Effects of environmental stress on intertidal mussels and their sea star predators

Abstract

Consumer stress models of ecological theory predict that predators are more susceptible to stress than their prey. Intertidal mussels, Mytilus californianus, span a vertical stress gradient from the low zone (lower stress) to the high zone (higher thermal and desiccation stress), while their sea star predators, Pisaster ochraceus, range from the low zone only into the lower edge of the mussel zone. In summer 2003, we tested the responses of sea stars and mussels to environmental stress in an experiment conducted on the Oregon coast. Mussels were transplanted from the middle of the mussel bed to cages in the low and high edges of the mussel bed. Sea star predators were added to half of the mussel cages. Mussels and sea stars were sampled between June and August for indicators of sublethal stress. Mussel growth was measured, and tissues were collected for heat shock protein (Hsp70) analyses and histological analyses of reproduction. Sea stars were weighed, and tissues were sampled for Hsp70 analyses. Mussels in high-edge cages had higher levels of total Hsp70 and exhibited spawning activity earlier in the summer than mussels in the low-edge cages. Sea stars suffered high mortality in the high edge, and low-edge sea stars lost weight but showed no differences in Hsp70 production. These results suggest that stress in the intertidal zone affected the mobile predator more than its sessile prey, which is consistent with predictions of consumer stress models.

Species richness and diversity across rocky intertidal elevation gradients in Helgoland: testing predictions from an environmental stress model

“…In rocky intertidal habitats, high elevations are often only occupied by truly intertidal species, which decrease in richness toward the upper intertidal boundary without sharing the substrate with the terrestrial species (e.g., vascular plants) that occur above (Raffaelli and Hawkins 1996). Thus, ESM predictions (low richness and diversity, and abiotic stress determining dynamics) are often met at the high intertidal zone Russell et al 2006;Scrosati and Heaven 2007;Petes et al 2008). In contrast, because of its limited aerial exposure, the low intertidal zone includes some species that primarily belong to subtidal biotas.…”

Micro-scale environmental variation amplifies physiological variation among individual mussels

“…see fig. 2 in [65]). We cannot rule out roles for these other parameters in driving physiological variation, nor can we yet determine at which life-history stage(s) (e.g.…”

Opposite responses by an intertidal predator to increasing aquatic and aerial temperatures

“…While there is some evidence that mobile intertidal predators are more sensitive to thermal stress than their prey (e.g. Petes et al 2008), experimental tests of the CSM have been inconclusive (Menge et al 2002). Moreover, under some conditions the reverse may be likely, especially when the predators are better able than their prey to thermoregulate (Broitman et al 2008).…”