Alexandra Kinnby1, Gunnar Cervin1, Ann Larsson1, Ulrica Edlund2, Gunilla, B. Toth1, and Henrik Pavia1
1Tjärnö Marine Laboratory, Department of Marine Sciences, University of Gothenburg, Strömstad, Sweden
2Fibre and Polymer Technology, KTH Royal Institute of Technology, SE-100 44 Stockholm, Sweden
Climate change due to anthropogenic activities has already resulted in unprecedented global changes, in part due to ocean acidification which can have powerful effects in the nearshore, shallow areas of the oceans where seaweeds are foundation species. Here we conducted experiments to investigate the effects of ocean acidification on the habitat-forming seaweed Fucus vesiculosus. We assessed effects on growth, thallus breaking strength, and drag, under both lab and field conditions. Additionally, we quantified the calcium and magnesium content of some seaweed tissues and compared this to scanning electron microscopy (SEM) imagery of thallus tissue to examine possible effects. Tissue resilience decreased when seaweeds were exposed to increased pCO2, corresponding with an increasing risk factor. This suggests that this species is more likely to suffer damage by mechanical stress such as grazing or wave action; we observed greater loss of these individuals in a field transplant experiment. Tissue exposed to increased pCO2 contained less calcium and magnesium, both of which are important the creation of structural alginate matrices. When these samples were viewed under SEM, there were voids forming in the tissue matrix of seaweeds grown under elevated pCO2 that were not present in control seaweeds. Reduced tissue resilience implies that climate change may lead to a future decline in populations of habitat-forming seaweeds, which may have large negative consequences on associated organisms that depend on this habitat-forming species. These effects could either be localized to specific populations or widespread, especially when combined with predicted increases to storm frequency and power.