Effect of reservoir drawdown on biomass of three species of aquatic macrophytes in a large sub-tropical reservoir (Itaipu, Brazil)

Thomaz, Sidinei Magela; Pagioro, Thomaz Aurélio; Bini, Luis Maurício; Murphy, K. J.

doi:10.1007/978-1-4020-5390-0_8

Cited by 20 publications

(36 citation statements)

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“…The physical and chemical changes occurring during floods allow macrophytes development. On the one hand, the fast colonization of free‐floating macrophytes would be associated to the phosphorous increase registered on March in the water column (from 0.1 to 2 mg/L of P‐PO4), and to a marked decreasing salinity (Chaparro et al ., ), in agreement to observations described in other studies (Haller et al ., ; Thomaz et al ., ). On the other hand, emergent macrophytes are able to regenerate the aerial biomass lost during droughts (Esteves and Suzuki, ).…”

Section: Discussionmentioning

confidence: 97%

Effect of Spatial Heterogeneity on Zooplankton Diversity: A Multi-Scale Habitat Approximation in a Floodplain Lake

2013

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Environmental heterogeneity is an essential quality of ecosystems as it has important implications in community structure. Macrophytes are a main component of environmental heterogeneity in floodplain lakes, and their dynamics are highly influenced by water level changes. In this context, we analysed at different spatial scales the relationship among hydrological variations, environmental heterogeneity associated to macrophytes and zooplankton regional diversity (γ diversity) in a South American floodplain lake adjacent to the Paraná River, and we also compared the local zooplankton diversity (α diversity) among the different environments that comprised the lake heterogeneity. At very low waters, the environmental heterogeneity was reduced as the lake was mainly limited to open water areas with low zooplankton diversity. At high waters, the profuse vegetation development (emergent and free‐floating), in mixed or homogeneous patches, determined a higher lake environmental heterogeneity with enhanced regional zooplankton diversity; littoral species increased over limnetic ones. Zooplankton α diversity was higher in environments with free‐floating macrophytes than in those without these plants. The structural complexity in the water column provided by plant roots would be closely related to the enhanced diversity found under free‐floating mats. This study contributes to the knowledge on the effects of strong water level variations on environmental heterogeneity, which is strongly associated to macrophytes and on zooplankton diversity, and highlights the role of free‐floating plants as diversity hosts and ‘key structures’ in floodplain lakes. Copyright © 2013 John Wiley & Sons, Ltd.

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Section: Discussionmentioning

confidence: 97%

Effect of Spatial Heterogeneity on Zooplankton Diversity: A Multi-Scale Habitat Approximation in a Floodplain Lake

2013

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“…In other words, the aquatic macrophyte assemblages were spatially organised in the entire reservoir and in most of the reservoir’s arms. Until 1999, the reservoir had experienced long‐term stability in terms of water level (usually fluctuating <1 m year −1 ; Thomaz et al. , 2006), which provided suitable environmental conditions for macrophyte assemblage development.…”

Section: Discussionmentioning

confidence: 99%

“…Some species that may become extinct as a result of a drawdown disturbance can return within a few months after the water level has re‐established (e.g. submersed species; Thomaz et al. , 2006) and recolonise the open area.…”

Section: Discussionmentioning

confidence: 99%

“…In other words, the aquatic macrophyte assemblages were spatially organised in the entire reservoir and in most of the reservoir's arms. Until 1999, the reservoir had experienced long-term stability in terms of water level (usually fluctuating <1 m year )1 ; Thomaz et al, 2006), which provided suitable environmental conditions for macrophyte assemblage development. According to Townsend (1989), this type of environment is called niche controlled, having low temporal heterogeneity, and with competition and resource partitioning playing strong roles.…”

Section: Discussionmentioning

confidence: 99%

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The immediate and long‐term effects of water drawdown on macrophyte assemblages in a large subtropical reservoir

