This project is a collaboration between the laboratories of Dr. Howard R. Lasker, University at Buffalo and Dr. Peter J. Edmunds, California State University, Northridge.  The research focused on soft corals on St. John, US Virgin Islands.  The hard corals on these reefs have been monitored since 1987, providing one of the most extensive data sets of a Caribbean reef.  The new work adds octocorals to that monitoring effort at a time at which Caribbean octocorals have been reported to be increasing in abundance, even as the hard corals decline.  St. John is particularly suited for such a study as 75% of the island is a national park, minimizing locally derived anthropogenic effects.

The research has proceeded with 4 general goals, a description of the species of soft corals on the shallow reefs, analyses of the trends in soft coral abundance over the past 25 y, identification of mechanisms causing soft corals to change in abundance, and developing the capacity to forecast the future of soft corals on Caribbean reefs.

Soft corals, unlike the hard corals, have received relatively little attention in research programs and one of the fundamental tasks of the project was documenting the composition of the soft coral community at three sites chosen to characterize a range of shallow water reef habitats.  Those surveys have characterized the community at species level precision and indicate that most of the Caribbean fauna is present on St. John and that species present at the sites varies with differences in those physical environments. 

Retrospective analyses of legacy data from earlier monitoring demonstrates that since a low point following the 1997-98 El Niño soft corals have increased in abundance and are more abundant than prior to the 1997-98 event.  However, the composition of the community that developed after 1997-98 is different than prior to the event.  Composition over the past 4 years has been stable.  This is in contrast to scleractinian abundances which have continued to decline at most sites. The effects of Hurricanes Irma and Maria on these reefs and the species level resolution data that we now have provides opportunity to further explore recovery following disturbance.

The dense “forests” of octocorals that have developed at some sites modify the environment and create a habitat in which octocorals interact with each other, competing for space in the canopy and possibly facilitating recruitment.

Monitoring recruitment to tiles placed on the reef indicates that soft coral larvae are arriving and/or surviving at higher rates than scleractinians. Positioning of these larvae both on artificial tiles and the natural reef substrate shows soft coral larvae have microhabitat preferences which may differ from hard corals, possibly explaining some of the differences in success of the two groups. Survival of soft coral recruits has been high.  However, abundances of the soft coral larvae also indicate that the relative abundances of adults are driven by a combination of supply of larvae and differential survival of larvae.

These data are critical to understanding how Caribbean reefs will respond to continuing change in the environment and to future episodic events such as bleaching and hurricanes.

In addition to training undergraduate and graduate students, participants in the project have also contributed to the educational program at the Virgin Islands Resource Center in its outreach programs for students in the Virgin Islands.

The project is also contributing to the further development of the website South Florida Octocorals: A guide to identification (https://nsuworks.nova.edu/octocoral_species-list/), which is designed to help with soft coral identification by both the public and specialists.

Data from this project are available at http://www.bco-dmo.org/project/562086 and https://www.bco-dmo.org/dataset/682966/data.

Last Modified: 05/06/2018
Modified by: Howard R Lasker