Meeting Abstract
Splash pools along rocky coastlines experience daily fluctuations of environmental parameters such as temperature, dissolved oxygen, pH and salinity, often reaching levels beyond the physiological tolerance of most organisms. Yet, along the Pacific coast the copepod T. californicus can be found in high abundance, making it a useful model to study how multivariate environmental fluctuations influence physiology and behavior. We examined the interactive effects of temperature and oxygen levels on thermal tolerance and preference behavior of T. californicus. Given the temporal correspondence between high temperatures and high oxygen levels in the field, we first set out to test the Oxygen Capacity Limited Thermal Tolerance hypothesis (OCLTT) by exposing egg-mass bearing females (n=384) to one of four acute levels of oxygen ranging from hypoxic to hyperoxic, coinciding with a heat ramp with peak temperatures ranging from 34.1°C to 38°C. Female survival was monitored for one week following exposure. The results indicate a higher survival rate in females exposed to high oxygen while simultaneously exposed to high temperature, supporting the OCLTT hypothesis. However, the effect size is small in magnitude. A second set of females were used to determine preference when exposed simultaneously to gradients of temperatures (12-29°C) and oxygen saturation (15-210%). Results to date indicate a trend of thermal preference being modulated by dissolved oxygen levels; distribution appeared unaffected by oxygen levels at low temperatures, but females avoided hypoxia at high temperature. Addressing how organisms respond to realistic combinations of environmental conditions can help us better predict the outcomes of future changes.
