Patterns of macrophyte distribution and productivity in coastal ecosystems: effect of abiotic and biotic forcing
Date
2013-08-05
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Abstract
Ökoloogia põhieesmärk on mõista elustiku levikumustrite muutusi ja põhjuseid looduskeskkonnas. Enamus varasemaid uuringuid on teostatud väikestes ruumimastaapides ning isegi kui tööd viidi läbi ulatuslikel aladel, jäid kogutud punktandmete vahele suured uurimata alad. Käesolevas doktoritöös kombineeriti edukalt masinõppe algoritme statistilise modelleerimise, kaugseire ja traditsioonilise ruumimodelleerimisega, selleks et ennustada põhjataimestiku ja selgrootute liikide katvusmustreid meremaastikel. Mudelid näitasid lainetuse, sügavuse ja põhjasette suurt rolli põhjaelustiku ruumimustrite kujunemisel. Madalaveeliste liikide levikut kirjeldasid enim tuulelainetus ning sügavaveeliste liikide levikut ranniku geomorfoloogia. Täiendavad eksperimentaaluuringud näitasid eluta keskkonnategurite ülekaalukat mõju põhjataimestiku fotosünteetilisele produktsioonile. Isegi rannikumere madalaveelistel aladel, kus valgust peaks olema piisavalt, kannatasid suurem osa põhjataimestliku kooslustest valguslimitatsiooni all. Katsed näitasid, et kooslustele oli iseloomulik väga stabiilne fotosünteetiline produktsioon. Seega ei täida põhjataimestik vaid bioloogilise mitmekesisuse säilitamise ülesannet, vaid tagab muutuvate keskkonnatingimuste juures ka stabiilse fotosünteetilise produktsiooni.
The ultimate goal in ecology is to understand biotic patterns, processes and their changes in nature. The vast majority of studies have been performed on limited spatial scales even though the studies covered larger areas than the grain size i.e. the size of sampling units still remained small and vast areas between grains were left unstudied. In the current thesis the machine learning technique combined with statistical modelling, remote sensing and traditional spatial modelling variables succeeded in identifying and testing effects of abiotic environmental predictors on the coverage of benthic macrophyte and invertebrate species from local to seascape scales. In general, exposure to waves and partly water depth and sediment characteristics were the best predictors of the distribution patterns of benthic species. Overall, wind patterns best explained variability in the coverage of shallow water species whereas coastal geomorphology largely contributed to the models of deep water species. Supporting field experiments also demonstrated the strong importance of abiotic forcing to the photosynthesis of macroalgae. Specifically, in coastal environments, where light is supposedly plentiful, macroalgal communities are nevertheless strongly light limited. The experiments also showed that photosynthetic production was more stable at community than species level. Thus, the canopy-forming algae are not just providers of biodiversity but also provide stable photosynthetic production (i.e. food and habitat resource) through the large range of hydrographical conditions.
The ultimate goal in ecology is to understand biotic patterns, processes and their changes in nature. The vast majority of studies have been performed on limited spatial scales even though the studies covered larger areas than the grain size i.e. the size of sampling units still remained small and vast areas between grains were left unstudied. In the current thesis the machine learning technique combined with statistical modelling, remote sensing and traditional spatial modelling variables succeeded in identifying and testing effects of abiotic environmental predictors on the coverage of benthic macrophyte and invertebrate species from local to seascape scales. In general, exposure to waves and partly water depth and sediment characteristics were the best predictors of the distribution patterns of benthic species. Overall, wind patterns best explained variability in the coverage of shallow water species whereas coastal geomorphology largely contributed to the models of deep water species. Supporting field experiments also demonstrated the strong importance of abiotic forcing to the photosynthesis of macroalgae. Specifically, in coastal environments, where light is supposedly plentiful, macroalgal communities are nevertheless strongly light limited. The experiments also showed that photosynthetic production was more stable at community than species level. Thus, the canopy-forming algae are not just providers of biodiversity but also provide stable photosynthetic production (i.e. food and habitat resource) through the large range of hydrographical conditions.
Description
Väitekirja elektrooniline versioon ei sisalda publikatsioone.
Keywords
vetikad, fütobentos, levik (biol.), bioproduktiivsus, keskkonnategurid, algae, phytobenthos, distribution, bioproductivity, environmental factors