| Title: | Recovery of a top predator mediates negative eutrophic effects on seagrass |
| Author(s): | Hughes BB; Eby R; Van Dyke E; Tinker MT; Marks CI; Johnson KS; Wasson K; |
| Address: | "Department of Ecology and Evolutionary Biology, Long Marine Laboratory, University of California, Santa Cruz, CA 95060" |
| ISSN/ISBN: | 1091-6490 (Electronic) 0027-8424 (Print) 0027-8424 (Linking) |
| Abstract: | "A fundamental goal of the study of ecology is to determine the drivers of habitat-forming vegetation, with much emphasis given to the relative importance to vegetation of 'bottom-up' forces such as the role of nutrients and 'top-down' forces such as the influence of herbivores and their predators. For coastal vegetation (e.g., kelp, seagrass, marsh, and mangroves) it has been well demonstrated that alterations to bottom-up forcing can cause major disturbances leading to loss of dominant vegetation. One such process is anthropogenic nutrient loading, which can lead to major changes in the abundance and species composition of primary producers, ultimately affecting important ecosystem services. In contrast, much less is known about the relative importance of apex predators on coastal vegetated ecosystems because most top predator populations have been depleted or lost completely. Here we provide evidence that an unusual four-level trophic cascade applies in one such system, whereby a top predator mitigates the bottom-up influences of nutrient loading. In a study of seagrass beds in an estuarine ecosystem exposed to extreme nutrient loading, we use a combination of a 50-y time series analysis, spatial comparisons, and mesocosm and field experiments to demonstrate that sea otters (Enhydra lutris) promote the growth and expansion of eelgrass (Zostera marina) through a trophic cascade, counteracting the negative effects of agriculturally induced nutrient loading. Our results add to a small but growing body of literature illustrating that significant interactions between bottom-up and top-down forces occur, in this case with consequences for the conservation of valued ecosystem services provided by seagrass" |
| Keywords: | "Analysis of Variance Animals Brachyura/*physiology California Estuaries Eutrophication/*physiology *Food Chain History, 20th Century History, 21st Century Nitrates/analysis Otters/*physiology Population Dynamics/history Zosteraceae/*growth & development e;" |
| Notes: | "MedlineHughes, Brent B Eby, Ron Van Dyke, Eric Tinker, M Tim Marks, Corina I Johnson, Kenneth S Wasson, Kerstin eng Comparative Study Historical Article Meta-Analysis Research Support, Non-U.S. Gov't Research Support, U.S. Gov't, Non-P.H.S. 2013/08/29 Proc Natl Acad Sci U S A. 2013 Sep 17; 110(38):15313-8. doi: 10.1073/pnas.1302805110. Epub 2013 Aug 27" |
