Coral reefs

Tubastrea coccinea is an invasive coral species found on the reefs of Bonaire. These corals are typically seen at various densities (up to 80% m-2) on hard, vertical substrata suggesting that biotic resistance could be one possible biological factor preventing settlement of T. coccinea elsewhere (e.g.,,, horizontal substrata). The impact potential competitors have on the successful invasion, recruitment and growth of T. coccinea was experimentally assessed by establishing replicated 15 x 15 cm plots of substrata already inhabited by single species or combinations of native species (0-3 and 3 seeded with adult T. coccinea) at the Harbor Village jetty, Kralendijk, Bonaire, which had the necessary vertical substrata. Monitoring occurred over a period of three weeks to assess percent cover change of the studied organisms. Additionally 15 vertical, 5 m transects were run to evaluate mean percent cover of all sessile species that inhabited the surveyed locations for a general representation of species diversity at the jetty. T. coccinea was not observed to settle in any of the experimental plots nor did the seeded adult conspecifics show any evidence of growth or recruitment. Observational data indicated that an algal turf had the highest mean percent cover, but in areas around T. coccinea, algal turf percent cover decreased by almost 20%, suggesting competition between the two organisms. No firm conclusions could be drawn about T. coccinea recruitment or growth, but results suggested that the presence of an invasive species may negatively affect the growth of native species when they are found in close proximity to it.

This student research was retrieved from Physis: Journal of Marine Science IV (Fall 2008)19: 2-6 from CIEE Bonaire.

Foraging success is affected by choice of feeding association, color phase, and habitat type. Bar jacks (Caranx ruber) exhibit a number of feeding associations, changes in coloration from silver to dark brown/black, and utilize different habitat types within the fringing reef ecosystem for feeding. The objective of this study is to determine if foraging success is affected by 1) feeding association utilized (individual, conspecific, or multispecies groups) 2) color (black or silver) or 3) habitat type (reef flat or reef slope). Observations of C. ruber were conducted at two dive sites on the fringing reef of Bonaire using SCUBA. The number of bites min-1 was used as a measure of foraging success. Analysis of results shows that C. ruber has significantly greater foraging success when feeding alone and in multispecies groups as opposed to feeding with conspecifics. Dark brown/black C. ruber have double the feeding rate as that of silver and habitat type did not have an affect on C. ruber foraging success. In conclusion, foraging success of C. ruber, measured in bites min-1 , is affected by choice of feeding association and coloration, but is not affected by choice of habitat.

This student research was retrieved from Physis: Journal of Marine Science V (Spring 2009)19: 10-13 from CIEE Bonaire.

This study explores the competitive and allelopathic interactions of native sponges and the non-native ascidian, Trididemnum solidum, in the space-limited coral reef environments of Bonaire, NA. The study had two main goals: (1) to identify native sponge species and provide estimates of sponge and T. solidum percent cover, and (2) investigate the allelopathic and overgrowth responses of native sponges and T. solidum when they are engaged in spatial competition with each other. Belt transects and modified nearest-neighbor methods were used to quantify abundance, species diversity, and interactions between native sponges and T. solidum at the Karpata dive site on Bonaire. Overall, it was found that percent cover of sponges significantly increased with depth while percent cover of T. solidum varied among depths, reaching a maximum at 11 – 15 m. Twenty-two species of sponges were recorded with species composition and abundance varying among depths while diversity among depths was not significantly different (p = 0.880). It was found that percent cover of T. solidum had a significant effect on the number of contact interactions. A closer look at contact interactions revealed that T. solidum frequently (87.5 % - 100.0%) overgrew sponges and caused tissue necrosis but was itself never observed to be overgrown. Staged interactions between two abundant encrusting sponges (Ulosa ruetzleri and Halisarca sp.) and T. solidum showed that native sponge growth is impaired by the ascidian and that T. solidum uses allelopathy when expanding its colonies. As described by this study, the success of T. solidum in its expanded range may provide support for two additional hypotheses: the evolution of increased competitive ability hypothesis, which attributes the success of non-native species to their increased ability to overgrow native organisms, and the novel weapons hypothesis which explains that non-native species are successful because they harbor allelopathic chemicals that native organisms have not evolved defenses for.

