Benthic–pelagic coupling in the population dynamics of the harmful cyanobacterium Microcystis

Abstract

General rightsIt is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulationsIf you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: http://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. 2. We monitored changes in pelagic and benthic populations of Microcystis in Lake Volkerak, The Netherlands. In addition, sedimentation rates and the rate of recruitment from the sediment were measured using traps. These data were used to model the coupling between the benthic and pelagic populations and to calculate the contribution of overwintering benthic and pelagic populations to the magnitude of the pelagic summer bloom. 3. Changes in the benthic Microcystis population showed a time lag of 3-14 weeks compared with the pelagic population. This time lag increased with lake depth. The largest amount of benthic Microcystis was found in the deepest parts of the lake. These observations suggest horizontal transport of sedimented Microcystis from shallow to deep parts of the lake. 4. Recruitment from and sedimentation to the sediment occurred throughout the year, with highest recruitment and sedimentation rates during summer. Model simulations indicate that the absence of benthic recruitment would reduce the summer bloom by 50%. 5. In spring, the total pelagic population was three to six times smaller than the total benthic population. Yet, model simulations predict that the absence of this small overwintering pelagic population would reduce the summer bloom by more than 64%. 6. Reduction of the overwintering pelagic populations, for instance by flushing, may be a useful management strategy to suppress or at least delay summer blooms of Microcystis.

Different tolerances and responses to low temperature and darkness between waterbloom forming cyanobacterium Microcystis and a green alga Scenedesmus

“…Compared to colonial Microcystis, the cell number of unicellular Microcystis had a significant decrease, suggesting that colonial Microcystis can survive a longer period under the stress of darkness and low temperature than unicellular Microcystis. This may be an explanation why Microcystis colonies were found in winter at the bottom of freshwater lakes (Reynolds et al, 1981;Tsujimura et al, 2000;Brunberg & Blomqvist, 2002;Latour et al, 2004a;Verspagen et al, 2004Verspagen et al, , 2005. Our previous study also indicated that colonial Microcystis exhibited more tolerance to copper than unicellular Microcystis (Wu et al, 2007), supporting that higher endurance to environmental stresses might play an important role in survivals of colonial Microcystis.…”

Changes in abundance and community structure of bacteria associated with buoyantMicrocystiscolonies during the decline of cyanobacterial bloom (autumn–winter transition)

“…To our knowledge, this is the first report on microbial communities associated with buoyant Microcystis colonies, which would take an important role during the next summer bloom (Verspagen et al, 2005), during the decline period of annual freshwater bloom. qRT-PCR revealed a gradual decrease in the ratio of bacteria associated with Microcystis colonies, indicating that Microcystis colonies remaining buoyant on the water surface are resistant to bacterial colonization.…”

Effect of temperature on recruitment of cyanobacteria from the sediment and bloom formation in a shallow pond

“…This result is consistent with the in situ observation that the population density of Microcystis species in the water increased with water temperature. The upward movement of Microcystis species is obviously regulated by cell buoyancy, and some researchers have suggested a positive effect of temperature on the recovery of buoyancy in Microcystis colonies or an increase in the number of buoyant colonies (Thomas & Walsby 1986, Tsujimura et al 2000, Brunberg & Blomqvist 2003, Verspagen et al 2005. Therefore, Microcystis colonies in the sediment are probably stimulated to become active quickly in response to an increase in temperature.…”