Algal Bloom

There is a wide range of algal species, ranging from the giant kelp of South America, to microscopic species. In a given area, some of the algae species will live on the sediment, others will live in the littoral zone, others will float at the surface, and some species will drift towards the depths of the water column. The life cycle of algae can be very different. 

Some species, such as pond scum and diatoms can reproduce by fragmentation. Some species cannot reproduce this way, but they have a life cycle where they spontaneously divide into several small species. Another method of sexual reproduction is meiosis, and some species have a meiotic division as a part of their life cycle. Microscopic life forms on the surface of the water column are known as metazoa (animal life) and phytoplankton.

What are Algal Blooms?

An algal bloom is a kind of algae who increases their population rapidly. They mainly live in freshwater or marine water systems and they are mainly recognised by the discoloration in the water with the help of their pigments. The term algae means a class which contains many types of aquatic photosynthetic organisms both microscopic and macroscopic in nature. As algal bloom is one of the rapid growing microscopic algae i.e they are unicellular in nature and one of the most common macroscopic algae is Kelp forest.

When there is little or no food available in the water, the phytoplankton will die. But when an abundance of food is present, the plankton cells can produce a large number of flagella and multiply very rapidly, thereby exceeding the capacity of the surrounding water to absorb them. As they grow, they eventually settle to the bottom and form visible concentrations of organisms called 'red tides'.

Algal blooms are formed due to various nutrients like nitrogen, phosphorus which enters from various fertilizers into the aquatic system and there they form algal blooms. They cause various effects on ecosystems like blocking of sunlight, depletion of oxygen level in water, secreting toxic material in water, etc. Due to all these harmful effects most of the time they lead to depletion of aquatic organisms.

What are the effects of an algal bloom? 

Algal blooms occur when the ratio of available food to algae, plankton is exceeded. If this ratio is greater than one to one, algae can grow faster than phytoplankton can be absorbed into the surrounding water. If there is a surplus of algae in a particular area, the phytoplankton will begin to accumulate, grow and settle out at the bottom of the water column. 

If the algal bloom accumulates in a particular area, then it will cause some changes in the water. For instance, an algal bloom can reduce light levels beneath the blooms. This will affect benthic (bottom-dwelling) invertebrates which are more sensitive to light then are the planktonic (floating-dwelling) invertebrates. 

It is important to note that algal blooms can occur at very different water depths and are only known to affect the waters within which they occur. For instance, if the algal bloom settles out at the very surface, then the invertebrates may find it very difficult to move down to shallower water. It is the ability of a water body to withstand this increased algal growth, that determines the size of the phytoplanktonic food chain that is able to grow in the presence of this algae.

What Causes Algal Bloom:

There are several factors which causes algal bloom in water bodies, they are given below:

1. Run of Nutrients: An algal bloom is mostly caused by the presence of nutrients like nitrogen, phosphorus in water. As these nutrients are washed by water from lands and agriculture areas that are heavily filled with nitrogenous and phosphatic fertilizers. Here rain acts as a washing agent, as they wash all the nutrients from soil and deposit all nutrients to water bodies i.e oceans, rivers, etc. Due to all this deposition of nitrates and ammonia in water bodies it causes algal bloom. Main reason behind this algal bloom is discharge of  untreated industrial waste directly into water bodies.

2. High Temperature: As depletion of ozone layer is happening due to global warming and this reason is a major factor behind tremendous growth in algal bloom. Appropriate temperature is needed for proper growth of algal bloom. As high temperature leads to rapid decompositions of the nutrients like nitrogen, phosphorus and these decomposed nutrients become easy for bacteria to use up and grow rapidly.

3. Presence of Dead Organic Material: There are so many varieties of bacteria which are present in water bodies as well as in the atmosphere.These bacteria lead to the growth of algae bacteria like all other bacteria. As nutrients in water along with dead organic matter leads to increase in growth of algal bloom.

4. Large Mass of Water: Large mass of water is needed for growth of algal bloom. As less disturbance in water propagation leads to tremendous growth of algal bloom.

Harmful Effects of Algal Bloom on Aquatic System:

Algal blooms leads to so many harmful effects on aquatic ecosystem, some of these harmful effects are given below:

1. Risk on Human Health and Life: As algal bloom produces toxin in water bodies which is indirectly consumed by human beings which further leads to fatal disorders or disease like itching, several skin related diseases, etc.

2. Death of Aquatic Animals: As each and every living organism needs proper supply of oxygen whether they live in water or on land. In the same way algal bacteria need oxygen for their survival for which they utilize the amount of oxygen present in the aquatic system, this leads to depletion in oxygen level and causes death of aquatic animals.

3. Leads to Starvation: Algal bloom feeds on important nutrients present in the aquatic system which leads to starvation situations in aquatic organisms as they dont get enough nutrients from the aquatic system and ultimately they lead to death of an affected organism.

Types of Algal Bloom:

Mainly there are three different types of algal bloom, they are:

1. Fresh Water Algal Bloom: They are formed due to deposition of extra nutrients especially phosphates, as these nutrients originated from fertilizers which are given to agricultural land. As higher concentration of nutrients leads to algal bloom formation in fresh water algal bloom. This bloom may also be absorbed in freshwater aquariums.

2. Ocean Bloom: This type of algal bloom is formed in large water reservoirs like the ocean. This algal bloom mainly destroys aquatic organisms in the ocean. They mainly lead to depletion of oxygen levels in oceans which have harmful effects on aquatic organisms.

3. Harmful Algal Bloom: A harmful algal bloom has a negative impact on the aquatic system, this impact can be in various forms like depletion of oxygen level, death of aquatic organisms, etc.

Negative Impact of Harmful Algal Bloom:

1. As it produces various toxins it leads to the death of aquatic organisms.

2. It increases liver disease in affected individuals.

3. Oxygen depletion in the aquatic system.

4. Disruption of epithelial gill tissues in fish, resulting in asphyxiation.

Important Terms on Algal Bloom:

1. Red Tide: It has similar meaning as harmful algal bloom which is found in coastal areas. Due to color and variation in growth harmful algal bloom is known as red tides. 

2. Eutrophication: The process of the oversupply of nutrients leading to algae growth and oxygen depletion is called eutrophication.