This student research was retrieved from Physis: Journal of Marine Science V (Spring 2009)19: 2-9 from CIEE Bonaire.

Biodiversity of coral reef fish species is often related to the structural complexity and diversity of their habitats. This study explores the relationship between fish species richness, habitat diversity (substrate diversity) and habitat complexity (rugosity). Habitat diversity and topographic measures were used to predict reef fish diversity. It was hypothesized that high fish species diversity would show a positive correlation with greater habitat structure, which includes habitat diversity and topographic complexity. Fish species richness was determined at six dive sites in Bonaire, N.A. (Karpata, Andrea II, Cliff, Windsock, Angel City, and Red Slave) using data from 20 randomly chosen expert-level surveys provided by Reef Educational Environmental Foundation (REEF) for 2004 – 2009. Preliminary analysis of REEF data was used to select sites with high and relatively low fish species richness to make comparisons with the habitat structural complexity measurements (substrate diversity and rugosity). Substrate diversity and habitat complexity were measured using a 10 m transect randomly placed at 4 depths (2, 6, 12, and 18 m) at each site. Substrate diversity was determined by measuring the percent cover of the different substrates and then using the Shannon Diversity Index to determine H’. The rugosity of the sample area was measured by fitting a lead line to the reef at each of the determined depths. Overall results suggested that topographical complexity (rugosity) was not related to high fish species richness at dive sites on Bonaire. There was a weak positive correlation between H’ and fish species richness on the reef slope and a weak negative relationship between H’ and fish species richness on the reef flat. The results provide evidence that there are more factors to consider when explaining fish species richness on coral reefs than the structural complexity of the habitat at the scale of this study.

This student research was retrieved from Physis: Journal of Marine Science VI (Fall 2009)19: 66-72 from CIEE Bonaire.

The use of biological entities as indicators of environmental stress can provide links between changes in ecological conditions and ecosystem productivity. Historically, bioindicators have been used as a rapid-assessment tool of areas declining in sustainability for the inhabiting organisms. This study investigated the utility of sessile, filter feeding Christmas tree worms (Spirobranchus giganteus) as bioindicators of the presence of potential coral reef stressors. Christmas tree worm density was compared at low impact sites (> 200 m from a commercial establishment) and high impact sites (< 200 m from a commercial establishment). For each site, four quadrats were randomly placed along a 10 m transect at 6, 12 and 18 m depths to assess percent live coral cover and Christmas tree worm density. These data were compared with potential environmental stressors such as excess nutrients (nitrite, nitrate, ammonia and phosphate), human gut (Enterococcus) bacteria, sedimentation rates, and sediment particle size distributions between high and low impacted sites and among depths. Approximately 97% of the worms inhabited live coral. Live coral cover was similar for 12 and 18 m at both high and low impacted sites (~ 17 % - 20 %) but significantly lower at 6 m depth (~ 2 % - 8 %). Despite the similarity in live coral cover at depth, there were significantly more Christmas tree worms at 12 m of high impact sites. At all other sites and depths, the worms never exceeded ~ 1.5 worms m-2. At 12 m, water chemistry analyses did not show any differences between site impact except for phosphate, with significantly greater concentrations at high impact sites. Bacterial loads, sedimentation rate and particle size distributions did not show any differences between site impact although there were finer sediments at high impact sites and coarser sediments at low impact sites. S. giganteus may be found at high densities at high impact sites due to a greater availability of food acquired through filter-feeding biota. Therefore, they may be used as novel indicators of the presence of environmental stressors, such as excess nutrients and finer sediments, in Caribbean coral reef systems.

This student research was retrieved from Physis: Journal of Marine Science VI (Fall 2009)19: 58-65 from CIEE Bonaire.

