Mapping and modelling of the spatial distribution of benthic macrovegetation in the NE Baltic Sea with a special focus on the eelgrass Zostera marina Linnaeus, 1753
Date
2017-06-21
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Abstract
Eesti rannikumere põhjataimestiku uuringute ajalugu ulatub 18. sajandisse. Merepõhjast proovide kogumist sukelduja poolt või pinnalt põhjaammutite abil alustati Eestis 1959. aastal. 2005. aastaks sai eesmärgiks süstematiseeritud teabe kogumine ja ulatuslike merealade kaardistamine ning seetõttu võeti lisaks kasutusele videouuringud, kaugseire, hakati enam rakendama ruumilist modelleerimist. Videomeetod on teiste meetodite kõrval tänapäevani laialt kasutuses ning videopõhised hinnangud on piisavad põhjaelustiku kaardistamiseks koosluste tasandil. Kaugseire võimaldab lühikese ajaga koguda infot ulatuslike alade kohta. Selle abil saab Läänemeres põhjakoosluseid kaardistada kuni 6 m sügavusel rannikuvees ning väljatöötatud koosluste klassifikatsiooniskeemid ja levikukaardid võimaldavad muuhulgas liigipõhiste uuringute optimaalsemat planeerimist.
Pikk merihein on Eesti rannikumere liivastel põhjadel üks olulisemaid võtmeliike. Meriheina kooslustega seotud liikide arv, kokku 35 põhjataimestiku ning 33 põhjaloomastiku liiki, moodustab umbes neljandiku meie merepiirkonna põhjaelustiku liikide arvust. Aastatel 2005–2015 tuvastati üle 300 pika meriheina kasvukoha. Ulatulikest uuringutest selgus, et liik on tavapärane kogu Eesti rannikumeres, välja arvatud madala soolsusega Soome lahe idaosas ning Pärnu lahes. Pikk merihein kasvab peamiselt sügavusvahemikus 2–5 m ning üle 3 m sügavusel on see meie liivastel põhjadel ainus suure tihedusega kooslusi moodustav taim. Pika meriheina levikuala, kus liigi katvus ületab 10%, on hinnanguliselt 150 km2. Modelleerimine näitas, et liik on vastupidav suurtele keskkonnatingimuste muutustele ning tuleviku kliima stsenaariumi kohaselt mõjutavad liigi levikut peamiselt merevee soojenemine, vee liikumiskiiruse tõus ning laguneva jää poolt põhjustatud mehaaniline häiring. Meie rannikumere mitmete teiste võtmeliikide püsimine on tuleviku kliima tingimustes otseselt ohustatud ning seega on liigilise mitmekesisuse säilitamisel äärmiselt oluline terviklik merekeskkonna käsitlus. Antud doktoritöö annab selle terviku mõistmiseks olulise panuse
The first phytobenthic investigations in Estonia are known from the 18th century. Sampling of Estonian coastal sea benthic communities began in 1959; the main survey methods were diving and physical sampling of the seabed. Demands for large-scale mapping of marine areas evoke the use of videosampling, remote sensing and spatial modelling. Since 2005 videosampling has been widely used. The continuous video mode is precise enough for mapping benthic macrophyte communities. The used remote sensing classification schemes produced accurate high-resolution maps at 0-6 m depth with a potential to distinguish larger groups of macrophytes. The results provide an important cost-effective input when planning targeted large-scale mapping of e.g. eelgrass. Eelgrass is an ecosystem engineering species in moderately exposed sandy substrates of the NE Baltic Sea. A total of 33 macrophytobenthic and 35 invertebrate taxa were found in samples from eelgrass stands in the coastal waters of Estonia. The findings correspond to about a quarter of the total benthic species richness in the area. In 2005–2015 eelgrass was found in more than 300 locations. The species spreads all over the Estonian coastal sea, except the easternmost low salinity parts of the Gulf of Finland and the turbid and diluted Pärnu Bay. Its main depth range is 2–5 m. The area of eelgrass coverage of higher than 10% is estimated at about 150 km2. Our modelling study showed that eelgrass is very resilient to a broad range of environmental perturbation and that eelgrass is most affected by changes in physical disturbances such as seawater warming, elevated wave-induced current velocity and reduced ice scour. As many of the benthic key species are negatively affected by the expected future climate, a modelling of the cover of eelgrass under the future climate is essential in order to help managers to establish marine protected areas that can resist the projected influences of climate change and thereby minimize the loss of biodiversity.
The first phytobenthic investigations in Estonia are known from the 18th century. Sampling of Estonian coastal sea benthic communities began in 1959; the main survey methods were diving and physical sampling of the seabed. Demands for large-scale mapping of marine areas evoke the use of videosampling, remote sensing and spatial modelling. Since 2005 videosampling has been widely used. The continuous video mode is precise enough for mapping benthic macrophyte communities. The used remote sensing classification schemes produced accurate high-resolution maps at 0-6 m depth with a potential to distinguish larger groups of macrophytes. The results provide an important cost-effective input when planning targeted large-scale mapping of e.g. eelgrass. Eelgrass is an ecosystem engineering species in moderately exposed sandy substrates of the NE Baltic Sea. A total of 33 macrophytobenthic and 35 invertebrate taxa were found in samples from eelgrass stands in the coastal waters of Estonia. The findings correspond to about a quarter of the total benthic species richness in the area. In 2005–2015 eelgrass was found in more than 300 locations. The species spreads all over the Estonian coastal sea, except the easternmost low salinity parts of the Gulf of Finland and the turbid and diluted Pärnu Bay. Its main depth range is 2–5 m. The area of eelgrass coverage of higher than 10% is estimated at about 150 km2. Our modelling study showed that eelgrass is very resilient to a broad range of environmental perturbation and that eelgrass is most affected by changes in physical disturbances such as seawater warming, elevated wave-induced current velocity and reduced ice scour. As many of the benthic key species are negatively affected by the expected future climate, a modelling of the cover of eelgrass under the future climate is essential in order to help managers to establish marine protected areas that can resist the projected influences of climate change and thereby minimize the loss of biodiversity.
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Keywords
fütobentos, merihein, kooslused, liigiline koosseis, keskkonnategurid, levikukaardid, modelleerimine (teadus), rannikumeri, Läänemeri, Eesti, phytobenthos, seagrass, biocenosis, species composition, environmental factors, distribution maps, modelling (science), coastal sea, Baltic Sea, Estonia