Sewage Nutrients Fuel Coral Disease

This dated report is still important today.

January 11, 2004 New Scientist Print Edition

It will also fuel debate about whether run-off from Queensland’s sugar cane and cattle stations threatens the relatively pristine Great Barrier Reef, home to almost one-fifth of the world’s coral reefs.

“We’ve found pretty convincing evidence of a nutrient effect. It’s really happening,” says John Bruno of the University of North Carolina, Chapel Hill, who was lead researcher on the study.

While nutrients may increase the severity of coral disease, the root cause of epidemics remains largely a mystery, says Bruno. Around 80 per cent of Caribbean coral has been lost to disease in the past 20 years, but the decimation occurred across the whole region, not just where pollution is a problem.

However, the nutrients from agricultural run-off and untreated sewage, or even natural causes that bring deep water to the surface, may be making epidemics more severe in the Caribbean. And the problem could worsen. “Even if current levels of pollution aren’t having much impact, imagine what it will be like in 100 years’ time,” he says.

Fungal infection

Bruno and his team looked at two common diseases of Caribbean coral: aspergillosis, a fungal infection that kills soft corals such as sea fans, and yellow band disease, a bacterial infection that kills reef-building hard corals.

In one experiment, the researchers grafted pieces of sea fan infected with aspergillosis onto healthy sea fans in reefs off Mexico’s Yucatán coast. Then, every week for three months, they attached a fresh bag of slow-release garden fertiliser a few centimetres from the graft.

The bags increased the nutrient concentration to between two and 10 times background levels, equivalent to a mildly polluted reef. Exposed to extra nutrients, about twice as much of the sea fan colony became infected with aspergillosis compared with colonies that received the graft but no extra nutrients.

Bruno and his colleagues also studied two species of the reef-building hard coral Montastraea. This can take hundreds of years to grow, so rather than infect healthy coral, the team studied ones that were already infected with yellow band disease. They ran a similar experiment and found that after three months, yellow band disease had killed up to 50 per cent more of the hard coral that had been fertilised with bags of nutrients compared with controls (Ecology Letters, vol 6, p 1056).

Upset balance

The infectious agents that cause the diseases probably feed off the extra nutrients, which are normally in short supply in tropical waters. Upsetting the nutrient balance on the reefs may damage coral in other ways, too. For example, some scientists argue that nutrients stimulate the growth of algae, which then take over space that would otherwise be occupied by coral.

“[Bruno’s] results are fairly conclusive,” says Peter Ridd of James Cook University in Townsville, Australia. But, he says, the nutrient level used in the study was generally higher than those seen on the Great Barrier Reef. What is more, although disease is a huge problem for the Caribbean reefs, the barrier reef is relatively disease-free.

Conservationists claim that climate change and agricultural run-off are already taking their toll on the barrier reef, and that some reefs closer to land have less coral coverage and less diversity than before. But some scientists, including Ridd, have argued that any run-off is likely to be far too dilute to affect the coral, and that the relatively small changes that have been seen on the barrier reef so far may be due to natural fluctuations in coral growth (New Scientist print edition, 4 January 2003).

But Clive Wilkinson, a coral expert at the Australian Institute of Marine Science in Townsville, says he is worried about the future of the barrier reef. “The nasty trilogy of disease, climate change and pollution are all acting together to knock out coral around the world. On the Great Barrier Reef, we’re not pressing the panic buttons yet. But we’re nervous.”

Scientists examine the decline of Florida Bay

Scientists Examine Decline of Fla Bay

This is a dated but significant story on the causes of the extensive loss of marinelife in Florida Bay.  

Sunday, October 17, 2004
By CATHY ZOLLO, crzollo@naplesnews.com

Twenty years after it began its downward spiral, the debate still rages about what is causing big problems in Florida Bay.

The western part of the bay is where the Naples Daily News first reported black water in the spring of 2002, but the problems are older than that by decades.

The crescent- shaped bay between the Florida peninsula and the string of Keys islands was once home to crystal clear water and lush sea grass beds.

Now the turtle grass that suffered a massive die-off in the early 1990s is being replaced by another species that likes nutrient pollution. The patch reefs just north of the middle Keys are barren of lobster that used to crowd under massive boulder corals.

Those corals are dead now, covered in a carpet of smothering green algae, the water often cloudy in an ecosystem that demands clear.

Black water, a phenomenon that scientists link to massive algae blooms and that damages life on the sea floor, has happened a few times since on a smaller scale than the 2002 event.

Professional scuba diver Don DeMaria, who’s been here through most of it, doesn’t wander up in the bay anymore.

He has enough problems in the reefs to the south where the water quality is better, but not much. This is an interconnected ecosystem after all.

DeMaria used to collect tropical fish for the aquarium market but gave that up because he just couldn’t see well enough in the increasingly murky water.

