Salt Marsh Ponds Research Articles

Bioturbation has a limited effect on phosphorus burial in salt marsh sediments

Abstract. It has been hypothesized that the evolution of animals during the Ediacaran–Cambrian transition stimulated the burial of phosphorus in marine sediments. This assumption is centrally based on data compilations from marine sediments deposited under oxic and anoxic bottom waters. Since anoxia excludes the presence of infauna and sediment reworking, the observed differences in P burial are assumed to be driven by the presence of bioturbators. This reasoning however ignores the potentially confounding impact of bottom-water oxygenation on phosphorus burial. Here, our goal is to test the idea that bioturbation increases the burial of organic and inorganic phosphorus (Porg and Pinorg, respectively) while accounting for bottom-water oxygenation. We present solid-phase phosphorus speciation data from salt marsh ponds with and without bioturbation (Blakeney salt marsh, Norfolk, UK). In both cases, the pond sediments are exposed to oxygenated bottom waters, and so the only difference is the presence or absence of bioturbating macrofauna. Our data reveal that the rate of Porg and Pinorg burial are indistinguishable between bioturbated and non-bioturbated sediments. A large terrestrial fraction of organic matter and higher sedimentation velocity than generally found in marine sediments (0.3 ± 0.1 cm yr−1) may partially impact these results. However, the absence of a clear effect of bioturbation on total P burial puts into question the presumed importance of bioturbation for phosphorus burial.

Oxygen and Triple Oxygen Isotope Measurements Provide Different Insights into Gross Oxygen Production in a Shallow Salt Marsh Pond

The metabolism of estuarine environments is often estimated by measuring changes in dissolved oxygen concentrations. A central assumption of common oxygen-based approaches is that oxygen consumption rates (primarily respiration) are similar under light and dark conditions. Evaluating this assumption is critical, especially in benthic-dominated systems, because differences between daytime and nighttime respiration could result in underestimation or overestimation of ecosystem productivity. We evaluated rates of gross oxygen production over hourly to seasonal time scales in a shallow, temperate salt marsh pond. To assess whether a dissolved oxygen diel mass balance underestimated gross oxygen productivity, we compared rates using this traditional approach and using the triple oxygen isotope tracer of photosynthesis. This is a powerful combination because the triple oxygen isotope approach is theoretically insensitive to respiration. The methods agreed well over daily to seasonal time scales. However, during midday periods of peak light and productivity, the triple oxygen isotope approach resulted in higher hourly scale gross oxygen production rates. The timing and magnitude of this short-term difference is consistent with light-dependent oxygen uptake fluxes including photoreduction and/or light-stimulated community respiration. Finally, aquatic vegetation was associated with variability in productivity across the pond. Such small-scale environmental heterogeneity is evidence that this shallow pond was not laterally well mixed, and likely contributes to the dynamism of these common estuarine environments.

Molybdenum geochemistry in salt marsh pond sediments

The concentration and isotopic composition of sedimentary molybdenum (Mo) has been used to distinguish different redox environments in modern marine settings and in the geological record. We report Mo concentrations and δ98Mo from porewaters and sediments in three anoxic East Anglian salt marsh pond environments: (1) ‘iron-rich’ sediments containing high concentrations of dissolved ferrous iron (up to 2 mM), (2) ‘sulfide-rich’ sediments containing very high concentrations of aqueous sulfide (up to 10 mM) and, (3) sediments that we consider to be intermediate between ‘iron-rich’ and ‘sulfide-rich’ conditions. In iron-rich sediments, we suggest that iron speciation and mineralogy controls the concentration and isotopic composition of Mo. Despite similar aqueous sulfide profiles, the intermediate and sulfide-rich pond sediment have different porewater Mo concentrations and δ98Mo. In the sulfide-rich pond sediment, we suggest that the concentration and isotopic composition of Mo is controlled by solubility equilibrium with an Fe-Mo-S mineral species (e.g. FeMoS4) due to similarities in sediment and porewater δ98Mo throughout the sediment column. In the intermediate pond sediment, we conclude that active breakdown of iron oxides redistributes porewater Mo, observable as a peak of dissolved Mo (>100 ppb), which diffuses within the sedimentary porewaters. The sedimentary δ98Mo is higher in sulfide-rich and intermediate pond sediment (mean = 1.66‰, range = 0.98–1.92‰) than in iron-rich pond sediment (mean = 1.10‰, range = 0.28–1.65‰) with all ponds having sedimentary δ98Mo that is lower than seawater. The maximum sedimentary δ98Mo observed in these anoxic sediments, which is 0.5–0.7‰ lower than seawater, appears to be set by Fe-Mo-S equilibration with ambient thiomolybdate species. We suggest diagenetic overprinting can cause more efficient capture of pond water Mo and causes sediment δ98Mo of originally iron-rich pond sediment to evolve to higher values at progressively higher aqueous sulfide concentrations.

