Kevin C. K. Ma PhD
Marine Ecologist · Postdoc · He/him
Biodiversity Research Centre · University of British Columbia
About
Kevin is a marine ecologist and postdoc in the Harley Lab at the University of British Columbia. In one project, he is measuring how environmental stress, habitat complexity, and predation by the keystone sea star Pisaster ochraceus each contribute to intertidal biodiversity, and how their relative importance changes across spatial scales. In a separate project, he is using black- and white-bordered experimental tiles to test how warming reconfigures rocky-shore communities under different salinity regimes across the Salish Sea.
Positions
- 2025–presentPostdoctoral Research Fellow · University of British Columbia
- 2022–2024Postdoctoral Fellow · Memorial University of Newfoundland
- 2019–2022Postdoctoral Research Fellow · Rhodes University
Education
- 2020PhD in Oceanography · Université Laval
- 2012MSc in Biology · Memorial University of Newfoundland
- 2008BSc in Biology (Ecology & Environmental Biology) · University of British Columbia
- Attending the Sentinels of Change Fall Team Meeting (22–23 Oct 2026)
- Attending the Western Society of Naturalists 107th Annual Meeting (12–15 Nov 2026)
- Teaching BIOL 326: Experimental Biology of Invertebrates (Jan–Apr 2027)
- Attended the Data4Nature Workshop: Species identification through computer vision (13 Oct 2026)
- Attended the Data4Nature Workshop: How to get data into and out of species databases (22 Sep 2026)
- Joined the science delegation for the Green College Dal Grauer Memorial Lecture (17 Sep 2026)
- Completed the Postdoc Instructional Skills Workshop (18 & 25–26 Jul 2026)
- Presented at the Institute for the Oceans and Fisheries’ 10-Year Anniversary Symposium (5 May 2026)
- Attended The Ecology of Our Changing Shores: Symposium & Intertidal Exploration (18 Apr 2026)
- Attended the Sentinels of Change Spring Team Meeting (1–2 Apr 2026)
- Presented at the 2026 Ocean Sciences Meeting in Glasgow (22–27 Feb 2026)
- Presented at the Biodiversity Research Centre Symposium and Open House (17 Sep 2025)
Publications
27 peer-reviewed articles (20 as first author) · 10 other academic works287 citations · h-index of 11 (Google Scholar as of October 2026)
Peer-reviewed articles
- Ma KCK, MacLeod CD, Janusson C, Ho J-A, Lemay MA, Gehman A-LM, Harley CDG. 2026. Genetic evidence for the microphallid trematode Maritrema gratiosum in the Northeast Pacific and an overview of its global distribution. Journal of Helminthology 100: e79. https://doi.org/10.1017/S0022149X26101771
The trematode Maritrema gratiosum Nicoll, 1907 has a heteroxenous life cycle comprising a marine gastropod as its first intermediate host, a barnacle as its second intermediate host, and a bird as its definitive host. Globally, the species is widely distributed from subtropical waters of the South China Sea to arctic waters of the Barents Sea. In European waters (namely, western Europe and the Barents Sea), the complete life cycle of M. gratiosum is known. Elsewhere in its range, however, its life cycle remains incompletely understood. Clarifying its distribution and resolving unknown host associations are essential for advancing a more holistic view of host–parasite dynamics and their ecological role in intertidal ecosystems. In this study, M. gratiosum was detected using DNA-based assays in individuals of the barnacle Balanus glandula Darwin, 1854 that were collected from the rocky intertidal zone along the southern coast of British Columbia, Canada. This finding provides the first molecular evidence of this trematode species in the Pacific, complementing earlier records. The same molecular approach can be extended to identify region-specific hosts, such as the first intermediate (molluscan) host in the Pacific region, which remains unidentified.
- Received
- 3 Dec 2025
- Revised
- 3 Jun 2026
- Accepted
- 4 Jun 2026
- Published online
- 13 Jul 2026
- Pierrat J, Ma KCK, Hamel J-F, Mercier A. 2026. Spatial and size distributions of early recruits of Cucumaria frondosa in a coastal nursery (Nunavut, Canadian Arctic). Regional Studies in Marine Science 96: 104920. https://doi.org/10.1016/j.rsma.2026.104920
The discovery of nursery sites of the sea cucumber Cucumaria frondosa in the Canadian Arctic offers opportunities to gather knowledge on the ecology of juveniles. Here, their size and spatial distributions were examined and inter-individual and inter-specific relations were assessed. Out of 893 juveniles collected between 1 and 3 m depths in the fall, 95% were early recruits (<1-year-old). They chiefly occurred on rubbles (∼80%) representing the main substratum (∼44%) in the nursery. The length of early recruits across all depths was ∼1520 μm, with the smallest found at 3 m (∼1407 μm). Fewer recruits were identified in the following spring (51.5%), allowing the calculation of a growth rate (∼114 µm mo−1). Their density was consistently ∼7400 ind m−2 across depths. Juveniles were mostly found aggregated on flat surfaces (62.7%) or in shallow depressions (18.4%) on the underside of the stones, but also occurred on seaweed holdfasts (2.7%). The average nearest neighbour distance was ∼0.37 cm, with some juveniles touching each other. More individuals were observed with their body oriented in the same direction (45%) than in opposite directions (25%). Four sympatric species were identified on the same substratum; the polychaete Spirorbis spirorbis (49.7%), encrusting bryozoans in order Cheilostomatida (40.5%), the limpet Testudinalia testudinalis (6.9%), and calcareous encrusting algae (2.9%). Data on newly settled sea cucumbers in the wild are rare. The present findings provide essential information on the population dynamics and carrying capacity of C. frondosa in support of local subsistence harvests and emerging small-scale commercial fisheries led by the Inuit community.
- Received
- 7 Jan 2026
- Revised
- 26 Feb 2026
- Accepted
- 11 Mar 2026
- Published online
- 14 Mar 2026
- Publication date
- 1 Apr 2026
- Ma KCK, Gover LE, Hamel J-F, Mercier A. 2026. Optimizing the use of portable ROVs for community-based benthic surveys: A case study on the demographics of sea cucumbers around nursery habitats in the Arctic. Polar Science 47: 101287. https://doi.org/10.1016/j.polar.2025.101287
Nearshore areas around Qikiqtait in the Canadian Arctic have been identified as nursery habitats for the sea cucumber Cucumaria frondosa, which is locally consumed and being explored for small-scale commercial fisheries. This study characterized this species’ demographics along a depth gradient (∼0.5–11.5 m) at three sites inside and adjacent to nursery grounds using a mini-class remotely operated vehicle (ROV). A novel technique involving the superimposition of virtual quadrats was developed to minimize perspective biases for the analysis of images captured obliquely relative to the seafloor. Overall densities at Katak and Kataaluk were a magnitude lower than at Sanikiluaq, suggesting spatial variability in environmental conditions. Smaller individuals (∼5 cm) occurred mostly on rubble between 1 and 3 m at Sanikiluaq, larger ones (∼10 cm) on gravel at 2–7 m at Kataaluk, and a mix of both size classes occupied gravel, rubble, boulders, and bedrock between 3 and 11 m at Katak. Globally, body sizes tended to increase with depth, evoking cohorts of sea cucumbers undergoing step-wise downward migrations as they grew. This study provides foundational data on C. frondosa around its nursery habitats. It also enhances the usefulness of mini-class ROVs to investigate benthic assemblages in ice-covered areas through community-led initiatives.
- Received
- 15 Apr 2025
- Revised
- 24 Aug 2025
- Accepted
- 2 Oct 2025
- Published online
- 3 Oct 2025
- Publication date
- 1 Mar 2026
- Ma KCK, Hamel J-F, Mercier A. 2026. Proposed revision of ‘crystal cells’ as phagocytised metabolic by-products in holothuroid echinoderms. Journal of the Marine Biological Association of the United Kingdom 106: e9. https://doi.org/10.1017/S002531542510101X
Crystal cells in echinoderms have been described in the literature as a type of coelomocyte (immune cell) containing a crystalline structure. Their putative function has been widely ascribed to osmoregulation but this assertion was never robustly tested. In the present paper, a review of crystal cells and crystalline structures provides evidence supporting a different identity and function. First, the same microcrystals can be found either free or encapsulated by a cell membrane (with or without a structure resembling a nucleus). Specifically, they are typically non-encapsulated when found inside tissues of internal organs and encapsulated when free floating in the hydrovascular or perivisceral fluids. Although usually individually packaged, microcrystals were also observed encapsulated in groups of up to four, with or without other particles. Their morphological features, coupled with their chemical and optical properties, match that of microcrystals of uric acid, described in other phyla, including chordates. Two pathways of excretion of these crystallised by-products were evidenced: rejected with sea water out of the respiratory tree and expelled via transrectal coelomoducts among coelomocyte aggregates. Overall, the present synthesis strongly supports that ‘crystal cells’ historically described as a distinct type of coelomocyte in holothuroids are phagocytes that have engulfed uric acid microcrystals generated as waste by metabolic activities.
