Anthropogenic stressors such as improper wastewater treatment, dump sites and construction sites can increase nutrient input into marine coastal waters, thereby declining water quality conditions for coral reefs and the surrounding marine environment. Increased nutrient flow in the form of dissolved inorganic nitrogen (DIN) and phosphorous (DIP) is taken up by phytoplankton leading to enhanced algal and cyanobacterial growth which can be measured by an increase of Chlorophyll – a (Chla). As part of the project, “Restoration of Nature and Resilience in the Dutch Caribbean”, water quality monitoring has been implemented on Dutch Caribbean islands to determine local stressors effecting costal water quality. Thus far, the role of land-based nutrient pollution has not been assessed on the Dutch Caribbean Island, Saba. This report analyses the water quality surrounding Saba’s coastal waters with a focus on Chla and nutrients and their relation to anthropogenic stressors on the island. We analysed the distribution of Chla and nutrients spatially and temporally. It is shown that Chla frequently exceeds the 0.2-0.3μM threshold around the harbour and in the two bays: Well’s Bay and Spring Bay/Cove Bay. Temporally, the highest elevated values can be attributed to the hurricane season form August-October. The first round of nutrient sampling from the week of 25-05-2022 shows that DIN exceeds its threshold for Cove Bay and Tent Reef, with ammonium contributing the largest to the DIN content. In future, attention needs to be paid to the DIN and DIP balance since high elevated ratios have been found at Tent Reef, possibly indicating DIP - limitation. With only one week of nutrient data available, no correlation between Chla and nutrients could be made. Overall, sites such as Tent Reef, Well’s Bay, and Spring Bay/Cove Bay demonstrate the most severely declining water quality based on frequently elevated Chla and nutrient levels. Further research on water quality data surrounding Saba is necessary to confirm these findings and to address stressors contributing to decreased water quality.
Resource recovery and reuse from domestic wastewater has become an important subject for the current development of sanitation technologies and infrastructures. Different technologies are available and combined into sanitation concepts, with different performances. This study provides a methodological approach to evaluate the sustainability of these sanitation concepts with focus on resource recovery and reuse. St. Eustatius, a small tropical island in the Caribbean, was used as a case study for the evaluation. Three source separation-communityon-site and two combined sewerage island-scale concepts were selected and compared in terms of environmental (net energy use, nutrient recovery/reuse, BOD/COD, pathogens, and GHG emission, land use), economic (CAPEX and OPEX), social cultural (acceptance, required competences and education), and technological (flexibility/adaptability, reliability/continuity of service) indicators. The best performing concept, is the application of Upflow Anaerobic Sludge Bed (UASB) and Trickling Filter (TF) at island level for combined domestic wastewater treatment with subsequent reuse in agriculture. Its overall average normalised score across the four categories (i.e., average of average per category) is about 15% (0.85) higher than the values of the remaining systems and with a score of 0.73 (conventional activated sludge – centralised level), 0.77 (UASB-septic tank (ST)), 0.76 (UASB-TF - community level), and 0.75 (ST - household level). The higher score of the UASB-TF at community
level is mainly due to much better performance in the environmental and economic categories. In conclusion, the case study provides a methodological approach that can support urban planning and decision-making in selecting more sustainable sanitation concepts, allowing resource recovery and reuse in small island context or in other contexts.
Raw data of a comparative nutrient monitoring program that included seasonal sampling for nutrients (ammonium, nitrate, DIN, SRP, TDN, TDP), phytoplankton biomass (Chl a), stable nitrogen isotopes (!15N) 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.
This data resulted in:
- a report: Lapointe and Mallin, 2011, Nutrient Enrichment and Eutrophication on Fringing Coral Reefs of Bonaire and Curaçao, Netherlands Antilles
- a student report: Wieggers, M., 2007, Impact of Increased Nutrient Input on Coral Reefs on Bonaire and Curacao
Please contact the DCBD administrator for access to the data.