Linking Hydrologic Connectivity in Salt Marsh Ponds to Fish Assemblages across a Heterogenous Coastal Habitat

ABSTRACT Ragan, A.N. and Wozniak, J.R., 2019. Linking hydrologic connectivity in salt marsh ponds to fish assemblages across a heterogenous coastal habitat. Journal of Coastal Research, 35(3), 545–...

Using Noble Gases to Compare Parameterizations of Air‐Water Gas Exchange and to Constrain Oxygen Losses by Ebullition in a Shallow Aquatic Environment

AbstractAccurate determination of air‐water gas exchange fluxes is critically important for calculating ecosystem metabolism rates from dissolved oxygen in shallow aquatic environments. We present a unique data set of the noble gases neon, argon, krypton, and xenon in a salt marsh pond to demonstrate how the dissolved noble gases can be used to quantify gas transfer processes and evaluate gas exchange parameterizations in shallow, near‐shore environments. These noble gases are sensitive to a variety of physical processes, including bubbling. We thus additionally use this data set to demonstrate how dissolved noble gases can be used to assess the contribution of bubbling from the sediments (ebullition) to gas fluxes. We find that while literature gas exchange parameterizations do well in modeling more soluble gases, ebullition must be accounted for in order to correctly calculate fluxes of the lighter noble gases. In particular, for neon and argon, the ebullition flux is larger than the differences in the diffusive gas exchange flux estimated by four different wind speed‐based parameterizations for gas exchange. We present an application of noble gas derived ebullition rates to improve estimates of oxygen metabolic fluxes in this shallow pond environment. Up to 21% of daily net oxygen production by photosynthesis may be lost from the pond via ebullition during some periods of biologically and physically produced supersaturation. Ebullition could be an important flux of oxygen and other gases that is measurable with noble gases in other shallow aquatic environments.

Effect of short-term, diel changes in environmental conditions on active microbial communities in a salt marsh pond

Effect of short-term, diel changes in environmental conditions on active microbial communities in a salt marsh pond

Bioaccumulation of Lead and Arsenic in Gastropods Inhabiting Salt Marsh Ponds in Coastal Bay of Fundy, Canada

The Cumberland Marsh Region (CMR), located on the coast of the Bay of Fundy, is a major feeding ground for waterfowl and contains significant coastal wetland systems. In this study, concentrations of lead (Pb) and arsenic (As) were assessed in the bottom sediments of various open water wetlands across the CMR, and gastropods were sampled from the same wetlands to assess bioaccumulation of these non-essential trace elements and the potential for transfer to higher trophic level species. It was predicted that gastropods would have higher concentrations of Pb and As from wetlands with higher concentrations of these elements in sediments. Although wetland sediments and gastropods had elevated Pb and As concentrations, in some cases above the Canadian Sediment Quality Guidelines for the protection of aquatic life, there were no significant correlations between sediment and gastropod trace element concentrations. Gastropod to sediment ratios of Pb and As concentrations were highest in the brackish wetlands, but overall, levels were not of toxicological concern. Wetland chemistries and gastropod physiologies are hypothesized to be driving factors in determining the level to which Pb and As will bioaccumulate and merit careful consideration when developing wetland management strategies.

