Disease

The 1983-1984 die-off of the long-spined sea urchin Diadema antillarum stands out as a catastrophic marine event because of its detrimental effectson Caribbean coral reefs. Without the grazing activities of this key herbivore, turf and macroalgae became the dominant benthic group, inhibiting coral recruitment and compromising coral reef recovery from other disturbances. In the decades that followed, recovery of D. antillarum populations was slow to non-existent. In late January 2022, a new mass mortality of D. antillarum was first observed in the U.S. Virgin Islands. We documented the spread and extent of this new die-off using an online survey. Infected individuals were closely monitored in the lab to record signs of illness, while a large population on Saba, Dutch Caribbean, was surveyed weekly before and during mortality to determine the lethality of this event. Within four months the die-off was distributed over 1,300 km from north to south and 2,500 km east to west. Whereas the 1983-1984 die-off advanced mostly with the currents, the 2022 event has appeared far more quickly in geographically distant areas. First die-off observations in each jurisdiction were often close to harbor areas, which, together with their rapid appearance, suggests that anthropogenic factors may have contributed to the spread of the causative agent. The signs of illness in sick D. antillarum were very similar to those recorded during the 1983-1984 die-off: lack of tube feet control, slow spine reaction followed by their loss, and necrosis of the epidermis were observed in both lab and wild urchins. Affected populations succumbed fast; within a month of the first signs of illness, a closely monitored population at Saba, Dutch Caribbean, had decreased from 4.05 individuals per m2 to 0.05 individuals per m2. Lethality can therefore be as high as 99%. The full extent of the 2022 D. antillarum die-off event is not currently known. The slower spread in the summer of 2022 might indicate that the die-off is coming to a (temporary) standstill. If this is the case, some populations will remain unaffected and potentially supply larvae to downstream areas and augment natural recovery processes. In addition, several D. antillarum rehabilitation approaches have been developed in the past decade and some are ready for large scale implementation. However, active conservation and restoration should not distract from the primary goal of identifying a cause and, if possible, implementing actions to decrease the likelihood of future D. antillarum die-off events.

Results presented at association of Marine Laboratories Scientific Meeting, Merida Mexico, May 2017. 

Sponges are important to reef health, fulfilling a number of structural and functional roles. Despite the wide range of functions they provide, limited research on sponges has been conducted. Their ability to filter the water column of nutrients is essential to keeping the water around reefs clean. Coral reef diseases are becoming more widespread due to multiple factors such as pollution and eutrophication. This study assessed the possible relationship between sponge abundance and disease prevalence in Bonaire, Dutch Caribbean, by using 10 m x 2 m belt transects photographed into 1 m x 1 m quadrats. Per transect, 10 randomly selected photographs were analyzed using Image J to find the total area of sponges and live and diseased coral. Less than 1% disease was found at the study sites because the majority of the coral in the quadrats was partially or completely dead. No correlation was found between disease and sponge coverage. However, a significant correlation was found between percent sponges and live coral coverage. Although there was no correlation found between sponge cover and disease prevalence, the relationship between live coral and sponge is of particular importance for reef health monitoring across the Caribbean.

This student research was retrieved from Physis: Journal of Marine Science X (Fall 2011)19: 35-39 from CIEE Bonaire.

Disease in the ocean is difficult to study because of the logistics involved in conducting marine research. This in turn has resulted in a lack of recognition when outbreaks do occur. Most diseases do not manifest themselves in an organism unless the individual is subject to stress that weakens its ability to fight disease. In recent years, anthropogenic stressors have increased in the world’s oceans; something thought to be increasing the incidence of disease. Recently, ocean surgeonfish, Acanthurus bahianus, in Bonaire, Curacao, and Turks and Caicos, have been observed with black spots on their bodies. There has not been any research on the subject and the causative agent has not been identified. The purpose of this study was to develop a basic understanding of the ocean surgeonfish with black spots. Using timed swims and observations, data on frequency of disease at depths, flash rate, bite rate, and percentage of time spent feeding were collected. There was a significant difference in the frequency of individuals across depth. In addition, there was a positive correlation between number of spots and percent of time spent feeding. However, there was no relationship found between number of spots and feeding rate and flash rate. This disease is affecting 89% of ocean surgeonfish. The implications of this disease are important to understand because ocean surgeonfish play a strong ecological role as herbivores in coral reef ecosystem.

