wwguy
01-24-2012, 05:51 PM
For those concerned about the recent decline in the health of Bonaire's reefs, and for those who may be reluctant to concede that a negative change is occurring; I think you will find this report to be both informative and insightful.
A new 137 page report titled Status and Trends of Bonaire’s Reefs: Cause for Grave Concerns (http://www.bmp.org/pdfs/Bonaire_Report_2011_FINAL.pdf) was recently published in PDF format by the Bonaire National Marine Park (BNMP) on this webpage (http://www.bmp.org/publications.html). Based on the title of the report, this would also seem to be the basis for the lecture with the same title scheduled to be given by Ramon de Leon, BNMP Manager, at the CIEE Research Station on Bonaire tomorrow night. If anyone reading this post attended that lecture, I'd appreciate reading a summary or your observations on the lecture and any resulting audience Q&A.
The entire document is only 6MB, so downloading shouldn't be a problem. At a minimum I recommend reading the 7 page Executive Summary on pages 7 to 13.
Paraphrased highlights from the Executive Summary section include:
Unusually warm ocean temperatures surrounding Bonaire during the late summer and fall of 2010 caused 10 to 20 % of corals to bleach.
Bleaching persisted long enough to kill about 10 % of the corals within six months of the event.
This increase in non-coral substrate (i.e. dead coral) increased the area algae can colonize, and the area parrotfish must keep cropped short.
Thus, herbivorous fish (parrotfish and sea urchin) biomass and population densities would have to increase for there to be no incremental change in seaweed (algae) abundance, but they have been steadily declining in recent years.
A decline in parrotfish and sea urchin numbers continues despite the establishment of no-take areas, called Fish Protection Areas (FPAs) and the recent law that completely bans the harvesting of parrotfish.
Damselfishes continue to increase in abundance (except in FPAs) and their aggressive territoriality reduces parrotfish algae-eating activity where they are present.
The declines in herbivory algae eaters resulted in a marked increase in macroalgae.
All research to date indicates that coral health and recruitment declines directly with increases in algal abundance.
To put it a simply as possible: Warm water killed 10% of the coral, which resulted in 10% more surface for the "bad" kind of algae to grow. In a balanced ecosystem bad algae would normally be eaten by parrotfish and urchins. But parrotfish and sea urchin numbers are steadily declining for other reasons, rather than increasing, which further propagates the growth of more bad algae. Further complicating matters, Coralline algae, the "good" algae which has been shown to facilitate coral recruitment, remains at or near unprecedentedly low levels. More bad algae and less good algae results in declining coral health and inhibited coral reproduction... and so the cycle continues in a downward spiral.
Thus the report's Executive Summary conclusion:
"Overall, Bonaire’s coral reefs today are more seriously threatened with collapse than at any time since monitoring began in 1999."
There is a little bit of good new in this report however: Predatory fishes including snappers, groupers, barracuda, grunts and others increased in abundance at the monitored sites. Unfortunately, specific predators known to eat damselfishes showed variable population densities with only a hint of an increase in 2011.
The final paragraph of the executive summary contains this ominous warning:
"The trend of greatest concern is the steady decline in parrotfish abundance despite very recent laws banning their harvest. It is possible that the timing of the bleaching event may have increased the area for algal colonization such that existing herbivores were overwhelmed by rapid algal growth which may negatively affect subsequent herbivory (see discussion in McMahan Chapter 4). If so, this would suggest Bonaire’s coral reefs could be slipping into a feedback loop that could continue and drive the reef towards a coral depleted state (Mumby and Steneck 2008)."
I confess that I haven't read the report in it's entirety yet, but I will soon. The information above is skimmed and/or paraphrased from the Executive Summary section.
I'm very much interested in what you all think about this report, and about what you think we can do to slow, stop, or reverse this downward trend in the health of our beloved reefs. After I've spent some time pondering, I plan to return to this thread to post some examples of what we may be able to do, both individually and collectively, to mitigate or reduce our negative impact on Bonaire's delicate ecosystem.
Ten years ago I brought my teenage son to Bonaire for his first Caribbean dive trip. Next month I'll welcome my first grandson into the world and I'd like to dive with him on Bonaire someday too. I can't help but wonder what Bonaire's reefs, and the other reefs in the world, will be like in another 15 years. Right now the future doesn't seem to be looking very bright.
