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Rev. biol. mar. oceanogr. 51(1): 203-208

Research Note

http://dx.doi.org/10.4067/S0718-19572016000100022

 

Comparison of zooxanthellae densities from upside-down jellyfish, Cassiopea xamachana, across coastal habitats of The Bahamas

Elizabeth W. Stoner1,2, Serina S. Sebilian1,3 and Craig A. Layman1,4

1Department of Biological Sciences, Florida International University, 3000 N.E. 151st Street, North Miami, Florida 33181, United States  of America
2Current Address: Loxahatchee River District, 2500 Jupiter Park Drive, Jupiter, FL 33458, USA
3Current Address: Presidio Trust, 1216 Ralston Avenue, San Francisco, CA 94129, USA
4Current Address: Department of Applied Ecology, North Carolina State University, Raleigh, NC 27695, USA

emailButton  betsy.stoner18@gmail.com


The southwestern Gulf of California has high-value commercial fisheries; however, there are few studies of the taxonomic diversity of fish in this area. Surveys of taxonomic diversity of the fish assemblage at 8 localities near the shore of Bahía de La Paz were undertaken from March 2002 to April 2003. Seasonal changes in diversity of rocky reef fish were analyzed, including taxonomic distance among fish species, using the alpha, alpha average, beta, and gamma diversity indices, the taxonomic distinctness index (TD D*), and the average taxonomic distinctness index (AvTD D+). Submarine visual censuses were carried out along 48 transects measuring 100 × 5 m (500 m2) at 5 m average depth from 09:00-16:00 h. Two seasons were studied: winter with an average temperature of 22.57°C, and summer with an average temperature of 27.09°C. 24,633 fishes, belonging to 92 species and 67 genera were recorded. According to the alpha average, beta, and gamma diversity indices, August had the highest diversity (19.5, 40.5, and 60 species, respectively), and December had the lowest diversity (20.6, 27.4, and 48 species, respectively). Spatial analysis of TD and AvTD were not significantly different, and analysis by season of these indices was not significant different. Greater anthropogenic impact would cause differences in TD and AvTD found at El Guano compared with other locations.
Anthropogenic disturbances may drive jellyfish blooms, and previous studies have suggested this is the case for upside-down jellyfish (Cassiopea xamachana). Cassiopea were found to have higher mean zooxanthellae densities in human-impacted areas on Abaco Island, The Bahamas, suggesting that nutrient loading in impacted sites may be one factor driving zooxanthellate jellyfish blooms. Gut contents from Cassiopea medusae were positively correlated to zooxanthellae densities, indicating that heterotrophically-derived nutrition may be an important factor in facilitating increased zooxanthellae population densities. Understanding the mechanisms driving jellyfish blooms is crucial for developing effective management strategies in impacted coastal ecosystems.

Key words: Benthic, facilitation, human impacts, heterotrophy, mutualism

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