177,543 research outputs found
Interactions between benthic macroinvertebrates and saltmarsh plants : consequences for saltmarsh restoration and the policy of managed realignment on the coast of SE England.
No full textPhDOver the last half century, the saltmarshes of south east England have undergone
an extensive decline, especially the pioneer zone vegetation. These losses have
generally been blamed on coastal squeeze resulting from sea level rising against sea
walls. There is little evidence to support this hypothesis however, and an alternative
hypothesis, based on infaunal invertebrates preventing the establishment of saltmarsh
plants was tested.
In the managed realignment site at Tollesbury, and the other sites examined, the
mudflat fauna was dominated by Nereis (= Hediste) diversicolor and Hydrobia ulvae. In
laboratory experiments N. diversicolor and H. ulvae reduced the production of seedlings
from seeds of Salicornia europaea agg.. Conversely the presence of S. europaea agg.
significantly reduced the normal burrowing activity of N. diversicolor.
Invertebrate exclusion experiments established at five sites in south east
England facilitated colonisation by saltmarsh plants at some sites (Orplands, the Blythe
Estuary, Wallasea Island and Maldon), by excluding large (>3cm) N. diversicolor.
However, at the Tollesbury realignment site, the high rate of sediment deposition and
the relatively long distance to a source of seeds prevented plant colonisation.
This study supports the hypothesis that establishment of saltmarsh vegetation is
prevented by infaunal invertebrates,particularly N.diversicolor, which exclude plants
through bioturbation, herbivory and granivory. These interactions may help explain the
loss of saltmarshes and will reduce the success of future managed realignment schemes
which depend upon the colonisation of new intertidal areas by saltmarsh vegetation.
Further management of realignment sites will be necessary to encourage saltmarsh
development.Ministry of Agriculture, Fisheries and Foo
Saltmarshes on the fringe : restoring the degraded shoreline of the Eden Estuary, Scotland
No full textSaltmarshes are highly valued habitats but the majority of the Eden Estuary’s saltmarsh was buried under sea defences and ad hoc rubbish dumps during the last century. Without saltmarsh, the degraded shoreline may be even more vulnerable to rising sea levels and increased wave and tidal energy. This study investigated planting native saltmarsh species, common in the estuaries of Eastern Scotland, to restore saltmarsh development and sedimentation to the Eden Estuary’s shoreline.
The survival and growth of the sedge Bolboschoenus maritimus (Sea Club-rush) and the grasses Phragmites australis (Common Reed) and Puccinellia maritima (Common Saltmarsh Grass) were compared in planting trials. These were seeded or transplanted onto unvegetated upper mudflats in front of eroded P. maritima saltmarsh and a disused rubbish dump. The longer term sustainability of this practice was assessed by comparing sediment deposition and surface elevation in the transplant sites, natural saltmarsh and upper unvegetated mudflats.
B. maritimus outperformed P. australis and P. maritima. Springtime, high density planting was successful, whereas seeds, planting in autumn and low density planting failed. Growth in the transplanted B. maritimus sites was relatively slow for the first three years but subsequently overtook growth of the seaward edge of natural B. maritimus marsh. Sediment was not deposited on natural P. maritima and was low on upper unvegetated mudflats and in young transplant sites. Most deposition occurred in four year old sites of B. maritimus. Sediment surface elevation in natural P. maritima remained constant throughout the year, but increased in all the other sites during the summer. The upper mudflat was the only site to erode during winter. A significant, positive association was found between tide height and sediment deposition, while winds from the south-east were associated with significantly more deposition than winds from the south-west.
