Distribution of modern salt-marsh foraminifera in the Albemarle–Pamlico estuarine system of North Carolina, USA: Implications for sea-level research

We described the distributions of foraminifera from ten physiographically distinct salt marshes in the Albemarle–Pamlico estuarine system, North Carolina using 193 surface samples. We defined elevation-dependent ecological zones at individual sites using cluster analysis and detrended correspondence analysis. Additionally, seven principal biozones of salt-marsh foraminifera were identified that have distinctive spatial distributions reflecting a pattern of salinity regimes caused by the current configuration of barrier-island inlets. High salinity sites along the southern Outer Banks are associated with sub-tidal calcareous assemblages, low marshes dominated by Miliammina fusca and high marsh environments defined by Haplophragmoides wilberti, Trochammina inflata and Arenoparrella mexicana. In contrast, lower salinity marshes have Ammobaculites spp. in sub-tidal settings, Miliammina fusca-dominated low marshes and high marsh settings characterized by Jadammina macrescens. Spatial variation of foraminiferal populations and the potential for biozones to migrate in response to changing inlet configuration and salinity, suggests that datasets of modern salt-marsh foraminifera from multiple environments would be appropriate for reconstructing Holocene relative sea level in North Carolina.     

Ammonium Transformation in a Nitrogen-Rich Tidal Freshwater Marsh

The fate and transport of watershed-derived ammonium in a tidal freshwater marsh fringing the nutrient rich Scheldt River, Belgium, was quantified in a whole ecosystem ¹⁵N labeling experiment. In late summer (September) we added ¹⁵N-NH₄⁺ to the flood water entering a 3477 m² tidal freshwater marsh area, and traced the ammonium processing and retention in four subsequent tide cycles. In this paper we present the results for the water-phase components of the marsh system and compare them to a similar experiment conducted in spring/early summer (May). Changes in concentration and isotopic enrichment of NO₃⁻ + NO₂⁻, N₂O, N₂, NH₄⁺ and suspended particulate nitrogen (SPN) were measured in concert with a mass balance study. All analyzed N-pools were labeled, and 49% of the added ¹⁵NH₄⁺ was retained or transformed. The most important pool for ¹⁵N was nitrate, accounting for 17% of ¹⁵N-transformation. N₂, N₂O and SPN accounted for 2.4, 0.02 and 1.4%, respectively. The temporal and spatial patterns of ¹⁵N transformation in the water phase component of the system were remarkably similar to those observed in May, indicating good reproducibility of the whole ecosystem labeling approach, but the absolute ammonium transformation rate was 3 times higher in May. While the marsh surface area was crucial for nitrification in May this was less pronounced in September. Denitrification, on the other hand, appeared more important in September compared to May.     

Inhibitory effects of 2-bromoethanesulfonate and protection by addition of coenzyme M in hydrogen-oxidizing marine enrichment cultures

Abstract Since bromoethanesulfonate (BES) is an inhibitor of methane production (competitive with methyl-coenzyme M), cells able to accumulate large internal pools of methyl-coenzyme M via uptake of its precursor, HS-CoM, should be protected from BES by addition of HS-CoM to the growth medium. Hydrogen-oxidizing marine methanogen enrichments were prepared from anaerobic sediment samples collected at Sippewisset Salt Marsh and Oyster Bay Inlet near Woods Hole, MA. The three enrichments studied were a mixture of cell types with at least 50% of the culture comprised of methanogens. Methane production was found to be sensitive to BES with half maximal inhibition occurring at 5–20 μM BES depending on the enrichment. For each, half maximal protection against 40 μM BES occurred at a HS-CoM: BES molar ratio of 20: 1 to 40: 1. Since the protected enrichments exhibited normal sensitivity toward BES after removal of HS-CoM, it was concluded that methane production in the presence of both BES and HS-CoM resulted from true protection and not growth of BES-resistant mutants. These results suggest that uptake of HS-CoM may be a general property of methanogens occupying anaerobic marine sediments. It is possible that uptake of this coenzyme is an important nutritional feature of methanogens in their natural habitat.     

