Controlling factors on the resuspension of copepod eggs in salt-marsh and tidal flats of the Bahia Blanca Estuary, Argentina

MOLINA, L.M.; PERILLO, M.M.; PEREZ, D.E.; HOFFMEYER, M.S.; PERILLO, G.M.E.

Bahía Blanca

Congreso; ECSA 44: SCIENCE AND MANAGEMENT OF ESTUARIES AND COASTS: A TALE OF TWO HEMISPHERES; 2008

Estuarine Coastal Science Association-Instituto Argentino de Oceanografía

Dominant zooplancktonic species play a key role on the coastal ecosystems energy flow. Certain copepods have resting eggs areproductive strategy. They are not only a source of recruitment, but also way to survive unfavorable periods. Resting eggs can sinkin the bottom waiting for favorable conditions. However, eggs will only hatch after resuspension into the water column. The objectiveof this study was to investigate the possible role of tidal flat and Spartina alterniflora saltmarsh environments as a source and sink ofcopepod eggs, as well as the function of wind waves and tidal currents on their re-suspension. Water velocities were measuredemploying an Acoustic Doppler Velocimeter (ADV) and water samples were taken by pumping at several times during the tidal floodin both, a tidal flat and a nearby saltmarsh. The three components of the flow were filtered and spectrally analyzed. Suspendedsediment and copepod eggs concentrations were also estimated. Bottom shear stress at the study site was induced by both tidalcurrents and wind waves, being the effects of the waves at least four times greater than the currents shear stress in the tidal flat,and at least one order of magnitude larger at the salt marsh. However, eggs abundance showed the same pattern of variation, withhigher values over the saltmarsh. Our results showed a primary effect of waves on egg and sediment resuspension at both sites.When compared to tidal flats, Spartina alterniflora salt marshes act as the larger sinks, being better egg banks than tidal flats.