The direct planting of saltmarsh vegetation has restored a valuable and rapidly disappearing habitat to the degraded shoreline of the Eden Estuary. The low-cost and simplicity of this restoration practice give it great potential as a sustainable coastal management option that should be explored in other Scottish estuaries. This form of restoration could help to increase the resilience and reduce the vulnerability of degraded shorelines to climate change and rising sea levels
Mechanisms for accumulation and migration of technetium-99 in saltmarsh sediments
No full textThis thesis describes the development of analytical methods for both the bulk determination of 99Tc, and determination of 99Tc in sequential extracts from sediments. These methods have been used to collect data, which, along with trace and major element data have been used to interpret the mechanisms for 99Tc input, migration and accumulation in saltmarshes. The inventory of 99Tc stored in the Thornflatt Saltmarsh, Esk Estuary has also been determined. The routine determination of 99Tc in bulk samples uses 99mTc as a yield monitor. Samples are ignited stepwise to 550°C and the 99Tc is extracted using 8M nitric acid. Many contaminants are precipitated with Fe(OH)3 and the Tc in the supernant is pre-concentrated and further purified using anion-exchange chromatography. Final separation of Tc from Ru is achieved by extraction of Tc into 5% TnOA in xylene from 2M sulphuric acid. The yield is determined by γ-spectrometric analysis of 99mTc. Determination of 99Tc is made by liquid scintillation counting. Typical recoveries are in the order of 70-95% and the method has a detection limit of 1.7 Bq/kg for a sample size of 10g. Determination of Tc in sequential extracts uses operationally defined procedures to extract: exchangeable Tc, reducible Tc and oxidisable Tc. An initial water wash is used to extract any occluded Tc and a final leach in 8 M nitric acid is used to dissolve any residual Tc. The isolation of 99Tc uses TEVA resin for Extracts 1-4 and the decontamination procedure developed for bulk analysis for Extract 5. 99mTc was used as a yield monitor, and determination of 99Tc is by liquid scintillation counting. Limits of detection were dependent on the amount of 99mTc tracer used but were found to be as low as 2.4 Bq/kg for a sample size of 2g. A study was made of the mechanisms responsible for the accumulation and migration of Tc in estuarine sediments using sediments collected from saltmarshes at Thornflatt, Carlaverock and the Ribble Estuary. 99Tc was present at determinable activities in all the sediment cores taken from these sites. Good correlations between Tc and CaO as well as CO3 concentrations and poor correlation between Tc and radionuclides adsorbed to inorganic detritus infer a direct input of 99Tc to marsh sediments. Determination of 99Tc in biota living on the marsh also showed that this was not a significant pathway for input of Tc to the sediments. Sequential extraction data imply sorption to an organic fraction of the sediment. Stable element and sequential extraction data indicates that Tc is readily oxidised and remobilised before reprecipitation where redox conditions are favourable. Data indicate a reduction potential between those of the MnIV to MnII reaction and the FeIII to FeII reaction is necessary for re-accumulation to occur, as suggested by published thermodynamic data. Data collected from reducing sediments imply that similar mechanisms are responsible for the accumulation of Mn (e.g. reduction by sulphate reducing bacteria) and the accumulation of Tc. The inventory of 99Tc held within the Thornflatt saltmarsh is proportionally less than that of 137Cs or 241Am when compared to discharges from Sellafield. However a higher proportion of 99Tc is transferred from Seliafield and incorporated into saltmarsh sediments than is suggested by previously published standard distribution coefficient data. Saltmarsh sediments are therefore a more important sink of 99Tc than extrapolations made from inventories of other radionuclides would suggest
Water regimes and marsh distribution. In: McComb, A.J., Kobryn, H.T. and Latchford, J.A. (eds) Samphire marshes of the Peel-Harvey estuarine system Western Australia.
No full textTide has long been recognised as the most influential factor determining plant zonation and the development of saltmarsh communities, and it is the tide that largely determines the structure and function of saltmarshes (Clarke & Hannon, 1969).
The zonation of species with increasing distance from the water's edge and increasing elevation is initially determined by the frequency of tidal flooding and the tolerance of various species to this (Huiskes, 1990). Tidal range usually sets the upper and lower limits of the marsh. The lower limits are set by depth and duration of flooding, and the consequent mechanical effect of the waves, sediment availability and rate of erosion. The upper limits are influenced mainly by soil water salinity and nutrient availability, both of which are linked to tidal flooding frequency (Mitsch & Gosselink, 1993), tidal water being the main source of soil salt and the major mechanism for nutrient transport (Clarke & Hannon, 1971)
The ecological significance of saltmarshes to the Peel-Harvey Estuarine system. In: McComb, A.J., Kobryn, H.T. and Latchford, J.A. (eds) Samphire marshes of the Peel-Harvey estuarine system Western Australia.
