Direct and indirect effects of ocean acidification and warming on a marine plant–herbivore interaction

Abstract

The impacts of climatic change on organisms depend on the interaction of multiple stressors and how these may affect the interactions among species. Consumer-prey relationships may be altered by changes to the abundance of either species, or by changes to the per capita interaction strength among species. To examine the effects of multiple stressors on a species interaction, we test the direct, interactive effects of ocean warming and lowered pH on an abundant marine herbivore (the amphipod Peramphithoe parmerong), and whether this herbivore is affected indirectly by these stressors altering the palatability of its algal food (Sargassum linearifolium). Both increased temperature and lowered pH independently reduced amphipod survival and growth, with the impacts of temperature outweighing those associated with reduced pH. Amphipods were further affected indirectly by changes to the palatability of their food source. The temperature and pH conditions in which algae were grown interacted to affect algal palatability, with acidified conditions only affecting feeding rates when algae were also grown at elevated temperatures. Feeding rates were largely unaffected by the conditions faced by the herbivore while feeding. These results indicate that, in addition to the direct effects on herbivore abundance, climatic stressors will affect the strength of plant-herbivore interactions by changes to the susceptibility of plant tissues to herbivory.

The stunting effect of a high CO2ocean on calcification and development in sea urchin larvae, a synthesis from the tropics to the poles

“…It is also important to consider the impact of acidification on algal condition. In microcosms where grazers and algae were reared in ocean acidification and warming conditions, consumption by grazers was reduced and algae was less palatable to grazers [85,86]. Reduced larval calcification in near-future ocean acidification conditions is also evident for the calcifying larvae of molluscs [87,88].…”

Ocean acidification affects growth but not nutritional quality of the seaweed Fucus vesiculosus (Phaeophyceae, Fucales)

“…However, indirect effects of ocean acidification, which are mediated through altered species interactions, have received much less attention (Falkenberg et al, 2013a,b;Poore et al, 2013). Indirect effects can modify single species responses, and are thus crucial for a comprehensive understanding of the implications of global climate change for the structure and functioning of marine ecosystems (Alsterberg et al, 2013).…”

Species interactions can shift the response of a maerl bed community to ocean acidification and warming

“…Epiphyte overgrowth is thus likely to adversely affect underlying coralline algae, increasing the shading effect at light and the pH decline in the dark. Climate change may also affect other components that we did not assess in the present study, such as algal palatability and potential changes in grazer trophic behaviour (Campbell et al, 2014;Duarte et al, 2015;Poore et al, 2013Poore et al, , 2016. Algal palatability to grazers may also be affected by predicted changes through shifts in the composition and the quantity of allelopathic compounds, as suggested by Del Monaco et al (2017).…”