沉水植物苦草对上覆水各形态磷浓度的影响

沉水植物是影响湖泊磷营养状态的重要因素。在室内模拟了"水-苦草-沉积物"生态系统,在沉水植物苦草生长过程中分析上覆水中的总磷(TP)、溶解性总磷(TDP)、溶解性有机磷(DOP)、溶解性活性磷(SRP)、颗粒态总磷(PP)的变化,探讨了苦草对上覆水磷赋存形态的影响。结果表明,苦草在生长过程中减缓了沉积物磷的相对释放速率使上覆水中TP、SRP、DOP、PP均呈现不同程度的下降。上覆水TP、SRP、DOP、PP分别下降了37.5%、74.6%、42.0%、19.5%;苦草主要通过吸收上覆水和间隙水中的磷及对环境因子的影响,使得上覆水中各形态磷浓度保持在较低的水平,降低沉积物向水体释放磷的速率。     

Effects of Water Level Fluctuations on Spawning Habitat of an Endangered Species,the Australian Lungfish (Neoceratodus Forsteri)

The Australian lungfish Neoceratodus forsteri is an endangered native fish species currently protected under federal and international agreements. The impoundment of riverine habitats by water storages has substantially decreased the availability of dense beds of macrophyte (e.g. Vallisneria nana) in shallow water, the preferred spawning habitat of Australian lungfish. Storage management, such as storage drawdown and maintaining storages at specific levels, may impede establishment and development of dense macrophyte beds, although the effects of storage operation on macrophytes are poorly understood. Storage bathymetry and modelled stream data were used to examine the impact of water level changes (frequency and magnitude) on V. nana habitat within storages and associated riverine areas. Three storages located within the natural range of the Australian lungfish in the Burnett River (Ben Anderson Barrage, Ned Churchward Weir and Paradise Dam) were found to provide limited potential for V. nana habitat when at the full supply level. Furthermore, water storages within the distribution of Australian lungfish fluctuate by ±1 m more frequently in comparison to associated riverine environments. These frequent water level fluctuations challenge the establishment of dense macrophyte beds required for lungfish spawning. Since aquatic macrophytes and streamflow play an integral role in lungfish spawning, management of water storages should focus on releases to the downstream reaches. These releases should mimic natural flow and water temperature regimes to allow establishment and growth of V. nana beds in synchrony with the timing of Australian lungfish spawning. Riverine reaches downstream of storages have the greatest potential for restoration of macrophyte beds. © 2014 Queensland Government, Department of Natural Resources and Mines. River Research and Applications © 2014 John Wiley & Sons, Ltd.     

不同密度铜锈环棱螺对沉水植物生长和水质的影响EI北大核心CSCD

通过试验研究不同密度铜锈环棱螺(Bellamya aeruginosa)对苦草(Vallisneria natans)和金鱼藻(Ceratophyllum demersum)生长及水质的影响。试验结果表明:铜锈环棱螺的存在显著促进了沉水植物的生长,高密度组苦草和金鱼藻的相对生长率分别是对照组的2.16和1.66倍,高密度组苦草和金鱼藻的相对伸长率分别是对照组的1.18和1.25倍;铜锈环棱螺的存在对水质有一定负面影响,水体电导率随着螺密度的增加而升高,溶解氧浓度随着螺密度的增加而降低,pH值、氧化还原电位和叶绿素浓度随着螺密度的增加没有一致的规律;水体氮的去除率随螺密度的增加呈下降趋势,高密度组苦草和金鱼藻对氮的去除率相对于对照组分别下降了70.0%和64.5%,磷的去除率组间没有显著差异;铜锈环棱螺密度对水体氮浓度变化起主要作用,方差占比为64%,沉水植物不同物种对水体磷浓度变化起主要作用,方差占比为72.54%。     

Effects of water level fluctuations on Vallisneria nana in the Burnett River in Southeast Queensland,Australia

Changes in aquatic macrophyte populations in the Burnett River in southeast Queensland, Australia are described with respect to the effects of water level fluctuations and possible impact on the Queensland lungfish (Neoceratodus forsteri). This protected fish relies on macrophyte beds as spawning and nursery areas. Studies were conducted prior to, during and following construction of a new weir on the river. Comparative results of impounded and non‐impounded sites were conducted to investigate seasonal and inter‐annual changes in macrophytes and the effects of both a rapid rise in water level when the impoundment first filled and a decline, on new plants in shallow water. Macrophyte communities in newly inundated areas were studied to determine the time taken for seedlings to emerge and reach a cover sufficient to represent spawning habitats for the lungfish. Vallisneria nana dominated the macrophyte beds, which were scoured from the river by a large flow event in May 1998, the effects of which persisted for at least 1 year. Most newly emerging seedlings of Vallisneria perished following a small decline of 7 cm in water level. Decrease in plant biomass and death of established plants in highly turbid water resulted within 6–9 weeks following larger water level rises of 4.0–5.5 m in the new impoundment. In the period leading up to the lungfish‐spawning season at least 5 months is required for submerged plants to reach the 90% cover preferred for spawning. Implications of the results for water level management and lungfish populations are discussed. Copyright © 2008 John Wiley & Sons, Ltd.     

