Short-term variability of metabolic and digestive enzyme activity in naturally occurring populations of adult copepod Acartia clausi

Changes in whole animal activity of two enzymes that have been used historically as proxies of intermediary metabolism (ETS, GDH) and of three digestive enzymes (laminarinase, amylase, trypsin) were measured in adult Acartia clausi copepods collected pre-, during, and post-spring phytoplankton bloom in a region of semi-enclosed circulation within the Bay of Villefranche. About once per week during a 13-week period from mid-March to mid-June, the bay was submitted to strong `mistral' wind events known to vertically mix the water column of the inner bay and so dilute the phytoplankton standing stocks. Our data show a correlation between the incidence of these mistral wind events and temporal variations in the metabolic and digestive enzyme activity of sampled animals. These results may reflect wind-induced, short-term dilutions of copepod food supply: enzyme generally declined 1-2 days after each wind event, and then increased again 2-4 days later to match or exceed pre-event activity levels. Spectral analysis indicated that 38-64% of the variability in activity of each of the five enzymes occurred with periods of 7-19 days. On the other hand, the fact that differences in activity among each of the five enzymes were not always in phase suggest that the pathways that exist for the regulation of digestion are different from those mediating intermediary metabolism. Ratios of ETS and GDH activity to whole animal respiration and ammonia excretion measured in 5-9 hour laboratory incubations showed little variation between early spring, late spring, early summer, or summer (cv = 20% for ETS: Resp and 28% for GDH:Excr). The ratio of oxygen consumption relative to ammonium excretion (O:N ratio = 11 +/- 4 by atoms) indicated that whole animal intermediary metabolism was dominated by protein catabolism throughout the 3-month period of field collection

Biomarqueurs lipidiques, réseau trophique pélagique et écologie alimentaire des oiseaux de mer Procellariiformes

PARIS-BIUSJ-Thèses (751052125) / SudocBANYULS/MER-Observ.Océanol. (660162201) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

Stratégies reproductives des copépodes subantarctiques dominant l'écosystème pélagique côtier des Iles Kerguelen (Implications écologiques)

AIX-MARSEILLE2-BU Sci.Luminy (130552106) / SudocBANYULS/MER-Observ.Océanol. (660162201) / SudocSudocFranceF