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1.
Physical and biological development of a newly breached managed realignment site, Humber estuary, UK 总被引：1，自引：0，他引：1
As part of the Humber flood defence upgrade works (Urgent works) undertaken by the Environment Agency, the Paull Holme Strays site was identified as one of twelve potential managed realignment sites within the Humber catchment. The site was breached in September 2003, creating 80 hectares of new intertidal habitat. Initial accretion monitoring commenced in December 2003 with annual surveys of invertebrate colonisation commencing in October 2004. The present study gives details of the physical development of the newly created mudflat within the site, together with invertebrate colonisation and benthic community change over time. Comparisons between the newly created habitat and the existing mudflat outside the old sea wall are made. The macrofaunal communities found within the area as a whole are considered to be characteristic of the area with low species diversity, high abundance and small body size. The community within the managed realignment site is still in an early successional stage with low abundance and diversity in comparison with other sites within this part of the Humber. However the community biomass increased considerably between 2004 and 2005. Colonisation within the managed realignment site is still primarily concentrated in the areas around the two breach sites and is thought to be restricted in other areas due to infrequent tidal inundation. 相似文献
2.
The managed realignment of coastal defences and subsequent creation of intertidal habitats is one of several 'soft' engineering options that could reduce the costs of maintaining embankments and at the same time deliver environmental benefits. The managed realignment at Tollesbury was one of the first in the UK, undertaken as an experimental test case to improve understanding of the practical techniques and processes involved. Independent studies were undertaken on the development of soils, benthic invertebrates and vegetation within the site in addition to methods of enhancing the process of natural colonisation of saltmarsh plants. Bathymetric and vegetation monitoring were undertaken on the adjacent estuary to determine any breach effect that may be attributed to the realignment. This paper summarises the results from the vegetation, sedimentation and invertebrate monitoring and discusses the implications for other managed realignment schemes in the UK. 相似文献
3.
The Humber Estuary Shoreline Management Plan provides a long-term strategy for investment in sustainable defences to reduce the risk to people and property from flooding in part of Eastern England. In addition to the estuary's economic importance with its ports, industry and the third of a million people living on its floodplain, the Humber is of outstanding value for wildlife and its historic environment. The plan has to meet the needs of these activities and take account of rising sea level. It is based on extensive technical studies and modelling. The realignment of some embankments is being examined so that the creation of intertidal habitat will offset losses from coastal squeeze, increase the stability for some lengths of embankment and reduce extreme high flood levels in the tidal rivers. The 80 ha Paull Holme Strays managed realignment wetland was completed in the summer of 2003 and work is in progress on another at Alkborough. Other such realignment will be developed as part of the implementation of the long term strategy. 相似文献
4.
Annual topographic surveys were carried out at the Saltend mudflat (Humber estuary, UK) between 1998 and 2006. These surveys formed part of an ongoing monitoring programme to examine the potential effects on the mudflat topography of the construction and operation of a waste water treatment works (WwTW) development by Yorkshire Water. Of particular concern was the potential disruption to the sedimentological regime within the special protection area (SPA) and candidate special area of conservation (cSAC) which could affect the invertebrate communities and ornithological functioning of the site. In addition to the development of the WwTW located to the extreme north-west of the site, a port extension removing 10ha of the Saltend intertidal mudflat (outside the SPA but immediately south east of the WwTW) also occurred between 1999 and 2006. Minimal change was noted across the site following the construction and operation of the WwTW between 1998 and 2000. However, the construction of the bund in closer proximity to the SPA and cSAC masked any potential impact the WwTW could have had across the site after 2000. Profiles and contour mapping indicate that significant mudflat accretion occurred in the immediate area of the bund, with a general increase recorded across the western section of the site since 2000. In contrast the alternations to channel planform and subsequent rapid accretion of the mudflat to the east of the jetty, being a significant distance from the developments, are attributed to natural cyclical changes. 相似文献
5.