- Received
- 19 Jun 2025
- Revised
- 16 Oct 2025
- Accepted
- 20 Dec 2025
- Published online
- 20 Jan 2026
- Ma KCK, Gao F, Hamel J-F, Mercier A. 2025. Diversity and distribution of extracellular microcrystals in holothuroid echinoderms. Royal Society Open Science 12: 250514. https://doi.org/10.1098/rsos.250514
Biomineralization research in echinoderms has been focused on skeletal structures, which provide strength and protection. Other minerals, specifically extracellular microcrystals, are described here for the first time in echinoderms. Six morphotypes were isolated from a holothuroid and classified into three chemical compounds. Uric acid crystals were associated with fluids from the hydrovascular system, perivisceral coelom and respiratory tree, while calcium carbonate crystals were detected in the epithelium of the respiratory tree and calcium oxalate dihydrate crystals were found in tissues of the cloaca, integument, Polian vesicle and tentacle. Uric acid crystals were mostly non-encapsulated in tissues, whereas, in fluids, they were often encapsulated by phagocytes, alone or in groups, suggesting that they are waste products. Calcium carbonate crystals in the respiratory tree and calcium oxalate dihydrate crystals in the cloaca suggest that they are being expelled from the body. Insofar as calcium oxalate dihydrate crystals could be involved in calcium regulation, we speculate that they might be crystallized and retained in ossicle-associated integumentary tissues and tentacles, which are susceptible to damage and could use them as a calcium reserve to synthesize and repair ossicles. Observations of microcrystals in different holothuroid species examined suggest their ubiquity in the class Holothuroidea and more generally, deuterostomes.
- Received
- 26 Mar 2025
- Accepted
- 20 Aug 2025
- Published online
- 17 Sep 2025
- Pratt CJ, Trott TJ, Bernier RY, Boerder K, Goodwin C, Barrell J, Grégoire B, Rawlings TA, Cronmiller E, Ma KCK, Sargent PS, McBride MC, DiBacco C, Hiltz C, Kingsbury S. 2025. The overlooked introduction of the encrusting bryozoan Juxtacribrilina mutabilis to eastern Canada. Journal of the Marine Biological Association of the United Kingdom 105: e98. https://doi.org/10.1017/S0025315425100362
We report the introduction of Juxtacribrilina mutabilis, a nonindigenous marine encrusting bryozoan, to eastern Canada. Previously reported as a nonindigenous species (NIS) in Europe and Maine, USA, this species is of potential ecological concern due to its propensity to foul eelgrass (Zostera marina), an ecologically important habitat-forming coastal species. By compiling prior unpublished records, re-evaluating existing specimens, and collecting new records of J. mutabilis, we discovered that the species has a widespread distribution in eastern Canada. Specimen reclassification efforts in our study indicate that J. mutabilis has been present in eastern Canada since at least 2013, but the species largely escaped notice until 2024, likely due to its similarity to other encrusting bryozoan species and other factors inhibiting its detection. In light of the distributional and genetic data collected in this study, we reconstruct the possible invasion history of J. mutabilis in eastern Canada, including potential introduction mechanisms, timing, and source regions. We also discuss the ecology of J. mutabilis in eastern Canada, evaluating the factors influencing the morphology of the bryozoan, assessing its potential to detrimentally impact its eelgrass substrate, and estimating its environmental niche. Further research into the distribution, ecology, and potential impacts of J. mutabilis in eastern Canada is recommended. This case study highlights the importance of diversity in the habitats surveyed and methods used when monitoring for marine NIS, the need for horizon scanning to raise awareness of potential NIS, and the advantages of multi-party collaboration and citizen science for early detection of such species.
- Received
- 24 Feb 2025
- Revised
- 20 May 2025
- Accepted
- 12 Jun 2025
- Published online
- 11 Sep 2025
- Corbisier G, Ma KCK, Jobson SM, Hamel J-F, Caulier G, Mercier A. 2025. Morphological variations and dysmorphic features in the sea cucumber Cucumaria frondosa. Canadian Journal of Zoology 103: 1–13. https://doi.org/10.1139/cjz-2025-0008
Studying morphological abnormalities provides valuable insights into the developmental processes, species adaptability, gene expression, and the potential effect of environmental pressures. Dysmorphic features are well known within several taxa like arthropods but has much less been investigated in others like echinoderms, and specially sea cucumbers (Holothuroidea). The dendrochirotid Cucumaria frondosa (Gunnerus, 1767), which is the most studied and economically important holothuroid species in the North Atlantic, is known to present different colour morphotypes but anatomical variations have rarely been reported. This study tallied dysmorphic features across a sample of more than 900 individuals of C. frondosa examined over five years. About 1.3% and 15.9% of individuals presented non-standard external or internal anatomical characteristics, respectively. Individuals with unusual body plans, including two posterior ends and two cloaca/anuses, or an abnormal number of tentacles, were discovered. Others exhibited supernumerary organs, or organs of unusual shape and size, e.g., ramified/split ambulacra and longitudinal muscle bands, ramified or supernumerary Polian vesicles, hypertrophied madreporites, inter-vesicle protrusions, and hypertrophied circular haemal vessels. These features are described here for the first time in C. frondosa and have not been reported before in holothuroids. The severity of the morphological changes along with their possible drivers and impacts is discussed.
- Received
- 23 Jan 2025
- Accepted
- 31 Mar 2025
- Published online
- 28 Jun 2025
- Publication date
- 2 Oct 2025
- Ma KCK, Reddy S, Froneman PW, Porri F, McQuaid CD. 2025. Locality-based community science facilitates early detection and monitoring: The case of an extralimital population of a brachyuran crab. Management of Biological Invasions 16(2): 531–544. https://doi.org/10.3391/mbi.2025.16.2.12
Practitioners of community science who are based at a locality and who are familiar with the local ecosystem can provide opportunities to supplement formal monitoring efforts. Between 2021 and 2023, we established a working relationship with a year-round resident recreational fisher who was engaged with monitoring as a community scientist. As a result, the first extralimital record of Portunus segnis (commonly known as the blue swimming crab) in temperate waters of South Africa was detected in January of 2020 in the Kowie River on the south coast. Following this discovery, two additional specimens were found in the estuarine reaches of the same river in December 2021. This report provides evidence of a population of P. segnis persisting outside its native tropical range and, in addition to morphological identification, species verification was confirmed using genetic barcoding. The circumstances of finding these specimens underscore the importance of establishing and maintaining relationships between local resource users and researchers to facilitate the identification and monitoring of introduced and range expanding species and to provide formal scientific documentation and rapid communication of species occurrences and persistence outside their native range.
- Received
- 10 Nov 2024
- Accepted
- 7 Feb 2025
- Published online
- 16 Apr 2025
- Publication date
- 1 Jun 2025
- Zardi GI, Ma KCK, Froneman PW, Nicastro KR. 2025. First record of pyroplastic and partially burnt plastic litter along South African shores. Marine Pollution Bulletin 214: 117817. https://doi.org/10.1016/j.marpolbul.2025.117817
As plastic pollution has accumulated in the natural environment over the last half-century, so too has the body of literature on plastic contamination assessment. Despite this growing research, new, and cryptic forms of plastic debris continue to emerge, with limited data on their composition and abundance. Among these novel pollutants is a type of marine litter derived from the burning or melting of manufactured plastics. In this study, we report for the first time the presence of burned plastic forms at selected intertidal sandy habitats along the South African coast. We examined both pyroplastics—molten items with rock-like properties due to environmental weathering—and partially burned plastics, which retain features of the original manufactured objects. Surveys conducted across 22 sites spanning over 2000 km revealed this new type of litter at 19 locations, predominantly composed of polyethylene (37 items), polyethylene terephthalate (12 items), polypropylene (5 items) and polystyrene (3 items), with an average weight of 5.4 g per item. These findings highlight the widespread presence of burned plastics in coastal environments in South Africa and emphasize the need for further research into their ecological impacts.
- Received
- 29 Oct 2024
- Revised
- 4 Mar 2025
- Accepted
- 9 Mar 2025
- Published online
- 14 Mar 2025
- Publication date
- 1 May 2025
- Boonzaaier-Davids MK, Ma KCK, McQuaid CD. 2023. Epibiotic association of encrusting cheilostome bryozoans on shells of an invasive mussel from rocky shores of South Africa, with the description of a new aviculiferous species of Chaperia. Zootaxa 5258(2): 197–210. https://doi.org/10.11646/zootaxa.5258.2.2
Rocky shores typically exhibit a variety of sedentary and free-moving forms of epibionts associated with the shells of mussel basibionts. This paper provides a first report on epibiotic bryozoans found on shells of the invasive Mediterranean mussel, Mytilus galloprovincialis Lamarck. More than 2500 mussels were collected between December 2019 and October 2020 from rocky shores during low spring tides across the south–southeast coast of South Africa. Ten percent of these mussels hosted epibiotic bryozoans. We examined a subset of these epibiotised mussels to assess the diversity of bryozoans. Three encrusting cheilostome species were identified: Chaperia atypica n. sp., Celleporella hyalina (Linnaeus), and Hippomonavella sp. This new species is the first Chaperia with avicularia and the first South African species with ooecia. This study highlights the biological diversity of epibiotic bryozoans on mussel shells and, given their differences in microtopography, the possibility that invasive species can provide a new substratum for rare, overlooked or undescribed species of epibionts.
