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Impact Of Increased Nutrient Input On Coral Reefs On Bonaire And Curacao


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My presentation of my internal research during my master program.

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Impact Of Increased Nutrient Input On Coral Reefs On Bonaire And Curacao

  1. 1. Impact of Increased Nutrient Input on Coral Reefs on Bonaire and Curacao By Mark W. Wieggers BSc. July 2007
  2. 2. Outline CH.1 Introduction CH.2 Research Methods CH.3 Results CH.4 Discussion CH.5 Conclusions and Recommendations
  3. 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. 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. 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. 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. 7. Research Methods Site description Monitoring sites on Bonaire.
  8. 8. Research Methods Site description Monitoring sites on Curacao.
  9. 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. 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. 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. 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. 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. 14. Results Coral Cover Bonaire Curacao
  15. 15. Results Ratio between the Cover of Macroalgae and Turf Algae Bonaire Curacao
  16. 16. Results Chlorophyll α Bonaire Curacao
  17. 17. Results Isotope Ratio 15N/14N of Algae Bonaire Curacao
  18. 18. Results Phosphate Bonaire Curacao
  19. 19. Results Total Dissolved Phosphor Bonaire Curacao
  20. 20. Results Nitrite & Nitrate Bonaire Curacao
  21. 21. Results Ammonium Bonaire Curacao
  22. 22. Results Dissolved Inorganic Nitrogen Bonaire Curacao
  23. 23. Results Results of Saint Lucia The average values of the first monitoring round of Saint Lucia:
  24. 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. 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. 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. 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. 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. 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. 30. Special thanks going out to…
  31. 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.