Cyanobacterial Harmful Algal Blooms

Balint Lengyel

Algal blooms

• Algal blooms were observed throughout history, and the data suggests a increasing trend of occurrence, both in fresh water bodies, and the oceans.

• Weedy type algae includes members of Chlorophyta, species which can form mats and block the water surface. Several species of Cyanophyta can also form mats. These groups are responsible for most fresh water HABs.

• Dynoflagellates are responsible for most marine HABs, but Cyanobacteria can also become problematic in oceans.

Complex Issues

• Many different types of environments have potential risks of algal blooms. Wide range of circumstances can lead to various types of HABs. The different environments and the harmful species have to be studied independently to understand the causes and effects.

• The statistical records indicate that the environmental changes caused by humans are related with the increasing occurrence of HABs. Pollution, disturbance of ecosystems, and alteration of habitats increase the potential risks.

• The economic impact of these algal blooms can be significant, but people can also be directly effected.

• Cyanobacteria are particularly capable of rapid blooms, and to cause adverse effects.

Bloom type growth of filaments and colonies of the buoyant cells results in accumulation near the surface of the water body, especially at locations where the currents terminate.

The mats usually start to aggregate near the shore, and around partially submerged objects, and advance backward to the open waters. Depending on the surface area of the water body, the algae might cover up the entire surface.

With time, even large lakes can become entirely clogged.

The currents, the work of the waves and wind patterns at the site can be easily identified on the surface aggregation of cyanobacteria.

• Other then aesthetic nuisance cyanobacterial blooms can have serious adverse effects.

• These rapid changes can destroy entire ecosystems. Plants will die due to the lack of light, and later the animals can die out in the area, as their main food sources the plants disappear. This generalized collapse of the ecosystem can take time, but cyanobacterial blooms can result in much faster die off rates.

• Many cyanobacteria produce toxins, such as microcystins, nodularins, anatoxins, or methylamino alanine. People and their livestock, as well as wild animals can die after drinking from the poisonous waters.

• The economic cost of these conditions can be high, if the population in the area depends on the effected water bodies for domestic uses.

• The problem can have devastating consequences for aquacultures.

Results and Consequences in historical evidences and current observations

• Middle Eocene fossils in Messel, Germany contain evidence of large scale cyanobacterial poisioning events. Healthy appearing animals, form turtles to birds, and even horses were fossilized with sunken cyanobacterial mats.

• Waterbird death studies in Denmark, 1997 found evidence of anatoxin poisoning. In France dog deaths were described with the same reasons.

• In Australia, 1994, sheeps were poisoned by saxitoxins. The event was precisely studied, and it was concluded, that the death of the animals came about 4 minutes after they drank, as respiratory failure.

• Other study cases include deaths of flamingos, rhinoceroses, bees and bats.

• (Stewart, 2008)

Effected waters must be treated, and water purification is costly. Larger ponds’ problems might not be solved with traditional methods, and new management techniques have to be invented.

• Water purification, and biological filtering are the most common ways to mitigate the problems. These costly mechanical methods might provide drinkable water for people, but the problem is not solved by their applications.

• Algaecides can be directly added to the water, but these chemicals can have their own adverse effects on the remaining, as well as the later supposedly recovering ecosystems.

• Chemicals against cyanobacteria include Copper Sulfate, Sodium Carbonate Peroxyhydrate, as well as Titanium Dioxide. However, these chemicals will stay in the water after the algae are gone, and the method of their removal is not yet described.

• The best way might be to introduce other species, which either compete with the cyanobacteria, or which directly consume them. Recent studies with various invertebrate species suggest that inhibiting the CyanoHABs is possible without the destructive effects of the chemical compounds.

While most pond and small standing water bodies have high risk of Cyanobacterial blooms, without prevention and sustainable water management, even the Great Lakes are vulnerable.

Great Lakes CyanoHAB