reef health

Abstract

Hard coral cover throughout the Caribbean has been in decline for at least fifty years due to large-scale disturbances such as White-Band-Disease, die-off of sea urchin populations, and coral bleaching. Local stressors, like coastal water pollution and eutrophication, have amplified this decline. The ecosystem services of coral reefs offer opportunities for tourism, recreation, employment and biodiversity. In Aruba, coral cover is naturally low due to a high abundance of sand, leaving less benthic area available for coral growth. The outbreak of stony coral tissue loss disease in Aruba in December 2022 presented a new threat for local coral reef communities. Assessment of coral cover is necessary to devise methods to mitigate the stressors that corals in Aruba face. In this study, 12 sites were identified that reflect the heterogeneous status of Aruba’s coral reefs for investigation to examine coral health and the development of the ecosystem since 2019. While on average, coral cover remained constant, almost half of the surveyed sites showed an increase in (macro)algae cover coupled with a decrease in coral cover, indicating stress on coral reefs. Five out of 12 sites showed a degrading ecosystem trend within the last four years. By assessing the spread of stony coral tissue loss from the surveyed data, a metric for the development of Aruba’s coral reefs was determined. We found that nine coral species, including important reef-building coral species such as Montastraea cavernosa, Orbicella annularis and Orbicella faveolata have been infected by the disease. About six months after the outbreak of the disease,  13 % of all coral showed signs of the disease. This number is expected to increase, indicating strong changes for Aruba’s coral reefs in the near future.

Curaçao's coral reefs are subjected to a deteriorating momentum risking the health and therefore sustainability of this vital ecosystem. Despite the dependency of the Island's prosperity on the condition of the ecosystem, research suggests that wastewater management is likely to be a significant contributor to this effect. Incorporating both open literature results and information obtained from an extensive constructed research network, this study demonstrates essential aspects of the urban wastewater management system of Willemstad regarding the quantity and quality of the urban wastewater fluxes and their potential environmental implications. The system, which merely connects 33\% of Curaçao's population, is concluded to be outdated and insufficient with respect to capacity as well as treatment efficiency. Although it is solely designed for pure domestic wastewater, this study concluded and demonstrated the significant impact of illegal discharge onto this system by industrial sectors leading to both high contamination loading and increased wastewater volumes. The combination of these features is the major cause of wastewater discharge pathways into marine environments. Arising from the constructed urban wastewater flux model, which visualizes the wastewater management system, 14 discharge locations correlated to significant environmental contamination pathways are identified with Piscadera Bay, Rif Mangrove area, Playa Kanoa and Shut concluded as the utmost importance. Furthermore, the model revealed that the urban wastewater is predominantly directed towards the treatment plant Klein Hofje via either the northern trajectory (Bonam - Suffisant F - Garipitoweg - Argentianweg - Klein Hofje) or the southern one (SVB - Klein Hofje). Also, the quantity and quality of the fluxes are estimated based on the connected area and the potential industrial activities within it. However, validation of these estimations is recommended since no water quantity and quality analysis was performed or available for conducting the modelled estimations. Furthermore, since the system is partly a combined sewage system, hence harvesting stormwater fluxes as well, its effect is recommended to incorporate in the model and estimations for accuracy purposes. Lastly, the government reports that at least 90\% of all industrial wastewater is discharged either directly into the ocean or onto the sewer system. Since the actual ratio as well as the water quality remains unknown this is recommended for future research. Overall, this study enables tailored future research programs to overcome the discussed limitations and with that significantly contribute to eliminating the current existing white spot concerning the effect of urban wastewater fluxes on the marina ecosystem of Curaçao.

Cleaner species are believed to help maintain the health of client species by cleansing them of parasites, dead or infected tissue and debris which leads to healthier fish and in turn maintains the health of the entire ecosystem. Cleaning intensity may vary depending on several factors such as ectoparasite load, hunger levels of cleaners, and possible overlap of nocturnal and diurnal client species. Data on cleaning intensities during three different times of day (early morning, afternoon, and late evening) were collected for three different species of cleaners: Periclimenes pedersoni, juvenile Thalassoma bifasciatum, and Gobiosoma spp. in Bonaire, N.A. Research was conducted at the Yellow Sub dive site Bonaire, N.A. Analysis of the data collected during this study indicate that different cleaning species do in fact show significant differences in the amount of time they spend cleaning throughout the day. In addition, we found that the number of client species visiting the different cleaner species also varied, with P. pedersoni having the largest number of clients visiting and juvenile T. biffasciatum having the smallest.