No full textThe saltmarshes of the Peel-Harvey system are important to the environmental health of the estuary and to this region of the Swan Coastal Plain. Although there have been few scientific investigations specific to this area, a number of world-wide studies on the ecological characteristics of saltmarshes have indicated they are very important to the environmental health of estuaries and coastal ecosystems (Mann, 1982; Kennish, 1990). Unfortunately, there is a paucity of studies on Australian saltmarsh ecosystems (Fairweather, 1990). However, in a local context there is evidence that saltmarshes in the Peel-Harvey system are critical to the overall ecological health of the Estuary (Table 6.1). For example, over 83 bird species have been observed in the saltmarshes of the estuary (Ninox, 1990) (Plate 6.1) and between 18 and 25 of these species are known to be trans-equatorial migrants (Jaensch et al., 1988; Wilkes, 1990). This provides the basis for listing the whole Peel-Harvey Estuarine area as a RAMSAR bird treaty area as well as for the estuary being listed in the JAMBA and CAMBA treaties.
The area is also significant for other ecological reasons which will be briefly outlined, along with the major ecological points suggested in the previous chapters, and compared with data and literature generated from saltmarsh research elsewhere in the world. In this way it is hoped that a better appreciation of the ecological significance of the saltmarshes in the Peel-Harvey Estuary will be reached
Fine-scale spatial genetic structure across a strong environmental gradient in the saltmarsh plant Puccinellia maritima
No full textSaltmarsh forms the transition between maritime and terrestrial environments where biotic and abiotic conditions vary substantially along a gradient in elevation. Theoretical and empirical population genetics studies have focused on the influence of environmental gradients on intra-specific genetic variation. Contrastingly, only a few studies have focused on genetic variation in saltmarsh plants, despite the potentially strong influence of environmental gradients shaping diversity in these species. In the present paper, we assess the genetic structure of the saltmarsh plant Puccinellia maritima collected across an elevation gradient in restored and natural saltmarsh. Both spatial autocorrelograms of genetic variation and spatial analysis of principal components detected genetic structurein the natural saltmarsh organized along the gradient in elevation, yet no such pattern was identified considering distance between individuals without taking elevation into account. In combination with previous phenotypic analyses, our results imply that ecological divergence likely plays a key role in shaping genetic structure within saltmarsh species. Comparison of restored and natural saltmarsh indicated that interspecific competition plays an important role in shaping the genetic structure observed on the natural saltmarsh. The results of this study demonstrate that saltmarshes are valuable models in which to test effects of ecological differentiation and, by extension, provide a better understanding of the functioning of this threatened environment
Avery, Saltmarsh, & Company (to accompany bill H. R. no. 958).
No full textR-P of Avery, Saltmarsh, and Co. 23 Feb. HR 280, 24-2, v2, 9p. [306] Attacked by Creek Indians while transporting the mail in Alabama; Creek war
Australian saltmarsh and sparsely vegetated saltmarsh map version 1.0
No full textThe dataset contains a national map of saltmarsh and sparsely vegetated saltmarsh (also known as saltflats) ecosystems produced via a classification of Landsat 8 images.The map output of this classification and associated map data files are described below:1.JCU_Australia-saltmarsh-extent_v1-0.tiff: Contains a national map of saltmarsh ecosystems produced via a classification of Landsat 8 images. Pixel value is either 0 (Non Saltmarsh) or 1 (Saltmarsh).2.JCU_Australia-saltmarsh-probability_v1-0.tiff: Contains the associated probability map associated with the saltmarsh map. Pixel value represents percentage probability with values ranging from 0 – 100 (%).3.JCU_Australia-saltflat-extent_v1-0.tiff: Contains a national map of saltflats produced via a classification of Landsat 8 images. Pixel value is either 0 (Non Saltflats) or 1 (Saltflats).4.JCU_Australia-saltflat-probability_v1-0.tiff: Contains the associated probability map associated with the saltflat map. Pixel value represents percentage probability with values ranging from 0 – 100 (%).Suggested citation: Navarro, A., Canto, R., M., Lyons, M. & Murray, N.J. (2023) Australian saltmarsh and sparsely vegetated saltmarsh map version 1.0. James Cook University, Townsville. DOI: 10.6084/m9.figshare.24021465</p
Recommendations for the future management and conservation of saltmarshes in the Peel-Harvey estuarine system. In: McComb, A.J., Kobryn, H.T. and Latchford, J.A. (eds) Samphire marshes of the Peel-Harvey estuarine system Western Australia.
