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Brown Tide in Texas

Frequently Asked Questions

Cayo Del Grullo.  Photo: Mike Weeks, TPWDWhat causes brown tide blooms? Is increased rainfall part of the problem?

Brown tide is a natural phenomenon with no known linkage to human activity. At this time no one knows the exact combination of factors that causes brown tide, and there are no known ways that humans can control it. There is no evidence that an increase in rainfall causes brown tide to bloom. Research suggests that a number of factors have to be in place for a brown tide to begin. It's important to remember that brown tide has happened before and the Texas marine environment recovered.

Where did the brown tide come from? Is it always there?

Nobody knows where brown tide came from. Aureoumbra lagunensis, the alga responsible for brown tides, was not known before the 1989 Laguna Madre bloom. It seems to be unique to the Gulf of Mexico, though scientists are not sure of its origins. It is thought that brown tide concentrations might rise and fall as part of a natural cycle within the Laguna Madre, suggesting that the organism is present at all times in varying concentrations.

Is brown tide dangerous to humans?

No. Brown tide poses no effect on humans. The main concern is that it can bloom for long periods of time and in dense enough concentrations to harm seagrasses by blocking out the sunlight they need to survive. Click here for more information on Texas seagrasses.

Laguna Madre near Port Mansfield.  Photo: Mike Weeks, TPWDWhat effect does it have on fishing? How will it affect my fishing trip?

Brown tide is fortunately not toxic to fish, so it does not cause fish kills like red tide does. Natural baits have proven successful for anglers because the fish are attracted by the smell. Fishing success with artificial lures may be affected as the reduced water clarity may make artificial lures more difficult for fish to see. Also, because of the patchy nature of the bloom, anglers with boats can often move until they find areas where the bloom is less dense and the water is clearer.

Can you eat fish caught during a brown tide?

Yes. Brown tide does not release any toxins and therefore has no adverse effect on fish. Keep in mind that you should never eat fish found sick or dead, whether or not they are caught during a brown tide.

How long will the bloom last?

At this time, there is no way of knowing how long a bloom will persist.

Where does it occur?

Texas brown tides have been known to occur only in the Laguna Madre, which reaches from Corpus Christi to Port Isabel; they result from blooms of a microscopic alga called Aureoumbra lagunensis, which is unique to the Gulf of Mexico. There is evidence from work at the UT Marine Science Institute that the brown tide has appeared in the Laguna Madre of Tamaulipas. However, the phrase “brown tide” is a general term. It can be used to describe areas of discolored water that occur anywhere in the world due to blooms of a number of different algae.

Characteristic color of brown tide.  Photo: Meridith Byrd, TPWDWhere is it blooming right now?

It's almost impossible to say exactly where the brown tide is at any given moment, because blooms constantly expand and contract and move around in response to winds and tides. It's important to realize that brown tides are patchy and don't cover the expanse of the Laguna Madre. They often concentrate in areas sheltered from the wind or tidal currents.

What’s being done about brown tide?

TPWD and university researchers will continue tracking the location and movement of brown tide. Some water sampling will be done to determine baseline water chemistry associated with the brown tide. Seagrass researchers have been alerted to the presence of brown tide and will be on the lookout for possible impacts to seagrasses from the alga.

How can I report a possible sighting of brown tide?

You can phone the Kills and Spills Team at 512-912-7055. If you need to report a sighting after normal business hours or on weekends, you can get in touch with a Kills and Spills Team biologist by calling one of TPWD’s 24-hour Communications numbers at 512-389-4848 or 281-842-8100.

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