Jake Dytnerski
Ph.D. candidate
Research
Hong Kong has a seasonally dynamic marine environment. Summer sea surface temperatures can exceed 30°C whereas winter temperatures can drop below 15°C. This range in temperature allows for year-round coral communities, and abundant growth of macroalgae in the winter. For my PhD, I am researching the role of the long-spined sea urchin, Diadema setosum, in the ecosystem, here in Hong Kong. Much work has been done on Diadema antillarum in the Caribbean, and some work has been done on the D. setosum as a bioeroder of coral reefs in the tropics. However, little is known about which marcoalgae these urchins feed on; how they affect the seasonal patterns of macroalgae growth and distribution; if the urchins target living corals here in Hong Kong or just the turf algae that grows on the dead skeletons of the corals. Answering these questions will help understand the food sources of the urchins and how their energy stores vary with the seasonal change in food abundance. I am also interested in the connectivity of the populations of D. setosum across its range, as they can be found from the East coast of Africa to French Polynesia, from Honshu, Japan to NSW, Australia. I want to compare the physiological performance of the urchins from stable tropical environments and highly variable environments to determine if they show extensive physiological plasticity, or if populations have adapted to variable environments. This will allow me to predict how these important grazers will cope with future conditions across their range.
Education
2016: Bachelor of Science, Honours Marine Biology, University of British Columbia, Canada
2013: Arts and Science Diploma: Biology, Langara College, Canada
Awards
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2015: Dean of Science Scholarship – Biology research grant
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2013: Betty and Tony Pletcher Memorial Scholarship – For Achievement in Biology
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2012: Real Estate Foundation Biology Student Bursary – Bursary for Biology students
Ecological Restoration
Oyster Reef Restoration
Over 80% of oyster reefs have been lost globally. In their natural state, some oyster species form complex reef-structures which provide habitat for hundreds of other species, increasing the productivity of these systems in terms of biodiversity and for commercial fisheries for humans. The oysters themselves enhance nutrient cycling, filtering and cleaning the water of organic matter and pollutants
Hong Kong was a major port of oyster harvest for China from the Qing Dynasty, and has records of harvest from at least 700 years ago. It was a major exporter of lime, produced from burning the shells in kilns, and oyster meat. This meant that the oyster reefs in Hong Kong were harvested to the point that they are now almost non-existent as a habitat, completely changing the shores of Hong Kong without intervention and restoration. We are working the the Nature Conservancy to restore oyster reefs in Hong Kong.
https://www.tnc.org.hk/en-hk/what-we-do/hong-kong-projects/oyster-restoration/
From our research with TNC we have calculated that 7 m2 of Hong Kong oysters can filter an Olympic swimming pool per day.
Filtration Experiment
Water filtration at 15 °C over a tme lapse of 40 minutes
Filtration Experiment
Water filtration at 30 °C over a time lapse of 30 minutes
Benefits of sea urchins to coral communities
In this study, we look at algae settlement, sediment accumulation, and growth and survival rates of three common genera of corals in Hong Kong in the presence and absence of urchins. The goal is to assess the impacts of urchins on coral communities to inform local government of how urchins promote growth, increase survival and reduce sediment accumulation. Therefore, we seek to help shape policy on future urchin culls.
