Climate change amelioration by marine producers: Does dominance predict impact?

Climate 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 via shading and mitigating ocean acidification via 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, Neorhodomela oregona, on temperature and pH in field tide pools and tide pool mesocosms. We found that N. oregona was numerically dominant in this system, covering >60% of habitable space in the pools and accounting for >40% of live cover. However, while N. oregona had a density-dependent effect on pH in isolated mesocosms, we did not find a consistent effect of N. oregona on either pH or water temperature in tide pools in the field. These results suggest that the amelioration of climate change impacts i..., Study Site: To evaluate the role of the abundant alga Neorhodomela oregona (Doty) Masuda in driving local climate conditions, we conducted “removal” and “mesocosm” experiments at John Brown’s Beach (57.05° N, 135.33° W) near Sitka, Alaska from 05 Jul 2019 to 27 Sep 2019. Southeast Alaska was an ideal location for this study as it has been subjected to relatively low levels of direct human disturbance yet is experiencing rapid environmental change (Stafford et al., 2000). Air temperature in Southeast Alaska has increased by ~0.11°C per decade since 1830 (Wendler et al., 2016; Jewett and Romanou, 2017), well above the global mean rate of 0.07°C per decade (since 1880; Blunden and Arndt, 2019). Sea surface ocean pH has declined by 0.03 units over a recent 15-year window (1991-2006) in the northeast Pacific waters off the Alaskan coast (Byrne et al., 2010).
Removal Experiment: We selected 10 tide pools, which ranged from 2.5 - 23.5 L in volume and 2.49 - 3.29 m in tide height (i.e., vertica...,