Seaweed-Herbivore Interactions: Grazing as Biotic Filtering in Intertidal Antarctic Ecosystems

Abstract

Consumers constitute a key component of the environmental filters that restrict the establishment of colonists into local assemblages. Thus, the trophic activity of consumers, particularly grazers, can be pivotal to control the development of potential algal invaders in Antarctic coasts. Here, the consumptive effects of coastal macrobenthic grazers on algal communities are reviewed to assess the degree to which these consumers can mediate the introduction of seaweeds in intertidal Antarctic communities. Gastropods and amphipods have strong consumptive effects on algal communities. Yet, amphipods are sensitive to climate change factors such as warming and acidification, which could hamper their ability to control native and alien macroalgae. Alien macroalgae that modify the abiotic environment, such as the gutweed Ulva intestinalis in tidepools, represent potential superior competitors in Antarctic ecosystems. In this line, simulations based on a simple probabilistic model showed that intermediate to high levels of frequency-dependent consumption seem to be fundamental to allow for stable coexistence when the alien species is competitively superior. With this work, I hope to stimulate further manipulative research to assess the role of benthic consumers in mediating the coexistence (or lack thereof) between alien and native seaweeds under multiple climate change scenarios.