[Coral-List] Nutrients and Macroalgae

Dr. James M Cervino cnidaria at earthlink.net
Mon Oct 16 21:24:24 EDT 2006

Dear Alina:

Ah alas! I am finally being slapped and insulted 
by Dr. Alina Szmant for"prostituting  the 
literature"  and "conduct un-becoming of a 
scientific officer"  eg. " This is not acceptable 
scientific behavior".  All of this, because I 
struck a nerve with regards to anthropogenic 
nutrient inputs and algae smothering corals.  I 
am somewhat disappointed by your response to my 
posting. My references to nutrient enrichment 
seem to have struck a nerve. In the interests of 
shedding more light and less heat on this debate, 
allow me to elaborate.

In my post, I referred to recent findings by 
colleagues, in which they observed the effects of 
macro algae on coral settlement. You correctly 
point out that, in the results presented by 
Kuffner et al., the presence of macrophytes was 
not significantly correlated with numbers of 
larvae. That paper, however, reports a large 
number of significant results, including the 
effect on recruit survival. The overall picture 
is quite clear. If you look at my post I was 
complementing a fellow coral reef scientist on a 
peer reviewed newly published experiment where 
they are looking at the effects of macro-algal 
covering and the inhibition of coral settlement.

As far as I know p < 0.05 is statistically 
significant for the macrophyte/Dictyota pulchella 
or Lobophora variegata treatments and significant 
difference for controls p = 0.032, D. pulchella p 
< 0.0001 between tile and chamber sides! Yes, you 
are correct according to the 1-way ANOVA the 
presence of macrophytes did not significantly 
effect total number of live larvae.  However, 
recruit survival was significantly affected by 
the presence of macrophytes tested during Expt. 4 
(Person chi sq. P < 0.0001).

The results presented by Kuffner et al. are 
troubling in their implications for the long-term 
survival of coral reefs in a time of increasing 
nutrient input to the oceans. There is a growing 
body of evidence that this is a major problem 
(Millenium Report, 2006). Your position is also 
clear, as embodied in your Estuaries paper (V. 
25: 743-766): nutrient enrichment is only locally 
important, if that.

There is room for both points of view, on 
coral-list. My (scientifically informed) opinion 
is that nutrients are a major stress on reefs, 
and I fear I will be shown to be correct in the 
long run.

This is a valid investigation and your critique 
seems to be a function of personal disagreement 
with other national and international scientists 
that counter your position pertaining to natural 
vs anthropogenic nutrient enrichment (Millennium 
Report 2006). Your position regarding 
anthropogenic inputs (Szmant Estuaries Vol. 25, 
No. 4b, p. 743-766 August 2002. Nutrient 
Enrichment on Coral Reefs: Is It a Major Cause of 
Coral Reef Decline? Is clear. You published that 
"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". Do your studies still back this statement?

Then you say in the same paper that " Elevated 
Nutrients on Coral Reefs (ENCORE 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 (Szmant 
2002).  But then in the following sentences you 
claim that ; "Over-enrichment can be and has been 
the cause of localized coral reef degradation".

Help me understand something; in the first few 
sentences you are saying that enriched sites 
cannot affect the physiology of corals in an 
harmful way, only to see 4 sentences later that 
"over enrichment has been the cause to localized 
reef degradation" Therefore, which is it? Does 
enrichment affect coral reefs in a negative way 
and more specific; does macro-algal competition 
with the host tissue negatively impair, weaken, 
degrade the corals physiology?

In my post, I noted that Kuffner et al made the 
point that macroalgae whose growth is stimulated 
by ammonium enrichment have the ability to 
inhibit coral settlement and growth. I fail to 
see why this makes me guilty of prostituting the 

I do understand the role of top down grazing 
controlling macro-algal smothering as there were 
some good experiments that showed this to have an 
impact on coral survival (Lirman 2001;Coral Reefs 
19). What we are saying is that the rate of 
enrichment in the past 20 years cannot be 
controlled by top down grazing mechanisms.

Signature algae species associated with sewage 
include Chondrophycus poiteaui, Dictyota spp as 
well as  L. confervoides inducing significantly 
increasing mortality rates in Porites sp. 
Lapointe et al., (1992) showed that §15N values 
reported for macroalgae in coastal waters with 
natural and anthropogenic sources of nitrogen 
enrichment indicated that the following species 
are directly associated with sewage N15.  The 
goal of the study was to use 15N signatures of 
macroalgae and seagrass epiphytes to assess the 
relative importance of anthropogenic DIN coming 
from sewage in the Keys compared to regional 
scale agricultural to eutrophication in coastal 
waters of the FL Keys.

Corals that become smothered with cyanobacteria 
(blue-green algae) Lyngbya penicilliformis are 
usually associated with high sewage pollution 
containing high levels phosphorous. Dense 
canopies of filamentous Lyngbya, have also been 
shown to displace aquatic plants in Florida 
(Hauxwell et al. 2001). Measurement of stable 
nitrogen isotopes (15N/14N=d15N) in biota has 
been used widely to discriminate between natural 
and anthropogenic nitrogen sources (Risk et al., 
2001) and could provide an early warning tracer 
of anthropogenic nutrient enrichment directly 
from sewage or agricultural runoff thereby 
leading to the demise of tropical coral reefs 
(Risk 2000).

