COLLEGE STATION, Texas — One of the largest and longest red tides in Texas history appears to be disappearing, thanks in part to recent and much-needed rains, giving a well-deserved rest to volunteers who helped track the harmful algal bloom.
Samples collected and studied by Red Tide Rangers, a group created by the Texas Sea Grant College Program’s Tony Reisinger and the acting director at The University of Texas-Pan American’s Coastal Studies Laboratory, Don Hockaday, showed no red tide cells in the waters near South Padre Island.
“I think we can say that red tide gone from South Texas and is not likely to come back in the near future,” said Reisinger, Cameron County Coastal and Marine Resources Agent with the Texas Sea Grant Extension Program (TXSGE).
Declining water temperatures had already affected the health of red tide organisms — the small photosynthetic plant Karenia brevis — and increased freshwater inflows into Texas coastal waters from inland storm runoff is dropping salinities below levels the normally open-ocean dweller needs to survive.
“I’m really hopeful this (freshwater inflow) is the nail in the coffin for red tide,” said Meridith Byrd, Texas Parks and Wildlife Department (TPWD) harmful algal bloom (HAB) biologist. “We’re seeing very low cell counts along the rest of the Texas coast.”
Most of the information Byrd uses to track red tide in south Texas comes from Red Tide Rangers, who collect water samples daily from several locations around South Padre Island and then count the number of Karenia cells. They also note the number of dead fish, if any, and gauge the severity of the irritating aerosol created when red tide cells break apart in the surf.
Byrd calls the Red Tide Rangers “an invaluable part of our red tide monitoring program. They are out there giving us daily data, and there is no other network like them along the Texas coast. We would not otherwise be getting the kind of data they give us because we don’t have sufficient staff to do so.”
The current red tide has been an inconvenience at times to coastal residents but it has devastated the state’s oyster industry. The public oyster season, which should have opened Nov. 1, 2011, remains closed along most of the coast, including in Galveston Bay, where the vast majority of the state’s oyster crop is harvested. The closure has cost oyster fishermen about $7 million thus far, said Lance Robinson, TPWD Coastal Fisheries Division Upper Coast Upper Coast Regional Director.
The bloom was first detected in Brazos Santiago Pass, near the City of South Padre Island, in early September by a TPWD crew conducting a routine sampling cruise to monitor local fish populations. Crew members noticed fish swimming erratically near the water’s surface and gulping for air. Reisinger collected a water sample from the area shortly thereafter and confirmed the presence of Karenia cells.
Karenia is an ever-present inhabitant of the Gulf of Mexico, but usually in extremely small numbers of cells per milliliter of water, a standard by which it is measured.
“Finding one cell here and there is not enough to cause a panic, but finding even a handful of cells can spur us into stepping up our monitoring to determine if the counts will continue to grow over time into a full-blown bloom,” Byrd explained.
In terms of geographical size, the latest red tide spread from the southern tip of Texas to the lower reaches of Galveston Bay, putting it on par with another very large Karenia bloom in 1986. For reasons as yet unknown, the recent red tide killed just one-fifth of the 22 million fish that died in 1986.
Robinson said the latest bloom owes its duration — it is thought to be among the longest on record — to the severe drought in Texas. Karenia likes living in seawater, where the average salinity is about 35 parts per thousand (ppt). Red tides can spread to Texas bays but they usually do not persist for long when freshwater inflows lower the salinity of the bays below about 22 ppt. The drought has greatly curtailed freshwater inflows, leaving Texas bays saltier than normal.
“Galveston Bay rarely sees red tide because the organism is an open ocean dweller and usually the bay is fresh enough that the plant doesn’t like it,” Robinson said. “This drought is responsible for some of Galveston Bay’s highest salinities on record and is providing an education on a number of fronts for us by showing us what may happen in the future as more freshwater — even in non-drought years — is diverted from rivers for use by our growing population. As less water gets to the bays, the incidence of red tide will most likely increase. The impact on resources like oysters will be there as well.”
