Walter C. Jaap

Patterns of spread of coral disease in the Florida Keys

Reefs in the Florida Keys are experiencing a dramatic increase in the number of localities and number of species with coral disease. In extensive surveys from Key Largo to Key West in 160 stations at 40 randomly chosen sites, there has been a dramatic increase in (1) the number of locations exhibiting disease (82% of all stations are now affected, a 404% increase over 1996 values), (2) the number of species affected (85% of all species are now affected, a 218% increase over 1996 values), and (3) the rate of coral mortality (the deep fore-reef at Carysfort experienced a 60% reduction of living coral cover during the survey). Two null hypotheses (1) that the incidence of disease has remained constant through time and (2) that the apparent increase in disease is due to a lack of comparable earlier data, are both falsified. Different diseases exhibit different patterns of spread: some diseases (e.g. black band) exhibit low incidence and jump rapidly between sites; other diseases (e.g. white pox) exhibit patchy distributions and increase in frequency at affected sites from one year to the next. The central question of why so many corals are becoming simultaneously susceptible to a host of marine pathogens remains unanswered.

Coral reef restoration

Abstract Coral reefs are widely recognized for concentration of biological activity, fisheries and tourism, coastal protection, geological processes, and aesthetic wonder. A principal cause of reef damage in Florida is ships running into reefs. The other major human impact on Florida’s reefs is dredging for beach renourishment and channel maintenance. In response to chronic reef damage, federal and state agencies and consultants have developed techniques to restore, as best possible, reefs impacted by human disturbance. These efforts include salvaging sponges and corals, removing loose debris from the reef, rebuilding three-dimensional (3-D) structures onto leveled-scarified reef surfaces, and transplanting sponges and corals back on the cleared reef surfaces. This paper presents an overview of restoration approaches; a discussion on legal and administration to both damage and restoration of these essential fish habitats; a brief review of some case studies; and a discussion of restoration success criteria. Salvage of corals and sponges is critical to the success of any reef restoration effort. If a living surface is allowed to sit on the sand for a few days, that surface will die. Often the grounded vessel will have crushed the reef, excavating sediments and rubble that end up as a berm of material behind the ship’s resting position. Dealing with massive amounts of rubble debris is challenging. The options include leaving it in place and stabilizing it with cements; moving it a long way from the site and dumping it in deep water; or reconfiguring it by moving it off reef and building piles where it can do no harm. After the debris is moved off the reef platform, corals and other sessile benthic organisms (salvaged resources) can be transplanted on the damaged area. Monitoring is important to determine the success of the restoration and to look for ways to improve future projects. Sampling sites for monitoring should include restored areas plus a reference area (undamaged habitat of a relatively similar nature that is in close proximity) for comparison. The following questions should be addressed for any reef restoration project: are the transplanted organisms still secured to the reef? Is the vitality (color, disease, algal competition) of the transplanted organisms equivalent to the organisms in the reference sites? Is recruitment (settlement of juvenile organisms) similar in the restored areas and the reference areas? Monitoring should be tied to decision making so corrections can be made.

Platforms of the Nicaraguan Rise: Examples of the sensitivity of carbonate sedimentation to excess trophic resources

The Nicaraguan Rise is an active tectonic structure in the western Caribbean. Carbonate accumulation on its platforms has not kept pace with relative Holocene sea-level rise, despite a tropical location remote from terrigenous sedimentation. Trophic resources apparently exceed levels favoring coral-reef development because sponge-algal communities dominate the drowning western platforms, in contrast to mixed coral-algal benthos on Pedro Bank and well- developed coral reefs along the north coast of Jamaica. Concentrations of biotic pigments in sea-surface waters show a corresponding west-east gradient; oceanic waters flowing over the western banks carry nearly twice as much biotic pigment as oceanic waters north of Jamaica. Sources enriching the western Caribbean are terrestrial runoff, upwelling off northern South America, and topographic upwelling over the Nicaraguan Rise. That relatively modest levels of trophic resources can suppress coral-reef development holds important implications for understanding carbonate platform drownings in the geologic record.

