Discovery of algae's toxic hunting habits could help curb fish kills

A microbe commonly found in the Chesapeake Bay and other waterways emits a poison not just to protect itself but to stun and immobilize the prey it plans to eat, a team of researchers from four universities has discovered. The findings about algae linked to massive fish kills could lead to new ways to slow the growth of these tiny but toxic marine creatures.The researchers studied the behavior of the algal cell Karlodinium veneficum, known as a dinoflagellate and found in estuaries worldwide. Each year millions of dollars are spent on measures to control dinoflagellates around the globe. This particular species is known to release a substance called karlotoxin, which is extremely damaging to the gills of fish. Karlodinium veneficum has been known to form large algal blooms in the Chesapeake and elsewhere, triggering an immediate harmful impact on aquatic life, including fish kills."This new research opens the door to reducing bloom frequency and intensity by reducing the availability of its prey," said Allen Place of the Institute of Marine and Environmental Technology at the University of Maryland Center for Environmental Science. "As we reduce the nutrient load feeding Karlodinium's prey and bring back the bay's most prolific filter feeder, the Eastern oyster, we could essentially limit Karlodinium's ability to bloom."Place, in whose laboratory karlotoxin was discovered and characterized, was a co-author of the new study, published this week in the online Early Edition of the Proceedings of the National Academy of Sciences. Other researchers involved in the study came from the University of Minnesota, The Johns Hopkins University and the University of Hawaii."This is a major environmental problem, but we didn't know why these microbes were producing the toxins in the first place," said Joseph Katz, the William F. Ward Sr. Professor in the Department of Mechanical Engineering at Johns Hopkins and a co-author of the paper. "Some people thought they were just using the toxins to scare away other predators and protect themselves. But with this new research, we've provided clear evidence that this species of K. veneficum is using the toxin to stun and capture its prey."Historically, scientists have found it difficult to study the behavior of these tiny animals because the single-cell creatures can quickly swim out of a microscope's shallow field of focus. But in recent years this problem has been solved through the use of digital holographic microscopy, which can capture three-dimensional images of the troublesome microbes. The technique was pioneered by Katz.In a study published in 2007, Katz, Place and Jian Sheng, who was Katz's doctoral student, were part of a team that reported the use of digital holographic microscopy to view the swimming behavior of K. veneficum and Pfiesteria piscicida. At the time, it appeared that K. veneficum slowed down into a "stealth mode" in order to ambush its prey while P. piscicida sped up to capture prey.For the new paper, in which Sheng is lead author, the researchers used the same technique to more closely study the relationship between K. veneficum and its prey, a common, single-celled algal cell called a cryptophyte. They found that K. veneficum microbes release toxins to stun and immobilize their prey prior to ingestion, probably to increase the success rate of their hunt and to promote their growth.This significantly shifts the understanding about what permits harmful algal blooms to form and grow, the researchers said. Instead of being a self-defense mechanism, the microbes' production of poison appears to be more closely related to growth through the ingestion of a "pre-packaged" food source, the cryptophyte cell, they concluded."In the paper, we have answered why these complicated [toxic] molecules are made in nature in the first place and identify a possible alternative mechanism causing massive bloom," said Sheng, who is now a faculty member in the University of Minnesota's Department of Aerospace Engineering and Mechanics.

Fish-Killing Toxin Could Kill Cancer Cells

A powerful fish-killing toxin could have cancer-killing properties as well, according to collaborative research led by Agricultural Research Service (ARS) microbiologist Paul V. Zimba and chemist Peter Moeller of the U.S. National Oceanic and Atmospheric Administration (NOAA). The toxin, called euglenophycin, has a molecular structure similar to that of solenopsin, an alkaloid from fire ant venom known to inhibit tumor development.

