Temporal and spatial comparisons of zooplankton abundance and diversity on two Caribbean coral reefs
Climate change is increasing the decline of coral reef health as rising temperatures result in coral bleaching, often leading to death. However, recently increased heterotrophy has been indicated as a potential recovery mechanism for certain corals. Limited research exists for zooplankton communities on coral reefs in recent years. This study investigates the abundance and diversity of these communities to further investigate how heterotrophy aids in recovery from bleaching. It is expected that healthier coral reefs will have zooplankton communities with higher abundance and diversity than stressed coral reefs with higher frequencies of bleaching events.
Zooplankton were collected at both a stressed reef (Florida Keys) and relatively healthy reef (Panama), using tows over the reef during the day and traps set on the substrate at night to include vertical migration. Samples were processed immediately at the time of collection with a neutral red dye used to identify percentages of live plankton in water column. Samples were then preserved in ethanol. This study will provide a nice compliment to a similar study performed in the Florida Keys in 2004, at the same reef, allowing for a comparison of zooplankton communities on a reef exposed to increased bleaching events over the past decade.
The zooplankton community on the Florida Keys reef exhibited a different composition than reported in the original study revealing an increase in overall zooplankton abundance yet, a decrease in diversity. Copepods are the dominant plankton in both studies; however this study shows an increased abundance of zooplankton with few other orders contributing to the diversity, but each with a similar frequency to the copepods. The original study has more orders represented in the community, but none within an order of magnitude of copepod abundance. The healthy Panamanian reef samples show increased abundance of zooplankton compared to the stressed Florida Keys site. These results indicate both temporal and spatial variability on coral reefs, and suggest further research is needed for plankton dynamics on reefs in order to better understand heterotrophy as a recovery mechanism for bleaching corals. The temporal and spatial differences observed between these studies may be due to site specific bio-geological and oceanographic parameters. As zooplankton serve as a critically important vector to corals, as well as many other species in coral reef ecosystems, it is important to understand the dynamics of zooplankton on coral reefs to aid in their recovery from potentially negative consequences of a changing climate.