For now... Happy Diving.
-Roger
A new 137 page report titled Status and Trends of Bonaire’s Reefs: Cause for Grave Concerns (http://www.bmp.org/pdfs/Bonaire_Report_2011_FINAL.pdf) was recently published in PDF format by the Bonaire National Marine Park (BNMP) on this webpage (http://www.bmp.org/publications.html). Based on the title of the report, this would also seem to be the basis for the lecture with the same title scheduled to be given by Ramon de Leon, BNMP Manager, at the CIEE Research Station on Bonaire tomorrow night. If anyone reading this post attended that lecture, I'd appreciate reading a summary or your observations on the lecture and any resulting audience Q&A.
The entire document is only 6MB, so downloading shouldn't be a problem. At a minimum I recommend reading the 7 page Executive Summary on pages 7 to 13.
Paraphrased highlights from the Executive Summary section include:
Unusually warm ocean temperatures surrounding Bonaire during the late summer and fall of 2010 caused 10 to 20 % of corals to bleach.
Bleaching persisted long enough to kill about 10 % of the corals within six months of the event.
This increase in non-coral substrate (i.e. dead coral) increased the area algae can colonize, and the area parrotfish must keep cropped short.
Thus, herbivorous fish (parrotfish and sea urchin) biomass and population densities would have to increase for there to be no incremental change in seaweed (algae) abundance, but they have been steadily declining in recent years.
A decline in parrotfish and sea urchin numbers continues despite the establishment of no-take areas, called Fish Protection Areas (FPAs) and the recent law that completely bans the harvesting of parrotfish.
Damselfishes continue to increase in abundance (except in FPAs) and their aggressive territoriality reduces parrotfish algae-eating activity where they are present.
The declines in herbivory algae eaters resulted in a marked increase in macroalgae.
All research to date indicates that coral health and recruitment declines directly with increases in algal abundance.
To put it a simply as possible: Warm water killed 10% of the coral, which resulted in 10% more surface for the "bad" kind of algae to grow. In a balanced ecosystem bad algae would normally be eaten by parrotfish and urchins. But parrotfish and sea urchin numbers are steadily declining for other reasons, rather than increasing, which further propagates the growth of more bad algae. Further complicating matters, Coralline algae, the "good" algae which has been shown to facilitate coral recruitment, remains at or near unprecedentedly low levels. More bad algae and less good algae results in declining coral health and inhibited coral reproduction... and so the cycle continues in a downward spiral.
Thus the report's Executive Summary conclusion:
"Overall, Bonaire’s coral reefs today are more seriously threatened with collapse than at any time since monitoring began in 1999."
There is a little bit of good new in this report however: Predatory fishes including snappers, groupers, barracuda, grunts and others increased in abundance at the monitored sites. Unfortunately, specific predators known to eat damselfishes showed variable population densities with only a hint of an increase in 2011.
The final paragraph of the executive summary contains this ominous warning:
"The trend of greatest concern is the steady decline in parrotfish abundance despite very recent laws banning their harvest. It is possible that the timing of the bleaching event may have increased the area for algal colonization such that existing herbivores were overwhelmed by rapid algal growth which may negatively affect subsequent herbivory (see discussion in McMahan Chapter 4). If so, this would suggest Bonaire’s coral reefs could be slipping into a feedback loop that could continue and drive the reef towards a coral depleted state (Mumby and Steneck 2008)."
I confess that I haven't read the report in it's entirety yet, but I will soon. The information above is skimmed and/or paraphrased from the Executive Summary section.
I'm very much interested in what you all think about this report, and about what you think we can do to slow, stop, or reverse this downward trend in the health of our beloved reefs. After I've spent some time pondering, I plan to return to this thread to post some examples of what we may be able to do, both individually and collectively, to mitigate or reduce our negative impact on Bonaire's delicate ecosystem.
Ten years ago I brought my teenage son to Bonaire for his first Caribbean dive trip. Next month I'll welcome my first grandson into the world and I'd like to dive with him on Bonaire someday too. I can't help but wonder what Bonaire's reefs, and the other reefs in the world, will be like in another 15 years. Right now the future doesn't seem to be looking very bright.
For now... Happy Diving.
-Roger