The effect of cattle and sheep grazing on salt-marsh vegetation at Skallingen,Denmark

The aggregated effect of cattle and sheep grazing on Puccinellion maritimae and other salt-marsh vegetation has been studied together with changes in species composition, the percentage cover of each species, total cover and the percentage of bare ground, six years after grazing had been prevented by construction of experimental exclosures. The results of these experiments are discussed in relation to the natural development of the vegetation that occurred in a permanent plot in the ungrazed part of the salt marsh. Six years without grazing caused a marked increase in total cover and a dramatic reduction in the amount of bare ground. The species composition of the Puccinellia maritima community did not change during these six years, but all species increased in cover. Whereas Artemisia maritima migrated into the Festuca rubra community and only two species Festuca and Halimione portulacoides, increased in cover, all other species showed reduced cover and Salicornia europaea disappeared from the plot after six years without grazing. During the same period of time, three species, Salicornia europaea, Suaeda maritima, and Glaux maritima, disappeared from the plot in the ungrazed marsh as a result of natural development. During thirty-five years the vegetation originally dominated by Puccinellia maritima and Salicornia europaea has changed into a community dominated by Halimione portulacoides, whereas the grazed salt marsh is still dominated by Puccinellia maritima and Salicornia europaea. These results are discussed in relation to the literature on the effect of cattle and sheep grazing on salt-marsh vegetation.     

Differential response of salt-marsh species to variation of iron and manganese

Salt-marsh plants of the lower, middle and upper marsh were compared in their response to iron and manganese. The species studied showed differential sensitivity to high concentrations of Fe (1 000 μM) and Mn (10 000 μM) in hydroculture experiments, species of the lower marsh being more resistant than species of the upper marsh. Fe and Mn concentrations in the root were higher than in the shoot, which was also found in plants inundated with seawater. High Fe and Mn concentrations in the root are probably the result of the oxidizing power of plant roots with a subsequent low translocation of Fe (II) and Mn (II) to the shoot. At high (toxic) Fe and Mn levels in the nutrient solution, Fe and Mn concentrations were much higher in the shoots of sensitive species than in resistant species. The P content of roots and shoots was not influenced by increased Fe and Mn concentrations. Fe and Mn resistance in Spartina anglica and Juncus gerardii, may be in part due to a high root porosity. Other species, however, that are similarly resistant to Fe and Mn lack a well-developed aerenchym. Root porosity, radial oxygen loss and Fe (II) and Mn (II) exclusion by oxidation to Fe (III) (hydr)oxides deposited on the roots form part of the resistance mechanism of hygrohalophytes to Fe and Mn; the differences in this respect between the species may also be due to other metabolic aspects.     

Lake circulation and sediment transport in Lake Myvatn

Lake circulation and sediment transport in Lake Myvatn have been calculated using AQUASEA, a numerical model developed by Vatnaskil Consulting Engineers. The goal of the modelling was to calculate changes in sediment transport within the lake due to changes in lake bathymetry caused by diatomite mining. The model uses the Galerkin finite element method and consists of a hydrodynamic flow model and a transport-dispersion model. The flow model is based on the shallow water equations and the wave equation. The transport model is based on the conservation of mass for suspended sediment. The model was calibrated against measurements performed during the summer of 1992. These included measurements of water elevation, current velocity, wave height, and concentration of suspended sediment. After calibration, the model was run for different mining scenarios to determine their impact on the sediment transport in the lake.     

Effect of nutrient loading on biogeochemical and microbial processes in a New England salt marsh

Coastal marshes represent an important transitional zone between uplands and estuaries. One important function of marshes is to assimilate nutrient inputs from uplands, thus providing a buffer for anthropogenic nutrient loads. We examined the effects of nitrogen (N) and phosphorus (P) fertilization on biogeochemical and microbial processes during the summer growing season in a Spartina patens (Aiton (Muhl.)) marsh in the Narragansett Bay National Estuarine Research Reserve on Prudence Island (RI). Quadruplicate 1 m² plots were fertilized with N and P additions, N-only, P-only, or no additions. N-only addition significantly stimulated bacterial production and increased pore water NH₄⁺ and NO₃⁻ concentrations. Denitrification rates ranged from 0 to 8 mmol m⁻² day⁻¹. Fertilization had no apparent effect on soil oxygen consumption or denitrification measured in the summer in intact cores due to high core-to-core variation. P fertilization led to increased pore water dissolved inorganic phosphorus (DIP) concentrations and increased DIP release from soils. In contrast the control and N-only treatments had significant DIP uptake across the soil-water interface. The results suggest that in the summer fertilization has no apparent effect on denitrification rates, stimulates bacterial productivity, enhances pore water nutrient concentrations and alters some nutrient fluxes across the marsh surface.     

