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Description
The organization of algae on temperate rocky reefs is dynamic and stochastic, and may be a result of variable oceanographic conditions paired with the algae’s unique life history characteristics. Evidence suggests that algal assemblages are stratified by functional groups, adaptive characteristics, and morphology; each layer has the potential to shade the layer below it and thereby dramatically influence kelp forest community composition. Alternatively, removal of canopy layers has been shown to elicit positive responses in understory assemblages due to increased irradiance at the benthos. Loss of individual algae can occur from disturbances of varying frequencies and magnitudes that can physically remove them from the benthos and thereby alter benthic irradiances. This study addresses gaps in knowledge about the role of red algal ecophysiology in this process through field and laboratory experiments in two geographically distinct locations of California. Specifically, I investigated whether red algal benthic cover is altered under different canopy manipulations (i.e. levels of disturbance), and if the elicited responses by the algae are due to differences in their photophysiology. Counter to expectations, red algal benthic cover in Point Loma and Carmel Bay, CA did not differ among levels of disturbance. In addition to this lack of responses to the experimental canopy manipulations, no differences in red algal photophysiology (measured in oxygen evolution) were detected during laboratory incubations under different irradiances. Rather, simple patchiness in red algae communities accounted for most of the variation observed in both locations, suggesting that community organization likely results, at least in part, from individual species’ life history characteristics, their ecologies, and stochastic processes. This study contributes to a new line of inquiry pertaining to the processes dictating red algal assemblages on temperate rocky reefs, which suggests that photophysiology does not appear to explain observed differences in red algal benthic cover, as had previously been hypothesized, and does not support photophysiology as a mechanism for that organization.
