Characterization of marine bacteria and its association to population dynamics of <em>Pyrodinium bahamense var. bahamense</em> (L. Plate, 1906) and <em>Ceratium furca</em> (R. Claparède & C. Lachmann, 1859) present in the Laguna Grande (Fajardo, Puerto Rico)

Abstract

Bioluminescent bays are unique and ecologically significant marine ecosystems where the water emits a natural glow due to the presence of bioluminescent organisms like dinoflagellates. In Puerto Rico, these bays hold both ecological and economic importance due to their role in marine ecosystems and their value as tourism destinations.<br /> <br /> In order to evaluate the depth of the ecological biodiversity supported by these unique ecosystems, we evaluated the relationship between marine bacterial diversity and the population dynamics of two dinoflagellates: <em>Pyrodinium bahamense var. bahamense</em> and <em>Ceratium furca</em> in Laguna Grande, a saltwater lagoon in Fajardo, Puerto Rico. From the 42 samples collected by establishing a transect, we performed genomic DNA extractions and amplifications of the V4 region of the 16S rRNA gene. Data analyses included bacterial compositional assessments, Principal Component Analysis (PCA) for beta diversity, and Pearson correlation to test the association between dinoflagellate counts and marine bacteria present. We further examined whether fluctuations in the lagoon's microbiota could account for the seasonal changes in these dinoflagellate species. The analysis revealed significant associations: <em>Epsilonproteobacteria</em>, <em>Synechococcophycideae</em>, and <em>Flavobacteriia</em> were positively correlated with <em>P. bahamense var. bahamense</em>, suggesting a potential mutualistic relationship where these bacteria may contribute to nutrient cycling or other supportive functions. Conversely, <em>C. furca</em> showed strong positive associations with <em>Gammaproteobacteria</em>, <em>Acidimicrobiia</em>, and <em>Thermoplasmata</em>, indicating that these bacterial groups may facilitate <em>C. furca</em> growth through nutrient provision or environmental conditioning.<br /> <br /> Negative correlations were also observed, such as between <em>P. bahamense var. bahamense</em> and <em>Flavobacteriia</em> and between <em>C. furca</em> and <em>Synechococcophycideae</em>, suggesting competitive or inhibitory interactions that could suppress dinoflagellate populations during specific periods. These findings emphasize the critical role of microbial diversity in influencing the ecological dynamics of Laguna Grande, potentially driving the observed population peaks and declines of both dinoflagellate species. The study also demonstrated that while physicochemical parameters like temperature, salinity, and rainfall had some correlation with dinoflagellate counts, the influence of specific bacterial taxa was more pronounced. This highlights the complex interplay between microbial communities and environmental factors in regulating dinoflagellate populations. Although this research significantly enhances our understanding of these interactions, further studies are recommended to explore additional environmental parameters and a broader range of dinoflagellate species. Such research is vital for conserving and managing this bioluminescent lagoon, especially in light of ongoing environmental changes.