Diet choice in an omnivorous salt-marsh crab: different food types, body size, and habitat complexity

Studies of diet choice by omnivores have the potential to form conceptual links between studies of diet choice by herbivores, frugivores, detritivores, and predators. We examined diet choice in the omnivorous salt marsh crab Armases cinereum (=Sesarma cinereum (Grapsidae)) in a series of laboratory experiments. Armases is sexually dimorphic, with larger males having relatively larger claws than females. In a growth experiment, an invertebrate diet supported better growth than any other single diet; however, growth also occurred on single diets of mud, leaf litter or fresh leaves. Mixed diets provided the best growth. If alternative foods were available, consumption of leaf litter and fresh leaves decreased, but these items were not dropped from the diet completely. In contrast, consumption of invertebrate prey was not affected by the availability of alternative foods. In a predation experiment, crustacean prey (an amphipod and an isopod) were more vulnerable to predation by Armases than were two small gastropod species. Only large male Armases were able to consume large numbers of gastropods. Environmental structure (plant litter or litter mimics) reduced predation rates, especially on crustaceans, which actively utilized the structure to hide from predators. Armases consumes a mixed diet because several factors (prey physical defenses, avoidance behavior of prey, growth benefits of a mixed diet) favor omnivory over a specialized diet. Similar factors may promote minor amounts of “omnivory” by species generally considered to be herbivores, frugivores, detritivores, and predators.     

Retention of suspended sediment and phosphorus on a freshwater delta, South Lake Tahoe, California

The Upper Truckee River and Trout Creek, two major tributaries inflowing to Lake Tahoe, join to form what was historically the largest wetland in the Sierra Nevada mountain range that separates California and Nevada (USA). In the 1950s the delta floodplain of the Upper Truckee River was greatly reduced in area (38%) by urban development and the diversion of the river into a single excavated channel. Conversely, Trout Creek still flows through a wide marsh system with significant overbank flooding before entering Lake Tahoe. This study hypothesized that river channel reaches that are not incised within the delta floodplain retain more sediment and nutrients as a result of greater floodplain connectivity, compared to more incised and excavated reaches. Suspended sediment (SS) and total phosphorus (TP) load data from the delta formed by the Upper Truckee River and Trout Creek were collected using flow stage sensors, turbidometers and depth-integrated samples. During the spring snowmelt flow events monitored in 2003, SS load was reduced by 13–41% for the Upper Truckee River and by 68–90% for Trout Creek. Similar reductions in TP load were observed: 13–32% for the Upper Truckee River and 61–84% for Trout Creek. Monitoring of Trout Creek indicated a reduction in load per unit volume of 20–34% in a moderately incised reach versus a reduction of 51–77% in a non-incised marsh reach containing lagoons, braided channels and backwater areas created by a beaver dam. Smaller particle sizes, <10 μm, were retained in the lower marsh reach with similar efficiencies as larger particle sizes. If retention rates from the Trout Creek portion of the marsh are applied to the Upper Truckee River, sediment loading to Lake Tahoe for 2003 would have been reduced by 917 tons of SS.     

A new species of Ramazzottius (Tardigrada, Hypsibiidae) in a rain gutter sediment from England

Five species of tardigrades were extracted from a sample of sediment from a rain gutter. Four of these, the heterotardigrade Echiniscus testudo and the eutardigrades Milnesium tardigradum, Ramazzottius oberhaeuseri , and probably Macrobiotus cf. sandrae are typical of xerophilous habitats. The fifth species, Ramazzottius varieornatus sp. nov. , is new to science, and it can be readily distinguished from the others of the same genus by egg shell morphology, placoids and the type of cuticle.     

