Climate Change Amelioration by Marine Producers: Does Dominance Predict Impact?

AbstractClimate change threatens biodiversity worldwide, and assessing how those changes will impact communities will be critical for conservation. Dominant primary producers can alter local-scale environmental conditions, reducing temperature shading and mitigating ocean acidification photosynthesis, which could buffer communities from the impacts of climate change. We conducted two experiments on the coast of southeastern Alaska to assess the effects of a common seaweed species, , on temperature and pH in field tide pools and tide pool mesocosms. We found that was numerically dominant in this system, covering >60% of habitable space in the pools and accounting for >40% of live cover. However, while had a density-dependent effect on pH in isolated mesocosms, we did not find a consistent effect of on either pH or water temperature in tide pools in the field. These results suggest that the amelioration of climate change impacts in immersed marine ecosystems by primary producers is not universal and likely depends on species' functional attributes, including photosynthetic rate and physical structure, in addition to abundance or dominance.