No full textEstuarine saltmarshes can stimulate a number of senses. In a visual way, they provide a pleasing vista of procumbent to tall shrubs and trees tinged with colours ranging from red in autumn to succulent green in spring. This view is often enhanced by the sight of hundreds of wading birds feeding and dabbling along the shores and flying low over this interface between land and water. Saltmarshes also provide a contrasting sense when the rich productive smells of the marsh are detected. These smells are composed of decaying sun-baked vegetation mixing with the rotting gases of fetid muddy land. To some, the landscape features and the close proximity of open estuarine waters provides a potentially dollar-rich urban development challenge. With enough fill and re-contouring, these areas could be converted into expensive waterside homes. To all, however, the swarming mosquito hazes can drive us into our homes or cars making us wonder why nature has been so free in creating such a varied environment.
Overall, samphire marshes truly embody a large ecotone metaphor. On one side is a unique habitat providing an interface and link between land and water, and on the other side an environment fertile for human cultural conflict. Unfortunately, humans are an ecotone species and are drawn to the fringes of estuaries. To reduce conflict and successfully manage these environments requires an understanding of current land ownership, reserve status of fringing land, international treaty obligations, the planning process and the use of practical management plans and structures. It is also important to recognise the wisdom of using applied management and theoretical research plans to provide answers to management questions. They are most helpful if these plans recognise the uniqueness of most saltmarshes and give the public and estuarine manager the kind of information which allows saltmarshes to be conserved and sustained well into the future. Ultimately, any management plan must provide direction to help prevent the degradation of saltmarsh functions, such as ecologically important biodiversity, productivity and nutrient storage and release functions
Aspects of the ecology, behaviour and ecosystem effects of the marine polychaete Nereis diversicolor (O.F. Müller, 1776) in the estuaries of south-east England.
No full textPhDThe marine infaunal polychaete Nereis diversicolor has been shown to restrict the development of pioneer saltmarsh vegetation in south-east England through bioturbation and herbivory while surface deposit feeding. This can have severe implications for saltmarsh conservation as in the UK the greatest loss of internationally important saltmarsh habitat occurs in these estuaries. This thesis addresses several aspects of the ecology of N. diversicolor as an ecosystem engineer. The main aims were to investigate how it disperses and colonises sediments, what food sources support its often dense populations and whether these are enhanced by nutrient pollution, and what other effects on the habitat and other benthic fauna they may have. A 12 month experiment on the Crouch Estuary demonstrated that N. diversicolor disperse throughout the year, from the water column as late larvae and juveniles, and as adults crawling across the sediment surface. Peak dispersal is during late summer, but was not necessarily density dependant and individuals may disperse several times. There may be population differences in the stages of dispersal as funnel trap data from the Thames estuary indicate that N. diversicolor also disperse as much younger larvae. Multiple stable isotope (δ 13C and δ 15N) analyses were used approach was employed to test the hypothesis that N. diversicolor feeding behaviour was affected by sewage inputs, which would encourage surface deposit feeding on organic detritus, microphytobenthos and benthic macroalgae, rather than suspension feeding on phytoplankton and water column organic matter. At polluted sites N. diversicolor were mainly surface deposit feeders feeding on Ulva sp. and sediment organic matter, and at putative clean sites suspension feeding was more important. Their diet varied spatially as in some locations Spartina anglica detritus was important while in others Nereis was a secondary consumer, feeding on the amphipod Corophium volutator. A seasonal study using stable isotopes revealed differences in feeding behaviour between the Wallasea Island managed realignment site, and in an adjacent natural saltmarsh. At the realignment site benthic algae were the important food source, whereas in the mature marsh Nereis consumed predominantly Spartina anglica detritus, C. volutator, and was suspension feeding on water column organic matter. Preventing Nereis from surface deposit feeding within the recharged sediments in the Wallasea Island managed realignment site resulted in a reduction in sediment water content, increased sediment stability and development of diatomaceous mats. However, the exclusion did not provide refuge for young Nereis and bivalves, or encourage the successful establishment of pioneer marsh species (S. anglica and S. europaea agg.).Natural Environment Research Studentship
(NER/S/A/2006/14028)
CASE
Centre for the Environment, fisheries, Aquaculture Science (CEFAS
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