This student research was retrieved from Physis: Journal of Marine Science XI (Fall 2012)19: 64-69 from CIEE Bonaire.

Diseases of oceanic species are difficult to research due to the ocean‟s vast size and the overall logistics involved in studying disease in organisms that live in aquatic environments. Disease in marine organisms may go undetected even when an outbreak occurs. A healthy organism‟s immune system can fight an infection, but if it is weakened due to stress the ability of the immune system diminishes. Increasing human impacts in the world‟s oceans stress organisms through exposure to pollution and global climate change, which can increase the number of diseases in marine organisms. In the last year an unidentified disease has been reported on the Ocean surgeonfish, Acanthurus bahianus. The disease causes black spots on the epidermis of the fish and the deterioration of the fins. This disease has only been observed in Bonaire, Curacao, and the Turks and Caicos, all in the Caribbean. The purpose of this study was to generate a disease scale to facilitate the quantification of the progression of the disease and to compare the results conducted during the warmer months to those of the cooler months. Additionally, timed swims were used to determine the frequency of disease at various depths on the reef. Ocean surgeonfish play an essential role as herbivores in the coral reef ecosystems and since this disease is affecting 82% of ocean surgeonfish in Bonaire; it is crucial to study the distribution of

This student research was retrieved from Physis: Journal of Marine Science XII (Fall 2012)19: 52-58 from CIEE Bonaire.

Coral reef ecosystems provide a number of important ecological services, such as nurseries and protection from storms. This makes their health of vital importance for human populations. Past epidemics in the Caribbean involving high mortality of predominant species, such as long-spined sea urchins (Diadema antillarum) and elkhorn coral (Acropora palmata) have shown the potential of disease to fatally disrupt coral reef ecosystems already under stress. The high prevalence of an unknown disease in ocean surgeonfish (Acanthurus tractus) in the Caribbean, and its apparent ability to infect other fish, including parrotfish and other predominant grazers, is a source of concern since it affects a number of herbivorous fish that are integral to the health of the reefs. This disease is identified by the presence of black spots over the body and fins of infected fish. The number of spots can vary widely. Fin rot and lethargic behavior have been noted in fish with large numbers of spots. Bacterial cultures of swabs from healthy and dark spot epidermis, and necropsy of eight A. tractus specimens were used to attempt to identify the causative agent. This study found smaller bacterial numbers in the dark spot epidermis compared to healthy epidermis cultures, and the presence of encysting organisms embedded in the epidermis directly below black spots in body and fins of A. tractus. Additional encysting organisms were found deeper in the muscle tissue and did not produce a black spot. These encysting organisms are proposed to be digenean trematodes in the metacercariae life stage.

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 103-109 from CIEE Bonaire.

Diseases, pathogens, and parasites in marine ecosystems are difficult to research and understand. Tracking the health of ecosystems, such as tropical coral reefs, is important for protecting these sensitive ecological areas. On the coral reefs surrounding Bonaire and other Caribbean islands, a dark spot ailment has been observed on ocean surgeonfish, Acanthurus tractus. This condition has been found to be a parasite, although its exact taxonomic identity is still unknown. The study of this parasite has become the point of interest for many researchers because dark spots have now been observed on other herbivorous fish in this region. The current frequency of the parasite on ocean surgeonfish and other species of surgeonfish is not known. These herbivorous fish are crucial to a healthy and sustainable coral reef ecosystem; a large change to the health of the population of these fishes could potentially affect the entire system. The purpose of this research was to find the prevalence of this parasite in species of surgeonfish through repetitive transects of counting infected individuals on the reefs of Bonaire. Additionally, collection and excision of parasites from their hosts allowed for a hypothesized genus of the infecting organism. The proportion of the density of ocean surgeonfish infected with this black spot causing parasite was 63% and it was found that the proportion of density for the degree of infection for ocean surgeonfish differed significantly among the population. Furthermore, through individual samplings of ocean surgeonfish, the lowest possible taxonomic description of this parasite was found to be the genus Paravortex.

