Red tide in Puerto Vallarta still lingering in the Bay of Banderas

The harmful algal bloom known as red tide has afflicted Puerto Vallarta and Banderas Bay since the end of February, causing the death of fish and representing a risk to public health.

Their presence has been monitored by the members of the Department of Biological Sciences of the University Center of the Coast of the University of Guadalajara who, in each sample taken, have found more and more presence of these organisms.

“So far in the year 2022, we have been working and monitoring here in the bay, we observed this red tide from the end of February until yesterday when we went out to the field and here is the curious thing, we have observed a succession of species, so every time we go out to sample, it is a new bloom and this time it is practically covering the entire bay,” explained Dr. María del Carmen Cortés Lara, professor, and researcher at the Department of Biological Sciences of the CU Coast.

The microorganisms found in the bay area are of concern, says the biologist and oceanographer, because they produce neurotoxins, which is why hundreds of dead fish were found on the beach in Puerto Vallarta in recent days.

“Unfortunately, right now we have the presence of a diatom called Pseudonitzschia, which is very harmful because it is associated with the production of domoic acid, which is a neurotoxin, which is why we have observed a large number of dead fish in the bay,” added Cortez Lara. , who recommended people not to swim in places where “dense patches” of these microorganisms are observed, as they can cause skin conditions and obviously, dead fish should not be consumed.

Dr. Cortés explained that this is a natural phenomenon or event. “Right now we are in a spring season where algal blooms are, let’s say, the most normal and natural, but it happens that right now we also have nutrients, waters that are much richer in nutrients due to the presence of (marine) upwellings. The temperature is a little colder, so these conditions are favorable for this type of organism that we normally find in the bay, but right now the conditions are ideal, so that’s why they are flourishing,” she explained.

According to the biologist, the presence of these organisms is commonly between 200 and 300 per liter of water, but currently, they are registered at around 3 million, hence the health authorities could issue an alert in this regard.

“We, as part of the CUC, belong to the Banderas Bay Interstate Red Tide Committee, so the official spokesperson is the Ministry of Health, and it will soon issue a sanitary ban so that molluscs are not consumed mainly,” she added.

In most cases, the highest risk comes from people consuming seafood that ate the toxin: for example, eating whole hard shellfish such as clams, mussels, oysters that have been collected in waters that are not tested.

According to the researcher, it is not really known how long the algal bloom can last, “it could end tomorrow, it could last for several weeks, even until the holidays,” she said.

“Right now we have been monitoring since the end of February and the presence of the red tide continues, so it is recommended that people do not swim in places where they are very dense or in patches that are very red,” she reiterated.

Red tide is a phenomenon that could ruin a beach visit by possibly irritating your respiratory system or making your eyes water. In addition to making beachgoers cough, it also contaminates shellfish and kills fish and larger marine animals, including dolphins and manatees.

“Red tide is a general term for harmful algal blooms (HABs) in the ocean. There are many different algae that are described as red tide,” Dr. Richard Stumpf, oceanographer for National Oceanic and Atmospheric Administration’s (NOAA) National Centers for Coastal Ocean Science, said.

These harmful algal blooms usually make the water reddish-brown. Most of the red tide organisms are able to swim up and down in the water.

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