This student research was retrieved from Physis: Journal of Marine Science III (Spring 2008)19: 55-59 from CIEE Bonaire.

Coral reefs around the globe are subject to environmental and anthropogenic stressors that are causing habitat degradation and a decline in reef resilience. Past studies of Caribbean reefs document a decrease in coral cover with a simultaneous increase in algal cover after significant stress, disturbance, or coral mortality. The long-term shift from coral dominated reefs to algae dominated reefs is known as a coral – algal phase shift. This study assessed the progression of a coral-algal phase shift at the Yellow Sub study site on Bonaire, Dutch Caribbean, by comparing current coral and algal benthic cover to historical data at a nearby study site. Research was conducted over a five-week period from September to October 2012. Twenty 10 m transects were filmed and analyzed through Coral Point Count software to determine percent live coral and algal cover. Mean coral cover at the study site was 14.25%, algae cover was 72.37% and the algae: coral ratio was 5.07. Diseases present were noted and included Yellow Band disease, White Plague, Dark Spot disease, and coral bleaching. In comparison to historical data at a nearby study site, a significant increase in the algae: coral ratio was observed, indicating the progression of a coral – algal phase shift at Yellow Sub study site. This study served to contribute to the scientific knowledge of Bonaire reef ecosystem resilience and the results obtained will help provide evidence and motivation to increase coral reef conservation efforts.

This student research was retrieved from Physis: Journal of Marine Science XII (Fall 2012)19: 80-90 from CIEE Bonaire.

Serranidae, the grouper family, are common carnivorous fish that inhabit Bonaire’s coral reefs. Smaller grouper species are commonly spotted along the lower layers and crevices under the complex coral reef structure. These carnivores control population levels of lower trophic level omnivores (e.g. damselfish). Four smaller grouper species (Cephalopholis cruentata, Cephalopholis fulva, Epinephelus guttatus, and Epinephelus adscensionis) densities were used as indicator to evaluate current coral reef health on Bonaire. Maximum reef relief was estimated to evaluate for consistency in reef complexity across box transects. AGGRA fish methodology was used to survey densities of targeted Serranidae species. Recorded densities were compared to previously reported grouper densities from 2003 to 2011. A significant increase in density for C. cruentata (9.58 individuals/100 m2 ) and E. guttatus density (4.17 individuals/100 m2 ) was found since 2011. E. adscensionis and C. fulva densities were found to be consistent since 2003. Overall, a healthy coral reef was supported by the evidences of an increase in C. cruentata and E. guttatus since 2011. This increase in Serranidae density is controversial to commonly proposed competition between lionfish and native carnivores. Lionfish removal efforts are hypothesized to positively affect smaller Serranidae density, leading to a higher density in 2013. A biocontrol mechanism is proposed as a long-term solution following lionfish invasion. Future directions are discussed in regards to maintaining a resilient Serranidae population on Bonaire’s coral reef by establishing marine reserves and continued removal of Pterois spp. individuals.

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 69-78 from CIEE Bonaire.

