You may have heard of red tides, but are you aware of their impact on people and the environment?
Red tides can have a widespread effect on marine life, and can affect you if you swim in the water or consume contaminated seafood.
Let’s take a look at what causes a red tide, how it impacts the environment, and what you can do to reduce your exposure to its toxins.
A red tide is sometimes referred to as a harmful algae bloom (HAB). It’s made up of microscopic algae or phytoplankton, which are essential to ocean life.
When these algae receive excess nutrients, they can multiply uncontrollably, becoming a large mass that suffocates nearby ocean life. Some algae species, like Karenia brevis, can give the ocean a red tint, hence the name, red tide.
However, not all red tides color the ocean. In some cases, HABs are not dense enough to give the ocean a particular hue. Their most prominent effect is often seen in the surrounding ecosystem.
HAB toxins are harmful to the marine mammals, birds, and turtles that live in the water. They can also have an impact on the wildlife that feed on animals that are exposed to red tide.
Most phytoplankton species are not harmful to people, but a small number of species are known to produce potent neurotoxins. These toxins can be transferred down the food chain, affecting people who accidentally ingest them.
The consumption of shellfish, such as mussels or clams, is one of the most common ways for humans to be affected by red tide.
Ingesting toxic seafood
Paralytic shellfish poisoning (PSP) is a syndrome that people can develop if they eat seafood contaminated by a red tide.
PSP can be life threatening and often shows itself within 2 hours of consumption. Symptoms include:
In non-lethal cases, these conditions may appear over the course of a few days. In severe instances, individuals may experience respiratory arrest within 24 hours of consumption.
Other shellfish poisoning syndromes include:
- Amnesic shellfish poisoning (ASP). ASP symptoms include nausea, vomiting, and diarrhea. If left untreated, it may lead to permanent damage to the central nervous system.
- Diarrheal shellfish poisoning (DSP). DSP may cause nausea, vomiting, and abdominal cramps, and individuals are prone to becoming extremely dehydrated.
- Neurotoxic shellfish poisoning (NSP). NSP can cause vomiting, nausea, and other neurological symptoms as well.
Coming into contact with toxic water
Coming into physical contact with red tide may result in breathing problems, even for people who don’t have previous respiratory issues.
The toxins associated with red tide may also cause skin irritation, rashes, and burning or sore eyes.
There’s no known antidote for conditions caused by red tide, such as PSP. Severe cases may be treated with the use of life support systems, such as a mechanical respirator and oxygen until the toxin fully passes through your system.
There are a few ways that red tide poisoning can be prevented:
- Avoid entering bodies of water that have a distinct foul odor, appear discolored, or have foam, scum, or algal mats (sheet-like accumulations of blue-green algae) on the surface.
- Follow local or state guidance about the safety of the water.
- Check environmental or state websites for local beach or lake closures before visiting.
- Do not drink directly from lakes, rivers, or ponds.
- Do not fish, swim, boat, or participate in water sports in areas experiencing a red tide.
- Rinse off pets with clean water after they’ve been in the pond, lake, or ocean. Do not allow them to lick their fur until they’ve been rinsed.
- Follow local guidance when consuming harvested fish or shellfish.
- Avoid eating large reef fish.
Store-bought and restaurant-served shellfish are typically safe to consume during a red ride because the shellfish industry is closely monitored by state agencies for shellfish safety.
Commercially available shellfish are often not locally harvested and, if harvested locally, are tested for toxins prior to being sold to the public.
Most people can swim during red tide without serious risks, but it may cause symptoms such as skin irritation and a burning sensation in the eyes.
A red tide may not be harmful to humans who aren’t exposed to its toxins, but it can have a negative impact on marine life.
If you eat seafood contaminated with toxins, neurological symptoms may occur and become serious. There’s no antidote for syndromes such as PSP, but life support systems, such as a mechanical respirator and oxygen, can help you make a full recovery.
See a doctor if you think you may have eaten contaminated seafood.
You can avoid these types of syndromes and physical irritation from a red tide by taking precautionary measures before heading to the lake, pond, or beach.