Dr. Don Deibel

Professor (Research)

Ocean Sciences Centre

Memorial University of Newfoundland

St. John's, Newfoundland, Canada, A1C 5S7

Current Research Projects

1. Pelagic tunicate life history adaptations and role in biogeochemical cycles

Since my graduate student days I have been interested in the feeding behaviour and rates, and role in biogeochemical cycles, of three groups of pelagic tunicates, the salps, doliolids and larvaceans. I have been working on larvacean tunicates in Arctic polynyas, where we have determined population dynamics and feeding rates. Work in Newfoundland coastal waters on larvacean life history has lead to the development of a new tool for determination of the age of larvaceans captured in nature (i.e. statolith diameter), enabling the first determination of their age-dependent traits. We have found that the three sympatric species living here are separated in time and space along a temperature-salinity gradient, and that the species seem to be differentially adapted to seasonal environmental conditions, with Oikopleura vanhoeffeni maximizing clutch size while O. labradoriensis minimizes generation time. In the next few years we will be developing species-specific TaqMan genetic assays to examine speciation and population connectivity in pan-Arctic larvaceans. Recent graduate students involved in this work were Dr. Nami Choe, and Ainsley Latour.

2. Ecology and molecular genetics of ascidian tunicates

Although much of my career has concerned research on pelagic tunicates, over the past 8 years I have begun work on the feeding behaviour and population ecology and genetics of benthic ascidian tunicates. This work has resulted in the submission of 16 gene sequences to GenBank. We have discovered two non-indigenous ascidian species in Newfoundland that are severe pests of aquaculture operations elsewhere in Canada. Our research on somatic growth rates, sexual reproductive output, larval recruitment and adult abundance is helping government managers to make well-founded decisions about where and when to apply mitigation measures. We have determined that ascidians consume marine snow particles, that feeding rates are depressed by the mechanical effects of viscosity at low temperatures, and that the cytochrome c oxidase I gene of mtDNA can be used to identify non-indigenous ascidian species in Newfoundland. Our more recent work in Arnold's Cove has demonstrated constraints on lifetime reproduction by the short growing season in Newfoundland sub-Arctic waters, and life history adaptations to these time constraints, including early maturation at a small colony size. Dr. Ben Lowen (post-doctoral fellow) is coordinating our research team, which consists of recent graduate students Ashley Callahan, Kevin Ma and Gavin Applin.

3. Ecology of benthic boundary layer and water column zooplankton in cold ocean fjords

There is an abundant and diverse community of zooplankton living within a few meters of the ocean floor. However, since this community is difficult to sample, very little is known about its ecology. Together with R.J. Thompson, C.C. Parrish and some talented students, I have been studying the abundance, life cycles and seasonal energy storage (lipids and fatty acids) of dominant members of the benthic boundary layer zooplankton of Newfoundland fjords. We have found that some taxa (mysid shrimp) respond quickly to fresh phytodetritus originating from the sinking spring diatom bloom, while other taxa respond more slowly (amphipods) or not at all (predators such as chaetognaths). Furthermore, we have identified those species that can provide high-energy lipids and essential fatty acids to commercially-important groundfish species. We have extended this work onto the Beaufort Sea shelf, where we determined benthic boundary layer seston biogeochemistry and zooplankton lipids, lipid classes and fatty acids (both water column and benthic boundary layer). Recent graduate students who lead this work were Drs. Catherine Stevens, Nicole Richoux and Tara Connelly.