Meeting Abstract
Withering syndrome (WS), a bacterial disease, has led to population declines in all northeastern Pacific abalone species infected and impacts animals more severely during periods of thermal stress. This study aims to determine the mechanistic impacts of WS and heat stress on abalone digestive function by examining gut function in wild red abalone (H. rufescens) and comparing their gut function to WS-free New Zealand pāua (H. iris). We hypothesized that abalone digestive function is unable to keep pace with increased metabolic demand at the highest temperatures they experience in the wild, thereby making them more vulnerable to heat stress and WS in the face of climate change. We conducted 4-week thermal stress feeding experiments with both species. Red abalone and pāua were divided into 2 temperature regimes, ambient seawater and 6°C above ambient. We measured total organic matter and individual macronutrient (protein, carbohydrate, and lipid) digestibility to determine how thermal stress impacts the animals’ ability to extract nutrients and energy from their diet. We also measured metabolic rate (via O2 consumption) at both temperatures to determine whether the changes in digestive function enable animals to extract enough energy to meet their increased metabolic demand at elevated temperatures. Preliminary results show that metabolic demand is significantly elevated during the thermal stress treatment and that species differ in their digestive efficiencies, but have the reserve capacity to handle the 6°C challenge. This is one of the first detailed studies on abalone digestion, and collaborations with international fishing, aquaculture, and management agencies is enabling this data to be integrated into management.
