[Coral-List] New observational paper and the vicious cycle hypothesis

Pawlik, Joseph pawlikj at uncw.edu
Wed Dec 20 08:54:01 EST 2017

Hello Stuart,

Your new paper contains some of the same elements as the "vicious circle hypothesis" for the lack of resilience of Caribbean reefs that my colleagues and I published last year (citation and link below). I believe you are correct that the Caribbean is distinct from other tropical reef areas in having major river discharges into a semi-enclosed sea that acts like a "mixing bowl" --  these river plumes contain huge amounts of dissolved organic carbon (DOC), which is likely much more important than the nutrients (N&P) that they contain, because these nutrients are rapidly used by water column phytoplankton and likely never make it to the reef. 
We propose that the benthic sponge fauna of Caribbean reefs may use river DOC, as well as the DOC liberated by abundant seaweeds that colonized dead coral, to grow and produce fertilizer (N&P) in close proximity to seaweeds, which then enhances further seaweed growth -- this feedback between macroalgae and sponges is the "vicious circle."  The broader context of our hypothesis may explain the much higher (and rapidly increasing) abundance of sponges on Caribbean reefs, their distinctly different morphologies (and the lack of phototrophic species), and the Caribbean-wide patterns of both sponge and seaweed overgrowth of reefs. We also noted the connection between river discharge, dust, microbial activity and recent blooms of floating seaweeds (p. 472).

Pawlik, J.R., Burkepile, D.E., Vega Thurber, R. 2016. A vicious circle? Altered carbon and nutrient cycling may explain the low resilience of Caribbean coral reefs. BioScience, 66: 470-476



Joseph R. Pawlik
Frank Hawkins Kenan Distinguished Professor of Marine Biology
Dept. of Biology and Marine Biology
UNCW Center for Marine Science
5600 Marvin K Moss Lane
Wilmington, NC  28409
Office:(910)962-2377; Cell:(910)232-3579
Website: http://people.uncw.edu/pawlikj/index.html
PDFs: http://people.uncw.edu/pawlikj/pubs2.html
Video Channel: https://www.youtube.com/user/skndiver011
-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Dr Stuart P Wynne
Sent: Wednesday, December 20, 2017 1:57 AM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] New observational paper on regional eutrophication in the Caribbean

Dear Coral-list, 

I would like to draw your attention to a new observational paper on regional eutrophication in the Caribbean region. It is available for free download at:

Since writing this paper, communications from peers have suggested that iron limitation may be the missing part of the puzzle and help explain why algal blooms are more prevalent in the Caribbean than the Indo-pacific region. Carried over to the region in African dust (which is mentioned in my paper only in terms of pathogen transport), iron may facilitate algal blooms in the Caribbean where in the Indo-pacific region its paucity may limit such blooms even in areas with similar nutrient levels. 

I would be interested to hear coral-listers thoughts on this subject. 

Best Regards, 

Stuart Wynne
Former Deputy Director
Department of Fisheries and Marine Resources Government of Anguilla _______________________________________________
Coral-List mailing list
Coral-List at coral.aoml.noaa.gov

More information about the Coral-List mailing list