MEPS 629:235-241 (2019)  -  DOI: https://doi.org/10.3354/meps13122

ABSTRACT: Global change stressors can alter mutually beneficial interactions in structurally complex systems, leading to impaired functionality and service provision. Knowledge of how this is influenced by species identity and degree of specialisation is limited in seagrass systems, but these are key considerations for their conservation. Here, we used a mesocosm experiment to quantify effects of ocean warming on fouling in a temperate seagrass (Zostera capensis) system using sympatric specialist (Critically Endangered Siphonaria compressa) and generalist (Fissurella mutabilis) epiphytic limpet grazers. Results indicate an increase in fouling loads due to warming, by up to 15 times in the absence of grazers. Grazers differentially countered fouling, with the specialist providing a stronger cleaning function, especially at high temperatures. The specialist showed greater survival (80-90%) at higher temperatures, while survival for the generalist was reduced (10-20%). Our findings highlight the need for specialist, warm-tolerant grazers to be prioritised in seagrass conservation/restoration programs. This will likely establish positive feedback loops that benefit both seagrasses and grazers under warming conditions, with positive community- and ecosystem-wide ramifications.

KEY WORDS: Biodiversity · Ecosystem engineer · Warming · Seagrass · Grazing