- Ma KCK, Monsinjon JR, Froneman PW, McQuaid CD. 2023. Thermal stress gradient causes increasingly negative effects towards the range limit of an invasive mussel. Science of The Total Environment 865: 161184. https://doi.org/10.1016/j.scitotenv.2022.161184
Environmental filtering (EF), the abiotic exclusion of species, can have first order, direct effects with cascading consequences for population dynamics, especially at range edges where abiotic conditions are suboptimal. Abiotic stress gradients associated with EF may also drive indirect second order effects, including exacerbating the effects of competitors, disease, and parasites on marginal populations because of suboptimal physiological performance. We predicted a cascade of first and second order EF-associated effects on marginal populations of the invasive mussel Mytilus galloprovincialis, plus a third order effect of EF of increased epibiont load due to second order shell degradation by endoliths. Mussel populations on rocky shores were surveyed across 850 km of the south–southeast coast of South Africa, from the species' warm-edge range limit to sites in the centre of their distribution, to quantify second order (endolithic shell degradation) and third order (number of barnacle epibionts) EF-associated effects as a function of along-shore distance from the range edge. Inshore temperature data were interpolated from the literature. Using in situ temperature logger data, we calculated the effective shore level for several sites by determining the duration of immersion and emersion. Summer and winter inshore water temperatures were linked to distance from the mussel's warm range edge (our proxy for an EF-associated stress gradient), suggesting that seasonality in temperature contributes to first order effects. The gradient in thermal stress clearly affected densities, but its influence on mussel size, shell degradation, and epibiosis was weaker. Relationships among mussel size, shell degradation, and epibiosis were more robust. Larger, older mussels had more degraded shells and more epibionts, with endolithic damage facilitating epibiosis. EF associated with a gradient in thermal stress directly limits the distribution, abundance, and size structure of mussel populations, with important indirect second and third order effects of parasitic disease and epibiont load, respectively.
- Received
- 5 Jul 2022
- Revised
- 16 Dec 2022
- Accepted
- 21 Dec 2022
- Published online
- 26 Dec 2022
- Publication date
- 20 Mar 2023
- Ma KCK, Pulfrich A, Froneman PW, McQuaid CD. 2023. Invasion of rocky shores by a mytilid mussel reveals an abundant-centre distribution coupled with moderate increases in densities at its absolute range limits. Austral Ecology 48(1): 197–214. https://doi.org/10.1111/aec.13260
Semimytilus patagonicus is an invasive mussel on the coast of southern Africa and has extended its range in recent years. We asked whether its distribution and abundance are consistent with the abundant-centre hypothesis (ACH). Marginal populations were located by monitoring 33 rocky shore sites in South Africa and southern Namibia in 2021. This revealed no changes to its distributional limits since 2020. At nine of these sites, population demography was measured to allow a comparison of their densities and size structure. Four were central populations on the west coast of South Africa (including the site where the species was first detected in 2009). Four were marginal populations in South Africa: two towards the cold range edge in the north and two towards the warm range edge to the south. The ninth population was in southern Namibia, representing a recent invasion event first detected in 2014. Across the species' South African range, the distribution of its abundance was generally consistent with the ACH, with the greatest abundance at its range centre and a gradual decrease towards the range edges. However, the ultimate marginal population at both its cold and warm range edges showed moderate upticks in abundance compared to the penultimate marginal populations. Additionally, marginal populations in South Africa typically included a greater proportion of large individuals. Recruitment intensity was greater in warm range edge populations than cold range edge populations. The size structure of the population in Namibia resembled those of central populations in South Africa. Moderate increases in densities at the absolute range limits suggest that the species is currently undergoing spread into regions associated with moderately optimal environmental conditions (ultimate range edge sites) after encountering regions associated with suboptimal environmental conditions (penultimate range edge sites).
- Received
- 25 Mar 2022
- Revised
- 7 Oct 2022
- Accepted
- 8 Nov 2022
- Published online
- 4 Dec 2022
- Publication date
- 1 Feb 2023
- Ma KCK, McKindsey CW, Johnson LE. 2022. Detecting rare species with passive sampling tools: Optimizing the duration and frequency of sampling for benthic taxa. Frontiers in Marine Science 9: 809327. https://doi.org/10.3389/fmars.2022.809327
The choice of the duration and frequency of sampling to detect relevant patterns in field experiments or for environmental monitoring is always challenging since time and material resources are limited. In practice, duration and frequency of sampling are often chosen based on logistical constraints, experience, or practices described in published works but are rarely justified and almost never optimized before initiating sampling. Settlement plates are commonly used as a passive sampling tool to study recruitment patterns of fouling organisms (including non-indigenous species) and their deployment is amenable to experimentation with respect to manipulating duration and frequency of sampling. This study aimed to determine the optimal sampling strategy to detect rare species (e.g., a non-indigenous species early in the invasion process when its population size is still small). To do so, we deployed a series of settlement plates of various durations (1–32 days) and sampling frequencies (daily to biweekly) during the seasonal onset of recruitment, when larval supply was low, a situation that mimics the low propagule pressure of the early stages of the invasion process. We demonstrated that a combination of longer sampling duration and higher sampling frequency was the best strategy to maximize taxonomic richness. However, we found that an intermediate sampling duration of 1–2 weeks was optimal for detecting most species. These results can guide species-specific and assemblage-level sampling strategies using settlement plates. Additionally, this study can serve as a practical template for optimizing sampling of other taxonomic groups that were not examined in the present study as well as for the use of other methods.
- Received
- 4 Nov 2021
- Accepted
- 4 Feb 2022
- Publication date
- 16 Mar 2022
- Ma KCK, McQuaid CD. 2021. Review of range extensions of tropical brachyuran crabs into temperate waters of southern Africa. Crustaceana 94(10): 1235–1262. https://doi.org/10.1163/15685403-bja10144
We compiled known occurrence records of seven species of crabs identified in the literature and one documented in this report as having undergone range extensions in southern Africa. Of these eight species, six (Austruca occidentalis, Neosarmatium africanum, Ocypode ceratophthalmus, Portunus segnis, Tubuca urvillei, and Varuna litterata) have extended their ranges either across a major biogeographic boundary that separates the subtropical and warm temperate ecoregions of this coast, or into estuaries that historically lack mangrove forests. For the seventh and eighth species, Charybdis smithii and Scylla serrata, we were unable to find any distributional data that supported poleward range extension. In addition, we contribute the first record of the blue swimming crab, P. segnis, from the temperate south coast of South Africa. This early detection is likely to be part of an ongoing regional trend of tropical-adapted brachyuran crab species extending their ranges into temperate ecoregions.
- Received
- 29 Apr 2021
- Accepted
- 16 Jun 2021
- Published online
- 27 Oct 2021
- Ma KCK, Redelinghuys S, Gusha MNC, Dyantyi SB, McQuaid CD, Porri F. 2021. Intertidal estimates of sea urchin abundance reveal congruence in spatial structure for a guild of consumers. Ecology and Evolution 11(17): 11930–11944. https://doi.org/10.1002/ece3.7958
We hypothesized congruence in the spatial structure of abundance data sampled across multiple scales for an ecological guild of consumers that exploit similar nutritional and habitat resources. We tested this hypothesis on the spatial organization of abundance of an herbivorous guild of sea urchins. We also examined whether the amount of local along-shore rocky habitat can explain the observed spatial patterns of abundance. Standardized estimates of abundance of four intertidal sea urchins—Diadema cf. savignyi, Echinometra mathaei, Parechinus angulosus, and Stomopneustes variolaris—were determined by six observers at 105 sites across 2,850 km of coast of South Africa. For each species and observer, wavelet analysis was used on abundance estimates, after controlling for potential biases, to examine their spatial structure. The relationship between local sea urchin abundance and the amount of upstream and downstream rocky habitat, as defined by the prevailing ocean current, was also investigated. All species exhibited robust structure at scales of 75–220 km, despite variability among observers. Less robust structure in the abundances of three species was detected at larger scales of 430–898 km. Abundance estimates of sympatric populations of two species (D. cf. savignyi and E. mathaei) were positively correlated with the amount of rocky habitat upstream of the site, suggesting that upstream populations act as larval sources across a wide range of scales. No relationship between abundance and habitat size was found for P. angulosus or S. variolaris. Within the range of scales examined, we found robust congruence in spatial structure in abundance at the lower, but not the larger, range of scales for all four species. The relationship between abundance and upstream habitat availability in two species suggests that larval supply from upstream populations was probably the mechanism linking habitat size and abundance.
- Received
- 13 Jan 2021
- Revised
- 22 Jun 2021
- Accepted
- 24 Jun 2021
- Published online
- 9 Aug 2021
- Ma KCK, Gusha MNC, Zardi GI, Nicastro KR, Monsinjon JR, McQuaid CD. 2021. Biogeographic drivers of distribution and abundance in an alien ecosystem engineer: Transboundary range expansion, barriers to spread, and spatial structure. Journal of Biogeography 48(8): 1941–1959. https://doi.org/10.1111/jbi.14124
Aim
Biogeographic boundaries can act as either weak or strong barriers to the spread of species undergoing distributional change. Once a novel species spreads across a boundary, it can have a substantial impact on the ecosystem, for instance by competing with local species, and, over the long-term, re-engineer the ecosystem. Marine biogeographic regions are clearly defined on the coast of southern Africa and we tested the influence of their boundaries on the spread and spatial structure of an alien ecosystem engineer.
