The effects of salinity on the physiology and ecology of the mud-dwelling estuarine animal Corophium volutator (Pallas), a crustacean amphipod, have been investigated. A study of the effects ot salinity on the distribution and abundance of C. volutator on the estuary of the River Ythan, Aberdeenshire, indicates that 2‰ is a critical minimum salinity controlling its distribution. In areas with salinities between 2 and 5‰ C. volutator was present, but in reduced numbers. In areas with salinity greater than 5‰ , the distribution and abundance of C. volutator were controlled by the nature of the substrate; however, in areas with suitable substrates, but where the salinity was below 5‰ , the effects of salinity override the effects of the substrate. Experimental studies indicated that, if supplied with mud, it will survive the salinity range of 2 - 50‰, and without mud, the range 7.5 - 47.5‰. Moulting occurred in salinities of 2.6 - 46‰ , but most frequently in tho range 5 - 20‰ . Growth occurred at a maximum rate in 15.4 o/oo and only slightly slower at 4.4 and 30.6‰ ; but below 4.4‰ the growth rate was progressively reduced. The effects of salinity on the various stages in the life cycle are discussed. Freezing point studies show C. volutator to be a hyperosmotic regulator, having a tissue tolerance range of 13 - 50‰ . The effect of size, sex, feeding and moulting on the freezing point have been investigated. C. volutator was found to produce urine hypoosmotic to the blood when acclimated to low salinities, and isosmotic urine at salinities above 20‰ . Over a range of salinities from 1 - 35‰ , C. volutator was found to maintain Na+, K+,Ca ++,Cl-, more concentrated than the medium, and Mg++ less concentrated. The restricted permeable areas of the cuticle have been localised by silver staining. The oxygen consumption of animals of the same size, at the same level of activity, and at the same temperature, did not differ significantly between animals in different salinities. A salinity preference range of 10 - 30‰ has been demonstrated. Relevant literature on estuarine life, and osmoregulation of crustacea is reviewed. The adaptations of C. volutator to an environment with varying salinity are discussed.

Thesis (Ph. D.)--Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references. / The sinking flux of particles is an important removal mechanism of carbon from the surface ocean as part of the biological pump and can play a role in cycling of other chemical species. This work dealt with improving methods of measuring particle export and measuring export on different scales to assess its spatial variability. First, the assumption of ²³⁸U linearity with salinity, used in the ²³⁸U-²³⁴Th method, was reevaluated using a large sample set over a wide salinity range. Next, neutrally buoyant and surface-tethered sediment traps were compared during a three-year time series in the subtropical Atlantic. This study suggested that previously observed imbalances between carbon stocks and fluxes in this region are not due to undersampling by traps. To assess regional variability of particle export, surface and water-column measurements of ²³⁴Th were combined for the first time to measure fluxes on ~20 km scales. Attempts to relate surface properties to particle export were complicated by the temporal decoupling of production and export. Finally, particle export from ²³⁴Th was measured on transects of the Atlantic Ocean to evaluate basin-scale export variability. High-resolution sampling through the water-column allowed for the identification of unique ²³⁴Th features in the intermediate water column. / by Stephanie Anne Owens. / Ph.D.