Algal Bloom: Definition, Meaning Causes, Importance, Types

What Is Algae?

Algae represent a wide group of photosynthetic organisms occurring in different aquatic environments. They range from microscopic phytoplankton to large seaweeds. This, therefore, implies that algae form the most critical part of the ecosystem, as primary producers, through their ability to convert sunlight into energy by photosynthesis, hence forming the base of the aquatic food web.

Latest: NEET 2024 Paper Analysis and Answer Key 

Don't Miss: Most scoring concepts for NEET | NEET papers with solutions

New: NEET Syllabus 2025 for Physics, Chemistry, Biology

NEET Important PYQ & Solutions: Physics | Chemistry | Biology | NEET PYQ's (2015-24)

Algae can be found in single-celled, colonial, multicellular forms, as in the case of kelp. They form the base of the aquatic food chain and implementations for producing oxygen; however, their growth sometimes gets out of control, resulting in an algal bloom.

Importance Of Algae

Algal bloom research can contribute majorly to the understanding of their effects on the environment, economy, and human health. On an ecological note, algal blooms may result in a disruption in oxygen levels of aquatic ecosystems, hence fish and other aquatic life mortality. Economically, they may damage fisheries, tourism, water treatment processes, and the like, leading to huge losses.

In addition, several phytoplankton blooms can form toxins that influence human and animal health. They could contaminate drinking water intakes, cause illness, or even death. Therefore, monitoring and managing algal blooms becomes very critical to address concerns relating to ecological balance and public health.

What Is An Algae Bloom?

An algal bloom is a sudden increase in the population of algae in an aquatic system and may result in visible changes, discolouring the water. Blooms can occur in fresh and saline waters and are driven by some physical, chemical, and biological factors.

Algal bloom is divided further into harmful and non-harmful blooms. Harmful algal blooms produce toxins that may have adverse effects on aquatic life, human beings, and other animals. Non-harmful blooms, though non-toxic, may cause environmental problems such as hypoxia, leading to a situation when oxygen is low in the water.

Algal blooms are not anything new, but recently, due to increasing human activities like agricultural runoff, wastewater discharge, and rising climate change, their intensity and frequency have gone up. Therefore, the probability of forming an algal bloom is a must for any strategies to prevent or control it.

Types Of Algal Blooms

The various types of algal blooms are defined as:

Harmful Algal Blooms (HABs)

The harmful algal blooms result from algae producing toxins poisonous to aquatic life, humans, and animals. Common types of harmful algae include cyanobacteria also known as blue-green algae, dinoflagellates, and diatoms. They result in fish kills, shellfish poisoning, and other health problems.

Non-Harmful Algal Blooms

They do not produce toxins, but nontoxic algal blooms still have major ecological implications. For example, they can produce hypoxia, which creates dead zones where no aquatic life can live. It can block sunlight from going down to underwater plants and throw off the aquatic food chain.

Cause Of Algal Bloom

Algal blooms are caused by these reasons:

Nutrient Pollution (Nitrogen And Phosphorus)

The excess nutrients, mostly nitrogen and phosphorus, are key reasons behind algal blooms. Normally, these nutrients get into the water body from agricultural runoff, discharging of wastewater, or other industrial processes. High nutrient levels increase the growth rate of algae, promoting blooms.

Light Availability

Light is yet another essential element required in algal blooms. It is linked to photosynthesis, and high light availability in clear shallow waters favours high populations of algae. Seasonal variability can, however, still affect light penetration onto shallow areas, as can water turbidity.

Water Temperature

The water temperature displays a bias towards warmer conditions, with most blooms occurring in summer. Climate change is, therefore, raising the water temperature, likely to lead to significantly more frequent and serious algal blooms.

Water Movement And Stability

Stable water conditions characteristic of stagnant or slow-flowing waters tend to favour algal blooms. On the contrary, the turbulent nature of waters can disperse algae and limit bloom formation. Human activities, in particular on rivers by way of damming and flow alteration, create the perfect conditions for blooms.

Process Of Algal Bloom Formation

The steps of the process of the formation of algal bloom are:

Initial Conditions

Algal blooms usually arise once they encounter favourable conditions like nutrient-rich water, good sunlight, and appropriate water temperatures. It is the phase at which the growth rate of algae heightens in that they start reproducing fast, thereby increasing in terms of population.

Rapid Growth Phase

At this stage, the algae reproduce exponentially, thereby giving an effect of increased population visibly. Such quick growth may give the water either a green red or brown colouring, depending on the variety of algae.

Peak Bloom

At peak bloom, algae are at their highest concentration in the bloom. This can range from days to a few weeks dependent on the environment and nutrient availability.

Decline Phase

Gradually, most of the available nutrients become exhausted by the algae, after which the growth rate slows down. The decline phase is characterized by a drop in the algal population that can lead to dying and decaying of algae, further depleting oxygen content in water and possibly leading to hypoxia.

Effects Of Algal Blooms

Algal Bloom has the following effect:

Effects On Aquatic Ecosystems

During an algal bloom, algae cover large areas of the surface, preventing sunlight from reaching the bottom and using up much of the oxygen in the water. Optimization under such conditions, however, is impossible without toxin production. Such changes can cause the death of fish and other aquatic organisms, which shifts food webs and ecosystem dynamics.

Hypoxia And Dead Zones

Large quantities of algae, upon decomposition, consume oxygen in the water and create hypoxic conditions. It can create dead zones whereby aquatic life cannot survive in the event, hence huge ecological damage.

Impact On Fisheries And Tourism

Algal blooms could bring about death to fish and shellfish, hence hurting commercial and recreational fisheries. Besides, they could deter tourism to affected areas, therefore hitting the economy of the local area that relied on it.

Toxins And Their Effects On Humans And Animals

Blooms of harmful algae produce toxins that contaminate such sources as drinking water, seafood, and recreational waters. It is one of the things that might engender several health issues in man, like breathing problems, skin irritation, gastrointestinal illness, among others, and in cases involving high dosages, death in both human beings and animals.

Prevention And Control

Several measures can be taken for the prevention and control of algal blooms

Nutrient Management

Algal bloom occurrence can be avoided by reducing agricultural runoff, wastewater, and industrial nutrient inputs. This would include procedures for best management practices, including buffer strips and reduced fertilizer application, to minimise nutrient pollution.

Mechanical Removal

The processes mechanically remove algae from the surface of the water body with the help of mechanical equipment like skimmers and harvesters. Algal harvesting techniques may work well in small areas; however, this method might not be practical with large or widespread blooms.

Chemical Treatments

Chemical treatment, like applying algaecides, is one of the potential controls for algal blooms. However, such treatments may result in unintended ecological consequences and should be used with caution.

Biological Control Methods

Biological control methods would include the use of natural predators or competitors in controlling the algal population. For example, certain fish species that feed on algae may be introduced to control the bloom. These methods are mostly environment-friendly and sustainable.