Location
Southern Africa.
Taxon
An invasive mussel, Mytilus galloprovincialis.
Methods
Records of M. galloprovincialis were compiled into a database to determine its decadal patterns of spread across multiple bioregions. Distribution and abundance (estimated using density and semi-quantitative abundance scale [ACFOR]) of this mussel were surveyed to determine patterns in spatial structure across bioregions. In addition, we compared the size structure of populations at the eastern margins of its range with those of larger populations nearer the range centre.
Results
Initial breaching of biogeographic boundaries was associated with rapid spread, but other boundaries encountered decades later acted as barriers to further spread. Across >2,800 km of coast, spatial autocorrelation was observed in densities (low and mid shore levels) and in ACFOR abundances. Repeating spatial patterns in densities and ACFOR abundance were detected at scales of 120–160 km and of 400–990 km. Considerable effort was required to detect populations at the absolute eastern limits of its distribution.
Main conclusion
Detection of spatial structures at multiple scales suggests that ecologically determined processes regulate abundance at both intra-bioregional and inter-bioregional scales, which may help tease apart the historic and contemporary consequences of interspecific interactions on the structure of rocky shore communities. This study demonstrates the influence of biogeography in driving temporal patterns of spread and spatial structure on the distribution and abundance of an invasive species.
- Received
- 7 Jul 2020
- Accepted
- 16 Mar 2021
- Published online
- 4 May 2021
- Ma KCK, McQuaid CD, Pulfrich A, Robinson TB. 2020. Status of a decennial marine invasion by the bisexual mussel Semimytilus algosus (Gould, 1850) in South Africa. African Journal of Marine Science 42(4): 507–515. https://doi.org/10.2989/1814232X.2020.1820376
The invasion history and current distribution of the alien marine mussel, the bisexual mussel Semimytilus algosus, on rocky shores of South Africa is described in this study. The eastern edge of its distribution has been monitored since 2014, and the most-recent observations were made between January and March of 2020, at 16 sites between Hondeklipbaai on the west coast and Nature’s Valley on the south coast. From these 2020 records, the species ranged across approximately 840 km along the coast, from Hondeklipbaai to Hermanus. The species’ invasion history and distribution suggests that this mussel has persisted on the west coast over the past decade, and spread along the coast in both northward and south–southeastward directions. Since 2010, the species has spread predominantly in a southerly and then easterly direction, extending its range by ∼270 km into the Agulhas ecoregion. In contrast, its spread has been slower to the north, with a range extension of only ∼75 km. Long-term, routine monitoring of the coast to track the spread of S. algosus and other invasive marine species, and to identify new incursions, is recommended to support evidence-based management of biological invasions.
- Received
- 8 Apr 2020
- Revised
- 15 Jun 2020
- Accepted
- 18 Jun 2020
- Published online
- 16 Dec 2020
- Ma KCK, Zardi GI, McQuaid CD, Nicastro KR. 2020. Historical and contemporary range expansion of an invasive mussel, Semimytilus algosus, in Angola and Namibia despite data scarcity in an infrequently surveyed region. PLoS ONE 15(9): e0239167. https://doi.org/10.1371/journal.pone.0239167
Understanding the spread of invasive species in many regions is difficult because surveys are rare. Here, historical records of the invasive marine mussel, Semimytilus algosus, on the shores of Angola and Namibia are synthesised to re-construct its invasive history. Since this mussel was first discovered in Namibia about 90 years ago, it has spread throughout the western coast of southern Africa. By the late 1960s, the species was well established across a range of 1005 km of coastline in southern Angola and northern Namibia. Although only coarse spatial resolution data are available since the 1990s, the distribution of S. algosus clearly increased substantially over the subsequent decades. Today, the species is distributed over 2785 km of coastline, appearing in southern Namibia in 2014, whence it spread across the border to northern South Africa in 2017, and in northern Angola in 2015. Conspicuously, its current range appears to be relatively contiguous across at least 810 km of shore in southern Angola and throughout Namibia, with isolated, spatially disjunct occurrences towards the southern and northern limits of its distribution. Despite there being few occurrence records that are unevenly distributed spatially and temporally, data for the distributional patterns of S. algosus in Angola and Namibia provide invaluable insights into how marine invasive species spread in developing regions that are infrequently monitored.
- Received
- 1 Jul 2020
- Accepted
- 31 Aug 2020
- Publication date
- 11 Sep 2020
- Ma KCK, McKindsey CW, Johnson LE. 2020. Larval supply is a limited determinant of settlement at mesoscales across an anthropogenic seascape. Hydrobiologia 847: 4015–4029. https://doi.org/10.1007/s10750-020-04391-y
The relationship between larval supply and settlement is an integral part of the demographic processes of benthic marine organisms that determine their distribution at subsequent life stages. In ascidians, a strong positive relationship between larval supply and settlement has been previously documented, but only at small spatial scales (one location) and short time scales (less than one day). We investigated how this relationship might scale up by sampling larval abundance and settlement of a colonial ascidian (Botryllus schlosseri) across mesoscales (100s of m) of the anthropogenic seascape of a 1.5-ha marina. Settlement varied vertically with a linear decrease in settlement with increasing depth. This pattern corresponded to the vertical distribution of larvae in the morning, when they were most abundant. However, larval abundance explained only 26% of the variation in settlement at the meso-spatial scale (i.e. the combined effect of the horizontal and vertical dimensions). This weakening of the relationship between larval supply and settlement suggests that the two processes may become decoupled at larger spatial and temporal scales. Our study underscores how changing the scales of sampling may affect our understanding of larval dispersal and settlement processes.
- Received
- 11 Feb 2020
- Revised
- 9 Aug 2020
- Accepted
- 19 Aug 2020
- Published online
- 4 Sep 2020
- Ma KCK, Glon HE, Hawk HL, Chapman CN. 2020. Reconstructing the distribution of the non-native sea anemone, Diadumene lineata (Actiniaria), in the Canadian Maritimes: Local extinction in New Brunswick and no regional range expansion in Nova Scotia since its initial detection. Regional Studies in Marine Science 34: 101049. https://doi.org/10.1016/j.rsma.2020.101049
Since its first observations in New Brunswick (Sam Orr’s Pond) and Nova Scotia (Bedford Institute of Oceanography in Dartmouth) in 2009 and 2013, respectively, Diadumene lineata has been observed spreading to new locations in the Canadian Maritimes. In 2017 and 2018, regional surveys for non-native species did not detect D. lineata in New Brunswick, suggesting local extinction. Recent surveys also did not detect D. lineata in Prince Edward Island. However, between 2013 and 2018, D. lineata was detected in Nova Scotia (in chronological order) from Lunenburg Harbour (Lunenburg), Hermans Island (Lunenburg), Black Rock Beach (Halifax), Oak Island Marina (Chester), and Dartmouth Yacht Club (Dartmouth). These new observations combine to reconstruct the known recent distribution of this non-native sea anemone in the Canadian Maritimes. Further, after five years since its first detection in Nova Scotia, the regional distribution of D. lineata remained unchanged, restricted to a region of approximately 100 km between Halifax and Lunenburg. Although the primary focus is on D. lineata, additional records of the non-native macroalga, Codium fragile, from Sam Orr’s Pond and the native sea anemone, Metridium senile, fouling dock structures throughout the Canadian Maritimes are included in this report as M. senile commonly overlaps in habitat with D. lineata.
- Received
- 27 Sep 2019
- Revised
- 5 Dec 2019
- Accepted
- 5 Jan 2020
- Published online
- 7 Jan 2020
- Publication date
- 1 Feb 2020
- Carman MR, Colarusso PD, Neckles HA, Bologna P, Caines S, Davidson JDP, Evans NT, Fox SE, Grunden DW, Hoffman S, Ma KCK, Matheson K, McKenzie CH, Nelson EP, Plaisted H, Reddington E, Schott S, Wong MC. 2019. Biogeographical patterns of tunicates utilizing eelgrass as substrate in the western North Atlantic between 39º and 47º north latitude (New Jersey to Newfoundland). Management of Biological Invasions 10(4): 602–616. https://doi.org/10.3391/mbi.2019.10.4.02
Colonization of eelgrass (Zostera marina L.) by tunicates can lead to reduced plant growth and survival. Several of the tunicate species that are found on eelgrass in the northwest Atlantic are highly aggressive colonizers, and range expansions are predicted in association with climate-change induced increases in seawater temperature. In 2017, we surveyed tunicates within eelgrass meadows at 33 sites from New Jersey to Newfoundland. Eight tunicate species were identified colonizing eelgrass, of which four were non-native and one was cryptogenic. The most common species (Botrylloides violaceus and Botryllus schlosseri) occurred from New York to Atlantic Canada. Tunicate faunas attached to eelgrass were less diverse north of Cape Cod, Massachusetts. Artificial substrates in the vicinity of the eelgrass meadows generally supported more tunicate species than did the eelgrass, but fewer species co-occurred in northern sites than southern sites. The latitudinal gradient in tunicate diversity corresponded to gradients of summertime sea surface temperature and traditional biogeographical zones in the northwest Atlantic, where Cape Cod represents a transition between cold-water and warm-water invertebrate faunas. Tunicate density in the eelgrass meadows was low, ranging generally from 1–25% cover of eelgrass shoots, suggesting that space availability does not currently limit tunicate colonization of eelgrass. This survey, along with our 2013 survey, provide a baseline for identifying future changes in tunicate distribution and abundance in northwest Atlantic eelgrass meadows.
