Unexpected resilience of a seagrass system exposed to global stressors.

Autor: Hughes BB; Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, USA.; Division of Marine Science and Conservation, Nicholas School of the Environment, Duke University, Beaufort, NC, USA., Lummis SC; Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, USA., Anderson SC; School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA., Kroeker KJ; Department of Ecology and Evolutionary Biology, University of California, Santa Cruz, CA, USA.
Jazyk: angličtina
Zdroj: Global change biology [Glob Chang Biol] 2018 Jan; Vol. 24 (1), pp. 224-234. Date of Electronic Publication: 2017 Sep 13.
DOI: 10.1111/gcb.13854
Abstrakt: Despite a growing interest in identifying tipping points in response to environmental change, our understanding of the ecological mechanisms underlying nonlinear ecosystem dynamics is limited. Ecosystems governed by strong species interactions can provide important insight into how nonlinear relationships between organisms and their environment propagate through ecosystems, and the potential for environmentally mediated species interactions to drive or protect against sudden ecosystem shifts. Here, we experimentally determine the functional relationships (i.e., the shapes of the relationships between predictor and response variables) of a seagrass assemblage with well-defined species interactions to ocean acidification (enrichment of CO 2 ) in isolation and in combination with nutrient loading. We demonstrate that the effect of ocean acidification on grazer biomass (Phyllaplysia taylori and Idotea resecata) was quadratic, with the peak of grazer biomass at mid-pH levels. Algal grazing was negatively affected by nutrients, potentially due to low grazer affinity for macroalgae (Ulva intestinalis), as recruitment of both macroalgae and diatoms were favored in elevated nutrient conditions. This led to an exponential increase in macroalgal and epiphyte biomass with ocean acidification, regardless of nutrient concentration. When left unchecked, algae can cause declines in seagrass productivity and persistence through shading and competition. Despite quadratic and exponential functional relationships to stressors that could cause a nonlinear decrease in seagrass biomass, productivity of our model seagrass-the eelgrass (Zostera marina)- remained highly resilient to increasing acidification. These results suggest that important species interactions governing ecosystem dynamics may shift with environmental change, and ecosystem state may be decoupled from ecological responses at lower levels of organization.
(© 2017 John Wiley & Sons Ltd.)
Databáze: MEDLINE
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