Effects of climate variability on interactions between cyanobacteria and associated microheterotrophs-consequences for development of toxic cyanobacterial blooms

最近对新鲜和微咸湖泊浮游植物季节性动态的研究，特别是对德国北部湖泊无环蓝藻华的研究表明，多种相互作用而不是单个机制是导致蓝藻华发展的原因。温度的变化是导致蓝藻与异养菌在共生、寄生、共生等方面相互作用发生显著变化的关键因素之一。这些变化影响了季节性优势模式，也可能导致先前同步的食物网脱钩。通过使用普通和潜在有毒的蓝藻（spumigena Nodularia, Anabaena spp., aentinosa Microcystis (flos-aquae)）的纯培养物与自然和确定的异养细菌群落孵育，拟议的项目旨在实验验证以下假设：a)温度升高导致蓝藻和异养细菌之间的相互作用发生严重变化，b)由于蓝藻和异养细菌之间的紧密耦合，异养细菌群落组成的变化将影响蓝藻的发育，并可能导致目前同步的食物网脱钩（不匹配）。关于特定异养细菌群落作用的潜在机制将使用分子（系统发育）以及经典的微生物（生理学）方法进行研究。

Recent studies on seasonal dynamics of phytoplankton in fresh and brackish lakes, in particularly on acyclic cyanobacterial blooms in lakes of Northern Germany, suggest multiple interactions rather than individual mechanisms being responsible for the development of cyanobacterial blooms. Variability of temperature is one key factor leading to marked changes in interactions between cyanobacteria and heterotrophic bacteria in terms of symbiosis, parasitism, commensalisms etc. These changes affect the seasonal dominance pattern and may also lead to a decoupling of previously synchronised food webs. By using pure cultures of common and potentially toxic cyanobacteria (Nodularia spumigena, Anabaena spp., Microcystis aentginosa (flos-aquae) incubated with natural and defined communities of heterotrophic bacteria the proposed project aims to experimentally test the following hypotheses: a) Rising temperatures cause severe changes in interactions between cyanobacteria and heterotrophic bacteria, b) Due to a tight coupling between cyanobacteria and heterotrophic bacteria changes in the community composition of heterotrophic bacteria will impact the development of cyanobacteria and may cause decoupling of presently synchronised food webs (mismatch). Underlying mechanisms concerning the role of specific heterotrophic bacterial communities will be investigated using molecular (phylogeny) as well as classical microbiological (physiology) methods.