[Coral-List] Impact of nutrient enrichment on coral reefs

Dennis Hubbard dennis.hubbard at oberlin.edu
Fri Mar 14 10:18:13 EDT 2014


Thanks very much for bringing this paper to our attention. It will be very
useful to myself and to my students. In class, we have just completed a
first look at the intersection between top-down and bottom-up stresses and
I used a home-grown modeling simulation that requires them to do multiple
runs at varying levels of nutrient enrichment and overfishing. Because each
"event" in the model (e.g., fish eating an encountered alga, coral
recruitment, negative macro-algal impacts on a specific coral) has a
different degree of randomness applied to it, this "fuzzy logic" dictates
that a) successive runs do not produce absolutely intical results and b)
the system behaves in a very non-linear way both as it crashes and as
stresses are removed to encourage "recovery".

While this approach gives them (and many are non-science majors) a healthy
appreciation of the non-linearity of natural systems going into discussions
of climate change as the third leg of the stool (and the relative economics
of avoiding the problem at today's costs versus fixing it at discounted
rates in the future), I found myself remembering papers a couple of decades
back that challenged the importance of nutrient loading. A number of
equally thoughtful papers followed that argued otherwise. However, I never
developed a clear sense of what folks wrestling with this ultimately

So, first, thanks for what appears like an excellent overview. Second, and
to the larger "brain trust", do the seemingly realistic ideas reflected in
this manuscript reflect the larger opinions on this important topic? I'm
less concerned over arguments over the primacy of particular stresses
(i.e., is climate change or local stress the gorilla in the room?) than I
am about where the science on nutrient impacts relative to overfishing has
come over the past decade. This is not a semantic question and there is no
hidden agenda. I am asking purely out of ignorance and interest.



On Fri, Mar 14, 2014 at 3:14 AM, Wiedenmann J. <
joerg.wiedenmann at noc.soton.ac.uk> wrote:

> Dear all,
> our new publication on the impact of nutrient enrichment on corals and
> coral reefs can now be freely downloaded from the COSUST page:
> http://www.sciencedirect.com/science/article/pii/S1877343513001917
> We discuss, among other issues, the role that the competition for
> nutrients by phytoplankton might play in disturbing the nutrient balance in
> reef ecosystems. The abstract is attached below.
> Best wishes,
> Joerg
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> Prof. Dr. Jörg Wiedenmann
> University of Southampton, Waterfront Campus, NOCS
> Southampton, SO14 3ZH, U.K.
> http://noc.ac.uk/corals
> email: joerg.wiedenmann at noc.soton.ac.uk
> Mobile: +44 (0)7912564356
> Projects on thermal stress tolerance of corals:
> http://www.southampton.ac.uk/oes/research/projects/coral_bleaching.page
> http://www.southampton.ac.uk/oes/research/projects/gulf_corals.page
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> D'Angelo, C., Wiedenmann, J., 2014. Impacts of nutrient enrichment on
> coral reefs: new perspectives and implications for coastal management and
> reef survival. Current Opinion in Environmental Sustainability 7, 82-93.
> Anthropogenic nutrient enrichment is often associated with coral reef
> decline. Consequently, there is a large consent that increased nutrient
> influxes in reef waters have negative longterm consequences for corals.
> However, the mechanisms by which dissolved inorganic nutrients can disturb
> corals and their symbiotic algae are subject to controversial debate.
> Herein, we discuss recent studies that demonstrate how nutrient enrichment
> affects the heat and light stress tolerance of corals and their bleaching
> susceptibility. We integrate direct and indirect effects of nutrient
> enrichment on corals in a model that explains why healthy coral reefs can
> exist over a rather broad range of natural nutrient environments at the
> lower end of the concentration scale and that anthropogenic nutrient
> enrichment can disturb the finely balanced processes via multiple pathways.
> We conceptualise that corals can suffer from secondary negative nutrient
> effects due to the alteration of their natural nutrient environment by
> increased phytoplankton loads. In this context, we suggest that
> phytoplankton represents a likely vector that can translate nutrients
> effects, induced for instance by coastal run-off, into nutrient stress on
> coral reefs in considerable distance to the site of primary nutrient
> enrichment. The presented synthesis of the literature suggests that the
> effects of nutrient enrichment and eutrophication beyond certain thresholds
> are negative for the physiological performance of the coral individual and
> for ecosystem functioning. Hence, the immediate implementation of
> knowledge-based nutrient management strategies is crucial for coral reef
> survival.
> <http://www.mobitec.com/cms/products/bio/07_fluores_tec/eosfp.html>
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Dennis Hubbard
Chair, Dept of Geology-Oberlin College Oberlin OH 44074
(440) 775-8346

* "When you get on the wrong train.... every stop is the wrong stop"*
 Benjamin Stein: "*Ludes, A Ballad of the Drug and the Dream*"

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