Algal Bloom

Algal Bloom is a rapid increase in the algal population in waterbodies, often leading to visible discolouration of the water. Algal bloom causes include various factors including nutrient enrichment that help in excessive algal growth. Algae play crucial roles in aquatic ecosystems, serving as primary producers and oxygen suppliers. While essential for ecosystem health, unchecked algal growth can lead to disruptive blooms which deplete oxygen levels which is dangerous for marine life. In this article, we will cover algal bloom, its causes, and more.

What is Algal Bloom?

Algal bloom occurs when algae in water bodies grow excessively forming a thick layer of visible discolouration on the surface. An Algal bloom is a type of algae that reproduces at a high rate. This phenomenon is often due to excess nutrients from sources like agriculture or urban runoff, along with warm temperatures and calm conditions. The term ‘algae‘ refer to a group of aquatic photosynthetic organisms that can be microscopic or macroscopic in size. Algal blooms are microscopic algae that grow quickly and are unicellular in nature, and the kelp forest is one of the most prevalent macroscopic algae.

While algae are essential for ecosystems, excessive growth can lead to problems. Some blooms produce toxins harmful to aquatic life and humans, while others deplete oxygen levels, suffocating marine organisms. For instance, Lake Erie on the border of US and Canada experiences annual blooms due to nutrient runoff, impacting water quality and endangering wildlife.

Phytoplankton will die if there is little or no food available in the water. When there is plenty of food, however, plankton cells can develop a huge number of flagella and reproduce quickly, far outnumbering the capacity of the surrounding water to absorb them. They eventually settle to the bottom and generate visible concentrations of organisms known as ‘red tides’ as they mature.

Causes of Algal Bloom

Algal blooms in aquatic bodies are caused by a variety of sources,

• Run off Nutrients: The presence of nutrients such as nitrogen and phosphorus in the water causes algal bloom. These nutrients are washed away by water from fields and farm areas where nitrogenous and phosphatic fertilizers are used heavily. Rain functions as a washing agent, washing all nutrients from the soil and depositing them in water bodies such as seas, rivers, and lakes. An algal bloom is caused by the accumulation of nitrates and ammonia in water bodies. The main cause of this algal bloom is the direct release of untreated industrial waste into bodies of water.
• High Temperature: As the ozone layer depletes as a result of global warming, this is a major element in the explosive expansion of algal blooms. For proper algal bloom growth, the temperature must be just right. Because high temperatures cause rapid decomposition of nutrients such as nitrogen and phosphorus, bacteria may easily consume and develop these destroyed nutrients.
• Presence of Dead Organic Material: Bacteria can be found in a wide variety of places, including aquatic bodies and the environment. These bacteria, like all other bacteria, promote the growth of algae microorganisms. Algal blooms grow faster when nutrients in the water combine with dead organic waste.
• Large Mass of Water: Algal blooms require a large amount of water to grow. Less disruption in water propagation results in a massive algal bloom.

Effects of Algal Bloom on Water

When the ratio of available food to algae and plankton is exceeded, algal blooms occur. Algae can develop faster than phytoplankton can be absorbed into the surrounding water if this ratio is more than one to one. If there is an abundance of algae in one place, phytoplankton will begin to gather, expand, and settle out at the bottom of the water column.

If an algal bloom forms in a specific location, it will alter the water’s characteristics. An algal bloom, for example, can lower light levels beneath the blooms. This will have an impact on benthic (bottom-dwelling) invertebrates, which are more light-sensitive than planktonic (floating) invertebrates.

It’s worth noting that algal blooms can occur at a variety of water depths and are only known to have an impact on the waterways in which they occur. Invertebrates, for example, may find it difficult to travel down to shallower water if the algal bloom settles at the very surface. The extent of the phytoplanktonic food chain that can grow in the presence of this algae is determined by a water body’s ability to endure increased algal growth.

Effects of Algal Bloom on Aquatic Life

The harmful effects of algal blooms on waterbodies are:

Oxygen Depletion

During algal blooms, excessive growth of algae can lead to oxygen depletion in water bodies through the process of eutrophication. As algae die and decompose, microbial activity consumes oxygen, creating hypoxic or anoxic conditions that can suffocate fish and other aquatic organisms.