- Received
- 12 Jul 2019
- Accepted
- 9 Sep 2019
- Published online
- 30 Oct 2019
- Publication date
- 1 Dec 2019
- Ma KCK, Hawk HL, Goodwin C, Simard N. 2019. Morphological identification of two invading ascidians: New records of Ascidiella aspersa (Müller, 1776) from Nova Scotia and Diplosoma listerianum (Milne-Edwards, 1841) from New Brunswick and Quebec. BioInvasions Records 8(1): 50–64. https://doi.org/10.3391/bir.2019.8.1.06
We report new observations of two invasive ascidian species, the solitary Ascidiella aspersa and the colonial Diplosoma listerianum, from Eastern Canada, which include some records from new sites. Because these species share many superficial characteristics with native and non-native species in the region, identifications based on detailed taxonomic studies of internal structures—and not only on external features—are essential and can complement molecular methods. In this report, specimens of A. aspersa collected from Nova Scotia in 2013 and D. listerianum from New Brunswick and Quebec in 2017 were described morphologically to confirm species identity. Specimens of both were collected one year after initial discoveries in Nova Scotia and New Brunswick, respectively. Specimens of D. listerianum from Quebec were collected after a six-year hiatus. This report contributes a new record of A. aspersa 30 km (by sea) north of the site of the first record in Canada. It also confirms the first record of D. listerianum and documents its rapid spread in New Brunswick. This report is the first time that A. aspersa from Eastern Canada and D. listerianum from New Brunswick and the second time that D. listerianum from Quebec was explicitly identified based on an examination of internal features. Species confirmation of these easily overlooked or misidentified taxa contributes a time-stamp on current invasion fronts and suggests that the risk of further introductions and spread of these invasive species is present at un-invaded sites throughout Eastern Canada.
- Received
- 5 Jul 2018
- Accepted
- 9 Oct 2018
- Published online
- 6 Nov 2018
- Publication date
- 1 Mar 2019
- Ma KCK, Goodwin C, Cooper JA. 2018. Second record of Diplosoma listerianum (Milne-Edwards, 1841) five years after and 280 kilometres from the site of the first record in Nova Scotia. BioInvasions Records 7(2): 159–163. https://doi.org/10.3391/bir.2018.7.2.07
Five samples of Diplosoma listerianum, a non-indigenous colonial ascidian species complex, were collected via SCUBA between August 27 and September 28, 2017, from four sites in the coastal waters (depth ranging between 3.1 and 18.0 metres) around Brier Island, Nova Scotia, Canada. These samples constitute the second record of D. listerianum in Nova Scotia—five years after the first discovery and 280 kilometres (by sea) from the site of the first record. Semi-quantitative abundance of D. listerianum from Brier Island was determined and was found to be frequent or common in three of these four sites that were surveyed via SCUBA. The occurrence at several sites, coupled by the presence of eggs, ovaries, and larvae in some tissue samples suggest that there is presently an established population of D. listerianum off of Brier Island.
- Received
- 21 Nov 2017
- Accepted
- 31 Jan 2018
- Published online
- 25 Feb 2018
- Publication date
- 1 Jun 2018
- Ma KCK, Deibel D, Lowen JB, McKenzie CH. 2017. Spatio-temporal dynamics of ascidian larval recruitment and colony abundance in a non-indigenous Newfoundland population. Marine Ecology Progress Series 585: 99–112. https://doi.org/10.3354/meps12437
Spread of a non-indigenous ascidian (NIA), Botryllus schlosseri (Tunicata: Ascidiacea), has been detected since 2006 in coastal waters of Newfoundland. This species has been of economic concern because NIA can be a costly nuisance for bivalve aquaculture. The presence of this temperate-adapted species in Newfoundland represents an extension of its global range into subarctic waters. In 2010 and 2011, we investigated the population dynamics of B. schlosseri in Arnold’s Cove, Placentia Bay, Newfoundland and Labrador, Canada. Experiments testing the influence of season, depth, and substrate type on larval recruitment rates were conducted within the harbour over a period of 20 mo. Seasonal cycle of colony (adult) abundance was determined from video surveys of a belt transect of the wharf. The seasonal window of recruitment was from August to mid-October (ca. 2.5 mo), constrained to temperatures ≥13°C. Peak recruitment was observed coincident with maximum seasonal temperature in September. Recruitment was greatest at 1 m depth on PVC plates. Colonies were present year-round on wharf structures and exhibited seasonal fluctuations in percent cover, from <1% in May to ca. 3% in October. Seasonal increase in colony abundance was constrained to temperatures >5°C. These findings provide a population-level understanding of how a temperate-adapted, non-indigenous species is established and maintained in a subarctic environment. Our results suggest that 1 sampling site may adequately represent the spatial scale of ≤10s of metres within a marina, and NIA monitoring could target specific seasons, depths, and substrate types for optimal species detection.
- Received
- 16 Feb 2017
- Accepted
- 27 Nov 2017
- Publication date
- 27 Dec 2017
- Ma KCK, Deibel D, Law KKM, Aoki M, McKenzie CH, Palomares MLD. 2017. Richness and zoogeography of ascidians (Tunicata: Ascidiacea) in eastern Canada. Canadian Journal of Zoology 95(1): 51–59. https://doi.org/10.1139/cjz-2016-0087
Managers and policymakers in eastern Canada embrace science-based management of nonindigenous species and may benefit from having comprehensive regional species checklists at subnational jurisdictional levels. In this paper, regional checklists provide an account of the richness of ascidians in eastern Canada. Records of 58 ascidians resulted from reviewing 108 published sources, accessing data from two online databases, and collecting some common indigenous ascidian specimens. Analysis comparing the similarity of species among nine regions indicates that there is greater similarity in species composition between contiguous regions than between noncontiguous regions and suggests that there are four zoogeographic clusters in eastern Canada. Our checklists can inform managers and policymakers of the diversity of the ascidian taxa and can minimize taxonomic uncertainties of established nonindigenous and prospective invading species, for example, by identifying indigenous species that are congeners of nonindigenous species. The maintenance of checklists can be a valuable tool for the management of nonindigenous species as baselines to estimate changes in richness and to document the invasion status of nonindigenous species over time. For example, more importance can be placed on the spread of nonindigenous ascidians from one zoogeographic cluster to another than spread within the same cluster.
- Received
- 25 Apr 2016
- Accepted
- 24 Oct 2016
- Published online
- 30 Nov 2016
- Publication date
- 1 Jan 2017
- Ma KCK, Simard N, Stewart-Clark SE, Bernier RY, Nadeau M, Willis J. 2016. Early detection of the non-indigenous colonial ascidian Diplosoma listerianum in eastern Canada and its implications for monitoring. Management of Biological Invasions 7(4): 365–374. https://doi.org/10.3391/mbi.2016.7.4.06
In eastern Canada, the initial suspected discovery of the non-indigenous colonial ascidian Diplosoma listerianum in Quebec was followed by species identification and increased awareness for its detection in the neighbouring provinces of Nova Scotia and Prince Edward Island. A phylogenetic analysis was conducted based on sequences generated from the 18S ribosomal DNA gene isolated from tissues of two Canadian samples (Quebec and Nova Scotia) and samples from several species belonging to the Diplosoma genus, which confirmed the species identity of the eastern Canadian specimens. Colonies of D. listerianum found in Quebec (2008) and Nova Scotia (2012) are currently the only tissue records of this species in eastern Canada. Water samples of concentrated plankton collected in Quebec (2010 and 2011) and in Prince Edward Island (2011) tested PCR positive for D. listerianum DNA, but colonies were not observed concurrently. As a case study for early detection, this paper documents how D. listerianum was detected in eastern Canada by different groups (government monitoring, academic research) and with different methods (dive surveys, genetic analysis of water samples, collector plates). This case study suggests that the co-operation between groups and the breadth of the methods used contributed to the early detection of this species in three eastern Canadian provinces. In particular, we show that (i) partnerships between government, academia, and industry, (ii) a national capacity for species-specific molecular detection tools, and (iii) the recognition that the effectiveness and limitations of different monitoring methods may be site-specific can have positive early detection and monitoring outcomes.