Halimeda bioherms along an open seaway: Miskito Channel, Nicaraguan Rise, SW Caribbean Sea

A recent research cruise to examine small, detached carbonate platforms situated on the Nicaraguan Rise in the SW Caribbean Sea has revealed the presence of numerous Halimeda bioherms. Based upon interpretations from seismic reflection data some exceed 140 m in relief. This is the first documented occurrence of these green-algal buildups in the Caribbean/Bahama Bank region. The Halimeda bioherms form a nearly continuous band that borders the margins of the Miskito Channel—a shallow, open, 125 km long seaway. This 220 m deep channel bisects the Miskito Bank which is a major carbonate shelf. In seismic profile the bioherms appear acoustically “soft” and reveal a local relief of 20–30 m. Tops of these features lie in about 40–50 m of water. Samples from dredge hauls are coarse, poorly cemented packstones/grainstones which are dominated by largely unbroken, disarticulated Halimeda segments set in a poorly sorted sandy matrix. Exposed surfaces were stained brown. Very little living material was brought up in the dredges. The significance of these bioherms and their full extent in the Caribbean are not understood. Undoubtedly, further study will provide important answers concerning their role in the geologic development of Caribbean carbonate platforms.

Changes in coral reef communities among the Florida Keys, 1996–2003

Hard coral (Scleractinia and Milleporina) cover data were examined from 37 sites surveyed annually from 1996 to 2003 in the Florida reef tract, USA. Analyses of species numbers and total cover showed that site-to-site differences were generally very much greater than differences among times within sites. There were no significant differences among different geographical areas within the reef tract (Upper, Middle and Lower Keys). Large-scale changes documented included a reduction in species numbers and total cover on both deep and shallow offshore reefs between 1997 and 1999 followed by no recovery in cover, and only scant evidence of any recovery in species numbers by 2003. These changes coincided with bleaching events in 1997 and 1998, and the passage of Hurricane Georges through the Lower Keys in 1998. The lack of recovery among offshore reefs suggests that they were no longer resilient. Multivariate analyses revealed that some sites showed relatively little temporal variation in community composition, essentially random in direction, while others showed relatively large year-on-year changes. There was little evidence of any major region-wide changes affecting assemblage composition, or of any events that had impacted all of the sampling sites in any single year. Instead, different sites exhibited differing patterns of temporal variation, with certain sites displaying greater variation than others. Changes in community composition at some sites are interpreted in the light of knowledge of events at those sites and the relative sensitivities of species to various stressors, such as changes in cover of Acropora palmata and Millepora complanata at Sand Key following the bleaching events and hurricane in 1998, and declines in Montastraea annularis at Smith Shoal following a harmful algal bloom in 2002. For most sites, however, it is impossible to determine the causes of observed variation.

A Retrospective Analysis and Comparative Study of Stony Coral Assemblages in Biscayne National Park, FL (1977–2000)

Abstract. The hardbottom, patch, and bank reefs of Biscayne National Park (BNP) are among the most northern reef communities in the Florida Keys reef tract. The close proximity of BNP reefs to highly developed areas (i.e., the greater Miami metropolitan area) make them both heavily used and susceptible to a multitude of anthropogenic stresses. This study analyzes a unique 1977–1981 data set on stony-coral abundances and percent cover, collected from eight reefs in BNP, and compares this more than 25-year old data set with published data from surveys conducted from 1994–1996 and 1998–2000. In 1977–81, stony-coral cover on the eight reefs ranged between 8% and 28%, whereas coral cover reported from surveys in 1998–2000 ranged between 0.4% and 10%. Significant declines in cover of all coral species were seen at BNP reefs in the ? 20 years between data sets, although few changes were observed in species richness and taxonomic distinctness values. Spatial differences were observed between lagoonal patch reefs and outer bank reefs, consistent with previous reports of greater loss of coral cover on offshore reefs. Previous reports have suggested that high juvenile coral mortality due to fish predation, physical stresses, and thermal stresses have contributed to reduced cover at offshore BNP reefs.