TIDE: Tropic cascades and Interacting control processes in a Detritus-based aquatic Ecosystem.

Eutrophication, resulting from anthropogenic loading of nitrogen, is arguably the most pervasive problem in coastal ecosystem. The susceptibility to eutrophication differs between coastal systems, with systems dominated by marshes being apparently less susceptible compared to open water systems. The susceptibility is consistent with general ecosystem theory that suggests that a higher storage of detritus and recycling of nutrients contribute to ecosystem stability and resistance to change. Coastal marshes, however, exist in a fragile dynamic balance between C accretion and sea level rise and processes that affect rates of C accretion can alter that balance.

The second most pervasive change in ecosystems is altered community structure through overfishing and exotic species introductions. Overharvesting has contributed to alteration of trophic webs through both direct removal of species and through indirect effects on prey species. This alteration of species can have dramatic effects on food webs and also affect the rates of C accumulation by changing microbial and grazer populations.

Because of the interactive and non-linear responses of ecosystems to multiple disturbances, we can not assume that ecosystems will return to baseline following management actions to remove perturbations. Successful understanding of the response of ecosystems to change will require understanding the mechanisms controlling ecosystem dynamics and resistance to change. Such an understanding will depend on the fusion of biogeochemistry, microbial ecology, population & community ecology and the concepts of landscape ecology. In this project, we will employ an integrated approach to understand the consequences of different assumptions about the importance of biogeochemical and biotic controls on coastal ecosystems resistance to change.

We propose a 4-year program that will include two integrated efforts: First, whole ecosystem nutrient additions and species manipulation experiments that test the interaction of biogeochemical and biotic controls on the response of coastal marsh systems to change. Second, theoretical and synthetic modeling to integrate population dynamics, biogeochemical cycling and landscape changes.

This research advances ecological science in a number of ways. First, it considers the synergistic relationships among microbes, higher trophic levels, and landscape level changes in geomorphology to predict ecosystem response to change. Second, it will also develop a modeling method to link highly variable physical drivers with biogeochemical processes & higher trophic levels.