The findings were published online in July in the journal Toxicon.
In the summer of 2002, a commercial aquaculture facility in North Carolina reported mysterious fish mortalities in its ponds. More than 21,000 striped bass had died in July and August, resulting in losses of more than $100,000.
To find out why the fish had died, Zimba and Moeller collaborated with Michigan State University biologist Richard Triemer. Zimba works at the ARS Catfish Genetics Research Unit in Stoneville, Miss. The scientists isolated and analyzed dissolved compounds, bacteria and algae from pond water samples.
In a 2004 paper in the Journal of Fish Disease, they identified the culprits as Euglena sanguinea and E. granulata, two species of freshwater algae that had generally been considered benign.
It was the first report of freshwater algae causing fish kills, but it wasn't the last instance of such an event. Zimba and his colleagues have confirmed 11 additional occasions in which euglenoid algae have fatally impacted fish ponds. Losses from these events—which have affected striped bass, tilapia and channel catfish—are estimated to exceed $1.1 million.
Moeller, working in NOAA's Center for Human Health Risk in Charleston, S.C., then purified the active compounds and fully characterized the molecular structure of euglenophycin, the algal toxin responsible for the fish kills. The scientists are seeking patent protection on the toxin, and are currently investigating its properties. Laboratory tests have confirmed that euglenophycin is deadly to fish. Catfish exposed to the purified form of the toxin died within 4 hours of exposure.
One potential use of the toxin is in treating cancer patients. Laboratory tests have shown that even low concentrations of euglenophycin led to a significant decrease in cancer cell growth, and can kill cancer cells. Future tests will attempt to verify whether the toxin can slow or prevent tumor formation. Positive results would indicate that this problematic alga could have beneficial medical applications.
Adapted from materials provided by USDA/Agricultural Research Service.

Thousands of fish dead in Florida Bay

Florida wildlife officials say thousands of fish that turned up dead this week in Florida Bay may be victims of a marine version of heat stroke.Everglades National Park chief of biological resources Dave Hallac says the number of dead fish was unusually large. Redfish, snook and other species were among the dead animals.The bay is a delicate ecosystem with vast flats only a few feet deep. As a result, water conditions can change rapidly with the weather - heat raising the water's salt content and killing sea grass, affecting other life.The park is still investigating possible causes of the deaths.The Miami HeraldAssociated Press - July 23, 2009 5:54 AM ET ST. PETE BEACH, Fla. (AP) - A 19-year-old woman was bitten by a shark while swimming behind her St. Pete Beach home.St. Pete Beach Fire rescue says the wamn, Jenna James, was bitten Wednesday afternoon. St. Pete Beach Fire Marshal Ernie Hand says the bite, below her right knee, was serious but not life-threatening. She was taken to a hospital for treatment.The type of shark that bit James was not identified.St. Petersburg Times

Fish kill feared as algae blooms in Bay

A fish kill could happen soon in Tampa Bay. Scientists in Pinellas County are concerned about an algae bloom stretching 14 miles from Safety Harbor to Weedon Island. The bloom appears as reddish-brown streaks in the water."It's an indicator that something is wrong," said Kelli Levy, with the Pinellas county Department of Environmental Management. "A bloom only occurs if we have stimulated it in some way to grow that fast and to that extent."The bloom could cause the fish kill. At night and on cloudy days, algae depletes oxygen from the water. Fish are left unable to breath."We can have very low oxygen, so you might see fish in the water gulping for air," said Levy."There's no potential human health, risk per se. It's the environmental impacts we're worried about in this case," said Cindy Heil, Senior Research Scientists at the Fish and Wildlife Research Institute.But a fish kill can prompt human health concerns. Last year, thousands of dead fish turned up floating along the Courtney Campbell Causeway. Ben T. Davis beach shut down. The current bloom is much bigger."That area is 3.8 miles where dead fish were found. So now, the bloom is all the way down to Weedon Island so that's 14 miles," said Levy.Microscopic algae can't be removed from the water. It feeds on unnecessary pollutants, from us."We had a lot of rain in May which brought in with it pollutants like fertilizers and yard waste and things that go into storm drains and then we get a good rain event and then it flushes out into the Bay," said Levy.She says the county is making improvements to better protect water quality. "We're building storm water ponds so that the runoff goes from the drain into a pond and gets cleaned a little bit and then the pond discharges to the Bay," Levy said.The algae is not Red Tide. It's Pyrodinium, a species potentially toxic to Shellfish and definitely suffocating to all fish.Levy says a fish could happen in the "near future." However, Heil told FOX 13 "We don't expect one, but if we get a period of more than one or two cloudy days, it's something well be keeping an eye out for.". Kristin Wright Fox News