COS 56-4
Effects of ocean acidification on coralline algal community dynamics: Integrating experiments, historical data, and spatial models across biological scales
The process of ocean acidification is driving important changes in coastal seawater chemistry. Experimental evidence suggests that acidification may be a greater stressor to some organisms than others, including within communities and guilds of interacting species. In light of recent changes in ocean carbon chemistry in the Northeast Pacific and the availability of historical interaction and abundance baselines of crustose coralline algae (CCA), we asked whether changing ocean acidity over 30 years has altered community function through changes in species abundance and competitive interactions.
Results/Conclusions
Comparison of competition between CCA from the 1980s and 2010s revealed a reversal of competitive dominance in this guild. Competition experiments showed a markedly lower competitive ability of the previous competitively dominant species and a decreased response of competitive dynamics to grazer presence. Competitive networks obtained from field surveys show concordance between the 1980s and 2013, yet also reveal more intransitive interaction strengths across this guild. Further work linked changes in skeletal morphology to ecological traits related to competitive ability, offering a mechanistic understanding of these changes across biological scales. Here, we build upon this work to explore ecological dynamics of CCA using a spatial cellular automaton model parameterized with empirical data. We present evidence that ocean acidification, due to its energetic demands, may have supplanted the role of herbivores in promoting intransitivity and species diversity in this guild.