Monitoring the fluvial palynomorph load in a lowland temperate catchment and its relationship to suspended sediment and discharge

Despite it being a component of the seston we know very little about fluvial (waterborne) pollen and spore (palynomorph) transport. This paper presents the results of a monitoring programme conducted over two years and at a catchment scale in South West England. A hierarchical monitoring network was established with flood peak samples taken at 9 sub-catchments, intra-hydrograph samples taken in two sub-catchments and time-integrated sampling undertaken at one location. In addition sampling was undertaken of probable palynomorph sources such as channel bed and bank sediments, and the airborne pollen flux was monitored using modified Tauber traps. The results support previous research in illustrating how the vast majority of fluvial pollen and spores are transported during floods (91%) and that the main control on waterborne palynomorph assemblages is the catchment vegetation and its spatial distribution but with a long-distance (extra-catchment) component. However, strong seasonal effects are also shown, and the importance of distinctive sources such as the riparian input, bed re-suspension and overland flow into drains and tributaries is revealed. Fine sediment in river pools appears to act as a selective store of damaged cereal type pollen grains derived from arable fields. Although pollen does form part of composite particles the data presented here suggest that the majority of the pollen is transported as single grains. Fluvial palynomorph loading is strongly dependant upon discharge and so concentrations in laminated or varved sediments could be regarded as a proxy for flood magnitude. Handling editor: J. Saros     

Temporal changes in the fish fauna entering a tidal swamp system in tropical Australia

Synopsis Leanyer Swamp, a tidal swamp in tropical Australia, is a nursery area for a number of fish species of marine origin. Juveniles of 38 species, representing 24 families, were trapped between October 1979 and March 1980 as they entered the swamp on flood spring tides. The composition of the fish fauna varied markedly between the late dry, early wet and late wet seasons. Of the 17 species whose numbers were significantly correlated to environmental parameters, 15 were correlated wholly or in part with season. The season, the sequence of flood spring tides and the height of these tides determined the movement of the fish community as a whole. The seasonal abundance of many fish species was determined more by their breeding patterns and the dispersal abilities of their juveniles than by such environmental parameters as temperature and salinity which, despite their seasonal change, varied over the short-term with the interaction of tides and rainfall.     

Methodology for studying exchanges between salt marshes and coastal marine waters

The salt marshes of the Mont St. Michel bay represent a complex system in continuous change, mostly due to the frequent exchanges with the coastal waters through tidal processes. In such ecosystems, water is an important element insofar as it represents the common vector of flows between and among several ecosystem compartments. The purpose of the approach discussed here is to estimate the volume of water coming in and out and to determine the variations of the water quality according to time and nutrients concentrations. The estimation of the water fluxes is dependent on the channel calibration downstream of the watershed. Among the different methods examined, the continuous integrals calibration appears as the best one because the water level changes very quickly.Up to now, estimations of nutrients exchanges in wetlands have been based on rigorously regular field sampling, in consideration of the fact that exchanges occurred mainly during annual spring tides or during spring tides of each cycle of the year. According to our results, it seems that every tide, and portion of a tide, of a monthly and seasonal cycle has some importance and variability, which suggests that all parts of a tide should be considered in estimations of exchanges between wetlands and coastal waters.Corresponding Editor: W. Mitsch     

Ecological engineering, design, and construction considerations for marsh restorations in Delaware Bay, USA

Public Service Electric & Gas of New Jersey is restoring approximately 4050 ha of salt marsh along Delaware Bay, USA, to offset possible effects on fish populations in the Bay from their existing once-through cooling system. Planning for this effort started with addressing three questions: Do marshes contribute significantly to fish production? How much marsh produces how much fish? Which marshes should be restored? There is ample evidence that salt marshes produce fish. The area of marsh necessary to offset potential losses was calculated from a simple aggregated food chain model and multiplied by four to provide a comfort level to the regulatory agencies. Marshes chosen for restoration were former salt marshes at appropriate tidal elevations. Planning involved experts in marsh ecology, hydrology, and engineering working with the company and regulatory agencies to establish clearly defined goals for the project. Design followed the advice of the experts and construction was overseen to follow the design. Long-term follow up is through adaptive management that is scheduled to continue for about a decade, depending upon progress of the restoration toward its goals.     