Annual topographic surveys were carried out at the Saltend mudflat (Humber estuary, UK) between 1998 and 2006. These surveys formed part of an ongoing monitoring programme to examine the potential effects on the mudflat topography of the construction and operation of a waste water treatment works (WwTW) development by Yorkshire Water. Of particular concern was the potential disruption to the sedimentological regime within the special protection area (SPA) and candidate special area of conservation (cSAC) which could affect the invertebrate communities and ornithological functioning of the site. In addition to the development of the WwTW located to the extreme north-west of the site, a port extension removing 10 ha of the Saltend intertidal mudflat (outside the SPA but immediately south east of the WwTW) also occurred between 1999 and 2006. Minimal change was noted across the site following the construction and operation of the WwTW between 1998 and 2000. However, the construction of the bund in closer proximity to the SPA and cSAC masked any potential impact the WwTW could have had across the site after 2000. Profiles and contour mapping indicate that significant mudflat accretion occurred in the immediate area of the bund, with a general increase recorded across the western section of the site since 2000. In contrast the alternations to channel planform and subsequent rapid accretion of the mudflat to the east of the jetty, being a significant distance from the developments, are attributed to natural cyclical changes. 相似文献
6.
Blooms of macroalgal matting are increasingly common within temperate zones and are often comprised of opportunistic species such as Ulva lactuca. Where this algae forms a dense mat, a stressful environment is created in the sediment below, influencing the invertebrate infaunal assemblage. This study was conducted over a six month period during which a dense mat of U. lactuca developed and subsequently dispersed. The algal mat was found to have a significant negative impact on species richness, abundance and biomass of the macroinfauna. However, a faunal community developed within the algal mat which contained several species not previously observed. This community increased the abundance and diversity of the overall invertebrate assemblage. The results are discussed in relation to impacts on the ecosystem as a whole. 相似文献
7.
《Limnologica》2014
As a step towards the biological assessment of wetlands in South Africa, this study investigates the influence of biotope characteristics on the spatial distribution of aquatic invertebrates. The aim was to assess whether different wetland biotopes support significantly different invertebrate assemblages in terms of the composition and abundance of microcrustaceans and macroinvertebrate taxa. During October 2006, three different biotopes were sampled within Verlorenvlei and Wave's Edge wetlands (Western Cape, South Africa) using a long-handled sweep net. Composition and abundance of invertebrate assemblages were compared between and within sites for each of the wetlands. Assemblage composition generally differed among biotopes within each wetland, as revealed by cluster analysis and MDS plots. At Verlorenvlei, biotopes formed distinctive clusters with low site-specific variability. Assemblage composition at Wave's Edge revealed coarser groupings with clusters distinguishing between vegetated and non-vegetated biotopes only. Biotopes within each wetland differed significantly in terms of taxon richness, Shannon diversity and mean total invertebrate biomass (g m−3), whilst mean total density (ind m−3) differed only between biotopes in Verlorenvlei. Considerable shifts in invertebrate assemblage structure corresponded to differences in electrical conductivity among sites at Verlorenvlei. For large physico-chemically heterogeneous wetlands such as Verlorenvlei, it is suggested that smaller physico-chemically homogenous zones should be identified a priori and within these areas vegetated biotopes should be sampled over the broadest possible spatial scale, whilst open-water biotopes can be sampled more narrowly. For small, reasonably homogenous wetlands such as Wave's Edge, we suggest a less broad spatial representation of biotopes and instead one should concentrate on increasing the number of sample repetitions per site. 相似文献
8.
Benthic community responses to thin-layer disposal of dredged material were assessed at three sites in Mississippi Sound, USA. Community composition differed between disposal and reference sites (ANOSIM) for each disposal event. Oweniid sand worms, Amphinomid fire worms, and brittle stars (Ophiuriodea) contributed the most to community distinctions between disposal and reference sites (SIMPER), with higher abundances at the disposal sites. Total infaunal abundance was similar to pre-disposal and reference conditions within 3-10 months of thin-layer disposal. Distinctions in community composition between disposal and reference sites (nMDS) persisted throughout the 16-month study period, but were less pronounced at the site where sediment composition was unchanged by disposal. Size distributions of some taxa (e.g., gastropod and hemichordate) suggest adults recolonized the newly deposited sediments either through vertical migration or lateral immigration from adjacent areas. Thin-layer disposal offers a viable alternative to conventional open-water disposal practices and warrants further exploration for other areas with deeper bathymetries and different hydrodynamic regimes. 相似文献
9.
