The document summarizes research on the impact of increased nutrient input on coral reefs in Bonaire and Curacao. Monitoring sites were established on both islands to analyze coral cover, algae growth, phytoplankton levels, nutrient levels in seawater, and nitrogen isotope ratios in algae. Results showed Curacao had higher macroalgae growth, chlorophyll α levels, and nitrogen levels compared to Bonaire, indicating higher pollution. While some sites on Curacao like harbors had expected high pollution, one resort was surprisingly polluted from an unknown source. There was a correlation found between nitrogen levels and phytoplankton but not between nitrogen and macroalgae growth. The reefs are relatively un

1. Impact of Increased
Nutrient Input on
Coral Reefs on
Bonaire and Curacao
By Mark W. Wieggers BSc.
July 2007

2. Outline
CH.1 Introduction
CH.2 Research Methods
CH.3 Results
CH.4 Discussion
CH.5 Conclusions and Recommendations

3. Introduction
Oceans are important to mankind, 70% of the Earth’s surface is covered by oceans
and 25% of the proteins consumed by mankind is origin from the oceans.
Nevertheless is mankind polluting these same oceans for centuries.
One of the most important ecosystems within the oceans are coral reefs. These reefs
are known for their high biodiversity, the protective use for our coastlines, important
breeding place for fishes and the supply of all kind of natural products. The coral reefs
are also know for being the only change of surviving ice ages for marine life.
Today’s reefs are under pressure by nature but even more by mankind. This research
is focussing on nutrient pollution.

4. Introduction
Coral reefs are often overgrown by algae. The
problem is to point out the cause. On one hand
it can be due overfishing, but on the other
hand it might be due nutrient pollution.
In the figure of Lapointe (1997) is shown the
influence by mankind on the algae growth on
coral reefs.
This research is focused on the nutrient
availability (the y-axis).

5. Introduction
The research questions are:
• Is there a correlation between the nitrogen source and the macroalgae
growth?
Is it possible to see the influence of the local nitrogen sources on the local reefs, and
if yes, how big is the influence? This is very important for policy makers to gain insight
of the effects of environmental policy.
• Is there a correlation between nitrogen source and the phytoplankton levels?
To measure the level of phytoplankton is valuable because it is more reliable than
measuring nitrogen in the sea and the phytoplankton levels are easier to compare
worldwide than nitrogen levels.

6. Research Methods
Site description
The monitoring took place on three islands, Bonaire, Curacao and Saint Lucia. This
research focus mainly on the data of the first year of monitoring on Bonaire and
Curacao and compares the first results of Saint Lucia.
The reefs of Bonaire and Curacao are heavenly influenced by an equal series of
events. In 1982 a massive extinction took place under Echinoidea followed by the
massive extinction of Acropora cervicornis. In 1995 the reefs suffered from a major
bleaching event followed up the next year by yellow blotch disease. In the mid ‘90’s
another massive extinction took place under Acropora palmate which was followed by
a minor bleaching event in 1998. After all this two hurricanes, Lenny (1999) and Ivan
(2004), did destructively damage the reefs.

7. Research Methods
Site description
Monitoring sites
on Bonaire.

8. Research Methods
Site description
Monitoring sites
on Curacao.

9. Research Methods
Analysis of Reef Cover
During the monitoring four videos are made. All four transects are 25 meters long,
but two are made at a depth of 20 feet and two are made at a depth of 60 feet. The
capture of a snapshot of the video is approximately one square meter.
From each of these videos are 15 snapshots taken from equally distance in time. These
snapshots are analyzed using Coral Point Count with Excel extensions (CPCe). CPCe is
developed by the National Coral Reef Institute (NCRI) and the Nova Southeastern
University Oceanographic Center (NSUOC).
CPCe calculates the total coral and algae cover of the reefs.

10. Research Methods
Analysis of Phytoplankton
To analyze the amount of phytoplankton the amount of chlorophyll α was measured in
the seawater. Likewise the four videos the four seawater samples were in pairs at 20
and 60 feet. The samples were take gently at 5 cm form the reef surface.
In the lab was 200 ml filtered of the seawater for the chlorophyll α analysis. The
filters were wrapped in aluminum folio and put on ice. In frozen condition they were
send to the University of Miami for the final analyzing.

11. Research Methods
Analysis of Nutrients
To analyze the amount of the nutrients in the seawater the same four seawater
samples of the analysis of the phytoplankton are used.
In the lab was 100 ml filtered of the seawater for the nutrient analysis. The seawater
samples were directly put on ice and in the dark. In frozen condition they were send to
the University of Maryland for the final analyzing.

12. Research Methods
Analysis of Nitrogen Source
From both depths, 20 and 60 feet, were several species of algae harvested. The
harvested algae was dried for 12 hours at a temperature of 70°C. Afterwards the
algae were grained and send to the McMaster University in Ontario (Canada) for the
final analyzing of the isotope ratio of 15N and 14N.
Living organisms have similar isotope ratios as the sources. From earlier research
(Constanzo et al., 2001) the following categorization is made:
0.0 – 0.5 : natural fixation
1.0 – 3.0 : fertilizer
3.0 – 12.0 : sewage

13. Research Methods
Analysis of Fish Stock
The fish stock was supposed to be measured according the Bohnsack method, a
method also used in comparable research by Lapointe.
Due to the shortage of volunteers on Curacao and the use of a different method on
Bonaire, the available usable data was not enough for this research.

