IADO   05364
INSTITUTO ARGENTINO DE OCEANOGRAFIA
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Microzooplankton as an important trophic modulator of phytoplankton production in a highly turbid and eutrophic estuary in South America
Autor/es:
LÓPEZ ABBATE M. C.; BARRÍA DE CAO, M. S.; GUINDER V. A.; PETTIGROSSO, R. E.; HOFFMEYER M. S.
Lugar:
Figueira da Foz, Portugal
Reunión:
Simposio; Estuarine Coastal Sciencies Association 47 (ECSA 47); 2010
Institución organizadora:
Coastal and Estuarine Research Federation
Resumen:
Estuaries are productive
areas of the sea and are crucial points for the development of diverse
human activities. This poses potential impacts for those ecosystems,
such as nutrient enrichment that generally leads to changes in the
dynamics of local food webs. The Bahía Blanca Estuary (BBE) is a highly
turbid and eutrophic environment that holds a rich biological
community. The microzooplankton has been perceived as highly abundant
and mainly represented by tintinnids and aloricate ciliates. Thus, it
is expected that the microzooplankton plays a key role in the control
of phytoplankton standing crop in the estuary. Here, we estimated the
grazing impact of microzooplankton trough the dilution technique, in
two areas of the BBE with different nutrient loading and during
contrasting seasons as for hydrographic conditions and chlorophyll-a
concentration; winter and spring. The sampling stations were located in
the inner-intermediate area of the estuary; the station with high
nutrient loading (HN) was severely affected by the main city sewage
discharge and the other station (LN) was located in a less affected
tidal channel with significant lower nutrient concentrations.
Phytoplankton was always dominated by small diatoms and showed higher
biomass during winter. In the HN station, the phytoplankton growing
rate (k) was higher than in the LN station in both seasons. The
microzooplankton grazing rates (g) were moderate to high (ranged
between 1.4 0.7 d-1) with maximum values in HN, and
followed phytoplankton growth. Conversely, the consumer diversity tended
to be lower at HN, probably related to extremely high nutrient levels
that might affect the development of some protists. The grazing rates
were comparable with those found in other productive temperate
estuaries worldwide. Our results showed that microzooplakton represents
an important step in the trophic web in the BBE, presenting
significant grazing rates on phytoplankton standing crop during winter
and spring. Further detailed studies on nutrient ratios dynamics,
species-specific interactions and grazing pressure should be carried out
to disentangle direct and indirect effects of microzooplankton grazing
on phytoplankton structure and their potential cascading effects
throughout the pelagic food web.