Green Water Events In The Caribbean: A Case Of Regional Eutrophication Coral Reef Research Ecology

This video explores green water phenomenon in the Caribbean. These 'Green Water Events' are large scale phytoplankton blooms that may last for weeks, and are thought to be caused by nutrient rich water that originates from regional scale river plumes such as the Mississippi, the Amazon or Orinoco. In the example of the Amazon, this productive water is transported up the coast of Brazil and into the Caribbean via north Brazilian current rings.

This nutrient rich water appears to peak in certain years. As the nutrients get 'used up' the phytoplankton die and the water returns to normal. These green water events were first recognised by scientists in the early 2000’s, with events noted in 2009 and again later in 2011, 2014 and 2019. In each case, large areas of water were reported to turn green around islands such as Barbados, British Virgin Islands and Anguilla. Although these events do not themselves cause lasting detrimental effects (and may even temporally promote plankivorous fish and upper level predator numbers), they do signify a much deeper problem.

The green water events suggest a tipping point has been reached in the Caribbean where the oligotrophic conditions needed by coral reefs may be changing in the long term. This tipping point is already apparent when looking at how high macroalgae levels are on some Caribbean coral reefs (with little or no live coral), even when well away from local sources of nutrients. Coral diseases are also on the rise, many of which are caused by cyanobacteria infections that may be promoted by increased nutrient levels.

Solutions to this problem are not clear, but increasing awareness around the scientific community is a key starting point. All too often climate change is thought of as the biggest threat to Caribbean coral reefs, but decreasing water quality has a huge role to play.

Note that the local nutrient enrichment events mentioned in the video may be from chronic sources.

Key References:

Fratantoni D.M. & Richardson P.L. (2006). The evolution and demise of North Brazil Current Rings. Journal of Physical Oceanography 36 . p.1241-1264.

Johns E.M., Muhling B.A., Perez R.C., Muller-Karger F.E., Melo N., Smith R.H., Lamkin J.T., Gerard T.L. & Malca E. (2014). Amazon River water in the northeastern Caribbean Sea and its effect on larval reef fish assemblages during April 2009. Fisheries Oceanography 23. p.472-494.

Jury M.R. (2011). Environmental Influences on Caribbean Fish Catch. International Journal of Oceanography 2011 . pp.11.

Neill C., Chaves J.E., Biggs T., Deegan L.A., Elsenbeer H., Figueiredo R.O., Germer S., Johnson M.S., Lehmann J., Markewitz D. & Piccolo M.C. (2011). Runoff sources and land cover change in the Amazon: an end-member mixing analysis from small watersheds. Biogeochemistry 105 . p.7-18.

Restrepo J.D., Zapata P., Diaz J.M., Garzón-Ferreira J. & Garcia C.B. (2006). Fluvial fluxes into the Caribbean Sea and their impact on coastal ecosystems: The Magdalena River, Colombia. Global and Planetary Change 50. p.33-49.

Suchley A., McField M.D. & Alvarez-Filip L. (2016). Rapidly increasing macroalgal cover not related to herbivorous fishes on Mesoamerican reefs. PeerJ 4 :e2084; DOI 10.7717/peerj.2084

Wiedenmann J., Angelo C.D., Smith E.G., Hunt A.N., Legiret F-E., Postle A.D. & Achterberg E.P. (2013). Nutrient enrichment can increase the susceptibility of reef corals to bleaching. Nature Climate Change 3. p.160-164.

Note:

A full list of references that relate to this video can be found in Wynne S.P. (2017). Observational Evidence of Regional Eutrophication in the Caribbean Sea and Potential Impacts on Coral Reef Ecosystems and their Management in Anguilla, BWI. Anguilla Fisheries and Marine Resources Research Bulletin 8. 22 pages: https://www.thecoralreefresearchhub.c...

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