Responses to simultaneous anthropogenic and biological stressors were mixed in an experimental saltmarsh ecosystem. (July 2022)

• Record Type: Journal Article
• Authors: Blake, Rachael E.; Olin, Jill A.
• Is Part Of: Marine environmental research. Volume 179(2022)
• Publication Date: 2022-07
• Subjects: Saltmarsh -- Stressor -- Foundation species -- Herbivore -- Chemical -- Ecophysiology -- Experiment; Marine pollution -- Environmental aspects -- Periodicals; Marine ecology -- Periodicals; Mer -- Pollution -- Aspect de l'environnement -- Périodiques; Écologie marine -- Périodiques; Electronic journals; 577.705
• DOI: 10.1016/j.marenvres.2022.105644
• Languages: English
• ISSNs: 0141-1136

Abstract

Abstract: Coastal ecosystems are essential for absorbing and bouncing back from the impacts of climate change, yet accelerating climate change is causing anthropogenically-derived stressors in these ecosystems to grow. The effects of stressors are more difficult to foresee when they act simultaneously, however, predicting these effects is critical for understanding ecological change. Spartina alterniflora (Spartina), a foundational saltmarsh plant key to coastal resilience, is subject to biological stress such as herbivory, as well as anthropogenic stress such as chemical pollution. Using saltmarsh mesocosms as a model system in a fully factorial experiment, we tested whether the effects of herbivory and two chemicals (oil and dispersant) were mediated or magnified in combination. Spartina responded to stressors asynchronously; ecophysiology responded negatively to oil and herbivores in the first 2–3 weeks of the experiment, whereas biomass responded negatively to oil and herbivores cumulatively throughout the experiment. We generally found mixed multi-stressor effects, with slightly more antagonistic effects compared to either synergistic or additive effects, despite significant reductions in Spartina biomass and growth from both chemical and herbivore treatments. We also observed an indirect positive effect of oil on Spartina, via a direct negative effect on insect herbivores. Our findings suggest that multi-stressor effects in our model system, 1) are mixed but can be antagonistic more often than expected, a finding contrary to previous assumptions of primarily synergistic effects, 2) can vary in duration, 3) can be difficult to discern a priori, and 4) can lead to ecological surprises through indirect effects with implications for coastal resilience. This leads us to conclude that understanding the simultaneous effects of multiple stressors is critical for predicting foundation-species persistence, discerning ecosystem resilience, and managing and mitigating impacts on ecosystem services. Highlights: Multi-stressor effects were mixed with marginally more antagonistic than either synergistic or additive effects. Ecologically surprising indirect and direct effects were observed, in particular indirect positive effect of oil on plants. Asynchronous ecophysiological and biomass plant responses to anthropogenic stressors. Unified ecological theory for a predictive understanding of multi-stressor effects remains underdeveloped.