To find out the climate change effects on lakes in Latvia, its impact on toxic algae blooming and how that could affect human health, in 2015 - 2016 Institute for Environmental Solutions in cooperation with Latvian Institute of Aquatic Ecology carried out a holistic survey of the Burtnieks and Alūksne Lake’s food-chain. Also to raise the awareness and expand the local knowledge on climate change effects on lake ecology and introduce the local community with scientific research methods scientists introduced local community members and school children to participate the research.
The researchers found out that both lakes are very different. For instance, Lake Burtnieks has faced several ecological problems including intensive algae blooming during summer months. Previous studies show that in Burtnieks there are already 11 species of toxic algae. The Alūksne Lake is in relatively good ecological condition. However, during the last 5 years researchers have identified a rapid growth of a unique algae species Gloeotrichia echinulata in the Alūksne Lake.
Because of the climate change – the temperature has risings rappidly over past 40 yeas, therefore the weather conditions in Latvia from May to October is warm enough for blue-green algae to increase their growth and proliferation. They prevent other algae species to grow, thus reducing the food base for other stages of the food chain. Furthermore, they produce the harmful toxins that are traveling through the food chain and can end up in the human body. So far, scientists have found two types of toxins in blue-green algae: neurotoxin and hepatotoxin. Neurotoxin is harmful to human nervous system, while hepatotoxin is damaging to the liver. Recently, scientists have found a new toxin – neurotoxin BMAA. It occurs in every blue-green algae. It causes neurodegenerative disorders, also known as Amyotrophic Lateral Sclerosis – Parkinson Dementia Complex.
During the research project “Enhancing Society’s Understanding about Climate Change Effects on Lakes in Latvia” that has been financed by EEA financial mechanism the researchers found out the spread of the toxins in fish communities and counted the amount of fish that could be harmful for human to consume.
Algae toxins have been found in all fish species that have been researched. The highest concentrations of algae toxins researchers found in fish liver. A part of the toxins have been transferred to the other organs – gonads, kidneys and muscles. However, the toxin concentrations in muscles are 20 times lower than those that have been found in the liver.
There are considerable differences reveals in the amount of toxins in fish of various sizes. Bigger fish contain lower amount of algae toxins. The plankton-eating fish of the Alūksne Lake contain of higher concentrations of algae toxins. On the contrary, the higher concentrations of toxins have found in carnivorous fish of Lake Burtnieks. Perhaps, it indicates that plankton-eating fish are living in the shore where vegetation are able to accumulate more biomass of algae and their toxins. Lake Burtnieks is very shallow, therefore, with the help of wind and mixing of water the toxins reach also the carnivorous fish that usually live the deepest part of the waterbody.
As the World Health Organisation has acclaims person whose weight is 70 kg on a daily basis can consume 2.8 mg MC-LR (the most common toxin in freshwaters). It means that the person can eat c.a. 1.1 kg and 25-45cm of roach’s fillet that has been cached in the Alūksne Lake. While from 25-35 cm roach that has been cached in the same lake, the person may eat just 0.24 kg of its fillet. Researchers warn – people should be very careful with the amount of fish they feed their pets. The average weight of a cat is only 4 kg, so relatively small amount of roach could be harmful to cat’s health.
In the Summer of 2015 the local community of Alūksne and Burtnieki, municipality representatives, students, media and others participated science workshops. And during the field work and data gathering of Autumn researchers carried out together with the local school children. During the four science workshops participants got to know lake food chain, ecological condition and learn how the climate change can affect the lake. They collected fish samples, sorted them, measured and analysed the content of fish stomach. Scientists demonstrated shellfish ability to filter lake’s water. While, through the microscope the participants were able to see how does zooplankton and phytoplankton, that lives in lake ecosystems looks like.
To reach the wider audience and bring the message about the research conclusions further, as an end of the project the conference of climate change effects of Latvia’s waterbodies was held. It gathered the attention from different municipality members, media, environmental protection specialists, students and others. During the discussions the participants confirmed that they can actually see the indicators that show the effects of the climate change, in the same time, there are a lot of other factors that affect lake ecology. As a conclusion of the discussion, it was clear that for smart and sustainable management solutions the information based on scientific research and common action of various stakeholders is crucial.