SALINITY INFLUENCES BODY-WEIGHT QUANTIFICATION IN THE SCYPHOMEDUSA AURELIA-AURITA - IMPORTANT IMPLICATIONS FOR BODY-WEIGHT DETERMINATION INGELATINOUS ZOOPLANKTON

Comparisons are made between bell diameter:weights (wet, dry, ash-free dry, ash and elemental) relationships for the scyphomedusa Aurelia au rita (L.). There are significant differences in the relationships betw een bell diameter and dry, ash-free dry and ash weights at different s alinities, with these weights increasing as the ambient salinity incre ases. These trends are attributable to differences in the quantity of both bound water (i.e. 'water of hydration') and ash content, both of which vary with the size of medusae. Dry, ash-free dry and ash weights change rapidly as the salinity of an individual's environment alters, and these changes are associated with changes in the individual's buo yancy. Unless salinity effects are appropriately considered, significa nt errors may arise in the quantification of the biomass, production, and other weight-dependent measurements of A. aurita. Similar errors a rise in other gelatinous organisms, and studies of such groups must ma ke allowances for these effects.