High diversity of Ruppia meadows in saline ponds and lakes of the western Mediterranean

Saline inland and coastal waterbodies are valuable habitats that deserve attention for the protection of their unique submerged macrophyte beds that render the water clear, stabilize sediments and provide a habitat for high biomasses of invertebrates as food for waterfowl. The ‘continental seagrass’ Ruppia has the widest salinity tolerance among the submerged macrophytes and occurs in a wide variety of saline saltmarsh pond and lagoon systems. Although two cosmopolitan species Ruppia maritima and Ruppia cirrhosa are recognized in Europe and Ruppia drepanensis in the western Mediterranean, their diversity and distribution are not well known. This previously held traditional idea that there are only two widespread Ruppia species suggests a uniform and very homogenized population structure following the hypothesis of long-distance-dispersal through strong bird-mediated dispersal events. Therefore, the Ruppia chloroplast DNA diversity was investigated along a more than 1,000 km transect of the Iberian Peninsula. We studied 492 individuals from 11 wetland areas (17 ponds) and sequenced a 1,753-bp length of seven chloroplast introns. Eight haplotypes represented at least four distinct groups or taxa which is higher than commonly accepted. Six wetland areas contained more than one haplotype and within-pond diversity occurred within distances as small as 30 m (5 out of 17 cases). This underlines the importance of single waterbodies for harbouring haplotypic diversity in Ruppia. Unique haplotypes were observed in four wetland areas and R. maritima was detected only from a low salinity pond, suggesting the species might be more rare than previously accepted. The present results tend to minimize an overall effect of strong bird-mediated dispersal. This emphasizes the role of regional pond habitat diversity for the preservation of Ruppia taxa and their unique haplotype diversity in extreme saline habitats.

Evaluation of ecological network analysis: Validation of output

Ecological network analysis (ENA) is a modeling approach increasingly being used to evaluate food webs and provide an ecosystem-based approach to resource management. Unfortunately, validation of ENA output is rarely performed. This study represents part of a larger effort to critically evaluate ENA. Here we validate ENA output using stable isotope analysis (SIA), and where validation is not met, determine the effects of modifying trophic networks to reflect validation. Quantitative trophic networks representing four salt marsh ponds during late summer 2002 were constructed from an extensive field sampling program augmented by literature values. Ponds were used because they contain relatively simple food webs, have well defined boundaries, and allow for relatively complete sampling. SIA data (δ 13C, δ 15N, δ 34S) were used to validate effective trophic levels calculated by Ecopath for four separate networks, and carbon source estimates from NETWRK's total dependency matrix for four compartments in a single network. Effective trophic levels calculated by Ecopath matched those from δ 15N data for three of the four networks. Mean differences of trophic levels between methods ranged from 0.12 (95% CI = 0.27) to 0.34 (95% CI = 0.35) in three networks, and 0.53 (95% CI = 0.28) in the fourth. Agreement in carbon source estimates was determined graphically using ternary plots. Percent carbon from three sources (meiofauna, epiphytic algae, phytoplankton/POC) given in the total dependency matrix (NETWRK output) did not fall within the range given by stable isotope mixing models for three of four compartments. Modifications to reflect validation of carbon source estimates did not result in significant differences in ENA output. Lack of validation was often due to inherent differences in methods and assumptions imbedded in the models. Our study highlights the need for feedback between model construction, analysis and validation in improving trophic networks. Moreover, validation allows the effect of uncertainty in trophic networks to be evaluated by quantifying the sensitivity of ENA output to modifications in the models.

A Statistical Test of Network Analysis: Can it Detect Differences in Food Web Properties?

