Responses of benthic organisms on the deep Antartic continental shelf to a highly seasonal food supply

Galley, Elizabeth Anne (2003) Responses of benthic organisms on the deep Antartic continental shelf to a highly seasonal food supply. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

It was hypothesised that organisms living on the Antarctic continental shelf, west of the Antarctic Peninsula, have reproductive and energetic responses coupled to the seasonal pulse of phytodetritus.

Highly opportunistic reproductive strategies were observed from two species of holothurian, Protelpidia murrayi and Peniagone sp., which were closely tied to the phytodetrital pulse. In Protelpidia murrayi the initiation of gametogenic cycles were clearly linked to the arrival of phytodetritus, and fecundity in Peniagone sp. was also related to the intensity of the pulse. Sterechinus antarcticus exhibited a seasonal gametogenic cycle similar to the shallow congener Sterechinus neumayeri, although the timing of spawning in S. antarcticus was five months later than its shallow water counterpart. The brooding echinoids, Ctenocidaris perrieri and Amphipneustes lorioli, exhibited a continuous gametogenic pattern; however, Amphipneustes lorioli showed a seasonality of recruitment in the brooding pouches. In contrast the asteroid, Psilaster charcoti, which shows a seasonal reproductive cycle in shallow-water, showed no such periodicity on the deep Antarctic continental shelf.

Biochemical composition of body components of the six species of echinoderm indicated a significant difference in composition between male and female gonad tissues for all species. Ovaries contained a much higher proportion of lipid compared to the testes. The ovaries of Protelpidia murrayi indicated a seasonal variation in composition that correlated to the reproductive cycle; highest values of lipid were observed when the ovaries contained mature vitellogenic oocytes. The variation in composition of the gut lining tissue in several species indicated a role as a nutrient storage organ; the tissue had highest energy values during the period of seasonal phytodetrital flux. The pyloric caeca proved to be a dynamic nutrient storage organ that indicated significant variation both among stations and seasons, and was therefore very sensitive to the quality and quantity of food available.

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