14. Results
Coral Cover
Bonaire Curacao

15. Results
Ratio between the Cover of Macroalgae and Turf Algae
Bonaire Curacao

16. Results
Chlorophyll α
Bonaire Curacao

17. Results
Isotope Ratio 15N/14N of Algae
Bonaire Curacao

18. Results
Phosphate
Bonaire Curacao

19. Results
Total Dissolved Phosphor
Bonaire Curacao

20. Results
Nitrite & Nitrate
Bonaire Curacao

21. Results
Ammonium
Bonaire Curacao

22. Results
Dissolved Inorganic Nitrogen
Bonaire Curacao

23. Results
Results of Saint Lucia
The average values of the first monitoring round of Saint Lucia:

24. Discussion
Comparison between Islands
Curacao is more polluted than Bonaire
looking at the macroalgae growth and the
chlorophyll α levels.
The nitrogen levels a also significant different
between Bonaire and Curacao, the nitrite and
nitrate levels are higher on Curacao than on
Bonaire. On the other hand are the levels of
ammonium and dissolved inorganic nitrogen
which are higher on Bonaire than on Curacao.

25. Discussion
Exceptions of Curacao
Three monitoring sites on Curacao are significantly higher polluted than the others. On
forehand were the Mega Pier and Piscadera Bay expected to be polluted. The Mega
Pier is strongly polluted by the harbour, industry and sewage activities in the bay.
Piscadera Bay is polluted by the broken and leaking pipeline. The results at Piscadera
Bay were nevertheless much worse than expected.
The third site is the Habitat Resort Curacao, which is surprising highly polluted. The
resort has a good name in protecting the environment and limiting their pollution. The
nitrogen isotope ratio results proved the source is not from sewage. What is the
actual source is still a mystery.

26. Discussion
Phytoplankton
The level of phytoplankton is measured by the level of chlorophyll α. Several scientific
researchers agreed in their surveys that the critical value of the chlorophyll α level is
around 0.20 ug/l like Lapointe (2004) described.
Bonaire (0.19 ug/l) is approaching the critical limit where Saint Lucia (0.23 ug/l) and
Curacao (0.26 ug/l) already past the critical limit.

27. Discussion
Nitrogen Source
The sites from Bonaire and Curacao are
compared with sites in the Bahamas, the
USA and Australia in the table on the right.
With the absence of fertilizers on the
Netherlands Antilles, it is assumable that
these sites are a influenced by sewage.

28. Conclusions and Recommendations
The research questions are:
• Is there a correlation between the nitrogen source and the macroalgae
growth?
There is no correlation found between the nitrogen source and the macroalgae
growth.
• Is there a correlation between the nitrogen source and the phytoplankton
levels?
There is a correlation between the nitrogen source and the phytoplankton levels.

29. Conclusions and Recommendations
In general the coral reefs of Bonaire and Curacao are relative unspoiled.
Nevertheless are the levels of chlorophyll α reason for concern. It is very important
to limit the nutrient pollution for keeping the reefs healthy.
Recommended is to include fish monitoring data. At this moment it seems that the
level of macroalgae growth not be triggered by the nutrient pollution.
The expected polluted sites on Curacao were more alarming than expected and an
expected clean site, the Habitat Resort Curacao, was polluted by an unknown source.

30. Special thanks going out to…
WW2BW.org

31. References
• Constanzo, S.D., M.J. O’Donohue, W.C. Dennison, N.R. Loneragan and M. Thomas, 2001. A New Approach for
Detecting and Mapping Sewage Impacts. Marine Pollution Bulleting, volume 42, no. 2.
• Lapointe, B.E., 1997. Nutrient Threshold for Bottom-Up Control of Macroalgal Blooms on Coral Reefs in Jamaica
and Southeast Florida. Limnology and Oceanography, Vol. 42, No. 5, Jul., 1997, 1119-1131.
• Lapointe, B.E., P.J. Barile and W.R. Matzie, 2004. Anthropogenic nutrient enrichment of seagrass and coral reef
communities in the Lower Florida Keys: discrimination of local versus regional nitrogen sources. Journal of
Experimental Marine Biology and Ecology: 308 (2004) 23-58.
• Lapointe, B.E., P.J. Barile, M.J. Wynne and C.S. Yentsch, 2005. Reciprocal Caulerpa Invasion: Mediterranean native
Caulerpa ollivieri in the Bahamas supported by human nitrogen enrichment. Aquatic Invaders, volume 16, number 2.
• Zar, J.H., 1999. Biostatistical Analysis (Fourth Edition). Prentice-Hall, Inc., New Jersey, United States of America.