By Maggie Broadwater, Guest Blogger from NOAA’s Harmful Algal Bloom Analytical Response Team.
Animals living in coastal waters may face a number of environmental stressors—both from nature and from humans—which, in turn, may have compounding effects. This may be the case for marine life near Galveston Bay, Texas, which recently experienced both an oil spill and another threat coming from its own waters.
On the Lookout
Marine sentinels, like bottlenose dolphins in the Gulf of Mexico, share this coastal environment with humans and consume food from many of the same sources. As marine sentinels, these marine mammals are similar to the canary in the coal mine. Studying bottlenose dolphins may alert us humans to the presence of chemical pollutants, pathogens, and toxins from algae (simple ocean plants) that may be in Gulf waters.
Compared to other coastlines, Texas waters are a haven for a diverse array of harmful algae. Additional environmental threats for this area include oil spills, stormwater and agricultural runoff, and industrial pollution.
A few types of algae produce toxins that can harm fish, mammals, and birds and cause illness in humans. During harmful algal blooms, which occur when colonies of algae “bloom” or grow out of control, the high toxin levels observed often result in illness or death for some marine life, and low-level exposure may compromise their health and increase their susceptibility to other stressors.
Recently, we have been learning about the potential effects of oil on bottlenose dolphin populations in the Gulf of Mexico as a result of the Deepwater Horizon oil spill in April 2010. Dolphins with prolonged exposure to oil may develop lung disease and inflammation, and be less able to deal with stress. However, we know very little about the combined effects from both oil and harmful algal blooms. We now have a unique but unfortunate opportunity on the Texas coast to study these phenomena together.
On March 14, Texas officials closed Galveston Bay to the harvesting of oysters, clams, and mussels afterdetecting elevated levels of Dinophysis. These harmful algae can produce toxins that result in diarrhetic shellfish poisoning when people eat contaminated shellfish. Only four days later, on March 18, trained volunteers from NOAA’s Phytoplankton Monitoring Network detected Pseudo-nitzschia in Galveston Bay. NOAA scientist Dr. Steve Morton confirmed the presence of Pseudo-nitzchia multiseries, a type of algae known as a diatom that produces a potent neurotoxin affecting humans, birds, and marine mammals. NOAA’s Harmful Algal Bloom Analytical Response Team confirmed the toxin was present and notified Texas officials.
These environmental conditions were familiar to Morton. He immediately recognized parallels to what occurred in this region around the 2008 Texas Bottlenose Dolphin Unusual Mortality Event. Between February 1 and April 4, 2008, 119 bottlenose dolphins stranded along the Texas coast. Following confirmation of aDinophysis bloom, the presence of the harmful algae Pseudo-nitzchia pungens was identified while the dolphin mortality event was ongoing. Analysis of samples collected from these stranded dolphins showed low levels of the toxins produced by both these algae. This was the first reported association of multiple algal toxins with an unusual mortality event. Dealing with more than one type of harmful algae at a time may hit dolphins particularly hard.
When Oil and Algae Mix
Studying marine mammal mass strandings like the one in 2008 helps NOAA scientists and coastal managers understand the effects of harmful algal blooms across seasons, years, and geographical regions. We know that acute exposure to algal toxins through diet can cause death in marine mammals, and that even exposures to these toxins that don’t kill the animal may result in serious long-term effects, including chronic epilepsy, heart disease, and reproductive failure.
But in many cases, we are still working to figure out which level of exposure to these toxins makes an animal ill and which leads to death. We also don’t yet know the effects of long-term low-level toxin exposure, exposure to multiple toxins at the same time, or repeated exposure to the same or multiple toxins. Current NOAA research is addressing many of these questions. A dolphin mortality event, like the one in Texas in 2008, may have many contributing factors; harmful algae may only be one piece in the puzzle. Thus, we do not yet know what effects recent Dinophysis and Pseudo-nitzchia blooms may have on marine mammal populations living in Texas coastal waters. Coastal managers and researchers are on alert for marine mammal strandings that may be associated with exposure to harmful algae, but the story is unfolding, and has unfortunately gotten a lot more complex.
Four days after harmful algae were found in Galveston Bay, it was hit with an oil spill. On March 22, 2014, theM/V Summer Wind collided with oil tank-barge Kirby 27706 in Galveston Bay near Texas City, releasing approximately 168,000 gallons of thick, sticky fuel oil. The Port of Houston was closed until March 27. State and federal agencies are responding via the Unified Command. NOAA is providing scientific support andNatural Resource Damage Assessment personnel are working to identify injured natural resources and restoration needs. Much of the oil has come ashore and survey teams are evaluating the shorelines to make cleanup recommendations.
Time will tell if the harmful algal toxins and oil in Galveston Bay have a major negative effect on the marine mammals, fish, and sea turtles that live in surrounding waters. Data from the Texas Marine Mammal Stranding Network show an increase in marine mammal strandings beginning in January 2014 and peaking February through now. They responded to regular reports of marine mammal strandings following the March 22 oil spill, but many of these animals were in late stages of decomposition by the time they were recovered. Only two of them showed visible signs of oiling. It is not yet clear if there have been more strandings or simply more observations as a result of heightened awareness and surveys by oil spill responders.
This is an opportunity to study the effects of multiple stressors on these animals, and we should monitor this ecosystem carefully to determine the effects of what could be a “perfect storm” of environmental and human factors along the Texas coast. Fortunately, NOAA scientists with a range of expertise—from dolphins to harmful algae to oil spills—are on the job.
For more information, contact Maggie.Broadwater@noaa.gov.
Maggie Broadwater is a research chemist and serves as coordinator for NOAA’s Harmful Algal Bloom Analytical Response Team at the National Centers for Coastal Ocean Science in Charleston, S.C.