Distribution and ecology of <i>Pseudo-nitzschia</i> species (Bacillariophyceae) in surface waters of the Weddell Sea (Antarctica)

The distribution of six Pseudo-nitzschia species and their relationship with environmental conditions were studied for the first time in a vast zone of the Weddell Sea (∼61–77°S, Antarctica). Both qualitative and quantitative phytoplankton samples, collected during summer 2004, were examined using light and scanning electron microscopy. Phytoplankton abundance and composition showed great variability along our study area. Diatoms were the most conspicuous phytoplankton group in the northern area while small flagellates were generally dominant in the southern stations. The genus Pseudo-nitzschia was broadly distributed and significantly contributed to total diatom densities. A marked contrast in Pseudo-nitzschia species distribution was observed in three main zones divided by the Weddell Front (WF) and the Antarctic Slope Front (ASF). P. subcurvata and P. turgiduloides were the most abundant species in the neritic Weddell Sea zone, south of the ASF, mainly near the ice-edge in shallower waters and in conditions of long photoperiod. In contrast, P. prolongatoides and P. lineola dominated north of the ASF; the first was associated with deeper and nutrient-rich waters whereas the latter showed a weak relation with environmental variables examined. Finally, P. turgidula and P. heimii were mostly observed in the Weddell–Scotia Confluence Zone in the warmest and far from ice covered waters, north of the WF. A brief morphological Pseudo-nitzschia species description is given in the Appendix, including morphometrics and pictures.Facultad de Ciencias Naturales y Muse

COMPARISON OF BATHYMETRIC FEATURES DETECTED BY ERS2 SAR AND LANDSAT TM DATA OVER SAN MAT\ucdAS GULF, ARGENTINA

It is well known that Synthetic Aperture Radar (SAR) is capable of imaging bathymetric features by detecting changes in sea surface roughness associated with bathymetry-induced surface current modulations. The high dynamic range of LANDSAT Thematic Mapper (TM) and Enhanced TM+ (ETM+) sensors allow them to observe oceanic surfaces affected by solar specular reflection, or sun glint, without being saturated. This ability allows the imaging of sea surface roughness patterns in the sun glint affected area that are associated with surface current changes such as those produced by bathymetric features. ERS SAR and LANDSAT TM/ETM+ images obtained over the San Matías Gulf, Argentina during similar tidal current conditions are compared and the surface signature generated by the interaction of the tidal current with the bottom topography analyzed. Each type of sensor presents advantages and limitations to the observation of bottom features due to the way each one detects sea surface roughness. Still, when sun glint is present, TM/ETM+ and SAR show similar bathymetric patterns under the same tidal conditions. While both sensors provide consistent information over significant bathymetry features, increased differences in the detection is observed over weaker feature

Editorial for the Special Issue “Remote Sensing in Coastal Zone Monitoring and Management—How Can Remote Sensing Challenge the Broad Spectrum of Temporal and Spatial Scales in Coastal Zone Dynamic?”

Coastal zones are sensitive areas responding at various scales (events to long-term trends) where the monitoring and management of physico-chemical, biological, morphological processes, and fluxes are highly challenging [...

An empirical remote sensing algorithm for retrieving total suspended matter in a large estuarine region

The Río de la Plata is a large, shallow estuary located at approximately 35°S and flowing into the southwestern Atlantic Ocean. It carries a high amount of nutrients and suspended particulate matter, both organic and inorganic, to the adjacent shelf waters and is considered among the most turbid estuarine systems in the world. Knowledge of the concentration and spatial and temporal variability of these materials is critical for any biological study in the Río de la Plata. In this work, the relationship between suspended particulate matter and turbidity is empirically established in order to derive suspended particulate matter maps from satellite data (MODIS-Aqua) for the Río de la Plata region. A strong correlation between suspended particulate matter and turbidity was found (Pearson correlation coefficient =0.91) and the linear regression (slope =0.76 and intercepts =12.78, R2=0.83) explained 83% of the variance. The validation of the empirical algorithm, using co-located and coincident satellite and in situ measurements, showed good results with a low mean absolute error (14.60%) and a small and positive bias (3.04%), indicating that the estimated suspended particulate matter values tend to slightly overestimate the field values