The economy of Bonaire is highly dependent on tourism. Tourists are drawn to Bonaire because of the beautiful nature and biodiversity in the coastal ecosystems, e.g, mangrove forests, seagrass meadows, coral reefs. Therefore, it is important to protect these coastal ecosystems. Currently, eutrophication and pollution are serious threats to Bonaire’s mangrove forests and seagrass meadows through terrestrial run-off and influx of Sargassum. Seagrasses are known to be sensitive to local environmental changes by bioaccumulation of chemicals and nutrients through absorption in their tissues. In this study, we used turtle grass (Thalassia testudinum) as a bioindicator of spatial and temporal variation in eutrophication and pollution in five different bays on Bonaire. We found that T. testudinum is a good bioindicator of eutrophication and pollution. Analysis of stable isotope signatures (δ13C, δ15N), nutrient (%N, %P, %S) and trace metal content (%As, %Cd, %Co, %Fe, %Mn, and %Ni) in T. testudinum leaf samples
revealed that Lagun was the most eutrophic and polluted bay on Bonaire. The high eutrophic and polluted state in Lagun is mainly due to a nearby landfill, large catchment area, and influxes of pelagic Sargassum spp.. In Lac Bay, higher sulfide stress was observed in T. testudinum leaf tissues in 2019 compared to 2015, which may have hindered the uptake of N and P by T. testudinum. The difference in sulfide stress between 2015 and 2019 is due to the massive influx of Sargassum that occurred in 2018. However, we suggest a possible recovery given better uptake of N and P and lower sulfur content in T. testudinum leaf tissues in 2022. This may indicate less sulfide stress in 2022 compared to 2019. In Lac Bay in 2022, biochemical content of T. testudinum leaf tissues collected at fixed sampling sites where the direct cumulative effect of Sargassum influxes was assumed to be highest (i.e., west of Lac Bay), were similar to tissues collected in areas with no or intermediate direct impact of Sargassum. This may also suggest recovery of T. testudinum that has survived the most severe influx in 2018. We showed that Bonaire’s coastal ecosystems are threatened by eutrophication and pollution through land-based run-off and the influx of pelagic Sargassum. Hence, we want to encourage the local government with this study that nature restoration measures need to be taken immediately to protect their coastal ecosystems.
A B S T R A C T
Coral-associated invertebrates contribute much to the biodiversity of Caribbean coral reefs. Although the nature
of their symbiotic relation is usually not fully understood, they can cause damage to their hosts, especially when
they occur in high densities. The abundance of seven groups of coral-associated invertebrates was investigated on
reefs along the leeward side of Curaçao, southern Caribbean. In particular, coral barnacles (Pyrgomatidae),
boring mussels (Mytilidae: Leiosolenus spp.), gall crabs (Cryptochiridae), and Christmas tree worms (Serpulidae:
Spirobranchus spp.) were recorded together with their host corals by means of a photo survey at four depths (5,
10, 15, 20 m) and across seven sites with high and five sites with low eutrophication values (based on δ15N
isotope data). Feather duster worms (Sabellidae: Anamobaea), coral blennies (Chaenopsidae: Acanthemblemaria),
and worm snails (Vermetidae: Petaloconchus) were insufficiently abundant for thorough quantitative analyses.
The results show a decrease in the number of barnacles and Christmas tree worms per host over depth, which
could be related to the availability of their host corals. Sites with high δ15N values show a higher abundance of
barnacles and Christmas tree worms per host than sites with low values. This indicates that eutrophication could
be favourable for these filter feeding organisms but when their densities become too high, they tend to overgrow
their hosts and may become a threat to them.
The research aimed to recollect specimens from Curaçao of the genus Halosbaena belonging to the rare crustacean order Thermosbaenacea, a genus with a relictual Tethyan distribution. It resulted in recording the apparent extinction of the entire, species-rich, subterranean fauna on the island that had occurred within a period of 43 years up to 2015. The composition of the groundwater fauna on Curaçao was sampled in 2015 for comparison with sampling undertake 43 years previously. Despite using the same sampling methods previously used and comprehensive coverage of the available sampling sites, no stygofauna specimen was collected from sampling in 2015 in contrast to more than 50 species collected from the initial sampling in 1973. It is hypothesised that this faunal extinction was associated with the oil industry, but it is unclear whether it resulted from petroleum pollution of groundwater drawdown or recharge. This record of the extinction of an entire ecosystem, rather than merely some members of it, is perhaps unique, but is concerning amongst the more diffuse extinction events happening globally.
