Greetings everybody
It is so nice to be back I had such an amazing time in the Cotswolds with my whole family and lovely weather to! So lets get back to the science of everything. You might remember a previous post regarding the algal bloom in Lake Erie 'Mummy why's the water green??'. Well in this weeks nature algal blooms have been catapulted to the forefront of my mind again and I think it is time we look a little deeper into it all. Unlike the algal bloom up top they are usually very harmful and carry serious consequences for both us and the ecosystem they have taken over.
What are algal blooms and what causes them?
Freshwater is a limited resource of ours yet it is essential for both our survival and that of many other organisms. Algal blooms are fast becoming a major environmental issue as it alters ecosystems and threatens human life.
Algal blooms in basic terms is the overgrowth of algae in large water bodies. At their peak they block sunlight from getting to aquatic plants, hindering their ability to carry out photosynthesis and oxygenate the waters. Essentially suffocating the water ecosystem. Interestingly, the distribution of algal blooms is wide and has made appearances in Lake Taihu in China, Lake Victoria in Africa and Lake Erie in North America.
Despite the name, the causative organism isn't just algae - it is also bacteria and phytoplankton. Fascinatingly some of the worst algal blooms (those most detrimental to human health) are caused by the bacterium belonging to Cyanobacterium. The name comes from the blue-green pigment that they are known to produce that also happens to be toxic!
Cyanobacterium Microcystis in particular is a common culprit behind many algal blooms. This bacterium forms extensive blooming areas and like others in its family produce toxins that can poison livestock and make the water undrinkable for humans.
How and why do they form?
Sadly the factors leading to an algal blooming event are very complex and as such it makes it tricky to stop them from forming. It has been found that environmental factors such as temperature, pH, day length, and the speed of flowing water play a role on providing the right environment for the blooms. Human agricultural practices have a role to play also, the over- enrichment of their soils with nutrients such as Nitrogen and Phosphorus have been found to have bloom 'promotion' effects in nearby water bodies. Below are several other factors that could lead to the increased occurrence of algal blooms.
Eutrophication:
As before mentioned algal blooms can be promoted through over enrichment of nearby soils. The process of Eutrophication is characterised by the increased availability of limiting growth factors that is needed for the process of photosynthesis (sunlight, carbon dioxide and nutrient fertilisers) eventually this process leads to the excessive growth of plant and algae.
Nutrient enrichment has occurred as a result of multiple human activities such as agriculture, industry and sewage disposal in or near aquatic systems that seep their way into the water when it rains. Below is an image showing the process of Eutrophication for your additional information.
Predator abundance:
Above are images of two common predatory fish found in the Baltic Sea; a Perch and a Pike. Years of research and experimental studies on food chains have showed that a disproportionate amount of importance lies with the top predators keeping the populations of prey species in check therefore having a top to bottom effect.
Despite this research populations of large predatory fish continue to spiral downwards. Researchers found that in areas of the Baltic Sea where Perch and Pike were low algal blooms subsequently began to form.
What they found was your typical food chain cascade. By knocking out the top predators through overfishing the species below them have gone unchecked and as such their populations increased. This increasing mid level predatory population led to decline in the numbers of snails and crustaceans also known as algae-eating species. The increasing population of algae allowed for the formation of blooms.
Interestingly this studies models indicated that areas of the Baltic Sea where population of perch and pike were intact has a 10% chance of suffering a bloom, however, this increased to 50% when predatory fish population dropped below a threshold value.
Climate change:
Yep it is this old chestnut again, however, just because you may feel as though people drone on and on about this environmental issue remember they do it because it is major.
Some of the biggest algal blooms that were harmful to the environment and humans alike have occurred during the last two years. Just last year Lake Erie suffered from a bloom that took over 200km of the lake at the same time another bloom formed just of the west coast.
Algal blooms, climate, temperature and the hydrological cycle are all closely linked to one another. It is a proven fact that our most dangerous water quality issues are exacerbated by the weather.
Lake Eries blooming event was characterised by the right set of conditions coming together at the right time. Prior to the blooming a series of extreme rainstorms leading to a record breaking discharge from rivers thereby flooding the lakes with an intense concentration of nutrients. Additionally the area had experiences above average temperatures as well as low level winds and a weak water circulation allowing the nutrients to remain in the lake for a longer period of time. All of these factors came together and allowed for the blooming of Microcystis cyanobacteria. To find out more about what went on in Lake Erie click here
That brings us to the conclusion of this post. Management and prevention of such events will be tricky as environmental factors are well beyond our control. However, the management of large predatory fish populations is a good place to start as indicated by that study.
Thats Biobunch,
Over and out