Coral reefs worldwide are currently jeopardized by anthropogenic factors such as land-based pollution, coastal development, and sediment erosion. In the Caribbean alone, nearly two-thirds of coral reefs have been deemed as threatened. This study investigated the potential negative effects of water quality and eutrophication, Enterococci bacteria (found in human gut), and sedimentation on coral disease, bleaching, and macroalgal growth on the near shore reefs of Bonaire, N.A. Monitoring sites were defined according to their proximity to anthropogenic activity: “more impacted” or “less impacted” (< 200 m and > 200 m from coastal development, respectively). Water samples at 5 m were collected weekly and at 12 m biweekly from each site and tested for nutrient concentrations (NO3, NO2 - , NH4-N, PO4), Most Probable Number of Enterococci bacteria, sedimentation rates, and particle size distributions. Video transects (100 m) were also taken at defined depths and analyzed for live coral cover and diversity, percent disease and bleaching, and macroalgal cover. Data showed elevated NH4-N levels at all sites, Enterococci bacteria present at 3 of the 4 sites (mainly at 5 m), and sediment particle counts showed significant differences among sizes at both depths and between the interaction of size and impact at 12 m. There was also a strong trend of finer grained sediments at high impact sites and coarser grained sediments at low impact sites. Very little overall coral disease (1.105 ± 1.563 % at more impacted sites and 0.400 ± 0.566 % at less impacted sites in 12 m) and bleaching (3.245 ± 0.615 % at more impacted sites and 1.390 ± 1.966 % at less impacted sites in 12 m) was found on the reefs however, neither were present at 5 m. There was significantly more macroalgae at 12 m and a strong trend of more macroalgae at the deeper, more impacted sites. This study suggests that increased anthropogenic activity on Bonaire is contributing to the increased NH4- N levels, Enterococci bacteria presence, and finer particle sediments, which future studies may correlate significant interactions between these parameters and coral disease, bleaching, and macroalgal growth.

This student research was retrieved from Physis: Journal of Marine Science VI (Fall 2009)19: 35-43 from CIEE Bonaire.

Bioindicator species have been used to determine changes in water quality and the effect of pollution at sites of environmental concern. Increasingly degraded water quality throughout the Caribbean is leading marine park managers and scientists to use bioindicator organisms to rapidly detect differences in water chemistry by determining connections between environmental parameters and changes in reef fish communities. This study sought to determine bioindicator prey species that could provide early detection of changes as a result of anthropogenic activities in the coastal waters of Bonaire, N.A. The effects of these parameters on the density and diversity of reef fish species was compared between 4 sites of “more (MI)” and 4 sites of “less (LI)” anthropogenic impact (200 m from of coastal development, respectively). Fish communities were surveyed using a modified version of the AGRRA methodology during the morning and evening. Two 30x2 m transects at 12 m depth were used at each site to survey both prey and predator fish species. Water chemistry including nutrient, bacterial and sedimentation levels were also analyzed to attempt to determine the factor(s) driving the changes. This study revealed significantly greater densities and a higher diversity of prey and predatory fish species at MI sites versus LI sites during the morning and the evening. The species that was found at greatest densities for both LI and MI sites was Stegastes partitus, with significantly more S. partitus at MI sites during both the morning and evening. Thus, S. partitus may be a possible bioindicator of stressors on the reefs in Bonaire. The use of S. partitus as a bioindicator of anthropogenic stress may help increase the effectiveness of marine management protocols in Bonaire and provide a basis for determining bioindicator species for monitoring coastal water quality throughout the Caribbean. None of the water chemistry parameters studied differed between MI and LI sites, therefore, the driver(s) of the differences in prey species (e.g. S. partitus) may be unaccounted for in this study as a result of time lags in the coral reef ecosystem.

This student research was retrieved from Physis: Journal of Marine Science VII (Spring 2010)19: 12-20 from CIEE Bonaire.

