INVESTIGADORES
GUINDER Valeria Ana
congresos y reuniones científicas
Título:
Long-term decreasing trend and seasonal shift in the abundance of Thalassiosira curviseriata in the Bahía Blanca Estuary, Argentina
Autor/es:
GUINDER V. A.; POPOVICH C. A; FREIJE R. H.; MARCOVECCHIO J. E.
Lugar:
Mar del PLata
Reunión:
Congreso; The changing coastal and estuarine environment. A comparative approach; 2012
Institución organizadora:
UNMDP
Resumen:
The
monitoring of phytoplankton structure and composition is an accurate tool to
track environmental changes in coastal ecosystems. We present here the
long-term (1978-2008) variability in the abundance of the diatom Thalassiosira curviseriata Takano 1981, a
key phytoplankton species in the Bahía Blanca Estuary (38º45´S, 62º20´W),
Argentina, in relation to modifications in the pelagic conditions. For more
than 20 years, 1978-2002, T. curviseriata
was present throughout the annual cycle and has been a recurrent blooming
species in winter-early spring. The maximal densities were always in winter
(under a temperature range of 5-10 °C), over 1 x 106 cells L-1
(up to 12.7 x 106 cells L-1 in 1992), accounting for 60 -
96 % of the total phytoplankton abundance. In the last years (2003, 2006-2008),
the population of T. curviseriata has
significantly decreased in winter, with abundances lower than 0.8 x 106 cells L-1 in
2003 and 0.4 x 106 cells L-1
during 2006-2008. Moreover, it was not present all year-round and showed abundance
peaks in spring and summer (up to 0.3 x106 cells L-1). Empirical
studies of T. curviseriata isolated
from the Bahía Blanca Estuary allowed characterize this species as eurythermal
(5-20 ° C) and euryhaline (25 - 40 PSU) adapted to relatively low light
intensities (growth became saturated between 70-80 µmol m-2 s-1
and inhibited at 150 µmol m-2 s-1). The
modifications in water temperature, turbidity and pelagic trophodynamics observed
over the past three decades in the Bahía Blanca Estuary seem to be the driving
factors of T. curviseriata decrease
and seasonal shift. We discuss potential niche modifications, ecological traits
and species-specific interactions implicated in the exclusion of T. curviseriata from the winter period
in this estuarine ecosystem.