Toxicity

Some algal species produce toxins during blooms, known as harmful algal blooms (HABs), which can poison aquatic organisms and even pose risks to human health through contaminated seafood consumption. These toxins can affect the nervous system, liver, and other organs, leading to diseases or death in marine mammals, fish, birds, and shellfish.

Habitat Degradation

The dense biomass of algae during blooms can smother and shade underwater habitats, such as coral reefs, seagrass beds, and rocky substrates, inhibiting the growth of other organisms and disrupting ecosystem dynamics. This habitat degradation can reduce biodiversity and alter species composition, impacting the overall health of aquatic ecosystems.

Altered Nutrient Dynamics

Algal blooms alter nutrient dynamics in aquatic ecosystems, leading to imbalances and nutrient deficiencies or excesses. Excessive nutrient inputs, often from agricultural runoff or wastewater discharge, fuel algal growth and promote bloom formation, making nutrient pollution worse and its associated ecological impacts.

Economic Losses

Harmful algal blooms can result in significant economic losses for industries dependent on healthy aquatic ecosystems, such as fisheries, aquaculture, tourism, and recreational activities. Fish kills, beach closures, and declines in water quality can disrupt livelihoods and local economies, highlighting the far-reaching consequences of algal bloom events.

Examples of Algal Bloom

Some of the various examples of algal bloom around the globe are:

• Microcystis aeruginosa: Cyanobacterium responsible for toxic blooms in freshwater bodies.
• Karenia brevis: Dinoflagellate causing harmful red tides in marine environments.
• Prymnesium parvum: Alga associated with fish kills and water discoloration.
• Alexandrium spp.: Dinoflagellate species producing paralytic shellfish toxins.
• Pseudo-nitzschia spp.: Diatom genus linked to amnesic shellfish poisoning events.
• Cochlodinium spp.: Dinoflagellate resulting in fish mortality and water coloration.

Types of Algal Bloom

The different types of algal bloom are:

• Fresh Water Algal Bloom: They form as a result of the deposition of additional nutrients, particularly phosphates, which come from fertilizers applied to agricultural land. In freshwater, increasing nutrient concentrations lead to the production of algal blooms. Freshwater aquariums may also absorb this bloom.
• Ocean Bloom: Algal blooms of this type form an enormous water reservoir, such as the ocean. This algal bloom is mostly responsible for the death of aquatic species in the ocean. They mostly cause oxygen depletion in oceans, which has negative consequences for aquatic life.
• Harmful Algal Bloom: A harmful algal bloom has a negative impact on the aquatic system, which can take numerous forms such as oxygen depletion, aquatic organism death, and so on.

Conclusion – Algal Bloom

In conclusion, algal blooms represent a complex ecological phenomenon with significant implications for aquatic ecosystems and human activities. These blooms occur when algae proliferate rapidly, often due to excess nutrients, warm temperatures, and calm conditions, leading to visible discoloration on the water surface. While algae are essential components of aquatic ecosystems, excessive growth can result in harmful effects such as oxygen depletion, toxicity, habitat degradation, altered nutrient dynamics, and economic losses. Understanding the causes, effects, and types of algal blooms is essential for effective management and conservation of water resources and aquatic environments.

FAQs on Algal Bloom

What is Another Name for an Algal Bloom?

Another name for an algal bloom is “phytoplankton bloom” or “algae bloom.”

What Causes Eutrophication?

Eutrophication is caused by excess nutrients, such as nitrogen and phosphorus, entering water bodies, leading to excessive algal growth.

What is the Disease Algal Bloom?

Harmful algal blooms (HABs) can cause various diseases, including paralytic shellfish poisoning (PSP), neurotoxic shellfish poisoning (NSP), and amnesic shellfish poisoning (ASP), when contaminated seafood is consumed.

What is an Algal Bloom Class 11?

In Class 11, an algal bloom is studied as a phenomenon where algae grow excessively in water bodies, often due to nutrient enrichment and favorable environmental conditions.

What Causes an Algal Bloom?

Excessive nutrients, warm temperatures, and calm conditions typically cause algal blooms by promoting rapid algae growth.

What is a Harmful Algal Bloom?

A harmful algal bloom (HAB) is an algal bloom that produces toxins harmful to aquatic life and humans, posing risks to public health and ecosystems.