Water browning in the Evo area

Over the last decades, some surface waters (lakes, rivers) have become browner. Such phenomenon was observed throughout Finland and is referred to as water browning or brownification.

I have been studying browning in the Evo area since 2019 when I first came to Lammi Biological Station for a 2-month internship. I learned that browning led to a decline in aquatic invertebrate global abundance in Evo, and started to wonder about the impact of forestry activities practiced in the region on water colour.

Lake Valkea-Kotinen, my favourite place

I decided to come back in 2020 to carry on my studies on browning for my master’s thesis. My purpose was to investigate the contribution of forestry activities to changes in colour in Evo lakes and to highlight different aquatic invertebrate communities along a browning gradient.

My stay at LBS was very convenient and enjoyable as it is very close from Evo, where I had to perform fieldwork. Fieldwork was definitely my favourite part of my study. Evo is a beautiful area with its forest and lakes. I almost did not feel like I was doing fieldwork since I was so amazed by the Evo landscape.

Figure 2: invertebrate sampling

My fieldwork consisted in sampling aquatic invertebrates in 17 lakes of different characteristics: beaver-influenced, clear water, brown water and lakes located in protected areas. For that, I used activity traps (a method that has been traditionally used in Evo invertebrate surveys) in June 2020. Invertebrates were identified on the lake sites.

This fieldwork session highlighted that Evo lakes had different invertebrate communities as expected. For example, I found that copepods were negatively affected by browning, while isopods had higher abundance in brown waters. Other invertebrate families were affected by other environmental variables such as trichopterans that were found in higher abundance in protected lakes.

In parallel, I was also developing a method to identify clearcutting activity based on tree canopy cover. With this method, I was able to show that a high surface of clearcutting in the catchment of a lake led to high lake water colour. This demonstrated the contribution of forestry practices to the ongoing brownification of lakes.

Other interesting results came out of this study. Beavers, for instance, substantially affected lake water colour, which shows why their presence need to be considered in water quality studies in beavers distribution area. This study also demonstrated that lake cover had a significant impact on lake water colour. The more upstream lakes a lake has in its catchment, the less coloured it is. Adaptation of catchment management practices could be drawn out of these results.

More sampling

Lammi Biological Station is a place where many people share their research interest and their culture. I met many people that helped me with my research and that I could also help in return. It is always such a great experience to come to the station.

I successfully graduated in September 2020 in France and am in the process of writing scientific papers on the findings in my master’s thesis. In Finland, I found my vocation to carry out a research career. In June 2021, I will start a PhD at Helsinki University on brownification. I want to thank the foundation for supporting me throughout this journey in Finland.

Clarisse Blanchet is a 2020 LBAYS grant recipient