Award: OCE-0962074

Copepods are tiny crustaceans (most are less than a millimeter) that live in the oceans and in lakes. Although small, they are ubiquitous--they are one of the most abundant group of animals on the planet, and they play a central role in marine foodwebs. The main goal of our project was to develop new techniques for modeling copepods and to use these models to understand how they are distributed in the ocean. Like all animals, copepods start small and have to grow and develop before they can reproduce. This creates a trade-off between maturing quickly but at a small size or maturing slowly but being larger. Each copepod species balances this trade-off in a different way, one that allows it to be successful in a particular environment. In warm waters where seasonal cycles are small, many copepods take the "quick but small" strategy. In colder waters with strong annual cycles in temperature and productivity, many species take the "slow but big" strategy. This allows them to produce huge numbers of eggs when conditions are right and to accumulate energy reserves to survive adverse periods. Modeling this trade-off and understanding its consequences were the major goal of our project. We began be developing a general model of the growth-development trade-off. We call this model the "compupod model." This relatively simple model can represent a wide variety of copepod species. We then used this model to explore how copepods are adapted to different ocean environments. One of our central studies created several artificial oceans regions, each representing conditions (temperature and primary production) along a north-south gradient in the Atlantic. We seeded each region with several randomly created compupods, each with a different solution to the growth-development trade-off. We then allowed the compupods to grow and compete, and we examined the combinations of life-history strategies that work in each environment. We found a higher diversity of strategies and relatively few large copepods in the warm environments. We found fewer strategies in the cold environment and usually one large species dominated. These patterns are similar to those found in nature, suggesting that the growth-development trade-off is central to explaining the distribution of copepod species in the ocean. We also used the compupod model to examine in more detail a particular strategy employed by large copepods. Many large species, especially in colder environments, accumulate energy reserves and use these to persist during poor conditions. This strategy, known as diapause, is central to the success of many of the most important copepod species, including those that are food for fish and whales. We also used a simplified version of the compupod model to explain why the distribution of the number of copepod species does not change with temperature in the manner predicted by standard ecological theory. Our work is continuing on multiple fronts. Dr. Frederic Maps is now a professor at the Universite Laval and is using the compupod approach in the Arctic. Dr. Nicholas Record, now at Bigelow, is continuing this work in the Gulf of Maine. Dr. Andrew Pershing, along with graduate student Karen Stamieszkin is using many of the ideas developed in this study to understand how copepods contribute to the flux of organic matter from the productive surface waters to the ocean bottom. This flux supports the growth of animals on the ocean floor and is important for removing carbon from the atmosphere. Last Modified: 07/06/2014 Submitted by: Andrew J Pershing