Pollen as a chronometer and sediment tracer,Burrinjuck Reservoir,Australia

Pollen analysis is widely used to reconstruct vegetation and land use histories, but can also provide sedimentological information. At Burrinjuck Reservoir, in south-eastern Australia, annual grass pollen peaks are used to distinguish each year's sediment, even when there are no visible laminations. In conjunction with other dating methods, this allows the determination of year by year influxes of all sediment components. Pollen grains in the Burrinjuck sediments are shown to be predominantly waterborne so that they can be used to trace sediment to its source in particular vegetation stands. Pollen concentration and the proportion of damaged pollen might also distinguish sediment eroded from topsoils and that from subsoils. Pollen analysis can thus be used to locate specific erosion events in both time and space.     

Numerical modelling of suspended sediment transport in tidal estuaries: A comparison between the Tagus (Portugal) and the Scheldt (Belgium-the Netherlands)

A numerical model to simulate the transport of suspended sediment in tidal estuaries is presented. The model is applied to the two large European estuaries the Tagus (Portugal) and the Scheldt (Belgium-The Netherlands). Calculated suspended sediment concentrations compare favourably with observations in the Tagus (r=0.84) and in the Scheldt (r=0.73). The parametrization scheme indicates that the bottom content of fine sediment is correlated with depth in the Tagus; but a different relationship is used in the Scheldt. Because of tidal range differences, average suspended sediment concentrations are lower in the Tagus (80 mg l⁻¹) than in the Scheldt (130 mg l⁻¹), but a larger relative variation between spring and neap tide concentrations may occur in the Tagus.     

A dynamic model for flow and wind driven sediment resuspension in a shallow basin

A model is presented, which describes the daily variations in suspended particulate inorganic matter (SPIM) in a large (61 km²), shallow (mean depth 3.4 m) wind-exposed lake basin at the western end of Lake Mälaren, Sweden. Field studies have shown that wind speed and river inflow are the two major factors leading to changes in SPIM. Wind speed and beam attenuation were measured at high (10 min) frequency, while river inflow were monitored at daily frequency to develop the model. From these field measurements, model-coefficients were determined for the SPIM transport, settling and resuspension. Large-scale variations in SPIM lasting many weeks could be explained by events of high river inflow with a correspondingly high particle load. The threshold for river transported SPIM to have effect on lake concentration was 150 m³ s^–1, while wind induced resuspended SPIM was related to the square root of wind speed.     

Sediment nutrient accumulation and nutrient availability in two tidal freshwater marshes along the Mattaponi River, Virginia, USA

Sediment deposition is the main mechanism of nutrient delivery to tidal freshwater marshes (TFMs). We quantified sediment nutrient accumulation in TFMs upstream and downstream of a proposed water withdrawal project on the Mattaponi River, Virginia. Our goal was to assess nutrient availability by comparing relative rates of carbon (C), nitrogen (N), and phosphorus (P) accumulated in sediments with the C, N, and P stoichiometries of surface soils and above ground plant tissues. Surface soil nutrient contents (0.60–0.92% N and 0.09–0.13% P) were low but within reported ranges for TFMs in the eastern US. In both marshes, soil nutrient pools and C, N, and P stoichiometries were closely associated with sedimentation patterns. Differences between marshes were more striking than spatial variations within marshes: both C, N, and P accumulation during summer, and annual P accumulation rates (0.16 and 0.04 g P m^–2 year^–1, respectively) in sediments were significantly higher at the downstream than at the upstream marsh. Nitrogen:P ratios <14 in above ground biomass, surface soils, and sediments suggest that N limits primary production in these marshes, but experimental additions of N and/or P did not significantly increase above ground productivity in either marsh. Lower soil N:P ratios are consistent with higher rates of sediment P accumulation at the downstream site, perhaps due to its greater proximity to the estuarine turbidity maximum.