This student research was retrieved from Physis: Journal of Marine Science XVII (Spring 2015)19: 1-9 from CIEE Bonaire.

Globally, scleractinian coral populations are declining, and to fully understand this decline it is important to study potential coral stressors in-situ. One particularly interesting means of studying stressor effects is fluorescence in corals. Till now fluorescence research has focused primarily on laboratory studies. These experiments cannot fully account for real world effects of stressors such as disease, predation or competition on corals fluorescent patterns in nature. The purpose of this study was to develop a means of in-situ observation to study how coral are using fluorescent proteins in nature. Five sample organisms were used for each of the three categories of stress, and one group of healthy corals were used as control, UV photographs of each were then taken on a weekly basis. Visual trends across the photographs were analyzed for gradients in both red and green fluorescence using Photoshop. From this we detected patterns on predated and competing corals as well as significant gradients in both diseased and healthy corals. Healthy coral results indicated issues in light dispersal across coral colonies necessitating a reworking of the methodology for clearer results. However the presence of discernable trend lines across all other categories supports that this methodology could still be effective for future monitoring efforts. RFP and GFP associated proteins are good candidates for indicating the health of threatened coral reefs due to their ease of use and associations with important coral functions making the methodology discussed here significant in allowing their use.

This student research was retrieved from Physis: Journal of Marine Science XIX (Spring 2016)19: 64-73 from CIEE Bonaire.

Abstract Distribution and abundance of coral diseases have been well documented, but only a few studies con- sidered diseases affecting crustose coralline algae (CCA), particularly at the species level. We investigated the spa- tiotemporal dynamics of diseases affecting CCA along the south coast of Curac ̧ao, southern Caribbean. Two syn- dromes were detected: the Coralline White Band Syndrome (CWBS) previously described and the Coralline White Patch Disease (CWPD) reported here for the first time. Diseases were present at all six study sites, and our results did not reveal a relationship between disease occurrence and human influence. Both diseases were more prevalent on the shallower reef flat than on the deeper reef slope, and during the warm/rainy season than during the cold/dry season. The patterns observed were consistent with a positive link between temperature and disease occurrence. Reef flat communities were dominated by Neogoniolithon mamillare and Paragoniolithon solubile, whereas deeper habitats were dominated by Hydrolithon boergesenii. Dis- eases affected all the species encountered, and no prefer- able host was detected. There was a significant relationship between both disease occurrences and CCA cover. Moni- toring of affected patches revealed that 90 % of lesions in CWBS increased in size, whereas 88 % of CWPD lesions regenerated over time. CWBS linear progression rate did not vary between seasons or species and ranged from 0.15 to 0.36 cm month-1, which is in the same order of mag- nitude as rates previously documented. We conclude that diseases have the potential to cause major loss in CCA cover, particularly in shallow waters. As CCA play a key role in reef ecosystems, our study suggests that the emer- gence of diseases affecting these algae may pose a real threat to coral reef ecosystems. The levels of disease reported here will provide a much-needed local baseline allowing future comparisons. 

Abstract:

Emerging infectious diseases are a worldwide problem and are believed to play a major role in coral reef degradation. The study of coral diseases is difficult but the use of culture-independent molecular techniques has been, and will continue to be, useful in a system where a limited number of visible signs are commonly used to define a “coral disease”. We propose that coral “diseases”, with rare exception, are opportunistic infections secondary to exposure to physiological stress (e.g. elevated temperature) that result in reduced host resistance and unchecked growth of bacteria normally benign and non-pathogenic. These bacteria are from the environment, the host, or the coral mucus layer and become opportunistic pathogens. While difficult and time consuming, we do not advocate abandoning the study of disease-causing pathogens in corals. However, these studies should include comprehensive efforts to better understand the relationship between coral diseases and environmental changes, largely anthropogenic in nature, occurring on coral reefs around the world. These environmental insults are the cause of the physiological stress that subsequently leads to coral mortality and morbidity by many mechanisms including overwhelming infections by opportunistic pathogens.