COMPARING TWO METRICS OF THERMAL TOLERANCE TO QUANTIFY THE EFFECTS OF STARVATION ON THERMAL LIMITS IN A COMMON COPEPOD

Several techniques are used to quantify thermal limits in aquatic species. The Critical Thermal maximum (CTmax) is a common technique that uses a loss of response to stimulus as an endpoint under rapid, acute temperature ramping. In contrast, other studies use mortality under exposure to a constant temperature to quantify the thermal limit. Due to the shorter duration of thermal stress, CTmax gives a higher thermal limit than most mortality-based metrics. Thermal limits are often reported using only a single method per study; therefore, a more robust understanding of the relationship between thermal tolerance techniques is needed. We measure the thermal tolerance of a common coastal copepod, Acartia tonsa, using CTmax and Lethal Temperature 50 (LT50, the temperature at which mortality is 50% after 24 hours of exposure) under food replete and starvation conditions. We found that CTmax was ~ 35.5°C for both treatments and unaffected by starvation. LT50, however, was significantly affected by starvation with starved individuals seeing an LT50 of 25.8°C compared to 30.5°C for the food replete treatment. Temperatures at our collection site can exceed 26°C, meaning that short term food limitation can cause mass mortality at ecologically relevant temperatures, a finding that is not illustrated in CTmax measurements alone.

Presentation Preference: Standard Oral (12 Minutes)

Primary Presenter: Rowan Batts, University of Connecticut (rowan.batts@uconn.edu)

Authors:

Rowan Batts, University of Connecticut  (rowan.batts@uconn.edu)

Ava Aerlo, Western Washington University  (ava@arleo.net)

Hans Dam, University of Connecticut  (hans.dam@uconn.edu)