Respiration rates of dominant hydromedusae in the North Inlet tidal estuary during winter and summer

The objective of this study was to quantify the respiratoryrequirements and oxygen consumption rates for seasonal hydromedusaepopulations in the North Inlet estuary, Georgetown, SC, USA.Respiration rates were determined for hydromedusae collectedin January 2006, 2007 and July 2006 using microrespirometry.The numerically dominant gelatinous predators were Nemopsisbachei (January 2006 and 2007) and Bougainvillia muscus (July2006). Seasonal oxygen consumption rates were low (0.80–1.27µmol O₂ g^–1 h^–1). Q₁₀ values were high duringJanuary 2006 and July 2006 (4.7), but low during January 2007(0.5), suggesting hydromedusae were sensitive to the exposuretemperatures (7–34°C) in this study and well adaptedto the temperature range encountered in this estuary. Moreover,the oxygen consumption rates during July 2006 showed significantdifferences between the two species. The allometric relationshipbetween respiration rate and hydromedusae weight differed seasonally.Our findings suggest hydromedusae can persist in hypoxic conditionsand may partially explain the frequently observed increase inthese cnidarians under conditions of low dissolved oxygen concentrations.