MICROMORPHOLOGICAL RESPONSES TO AMBIENT TEMPERATURE IN SCLERACTINIA

Currently, the world’s coral reefs are threatened by ocean acidification, climate change, and localized anthropogenic disturbances. The coral cover on reefs has been steadily declining. It is estimated that 80% of the reef cover in the Caribbean and over 50% of the reef cover in the Great Barrier Reef has been lost in the last few decades. This loss of coral cover threatens the billion dollar industries of ecotourism, products derived from the reefs, and fisheries in addition to disrupting some of the diverse and ecologically important areas in the oceans. Despite the economic and ecological significance of Scleractinia, their evolutionary relationships are often uncertain. The divide between molecular phylogenies and traditional taxonomy has the potential to create difficulties in conservation efforts. Micromorphological characters have shown promise in creating morphology based taxonomies that more strongly agree with molecular phylogenetics. In order to both assess the stability of micromorphology in scleractinian corals and to assess the plastic response of corals to temperature shifts, experimental conditions in the laboratory were created using water temperature as the sole independent variable. The temperatures used for this analysis were 22 degrees C, 25 degrees C, and 28 degrees C. In order to better estimate the plastic response within Scleractinia to temperature we used three species of hermatypic corals: Galaxea astreata, Favia speciosa, and Caulastrea furcata. Colonies were grown from a single mother colony per species to limit genetic variability. After being grown in experimental conditions for six months, the specimens were cleaned and imaged using Scanning Electron Microscopy to examine skeletal features on the micron scale. Micromorphological characters were examined for variability between specimens and stability within the experimental colonies. We found morphological change in skeletal structure in response to increased temperature, but the overall structure of the skeletal micromorphology remained recognizable and stable enough for use in morphological taxonomy.