Studying the bottom landscapes of Lake Ladoga with use of underwater vehicles

In 2019, the Institute of Limnology of the Russian Academy of Sciences (IL RAS) carried out geological and geomorphological studies of the bottom and shores of Lake Ladoga within the framework of the State project of the IL RAS No. 0154-2018-0003 / 5. The research included the study of the bottom landscapes of Lake Ladoga with help of a series of underwater vehicles Limnoscout, designed and assembled at the IL RAS.

Underwater photo and video of the bottom in the coastal zone was carried out by the Limnoscout-230 vehicle from a boat. Each video filming polygon  included 2 continuous video profiles of 1-2 km normal to the shore, and 1 connecting profile parallel to the shore of 200-400 m, in the deep part.

Underwater video filming of the bottom in the open water area of ​​the lake was carried out by the Limnoscout-50 vehicle from the board of the r/v “Poseidon”, by point diving, in which the bottom was shot within a radius of 2-4 m from the dive point.

Maximal deep of studies was 117 m.

All underwater surveys were accompanied by echo-sounding surveys and GPS tracking.

In total, 24 underwater video filming  polygons in the coastal zone and 23 underwater video filming points in the open water area of ​​the northern part of Lake Ladoga were worked out.

The collected extensive photo and video materials made it possible to make preliminary typology of the bottom landscapes of Lake Ladoga and evaluate their condition.

Several new important facts of the structure of the bottom of Lake Ladoga and biota distribution were discovered, in particular:

- For the first time on the bottom of Lake Ladoga, an invasive species of mollusk Dreissena polymorpha was discovered, which in other large lakes has a significant impact on ecosystems.

- For the first time at the bottom in the northern part of the lake, outlets of presumably Riphean sandstones were discovered, which significantly complements the geological picture of the area.

- For the first time at the bottom in the northeastern part of the lake an abnormally deep occurrence of coarse deposits was discovered, which is likely to be associated with the intense activity of glaciers.

The use of underwater photo and video in combination with traditional methods for studying the bottom landscapes of Lake Ladoga has shown the high efficiency of these methods. The studies will be continued.