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Spatial and temporal phytoplankton distribution in the Gulf of Cariaco, Sucre State, Venezuela, February 2014 - January 2015

Abstract:

Coa temporal bottlesstal phytoplankton(5 distribution L) in sevenisstations of affected phytoplankton betweenby naturalFebruary in the and Gulf anthropic2014 of and Cariaco, processes.January Sucre 2015.To state, analyzeTransparency was evaluated. the influence(m) Samples salinityof some(UPS) (0-10 of these m) temperature were processes collected (° C)the with chlorophyllspatial Niskin and concentration a (mg m-3), and phytoplankton abundance (org mL-1) were measured. A nonparametric analysis of variance and multivariate methods (PCA, CCA, and nMDS) were used to analyze the results. The 0 - 10 m stratum was homogeneous with respect to all variables except temperature which ranged from 20.1 to 29.1 °C (March and October, respectively). Temporally, the variables were heterogeneous. Biomass fluctuated between undetectable (ND) and 17.5 mg m-3 (December and March). While microalgal abundance oscillated between 0.24 and 1.85 x 103 org mL-1 (April and February). The community was dominated by diatoms, nanoflagellates, and coccolithophorids. The first two groups were associated with turbulent, nutrient-rich waters. The nMDS separated the community into the three periods previously described for the region. Likewise, the CCA detected that wind speed and temperature were the most influential variables on the phytoplankton community during upwelling and relaxation period, respectively. In the transition period, none of the variables studied affected the community. This is the first time that coccolithophores are reported as part of the dominant flora in the Gulf of Cariaco. This change suggests modifications in the oceanographic conditions of the study area.