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