MEPS 142:203-214 (1996)  -  doi:10.3354/meps142203

Somatic and germinal growth of the infaunal brittle stars Amphiura filiformis and A. chiajei in response to organic enrichment

Sköld M, Gunnarsson JSG

The effects of a short-term organic enrichment on growth of the 2 brittle stars Amphiura filiformis (O. F. Müller) and Amphiura chiajei (Forbes) were studied in undisturbed sediment cores obtained from a coastal and an offshore site of the Kattegat and Skagerrak, and then maintained in the laboratory as microcosms. Growth was measured as arm regeneration (somatic growth) and oocyte size (germinal growth). Macrofaunal abundance and biomass were higher in the offshore sediment compared to the coastal site. Organic enrichment was studied by adding concentrated phytoplankton (diatoms) to mimic the sedimentation pulse of a spring bloom in terms of quality and quantity. The experiment was run for 2.5 mo (April to June 1993). Somatic growth of A. filiformis increased in response to the phytoplankton addition in the coastal site sediment but not in the offshore site sediment. Arm regeneration in A. chiajei increased in both sediments in response to the food pulse. A positive correlation between regenerated arm length and oocyte size was obtained for both species. The results show that the brittle stars were capable of increasing their growth and gonad development in response to the short-term organic enrichment. The difference between sites also suggests negatively density dependent growth indicative of space or food competition in the densely populated offshore sediment.

Regeneration · Oocyte size · Echinodermata · Ophiuroidea · Eutrophication · Kattegat · Skagerrak · Microcosm

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