Cardiovascular responses to increased temperature and lower pH for six cold water Opisthobranch species.

Increasing sea surface temperatures and ocean acidification continue to threaten marine life globally, especially in coastal waters where effects are often exacerbated. Individually, temperature and acidification negatively affect marine organisms, but interactive effects, vary depending on phylum and life cycle stage. Opisthobranch sea slugs, having short and complex life cycles, were studied for cardiac response to increasing temperature and to interactive effects of temperature and pH. Six cold-water, cosmopolitan species (Aeolidia papillosa, Cuthona gymnota, Dendronotus frondosus, Flabellina verrucosa, Onchidoris bilamellata , and Placida dendritica) common in the Gulf of Maine were selected. To determine response to temperature, heartbeats of test animals starting at 4 °C were recorded at increasing temperature intervals of 4 °C, until they slowed or ceased. Interactive effects were examined at pH 8 (control) and pH 7 coincident with temperature increases (4o to 16 °C). Overall, upper pejus temperatures tested ranged from 16o to 28 °C, with the largest species having the lowest temperature threshold and smallest having the highest. Although interactive effects were not significant, the negative synergistic effect of suppressed heart rate across temperatures was significant for three species and apparent in two others. As significant predators of sessile prey, especially within fouling communities, environmental impacts on sea slugs have the potential to alter both community structure and prey abundance within their environment, potentially reflecting larger implications affecting the biodiversity and abundance of prey populations within their environment. • Heart rates of all species positively correlated to temperature increase. • Q 10 for all species dropped to ∼1 at upper temperature thresholds (16o-28 °C). • papillosa & D. frondosus are already experiencing pejus temperatures in the GOM. • No interactive effects found, but a negative synergistic effect existed for some. [ABSTRACT FROM AUTHOR]

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