[Coral-List] Szmant 2002: Great review on nutrient enrichment on coral reefs

[Brodie, Jon]

Hi Mike and thanks for this clarity.
You are correct of course - there's been 16 years of intensive research into the effects of fine sediment and nutrients on coral reefs since the Szmant paper. I found it even at the time to be narrow in its focus to the Caribbean story of nutrients, loss of grazers and the algal/coral competition story (not that this is completely irrelevant), and did not look at the evidence available even in 2002 of the other effects you mention. I'd also include crown of thorns starfish connections to nutrients, where a whole lot of new research has been published recently. 

The other great case of management leading to coral recovery is in Pago Pago harbour where the tuna cannery wastes were diverted to deep water outside the harbour and the coral has now come back. Chuck Birkeland has written this up - I think the paper was in 2013.

Another similar story is from Tampa Florida where management of nitrogen inputs over decades has led to some recovery of seagrass. I think the papers by Greening et al.

Unfortunately at the moment on the GBR we are not managing nutrients (from agriculture) to anywhere near the required amount to have any significant protective effect.

Jon 

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov <coral-list-bounces at coral.aoml..noaa.gov> On Behalf Of Risk, Michael
Sent: Thursday, 3 May 2018 10:02 AM
To: Bruno, John <jbruno at unc.edu>; coral-list at coral.aoml.noaa.gov
Subject: Re: [Coral-List] Szmant 2002: Great review on nutrient enrichment on coral reefs

Hello John, and thank you for bringing this to our attention.

I am of course aware of that paper. Alina is a friend with whom I have shared many a dull meeting, and she has done some wonderful research.

That paper does not rank with her best. It was a sad little piece when it first came out, and now history has passed it by. In order to reach her conclusions, Alina had to rely on the results of ENCORE, while at the same time glossing over a large body of contradictory work. Tom Tomascik has been kind enough to supply us with links to the papers showing how ENCORE was always doomed to miss its original goals.

Back in those days, work on nutrients and reefs was largely done by biologists, and they kept running into correlation-but-not-causation. There was also considerable resistance to the whole idea from an unholy alliance of developers, industry, and compliant governments. The past couple of decades have seen an explosion in the sort of geochemical-sclerochronological research the field needed. Anyone now claiming that nutrients are unimportant in reef ecology would be laughed at, and rightly so. Nutrients have been linked to acceleration in bioerosion (a critical element in carbonate budgets), incidence of disease, coral growth rates, coral recruitment...on and on. We now have methods which can assess nutrient status and trends, and are powerful enough to stand up in court.

Nutrients and their evil travelling companion sediments have had a major impact on reefs, and continue to do so. We should never forget that, in the Caribbean, reef decline began before the middle of the 20th century, and by 1980 half the corals were gone (Gardner et al, 2002). The human footprint was obvious, with corals first being lost near cities. Through the wonderful work of Fabricius, de'Ath and co-workers, we know that the growth rate of corals on the GBR went into decline starting around 1990 (de'Ath et al 2009), and that the GBR lost half its coral cover between 1985-2012 (de'Ath et al 2012).

As though that were not enough: to add to the devastating duo of sediments and nutrients, we now have the impact of chemicals such as pharmaceuticals, pesticides, personal-care products etc, which we have only begun to study. There has been one small victory on this front: due largely to the work of Craig Downs and his colleagues, Hawaii has just banned the use of oxybenzone-containing sunscreens. But a lot of work remains.

We have all been stricken by the news from the GBR, but we must not fall into the trap of assuming climate change is the only cause. First of all, that view is scientifically indefensible. Second, that is a recipe for defeat.

There have been only two examples of which I am aware that followed reef health as a result of improvements in WQ: the well-known example of Kaneohe Bay, in Hawaii, and second, Worthing, Barbados. In both cases, the reef improved as WQ improved. If we truly believe in the environmentalists' mantra, "think globally, act locally", then we should be focused on cleaning up the water. To say that reefs are doomed if the world doesn't decarbonize is to give up. Getting the world off oil and onto renewables will take decades, if not longer. Improvements in WQ can start to-morrow.