Lapointe et al., (1990) Groundwater Inputs to 
Coastal Waters [Biogeochemistry, Vol. 10, No. 3], 
performed a study to determine the effects of 
on-site sewage disposal systems (OSDS, septic 
tanks) on the nutrient relations of limestone 
groundwaters and nearshore surface waters of the 
Florida Keys.  Macro-algae that were common 
included species indicative of moderate or high 
nutrients like Hypnea musciformis, Enteromorpha 
flexuosa, Bryothamnion triquetrum, and Ulva 
fasciata. (Goreau et al., 1988). Dominant 
macroalgae were species that are indicative of 
moderate or low nutrients, primarily Dictyota 
pinnatifida, Laurencia poiteaui, Halimeda sp., 
Udotea sp,. and Penicillus sp.  (Bell 1992; 
Lapointe et al.,2004; Goreau & Thacker, 1994, 
Coral Reefs, sewage, and water quality standards, 
Jamaica, 3:98-116).

In New England USA; Valiela et al., (1992) also 
showed that human, activities on New England 
coastal watersheds offer the major sources of 
nutrients entering shallow coastal ecosystems. 
Nutrient loadings directly from septic systems 
from watersheds are the most widespread factor 
that alters structure and function of receiving 
aquatic ecosystems by increasing the macro-algal 
biomass that dominates to such an extent that 
leading to anoxic events. They found that 
increases in macroalgae decreased the levels of 
eelgrass habitats thereby changing the benthic 
habitat leading to the significance of "BOTTOM UP 
CONTROLS" in shallow coastal food webs.

In conclusion , according to the Millennium 
Ecosystem Assessment Report that was comprised 
of, over 1300 national science minds from the 
entire globe seem to all agree that the amount of 
nitrogen and phosphorus that has been released 
into the environment as a result of using farm 
fertilizers and sewage has doubled since the 80s 
and that the level if nutrients being added into 
the marine ecosystem cannot be controlled by 
adding more grazers into the system.  According 
to the report; The sudden and extraordinary 
release of anthropogenic free nitrogen and 
phosphorus - has triggered massive blooms of 
macro-algae in the freshwater and marine 
ecosystems. According to the top minds on the 
planet that understand nutrient gradients along a 
macro-algal profiles identified that the nutrient 
loading problem has pushed the planet to the 
"tipping point" that can suddenly destroy entire 

Please keep the personal insults off the list, in 
the future contact me directly- James

Hi Jamie et al:

I do not understand your comment about the Kuffner et al 2006 paper.
For one there is no mention of any nutrient effects of any kind.  Thus
the patterns of algal distribution and biomass that these authors report
are what are found out there but there are no data to show that they
have anything to do with nutrient (or grazing) levels.  The areas they
surveyed are directly offshore of where Florida Bay water exits onto the
Florida reef tract and are best characterized as hard bottom.  There has
been little coral and lots of sediment on those hard bottom over
Holocene time frames (reviewed by Ginsburg, Shinn and others)

Secondly, if you read the paper carefully and study the figures, their
results show that some (not all) algae have a small but variable effect
on coral settlement.  In some cases there was more settlement in
treatments with the algae, in some not, thus not a strong indictment of
algal inhibition of coral settlement. Furthermore, while some of the
differences between treatments were statistically significant the
differences were not biologically/ecologically significant given natural
variability in coral settlement patterns.  My work has shown a strong
preference of several species of coral larvae for the undersides of
field conditioned substrates (Szmant and Miller 2006, 10th Coral Reef
Proc) regardless of presence of macroalgae. In fact, larvae avoid
surfaces covered by algae, encrusting inverts, and some types of
crustose corallines too.  They mostly settle on microfilm and there is
plenty of that available at the scale of a coral larva, even when
macroalgal cover is high.

The likely negative effect of macroalgal cover on coral recruits likely
shows up later when the corals grow out of their cryptic settlement

I know that excess nutrient enrichment, as well as too little grazing,
as well as too much grazing, can all damage small corals, affect reef
substrate composition etc etc etc.  But I hate to see the literature
misquoted for any reason, and your post is a perfect example of how easy
it is for scientists to prostitute the literature.  This is not
acceptable scientific behavior and should be avoided even if the
intention is laudable (e.g. to deter people from polluting coastal


Dear Ilsa & Devon,

Congrats on a thorough well put together manuscript! It is about time
that these data are beginning to get published, I will use this for
my class this next semester.

The sad point is that the people that think urchin grazing and other
dwindling herbivores/landscapers swimming on reef system control the
algal lawns that smother corals.  This says to the developers that
claim  "hey our point source" that is spewing secondary treated
sewage out into a reef is not the reason for the reefs to become
algal dominated, its because the spiny urchin died off that used to
be a proficient landscaper and kept the corals "macro-algae free".

Devon what I am not saying that top down controls are not
significant, they are. However, what I am trying to say is that the
levels of nutrients that induce algal blooms cannot be controlled
with more grazers.

Cheers, James

Dr. James M. Cervino, MS, Ph.D.
Marine Pathology
Department of Biological & Health Sciences
Pace University New York NYC
Phone: (917) 620-5287
Web site: http://www.globalcoral.org

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