One of the most promising solutions to the growing shortage of potable water is the tapping of the oceans through desalination. Until recently the high energy costs of this technology has kept it restricted to oil rich countries in the Middle East. As the need for fresh water has grown and the technology has improved, municipal desalination has slowly expanded out of this region and several plants have been built in the Caribbean and Australia, with more planned. These two regions also house some of the highest concentrations of reefs in the world, and exceedingly little research has been done on the impact of effluent from desalination plants on coral reef ecosystems. Desalination plants release hypersaline water with heightened thermal energy, lowered O2 levels, and a variety of chemical additives. This study used a modified AGRRA benthic survey method to compare coral mortality and reef composition outside the desalination plant to a control site in Bonaire, Dutch Caribbean. The LaMotte Salt Water AquaCulture Test Kit and Hanna Instruments HI 713 Phosphate Low Range kit were used to compare water samples within and between sites. The reef in close proximity to the desalination plant was found to have significantly lower live hard coral, gorgonian, and fire coral cover, and higher sand cover by percent than the control site. The reef also showed significantly higher rates of coral mortality than the control site. The water around the plant was also found to have higher salinity, but lower levels of CO2 and nitrates than the control site. These results suggest that the desalination plant has a negative effect on the surrounding coral reef ecosystem’s health and complexity. These results should give pause to governments planning the development of desalination plants near coral reef environments until more research can be done into this technology’s_environmental_impact.

This student research was retrieved from Physis: Journal of Marine Science IX (Spring 2011)19: 57-63 from CIEE Bonaire.

Damselfish are small herbivores that cultivate algal gardens on coral heads throughout Caribbean reefs. These gardens are used to grow specific types of algae that they can digest easily. However, algal gardens can affect coral both physically and physiologically. In addition to competing with coral for light and space, algal gardens cause coral to spend valuable metabolic energy to remove the algae. This study aimed to determine whether there is a correlation between damselfish density, percent dead coral cover, and coral diversity. A total of thirty-two 20 x 1m belt transects were laid out randomly at a highly impacted and less impacted site. The damselfish density, the number of species, and their size distribution were recorded along with percent dead coral present and coral composition of the substrate. Data were analyzed and compared to deduce whether or not there was any significant evidence that high damselfish numbers are correlated with an increased percentage of dead coral. Although no connection was found between high densities of damselfish and increases in dead coral, it is possible that factors not quantified in this study, such as human impact, could have had an influential role on both damselfish densities and the health of the reef.

This student research was retrieved from Physis: Journal of Marine Science IX (Spring 2011)19: 50-56 from CIEE Bonaire.

Cleaner shrimp are commonly found throughout Caribbean coral reefs and can effectively reduce parasite loads on reef fish resulting in increased fitness of local reef fish populations. The marine cleaner shrimp, Periclemenes pedersoni, most commonly inhabits two coral reef anemones, Condylactis gigantea or Bartholomea annulata, which have different distribution patterns on reefs. C. gigantea resides on hard or rocky substrates with greater relief, whereas B. annulata lives on muddy, sandy substrates or crevices with less relief. Past studies have been done on cleaning by P. pedersoni, yet no research has been done on the effects the differing host anemones may have on cleaning interactions. Using 12 min observation periods between 13:00 -17:00 h on the fringing reef in Bonaire, number of P. pedersoni shrimp, number of clients, species of clients, and time cleaned per client were recorded for C. gigantea and B. annulata anemone cleaning stations. When compared to B. annulata, C. gigantea had significantly more P. pedersoni shrimp, which cleaned a significantly greater number of client fishes. Greater species richness of clients was observed visiting C. gigantea than B. annulata cleaning stations, however there was no difference in time spent cleaning per client. Although protected in Bonaire, aquarium trade collection of C. gigantea throughout the rest of the Caribbean may result in an overall reduction in the number of cleaning interactions occurring on the reef, potentially having detrimental effects on the health of local fish populations.

This student research was retrieved from Physis: Journal of Marine Science IX (Spring 2011)19: 31-37 from CIEE Bonaire.