A follow-up of this study took place on Bonaire between 2011 and 2013:
- Slijkerman et al., 2013, Water quality of the coastal zone of Bonaire Results field monitoring 2011-2013
- Slijkerman et al., 2012, Water quality monitoring Bonaire. Identification of indicators, methods and locations
- Slijkerman et al., 2012, Water quality monitoring Bonaire. Results monitoring November 2011 and recommendations for future research
Marine organism are often kept, cultured, and experimented on in running seawater aquaria. However, surprisingly little attention is given to the nutrient composition of the water owing through these systems, which is generally assumed to equal
in situ conditions, but may change due to the presence of biofouling organisms. Signi cantly lower bacterial abundances and higher inorganic nitrogen species (nitrate, nitrite, and ammonium) were measured in aquarium water when biofouling organisms were present within a 7-year old inlet pipe feeding a tropical reef running seawater aquaria system, compared with aquarium water fed by a new, biofouling-free inlet pipe. These water quality changes are indicative of the feeding activity and waste production of the suspension- and lter-feeding communities found in the old pipe, which included sponges, bivalves, barnacles, and ascidians. To illustrate the physiological consequences of these water quality changes on a model organism kept in the aquaria system, we investigated the in uence of the presence and absence of the biofouling community on the functioning of the lter-feeding sponge Halisarca caerulea, by determining its choanocyte ( lter cell) proliferation rates. We found a 34% increase in choanocyte proliferation rates following the replacement of the inlet pipe (i.e., removal of the biofouling community). This indicates that the physiological functioning of the sponge was compromised due to suboptimal food conditions within the aquarium resulting from the presence of the biofouling organisms in the inlet pipe. This study has implications for the husbandry and performance of experiments with marine organisms in running seawater aquaria systems. Inlet pipes should be checked regularly, and replaced if necessary, in order to avoid excessive biofouling and to approach in situ water quality.
A reoccurring problem facing a majority of the coral reefs in the Caribbean for the past few decades has been the fear of a changing community structure from primarily reef-building corals to algal dominance. A shift in such ecosystems could inhibit coral growth and recruitment, eventually killing corals and lowering the diversity of fish in the area. Recent developments in agriculture and technology have advanced the dispersal of various inorganic nutrients into water systems, where excess nitrogen or phosphorous levels may lead to an increase in algal photosynthesis and thus growth. For my study I looked at relationships between algal growth and nutrient levels in seawater, specifically ammonia and nitrates + nitrites. Using photography and underwater transects I looked for differences in the amount of algae at sites with high or low nutrient levels as measured in March 2006 by the Bonaire Marine Park (BMP). The site with the highest nitrate + nitrite levels had a mean algal cover of 30.6% (std. dev. 30.4), which was not statistically different from the site with lowest concentrations (mean algal cover = 22.9%, std. dev. = 23.1). Algal cover was highest at 18 Palms (mean = 38.6% std. dev. = 39.5), where the lowest ammonia concentration was found. This research showed that nutrient levels did not influence the percent algal cover at my sites. Possible reasons for these findings are discussed.
Most hard corals require seawater with low nutrients and sediment loads to thrive. Unfortunately, on a global scale, increases in both are currently occurring due to poor coastal zone management practices. This causes damage that is often fatal to reef building corals. Plants living in near shore areas provide natural filters for sediments and nutrients, and recently managers have been harnessing the filtering capabilities of plants to protect aquatic ecosystems. In the marine environment, mangroves provide protection by filtering sediments and absorbing nutrients from runoff before it reaches coral reefs. Ritterocereus griseus, a common cactus species on Bonaire, N.A., has similar capabilities in the terrestrial realm. The following hypotheses were tested regarding cactus fences in Bonaire: smaller amounts of phosphate and sediments would be transported, and lower amounts of runoff would be collected down-slope of plots with cactus fences than plots without cactus fences. Experimental plots with cactus fences were compared to control plots without cacti. To construct plots, steel guides were used to direct simulated rainfall across plots with and without cactus fences into a collection cup at the base of the set-up. This study determined that R. griseus reduces the volumes of runoff and the amount of sediment and nutrients transported down-slope. The use of cactus fences could increase the resilience on Bonaire’s reefs by decreasing sediment and nutrient inputs to near shore waters and are a sustainable resource on the small island.
Beach environments are considered nutrient poor systems that support limited abundances of life due to the lack of attainable nutrients. Since the surrounding environment is nutrient limited, plants and organisms residing in sandy beach communities take advantage of available nutrients whenever possible, for example, nests laid on the beach. This study assessed whether nesting hawksbill sea turtles (Eretmochelys imbricata) are transporters of nutrients from ocean systems to nutrient-poor beaches of Bonaire, N.A. It was hypothesized that nitrogen (N) and phosphorus (P) levels would be elevated, infaunal organisms would be more abundant, and plant cover would be higher in nest plots compared to areas without nests. To determine the input of nutrients from nesting and the potential effects of nutrient enrichment on the plants and infauna, five experimental arrays, including nest, mechanically disturbed (no nutrient addition), and undisturbed treatments were sampled from September to October 2009 on Klein Bonaire. Five days following hatching events, sediment cores were taken to assess concentrations of N and P, as well as to determine the abundance of infauna. Plant percent cover was also determined for each plot. Nutrients did not differ significantly among plot type, with both N and P consistently at low concentrations. For all nest plots, 2.5 X more taxonomic groups, including known predators, were detected than in undisturbed or mechanically disturbed plots. No plants were found in any plot type for the duration of the study. This study suggests that hawksbill sea turtle nests are not strong drivers of coastal community structure in Bonaire. It is believed that the CaCO3 composition of the sand and the limestone base of the island do not allow for nutrient retention and thus excess nutrients are not available for exploitation by beach plants or infauna.