《Limnologica》2015
Abiotic variability is known to structure lotic invertebrate communities, yet its influence on lentic invertebrates is not clear. This study tests the hypothesis that variability of nutrients and macro-ions are structuring invertebrate communities in agricultural drainage ditches. This was determined by investigating invertebrate adaptations to disturbance using insect life-history strategies. Many low-lying agricultural areas contain drainage ditches which potentially provide suitable habitat for aquatic invertebrates. In the province of North Holland (The Netherlands) the extensive network of eutrophic ditches are hydrologically managed, creating seasonal variability of water quality arising from agricultural run-off and the inlet of mineral rich, river derived water. This temporal variability was analysed from monitoring data, collected over a 7 month period (February till August) and covering 84 ditches in three soil regions; sand, clay and peat. Invertebrate diversity was determined as local (α diversity), regional (γ diversity) and species-turnover (β diversity). We ran canonical correspondence analysis and linear mixed models to determine correlations between invertebrate diversity, functional community composition and specific abiotic parameters, including variability (expressed as the Median Absolute Deviation). Invertebrate α diversity was positively correlated to variability in water transparency and negatively correlated to average pH, with the two parameters reflecting a water quality gradient in the environment. Insect life-history strategies expressed adaptations to abiotic variability and harsh (eutrophic) conditions. These adaptations were mainly achieved through good dispersal abilities and developmental trade-offs. The results support measures to reduce influxes of excess nutrients to this network of ditches. 相似文献
10.
《Limnologica》2016
Both the diversity and abundance of water column phytophilous macroinvertebrates (PMI) were related to the fish stocking density, physico-chemical parameters in the water and semi-quantity of littoral aquatic macrophytes (AM). PMI were sampled in ponds with two types of polyculture 0+ or 2+/3+ common carp (Cyprinus carpio). The carp stock was combined with predatory fish pike (Esox lucius) or catfish (Silurus glanis) and herbivorous fish grass carp (Ctenopharyngodon idella) and/or silver carp (Hypophthalmichthys molitrix) in semi-intensively managed fishponds. Both the diversity of PMI community and abundance of most of the PMI trophic groups were negatively correlated with water depth and grass carp stocking density. Moreover diversity of PMI community was higher inside the beds of AM than in edge sites connected with open water. Neither polyculture with low stocking density of common carp 2+/3+ nor polyculture of common carp 0+ in the semi-intensively managed fishponds had a significant influence on the diversity of the PMI community. The abundance of PMI taxonomic groups was influenced by: (1) semi-quantity of reed sweet-grass (Glyceria maxima), (2) concentration of dissolved oxygen, (3) water depth, (4) common carp age 0+ or 2+/3+ and (5) quantity of fertilizer. Most of the PMI families were found in very shallow sites which were protected from fish, although environmental conditions there were more unfavourable, especially low oxygen concentration. The relationship between Glyceria maxima and PMI families seems to be related to its semi-terrestrial habitat (low water depth), growth dynamics and/or presence of aerenchyma. Supplemental food for fish increased the abundances of all of the PMI trophic groups. 相似文献
11.
Cores taken from 16 stations within Eight Day Swamp, a highly contaminated marsh in the Hackensack Meadowlands, were analyzed for metal concentrations and for benthic community structure. Metal levels were compared with the benchmark ERM values, and expressed in terms of toxic units. Mercury was the most important metal in all the samples in terms of its contribution to the total toxic units. The overall abundance and taxa richness in the benthic community were associated with the height of the location relative to the tidal cycle, but were generally not significantly correlated with metal concentrations at the sites. Ordination of the communities showed that the communities that were low-lying (on the mudflat) were most similar to one another, and those that were higher up on the marsh were most similar to one another. However, diversity indices (Shannon-Wiener H' and Simpson's) were significantly associated with concentrations of the metals (except As) and with the sum of the toxic units at a station. 相似文献
12.
