Marine food chains: Effect of phytoplankters and depth on the organ lipids of the sea scallop Placopecten magellanicus (Gmelin) and of intertidal invertebrates on the fat reserves of shorebirds.

• Main Author: Napolitano, Guillermo Eduardo.
• Other Authors: Ph.D.
• Format: Text
• Language: English
• Published: Dalhousie University 2014
• Subjects: Biology; Ecology; Animal Physiology; Environmental Sciences; Canada; Newfoundland
• Online Access: http://hdl.handle.net/10222/55246

Marine biogenic lipids, traditionally regarded as mere energy reserves, are now acknowledged to be associated with many important physiological processes. This work presents a comprehensive study of the occurrence and anatomical distribution of lipids in sea scallops Placopecten magellanicus from Georges Bank and southeastern Newfoundland as related to biological and environmental information. Analyses of the major organs in scallops presented different and characteristic lipid profiles. Lipid-rich organs exhibited dramatic biochemical changes associated with reproduction and feeding. Some fatty acids (16:1n-7 and 18:1n-9) were useful indicators of interorgan lipid transport; others (e.g. 20:5n-3, 22:6n-3) were related to fluctuations in water temperature or food supply on Georges Bank. Previous studies have demonstrated that less favourable conditions associated with deeper waters produced slower growth and reduced fecundity in scallops. Lipids of two populations of sea scallops living at different depths in southeastern Newfoundland were used to assess egg quality. It was demonstrated that eggs produced at 31 m had the same lipid reserves (60% of total lipids) as those produced at 10 m. Eggs from the two populations, thus, should be capable of similar developmental performances. The analyses of sterols in captive and wild scallops always showed a uniform anatomical distribution. This is assumed to be internally controlled for proper cellular function. Experimental evidence showed that the even anatomical distribution of sterols could be disrupted in apparently healthy animals by rapid uptake of exogenous phytosterols by the digestive gland and male gonad. This study was extended to lipids and lipophilic pollutants in other invertebrates of local ecological interest: the amphipod Corophium volutator and the polychaete Nereis diversicolor of the Bay of Fundy. Low levels of chlorinated pollutants were detected in these invertebrates ($<$0.002 ppm to 0.0165 ppm of lipid), and in three species of shorebirds feeding on them on mudflats of the Bay of Fundy (0.39 to 1.64 ppm of lipid). Biogenic lipids and hydrocarbons were used to document trophic relationships among the different components of this shorebird food resource. These results contributed to the establishment of a valuable baseline level of reference for monitoring the pollution status of this marine coastal environment. Thesis (Ph.D.)--Dalhousie University (Canada), 1991.