La condición ecológica de la bahía de Tumaco (Pacífico colombiano): evaluación de la calidad del agua y del fitoplancton

Abstract

The Bay of Tumaco has a strong interaction between waters discharged from different rivers, the rivers beds are characterized by being short but mighty, and the waters of oceanic origin projecting towards the coast, a situation that creates permanent variability of the physicochemical conditions that may be accentuated or attenuated according to the tidal cycle and the climatic seasons. Under these considerations, we characterized the phytoplankton community of the Bay waters in high and low tide in two seasons of the year and related them to physicochemical variables to assess the ecological condition of the Bay. Sampling was conducted in April (rainy season) and August (dry season) in nine stations. From the analysis of species composition and abundance, using a non-metric multidimensional scaling (nMDS), there were significant differences in the composition and abundance between the two seasons of the year (p = 0.001), showing less abundance, more species richness, uniformity and diversity in the rainy season compared to the dry season. Seasonal fluctuations in SST, salinity, chlorophyll a, nitrites and nitrates (Spearman's rank correlation coefficient: 0.545, p = 0.001), were associated with biological pattern found. These conditions favored the growth of Rhizosolenia imbricata, Odontella sinensis, Guinardia striata, Scrippsiella sp. and Protoperidinium sp. in rainy season and Coscinodiscus Granni, Leptocylindricus danicus, Thalassiosira sp., Astrionella japónica and Skeletonema costatum in the dry season. Comparison with other tropical estuaries physicochemical characteristics and the community structure it can be inferred that the ecological condition of the Bay is good, but is vulnerable to changes in its environmental conditions. It can be inferred that this estuary has the ability, at least in short spatial and temporal scales, to assimilate nutrient inputs, so algal blooms are rare.