A key question in designing any managed retreat site concerns the nature of the habitats which will be created, and their likely long‐term sustainability and development. Studies of historical sea wall failures in Essex have shown that former reclaimed areas may respond to renewed tidal ?ooding in different ways depending on a number of factors, most importantly the elevation of the land at the time of breach, which governs the frequency and duration of tidal ?ooding. This paper demonstrates how digital terrain modelling using airborne lidar data can be used to calculate the elevation of the land behind a breach and to predict the likely habitats which will be created. When combined with data from sites of historical sea wall failure, predictions can also be made about the likely geomorphological and biological evolution of the created habitats in the longer term. At Abbotts Hall on the northern side of Salcott Creek, Essex, where a managed retreat scheme was activated in October 2002, the highest areas above 2·35 m OD were predicted to develop stable saltmarsh, intermediate areas between 2·1 and 2·34 m OD to develop potentially unstable saltmarsh which is likely undergo internal dissection, and the lowest areas below 2·1 m OD to remain as mud?at or lagoon. Approximately 38 per cent of the site was predicted to develop stable saltmarsh, and nearly 50 per cent to remain as lagoon or mud?at. Monitoring is now being undertaken but it will be several years before the accuracy of the predictions can be assessed. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
13.
Little information currently exists on spatial and temporal benthic community variations in tropical coastal lagoons. Here, the benthic community response to habitat variation in the Celestun coastal lagoon, northwest Yucatan peninsula, was seasonally examined during the 1994–1995 climatic cycle into a grid of 12 sampling sites distributed along the salinity gradient of the lagoon. Habitat variation was assessed through physical factors associated both to the water column (e.g. salinity) and the bottom sediment (e.g. sand, silt and clay fractions). The benthic community response was assessed through species diversity measures and abundance. Under the influence of climatic seasonality, variations in habitat conditions followed by changes in the benthic community characteristics were expected. Results from two-way ANOVAs showed that for the period of study, Celestun lagoon was more heterogeneous along the spatial axis of variability than along the temporal one. Multiple regression analysis showed that salinity was spatially the main factor influencing the benthic community characteristics. Temporally, the sediment characteristics were observed to exert significant effects on the species diversity characteristics but not on abundance. Other variables assessed (dissolved oxygen, pH, temperature and water column transparency) exhibited no significant covariance with species diversity and abundance. Since generated from historical data, these results have the potential to be useful as a benchmark to the establishment of monitoring programs in the light of the increasing anthropogenic pressure on the natural resources of the lagoon and surrounding coastal area. 相似文献
14.
In December 1999, 28,000 m3 of sediment was dredged from two sites within the harbour at Coffs Harbour, NSW. Dredging was carried out using a trailing suction hopper-dredge which transported the spoil to a shallow (6 m) site within the adjacent Solitary Islands Marine Park for disposal. Evaluation of the effects of the dredge-spoil dumping at the receiving site was conducted by taking replicated van Veen grab samples at the disposal site and at two control sites, before, immediately after, and three months after dumping. The results indicated that dredge-spoil dumping had no detectable effect on either the structure of the invertebrate community or the physical characteristics of sediment at the receiving site. Although there were some significant faunistic differences between samples from the disposal site and the control sites immediately following dumping, these were related to pre-existing differences between sites rather than to the effects of dredge-spoil disposal. Four principal factors are likely to have contributed to the lack of impact: (i) dredged material had similar sedimentary characteristics to those at the receiving site; (ii) dredged material was free from contaminants; (iii) the disposal method systematically distributed a number of shallow layers of sediment over the disposal site and thus motile macrofauna had the opportunity to migrate upwards between passes of the barge; and (iv) the disposal site was in a high energy environment where the resident biota are likely to be adapted to dynamic sedimentary conditions. The lack of detectable effects suggests that the disposal strategy was one which minimized impacts within an area which has high conservation value and should thus be adopted as a model for future works within the region. 相似文献
15.
