Blue-green algal blooms are considered a major hazard to all the water supplies available for humans, and they are also very harmful to the health of humans, animals, and fish. They are caused by a prokaryotic species, Blue-green Algae, which is also known as Cyanobacteria. We are going to learn about Blue-green Algae in this article, and later in the article, we will also learn about Blue-green Algal blooms.
Blue-Green Algae: Introduction
Blue-green algae, also known as Cyanobacteria, are actually a type of bacterial family organism. Generally, blue-green algae look like green in color, but sometimes they also turn into blue color when scums are dying, and that's why it has been named Blue-green algae. They belong to a large heterogeneous group of prokaryotic organisms that are principally photosynthetic in nature. The reason behind naming algae as 'cyanobacteria' is that it resembles the eukaryotic algae in many ways that include ecological niches, morphological characteristics, and they were once treated as algae. When the classification of species occurred, Algae was reclassified as protists into a different Kingdom, and the prokaryotic nature of the Cyanobacteria caused them to be classified into the different prokaryotic Kingdom Monera with the other species of bacteria.
Blue-Green Algae: Structure
Like all the other prokaryotes present in Kingdom Monera, Blue-green Algae also lacks a Golgi apparatus, mitochondria, membrane-bound nucleus, endoplasmic reticulum, and chloroplasts. The functions which are carried out in the eukaryotes with the help of a membrane-bound nucleus are carried out by the Blue-green Algae by its bacterial cell membrane. Some of the Blue-green Algae, especially which are present in the planktonic form, have gas vesicles in them, which contribute to their buoyancy. Cyanobacteria contain only a single form of chlorophyll, i.e., chlorophyll á (which is a green pigment for the Photosynthetic nature organisms). In addition to this, Blue-green Algae also contains various centroids with yellowish color, the blue pigment phycobilin, and the red pigment phycobilin (in some species of them).
Blue-green Algae can be unicellular or filamentous, and many of them have sheaths present in them, which they use to bind other cells or filaments that are common in colonies of Cyanobacteria. The chemical, physiological and genetic characteristics of the Blue-green Algae are also used to classify this group under the Kingdom Monera. Because of the many other pigments present in them, some other species of this group are actually yellow, black, green, red, or brown in color. The Blue-green color of major species from the Cyanobacteria group is because of the combination of the chlorophyll and phycobilin present in them, and that's how they derived their popular name 'Blue-green Algae'.
Blue-green Algae: Nature and Occurrence
Because of the prokaryotic nature of Blue-green Algae (they are obligated phototrophs), most of them do not grow in the absence of light; however, some Cyanobacteria are also found in the dark places where a sufficient supply of glucose was available. Glucose, in turn, helps these organisms to fulfill their need for carbon and energy sources and help their growth in dark places.
In addition to the photosynthetic nature of the Blue-green Algae, many species of them are able to "fix" the atmospheric nitrogen, and that's why it is a known fact that they can transform the gaseous nitrogen from the atmosphere into multiple compounds, which is used by the living cells. The particular efficient nitrogen fixer types of Cyanobacteria are found in the filamentous species of the Blue-green Algae because these species have specialized cells known as heterocysts. The heterocysts present in the filamentous species of Blue-green Algae have thick-walled cell inclusions, and these thick-walled cell inclusions are impermeable to oxygen. Therefore, these heterocysts present in the Blue-green Algae provide them with an oxygen-free (anaerobic) environment, which is necessary for the operation of nitrogen-fixing enzymes. In Southeast Asia, these nitrogen-fixing species of Cyanobacteria are often found growing in the rice paddies, and thereby it eliminates any external supply of nitrogen fertilizers to rice paddies.
Blue-green Algae: Size and Distribution
The size of a common Cyanobacteria ranges from 0.5 to 60 micrometers, and that's how they represent the largest prokaryotic organisms present on the planet. Blue-green Algae can exist in places that are extremely common in freshwaters, and in such places, they are distributed widely and occur as a member of both the benthos and the plankton. Cyanobacteria are also represented abundantly in habitats such as tidal spray zones, tide pools, and coral reefs, and a few species of Blue-green Algae also exists in the ocean plankton. If we talk about land, the Blue-green Algae are common in the soil to a depth of approx. 40 inches (equal to 1 meter) or way more. Other than this, Blue-green Algae is also found growing on most surfaces of trees and rocks, where they appear in the form of layers or cushions.
You can also find Blue-green Algae flourished in some of the most inhospitable environments, which includes all kinds of extreme environments. For example, Cyanobacteria can be found on the lower surfaces of many rocks in deserts, in cold lakes underneath 5m of an ice pack, and in hot springs. Blue-green Algae are said as the first colonizers of bare soil and rocks, which makes their origin very old. Due to their existence in almost every type of environment, various types of association can be observed between Blue-green Algae and other organisms. Some species of Blue-green Algae grow a mutualistic relationship with the fungi, which in turn form a composite organism known as lichens.
Blue-green Algae: Reproduction
Blue-green Algae or Cyanobacteria follow most of the other species from the kingdom Monera in the reproduction pattern as they also reproduce asexually. The reproduction in Blue-green Algae takes place either by spore formation and fragmentation in the filamentous species or by means of binary and multiple fission in the unicellular and colonial form. If favorable conditions are provided to Cyanobacteria, they can reproduce at a very high or, we can say, explosive rate, which in turn forms a dense concentration of them known as blooms.
Now, we will study Blue-green Algal blooms in this article and learn how these can be harmful to us.
Blue-green Algal Blooms:
'Bloom' is a term that is generally used to describe an accumulation of an enormous number of algal cells to a point in some water body where they discolor the water, produce unpleasant odors and tastes, forms scum, affect water quality, and reduce the fish population. Even the decomposition of algae can also cause an increase in the number of fish killed because of the depletion of oxygen in the water body.
Blue-green Algal bloom is caused because of explosive increase in the number of Blue-green Algae in a water body and when these species become dominant in that water body. Following are the major reasons for which blue-green algae species may dominate and increase excessively in a water body:
Here, we have discussed all the reasons for which blue-green algae blooms occur in a water body.
The duration of Blue-green Algal blooms can vary from a few weeks to months, and it all depends mainly on the conditions of the water body and the weather around it. It is even observed that an increase in the flow of water or wind, and cooler weather can prevent and even reduce the blooms from a water body. When the bloom dies, the cells of Blue-green Algae present in the bloom tend to become 'leaky.' Many times, when a bloom contains species that produce toxins, then it may result in the release of toxins into the surrounding water. Once the toxins are released from the bloom in the water, they can persist even for up to three months or more before they start degrading.
Blue-Green Algae: Potential risks
If Blue-green Algae or Cyanobacteria start multiplying at a high rate and grow in number tremendously, the toxin will also be produced on a large scale in the water. It will cause multiple health issues in humans, domestic animals, fishes, and livestock who come in contact with the contaminated water. It will also be harmful to recreational users who come in contact with this water. In the past, many cases of eye and skin irritation, muscle cramping, and nausea have been reported due to water contaminated with the toxins produced by cyanobacteria.
Following are the harmful effects which the Blue-green Algae can cause on our health and the surroundings:
These are all the major harmful effects and potential risks of Blue-green Algae to human life as well all the living species around the water body in which Cyanobacteria is present.