Water Management Strategies Against Toxic Microcystis Blooms In The Dutch Delta

Abstract

Abstract. To prevent flooding of the Dutch delta, former estuaries have been impounded by the building of dams and sluices. Some of these water bodies, however, experience major ecological problems. One of the problem areas is the former Volkerak estuary that was turned into a freshwater lake in 1987. From the early 1990s onward, toxic Microcystis blooms dominate the phytoplankton of the lake every summer. Two management strategies have been suggested to suppress these harmful algal blooms: flushing the lake with fresh water or reintroducing saline water into the lake. This study aims at an advance assessment of these strategies through the development of a mechanistic model of the population dynamics of Microcystis. To calibrate the model, we monitored the benthic and pelagic Microcystis populations in the lake during two years. Field samples of Microcystis were incubated in the laboratory to estimate growth and mortality rates as functions of light, temperature, and salinity. Recruitment and sedimentation rates were measured in the lake, using traps, to quantify benthic-pelagic coupling of the Microcystis populations. The model predicts that flushing with fresh water will suppress Microcystis blooms when the current flushing rate is sufficiently increased. Furthermore, the inlet of saline water will suppress Microcystis blooms for salinities exceeding 14 g/L. Both management options are technically feasible. Our study illustrates that quantitative ecological knowledge can be a helpful tool guiding large-scale water management.

Genetic diversity of inorganic carbon uptake systems causes variation in CO2 response of the cyanobacterium Microcystis

“…Microcystis is a widespread genus that can produce the toxin microcystin (MC) and develops dense blooms in many eutrophic lakes and brackish waters across the globe (Chen et al, 2003;Orr et al, 2004;Verspagen et al, 2006;Tonk et al, 2007;Paerl and Huisman, 2008;Michalak et al, 2013). Our analysis reveals genetic diversity in the presence/ absence of the bicarbonate uptake genes bicA and sbtA among Microcystis strains.…”

Planktonic and benthic cyanobacteria of European brackish waters: a perspective on estuaries and brackish seas

“…MC-producing Microcystis blooms have been reported in European brackish waters (Rocha et al, 2002;Karlsson et al, 2005;Verspagen et al, 2006) and a bloom of M. aeruginosa has been recorded from the Minho River estuary (Portugal) that contained MC-LR (MC with leucine and arginine) and another variant of MC that is as yet uncharacterized (Vasconcelos & Cerqueira, 2001). In the Guadiana estuary (Portugal) the presence of MCs has also been reported, produced either by Microcystis or Oscillatoria species (Sobrino et al, 2004).…”

“…and Anabaena spp. (Wille´n & Mattsson, 1997;Rocha et al, 2002;Verspagen et al, 2006). Filamentous forms of Pseudanabaena and the unicellular Cyanodictyon, Cyanonephron, Aphanothece, Aphanocapsa and Cyanocatena have also been recorded in brackish-water environments of the Baltic Sea, but less frequently than the genera already mentioned (Lehtima¨ki et al, 2000;Finni et al, 2001;Rocha et al, 2002;Stal et al, 2003;Surakka et al, 2005).…”

“…Finni et al, 2001;Verspagen et al, 2006). Recently, the occurrence of cyanobacteria in brackish water has come more into the spotlight, following the discovery by Miller et al (2010) of a clear link between deaths of 21 marine otters and a thriving toxic bloom of Microcystis in a Californian estuary.…”

“…In these brackish waters, the most dominant cyanobacteria reported have been Oscillatoria spp., Microsytis aeruginosa, Planktothrix spp., Anabaena spp., as well as some unidentified picocyanobacteria (Rocha et al, 2002;Lehman et al, 2005;Verspagen et al, 2006;. In brackish waters of NW Spain, less frequent cyanobacteria such as Aphanocapsa conferta, Gomphosphaeria salina, Gloeocapsa deusta, Gloeocapsa granosa, Aphanothece stagnina, Gloeothece palea, Xenococcus pyriformis, Phormidium papyraceum, Spirulina labyrinthiformis, Symploca funicularis, Hassalia bouteillei, Tolypothrix tenuis, Nodularia spumigena and Rivularia nitida have also been reported (Calvo & Rbara, 2003).…”