Proximate and elemental composition of gelatinous zooplankton from the Southern Ocean

We have analysed the proximate composition and elemental (C,H,N) composition of eight gelatinous zooplankton from the Southern Ocean (two ctenophores, one anthomedusan, two siphonophorcs, one scyphozoan, one annelid and one salp). In all species except the annelid Tomopteris, water contents were very high and the dry matter contained significant residual water (estimated to be at least 10%). The dry matter had a very high ash content (60–73%). These data are typical of gelatinous zooplankton. The major organic component was protein (0.32−0.83% wet mass, equivalent to 7.5–17.0% dry mass). Lipid was the next most abundant component (0.08−0.22% wet mass; 1.8−4.6% dry mass), similar to levels reported previously for Southern Ocean gelatinous zooplankton but lower than typical Arctic values. Measured carbohydrate contents were 0.02−0.08% wet mass (0.4−1.7% dry mass), although stoichiometric considerations suggested the presence of an unmeasured or underestimated non-protein nitrogenous component which may be either a glycoprotein or an amino-polysaccharide. Tomopteris was intermediate in composition between typical gelatinous species and non-gelatinous species such as crustaceans. Unresolved difficulties over the residual water content and the nature of the unmeasured organic component mean that valid energy contents can be calculated neither from proximate composition nor carbon content.