SGER: Development of a method to measure feeding by copepods using qPCR

University Of Rhode Island, Kingston RI

Investigators

Abstract

This project will attempt to development a new method using molecular techniques to quantitatively measure in situ consumption rates of copepods on different phytoplankton and microzooplankton prey species. The approach will be to use the 18S ribosomal RNA gene as a marker to identify different prey species in the guts of copepods and to use quantitative real-time polymerase chain reaction (q-PCR) to measure of the amount of each species of prey in the stomachs of the copepods. By combining this gut content information with DNA digestion rates the investigators will be able to calculate feeding rate on these different prey species. The work will proceed in several phases: (1) develop and test group-specific primers, (2) carry out laboratory experiments to determine DNA digestion rates by copepods, (3) determine the 18S copy number per prey organism for selected prey species, (4) sample Calanus finmarchicus from the Gulf of Maine/Georges Bank region during late spring and generate a clone library from the gut contents using the group-specific primers. Species-specific primers developed from this clone library will be used with qPCR to quantify the prey DNA. Experiments will be carried out with the same group of animals to measure DNA digestion rates for selected prey species in the field. Ingestion rates will be calculated and compared with rates using the gut pigment method. Broader Impacts: While some aspects of the research are high risk, the potential payoff will considerable. Understanding the effect of changing environmental conditions on zooplankton and their role in controlling the fate of phytoplankton requires knowledge of their in situ feeding rates. Because of the strong gradients in the food environment in many regions of the ocean e.g. thin layers, ice edge and under ice regions, we argue traditional bottle incubation techniques for measuring in situ feeding by copepods are not appropriate. The methods being developed will allow direct in situ consumption estimates of different prey species overcoming these previous limitations. This research will result in the development of methods that will have many applications for investigating in situ predator-prey interactions in the marine environment because of its sensitivity and ability to measure ingestion rate of individual prey species present at low concentrations in the environment. Examples include fish larvae, deep-sea fishes, euphausiids, and amphipods. This knowledge would lead to new insights as to how the oceanic food web is functioning. The project will involve participation of a Graduate Student.