Shallow marine bays teem with life

Shallow marine bays are defined as sea areas less than four metres in depth, which are almost surrounded by the mainland. Such bays are diverse in terms of size, openness, water currents, and salinity. Of the habitats listed in the EU Habitats Directive, large shallow marine bays, coastal lagoons, and estuaries are all represented on the spectrum of shallow bays.

Particular attention is paid to the lagoons or flads, which are almost entirely cut off from the sea. Lagoons are protected by the Finnish Water Act.

Shallow marine bays have a diverse biota

The shallow marine bays deserve similar special attention. These sheltered bays are often surrounded by reed beds and are teeming with life, providing ecosystem services over a wide area, both on land and at sea.

Surface run-off waters carry both suspended solids and nutrients to the shore, much of which binds to either the shoreline sediments or aquatic vegetation. The flora is abundant and diverse and a large variety of invertebrate animals and insect larvae scurry about in the protection of its vegetation.

Some fish species, particularly pike, perch and roach, enter such shallow habitats to spawn, and their fish larvae begin their lives in these sheltered and gentle conditions. Larger fish, as well as water birds and waders, gather in such habitats to feed on the abundant fish juveniles and benthic invertebrates.

Many insects lay their eggs in the warm, calm waters of shallow marine bays, and the larval stages develop either within the bottom sediments or among the vegetation.

 Flower of a water lily floats in water in a shallow bay
Shallow marine bays are important areas for spring-spawning fish species such as perch.

Endangered aquatic plants thrive in shallow marine bays 

Most of the endangered aquatic plants of the Finnish coastline can be found in shallow coastal waters. The Nature Conservation Act prohibits any destruction and damage to their habitats. By protecting the unspoiled marine bays of special natural value, a wide range of biodiversity and ecosystem services can also be preserved effectively.

 Under water, the aquatic plants stretch towards the surface
Aquatic plants thrive in well-lit, shallow bays.