@article {7311, title = {Feedbacks Between Nutrient Enrichment and Geomorphology Alter Bottom-Up Control on Food Webs}, journal = {Ecosystems}, year = {2018}, month = {May-05-2018}, abstract = {

Classic bottom-up theory predicts that increased resource availability (for example, nutrients) at the base of the food web will stimulate primary production and, in turn, secondary production. Recent studies, however, indicate that bottom-up controls on food web production can be modified by other factors, such as landscape configuration and continuity. As part of a 10-year ecosystem-scale experiment in a New England salt marsh, we investigated the response of secondary consumers, specifically a fish, the mummichog (Fundulus heteroclitus), to nutrient enrichment. In the first 6\ years, we observed a classic bottom-up response of increased production of algae, invertebrate prey, and mummichogs. After the sixth year, however, mummichog biomass declined to below reference levels by the eighth year. This decline in mummichog biomass coincided with nutrient-induced collapse of the low-marsh habitat. Based on stable isotope analyses, field surveys, and small-scale experiments, we suggest that the geomorphic changes induced a trophic decoupling between creek and marsh habitats, thereby reducing mummichog access to prey in the intermittently flooded marsh. Thus, despite continued stimulation of algal and invertebrate prey production, fish abundances declined to below pre-enrichment levels. Our results demonstrate how geomorphic controls can override classic bottom-up control and emphasize the importance of long-term studies in detecting the response of slow-turnover phenomena (for example, changing landscapes).

}, keywords = {Estuary, food web theory, landscape control, nutrient enrichment, salt marsh, spatially coupled geomorphology, trophic subsidy}, issn = {1432-9840}, doi = {10.1007/s10021-018-0265-x}, url = {http://link.springer.com/10.1007/s10021-018-0265-x}, author = {Nelson, James A. and Johnson, David Samuel and Deegan, Linda A. and Spivak, Amanda C. and Sommer, Nathalie R.} } @article {821, title = {Animating the Carbon Cycle}, journal = {Ecosystems}, year = {2013}, abstract = {Understanding the biogeochemical processes reg- ulating carbon cycling is central to mitigating atmospheric CO2 emissions. The role of living organisms has been accounted for, but the focus has traditionally been on contributions of plants and microbes. We develop the case that fully {\textquoteleft}{\textquoteleft}animating{\textquoteright}{\textquoteright} the carbon cycle requires broader consideration of the functional role of animals in mediating biogeochemical processes and quanti- fication of their effects on carbon storage and exchange among terrestrial and aquatic reservoirs and the atmosphere. To encourage more hypothesis-driven experimental research that quantifies animal effects we discuss the mechanisms by which animals may affect carbon ex- changes and storage within and among ecosystems and the atmosphere. We illustrate how those mechanisms lead to multiplier effects whose magnitudes may rival those of more traditional carbon storage and exchange rate estimates currently used in the carbon budget. Many animal species are already directly managed. Thus improved quantitative understanding of their influence on carbon budgets may create opportunity for management and policy to identify and implement new options for mitigating CO2 re- lease at regional scales.}, keywords = {animal management for carbon storage, animal mediation of carbon cycling, animal multiplier effects, biogeochemical cycling, regional carbon budgets}, issn = {1435-0629}, doi = {10.1007/s10021-013-9715-7}, author = {Schmitz, Oswald J. and Raymond, Peter A. and Estes, James A. and Kurz, Werner A. and Holtgrieve, Gordon W. and Ritchie, Mark E. and Schindler, Daniel E. and Spivak, Amanda C. and Wilson, Rod W. and Bradford, Mark A. and Christensen, Villy and Deegan, Linda A. and Smetacek, Victor and Vanni, Michael J. and Wilmers, Christopher C.} }