In these fora, I try not to cite my own work, or quote myself-for obvious reasons. But looking over this question, I find that I cannot improve on what I wrote in 2009 (Mar Poll Bull 58: 787). It is very hard to keep up with the literature these days, and you seem to be unaware of this work, so forgive me for quoting an excerpt:

"The City of Lake Worth had applied for a permit allowing it to discharge Reverse Osmosis reject water, enriched in nutrients to about the level of sewage discharges, onto one of the few reefs remaining in the state. A local NGO (Palm Beach County Reef Rescue) asked me to come down and testify against the application as a volunteer.

Arrayed against us were six (no doubt highly-paid) men in suits.
Three of them were faculty members at local Florida universities:
all of them quoted second-rate science in support of their position that it was perfectly all right to dump this water on those reefs because, after all, nutrients had no effect on coral reefs. Did not everybody know (they said) that reefs were controlled solely by grazing, and that nutrients were irrelevant?

(I will digress here a moment to lament the current state of coral reef science politics. Somehow, we are led to believe that, out of all the ecosystems on the planet, reefs are the ONLY ones not affected by nutrients (Szmant, 2002). Some of this debate is no doubt truly driven by responsible people going where the data lead, but a cynic might note the confluence of development money and political pressure with the willingness of suits to say it's OK to dump/ dredge/clear/whatever, because it's all grazing and overfishing.)

The debate in the Lake Worth case was not long. I said (I paraphrase
here) ''You guys have opinions. I have 8.2 per mille affected versus 4 unaffected. I would love to see you in court." That meeting was pivotal in the decision by the State to stop dumping sewage on their reefs. In previous work on those reefs, I had just finished obtaining values of d15N from corals that were bathed in that gentle fecal rain-comparison corals from clean(er) areas gave values of 4. As I understand the American legal system, the onus is on proving that the sewage had DIRECTLY affected the reef-and here I had shown that the corals were metabolising it. We would have won the case hands down."

Mike
________________________________________
From: coral-list-bounces at coral.aoml.noaa.gov [coral-list-bounces at coral.aoml...noaa.gov] on behalf of Bruno, John [jbruno at unc.edu]
Sent: May 1, 2018 6:38 AM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] Szmant 2002: Great review on nutrient enrichment on       coral reefs

Dear listers,

Over the weekend I read, for the 3rd or 4th time, Alina Szmant's (2002) incredible review "Nutrient Enrichment on Coral Reefs: Is It a Major Cause of Coral Reef Decline?" and wanted to share it with you.

It's an amazing paper and a good example of how to critically evaluate evidence for a perceived impact. Very thorough and unbiased. You can download it here:  https://www.dropbox.com/s/q6j144vwzx66e2u/Szmant%202002.pdf?dl=0


Here's the abstract:

Coral reefs are degrading worldwide at an alarming rate. Nutrient over-enrichment is considered a major cause of this decline because degraded coral reefs generally exhibit a shift from high coral cover (low algal cover) to low coral cover with an accompanying high cover and biomass of fleshy algae. Support for such claims is equivocal at best. Critical examination of both experimental laboratory and field studies of nutrient effects on corals and coral reefs, including the Elevated Nutrient on Coral Reefs Experiment (ENCORE) enrichment experiment conducted on the Great Barrier Reef, does not support the idea that the levels of nutrient enrichment documented at anthropogenically-enriched sites can affect the physiology of corals in a harmful way, or for most cases, be the sole or major cause of shifts in coral- algal abundance. Factors other than nutrient enrichment can be significant causes of coral death and affect algal cover, and include decreased abundance of grazing fishes by fishing, and of grazing sea urchins to disease; grazing preferences of remaining grazers; temperature stress that kills coral (i...e., coral bleaching) and creates more open substrate for algal colonization; sedimentation stress that can weaken adult corals and prevent coral recruitment; coral diseases that may be secondary to coral bleaching; and outbreaks of coral predators and sea urchins that may be secondary effects of overfishing. Any factor that leads to coral death or reduces levels of herbivory will leave more substrate open for algal colonization or make the effects of even low-level enrichment more severe. Factors that contribute to an imbalance between production and consumption will result in community structure changes similar to those expected from over- enrichment. Over-enrichment can be and has been the cause of localized coral reef degradation, but the case for widespread effects is not substantiated.





_______________________________________________
Coral-List mailing list
Coral-List at coral.aoml.noaa.gov
http://coral.aoml.noaa.gov/mailman/listinfo/coral-list
_______________________________________________
Coral-List mailing list
Coral-List at coral.aoml.noaa.gov
http://coral.aoml.noaa.gov/mailman/listinfo/coral-list