Damage to Bay caused by classic example of nitrogen eutrophication

Reprinted with permission from the Florida Keys Keynoter

Editor
The recent article by Christine Rapozo explores the definition of an estuary on the basis of amounts of salt in the water. This article serves as a useful function for those readers unfamiliar with coastal ocean processes. She rightly concludes that to define Florida Bay in this manner is very complicated and implies that salinity control is the key to reversing the failing ecology of the region.

The position overlooks the important factors which have damaged the water quality in the region. The damage to the ecology of the bay and the decline of the reef is due to nutrient fertilizers pumped into the Everglades and discharged into Florida Bay. In this case the water becomes the messenger of bad news for the ecosystem.

We are all aware that you do not try to put out a fire by applying gasoline, yet this is analogous to adding fertilizers to natural waters. Explosive growth occurs in the form of blooms of algae. This explosive growth produces massive amounts of organic matter that can damage the environment by reducing the amount of oxygen and sunlight, and the promotion of nuisance/toxic species. All these phenomena are being observed in Florida Bay…

What has happened is that environmentalists argued that the Everglades needed more water: "Too much was being diverted for agriculture and development." Water management people said OK. Some scientists warned that, since these water were loaded with nutrients, it was possible that ecological problems (eutrophication) could occur if the water was diverted into coastal ocean regions. Supporters of the diversion said no. It would not happen because the nutrients would be removed by the dense vegetation of the Everglades as the water flowed through and out into coastal ocean regions.

What happened? The difficult calculations needed to make the diversion model acceptable are probably flawed. For example, the estimate of nutrient reduction by the Everglades did not consider the removal of nitrogen, only phosphate. In our opinion, the water quality in Florida Bay is a classic example of nitrogen eutrophication.

The agonizing part is all this is happening in a government-sponsored marine sanctuary. The environmental definition means a safe place, a refuge. The biblical meaning is not too different: A sacred, holy place - like heaven.

At the present pace, Florida Bay and all surrounding reefs are going to hell.

Charles S. Yentsch
Bigelow Lab
or Ocean Science
Boothbay Harbor, Maine
and Key West
Brian LaPointe
Harborbranch Oceanographic Institute
Fort Pierce and Big Pine Key

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Nutrient Thresholds for Bottom-up Control of Macroalgal Blooms on Coral Reefs in Jamaica and Southeast Florida

Brian E. LaPointe
Harbor Branch Oceanographic Institution, Inc.,
5600 US 1 North
Fort Pierce, Florida 34946

ABSTRACT

During the past two decades coral reefs in the greater Caribbean area have been altered by phase shifts away from corals and toward macroalgae or algal turfs. This study tested the hypothesis that because the phase shift of reefs in Jamaica and southeast Florida involved frondose macroalgae, bottom-up control via nutrient enrichment must be a causal factor. The approach was multifaceted and included measurement of near-bottom nutrient concentrations, salinity, nutrient enrichment bioassays, alkaline photophase assays, tissue C : N : P rations, and tissue 15N : 14N ratios. In both locations, concentrations of dissolved inorganic nitrogen (DIN) and soluble reactive phosphorus (SRP) exceeded nutrient thresholds (~1.0 uM DIN, 0.1 uM SRP) noted to sustain macroalgal blooms on Caribbean coral reefs. High seawater DIN : SRO ratios, alkaline phosphatase activity, and tissue C : P and N : P ratios of macroalgae on the carbonate-rich Jamaican reef suggested SRP limitation of productivity compared to lower values of these variables on siliciclastic reefs in Florida that suggested DIN limitation.

This pattern was corroborated experimentally when SRP enrichment increased P max (photosynthetic capacity at light saturation) of chlorophyte Chaetonmorpha linum in Jamaica compared to DIN enrichment that increased the photosynthetic efficiency under low irradiance of the deeper growing chlorophyte Codium isthmocladium in southeast Florida.

Increased DIN concentrations were associated with reduced salinity on both reefs, indicating submarine groundwater discharge was a significant source on both reefs, indicating submarine groundwater discharge was a significant source of DIN. Elevated soluble reactive 14N values of C. isthmocladium tissue further pointed to wastewater DIN as a source of nitrogen contributing to the blooms in southeast Florida.

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Widespread disease in Caribbean sea fans:
II. Patterns of infection and tissue loss

I Nagelkerken, K. Buchan, G.W. Smith, K. Bonair, P. Bush, J.
Garzon-Ferreira, L. Botero. P. Gayle. C.D. Harvell, C. Heberer, K. Kim, C. Petrovic,
L. Pors, P. Yoshioka

Section of Ecology and Semantics, Cornell University,
Ithaca, New York 14853

ABSTRACT

Large lesions and widespread tissue loss in the sea fans Gorgonia ventalina and G. flabellum L. occured throughout the Carribean during 1955 and 1996. An earlier study identified the putative pathogen as a fungus in the genus aspergillus (Smith et. Al. 1996). Repeated surveys showed that in the Bahamas the incidence (=% of diseased sea fans) and virulence (=% tissue loss per diseased colony) of the disease increased rapidly from 1995 to 1996. Repeated surveys in Curacao and Saba showed little variation in incidence and virulence.

