Linking rising pCO2 and temperature to the larval development and physiology of the American lobster (Homarus americanus)

Abstract

Few studies have evaluated the joint effects of elevated temperature and pCO2 on marine organisms. In this study we investigated the interactive effects of Intergovernmental Panel on Climate Change predicted temperature and pCO2 for the end of the 21st century on key aspects of larval development of the American lobster, Homarus americanus, an otherwise well-studied, iconic, and commercially prominent species in the northeastern United States and Atlantic Canada. Our experiments showed that larvae (stages I–III) and postlarvae (stage IV) reared in the high temperature treatments (19 °C) experienced significantly lower survival, developed twice as fast, and had significantly higher oxygen consumption rates, than those in ambient treatments (16 °C). Larvae from the ambient temperature/high pCO2 (750 ppm) treatment had significantly longer carapace lengths, greater dry masses in stages I–III and higher C: N ratios in stage IV than larvae from all other treatments. Stage IVs raised in the high pCO2 treatment at 19 °C had significantly higher feeding rates and swimming speeds than stage IVs from the other three treatments. Together these results suggest that projected end-century warming will have greater adverse effects than increased pCO2 on larval survival, and changing pCO2 may have a complex effect on larval metabolism and behaviour. Understanding how the most vulnerable life stages of the lobster life cycle respond to climate change is essential in connecting the northward geographic shifts projected by habitat quality models, and the underlying physiological and genetic mechanisms that drive their ecology.

American lobster postlarvae alter gene regulation in response to ocean warming and acidification

“…In contrast, the results of this experiment investigated response on gene expression, and found a greater differential expression of genes under OA stress than temperature stress, alone, and an interactive effect when both stressors were present. The results of this experiment provide compelling evidence that compensatory mechanisms at the cellular level minimize the physiological and morphological changes measured in other studies to p CO 2 effects (Small et al., 2015; Waller et al., 2017) and suggests that postlarvae are more responsive to predicted end‐century levels of elevated p CO 2 than previously assumed. The metabolic cost of these compensatory mechanisms is unknown.…”

“…This study exposed the larval and postlarval American lobster stages to a future climate scenario during the entirety of their planktonic development, and measured gene regulatory response within its final stage. The design of this study is similar in rearing methodology, treatment conditions, and exposure time to earlier studies that looked at the physiological response of the whole animal (e.g., growth rates, respiration rates, and swimming speed; Small et al., 2015; Waller et al., 2017). The results of those studies generally found little effect of OA relative to responses to temperature.…”

“…Results from physiological studies on larval and early juvenile Homarus congeners suggest a range of responses to end‐century acidification and warming as joint stressors (Agnalt et al., 2013; Keppel et al., 2012; Menu‐Courey et al., 2019; Rato et al., 2017; Ries et al., 2009; Small et al., 2015; Waller et al., 2017). Elevated temperature and p CO 2 can interact to cause changes in behavior, carapace length, carbon content, and development time; however, reports are conflicting in some cases (Small et al., 2015; Waller et al., 2017). The few studies to date that have tested thermal and p CO 2 effects together under similar experimental designs suggest that larval or postlarval physiological and behavioral response to predicted end‐century warming may be greater than that of p CO 2 alone (Agnalt et al., 2013; Small et al., 2015; Waller et al., 2017).…”

“…Elevated temperature and p CO 2 can interact to cause changes in behavior, carapace length, carbon content, and development time; however, reports are conflicting in some cases (Small et al., 2015; Waller et al., 2017). The few studies to date that have tested thermal and p CO 2 effects together under similar experimental designs suggest that larval or postlarval physiological and behavioral response to predicted end‐century warming may be greater than that of p CO 2 alone (Agnalt et al., 2013; Small et al., 2015; Waller et al., 2017).…”

Regulation of gene expression is associated with tolerance of the Arctic copepod Calanus glacialis to CO2‐acidified sea water

“…show higher swimming speeds at low pH (Waller, Wahle, Mcveigh, & Fields, 2016). Actinomyosin ATPase is a considerable component of the cellular energy budget (Rolfe & Brown, 1997).…”