[Coral-List] vicious cycle hypothesis, rivers, and enclosed seas (Coral-List Digest, Vol 112, Issue 12 -)

Storlazzi, Curt cstorlazzi at usgs.gov
Wed Dec 20 13:17:47 EST 2017


This thread by Stuart and Joseph regarding high DOC loading to a relatively
enclosed basin (the Caribbean, in this case) as "a" or "the" cause for
lower coral cover, etc is very interesting and brings up a point that has
baffled me throughout my career investigating land-based impacts (primarily
terrestrial sediment) on coral reefs.

I would argue that the statement that, "the Caribbean is distinct from
other tropical reef areas in having major river discharges into a
semi-enclosed sea" might not be true - southeast Asia (China, Vietnam,
Thailand, Borneo, Indonesia, Papua New Guinea, etc) has some of the natural
highest geologic uplift, rainfall, vegetation, and resulting weathering,
erosion, landslides. These climatic, geologic, and terrestrial ecologic
processes result in relatively massive terrestrial sediment and associated
nutrient (and maybe thus DOC?) fluxes to the relatively enclosed South
China, Andaman, Java, Timor, Flores, Celebes, Coral, Philippine, etc Seas
in the region, as shown by the seminal papers by John Milliman and James
Syvitski** spanning the 1980s-2000s.

​So my question to all is:

How is ​the Coral Triangle with it's relatively (in a global sense) high
coral cover and high diversity compatible with some of the highest natural
terrestrial sediment and associated nutrient fluxes (let alone growing
populations and their associated anthropogenic contributions) to the seas
where those corals exist?

John D. Milliman and Robert H. Meade
​ (1983)
 "World-Wide Delivery of River Sediment to the Oceans," The Journal of
​, v.​
91, no. 1
​, p.​

John D. Milliman
​ and ​
ames P.M. Syvitski (1992) "
Geomorphic/Tectonic Control of Sediment Discharge to the Ocean:
​ ​
The Importance of Small Mountainous Rivers
" ​
Journal of Geology, v
100, p. 525-544.

ames P.M. Syvitski, Scott D. Peckham, Rachael Hilberman
 Thierry Mulder
​ (2003) "
Predicting the terrestrial flux of sediment to the global ocean:
​ A​
 planetary perspective"
Sedimentary Geology
​v. ​
​, ​p.

James P. M. Syvitski,
​ ​
Charles J. Vosmarty,
​ ​
Albert J. Kettner,
​ ​
Pamela Green
​ (2005) "
Impact of Humans on the Flux of
​ ​
Terrestrial Sediment to the
​ ​
Global Coastal Ocean
" Science, v. 308, p. 376-380

Curt D. Storlazzi, Ph.D.
U.S. Geological Survey
Pacific Coastal and Marine Science Center
2885 Mission Street
Santa Cruz, CA 95060
(831) 460-7521 phone
(831) 427-4748 fax

Staff web page:
Coral Reefs:
*https://coralreefs.wr.usgs.gov/ <http://coralreefs.wr.usgs.gov/>*
Sea-level Rise and Atolls:


Message: 3
Date: Wed, 20 Dec 2017 13:54:01 +0000
From: "Pawlik, Joseph" <pawlikj at uncw.edu>
Subject: Re: [Coral-List] New observational paper and the vicious
        cycle   hypothesis
To: Dr Stuart P Wynne <stuart at stuartwynne.co.uk>,
        "coral-list at coral.aoml.noaa.gov" <coral-list at coral.aoml.noaa.gov>
        <CY4PR0601MB3668F236752B15429CFAFEE4CD0C0 at CY4PR0601MB3668.

Content-Type: text/plain; charset="us-ascii"

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@
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
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