Deciphering Phosphorescent Bay: New Approaches towards the Understanding of this Unique Ecosystem

Deciphering Phosphorescent Bay: New Approaches towards the Understanding of this Unique Ecosystem April 15, 2015 Puerto Rico Sea Grant Award/Project number: R–101–1–12 Time Period: February 1, 2012 – January 31, 2015 PI - Brenda M. Soler Figueroa, PhD Candidate Department of Marine Science, University of Puerto Rico, Mayagüez Co-PI - Ernesto Otero Morales, PhD Professor Department of Marine Science, University of Puerto Rico, Mayagüez Collaborator - Juan O. Gonzalez-Lopez, PhD Candidate Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Indiana EXECUTIVE SUMMARY Summary of impacts and contributions Objectives - The aim of this study was to identify the links between the environmental and meteorological conditions and the patterns of variability of Pyrodinium bahamense and Ceratium furca and the bioluminescence levels (BL) at Bahía Fosforescente (BF; Phosphorescent Bay). Objective 1 – Determine the daily, spatial and seasonal variability of P. bahamense and C. furca. This objective was achieved. Results indicated that seasons alone accounted for about 48% of the total variation in the dinoflagellate composition, while daily and spatial variation only accounted for ca. 10% of the total variation. Pyrodinium bahamense was the numerically dominant dinoflagellate during the wet season and a shift towards the dominance of C. furca were found during the dry season. Objective 2 - Identify the environmental factors that may drive the fluctuations of species. This objective has been meet. A multivariate analysis showed that seasonal differences in dinoflagellates composition were better explained by salinity, dissolved organic matter fluorescence, pH and silicates, environmental variables that are significantly influenced by different precipitation extremes. Thus, results indicate that the alternations in the abundance of P. bahamense and C. furca are intimately linked to seasons, the local weather and the resulting changes in the environmental conditions. Objective 3 - Examine the response of P. bahamense and C. furca to different nutrient enrichments. This objective was waived and changed to – a) Determine the actual bioluminescence levels (BL) at BF and evaluate the putative declining bioluminescence trend and b) Identify the role of different environmental conditions on BL. The seasonal trend in the dinoflagellate composition, described in Objective 1, was also reflected in the bioluminescence. High levels characterized the wet season and strongly correlated with the high cell densities of P. bahamense. During the dry season, dramatic decreases in P. bahamense populations resulted in simultaneous reductions in BL. This suggests that environmental changes exerted by different meteorological conditions are linked to variations in BL by a modulation in dinoflagellate composition. Objective 4 - Investigate the influence of the water circulation pattern in relation with the spatial and temporal distribution of the organisms. A detailed measurement of the water levels, currents and bottom temperature was conducted during November 2012 and March 2013. The analysis showed a predominantly two-layer circulation with currents coupled with both the daily temperature cycle and the winds. In particular the dominant periods of the