Nutrient Monitoring program finalized
A second year of monitoring has now been completed in Bonaire and Curaçao. The results of the laboratory analysis of the N and P values and the Cholorophyll-a levels of the water samples are now all in, as well as the stable Nitrogen isotope ratio of the algae tissues that were collected. In the coming month these results will be analyzed and a final report will be produced, hopefully by October of this year. The intention is to present the final results and conclusions at the Gulf & Caribbean Fisheries Institute (GCFI) meeting on Guadeloupe in November this year as part of the special session of coastal impacts on marine resources. The yearly meetings of the GCFI are a platform not only for fisheries research but also for Marine Protected Area management research. A small working group of experts and interested scientists has been formed to discuss the possibilities during the workshop to develop this type of monitoring into a regional water quality monitoring effort.
The preliminary report on
the first year of nutrient monitoring that was prepared by Mark Wieggers as
part of his internship working for his master's degree at the University of
Utrecht, has now finally been posted on this website and can be downloaded from
the literature index or click on the link here:
download preliminary report, pdf 2MB
Coral Reefs of Bonaire and Curacao on the brink
Workshop in Bonaire presents preliminary results of one year of nutrient monitoring
|Brian Lapointe showing nutrient indicator algae at Lagun, Bonaire, one of the monitoring sites.|
July 1, 2007. The reefs of Curaçao and Bonaire are on the brink of going the same way as the reefs of Jamaica or Florida, where sea weeds have taken over and are replacing corals. A number of locations in Curaçao already have 50% or more of the bottom covered by so-called macro-algae or sea weeds, and point to land-based sources of pollution. These were some of the conclusions at a meeting in Bonaire where the preliminary results of a year long monitoring program on Bonaire and Curaçao were discussed. The program looked at nutrient concentrations and algae suspended in the water on the reefs of the two islands. It also looked at nitrogen isotope signatures in algae tissues indicating the relative importance of sewage as a source of nitrogen.
The nutrient monitoring project is an initiative of the NACRI, or Netherlands Antilles Coral Reef Initiative, and organized by the department of Nature and Environment of the Netherlands Antilles (MINA), and Stinapa Bonaire, together with Reef Care Curaçao, the Section Environmental Management in Bonaire (DROB-MNB), and the Agriculture and Fisheries Service (LVV) in Curaçao. The Bonaire meeting brought together many people involved in the monitoring work on both islands, as well as representatives of various island government services involved with water treatment and marine conservation. Also present were representatives of the Soufriere Marine Management Area (SMMA) in St.Lucia, which has recently joined the project, and representatives of St. Maarten and Martinique, who were also interested in this work.
|Chlorophyll-A concentrations at various locations in Bonaire and Curacao. Red hjorizontal line represents threshold value below which reefs are considered healthy.|
The results presented at
the meeting still need further analysis. However, it was clear that on average
Curaçao had up to five times more seaweeds on the reef than Bonaire as
well as having more phytoplankton (algae suspended in the water). In three places
in Curaçao there were indications of nutrients originating from sewage,
i.e., down current from the harbor mouth, outside the mouth of the Piscadera
Bay, and inside the Spanish Water. The reefs of Curaçao are clearly more
polluted than those of Bonaire.
However, disconcertingly high concentrations of ammonia were found in Bonaire, possibly linked with the extremely high nutrient concentrations found in the salt ponds. At the Lagun sampling site very high plankton values were found in the water, as well as a clear sewage signature in the seaweeds growing there. This may be due to leachate from the landfill reaching the water.
In general both Bonaire and Curacao are at or just above the nutrient thresholds that would lead to degradation of the coral reefs. The higher plankton and seaweed values in Curacao indicate higher land-based nutrient loads. Bonaire is not far behind however, and there is a clear and urgent need to prevent nutrient rich waste water from reaching the reefs in order to prevent further reef degradation; careful policy and management are required.
|The ratio between macro and turg algae on the coral reefs of Bonaire and Curaçao. A higher ratio means more macro-algae (or seaweeds) on the reef.|
Continued monitoring of nutrient levels and pollution indicators in the coastal waters, but also in the groundwater, on both islands, is of great importance for the future of our coral reefs.