Incidence of the disease was higher on larger than on smaller colonies. On sheltered or moderately exposed shallow reefs (<12m), both incidence and virulence were positively correlated in water depth. The number of lesions on diseased fans, measured only in Curacao, also with depth. These patterns may result from a decrease in wave action, which usually declines with water depth, and the consequent reduction in the swaying motion of the sea fans, thus affecting success of pathogen attachment and establishment. The sea fan predator snail Cyphoma gibbosum was more abundant on diseased than on healthy colonies but its density appears to have been too low to contribute significantly to infection and tissue loss. Algal tumors were found on both healthy and diseased colonies and showed no clear association with the disease.

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Microbial Pests: Coral Disease In the Western Atlantic

D.L. Santavy and E.C. Peters
U.S. Environmental Protection Agency, Gulf Ecology Division, 1 Sabine Dr., Gulf Breeze, Florida 32561, U.S.A
Tetra Tech., Inc. 10306 Eaton Place, Suite 340, Fairfax, Virginia 22030, U.S.A

ABSTRACT

Diseases of sceleractinian corals have increased significantly over the last decade, affecting greater number of species around the world. Gross signs of coral disease are often observed in tissue loss on the skeleton, making differential diagnosis difficult. Using the histopathological and infrastructural techniques, coupled with microbiological analyses, the importance of microorganisms as pathogens in coral diseases is becoming more apparent.

This paper addresses the ecology of pathogens on reefs, specifically bacreria and cynobacteria that produce disease in scleractinian and acyonarian corals.

We review the nature of the disease and the influence of adverse environmental conditions. An update is presented on research concerning the bacteria associated with black- and white- band diseases; observations are presented concerning other coral diseases in the western Atlantic that appear to be caused by bacteria. We conclude with suggestions for improving the recognition that include research to identify bacterial pathogens and the role of environmental factors in the development of coral disease.

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Coral Diseases: What is Really Known?

Laurie L. Richardson
Laurie Richardson is at the Department of Biological Sciences
Florida International University, Miami, FL 33199, USA
(ricardl@fiu.edu)

Reports of new and emerging coral diseases have proliferated in recent years. Such coral diseases are often cited as contributing to coral reef decline. Many of these diseases, however, have been described solely on the basis of field characteristics, and in some instances there is disagreement as to whether an observed coral condition is actually a disease. A disease pathogen has been identified for only three coral diseases, and for only two of these has the pathogen been shown (in the laboratory) to be the disease agent.. In one case, the same disease name has been used for several widely varying coral syndromes, whereas in other multiple disease names have been applied to symptoms that may have been caused by a single disease. Despite the current confusion, rapid progress is being made.

Coral disease emergence in the 1990s
There have been many reports of new coral diseases in the 1990s. These include red band disease, yellow band disease, yellow blotch disease, dark spot disease, white pox, sea fan disease and rapid wasting disease. The emergence of theses dideases was broadcast in the popular literature, on coral reef websites and on coral-reef related internet servers as anecdotal observations. For most of these diseases, supporting data were limited to photographs of afflicted coral colonies. In many cases, it is not clear that what is being shown is actually a disease. The status of these new diseases is extremely confusing.

Only one of the recently emerging new coral diseases has been systematically characterized. Asperillogosis of sea fans (gorgonian corals) rapidly swept through the reefs of the Caribbean and the Florida Keys in 1995 and 1996, resulting in mass mortalities as result of tissue-degrading lesions. A team of investigators, using both laboratory and field techniques, showed that the lesions were caused by the terrestrial fungus Apergillus sydowii (proven in laboratory experiments that fulfilled Koch's postulates, see Koch's postulates for demonstrating the identity of a pathogenic microorganism), and that disease incidence was correlated with water depth and protection from wave exposure. The disease still persists throughouht the western Atlantic. These investigators have postulated that an unexplained, but well documented, mass mortality of sea fans that occured throughout the Caribbean during the 1980s was an earlier epizootic of the same disease. This conjecture is based on photographs of diseased sea fans from the 1980s event that reveal the same lesions now known to be caused by A. sydowii. The effect of this extensive sea-fan mortality on the reef ecosystem is not known.

Results of Studies of individual coral diseases
A summary of what is currently known about coral diseases (including only peer-reviewed literature that contains original data) is presented in Koch's postulates (see Koch's postulates for demonstrating the identity of a pathogenic microorganism). The main conclusions are as follows:

• There are currently only four diseases for which both coral tissue destruction leading to mortality, and the presence of a consistent, characteristic microorganism (or microbila consortium) associated with the disease are known. These are aspergillosis, black band disease, white band disease type II and plague type II. This is in contrast to the 13 individual coral diseases put forth by various investigators.
• Only 3 diseases (aspergillosis, black band disease and plague type II) have an associated microorganism (or microbial consortium) that has been demonstrated to be the disease pathogen.
• The mechanism of coral tissue death is known only for black band disease.
• Only white band disease has been shown to restructure a reef on a regional scale.

