A new bio-bay: Bioluminescence in the Humacao Natural Reserve, Puerto Rico

Background/Question/Methods

Rising sea level will cause salt-water intrusion in coastal areas affecting coastal wetland ecology.  In the Humacao Natural Reserve in Puerto Rico (HNR) salt water intrusion has been accelerated by a man-made channel that connects the HNR coastal lagoons to the Caribbean sea.  An unexpected outcome of this salt-water intrusion was the introduction of bioluminescent dinoflagellate that when concentrated in high densities produce the phenomenon.  With this research we will try to understand how the  salt-water intrusion caused by the construction of the channel is affecting the lagoon salinity regime and the recently observed bioluminescence events.  Our specific questions are: 1) How much has the salinity of the lagoons changed in the HNR, and 2) is there a relation between the bioluminescence events and the salinity gradient in the HNR lagoon system.

For this, we will take water samples  throughout the two HNR lagoon subsystems and compare the population dynamics of bioluminescent dinoflagellate along a salinity gradient that runs through the linear series of the lagoon subsystems.  Will examine: 1) bioluminescent dinoflagellate densities along sampling points in a salinity gradient, 2) physical parameters of the water column (depth (m), Secchi transparency (m), water temperature (°C), dissolved oxygen (mg/L), specific conductance (μS/cm), salinity (ppt), pH ).  Research will be conducted for at least 12 months to include samples from the dry season and the wet season.  We expect that bioluminescent dinoflagellate densities will vary through the salinity gradient and changes in the retention time of the lagoon.

Results/Conclusions

Our initial results revealed: 1) The construction of the channel caused a drastic increase in salinity since 2002,  2)  the organism causing the observed bioluminescence is not Pyrodinium bahamense as previously thought (has not yet been found in substantial numbers to produce bioluminescence), 3) nocturnal observations suggest that bioluminescence intensity is related to the dry season. 4) salinity averages 24 ppt at all water depths in the Mandri lagoons,  (low  salinity values for P. bahamense bioluminescent activity). Following these results, research is now focused on the taxonomic study of highly abundant dinoflagellates (e.g. Gonyaulax sp.) and continuing measurements of lagoon profile characteristics.