It was the 1986 bloom and a couple more in the early 1990s that led Reisinger and Hockaday to form the Red Tide Rangers. Reisinger remembers “fish piled up like cordwood along the beaches and the inshore areas around South Padre Island” during the 1986 bloom. “All major species of game and prey fish were affected. There were huge tarpon lying all over the place. The smell was absolutely horrendous,” he said.
TPWD had precious few staff available to handle the sampling needed to monitor the blooms, Reisinger said, so he and Hockaday decided to lend a hand by having preeminent red tide researcher Karen Steidinger in Florida train them to identify and count red tide cells in water samples. Steidinger is the “Karen” in Karenia, an honor bestowed upon her by taxonomists in recognition of her pioneering work.
“The red tide organism is such a big cell that if you get up extremely close, like on a floating dock, and the light is right, you can see all of these little red dots swimming around in the water. It’s like a swarm of bees,” Reisinger said. “But it was difficult learning to count them because there can be many cells per sample.”
Reisinger and Hockaday found they could not collect and analyze the number of samples they needed to adequately monitor a bloom, so they struck upon the idea of training volunteers to collect water samples from areas suspected of having red tide. The volunteers soon overwhelmed Reisinger and Hockaday with more samples than they could manage in a timely manner. The obvious solution, said Reisinger, was to further train the volunteers to identify and count Karenia cells in the samples they collected.
The initial class of about 20 volunteers, whom Reisinger dubbed Red Tide Rangers, has since almost doubled in size and is now largely coordinated by Brigette Goza at The University of Texas-Pan American Coastal Studies Laboratory at South Padre Island. Their work has proved invaluable and led to them receiving a Gulf Guardian Award from the U.S. Environmental Protection Agency in 2006.
Data provided by Red Tide Rangers helps Byrd not only monitor blooms, but also update the public so people can better judge the health risks they face if they plan on being near the water. Karenia itself is not harmful. The danger comes from a potent poison called brevetoxin that the alga carries. Scientists do not know for certain why Karenia produce brevetoxin, but there is evidence that it is not a defensive mechanism. Research indicates brevetoxin may help Karenia control the amount of salt in a cell as the organism moves from the Gulf of Mexico into less salty bays.
Karenia is a very fragile cell and breaks easily, particularly when pounded by waves in surf zones. When broken, the cells release their brevetoxin into the water, where it mixes with the salt spray created by waves to form an aerosol that irritates eyes and respiratory systems. Healthy people suffer little more than discomfort, but the aerosol can pose much greater danger to asthmatics and others who suffer from respiratory conditions.
Brevetoxin is also dangerous to humans and other animals if they ingest it through eating tainted seafood, leading to neurotoxic shellfish poisoning (NSP). Symptoms include nausea and vomiting; burning, itching or tingling of the mouth and lips; slurred speech; and dizziness.
Brevetoxin collects mainly in the organs of fish. A minute amount — but not enough to be harmful — is deposited in the meat of fish, so those caught in red tide areas are safe to eat as long as they are caught live and are acting normally, Byrd said. Animals, particularly dogs and coyotes, have died from eating contaminated fish because they consume the organs as well as the meat.
Filter feeders like oysters also accumulate brevetoxin in their organs and are the primary source of NSP in humans, which is why the Texas Department of State Health Services closes oyster harvesting in a bay when red tide cells are detected. Brevetoxin is a very stable compound that cannot be destroyed by cooking and remains in fish tissue for long periods of time. Despite the lack of red tide at the southern end of the state, the Cameron County Department of Health and Human Services continues to issue a warning to pet owners to monitor their dogs closely because there may still be some tainted dead fish on area beaches. Reisinger said the foam created by red tide-laden surf is also thought to be harmful to canines when sniffed and researchers believe at least one dog died after inhaling brevetoxin from the foam.
The Texas Sea Grant College Program is a partnership of university, government and industry focusing on marine research, education and outreach. It is administered through the National Oceanic and Atmospheric Administration and is one of 32 university-based Sea Grant Programs around the country. Texas Sea Grant is a non-academic research center in the College of Geosciences Texas A&M University.
TXSGE is a joint outreach program of Texas Sea Grant, Texas AgriLife Extensionand the Commissioners Courts in participating counties.