Spatio-temporal patterns of native and invasive zooplankton species under changing climate and eutrophication conditions
Date
2011-07-27
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Abstract
Eutrofeerumist, kliimamuutusi ja bioinvasioone peetakse olulisteks teguriteks, mis võivad tõsiselt ohustada rannikumere koosluste stabiilsust. Samas pole olemas ühte kindlat ruumiskaalat, millel nende muutuste mõju elusloodusele uurida. Üheaegselt mõjutavad ökosüsteemi nii laial skaalal toimuvad protsessid kui ka vaid kohalikul tasandil toimunud muutused. Käesolevas töös hinnati, kuidas erinevatel ruumiskaaladel toimivad troofsuse- ja kliimamuutujad mõjutavad Soome lahe zooplanktoni biomassi, seda nii kohalike kui võõrliikide puhul. Samuti kirjeldati nelja Läänemerre elama asunud võõrliigi Balanus improvisus, Marenzelleria neglecta Cercopagis pengoi ja Evadne anonyx populatsioonide dünaamikat ja ökoloogilist mõju Eesti vetes. Zooplanktoni koosluse dünaamika oli mõjutatud nii klimaatiliste tingimuste kui ka eutrofeerumise teguritest ja seda kõikidel uuritud ruumiskaaladel. Enamike liikide puhul olid kõige vähem mõjuvateks, kuid siiski olulisteks teguriteks just väikseima ehk lokaalse skaala keskkonnatingimused. Samas ei olnud kliima ja eutrofeerumise muutujate koosmõju zooplanktoni liikidele oluliselt suurem kui nende mõju eraldi võetuna. Käsitletud võõrliikide vaatlused näitavad, et nende biomass on viimastel aastatel näidanud tõusutrendi. Võõrliigi Cercopagis pengoi tihedus oli korrelatsioonis nii klimaatiliste tingimustega kui ka näiteks teiste vesikirpude liikidega, kuid olulist seost eutrofeerumisega selle liigi puhul ei leitud. Röövtoidulise Cercopagis pengoi mõju oma potensiaalsele saakloomale avaldus peamiselt saaklooma populatsiooni paiknemisena sügavamates veekihtides nendes jaamades, kus röövloom esines suure arvukusega. Värskeima võõrliigi Evadne anonyx arvukus on seni jäänud madalaks.
Eutrophication, climate change and bioinvasions are ranked among the major threats to the stability of the marine coastal environment and can have severe impacts on near-shore biodiversity and functioning, but there is no single natural scale at which the effects of eutrophication and climate should be studied. The contribution of eutrophication and climate variables estimated at local, gulf and regional scales to the biomass of native and invasive zooplankton species in a shallow brackish water ecosystem of the Baltic Sea was evaluated in this thesis. Population dynamics and ecological impacts in north-eastern Baltic Sea of four established alien species: Balanus improvisus, Marenzelleria neglecta, Cercopagis pengoi and Evadne anonyx, was described in this thesis. The study demonstrated that eutrophication and climate variables largely explained the observed patterns in zooplankton communities and most species were affected by environmental variability at all spatial scales. Both eutrophication and climate variables describe a substantial amount of the variability in the models of mesozooplankton species. On the other hand, the interactive effect of eutrophication and climate variables on mesozooplankton was not significant. The abundance of Cercopagis pengoi was best explained by climate variables and the densities of selected cladocerans while eutrophication had no significant effect on it within a broad range of spatial and temporal variability. The effect of predatory Cercopagis pengoi on the potential prey species Bosmina coregoni maritima was revealed as changed vertical distribution of the pray species by the presence of the predator. Although it still has low densities, Evadne anonyx will most likely further increase in abundance and colonize new areas in the Baltic Sea.
Eutrophication, climate change and bioinvasions are ranked among the major threats to the stability of the marine coastal environment and can have severe impacts on near-shore biodiversity and functioning, but there is no single natural scale at which the effects of eutrophication and climate should be studied. The contribution of eutrophication and climate variables estimated at local, gulf and regional scales to the biomass of native and invasive zooplankton species in a shallow brackish water ecosystem of the Baltic Sea was evaluated in this thesis. Population dynamics and ecological impacts in north-eastern Baltic Sea of four established alien species: Balanus improvisus, Marenzelleria neglecta, Cercopagis pengoi and Evadne anonyx, was described in this thesis. The study demonstrated that eutrophication and climate variables largely explained the observed patterns in zooplankton communities and most species were affected by environmental variability at all spatial scales. Both eutrophication and climate variables describe a substantial amount of the variability in the models of mesozooplankton species. On the other hand, the interactive effect of eutrophication and climate variables on mesozooplankton was not significant. The abundance of Cercopagis pengoi was best explained by climate variables and the densities of selected cladocerans while eutrophication had no significant effect on it within a broad range of spatial and temporal variability. The effect of predatory Cercopagis pengoi on the potential prey species Bosmina coregoni maritima was revealed as changed vertical distribution of the pray species by the presence of the predator. Although it still has low densities, Evadne anonyx will most likely further increase in abundance and colonize new areas in the Baltic Sea.
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Keywords
zooplankton, populatsioonidünaamika, keskkonnamuutused, troofsus, eutrofeerumine, võõrliigid, Läänemeri, eutrophication, zooplankton, Baltic Sea, climate change, alien species, trophic state