Top-Down Control of Cyanobacteria: A Theoretical Analysis

Gragnani,; Scheffer,; Rinaldi,

doi:10.2307/2463895

Cited by 15 publications

(20 citation statements)

References 24 publications

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“…We assumed a seasonal succession from algal species with a highnutritional value (A) to algal species with a lownutritional value (B), thus simulating in situ seasonal succession from a spring crop of small edible algae to large colonial cyanobacteria. Following Gragnani et al (1999), we refer to these groups of algae that differ in their nutritional value as green algae and cyanobacteria, respectively. To keep the model as simple as possible, overwintering algae of type B are converted back into type A at the end of year.…”

Section: Methodsmentioning

confidence: 99%

Can overwintering versus diapausing strategy in Daphnia determine match–mismatch events in zooplankton–algae interactions?

et al. 2006

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Mismatches between predator and prey due to climate change have now been documented for a number of systems. Ultimately, a mismatch may have far-reaching consequences for ecosystem functioning as decoupling of trophic relationships results in trophic cascades. Here, we examine the potential for climate change induced mismatches between zooplankton and algae during spring succession, with a focus on Daphnia and its algal food. Whereas the development of an overwintering population of daphnids may parallel shifts in phytoplankton phenology due to climate warming, changes in the photoperiod-temperature interaction may cause the emerging population of daphnids to hatch too late and mismatch their phytoplankton prey. A decoupling of the trophic relationship between the keystone herbivore Daphnia and its algal prey can result in the absence of a spring clear water phase. We extended an existing minimal model of seasonal dynamics of Daphnia and algae and varied the way the Daphnia population is started in spring, i.e., from free swimming individuals or from hatching resting eggs. Our model results show that temperature affects the timing of peak abundance in Daphnia and algae, and subsequently the timing of the clear water phase. When a population is started from a small inoculum of hatching resting eggs, extreme climate warming (+6 degrees C) results in a decoupling of trophic relationships and the clear water phase fails to occur. In the other scenarios, the trophic relationships between Daphnia and its algal food source remain intact. Analysis of 36 temperate lakes showed that shallow lakes have a higher potential for climate induced match-mismatches, as the probability of active overwintering daphnids decreases with lake depth. Future research should point out whether lake depth is a direct causal factor in determining the presence of active overwintering daphnids or merely indicative for underlying causal factors such as fish predation and macrophyte cover.

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Section: Methodsmentioning

confidence: 99%

Can overwintering versus diapausing strategy in Daphnia determine match–mismatch events in zooplankton–algae interactions?

et al. 2006

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“…Moreover, in many lakes, the zooplankton grazers are generally food-limited in early summer, as in Dutch lakes, even before cyanobacteria have developed a sizable population (Gulati, 1989(Gulati, , 1990. Thus, limited grazing capability of zooplankters is often suggested as an explanation for a shift to cyanobacterial dominance following the spring grazing maximum of zooplankton (Sommer et al, 1986;Sarnelle, 1993; see also in Gragnani et al, 1999).…”

Section: Failure Of Cladoceran Zooplanktonmentioning

confidence: 99%

Lake restoration studies: Failures, bottlenecks and prospects of new ecotechnological measures

2008

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This paper critically reviews the published works on lake restoration in north-western Europe, with the aim to highlight the causes of failures of lake biomanipulation, and to identify the main bottlenecks that have impeded progress. More importantly, we explore the prospects of applying new ecotechnological measures to lakes with a focus on shallow lakes. These complementary measures are: (1) reduction of sediment resuspension; (2) water-level management; and (3) the use in shallow lakes of bivalves as effective grazers on lake seston, especially when cyanobacteria are dominant. If the sustainability of the positive effects of biomanipulation is considered over a decade, there are probably more cases of failures than successes. The failures can be ascribed to several bottlenecks that include: (1) inadequate reduction of allochthonous phosphorus (P) and an increase in autochthonous P inputs, i.e. release of P from the lake sediments following reductions of external P inputs; (2) poor edibility of filamentous and colonial cyanobacteria to daphnids; (3) inadequate coverage of the lake area by macrophytes partly due to foraging on the macrophytes by both fish and birds; (4) ineffective reduction of planktivorous fish biomass and our inability to maintain the fish mass to a 'low level' for longer periods; and (5) failure of northern pike (Esox lucius) after its transplantation to the lakes to develop a population level that can control planktivorous fish to desired low levels. Three potentially complementary ecotechnological measures are discussed. The first such measure concerns prevention of sediment resuspension in lakes by creating islands in order to minimise the wind fetch to reduce the wave amplitude. The second measure involves allowing greater water-level fluctuations (WLF) in lakes as planned in lowland countries like the Netherlands; WLF are likely to allow more space for water, and may lead to improved water quality and higher biodiversity. The third ecotechnological measure relates to grazer populations that complement herbivorous zooplankton to regulate phytoplankton, particularly to control cyanobacterial blooms. For this, the bivalve Dreissena polymorpha appears to be a good potential candidate for grazing on phytoplankton, especially in shallow eutrophic lakes that are dominated by filamentous and toxic cyanobacteria (e.g. Planktothrix agardhii and Microcystis aeruginosa).

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“…For lakes at least, their properties can be revealed by quite simple models (e.g. Gragnani et al, 1999;Lima et al, 2002), and can have very counterintuitive outcomes (Huppert et al, 2002). The fluctuations in water quality data for the small rivers shown in Fig.…”

Section: Discussion-a New Look At What Is Inadmissible Evidencementioning

confidence: 99%

“…Changing stoichiometries over ecologically significant time scales will only complicate the picture. A further complication arises because the underlying stochastic drivers of catchment systems, as well as the (self-organised) internal dynamics lead to the observed biodiversity (Gragnani et al, 1999;Huisman and Weissing, 1999); and we know that the biodiversity controls the overall function, often in idiosyncratic ways (Emmerson et al, 2001). While there are some overall patterns of response, dynamical simulation models do not predict the dynamics, emergence, contingency and biodiversity of real world systems.…”

Section: The Implications For Modelling and Predictionmentioning

confidence: 99%