Trying to understand the extent to which anthropogenic stressors impact coral reefs globally has led to an increase in studies which analyze the effects of nutrient enrichment on the frequency and severity of coral disease. Bonaire, Dutch Caribbean currently has no sewage treatment facility in place, resulting in the percolation of wastewater to the surrounding coastal marine environment. On the reefs near resorts, there is a large volume of groundwater used and subsequently discharged into the ocean. As a result, the reefs directly in front of major resorts are likely to have higher disease levels than reefs without resorts nearby. The goal of this study was to evaluate the difference in prevalence of coral disease between sites located in close proximity to groundwater discharge and sites located further away. In order to achieve this objective, six sites with varying gradients of exposure to sewage discharge were surveyed by laying down 1 m x 30 m transect belts parallel to the shore at 6 m, 12 m and 18 m depths. During each survey, nutrient enrichment, macroalgal cover, water depth and coral colonies displaying signs of disease were recorded. Water quality was assessed using a number of parameters including nutrients (ammonium, ammonia, phosphate and dissolved oxygen), Enterococci bacteria and sedimentation. At sites closer to resorts there were higher nutrient levels and percent cover macroalgae, however sedimentation rates and mean percent coral disease frequency were highest at medium impacted sites. Low impacted sites had a greater presence of coral disease at shallower depths, compared to high impacted sites. This data will be used to illustrate a relationship between coral disease and anthropogenic stressors and provide a baseline for future studies.
This student research was retrieved from Physis: Journal of Marine Science IX (Spring 2011)19: 1-11 from CIEE Bonaire.
The creation of harbours through dredging combined with boat maintenance and waste is known to increase nutrients and sedimentation within coastal waters causing the degradation of nearby coral reefs. Winds and currents play a large role in the transportation of nutrients and sediments. This study investigated the distribution of nutrients in water surrounding Harbour Village Marina in Bonaire, Dutch Caribbean, as well as the extent to which the harbour affects adjacent coral reefs. Water samples were collected at increasing distances from the entrance to the harbour and were tested for nutrients. Percent coral cover was estimated using 10 m line-intercept transects. By noting the wind direction and currents when collecting data, it was determined that both the surface and bottom currents flow predominantly north. Results show that current plays a large role in nutrient distribution, but the effects on coral cover are unknown. Coral cover was also much lower north of the harbour in the direction of current flow compared to the south. This study increases the knowledge on nutrient distribution and coral cover as well as the impact harbours have on surrounding reefs. The results can be used for management efforts to help maintain coral reef health, and to keep nutrient levels low during the creation and upkeep of small harbours.
The island of Bonaire has significant contamination from anthropogenic sources such as sewage and landfills, which can cause excess nutrients in groundwater that will eventually enter the ocean. Nutrients have been suggested to increase macroalgal growth. The amount of nutrients and abundance of herbivores play a key role in maintaining a healthy coral dominated reef system. The major objective of this study was to determine the health of Bonaire's reefs by assessing various bioindicators, evaluating bioacummulation of macroalgae, assessing the biocontrol mechanisms, and determining the presence of phase shifts. This study looked at the relationship of herbivorous fish, nitrogen content and abundance of macroalgae to make inferences regarding the overall health of the reef. Two study sites, Kas di Arte and Something Special, were chosen for research over the course of four weeks. Data collection included abundance of herbivorous fish, substrate composition and nutrient level in water and algae samples. No inferences could be determined from the nutrient tests due to the varying concentrations found in both water and macroalgae. The herbivorous fish abundance and macroalgae were found to be inversely proportional. This study is important to determine whether herbivorous fish or nutrient input control phase shifts on Bonaire's reefs and can aid in identifying similar issues in reefs all over the Caribbean.
This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 58-65 from CIEE Bonaire.