Impact of temperature on larval mortality and performance of the acorn barnacle Chthamalus fissus in San Diego, CA

Abstract

Rising ocean temperatures and increasingly frequent marine heatwaves threaten the physiological performance and survival of marine larvae. This study quantifies the thermal tolerance, respiration, and swimming behavior of Chthamalus fissus cyprid larvae to establish a baseline for understanding their vulnerability under future climate scenarios. Larvae were collected from the Scripps Pier in La Jolla, CA and exposed to a range of temperatures (12–50°C, dependent on the experiment) to assess oxygen consumption, mortality, and swimming speeds. Oxygen consumption rates increased significantly with temperature, peaking at 30°C, with cyprids exposed to temperatures above 26°C showing significantly higher respiration rates than those below this threshold. The median lethal temperature (LT₅₀) was 40.2°C, indicating high acute thermal tolerance. However, swimming behavior declined above 26°C, with cyprids at 40°C exhibiting slower mean swim speeds. These results suggest that while C. fissus cyprids can survive short-term thermal extremes, their performance and potential for successful settlement may be compromised under prolonged or sublethal warming conditions. Future work can observe long term exposure impact of temperature on larval performance, population-level differences, and sublethal stress indicators such as heat shock protein expression to better predict the ecological consequences of local warming scenarios on this foundation species