Ramond JB Berthe T Lafite R Deloffre J Ouddane B Petit F 《Marine pollution bulletin》2008,56(6):1168-1176
The Seine estuary (France) is one of the world's macrotidal systems that is most contaminated with heavy metals. To study the mercury-resistant bacterial community in such an environment, we have developed a molecular tool, based on competitive PCR, enabling the quantification of Gram-negative merA gene abundance. The occurrence of the Gram-negative merA gene in relation with the topology (erosion/deposit periods) and the mercury contamination of three contrasted mudflats was investigated through a multidisciplinary approach and compared with a non-anthropized site (Authie, France). The higher abundance of the Gram-negative merA gene in the Seine estuary mudflats indicates a relationship between the degree of anthropization and the abundance of the merA gene in the mudflat sediments. In the Seine mudflats, the maxima of abundance are always located in fresh sediment deposits. Therefore, the abundance is closely related with the hydrosedimentary processes, which thus seem to be determining factors in the occurrence of the Gram-negative merA gene in the surface sediments of the Seine's mudflat. 相似文献
16.
A benthic habitat along the coast of McMurdo Station in the Ross Sea, Antarctica is enriched by sewage from the station and altered by hydrocarbons and heavy metals in an adjacent historic dumpsite. We report on 10 years of change in the benthic communities from 1988 to 1998 and compare enrichment effects at Australia's Casey Station, East Antarctica. Despite being 14 km apart, reference communities upcurrent and downcurrent of McMurdo Station remained closely similar over time, dominated in all years by a tube building polychaete, Spiophanes tcherniae. The community bordering McMurdo Station was generally a third as abundant as communities at the reference sites over the decade of sampling, although diversity was as high or higher, except in the most contaminated areas. In 1992, organic enrichment of the outfall community intensified and within the year, the opportunistic polychaetes Aphelochaeta sp., Ophryotrocha notialis, Capitella perarmata, and Leitoscoloplos kerguelensis became dominant. Since 1996, two of the three enriched communities have increased in resemblance to the reference communities. Given the observed responsiveness of the benthos to the outfall so far, further changes are anticipated within the year following implementation of sewage treatment in 2003. Organic enrichment by McMurdo Station has had a greater impact on benthic community structure than at Australia's Casey Station. 相似文献
17.
Benthic meiofauna community composition at polluted and non-polluted sites in New Zealand intertidal environments 总被引：1，自引：0，他引：1
Meiofauna composition was investigated for six field sites, including polluted and non-polluted sites, within two regions (Auckland and Bay of Plenty) during winter (July-August 2004) in the North Island of New Zealand. Physico-chemical parameters were measured during the sampling period and meiofauna distribution and abundance were compared with these measured parameters. Analysis of meiofauna abundance indicated that foraminiferans, nematodes and ostracods were the taxa that contributed to the variability between field sites within the Auckland region. However, no clear taxa dominance was seen in the Bay of Plenty region. Comparison of meiofauna abundance and physico-chemical parameters was done using multivariate analysis (PRIMER). However, no clear relationships between the parameters were observed in any field site in either region. The Shannon-Weiner index of diversity did not show any clear differentiation between polluted and non-polluted field sites. Therefore, from the present study, the taxa or physico-chemical parameters used could not effectively characterise pollution at the investigated field sites. 相似文献
18.
低头坝养鱼对上下游局域栖息地和鱼类群落时空格局的影响 总被引：1，自引：0，他引：1
河流鱼类的群落特征会随栖息地环境的变化而发生变化.为了解鱼类群落对低头坝养鱼的响应程度,2013—2014年共6次调查了乌龙河(长江下游支流)两个可涉水河段样点(上游坝和下游坝)的环境因子、鱼类多样性及其群落结构.共采集到5目10科21属24种鱼类,以鲤形目鲤科最多,占总数的58.3%.通过解析时空动态变化与局域栖息地条件对鱼类群落的影响,发现季节因素对鱼类群落结构无显著影响,而鱼类群落所在空间位置(上游坝,下游坝)对群落结构差异具有较显著影响,其中上游中华鳑鲏(Rhodeus sinensis)、(Hemiculter leucisculus)、棒花鱼(Abbottina rivularis)、大鳍鱊(Acheilognathus macropterus),下游食蚊鱼(Gambusia affinis)的多度决定了这种差异;而3个栖息地变量(溶解氧浓度、电导率和流速)均对鱼类群落特征具有显著性影响.栖息地环境差异对河流上、下游鱼类群落的影响较大,具体体现在下游样点鱼类的捕获重量、捕获数量、密度、多样性明显下降,推测利用低头坝养鱼是造成这些现象的重要原因. 相似文献
19.