[Coral-List] Vicious cycle hypothesis, rivers, and enclosed seas

Thu Dec 21 12:04:45 EST 2017

Hi Curt and those interested in this thread,

River sediment load is not the same as DOC load.

The long meandering rivers that travel across flat swampy lands and empty into the Caribbean have lots of DOC, while the short, rapid rivers that empty into the waters of the coral triangle have lots of sediment.

Milliman & Meade (1983):  p. 17 (2nd column, top): “The large islands of the western Pacific Ocean are among the most prodigious producers of river sediment… Because of their active tectonism and volcanism, steep slopes, heavy rainfall, and intense human activity, these islands contribute large quantities of river sediment to the ocean.” They then go on to point out that the rivers of the island of Taiwan alone produce more sediment than the entire continental US!  Steep, fast flowing rivers produce a lot of inorganic sediment load, but there isn’t time to produce the DOC “tea” that comes from slow flow and interaction of river water with terrestrial soils, trees, marshes, etc.  Long, slow rivers produce much more DOC, but less sediment load, which tends to fall out of suspension in the river delta. Table 2 in Milliman & Meade (1983) provide the water discharge data for river systems around the world, and the Mississippi, Magdalena, Orinoco and Amazon are 580, 237, 1100, and 6300 km3yr-1, respectively, while the largest in Asia that are near the Coral Triangle are the Hungho and Mekong in Vietnam, (123 and 420) and in Oceania are the Fly and Purari (PNG, both 77). The long, slow rivers that empty into the Caribbean have relative little sediment deposition but the largest combined freshwater inputs on Earth and particularly large DOC fluxes because of the large drainage basins that feed them.  Dai et al. (2012) estimate that the DOC flux for the Amazon is 30.7 TgCyr-1, the next highest is the Congo (11.9) then the Orinoco (4.3). The Mississippi is 2.3. The largest input into the Coral Triangle cited is the Fly, with 1.1. Note that the Amazon empties along the coast of Brazil, but the freshwater and DOC rides on the surface and is blown into the Caribbean during half the year (Salisbury et al. 2011). 

All this said, there are places in the Coral Triangle, and elsewhere in the Indo-Pacific, that have more freshwater input and are intermediate in sponge cover relative to the ends of the spectrum (Caribbean vs. oligotrophic oceanic Indo-Pacifc reefs).

Curt, as far as corals go, I would say they can tolerate high sediment loads better than they can tolerate high DOC loads, when the DOC load results in the rise of a feedback loop between seaweeds and sponges that outcompete them.

Regards,

Joe
**************************************************************
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 Storlazzi, Curt
Sent: Wednesday, December 20, 2017 1:18 PM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] vicious cycle hypothesis, rivers, and enclosed seas (Coral-List Digest, Vol 112, Issue 12 -)

Colleagues,

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 Geology , v. 91, no. 1 , p. 1-21.

John D. Milliman
 and 
J
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.

J
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. 
162
, p.
5–2
4.

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:
https://www.usgs.gov/staff-profiles/curt-d-storlazzi
Coral Reefs:
*https://coralreefs.wr.usgs.gov/ <http://coralreefs.wr.usgs.gov/>* Sea-level Rise and Atolls:
*https://walrus.wr.usgs.gov/climate-change/atolls/
<http://walrus.wr.usgs.gov/climate-change/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>
Message-ID:
        <CY4PR0601MB3668F236752B15429CFAFEE4CD0C0 at CY4PR0601MB3668.
namprd06.prod.outlook.com>

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

http://people.uncw.edu/pawlikj/2016BioSciencePawlik.pdf

Regards,

Joe
**************************************************************
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:
http://www.gov.ai/documents/fisheries/AFMR%20Research%
20Bulletin%2008%20(2017)%20-%20Observational%20Evidence%20of%20Regional%
20Eutrophication.pdf

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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