K307 Elsi

Small coastal lagoons under human pressure


Roosa Mikkola
Anette Bäck


The Quark region in the Baltic Sea is known for high postglacial rebound; the isostatic land uplift measuring up to 8,5 mm/year, providing 700 ha new land area annually. This forms the landscape continuously, and gives rise to unique features that are characteristic to the area, like the many small lagoons, so called flads, found along the coast. During the land uplift process, new bays emerge as old ones get cut from the sea and build small isolated water areas. The restricted water exchange with the surrounding sea creates distinctive conditions forming important habitats for many species, such as reproduction sites for fish. Shallow bays are ecosystem service providers at a large scale (Austin et al. 2017) but are under high human pressure as they are preferred sites for recreational use. Dredging and boat traffic as well as land runoff highly alter these delicate environments. Today over 60% of these shallow coastal lagoons have been modified by human activities.
Climate change and the subsequent sea level rise is a new upcoming threat, that will have considerable effects on these fragile ecosystems. The current upper predicted sea-level rise is 9mm a year which means that the “birth of new land” would stop since sea level rise would be equal to land uplift (Poutanen & Steffen 2014). This leads to a decrease in emerging new flads which raises the importance of protecting current flads by a) gathering knowledge of biological and physiochemical data b) raising the awareness regarding potential damage causing actions.
The Quark area has approximately 2500 flads and shallow bays. Out of these, 33 in Finland and 19 in Sweden were chosen for closer research. Different parameters such as temperature, salinity and pH were measured. The amount of pike, perch and roach as well as their hatchlings were investigated. This data will be compared with physiochemical data, vegetational data maintained by aerial mapping and snorkeling for information about preferred spawning sites.
The aim is to gather the data from the 52 well studied areas and then interpolate on all the other bays in the Quark area. By modelling the results on other flads in the region we will be able to evaluate ecosystem services that flads offer and make assumptions of their function as fish reproduction areas. We will be able to draw conclusions about human induced impacts on the functioning of the ecosystem.

Austin, Å. N., Hansen, J. P., Donadi, S., & Eklöf, J. S. (2017). Relationships between aquatic vegetation and water turbidity: A field survey across seasons and spatial scales. PloS one, 12(8), e0181419.

Poutanen, M., & Steffen, H. (2014). Land Uplift at Kvarken Archipelago/High Coast UNESCO World Heritage area. Geophysica, 50(2).