Most coral diseases, including new ones and some new ones that were first described in the 1970s and 1980s, have been only partially characterized. These include white band type I, plague type I, shut down reaction, red band disease, yellow blotch, rapid wasting disease, dark spot disease and white pox. No pathogens have been identified for nay of these diseases, and confusion is prevalent. Despite this, many of these syndromes are currently included in monitoring programs designed to evaluate coral reef health.

Current research by many of the investigators cited in this review is focusing on new areas, such as discerning mechanisms of aspergillosis resistance in sea fans, applying molecular probes to confirm identities of pathogens in outbreaks in different regions, and experimental manipulations to trigger disease activity from reservoir populations. Moreover, much current research is aimed at determining the relationship, if any between increased nutrients and coral disease.

The continuation of rigorous research efforts of recent years, specifically those that go beyond descriptive studies, is of critical importance for a complete understanding of coral diseases. A word of caution, however: until a pathogern has been identified for each of the uncharacterized coral diseases (including fulfillment of Koch's postulates), these syndromes should be clearly identified as potential disease states and not coral diseases.

Disease related research in other areas of scientific endeavor always includes strict attention to fulfillment of Koch's postulates ( a procedure set forth by Robert Koch in the 1870s) by which a presumed disease pathogen is demonstrated to be the cause of a disease. To demonstrate unequivocally the identity of a pathogenic microorganism, the following must be carried out:

• The microorganism must be documented as always being found associated with a particular disease.
• The microorganism must be isolated from the disease state and grown in pure culture under laboratory conditions.
• The pure culture of the microorganism must produce the disease when inoculated into a healthy animal.
• The microorganism must be re-isolated from the newly diseased animal and identified as the same microorganism as the presumptive pathogen.

Satifaction of Koch's postulates when the host is a coral is challenging for several reasons. First, duplication of the normal reef environment in library aquaria is difficult, especially in terms of water movement (currents vs. Aeration) and microorganisms present in the water column. Second, the natural mode of infection is not known as a coral disease. Consequently, inoculation by syringe or after wounding the host tissue could be as unnatural as exposure to concentrated suspensions of pathogen in aquarium water of placement of colonies on pathogen-inoculated plates. Finally, it is difficult to prove the re-isolation of the pathogen by sampling the newly diseased experimental coral. Because some diseases are present on the surface of coral tissue, and experimental inoculation usually involves inoculation of the aquarium environment, recovery of the test microorganism could be compromised by the presence of contaminated aquarium water.

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Climate Change Coral Bleaching and the Future of the World's Coral Reefs

Ove Hoegh-Gulberg
Foundation Professor
Marine Studies
University of Queensland

EXECUTIVE SUMMARY

Sea Temperatures in the tropics have increased by almost 1 degree Centigrade over the past 100 years and are currently increasing at the rate of 1-2 degrees Centigrade per century. Reef-building corals, which are central to healthy coral reefs, are currently living close to their upper thermal limit. They become stressed if exposed to small slight increases (1-2 degrees Centigrade) in water and experience coral bleaching.

Coral bleaching occurs when the photosynthetic symbionts of corals (zooxanthellae) become increasingly vulnerable to damage from light at higher than normal temperatures. The resulting damage leads to the expulsion of these important organisms from the coral host. Corals tend to die in great numbers following coral bleaching events, which may stretch across thousands of square kilometers of ocean. Bleaching events in 1998, the worst on record, saw the complete loss of live coral from some reefs in some parts of the world.

This paper reviews our understanding of coral bleaching and demonstrates that the current increase in the intensity and extent of coral bleaching is due to the increasing sea temperature. Importantly, this paper uses the output from four different models to project how the frequency and intensity of bleaching events are likely to change over the next hundred years if greenhouse gas emissions are not reduced. The results of this analysis are startling and a matter of great concern. Sea temperatures calculated by all model projections show that the thermal tolerances of reef-building corals are likely to be exceeded within the next few decades. As a result of these increases, bleaching events are set to increase in frequency and intensity. Events as severe as the 1998 event could become commonplace within twenty years. Bleaching events are very likely to occur annually in most tropical oceans by the end of the next 30-50 years.

There is little doubt among coral reef biologists that an increase in the frequency of bleaching events of this magnitude could have drastic consequences for coral reefs everywhere. Arguments that corals will acclimate to predicted patterns of temperature change are unsubstantiated and evidence suggests that the genetic ability of corals to acclimate is already being exceeded. Corals may adapt in evolutionary time, but such changes are expected to take hundreds of years, suggesting that the quality of the world's reefs will decline at rates that are faster than are expected.

Every coral reef examined in Southeast Asia, the Pacific and Caribbean showed the same trend. The world's largest continuous reef system (Australia's Great Barrier reef) was no exception and could face severe bleaching events every year by the year 2030. Southern and central sites of the Great Barrier Reef are likely to be severely affected by sea temperature rise within the next twenty to forty years. Northern sites are warming more slowly and are expected to lag behind changes in the southern end of the Great Barrier Reef by twenty years. In summary, the rapidity and extent of these projected changes, if realized, spells catastrophe for tropical marine ecosystems everywhere and suggests that unrestrained warming cannot occur without the complete loss of coral reefs on a global scale.

Click here to review complete article.

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