Impacts of different weed cutting practices on macrophyte species diversity and composition in a Danish stream

Various effects of stream management on biotic communities have been suggested on the basis of observations and investigations in regularly managed streams throughout Europe, but only very sparse information is available about if and how stream management can be combined with maintaining a natural and diverse stream flora. Our study was carried out to investigate how weed cutting practice and frequency can affect macrophyte communities to provide knowledge for future decisions regarding management in streams. We chose an experimental approach and applied four different weed cutting practices (cutting full width, central channel, diagonal channels and no cutting) and frequencies within one stream reach for four years. We found only very limited changes over the four years in overall macrophyte diversity parameters following different management practices and there were no changes in macrophyte diversity parameters either as a function of the weed cutting frequency or method applied. In contrast we found directional changes in macrophyte composition following frequent cuttings of either the whole stream channel or a less comprehensive cutting of only one central channel for four years. In both cases the macrophyte communities changed towards a more Ranunculus dominated community while Potamogeton natans became less important in the community. This change seemed to reflect a higher tolerance of Ranunculus towards disturbance. On the basis of these results, we recommend that the management frequency in streams is limited and, if several cuttings are needed to prevent bank over‐flow, cutting in several narrow channels is preferable to cutting in one central channel as directional changes in plant communities are avoided. Copyright © 2003 John Wiley & Sons, Ltd.     

自然河道中沉水植物苦草对水流的生理响应

通过野外现场研究苦草生长和生理对水流的响应规律。结果表明:30~40 cm/s的水流速度对苦草的生长形态有影响;与静水区相比,动水区中苦草植株矮小、叶片较窄。在植物生长旺季和生殖生长期间,动水对植物细胞内的蛋白质和可溶性糖含量有促进作用,同时也诱导过氧化氢(H2O2)等活性氧上升,使得超氧化物歧化酶(SOD)、过氧化氢酶(CAT)等抗氧化酶活性相应提高以降低活性氧伤害;30~40 cm/s的流速对苦草生长有一定的影响,但不影响苦草在河道生态修复中的应用。     

Abiotic influences on the biomass of Vallisneria americana Michx. in the Upper Mississippi River

American wildcelery, Vallisneria americana Michx. is an ecologically important component of aquatic communities in the Upper Mississippi River (UMR). We conducted a study in 2002 to determine the association of several abiotic factors on the vegetative growth of Vallisneria in Navigation Pool 8 (Pool 8) of the UMR. We measured turbidity, percent light absorbance, surface water ammonium, surface water nitrate, current velocity, conductivity, pH and water depth throughout one growing season at 56 stratified sites based on where Vallisneria occurred in previous years. Sediment and aboveground biomass samples were collected during peak growth. Sediment was analysed for organic content, particle size, pore water nitrate and pore water ammonium. Vallisneria biomass samples were dried to constant mass. Because some sites were without water for much of the growing season, only data from 52 sites were reported. Biomass was associated with depth, percent light absorbance, turbidity and wind fetch. Vallisneria was abundant in the depth range of 0.55 to 1.03 m, in areas receiving at least 38% of surface light and in areas exposed to greater wind fetch (>2000 m). Our results suggest that the primary abiotic variable associated with Vallisneria americana in the UMR is light, not nutrients. Published in 2007 John Wiley & Sons, Ltd.     

Light availability and growth of wildcelery (Vallisneria americana) in upper Mississippi River backwaters

Large beds of Vallisneria americana declined in the backwaters of the Upper Mississippi River after a drought that occurred between 1987 and 1989. One hypothesis for this decline is that low light availability may have decreased net photosynthesis to the extent that overwintering tubers were not formed. Following the decline, light availability remained low. To determine what light levels would be necessary for the re-establishment of Vallisneria in the Upper Mississippi River, the long-term growth of plants in a backwater lake and in an experimental pond was measured while the surface and subsurface light were monitored continuously. Plants grown from tubers transplanted to 0·5, 1·0 and l·5m depth in the lake grew and produced tubers only at 0·5m depth (9% of surface light). At 1·0 m, light availability was less than 1% of the surface light. Plants grown from tubers in experimental ponds with four shade treatments (2, 5, 9 and 25% of surface light) for the same growing period produced replacement-weight tubers in 9% light. For a longer growing season, plants also produced replacement-weight tubers in treatments with at least 5% of surface light. An average light-extinction coefficient of 4·64 m^?1 was calculated for the backwater lake based on continuous data collected during 94 days during the growing season from eight widely separated sites. Using equations based on the average extinction coefficient for the lake and average leaf lengths of plants grown in experimental ponds, we predict that in years with comparable turbidity, plants grown from locally collected tubers will grow and produce replacement tubers only at depths of 0·8 m or less.