Climate change in the rocky intertidal zone: predicting and measuring the body temperature of a keystone predator

Abstract

Forecasting the responses of populations and ecosystems to climate change requires that we understand both the direct effects of temperature on organism physiology and the indirect effects of temperature change on interactions such as predation and competition. The sea star Pisaster ochraceus is a keystone predator in the rocky intertidal zone with a broad geographic distribution along the west coast of North America. We developed a mechanistic heat budget model that uses environmental data to predict the body temperatures of P. ochraceus. Model accuracy was verified by comparing model output temperatures, generated using measured microclimatic data as input, to the temperatures of live P. ochraceus in the field. The average absolute errors between predicted and measured body temperatures were ~1°C. To continuously monitor sea star body temperatures in the field, we developed data loggers that thermally mimic P. ochraceus. Accuracy of these biomimetic loggers was tested by comparing logger temperatures to P. ochraceus body temperatures, and they were found to mimic body temperatures within ~1°C. Loggers were deployed at different tidal heights at a site in Bamfield, British Columbia, Canada, to investigate within-site body temperature variation. We also explored the relationship between body temperature and vertical distribution of P. ochraceus. A negative correlation was found between maximum body temperatures on Day n and the number of sea stars found in the intertidal on Day n + 1. These results suggest that temperatures reached during aerial exposure at low tide, at least in part, may determine where in the intertidal zone these sea stars are located, which could affect their foraging limits.

Shore-level size gradients and thermal refuge use in the predatory sea star Pisaster ochraceus: the role of environmental stressors

“…We tested the effects of sea water temperature (Sanford 1999), air temperature (Pince bourde et al 2008), wind speed (Landenberger 1969), wave action (Sanford 2002), and solar radiation (Burnaford & Vasquez 2008), since all have been shown to affect sea star physiology, body temperature, and/or behavior (Szathmary et al 2009). We used data collected hourly by a weather station (200 m from the survey area) and associated wave height radar and seawater temperature sensors maintained by the Bodega Ocean Observing Node (www.bml.…”

“…We manipulated the data series as follows. First, we used aerial data corresponding to 1 d prior to each population survey, since aerial conditions would have had their impact during the previous day's aerial exposure (Szathmary et al 2009). We only used seawater temperature and wave height data recorded during high tide periods (>1 m above MLLW), and only used air temperature, wind speed, and solar radiation data recorded during low tide periods (≤1 m above MLLW).…”

“…To assess the temperatures individuals would experience in different microhabitats (potential body temperature), we used biomimetic temperature loggers (iButton DS1922, 0.0625°C resolution) embedded within a solid disc of foam (Aquazone single cell, Reilly Foam) to resemble the thermal properties of an average size Pisaster, ~200 g (Szathmary et al 2009). We deployed the sensors (robo-sea stars) at Strawberry Hill and Bodega during the summer of 2012, and continuously recorded (15 min sampling interval) Pisaster body temperature in sun-exposed (high, mid-, and low intertidal heights) and heat-protected microhabitats (crevices and tide pools).…”

From Space to the Rocky Intertidal: Using NASA MODIS Sea Surface Temperature and NOAA Water Temperature to Predict Intertidal Logger Temperature

“…While several biophysical models can accurately estimate body temperature of terrestrial and intertidal organisms, they are typically complex and require several variables to provide accurate results [18]. Among the many variables used in these models are air or water temperature collected by weather stations, ocean buoys, or field observations.…”

“…Rapid changes in body temperature of intertidal species can cause stress and may result in changes in population distributions after repeated exposure to such extremes [11,14,16]. Since body temperature directly influences the growth [7,17], ecology [18], and the distribution of mussels [19] and other intertidal species [20], being able to map body temperature across varying temporal and spatial scales is essential [18]. However, collecting in situ body temperature data in order to understand long-term, regional-scale climate effects on intertidal species can be logistically challenging.…”