2012

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Summary 1. Disturbances play a central role in determining the spatial and temporal dynamics of many plant communities. In our study of macrophyte assemblages at 150 sites in five arms of a large subtropical reservoir (Itaipu Reservoir, Brazil–Paraguay border), we used co‐occurrence null models and spatiotemporal analyses to describe the patterns in the assemblages during a historically large water drawdown in 2000, in comparison with the previous year (1999) and subsequent years (2001–07). A C‐Score co‐occurrence index tested the null hypothesis of random structure during the drawdown period. A detrended correspondence analysis and multiresponse permutation procedure were used to verify whether species composition differed before, during and after the disturbance. 2. In contrast to our expectations, the null models showed that the macrophyte assemblages were spatially structured during the drawdown (2000), although species composition was significantly different from the previous year (1999) and also changed in the following years (2001–07). Significant species co‐occurrence patterns were generated by the drawdown disturbance, with species extinctions and colonisation by new species from propagules and seed bank germination. 3. The randomness we expected in 2000 actually occurred in 2001, probably because the reestablishment of normal water level enabled both submersed and free‐floating species to recolonise the shore that emergent species had inhabited since the drawdown. Biotic interactions appeared to increase during the years after the disturbance and the habitat preferences of the aquatic macrophytes were re‐established, resulting in higher similarities in aquatic macrophyte species composition in the years after the drawdown.

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“…Desiccated macrophyte beds are also capable of recovering after rewetting, mainly by the germination from roots or seeds, or by the growth of shoot fragments in the water column (Thomaz et al ). These regrown submerged macrophytes can utilize nutrients from both the water column and sediments (Carignan ; Chambers et al ; Madsen and Cedergreen ), thus might alleviate the water deterioration from macrophyte decomposition.…”

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confidence: 99%

Effects of water level fluctuations on nitrogen dynamics in littoral macrophytes

Lü

Bunn

Burford

2017

Limnology & Oceanography

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Sustained water level drawdown followed by rewetting has the potential to shift macrophytes from a nutrient sink to a source, but the fate of macrophyte-derived nutrients after rewetting is not well understood. We investigated the fate of released nitrogen (N) from isotopically labeled macrophyte litter over a 4-week period after rewetting. We used three treatments: (1) different species in the litter (invasive Cabomba caroliniana vs. native Hydrilla verticillata); (2) sediment desiccation history ("dried then rewetted" vs. "constantly wet"); (3) living macrophytes (presence vs. absence). Our results showed that the Cabomba litter treatment had a significantly higher percentage of macrophyte-derived 15 N in the dissolved fraction of the water column and assimilated by phytoplankton (higher chlorophyll a concentrations), compared to the Hydrilla litter. The treatments with sediment desiccation also had a significantly higher percentage of 15 N in the dissolved fraction and used by phytoplankton after rewetting, but less in the sediment, compared to the constantly wet treatment. The presence of living macrophytes partially reduced the 15 N increase in the water column and/or sediment, but the scale of the effect was species-and biomass-dependent. Our study showed that sediment pre-desiccation changed the fate of macrophyte-derived 15 N after rewetting, increasing the impact on water quality. This was further exacerbated by the presence of litter from an invasive species. This study highlights the need to manage water levels to maintain healthy macrophyte beds and thereby addressing water quality issues in lakes and reservoirs.

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Effect of reservoir drawdown on biomass of three species of aquatic macrophytes in a large sub-tropical reservoir (Itaipu, Brazil)

Cited by 20 publications

References 10 publications

Effect of Spatial Heterogeneity on Zooplankton Diversity: A Multi-Scale Habitat Approximation in a Floodplain Lake

Effect of Spatial Heterogeneity on Zooplankton Diversity: A Multi-Scale Habitat Approximation in a Floodplain Lake

The immediate and long‐term effects of water drawdown on macrophyte assemblages in a large subtropical reservoir

Effects of water level fluctuations on nitrogen dynamics in littoral macrophytes

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