Algal bloom
[5] Since algae is a broad term including organisms of widely varying sizes, growth rates, and nutrient requirements, there is no officially recognized threshold level as to what is defined as a bloom.
[11] Along coastal regions and in freshwater systems, agricultural, city, and sewage runoff can cause algal blooms.
Depending on the organism, its pigments, and the depth in the water column, algal blooms can be green, red, brown, golden, and purple.
[2] Bright green blooms in freshwater systems are frequently a result of cyanobacteria (colloquially known as "blue-green algae") such as Microcystis.
For example, Gymnodinium nagasakiense can cause harmful red tides, dinoflagellates Gonyaulax polygramma can cause oxygen depletion and result in large fish kills, cyanobacteria Microcystis aeruginosa can make poisonous toxins, and diatom Chaetoceros convolutus can damage fish gills.
[22] In lakes that are stratified in the summer, autumn turnover can release substantial quantities of bio-available phosphorus potentially triggering algal blooms as soon as sufficient photosynthetic light is available.
[citation needed] When phosphates are introduced into water systems, higher concentrations cause increased growth of algae and plants.
[citation needed] Blooms may be observed in freshwater aquariums when fish are overfed and excess nutrients are not absorbed by plants.
These are generally harmful for fish, and the situation can be corrected by changing the water in the tank and then reducing the amount of food given.
[citation needed] Algal blooms in freshwater systems are not always caused by human contamination and have been observed to occur naturally in both eutrophic and oligotrophic lakes.
[27] Cyanobacteria are able to retain high phosphorus uptake in the absence of nutrients which help their success in oligotrophic environments.
Tiny molecules found inside these microscopic plants harvest vital energy from sunlight through photosynthesis.
The natural pigments, called chlorophyll, allow phytoplankton to thrive in Earth's oceans and enable scientists to monitor blooms from space.
Satellites reveal the location and abundance of phytoplankton by detecting the amount of chlorophyll present in coastal and open waters—the higher the concentration, the larger the bloom.
Observations show blooms typically last until late spring or early summer, when nutrient stocks are in decline and predatory zooplankton start to graze.
[37] Because human exposure can take place by consuming seafood products that contain the toxins expelled by HAB algae, food-borne diseases are present and can affect the nervous, digestive, respiratory, hepatic, dermatological, and cardiac systems in the body.
[38] Beach users have often experienced upper respiratory diseases, eye and nose irritation, fever, and have often needed medical care in order to be treated.
If the HAB event results in a high enough concentration of algae the water may become discoloured or murky, varying in colour from purple to almost pink, normally being red or green.
[citation needed] Dinoflagellates are microbial eukaryotes that link bioluminesce and toxin production in algal blooms.
Harmful algae blooms have a large effect on the Great Lakes St. Lawrence River Basin.
Harmful algae blooms continue to infect water supplies at the Binational Great Lakes Basin and due to the world’s recovery from the Covid-19 Pandemic, solving the issue has become a low priority.
This economical problem has become part of politics in the United States, whereas in allied countries such as Canada there is low concern, as well.
For example, in August 2024 the growth of the toxic algae, Pseudo-nitzschia, along California coasts were making sea lions sick and aggressive to beach goers.
The growth of Pseudo-nitzschia leads to the production of a dominic acid which accumulates in fishes such as sardines, anchovies, and squids.
