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Dry Tortugas National Park Long Term Monitoring and Assessment Project 2007 Annual Report

Long-term Status and Trends from 2004 to 2006 for the Coral Reefs of the

Dry Tortugas National Park

(Summarized results)

Scleractinian Species (Stony Coral) Inventory

• In 2005, a total of 29 stony coral species were identified for the 23 Dry Tortugas monitoring stations compared to 33 total species in 2004.
• In 2005, five species were present at all survey stations; Porites astroides, Millepora alcicornis, Montastrea annularis (species complex), Diploria strigosa, and Agaricia agaricites.
• The mean, or average, number of stony coral species per station decreased from 2004 to 2005 at five of the six study sites that have data for both years.
• In 2005, bleaching or disease was recorded at 18 of 23 survey stations.

Video Transect Survey

• The mean percent cover of stony corals per station for all of the Dry Tortugas decreased from 2004 (7.2 percent) to 2005 (6.7 percent). This decline was not statistically significant.
• Statistically significant declines from 2004 to 2005 were found at two sites: Bird Key (12.6 percent to 11.3 percent) and Prolifera Patch (15.1 percent to 13.8 percent). These two sites had the highest mean percent of stony coral cover for both years. With the exception of Palmata Patch (mean percent stony coral cover of roughly 5.5 percent for both years), no other site had stony coral cover above five percent.
• At Bird Key the coral species with the highest mean percent of cover across all survey stations were Montastrea annularis, M. cavernos, Colpophyllia natans, and Siderastrea siderea.
• When averaged across all stations for each site, octocorals are the most abundant taxonomic group at five of the seven Dry Tortugas sites.
• At Temptation Rock the mean percent cover of the zoanthid Palythoa caribaeorum (about 13 percent for 2004 and 2005) is much higher than at any other survey site.

Clionid Sponge Survey

• The mean clionid sponge area per station for each site decreased from 2004 to 2005 at five of the seven survey sites.
• Palmata Patch had no clionid sponges in either year.
• At White Shoal the mean clionid cover is below 0.5 centimeters squared/meters squared (cm²/m²) for both years, but increased slightly from 2004 to 2005.
• The coral species most affected by clionid sponges are Montastrea annularis (complex), M. cavernosa, and Siderastrea siderea.

Octocoral Abundance Survey

*This survey was conducted at only one site, Mayer's Peak.

• Octocorals from 10 different genera, or classifications, were observed at Mayer's Peak in 2005, the first year of the Octocoral Abundance Survey.
• The most common Octocoral genera were Briareum (six colonies/meters squared [m2]) Erythropodium (five colonies/m²), Eunicea (4.5 colonies/m²), and Pseudopterogorgia (four colonies/m²).

As shown by the two Dry Tortugas sites monitored since 1999, see the CREMP 2007 executive summary, coral cover has been declining in the Dry Tortugas for several years. Although significant declines are not observed at most survey sites, decreases in coral cover have continued from 2004 -2005. The frequency and intensity of tropical storms and hurricanes that have passed over this area during this time period may have contributed to the observed declines. Continued monitoring of these sites is necessary in order to understand how coral reefs are changing in Dry Tortugas National Park.

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The DRTO CREMP 2007 Annual Report was prepared by the Fish and Wildlife Research Institute

Funding for DRTO CREMP has been provided by the National Parks Service