CONTROLLING FACTORS ON THE RESUSPENSION OF COPEPOD EGGS IN SALT-MARSH AND TIDAL FLATS OF THE BAHIA BLANCA ESTUARY, ARGENTINA

LUCAS M. MOLINA, MAURICIO M. PERILLO, DANIEL E. PEREZ, MÓNICA S. HOFFMEYER, GERARDO M. E. PERILLO

Bahía Blanca, Argentina

Simposio; ECSA 44 Symposium: Science and management of estuaries and coasts: A tale of two hemispheres; 2008

Dominant zooplancktonic species play a key role on the coastal ecosystems energy flow. Certain copepods have resting eggs as a reproductive strategy. They are not only a source of recruitment, but also way to survive unfavorable periods. Resting eggs can sink in the bottom waiting for favorable conditions. However, eggs will only hatch after resuspension into the water column. The objective of this study was to investigate the possible role of tidal flat and Spartina alterniflora saltmarsh environments as a source and sink of copepod eggs, as well as the function of wind waves and tidal currents on their re-suspension. Water velocities were measured employing an Acoustic Doppler Velocimeter (ADV) and water samples were taken by pumping at several times during the tidal flood in both, a tidal flat and a nearby saltmarsh. The three components of the flow were filtered and spectrally analyzed. Suspended sediment and copepod eggs concentrations were also estimated. Bottom shear stress at the study site was induced by both tidal currents 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, with higher 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.Keywords: copepod eggs, tidal flats, saltmarshes, shear stress, ADV