The anthropogenic effect of terrestrial run-off on coral reef ecosystems is a topic of high concern to marine ecologists. In the Caribbean, coral cover is decreasing at an alarming rate, and phase shifts to an algae-dominated reef have been documented. Studies have shown a correlation between densely populated coastal communities and high levels of substances known to be detrimental to marine ecosystems. This study focuses on two contaminants common in waters affected by terrestrial run-off: fine sediment and UV reactive hydrocarbons. Fine sediment cannot be removed easily from the tissues of corals and can prevent corals from receiving enough light. UV reactive hydrocarbons can embed themselves in tissue membranes and cause oxidative damage upon exposure to UV light. The presence and effects of these contaminants were determined near a drain in Bonaire, Dutch Caribbean. The percent distribution of sediment grain sizes was determined at increasing distances from the drain. The results revealed that the percentage of fine sediment is highest close to the drain and decreases with increasing distance from it. The presence of UV reactive hydrocarbons was determined using bioassays of Artemia sp. The results of the bioassays suggest that run-off from the drain contains UV reactive hydrocarbons. The effect of these contaminants on the abundance of organisms in benthic communities was analyzed using endobenthos technique but results were inconclusive. This study determined the presence of fine sediment and UV reactive hydrocarbons due to a point source of terrestrial run-off.
Runoff and sewage discharge present serious consequences if left unchecked in coral reef ecosystems. Eutrophication and the introduction of harmful chemicals to the environment can lead to the destruction of coral reefs. Phosphates and polycyclic aromatic hydrocarbons (PAHs) are well known components of runoff that are detrimental to the reef ecosystem. As such, the ability to monitor the concentration and spatial distribution of these chemicals is of great interest. These pollutants may be detected using bioindicators. Bioindicators are organisms that can be used to monitor the health of an ecosystem. In this study, sponges were assessed as bioindicators for phosphate and PAHs in coral reef environments. Holopsamma helwigi, Ircinia strobilina, and Pseudoceratina crassa are common Leuconoid sponges that were tested for pollutant contaminations using fluorometric analysis. The sponges were collected along a transect spanning the northern coast of Kralendijk, Bonaire. A known runoff site at ‘Kas di Arte’ (12° 9' 19.9362" N, 68° 16' 44.5434" W) was selected as the starting point for the transect. The sponges bioaccumulated both phosphates and PAH compounds. Concentrations of the pollutants were not found to decrease as the distance from the runoff site increased suggesting that sponges assessed here are not capable of showing short-term variation in spatial trends of pollutant concentration. In order to better understand how the sponges accumulate pollutants, a thorough exploration of the kinetics of pollution bioaccumulation should be pursued in future studies.
This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 45-51 from CIEE Bonaire.
Phototoxic polycyclic aromatic hydrocarbons (PAHs) have been welldocumented as major marine pollutants. While PAHs are known to have negative ecological effects, the spread of point-source PAHs into coral reefs is poorly understood. This study focuses on a potential source of marine PAH contamination from a drain into a coral reef in Bonaire, Dutch Caribbean. PAHs were believed to be detected outside of the drain between October and November 2013, providing incentive for continued monitoring of PAH presence. Insight from this investigation is important not only to the general understanding of point-source marine pollution pathways, but holds implications for drain management strategies. Water samples from sites of varying distances from the drain were analyzed for UV-reactive toxicity using two Artemia sp. bioassays. Results from the bioassays indicated that PAH presence was undetectable, and that there was no relationship between distance from the drain and UVreactive toxicity. It was concluded that sediment dispersion and marine organism bioaccumulation likely accounted for the apparent temporal discrepancy in PAH presence. Field observations displayed noticeable coral reef degradation, which was assumed to be largely caused by factors other than PAH pollution. Despite the lack of evidence for current PAH presence, observations of poor reef health outside of the drain suggest that further studies and management strategies be considered for the drain and cement trough.
Baseline data on anthropogenic seafloor debris contamination in the year 2000 is provided for 24 submersible video transects at depths of 80-900 m, off the Dutch ABC-islands (Aruba, Bonaire, Curaçao), in the southeastern Caribbean Sea. In total, 202 objects were documented from a combined 21,184 m of transect, ranging from sandy lower island-slope to rocky upper island-slope habitat. Debris densities differed significantly with depth. Highest debris accumulation (0.459 items 100 m(-2) or 4590 items per km(2)) occurred at depths of 300-600 m on more shallow-sloping (20-30°) sand and silt bottoms. The overall average debris density was 0.27 objects per 100 m(2) (or 2700 items per km(2)), which is an order of magnitude higher than most other deepwater debris studies. What we describe may be representative for other small, populated, steep volcanic Caribbean islands. Food and beverage-related items were the single largest usage category identified (44% of objects; mostly glass beverage bottles).