Ecological network analysis (ENA) is a modeling approach increasingly being used to examine food webs. However, most studies do not replicate networks, and a statistical evaluation of ENA is lacking. The major objectives of this study, therefore, were to evaluate statistically the effectiveness of ENA in detecting differences in food web properties and to compare ENA output with established community level indices. Quantitative trophic networks (n = 12) representing four high salt marsh ponds during three times (corresponding to low stress, high stress, and post-disturbance) were constructed from an extensive field sampling program augmented by literature values. Food webs of salt marsh ponds were used because these systems contain relatively simple food webs, have well defined boundaries, and allow for adequate replication. A null hypothesis was tested to determine how values of 12 indices from ENA output differed among the three stress/disturbance conditions (H o: low stress = high stress = post-disturbance). Results of both ANOVA and Friedman’s tests indicated most ENA indices were significantly different among the three stress/disturbance conditions. The amount of covariance among the indices was relatively low (7 of 66 were significant). Results were compared to differences in community indices (richness, evenness, and diversity) among the three stress/disturbance conditions. ENA output identified differences beyond those recognized by the community indices. Overall, networks were unique enough under different environmental conditions to provide statistically significant differences in ENA results. Our findings are supportive of the use of carefully constructed networks in food web analysis and for decision making in ecosystem-based management.

Reconstructing the development of eutrophication in Louisiana salt marshes

We collected sediment cores from three salt marsh ponds in coastal Louisiana to test the usefulness of proxies of eutrophication. One‐centimeter increments of 210Pb‐ and 137Cs‐dated sediment were analyzed for diatoms, pigments (phaeophytin and chlorophyll a), biogenic silica, percentage organic matter, percentage carbon, and percentage nitrogen. Both sediment chlorophyll a and a diatom‐based trophic index (TI) were significantly and positively correlated with riverine or local nutrient indices. Two diatom species, Amphora copulata Giffen and Navicula yarrensis Grunow, were significantly and negatively correlated with riverine and local nutrient indices. These results suggest that these variables can be used as potential indicators of trophic status. Results from a complete‐linkage cluster analysis on the diatom assemblage data demonstrated that the sediment cores could be split into three time periods: early 1900s (pre‐1930s/1940s), mid‐1900s (1930s/40s to 1960s/1970s), and late 1900s (1960s/70s to 1990s). Examination of the sediment chlorophyll a and TI data over these time periods, coupled with an analysis of variance of nutrient inputs between the time periods, suggests that nutrient loading increased dramatically from the mid‐ 1960s to the mid‐1970s. This study demonstrates that (1) a retrospective analysis of sediment cores can be conducted in highly variable salt marsh ponds and (2) these salt marsh environments are already affected by the higher nutrient loads from both riverine and local processes occurring over the last 50 years. Additional nutrient loading, e.g., from river diversion projects for the lower Mississippi River, may exacerbate eutrophication already evident in the marsh environment.

Elemental and stable isotope composition of Zostera noltii (Horneman) leaves during the early phases of decay in a temperate mesotidal lagoon

The aim of this study was to assess the changes in the elemental and stable isotope composition of Zostera noltii leaves during the early phases of decay. The litter biomass, the C, N and S elemental contents, the C:N ratios and the δ 13C, δ 15N and δ 34S values were monitored in a litterbag experiment for 60 days at Ria Formosa lagoon, southern Portugal in two different field conditions, permanently submerged in a salt marsh pond and at high intertidal. The elemental and stable isotope composition of both attached leaves and leaf wrack of Z. noltii was also determined. The overall decay rate of Z. noltii leaf material throughout the whole experimental period was k = 0.016 ± 0.001 d −1. Even though the biomass loss of the Z. noltii leaves after 30 days was about 25% higher within the pond than at the high intertidal, at the end of the experiment there were no significant differences between sites. The decay of the C and N content was of the same magnitude and thus the C:N molar ratio did not vary significantly in the experiment. The elemental content of the leaf wrack was in the range of the element content of leaf litter after 30–60 days of incubation. Contrary to other vascular plants rich in lignin, which degrades slowly, and thus forces the decrease of the δ 13C values during decay, the δ 13C values of Z. noltii leaves did not vary significantly over time or between incubation sites. The δ 15N values of leaves did not increase as has been reported for vascular plants with high C:N ratio. This suggests that during the early phase of the Z. noltii decomposition the community of decomposers relied mostly on the endogenous nitrogen of the plants, not needing to immobilize exogenous N. Stable isotope studies to assess the contribution of this species to the food web can rely on the natural δ 13C and δ 15N abundances of living tissues without any correction to account for decomposition. The analysis of the δ 34S values of Z. noltii detritus was not useful probably due to the contamination of the samples with pyrite, which has a depleted δ 34S signal.

