Sandy coasts

Abstract

1. Sandy coasts, including the epilittoral part of sandy beaches and the shallow sandy sublittoral, are particularly extensive in the southern and southeastern part of the Baltic Sea. 2. In the Baltic Sea ecosystem, sandy coasts function as biocatalytic filters by decomposing organic matter (including detritus) most of which originates directly or indirectly (e.g. Via waterbirds) from the sea. 3. Sandy coasts are unstable, erodable environments which change in time and space due to e.g. Erosion in winter and deposition of sand on the beaches in summer, and to the constant shifting of the substrate by winds and currents. 4. The sandy epilittoral and shallow sublittoral habitats support a variety of life forms, from microbes to birds, and are the space in which diverse processes involved in energy flow and matter cycling operate at different temporal and spatial scales. 5. The sandy coast food webs are partly based on the direct input of solar energy and nutrients used by primary producers (phytoplankton, microphytobenthos, macrophytes) whose production is subsequently utilised by invertebrates (meiobenthos, macrozoobenthos), fish and birds. 6. Another part of the sandy coast food webs is based on the input of organic material in the form of detritus, a source of energy for microbial communities consisting of bacteria, fungi, yeasts and actinomycetes as well as of heterotrophic protists living attached to sand grains and in the interstices. 7. Birds collect invertebrate prey from the sand on the beach or from the shallow sublittoral and contribute to the organic matter pool of the sandy habitat. 8. The sandy coasts of the Baltic Sea experience heavy anthropogenic pressure which primarily involves tourism and recreation, but also effects of eutrophication, establishment of non-indigenous species, sand extraction and dredging, fishing, infrastructure and shore defence constructions.