9/8/2023 0 Comments Algal bloom red tide algae![]() ![]() Small amounts of the okadaic acid usually do not have any harmful effects and only become an issue when large amounts are consumed. It is caused by Okadaic acid, which is produced by several species of dinoflagellates, and is usually non-deadly to humans. Diarrhetic Shellfish Poisoning is another example of a harmful effect from eating contaminated shellfish. Some of the toxins that cause Paralytic Shellfish Poisoning can be 1,000 times more potent than cyanide. It can cause paralysis and in extreme cases death. Paralytic Shellfish Poisoning is typically found along the Pacific and Atlantic coasts of the United States and Canada. Thus when smaller marine animals feed on the algae, the trophic level above them can become poisoned as well. The toxins produced can often affect the respiratory and nervous systems of all life forms. Very few algae species can produce this toxin but when a large enough group forms on shores it can have a negative effect on both the marine environment and humans. What becomes a problem or what classifies as a “Red Tide” are the algae that release toxins in the air and water when they grow. ![]() Algae alone is not an issue and even during the time of the year where there seems to be an excess amount of growth, this is a natural occurrence. The photos above show two examples of Algal blooms from two very different parts of the world, yet both species are considered “Red Tide” and harmful to some shellfish and animals that eat the shellfish. What is important to recognize about “Red tides” and Algal blooms is that it isn’t always obvious that algae growth is there. “Red Tides in Isahaya Bay, Japan / Algal Bloom in Pelee Island, Ontario” by Marufish and Tom Archer There are three types of algae that can release these harmful toxins, they are Alexandrium fundyense, Alexandrium catenella and Karenia brevis. The toxins in the water could have negative effects on the health of humans and animals exposed to them. Some effects of the red tide are that it could deplete the oxygen in the water and/or release toxins into the water. Some key factors involved in red tides forming are warm ocean surface temperatures, low salinity, high nutrient content, calm seas, and rain followed by sunny days during the summer months. This is where the name “red tide”comes from. It is also sometime referred to as a Harmful Algal Bloom or “HAB”. The red tide occurs when the algae from algal blooms becomes so numerous that it discolors the water. Overall Algae species are very tough and can survive in a wide range of environments, which can be seen as both a positive and negative situation. They contributed to the Earth being able to house life by producing oxygen through photosynthesis. There are few cases where they have been found on land such as rocks, trees, hot springs, etc… Species of algae have been well documented to be able to survive many harsh environments and have been on earth far longer than most living organisms to this day. Habitats for algae include any bodies of water including fresh and salt water, or have extreme external environment factors. Though similar to plants in the way they are both producers, algae have no stems or leaves and are more closely related to other groups of protists. Algae are autotrophs, meaning they use photosynthesis as their means of producing energy for themselves. Most species of algae are single-celled organisms but some species can be multi-cellular as seen in the photo above. “Multicellular Green Algae” by Frank Fox īefore going into what red tide is or how the populations of these microorganisms seem to be increasing significantly as oceans warm up, lets take a closer look at algae. During these specific months of warmer weather, billions upon billions of these microorganisms start to take over our oceans and can have many consequences for us. But why are the other months of the year not safe for people to eat shellfish? In short its because of the algae that grow during this time of year and as ocean temperatures rise. Ever been told to only eat shellfish during the months that have the letter “R”, (September-April)? Well this rule is actually pretty important for keeping the health of people safe and to allow for many species of shellfish to repopulate. ![]()
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