- Received
- 31 Mar 2016
- Accepted
- 1 Jul 2016
- Published online
- 16 Aug 2016
- Publication date
- 1 Nov 2016
- Moore AM, Vercaemer B, DiBacco C, Sephton D, Ma KCK. 2014. Invading Nova Scotia: First records of Didemnum vexillum Kott, 2002 and four more non-indigenous invertebrates in 2012 and 2013. BioInvasions Records 3(4): 225–234. https://doi.org/10.3391/bir.2014.3.4.03
Research and monitoring efforts led to the discovery of four new non-indigenous tunicates and one new non-indigenous anemone in Nova Scotia in 2012 and 2013. In this report, we summarize and interpret the circumstances leading up to and actions taken following the first Nova Scotian records of the high impact invasive tunicate Didemnum vexillum Kott, 2002 as well as the tunicates Styela clava Herdman, 1881, Ascidiella aspersa (Müller, 1776), and Diplosoma listerianum (Milne-Edwards, 1841) and the anemone Diadumene lineata (Verrill, 1869). While dockside research and monitoring were responsible for detections of four species, the possibility that Didemnum vexillum was present was first reported by a member of the public, through Fisheries and Oceans Canada’s Aquatic Invasive Species Monitoring program.
- Received
- 3 Jul 2014
- Accepted
- 12 Sep 2014
- Published online
- 9 Oct 2014
- Publication date
- 1 Nov 2014
Other academic works
- Ma KCK, Pierrat J, Hamel J-F, Mercier A. 2025. Unexpected biotic substrata utilised by newly-settled recruits of the sea cucumber Cucumaria frondosa in their nursery habitat. SPC Beche-de-mer Information Bulletin 45: 59–62.·pdf
Recently, the occurrence of newly settled recruits and early juveniles of the sea cucumber Cucumaria frondosa was described in shallow waters (depth <2.5 m) of Qikiqtait, Nunavut (northern Canada) on shells of live and dead mussels, and on the bare surfaces of stones, forming a nursery habitat. It was assumed that most young individuals (i.e. <2 y) occurred on these substrata. However, since the initial publication by Hamel et al. (2023), new biotic substrata have been identified to host newly recruited juveniles in their nursery habitat, including the holdfast and blade of seaweeds, sea urchin spines, encrusting bryozoans, barnacles, coralline algae, and bivalves other than mussels, suggesting that the recruitment of C. frondosa may be more complex and opportunistic than originally suspected. As C. frondosa is currently the most heavily fished sea cucumber in the world, with fishing initiatives emerging in the Arctic, knowledge of where its recruits and juveniles are distributed is of major importance to protecting this potentially vulnerable resource.
- Pierrat J, Tucker A, Ma KCK, Hamel J-F, Mercier A. 2025. Association between a marine halacarid mite (Halacaroidea: Arthropoda) and early juveniles of the northern sea cucumber Cucumaria frondosa in Nunavut. SPC Beche-de-mer Information Bulletin 45: 56–58.·pdf
Juvenile and adult sea cucumbers are integral to marine food webs across the globe. The northern species Cucumaria frondosa is part of the diet of sea stars, crabs, fishes, birds and mammals, including seals and walruses, across its wide geographic distribution in the North Atlantic and Arctic Oceans. However, the trophic ecology of early juveniles is far less understood. In Qikiqtait (southern Nunavut, northern Canada), a nursery comprising newly settled and early juveniles <1 year of age (<1 mm in length) was recently identified. One juvenile sampled from this nursery was fortuitously discovered to host a transparent halacarid mite (~150 µm in length). The colour of the mite’s digestive tract mirrored the colour of the sea cucumber’s tissues, which are rich in red pigmented cells. Accordingly, the mite was cryptic, almost invisible when seen from above, and was presumed to feed on the tissues of juveniles. This represents the first observation of a direct interaction between juvenile sea cucumbers and a mite, providing novel insight on halacarid–echinoderm associations and adding an element to our understanding of northern sea cucumber populations.
- Scott MMF, Ma KCK, Wolvin S, Hamel J-F, Mercier A. 2024. First report of skin ulceration disease from temperate waters of the Northwest Atlantic: The case of the sea cucumber Cucumaria frondosa. SPC Beche-de-mer Information Bulletin 44: 22–26.·pdf
Approximately 60–70 adult individuals of the dendrochirotid sea cucumber Cucumaria frondosa – collected in waters off the coast of insular Newfoundland in eastern Canada – presented injuries consistent with skin ulceration disease (SKUD). An examination of 31 individuals that were suspected to be diseased revealed some cases of white-coloured lesions or ulcerations on the body wall, evisceration of internal organs, liquefaction of the dermis, and loss of podia attachment strength. Another 11 diseased individuals were quarantined and, eventually, exhibited liquefaction of the entire body and died. To our knowledge, this is the first time a condition consistent with SKUD has been reported in temperate–subpolar waters of the Northwest Atlantic and, the first time in C. frondosa, which is a commercially valuable species.
- Mercier A, Penney HD, Ma KCK, Lovatelli A, Hamel J-F. 2023. A guide to northern sea cucumbers: The biology and management of Cucumaria frondosa. FAO Fisheries and Aquaculture Technical Paper No. 700, pp. xvii + 92. https://doi.org/10.4060/cc7928en
This document synthesising knowledge on the northern sea cucumber Cucumaria frondosa was prepared for all stakeholders, including industry participants, government scientists, policymakers, and academic researchers. Its aim is to highlight the uniqueness of this marine resource to guide the industry forward and to emphasize areas that deserve further investigation. Available data from eastern and northern Canada, eastern United States of America, Greenland, northern Europe and the Russian Federation are presented. Topics covered include the taxonomy, distribution, biology, and ecology of the species, the natural threats it faces, the current harvesting, processing and marketing practices, and the prospects for aquaculture development. Relying on a knowledge base gathered over more than 40 years, this contribution compares C. frondosa with other common commercial species of sea cucumbers to tease out the major aspects that set it apart. A final segment provides a number of key recommendations for its management and conservation.
- Ma KCK, Trenholm R, Hamel J-F, Mercier A. 2023. The enigma of stones found in the body cavities of sea cucumbers. SPC Beche-de-mer Information Bulletin 43: 32–38.·pdf
For the first time, industrial processors of the suspension-feeding sea cucumber Cucumaria frondosa (Holothuroidea: Dendrochirotida) have reported two individuals with pebbles or stones nestled inside their body cavities. The two sea cucumbers were harvested by bottom trawl off the coast of Newfoundland (eastern Canada) and later analysed. They measured 11.5 cm and 14.0 cm in length, respectively, and harboured stones weighing up 450 g (i.e. three to four times their whole wet weight). These individuals displayed a severely damaged or crushed aquapharyngeal bulb, open wounds through the integument, and other deformations. The absence of, or damage to, internal organs and the erosion of the podia rows pointed to severe trauma, rather than deliberate ingestion (i.e. gastrolith), as the cause of the phenomenon. Violent impact of metal gear components with stones present on the seafloor or in the trawl itself may forcibly push these stones into the sea cucumbers during harvesting. A concrete outcome is potential damage to industrial equipment used for processing these stone-bearing sea cucumbers. As the fishery intensifies, it is anticipated that harvested sea cucumbers harbouring stones may increase in frequency, raising questions around this harvesting method, and calling for ways to detect the presence of internal stones before processing.
- Samy SS, Froneman PW, McQuaid CD, Ma KCK. 2022. A review of decapod biological invasions of polar waters. Biological Science: A Periodical of the Research of the Zoology & Entomology Honours Students 1(1): 69–74.·pdf
Over recent decades, polar waters have experienced an unprecedented amount of anthropogenic activity due to climate change melting sea-ice and creating new pathways through previously inaccessible waters. As anthropogenic activity increased in these regions, shipping has become more frequent and thus the movement of organisms through ballast water and hull fouling has also increased. As such, polar waters have become particularly susceptible to bio-invasions. Notably, decapod bio-invasions in both the Arctic and the Antarctic have been rising due to increased transoceanic movement through polar waters as well as the overall warming of polar waters. This is particularly interesting as decapods face a range of biogeographical and physiological barriers (such as below freezing temperatures and high magnesium [Mg2+] concentrations) that limits successful introductions, establishment, and geographic spread. Available literature suggests that as climate change drives disproportionate warming of polar waters, geographic and physiological barriers are being broken down both directly and indirectly via anthropogenic activity thus driving an increase in observed decapod invasions. This review assessed decapod bio-invasions in both the Arctic and the Antarctic with regard to key vectors of invasion, and physiological determinants to create an overview of decapod invasions in polar waters as whole as well as to create a preliminary list of invasive decapod species in polar waters.
- Ma KCK. 2020. Rare species detection and benthic recruitment across multiple scales of space and time with implications for early detection of marine invasive species. PhD thesis, Université Laval, pp. xxiv + 238. https://hdl.handle.net/20.500.11794/38152
As a consequence of anthropogenic activities, biological invasions have become a global problem that can cause ecological (e.g., biodiversity and habitat), economic (industries), and social (human wellbeing) harm. Prevention and early detection of new invasions are vital components of managing risks and impacts to ecosystems and economies. Prevention is, of course, preferred but early detection is a critical step that can ultimately stop future spread of invasive species because it provides an opportunity for eradication before population growth and spread. Despite being a cost- and time-effective management option, early detection requires considerably high sampling effort to detect incipient invasive populations at the early stages of their invasion.