Now DeMaria collects sponges for researchers looking for compounds to cure cancer.
Those hold still and you can feel for them if you have to.

“Years ago all you had to contend with was the wind (to cause cloudy water),” DeMaria said. “Now you have to contend with the wind and the algae blooms.”

Depending on who’s answering the question about these problems, the answer is as complex as a scientific history lesson or as simple as basic math: take an environment that demands clear, pollution-free water, add nutrients from sewage and agriculture and you get the mess that is Florida Bay and the reefs south of the Keys. The latter are down to 7 percent live coral cover.

The history lesson that largely opposes that viewpoint goes something like this:

Florida Bay wasn’t always clear, besides which the redirection of fresh water that once ran to the bay has caused most of the problems. Higher salinity killed the sea grass that in turn decomposed and fed algae blooms.

That idea, held by scientists at the Florida Keys National Marine Sanctuary and Florida International University, holds that while runoff coming from the mainland contains nutrients, there is a question about what happens to those nutrients in the mangroves that fringe the eastern and central bay.

And there is still some debate about which happened first, the algae blooms or the sea grass death.

Brian Keller, science coordinator for the sanctuary and also a member of the Florida Bay Program Management Committee, said managers do look at water quality going into the bay. They just don’t happen to agree with other theories about what the water might be doing.

“We’re always concerned about the quality part of the quantity, quality, timing and distribution mantra for Everglades restoration,” Keller said.

That quality question is in play because the $8.4 billion project that is supposed to save the Everglades by increasing water flows through the river of grass will have those flows ending up in Florida Bay.

If the quality is not right, the bay could suffer.

Brian Lapointe, senior scientist at Harbor Branch Oceanographic Institution in Fort Pierce, said it already is — has been since the hypersalinity theory grew wings and led to a demand for more water for the bay.

Critics of the hypersalinity theory, Lapointe chief among them, say it missed the mark because more fresh water was already reaching the bay as early as the 1970s. It was called the Interim Action Plan, during which water that had until then been back-pumped into Lake Okeechobee to keep sugar cane fields dry was instead directed south to Florida Bay.

The interim plan’s goal was to keep the lake from crashing under massive algae blooms that resulted from the infusion of nutrients that came with the backpumped water.

It worked for the lake. Not so much for the bay.

Lapointe has been in the basic math camp since the early 1980s when he began a monitoring program for Looe Key, a reef just south of the middle Keys, that continues today.

He says the blooms happened first, and they smothered more than 100,000 acres of turtle grass.

They followed releases of nitrogen-rich water from the Shark River Slough that feeds western Florida Bay.

In a paper he recently published in The Journal of Experimental Marine Biology and Ecology, Lapointe said he used nitrogen isotopes to trace the source of the nutrients at Looe Key.

He found that when it rains a lot, the signature is from sewage.

When water releases are high from the mainland into the bay — and flow through the channels between islands to Looe Key — the signature is from agriculture.

Though progress is under way to install a sewer system in the most heavily populated parts of the Keys, the job isn’t complete, and many homes still rely on septic tanks that leach nutrients into Keys waters.

Key West has sewers and treats its waste water to remove nutrients before pumping it into an injection well. Stock Island is getting sewers and, as soon as Key West Resort Utilities that is doing the job reaches 100,000 gallons a day, it will go to the same advanced treatment as Key West. The city of Marathon just got 900 homes onto sewer lines with its Little Venice operation, and Islamorada and Key Largo are moving along with plans and a sewer system.

Still, there is the runoff from the mainland to consider.

The Modified Water Deliveries project — called Mod Waters — will be completed in 2006. At that point, engineering changes will flush an additional 4,000 cubic feet per second in a sheet flow of water through the southern Everglades and into Florida Bay.

While the increased water and managed flow might be good for the’Glades, the water quality, or lack of it, will harm the bay and the reefs, Lapointe has said.

Water managers acknowledge that more water means more nitrogen.

Though the National Academies of Science in August 2002 called for more research into Lapointe’s nitrogen question, local water managers have been a bit slower to acknowledge the problem.

But Deevon Quirolo, who, along with her husband, Craig, founded Reef Relief, said there is a glimmer of hope. Reef Relief, a grass-roots effort to save dying reefs, has been fighting alongside Lapointe for such recognition and got their first hint in June that things were going their way.

In a letter, Chip Merriam, deputy executive director of water resources for the South Florida Water Management District, said the district is looking at the possible impacts of nitrogen on the bay and reefs.

“We are definitely making headway,” Quirolo said. “This is one of the most difficult challenges we’ve had. It’s a good fight and an important issue, one that will have a huge impact on the survival of the reef.”

http://www.flyrodreel.com/node/12185

Florida Keys Keynoter: Study Links Sewage and Reef

by Pamela J. Suarez, July 20, 2007: Studies by Dr. James Porter and others document that nearshore waters and offshore coral reefs in the Florida Keys are contaminated with human sewage.