Ammonium excretion by the ophiuridOphiothrix fragilis as a function of season and tide |
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Authors: | D. Davoult F. Gounin M. -A. Janquin |
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Affiliation: | (1) Station Marine, URA 1363 du CNRS, B.P. 80, F-62930 Wimereux, France |
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Abstract: | Ammonium excretion of a dense population (~1 500 individuals m–2) of the ophiuridOphiothrix fragilis (Abildgaard) was measured in the Dover Straits (French coast) between May 1989 and March 1990: the excretion rate varied from 4.8 µg N g–1 dry wt h–1 in November to 12.8 µg N g–1 dry wt h–1 in June. Mean individual ammonium excretion,E, wasE=0.019t +1.26 (whereE=µg N individual–1 andt=time in min;r=0.80;N=81). Variations in the ammonium excretion rate during a tidal cycle appeared to arise from variations in the duration of the suspension-feeding activity ofO. fragilis, which was governed by the strength of the tidal current. During short-term starvation, excretion was low (E=0.009t+1.47;r=0.91;N=17), increasing with increasing length of starvation [E=4.62lnt–2.5;r=0.95;N=17], as observed for other echinoderms; this could be due to catabolism of tissue. The daily ammonia flux from thisO. fragilis population to the water column was estimated at 41 mg N m–2 d–1. |
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