The nutrient monitoring
program was funded by the American National Fish and Wildlife Foundation the
United Nations Environmental Program and the White Water to Blue water initiative,
and made possible by the help of many dedicated volunteers and the support of
the diveshops on both islands, Captain Don’s Habitat in Bonaire, and Habitat
The presentations given at the workshop in Bonire can be downloaded here:
Reef Nutrient Monitoring Bonaire and Curaçao
First round successfully concluded.
|Brian Lapointe and volunteers in Bonaire preparing for a dive at Angel City.|
March 28, 2006. Last week the first round of nutrient monitoring on the reefs of Bonaire and Curaçao was concluded with a last dive at Watamula Reef in Curaçao. A total of twenty sites, ten in Bonaire and ten in Curaçao, were visited over a nineteen day period. On each site video transects were recorded, water samples taken, and various algae samples collected, both at 60 ft and at 20 ft depths. A total of eighty water samples and more than 220 algae samples were subsequently processed and carried to the US by Brian Lapointe to be analyzed in specialized labs.. The results of this analysis are expected in about a month time, when a start can be made with interpreting the data.
Meanwhile, some general preliminary impressions were formed with regard to nutrient impact on the reefs of Bonaire and Curaçao. First of all it became clear that there definitely is an impact of nutrient pollution on some of the reefs on both islands. Compared to many other places in the Caribbean, the reefs of Curacao and Bonaire still generally look to be in good condition, but signs of nutrient pollution were seen on both islands. On average the reefs in Bonaire were less impacted than those of Curacao, but both islands had some sites that are a cause for serious concern. One particular site in Bonaire showed blooms of various species of cyanobacteria (blue-green algae) including the toxic Lyngbia (implicated in the development of disfiguring fibropapillomas in sea turtles), and elevated incidence of coral diseases and corals killed over the past few years. In Curaçao several sites such as Caracas Bay and Piscadera had many dead corals and presented luxurious growth of various macro-algae such as Lobophora, Halimeda, and Dictyota. Some sites in the vicinity of resort areas showed alarmingly luxurious growth of Dictyota and relatively high incidence of Black Band disease. Sites within the town area both in Bonaire and Curacao had clear nutrient indicator macro-algae growing on the rocks in the surf zone, and there is no question that they are being impacted by nutrient pollution, but the other sites will have to await the lab results before any clear conclusions can be drawn.
The specialized laboratory analysis will test for very low levels of dissolved inorganic nitrogen and phosphorus, and will provide a measure of the amount of phytoplankton (floating one-celled algae) in the water. The collected algae samples will yield ratios of nitrogen isotopes in the algae tissues, indicating the source(s) of the nitrogen. Natural sources of nitrogen, fertilizer nitrogen, and sewage nitrogen all have different signatures. When luxurious algae growth coincides with a signature of fertilizer or sewage nitrogen there is clear cause for concern.
|Frank van Slobbe and Ramon de Leon, coordinators of the Bonaire nutrient monitoring effort, familiarizing themselves with a Dissolved Oxygen meter.|
Any conclusions, even after the lab results come in, must also take into the account the possible seasonality of nutrient sources, e.g. increased run-off or mixing of ground water with sea water because of the rainy season. That is why this is only the first round of monitoring. It will be repeated quarterly for a year. Over the past couple of weeks volunteers in Bonaire and Curaçao had the opportunity to observe how the sampling is done, how the water samples must be carefully filtered after the dive, avoiding any contamination, and how to distinguish various species of algae. They will now continue the monitoring every three months to produce a complete picture of the nutrient situation of the reefs from which clear conclusions and recommendations can be drawn.
To learn more about nutrients, macro algae and coral reefs you can download the following:
Presentation given by Dr. Brian Lapointe in Bonaire and Curacao (Powerpoint 8 MB)
Lapointe, Brian E. and Katie Thacker: “Community based Water Quality and
Coral Reef Monitoring in the Negril Marine Park, Jamaica: Land-based nutrient
inputs and their ecological consequences” (PDF, 5 MB)
Brian E. 1997: Nutrient thresholds for bottom-up control of macroalgal blooms
on coral reefs in Jamaica and Southeast Florida