Cianobacterias en la Bahia de Mayaguez: Abundancia, distribucion y su relacion con las propiedades bio-opticas

Mayaguez Bay is a complex environment with variety of physical and biological processes influencing the spatial and temporal variability of bio-optical properties. This research focused on the role of cyanobacteria because phytoplankton is a key component of the large bio-optical variability in marine environments. Their distribution was assessed by traditional and molecular techniques. The Bay was sampled during five cruises from July to December of 2005 in coastal stations (A1, G1, Y1, AAA) and oceanic stations (A2, G2). The abundance of cyanobacteria was low, representing only 3.6% of the total phytoplankton. Diatoms were the dominant group during the study period. Abundance of cyanobacteria and diatoms showed spatial and temporal changes, when rivers input were high. Diatoms abundance and Chlorophyll-a were higher at coastal stations than at oceanic stations. These two parameters were also consistently high at G1 and Y1 stations. A negative relationships was found between cyanobacteria abundance and Chlorophyll-a, whereas diatoms were positively correlated with Chlorophyll-a, indicating that this group contributes most to the Chlorophyll-a concentration in Mayaguez Bay. High temporal and spatial variability was found for all the bio-optical properties. The absorption, backscattering and attenuation coefficients of station G1 were the highest. In oceanic stations these coefficients were low. A clear relationship between cyanobacteria abundance and bio-optical properties could not be established. In contrast, diatoms abundance and Chlorophyll-a were positively correlated with bio-optical properties. Therefore, changes in diatoms abundance are very important for the optical variability of Mayaguez Bay. Spatial and temporal changes in the community structure of cyanobacteria were found by analyzing Terminal Restriction Fragment Length Polymorphism (T-RFLP) of 16S rDNA cyanobacteria. Clones libraries revealed that the cyanobacteria community was also composed of picocyanobacteria.