Date of Award

6-2023

Degree Name

MS in Biological Sciences

Department/Program

Biological Sciences

College

College of Science and Mathematics

Advisor

Kristin Hardy

Advisor Department

Biological Sciences

Advisor College

College of Science and Mathematics

Abstract

Sessile invertebrates in the rocky intertidal experience intermittent periods of air exposure due to tidal flux, presenting risks of temperature extremes, hypoxia, nutrient limitation, and most dangerously, desiccation. Microscale variation in severity and frequency of these risks is widely dependent on vertical position within the intertidal zone. Common acorn barnacles (Balanus glandula) have a wide vertical distribution in the intertidal, creating large differences in microhabitat between the highest and lowest individuals in the population. This study set out to explore whether tidal position dependent differences exist in the response to oxygen and desiccation stress in B. glandula. We hypothesized that B. glandula from relatively high tidal heights, which are exposed to the air for a greater duration, will be better suited to tolerate anoxic and desiccation stress than conspecifics from lower tidal heights. To explore this, we compared responses of B. glandula collected from high and low intertidal positions to A) anoxia (0 mg O2/L) and hypoxia (≤ 2 mg O2/L) on survival, behavior (closed opercular plates, cirral beating, pneumostome formation), enzyme activity (lactate dehydrogenase (LDH), superoxide dismutase (SOD)), and tissue-lactate accumulation, in addition to B) the effects of humid (98% RH) and dry (32% RH) air emersion (at 17˚C) on survival, opercular behavior (open/closed), evaporative water loss (EWL) rates, and tissue-lactate accumulation. Relative to barnacles from the low intertidal, we found that barnacles from the high intertidal survive longer during anoxia and air emersion stress, close their operculum sooner in dry air, lose more water during air exposure at any humidity level, and tend to accumulate less D-lactate. We suspect that high intertidal B. glandula can survive desiccation longer by ejecting stores of mantle cavity fluid, thereby creating a moist lung-like, air-filled internal environment, then remaining largely closed and metabolically inactive when in air to avoid drying out and becoming anoxic. These differences may reflect plasticity or selective pressure in response to environmental stress during development and highlight the potential importance of microscale stress heterogeneity in influencing species climate change tolerance and potential distribution patterns.

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