Investigating the correspondence between environmental variation, abundance, and interspecies competition of a globally significant echinoderm pathogen

Diadematidae scuticociliatosis (DSc) is an emerging and globally distributed threat to keystone herbivorous urchins within coral reef habitats. The condition is caused by the DSc Philaster clade (DScPc), which has also been observed on the surfaces of sympatric corals, sponges and macroalgae at the time of mass mortality and for months afterwards. Key questions remain around factors resulting in its emergence, overlapping distribution with coral diseases, and how environmental variation and interspecific competition affect DScPc dynamics. We performed a time series analysis of DScPc and related ciliate taxa at a single site (Vaca Key, Florida) over 18 months in plankton and surfaces of corals, sponges, and macroalgae in association with physicochemical parameters and chlorophyll a. We found that DScPc was detected on surfaces in springtime, concomitant with enhanced macroalgal cover, but was largely replaced by a related species of Philaster into summer. DScPc was detected in the water column at the same site in late Fall through Spring, where the related species was detected in Spring into Summer. DScPc consumed zooxanthellae, retaining their chloroplasts, in culture-based experiments. Together, these data suggest that the DScPc associates with springtime primary production, which may result from consumption of dissolved or particulate organic matter derived from primary production. Furthermore, consumption of zooxanthellae leads to interesting questions about the association between bleaching and other coral diseases and DSc-Philaster emergence.

Presentation Preference: Oral

Primary Presenter: Ian Hewson, Cornell University (hewson@cornell.edu)

Authors:

Michael Henson, Northern Illinois University  (mhenson@niu.edu)

Christopher DeRito, Cornell University  (cmd49@cornell.edu)

Mya Breitbart, University of South Florida  (mya@usf.edu)