Rapport nr 112: Kartering av vattenlevande makrofyter längs två inner-ytterskärgårdsgradienter på nordvästra och sydöstra Åland
SCHEININ, M; SÖDERSTRÖM, S (2005)
SCHEININ, M
SÖDERSTRÖM, S
Åbo Akademi, Husö biologiska station
2005
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This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.
Julkaisun pysyvä osoite on
https://urn.fi/URN:ISBN:952-12-1637-9
https://urn.fi/URN:ISBN:952-12-1637-9
Tiivistelmä
As assigned by the Provincial Government of Atand Islands, a dive mapping of aquatic macrophytes (macroscopic algae and plants) was carried out in the archipe/ago of Aland Islands. The survey was done a/ong two gradients reaching from the innermost to the outermost parts of the archipe/ago. The gradients were /ocated in the North-Western and South-Eastern parts of the archipe/ago. Macrophytes are sessi/e primary producers, which can easi/y be observed visual/y. Hence, they are preferable as indicator organisms in investigating the state of aquatic environments. The purposes of the survey were to prepare a thorough description of the macrophyte communities and the environmental factors affecting them, to campare the communities in different parts of the gradients and the archipe/ago, as we/1 as to constitute a basis for future monitoring of these communities in the archipelago of Atand.
Both inner-outer-archipe/ago gradients were divided inta five hypothetica/ zones based on the levet of physica/ exposure. Three or four mapping sites were included in every zone. Within the zones, the sites were located to describe the environment in the mast comprehensive manner. Areas objective to direct anthropogenic effects were avoided. The mapping was carried out by visua/ observations. The methodo/ogy was based on a modified version of the guidelines for mapping of rocky-bottom flora, by the Finnish Environment lnstitute (SYKE). The macrophyte communities were investigated qualitative/y and quantitatively along a 50 m /ong transect, which was p/aced at right angle to the shore-line. lf required, the vertica/ limits for the distribution of the macrophytes were noted outside the transect. At every site and zone, several biotic and abiotic environmenta/ parameters, which direct/y or indirect/y can affect the composition of macrophyte communities, were a/so observed.
Altogether, 49 species of macroa/gae and plants were encountered. The number of species was lowest in the inner archipelago, increased prominent/y towards the middle parts of the gradient and decreased slight/y towards the outer archipelago. The mast important factor affecting the composition and number of species was bottom type, which, in its tum, was mainly determined by the leve/ of physica/ exposure and the amount of nutrients in the water. In the inner archipe/ago the bottom consisted mostly of soff substrates, in the midd/e archipe/ago of a mixture of saft and hard substrates, and in the outer archipe/ago principal/y of hard substrates. The content of macroa/gae in the species composition increased along the gradient from the inner to the outer archipelago, where the number of a/ga/ species was highest. The concentration of nutrients, levet of anthropogenic effects and temperature decreased along the gradient from inner to outer archipe/ago, whereas the levet of physical exposure, underwater visibility and, thus, the vertica/ distribution of the macrophytes increased. In comparison, the North-western gradient was less affected by anthropogenic activities and possessed /ower concentrations of nutrients, higher number of species and greater underwater visibility than the South-eastern gradient.
Both inner-outer-archipe/ago gradients were divided inta five hypothetica/ zones based on the levet of physica/ exposure. Three or four mapping sites were included in every zone. Within the zones, the sites were located to describe the environment in the mast comprehensive manner. Areas objective to direct anthropogenic effects were avoided. The mapping was carried out by visua/ observations. The methodo/ogy was based on a modified version of the guidelines for mapping of rocky-bottom flora, by the Finnish Environment lnstitute (SYKE). The macrophyte communities were investigated qualitative/y and quantitatively along a 50 m /ong transect, which was p/aced at right angle to the shore-line. lf required, the vertica/ limits for the distribution of the macrophytes were noted outside the transect. At every site and zone, several biotic and abiotic environmenta/ parameters, which direct/y or indirect/y can affect the composition of macrophyte communities, were a/so observed.
Altogether, 49 species of macroa/gae and plants were encountered. The number of species was lowest in the inner archipelago, increased prominent/y towards the middle parts of the gradient and decreased slight/y towards the outer archipelago. The mast important factor affecting the composition and number of species was bottom type, which, in its tum, was mainly determined by the leve/ of physica/ exposure and the amount of nutrients in the water. In the inner archipe/ago the bottom consisted mostly of soff substrates, in the midd/e archipe/ago of a mixture of saft and hard substrates, and in the outer archipe/ago principal/y of hard substrates. The content of macroa/gae in the species composition increased along the gradient from the inner to the outer archipelago, where the number of a/ga/ species was highest. The concentration of nutrients, levet of anthropogenic effects and temperature decreased along the gradient from inner to outer archipe/ago, whereas the levet of physical exposure, underwater visibility and, thus, the vertica/ distribution of the macrophytes increased. In comparison, the North-western gradient was less affected by anthropogenic activities and possessed /ower concentrations of nutrients, higher number of species and greater underwater visibility than the South-eastern gradient.