Bonaire’s reefs remain among the best in the Caribbean. However, our monitoring has revealed some potentially troubling trends that may require management action. In 2005, we reported to the Bonaire Marine National Park on the status of Bonaire’s coral reefs, and we suggested a strategy for monitoring trends among four key reef attributes we believe track the health and resilience of Bonaire’s reefs (Steneck and McClanahan 2005). Here we report the results of monitoring studies conducted 2003, 2005 and now 2007 at each site. Where appropriate, we drew from Bonaire’s first AGRRA assessment conducted in February 1999 (Kramer and Bischof 2003) to extend temporal trends over a period of eight years. 
Troubling trends
We see three troubling trends of increased macroalgae, declining herbivory from parrotfish, and increases in damselfish populations. Of these, the first two are most serious (see Chapters 1, 2 and 3). Secondary trends of concern, increases in damselfish populations (Chapter 4) and declines in coralline algae (Chapter 1), could lead to reduced recruitment of reef corals (Chapter 7), but to date this is not evident (Chapter 7). Importantly, coral cover remains relatively high (Chapter 1). The monitored group of carnivorous fishes, the lutjanid snappers, are holding constant but we remain concerned about the past (Steneck and McClanahan 2003) and continued loss of other larger bodied reef carnivores such as groupers and barracuda. The positive ecological role of parrotfish is well documented (e.g. Mumby et al. 2006) so their decline is troubling. It is unclear exactly why their population densities are declining. While parrotfish are not currently a widely sought group of reef fish (Chapter 8), fishing pressure on them is growing. It is possible they are vulnerable to even modest fishing pressure, particularly from fish traps. Accordingly, we recommend that the capture and killing of parrotfish be stopped because of their key ecological role on Bonaire’s coral reefs. Further, other groups of grazing herbivores such as the longspined sea urchin (Diadema antillarum) are increasing but too slowly to effectively replace the functional role of parrotfish (Chapter 1). We suggest continued monitoring of key drivers of reef health (coral cover, algal abundance, herbivory and coral recruitment). Some standard protocols such as the Atlantic and Gulf Rapid Reef Assessment (AGRRA) are entirely commensurable with the data presented in our reports in 2003, 2005 and 2007 (this report). A streamlined monitoring protocol is likely to be most useful to managers to alert them as a potential problem is growing and, perhaps more importantly, to show improvement when it occurs.
 
 

Bonaire has long been considered to have amongst the healthiest reefs of the Caribbean. However, at the 2002 Annual Meeting of Pew Fellows for Marine Conservation in Bonaire, several scientists with a long history of research on Bonaire’s coral reefs, expressed concern over the future of the island’s reefs. Specifically, they identified the decline in large predatory fish such as groupers as a noticeable change during the past decade. They suspected that this change resulted from increased fishing pressure on Bonaire’s reefs. They also suggested the Bonaire authorities take action to protect the reef-fish stocks. In response to those concerns, officials of the Bonaire Marine Park consulted with scientists and fishermen on Bonaire to explore the possibility of establishing fish protected areas (FPAs), as a way to protect the reef fish stocks. If FPAs improve both fish stocks and the condition of the coral reef, all stakeholders will profit. If fish stocks increased significantly in FPAs, a “spill over” of these fish to adjacent fished areas would be expected. Also, fish that perform important ecological functions could improve the quality of the coral reef ecosystem. Therefore, areas protected from fishing should have healthier coral reefs, which would also improve the island’s valuable ecotourism businesses. The Pew Fellows program funded a research project designed to identify potential FPAs. The Bonaire Marine Park authority, in consultation with the local fishing community would determine the location and size of the FPAs. To monitor the effects of fish protection areas so fishing impacts can be isolated from other factors (such as natural changes, shore-based impacts or effects of scuba divers), an equal number of similar reef sites were selected for study, with half closed to fishing while half remaining open (as “control” reefs). This report reviews the status and recent trends of coral reefs in the Caribbean and Bonaire. It identifies the key features of healthy reefs and how Bonaire’s reefs compares with those elsewhere in the Caribbean. The seven chapters go into scientific detail on factors contributing to the condition of Bonaire’s reefs as of March and April 2003. Special focus will be on factors that threaten reef health or are critical to reef resilience such as seaweed overgrowth, nutrient inputs from land and the ecology of juvenile corals. The report concludes with chapters on the socioeconomic effects of Bonaire’s coral reefs on the fishing and diving industries that depend on them.
Summary Results 2003: The Biological Status of the Coral Reefs of Bonaire & Socioeconomic Implications
 In March and April of 2003, teams of researchers studied the coral reefs of Bonaire to establish the baseline conditions that currently exist and against which trends can be determined and future changes from fish protection areas be assessed. Six study sites were chosen with advice from the Bonaire Marine Park. They represent a range of comparable reefs minimally affected by the 1999 Hurricane Lenny. The sites selected for this study were: Windsock, Plaza, Forest on Klein Bonaire, Scientifico, Barcadera and Karpata (Fig. 0.4). When feasible, parallel studies were conducted at 5 and 10 m depths, however, only the latter depth had fully developed reefs at all sites. The study was designed to quantify the patterns of abundance of the dominant reef organisms as well as to study the processes that control their abundances or threaten their stability. This was done to establish a baseline and to determine if significant differences exist among any of the study sites that would make them a poor choice as a FPA. We also examined some socioeconomic factors related to fishing and scuba diving activities if FPAs are established in Bonaire.