Swimming activity of seabass: comparing patterns obtained in natural environment and in re‐circulating tanks under high density

Seabass (Dicentrarchus labrax) swimming activity was compared between natural environments and aquaculture facilities. Behaviour under natural conditions was assessed in a saltmarsh pond (250 m2, 18 × 14 × 0·8 m) using acoustic telemetry. From several surveys, we documented the diel activity rhythm and demonstrated group effects on swimming patterns and amplitudes by comparing activity of solitary fish with that of a fish living in a group of 60. Consequences of weather variability were also analysed and revealed a high sensitivity of fish to atmospheric conditions for both swimming and demand‐feeding behaviour. Behaviour in fish tanks was also studied using acoustic telemetry, as part of the EUREKA EU1 960 ‘Aqua‐Maki 2’ project investigating aspects of fish culture in re‐circulating tanks under high density. A re‐circulating hexagonal tank (5·4 × 5·4 m, 1·8 m depth, 48 m3) was equipped with positioning and demand‐feeding systems, oxygen and temperature probes. Initial density was 50 kg m3 in March and rose to 90 kg m3 at the end of the experiment in May. During this period, the movements of nine fish were continuously recorded for 24 h each, reaching a total of six 24 h episode at eight days interval. Swimming activity was analysed in terms of activity rhythms and space occupation specially around feeding events. The two data set and main results will be presented and compared to assess seabass behavioural plasticity and sensitivity to husbandry conditions.

Importance of Metabolism in the Development of Salt Marsh Ponds

Importance of Metabolism in the Development of Salt Marsh Ponds

Changes in midge (Diptera: Chironomidae) populations of sub-arctic supratidal vernal ponds in response to goose foraging

Grubbing and grazing by lesser snow geese (Anser caerulescens caerulescens) have led to loss of terrestrial vegetation and changes in the hydrology, chemistry and biology of shallow vernal ponds in a supratidal marsh at La Pérouse Bay, Manitoba, on the Hudson Bay coast. Chironomid populations in ponds have been examined because they are an important food source for ducks and shore birds, and are also widely used as ecological indicators of change. Seventy ponds were sampled during the summers of 1996 and 1997. They were located within a densely vegetated freshwater area, a relatively undamaged salt marsh and a degraded salt marsh where loss of vegetation had occurred as a result of goose foraging. Principal Components Analysis indicated that of 21 environmental descriptors, salinity was the primary gradient distinguishing ponds. Ponds in the degraded marsh that dried out early were the most saline (8 to 30‰) and those in the freshwater area the least saline (< 2‰). Densities of chironomids approached 22 000 m-2 with the highest numbers recorded from salt-marsh ponds. Estimated chironomid biomass in all ponds ranged between 0.7 and 9.0 g dry wt m-2 which reflected differences in species composition of ponds. Freshwater ponds contained seven species from six genera of which five did not occur in the other two habitats. Ponds in the undamaged salt marsh contained five species from five genera of which two were restricted to the area, while only the large-bodied Cricotopus (Isocladius) sp., most likely ornatus, was representative of ponds in the degraded salt marsh.

Effects of sustained-release methoprene and a combined formulation of liquid methoprene and Bacillus thuringiensis israelensis on insects in salt marshes.

Aquatic insects are an important component of the food web in salt marshes, therefore it is necessary to test whether pesticides used to control mosquitoes in salt marshes are safe for nontarget insects. We tested the nontarget effects of a combined formulation (duplex) of Bacillus thuringiensis israelensis (B.t.i.) and liquid methoprene (an insect development regulator) or sustained-release methoprene pellets (Altosid(R) pellets) by applying these materials to replicated salt marsh ponds at maximum label rates. Untreated ponds served as controls. We measured effects of the pesticides by rearing immature mosquitoes (Aedes dorsalis) and water boatmen (Trichocorixa reticulata) in predator-exclusion cages and by monitoring uncaged populations of invertebrates using replicated sweep-net samples. Both pesticides killed caged mosquitoes, and the activity of the Altosid(R) pellets continued through 99 days. There were no detectable effects of either pesticide on the survival or maturation of T. reticulata, or on abundances of uncaged invertebrates. The long-term activity of the pellets could help minimize mosquito abatement activity in salt marshes where there are breeding birds or endangered species. However, other studies suggest that this advantage needs to be balanced against the risks that sustained-release formulations could lead to development of resistance in mosquitoes or that initially undetected nontarget effects could build over time.