Land-based nutrient pollution is a major stressor on coral reef communities around the Caribbean region and globally. To assess the status of nutrient enrichment and eutrophication on Bonaire and Curacao’s coral reefs, we conducted a comparative nutrient monitoring program that included seasonal sampling for nutrients (ammonium, nitrate, DIN, SRP, TDN, TDP), phytoplankton biomass (Chl a), stable nitrogen isotopes (ð15N) in reef macroalgae, and biotic cover (point count analysis of video transect data) of shallow and deep reef sites between March 2006 and June 2008. Ammonium dominated the DIN pool on both islands and the highest concentrations (~10 µM) occurred on Bonaire’s reef sites adjacent to the Cargill salt ponds. DIN concentrations averaged > 1 µM on both shallow and deep reefs of both islands, indicating that these reefs are now above the DIN threshold noted to support expansion of algal turf, macroalgae and coral diseases. SRP concentrations averaged ~ 0.1 µM on both islands, a level that also represents the SRP threshold for eutrophication on coral reefs. DON and DOP dominated the TDN and TDP pools; TDN/TDP ratios averaged 52 on Bonaire and 45 on Curacao, indicating strong P-limitation of algal growth. Mean Chl a concentrations were higher on Curacao (0.25 µg/l) than Bonaire (0.19 µg/l) and the highest Chl a concentrations on both islands occurred on reefs adjacent to urbanized, nutrient enriched areas. In contrast, low Chl a values of ~ 0.05-0.1 µg/l occurred at the upstream reef sites and the offshore reference site, underscoring the importance of land-based nutrient enrichment to microbial growth and eutrophication on fringing reefs of both islands. The highest macroalgal ð15N values (> + 3 ‰) occurred at the MegaPier and Piscadera Bay on Curacao, which reflects the highest watershed sewage nitrogen inputs of all reef sites in the study. The lower ð15N (< + 2 ‰) values at the other reef sites reflect lower levels of sewage treatment as well as contributions from other nitrogen sources (nitrogen fixation, atmospheric inputs) that have lower source ð15N values. Reefs on both islands were dominated (~ 75 % cover) by benthic algae but showed distinct differences in algal composition; Bonaire’s reefs had high cover of turf and low cover of macroalgae compared to the opposite pattern on Curacao. Our results suggest that the recent expansion of benthic algae and loss of coral cover on reefs in Bonaire and Curacao are not simply the result of top-down human pressures (e.g., overfishing) alone, but also reflect strong bottom-up effects from land-based nutrient pollution.
The data of the study can be found here
In 2010 a petrochemical fire took place at the BOPEC oil terminals on Bonaire. These facilities are located on the shores of the Goto lake, a legally protected RAMSAR wetland and important flamingo foraging area. Before the fire, daily flamingo counts averaged approximately 400 birds that used the area to feed on Artemia (brine shrimp) and Ephydra (brine fly larvae). Immediately after the fire, flamingo densities plummeted to nearly none and have not recovered. A large amount of fire retardants were used to combat the fire, and were hypothesised to be a potential cause for the flamingo declines. Our analyses of 15 years of baseline flamingo monitoring data show that rainfall does influence flamingo densities but only on the short-term and steering seasonal dynamics of flamingos. Therefore the rainfall event/change in the rainfall regime cannot account for lasting absence of flamingos. Nearby control lakes that were not affected by the fire showed no lasting reduction in flamingo densities, but instead an increase due to the birds no longer feeding in Goto.
In 2012, we measured the concentrations of polycyclic aromatic hydrocarbons (PAHs) and perfluorinated compounds (PFCs, which includes PFOS) in Goto and control-lake waters and conducted additional chemical screening (fingerprinting) of sediments and biota. These measurements showed both lasting elevated levels of PFCs, in water, sediments and biota (fish) and lowered food-species concentrations in Goto as compared to control areas. Based on calculated Risk Quotients combined with the chronic exposure, for the documented PFOS levels, toxicological effects on benthic organisms such as Artemia and Ephydra are likely. Nevertheless additional impact by other associated retardant toxicant is also probable. Goto was found to be chemically different based on GC*GC chemical fingerprinting indicative of elevated Butylated Hydroxytoluene (BHT) concentrations, a compound used in petrochemical industries as a solvent.
In conclusion, our results demonstrate a close link between the 2010 Bopec fires and the subsequent abandonment of the adjacent Goto lake by foraging flamingos. Compared to nearby control lakes, Goto was found to have elevated (and toxic) concentrations of PFCs and associated low food species concentrations. Therefore, our results suggest that the lasting abandonment of the lake by flamingos after the fire have been due to the drastically low food-species densities as likely caused by toxic ecosystem effects resulting from retardants released into the environment while combatting the fires.
In a recent dissertation (Vermeij, 2002) it is stated that with no action by the Curaçao government, the coral reefs will have disappeared in 30 years. To answer the question "What can be done?", this document focuses on the following causes of coral decline:
- Inorganic and organic pollution
- Oil pollution
- Heavy metals and pesticides