Effectiveness of the burglar alarm hypothesis: a comparison between bioluminescent displays in dinoflagellates and abundance of copepods at various depths

The burglar alarm hypothesis states that dinoflagellate bioluminescence is used to avoid predation from copepods by taking an altruistic approach. This study aims to test the effectiveness of the in-situ dinoflagellate defense mechanism in the waters of the western coast of Bonaire, (Dutch Caribbean). According to the burglar alarm hypothesis, areas of higher bioluminescence should have lower abundances of copepods, however there is little evidence supporting this. To analyze the effectiveness of the burglar alarm hypothesis, horizontal tows were used to collect plankton samples at four depths: the surface, 10, 20, and 30 feet. Dinoflagellate bioluminescent display frequency was recorded immediately after collection in a dark room. Copepods and Dinoflagellates were then identified under a compound microscope and abundance was analyzed. Two-way ANOVA tests showed significant relationships between the decreased ratio of copepod to dinoflagellate abundance associated with increased bioluminescence frequency and increased bioluminescence frequency in relation to increased depth. No significant difference was found in bioluminescent displays in comparison with various weather conditions. This study shows that the burglar alarm has positive effects in maintaining dinoflagellate populations. The environment at depth allows for more dinoflagellate bioluminescent displays to occur than at the surface. Implications of light pollution may cause variations in bioluminescence at shallower depths, lessening the effectiveness of the luminescent defense mechanism of dinoflagellates. Comparisons of biolumi-nescence between the areas exposed to light pollution and areas sheltered from ambient light can be used to analyze how the primary trophic level will change with increasing human impacts.

This student research was retrieved from Physis: Journal of Marine Science XIII (Spring 2013)19: 45-52 from CIEE Bonaire.

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