Using the marine benthic system as a model, four inter-related studies were carried out to identify sampling strategies that could enhance our ability to detect rare invasive populations and to understand ecological patterns and processes of benthic recruitment across multiple scales of space and time. Specifically, these experimental field studies aimed to (1) evaluate the relationship between propagule supply and settlement in a closed invasive population, (2) determine the optimal sampling duration and frequency using settlement plates to detect rare species, (3) ascertain the relative importance of spatial and temporal sources of variation in benthic recruitment, and (4) examine how the spatial scale of sampling affects species detection by analyzing recruitment patterns at multiple scales across four orders of magnitudes ranging from tens of metres to tens of kilometres.
First study: Contrary to the expectation of a strong relationship between supply and initial settlement, larval supply was instead a limited determinant of settlement at mesoscales. This finding suggests that the strength of this relationship weakens as the spatial scale increased from previously reported small-scale field observations to mesoscales of the present study. Nonetheless, a quarter of the variation in settlement can still be explained by supply over short timescales (one week). Therefore, this relationship supports the utility of settlement plates as an effective tool for early detection at mesoscales within a marina because low densities of recruitment on plates correspond to low abundances of invasive propagules in the water column.
Second study: Intermediate sampling timescales of one to two weeks (duration treatments ranging from one day to one month) was the optimal plate deployment duration for “rare” species detection (i.e., during the seasonal onset of recruitment). An assemblage-level analysis, however, showed that increasing the duration and frequency of sampling logarithmically increased the total number of rare species observed. These species-by-species and assemblage-level findings demonstrate that modifying temporal aspects of sampling, such as duration and frequency, can substantially affect species detection.
Third study: The seasonal timing of plate deployment was determined to be the greatest source of variability in benthic recruitment of rare species after evaluating several spatial and temporal sources (i.e., site, region, season, and year). In particular, the optimal seasonal timing for early detection may be in the autumn (a) when the seasonal recruitment of established invasive species tends to peak and (b) when the site-level detection of rare invasive species tends to occur.
Fourth study: The dominant scale in rare species recruitment is at the smallest spatial scale (hundreds of metres). This dominant scale can be interpreted as being the correct spatial scale for rare species detection. Further analysis showed that if sampling was structured randomly, then forcing sampling at intermediate scales (thousands of metres) is the optimal scale for rare species detection. These results elucidate differences in the natural variability in benthic recruitment across multiple scales of space and time for both rare and common species.
These ecological studies are part of an early detection toolkit that can inform marine invasive species management with respect to how sampling for rare species should proceed across multiple spatiotemporal scales. Similar field experiments optimizing for rare species detection (beyond the use of settlement plates to detect benthic organisms in the Canadian Maritimes) should be done for other taxa, regions, and sampling tools—especially for forecasted high-risk invaders, regions susceptible to future invasions, and newly-developed tools.
- Deibel D, McKenzie CH, Rise ML, Thompson RJ, Lowen JB, Ma KCK, Applin G, O’Donnell R, Wells T, Hall JR, Sargent P, Pilgrim BB. 2014. Recommendations for eradication and control of non-indigenous, colonial, ascidian tunicates in Newfoundland harbours. Canadian Manuscript Report of Fisheries and Aquatic Sciences 3039, pp. xi + 60.·pdf
Two non-indigenous, colonial, ascidian species, Botryllus schlosseri and Botrylloides violaceus, were discovered along the south coast of Newfoundland in 2006–2007. B. schlosseri was found in several harbours, while B. violaceus has been found in one harbour thus far. These species have been reported in high, invasive abundances in many parts of the world, including other locations in Canada. They can have severe impacts on the marine environment, including displacing native benthic species, and threatening the economic sustainability of bivalve aquaculture farms. In this manuscript, we review the biology of these two species, their genetics and population ecology, and make recommendations for their eradication and control in Newfoundland harbours. This report is based on four years of research we have done on these non-indigenous ascidians in Belleoram and Arnold’s Cove, Newfoundland.
- Ma KCK. 2012. Population dynamics of a non-indigenous colonial ascidian tunicate in a subarctic harbour. MSc thesis, Memorial University of Newfoundland, pp. xxii + 211. https://hdl.handle.net/20.500.14783/4212
Botryllus schlosseri (Subphylum Tunicata: Class Ascidiacea) is a nonindigenous ascidian species of global and national interest, which has extensive populations along the south coast of insular Newfoundland. Economically, this species has been of concern to industry, management, and policymakers because non-indigenous ascidian species have been a severe and costly nuisance for bivalve aquaculture. Ecologically, the presence of this temperate-adapted species in Newfoundland represents an expansion of its global range into subarctic waters. Thus, I aimed to describe the population dynamics of B. schlosseri in Arnold's Cove, Placentia Bay, Newfoundland and Labrador, Canada, by determining the temporal and spatial patterns of recruitment and the seasonal cycle of colony abundance. In addition, I aimed to compile a checklist of extant indigenous and non-indigenous ascidian species of eastern Canada with an emphasis on species from Newfoundland and Labrador.
Artificial plates were used to determine recruitment rates among three sites, depths (1.0, 2.5, and 4.0 m from the water surface), and substrate types (aluminum, PVC, and wood in 2010; only PVC in 2011), in Arnold's Cove. Concurrently, density and cover of colonies were determined from the analysis of high-definition video surveys of a belt transect of wharf pilings. Seasonal biomass production was estimated from carbon to nitrogen (C:N) ratios and dry weight per unit area of dissected tissue subsamples.
The seasonal window for recruitment was from early August to mid-October. Recruitment rates were greater near the water surface than at other depths, and on PVC in comparison to aluminum and wood substrates. Maximum recruitment rates on PVC at 1.0 m were 29.3 and 43.5 m⁻²d⁻¹ in September of 2010 and 2011, respectively, coincident with maximum seasonal seawater temperatures of 16–17°C. Colonies were present year-round on pilings. In the upper subtidal zone, monthly mean cover ranged from an annual minimum of 0.6% in May to a maximum of 2.8% in October. Colony size and biomass, though not C:N ratios, had a significant seasonal signal.
These findings suggest that recruitment was predominantly constrained by seawater temperature within the short productive season, and that the population was sustained from one year to the next because of high cover of overwintering colonies. The efficacy of utilising PVC to track recruitment of Botryllus schlosseri, and perhaps other closely related ascidian species is supported by my data. Future management of B. schlosseri should target mitigation efforts before the annual onset of sexual reproduction and recruitment in July and within the upper 3–4 m of the water column.
- Ma KCK, Deibel D, McKenzie C. 2011. Indigenous and non-indigenous ascidian tunicates of Newfoundland and Labrador. Proceedings of the Contributed Papers of the 27th Annual General Meeting of the Aquaculture Association of Canada, Aquaculture Association of Canada Special Publication No. 17: 58–63.·pdf
Ascidian tunicates (sea squirts) can be aggressive invaders that grow over shellfish (e.g., mussels) and consequently out-compete them for space, and perhaps for food. The recent discovery of non-indigenous ascidians in Newfoundland and Labrador warrants the compilation of a comprehensive checklist of ascidian species to provide insight into the diversity of local ascidians and a basis for future comparisons with neighbouring marine environments. We have conducted a thorough literature review, search of online databases, and our own field collections to assemble the first comprehensive checklist of ascidian species for insular Newfoundland and mainland Labrador. A total of 38 ascidian species have been reported from the cold ocean waters of Newfoundland and Labrador since 1860. Among them are two non-indigenous, colonial ascidians, Botrylloides violaceus (Oka, 1927) and Botryllus schlosseri (Pallas, 1766), which have had an impact on aquaculture sustainability in Atlantic Canada. Our field collections are the first reports of these invasive, encrusting, marine invertebrates to have survived the winter as established resident populations on Newfoundland’s south coast.
Datasets
- Canadian BioGenome Project. 2024. Solaster endeca genome assembly. Principal haplotype (GCA_041228555.1), alternate haplotype (GCA_041228535.1). GenBank, National Center for Biotechnology Information. Specimens provided by Ma KCK, Hamel J-F, and Mercier A.
- Canadian BioGenome Project. 2024. Echinarachnius parma genome assembly. Principal haplotype (GCA_037951105.1), alternate haplotype (GCA_037951085.1). GenBank, National Center for Biotechnology Information. Specimens provided by Ma KCK, Hamel J-F, and Mercier A.
- Canadian BioGenome Project. 2024. Hippasteria phrygiana genome assembly. Principal haplotype (GCA_037893225.1), alternate haplotype (GCA_037893065.1). GenBank, National Center for Biotechnology Information. Specimens provided by Ma KCK, Hamel J-F, and Mercier A.
- Canadian BioGenome Project. 2024. Crossaster papposus genome assembly. Principal haplotype (GCA_037893245.1), alternate haplotype (GCA_037893195.1). GenBank, National Center for Biotechnology Information. Specimens provided by Ma KCK, Hamel J-F, and Mercier A.
- Canadian BioGenome Project. 2024. Henricia sp. genome assembly. Principal haplotype (GCA_037783545.1). GenBank, National Center for Biotechnology Information. Specimens provided by Ma KCK, Hamel J-F, and Mercier A.
- Canadian BioGenome Project. 2024. Leptasterias polaris genome assembly. Principal haplotype (GCA_037783415.1), alternate haplotype (GCA_037783435.1). GenBank, National Center for Biotechnology Information. Specimens provided by Ma KCK, Hamel J-F, and Mercier A.