Benthic patterns in a salt marsh basin: a snapshot of Palude della Rosa (Venetian Lagoon, Italy)

The macrobenthos was sampled at 42 stations inDecember 1991 within a shallow eutrophic salt marsh pond, known as Palude della Rosa, located inside the VenetianLagoon, Italy. The benthic assemblages showed adistribution pattern made up of three different zonesreferred to in this paper as `Landward Zone',`Central Zone' and `Seaward Zone'. Thiszonation reflected both the distribution of the greenmacroalga Ulva rigidaAgardh and hydrology ofthe basin. The distribution patterns especially relateto the slow exchange of water due to the meanderingnature of channels surrounding the Palude dellaRosa.

The effects of species manipulation on growth and survival of an assemblage of juvenile estuarine fish

Growth and survival of Cyprinodon variegatus, Fundulus heteroclitus, Menidia beryllina, and Lucania parva, held in combination with an omnivorous grass shrimp–Palaemonetes pugio, and a predatory diving beetle Tropisternus lateralis, were measured at 12–60% in outdoor static microcosms that simulate salt marsh ponds. We predicted that the low species richness of this abiotically harsh but highly productive habitat would lead to a high degree of interaction among species. The presence of the beetle had no effect on the fish or the shrimp. Removal of the shrimp similarly had no detectable effect on the fish. There was a trend in proportions of survival among three fish: C. variegatus>F. heteroclitus>M. beryllina. Survival of M. beryllina was greater when it was alone at low densities of its own species (333 v. 667 fish m −3), and less when it was paired with F. heteroclitus. Interactions with other species diminished the growth of M. beryllina. Survival of F. heteroclitus was greater when it was alone at low density (333 m −3), than when the same number were placed together with Menidia and Cyprinodon at a total fish density of 999 m −3. There were no effects of removal of other species on survival or growth of C. variegatus at either 12′5 or 24%. This study showed that a complex array of interactions occurred among six common members of a salt marsh food web, but the degree of interaction Was less than We predicted.

The effects of species manipulation on growth and survival of an assemblage of juvenile estuarine fish

Growth and survival of Cyprinodon variegatus, Fundulus heteroclitus, Menidia beryllina, and Lucania parva, held in combination with an omnivorous grass shrimp–Palaemonetes pugio, and a predatory diving beetle Tropisternus lateralis, were measured at 12–60% in outdoor static microcosms that simulate salt marsh ponds. We predicted that the low species richness of this abiotically harsh but highly productive habitat would lead to a high degree of interaction among species. The presence of the beetle had no effect on the fish or the shrimp. Removal of the shrimp similarly had no detectable effect on the fish. There was a trend in proportions of survival among three fish: C. variegatus&gt;F. heteroclitus&gt;M. beryllina. Survival of M. beryllina was greater when it was alone at low densities of its own species (333 v. 667 fish m −3), and less when it was paired with F. heteroclitus. Interactions with other species diminished the growth of M. beryllina. Survival of F. heteroclitus was greater when it was alone at low density (333 m −3), than when the same number were placed together with Menidia and Cyprinodon at a total fish density of 999 m −3. There were no effects of removal of other species on survival or growth of C. variegatus at either 12′5 or 24%. This study showed that a complex array of interactions occurred among six common members of a salt marsh food web, but the degree of interaction Was less than We predicted.

Waterbird use of saltmarsh ponds created for open marsh water management : R. M. Erwin, J. S. Hatfield, M. A. Howe & S. S. Klugman, Journal of Wildlife Management, 58(3), 1994, pp 516–524

Waterbird use of saltmarsh ponds created for open marsh water management : R. M. Erwin, J. S. Hatfield, M. A. Howe & S. S. Klugman, Journal of Wildlife Management, 58(3), 1994, pp 516–524