Role of initial energy reserves in stress tolerance thresholds during the early benthic phase in intertidal invertebrates

Abstract

Although depleted energy reserves are not a major direct cause of early benthic phase mortality for many species of marine invertebrates, initial energy reserves might nevertheless play a role in early benthic phase mortality through indirect effects on physiological tolerance thresholds, a mechanism that has not been tested. We therefore examined the extent to which energy reserves affect acute tolerance thresholds of early benthic phase individuals of 2 species (Balanus glandula and Nucella ostrina) to 2 of the most challenging intertidal stressors: desiccation and high emersion temperature. Energy reserve levels were estimated by maintaining individuals without food for different durations of time or using individuals of different body mass. Individuals in each energy level treatment were then exposed to a range of desiccation periods and emersion temperatures. Lower estimated energy levels had no effect on tolerance to emersion temperature, but did significantly reduce the ability to tolerate desiccation. This suggests the survival of individuals through the early benthic phase is likely dependent on initial energy content through an indirect effect on tolerance to desiccation. Also, habitats experiencing intense desiccation likely impose a selective pressure on intertidal invertebrates favoring the evolution of greater energy reserves at the onset of the early benthic phase. These findings suggest depleted energy reserves at the onset of the early benthic phase can influence early benthic phase mortality through indirect effects by making individuals more vulnerable to environmental stressors. In this way, energy reserves may impact recruitment rates and thus influence population dynamics and intertidal community structure.

Life‐stage‐dependent effects of multiple flood‐associated stressors on a coastal foundational species

“…Newly settled juveniles can be extremely sensitive to physiological stressors and experience high mortality rates (Gosselin & Qian, 1997; Hunt & Scheibling, 1997). Elevated metabolic demands and reduced feeding rates that occur during metamorphosis contribute to post‐settlement susceptibility to stressful environmental conditions (Garcı́a‐Esquivel & Bricelj, 2001; Mendt & Gosselin, 2022). Low salinity caused substantial lethal effects on post‐settlement juveniles in our laboratory exposure (Figure 4a).…”