- Canadian BioGenome Project. 2024. Strongylocentrotus droebachiensis genome assembly. Principal haplotype (GCA_035222895.1). GenBank, National Center for Biotechnology Information. Specimens provided by Ma KCK, Hamel J-F, and Mercier A.
- Ma KCK, Reddy S, Porri F. 2023. Portunus segnis cytochrome c oxidase subunit I (COX1) gene, partial cds. Specimen vouchers SB9176 (OR540310) and SB9487 (OR540311). GenBank, National Center for Biotechnology Information.
- Ma KCK, Monsinjon JR, Froneman PW, McQuaid CD. 2022. Determination of mean effective shore level to delineate periods of emersion and immersion for intertidal rocky shores. Dryad Digital Repository. https://doi.org/10.5061/dryad.h70rxwdmn
- Ma KCK, Redelinghuys S, Gusha MNC, Dyantyi S, McQuaid CD, Porri F. 2021. Distribution and abundance of intertidal sea urchins in South Africa. Dryad Digital Repository. https://doi.org/10.5061/dryad.mkkwh7110
- Ma KCK, Gusha MNC, Zardi GI, Nicastro KR, Monsinjon JR, McQuaid CD. 2021. Historical and contemporary records of Mytilus galloprovincialis in southern Africa. Dryad Digital Repository. https://doi.org/10.5061/dryad.crjdfn33n
- Ma KCK, McKindsey CW, Johnson LE. 2020. Larval abundance and recruitment densities of a non-native colonial ascidian in a marina in Nova Scotia, Canada. Zenodo. https://doi.org/10.5281/zenodo.4010641
Students
Kevin will be co-teaching BIOL 326: Experimental Biology of Invertebrates with Carl K. H. Ng at the University of British Columbia in Winter Term 2 (January–April 2027). The course explores invertebrate ecology, from physiology and behaviour to communities, through field surveys and lab experiments. Students curious about marine invertebrates are warmly encouraged to enrol.
Co-supervised honours students
Nalan E. GOOSEN — Multi-scale spatial patterns of biodiversity in intertidal cobble fields
Lauren E. GOVER — Sea cucumbers in the Canadian ArcticMa KCK, Gover LE*, Hamel J-F, Mercier A. 2026. Optimizing the use of portable ROVs for community-based benthic surveys: A case study on the demographics of sea cucumbers around nursery habitats in the Arctic. Polar Science 47: 101287. https://doi.org/10.1016/j.polar.2025.101287
Nearshore areas around Qikiqtait in the Canadian Arctic have been identified as nursery habitats for the sea cucumber Cucumaria frondosa, which is locally consumed and being explored for small-scale commercial fisheries. This study characterized this species’ demographics along a depth gradient (∼0.5–11.5 m) at three sites inside and adjacent to nursery grounds using a mini-class remotely operated vehicle (ROV). A novel technique involving the superimposition of virtual quadrats was developed to minimize perspective biases for the analysis of images captured obliquely relative to the seafloor. Overall densities at Katak and Kataaluk were a magnitude lower than at Sanikiluaq, suggesting spatial variability in environmental conditions. Smaller individuals (∼5 cm) occurred mostly on rubble between 1 and 3 m at Sanikiluaq, larger ones (∼10 cm) on gravel at 2–7 m at Kataaluk, and a mix of both size classes occupied gravel, rubble, boulders, and bedrock between 3 and 11 m at Katak. Globally, body sizes tended to increase with depth, evoking cohorts of sea cucumbers undergoing step-wise downward migrations as they grew. This study provides foundational data on C. frondosa around its nursery habitats. It also enhances the usefulness of mini-class ROVs to investigate benthic assemblages in ice-covered areas through community-led initiatives.
- Received
- 15 Apr 2025
- Revised
- 24 Aug 2025
- Accepted
- 2 Oct 2025
- Published online
- 3 Oct 2025
- Publication date
- 1 Mar 2026
Sheyenne Samantha SAMY — Review of decapod invasions of polar watersSamy SS*, Froneman PW, McQuaid CD, Ma KCK. 2022. A review of decapod biological invasions of polar waters. Biological Science: A Periodical of the Research of the Zoology & Entomology Honours Students 1(1): 69–74.
Over recent decades, polar waters have experienced an unprecedented amount of anthropogenic activity due to climate change melting sea-ice and creating new pathways through previously inaccessible waters. As anthropogenic activity increased in these regions, shipping has become more frequent and thus the movement of organisms through ballast water and hull fouling has also increased. As such, polar waters have become particularly susceptible to bio-invasions. Notably, decapod bio-invasions in both the Arctic and the Antarctic have been rising due to increased transoceanic movement through polar waters as well as the overall warming of polar waters. This is particularly interesting as decapods face a range of biogeographical and physiological barriers (such as below freezing temperatures and high magnesium [Mg2+] concentrations) that limits successful introductions, establishment, and geographic spread. Available literature suggests that as climate change drives disproportionate warming of polar waters, geographic and physiological barriers are being broken down both directly and indirectly via anthropogenic activity thus driving an increase in observed decapod invasions. This review assessed decapod bio-invasions in both the Arctic and the Antarctic with regard to key vectors of invasion, and physiological determinants to create an overview of decapod invasions in polar waters as whole as well as to create a preliminary list of invasive decapod species in polar waters.
Emma Lee GOODES — Endolithic infestation and barnacle epibionts on mussel shells
Alicea LUBBÉ — Review of interference and exploitative competition in marine systems
Current students
Maja WIND — Re-evaluating the space-for-time substitution method
Cole A. IRELAND — Distribution of the non-native periwinkle in British Columbia
Peach TRIPPELL — Sea cucumbers in British Columbia
Cassidy Yuen Chi LEE — Biodiversity of intertidal rocky shores in the Canary Islands
Joanne Jiou-An HO — Prevalence of trematode parasites in a population of barnaclesMa KCK, MacLeod CD, Janusson C, Ho J-A*, Lemay MA, Gehman A-LM, Harley CDG. 2026. Genetic evidence for the microphallid trematode Maritrema gratiosum in the Northeast Pacific and an overview of its global distribution. Journal of Helminthology 100: e79. https://doi.org/10.1017/S0022149X26101771
The trematode Maritrema gratiosum Nicoll, 1907 has a heteroxenous life cycle comprising a marine gastropod as its first intermediate host, a barnacle as its second intermediate host, and a bird as its definitive host. Globally, the species is widely distributed from subtropical waters of the South China Sea to arctic waters of the Barents Sea. In European waters (namely, western Europe and the Barents Sea), the complete life cycle of M. gratiosum is known. Elsewhere in its range, however, its life cycle remains incompletely understood. Clarifying its distribution and resolving unknown host associations are essential for advancing a more holistic view of host–parasite dynamics and their ecological role in intertidal ecosystems. In this study, M. gratiosum was detected using DNA-based assays in individuals of the barnacle Balanus glandula Darwin, 1854 that were collected from the rocky intertidal zone along the southern coast of British Columbia, Canada. This finding provides the first molecular evidence of this trematode species in the Pacific, complementing earlier records. The same molecular approach can be extended to identify region-specific hosts, such as the first intermediate (molluscan) host in the Pacific region, which remains unidentified.
- Received
- 3 Dec 2025
- Revised
- 3 Jun 2026
- Accepted
- 4 Jun 2026
- Published online
- 13 Jul 2026
Monica LIN — Physiological response of barnacles under low pH conditions
Lisa ZHANG — Persistence of intertidal barnacles on friable sandstone
Past students
Sofina M. JOHNSON — Analysis of intertidal biodiversity data
Libby LEE — Spectral properties of mussel shells
Nehal BHUSHAN — Review of biological zonations of intertidal rocky shores
Ada BREKER — Distribution of the non-native periwinkle in British Columbia
Kaitlyn LIU — Behavioural response of littorinids to a heated substratum
Megan Marie Frances SCOTT — Skin ulceration disease in a cold-water species of sea cucumberScott MMF*, Ma KCK, Wolvin S, Hamel J-F, Mercier A. 2024. First report of skin ulceration disease from temperate waters of the Northwest Atlantic: The case of the sea cucumber Cucumaria frondosa. SPC Beche-de-mer Information Bulletin 44: 22–26.
Approximately 60–70 adult individuals of the dendrochirotid sea cucumber Cucumaria frondosa – collected in waters off the coast of insular Newfoundland in eastern Canada – presented injuries consistent with skin ulceration disease (SKUD). An examination of 31 individuals that were suspected to be diseased revealed some cases of white-coloured lesions or ulcerations on the body wall, evisceration of internal organs, liquefaction of the dermis, and loss of podia attachment strength. Another 11 diseased individuals were quarantined and, eventually, exhibited liquefaction of the entire body and died. To our knowledge, this is the first time a condition consistent with SKUD has been reported in temperate–subpolar waters of the Northwest Atlantic and, the first time in C. frondosa, which is a commercially valuable species.
Contact
Department of Zoology, University of British Columbia
Biodiversity Research Centre, 2212 Main Mall
Vancouver, British Columbia V6T 1Z4, Canada
Emails: kevin.ma@ubc.ca · kevin.ma@hakai.org
