Marsh Ponds Research Articles

Development and Field Testing of a Wireless Data Relay System for Amphibious Drones

Amphibious (air and water) drones, capable of both aerial and aquatic operations, have the potential to provide valuable drone applications in aquatic environments. However, the limited range of wireless data transmission caused by the low antenna height on water and reflection from the water surface (e.g., 45 m for vertical half-wave dipole antennas with the XBee S2CTM, estimated using the two-ray ground reflection model) persists as a formidable challenge for amphibious systems. To overcome this difficulty, we developed a wireless data relay system for amphibious drones using the mesh-type networking functions of the XBeeTM. We then conducted field tests of the developed system in a large marsh pond to provide experimental evidence of the efficiency of the multiple-drone network in amphibious settings. In these tests, hovering relaying over water was attempted for extension and bypassing obstacles using the XBee S2CTM (6.3 mW, 2.4 GHz). During testing, the hovering drone (<10 m height from the drone controller) successfully relayed water quality data from the transmitter to the receiver located approximately 757 m away, but shoreline vegetation decreased the reachable distance. A bypassing relay test for vegetation indicated the need to confirm a connected path formed by pair(s) of mutually observable drones.

Farming Sparus aurata (Teleostei: Sparidae) in marsh ponds: trophic characterization and trace metal accumulation

Considering the overexploitation of fishing on most of the world coasts, the ingestion of fish and shellfish will depend mostly on aquaculture production. Since intensive mariculture usually involves environmental impact, developing sustainable cultures is a priority. In this sense, salt marshes can provide ecosystem services and incorporate both conservation and extensive aquaculture activities. In the present study we compared gilthead seabream Sparus aurata Linnaeus, 1758 cultured in extensive and semi-intensive marsh ponds with wild conspecifics from surrounding coastal areas, using trophic characterization (diet analysis and stable isotopes) and trace metal accumulation. Stomach content analysis revealed different feeding habits among gilthead seabream from different origin. Although wild specimens had the most diverse diet, results of stable isotopes showed that extensive diet had the wider isotopic niche and revealed the highest similarities between wild and extensively cultured gilthead seabream. A similar trace element signature was also measured in wild and extensive culture, whereas the semi-intensive culture showed different concentrations for several elements. Cr, Fe and Mn showed the highest concentrations in semi-intensive cultured fish, while As and Zn showed the lowest values in this group. In any case, average values measured in both extensive and semi-intensive culture were, in general terms, below the hazardous limits provided by the standards recommended for trace metals by national and international regulations. Therefore, marsh ponds provide a suitable environment where the cultured fish, especially extensive, should be promoted.

How much waste can the amphipod Gammarus insensibilis remove from aquaculture effluents? A first step toward IMTA

In recent years marine amphipods have been highlighted as an alternative live feed resource for Integrated Multi-Trophic Aquaculture (IMTA). Gammarus insensibilis Stock, 1966 is a native amphipod from the Mediterranean Sea and the north Atlantic Ocean and it is highly abundant in southern Spain marsh ponds. Its high potential for being intensively reared has been demonstrated in previous studies, as this species can feed on detritus and presents an interesting nutritional profile. In the present work, G. insensibilis specimens were maintained in closed batches at three different densities (100, 500 and 1000 ind L−1) and fed on dry or wet detritus (uneaten food and faeces from a fish RAS effluent) in order to assess for the first time the amount of wastes that they were able to remove. In parallel, a trial was performed to study the effect of dissolved inorganic nitrogen compounds (highly abundant in aquaculture effluents) on their survival, and the median lethal concentrations (LC50) in 96 h were calculated. Amphipods in all experiments and conditions showed promising survival rates higher than 80%. No advantages were observed when gammarids were maintained at high densities due to the significantly higher ammonium concentrations in these treatments, having an effect on intake but allowing sub-lethal conditions. Indeed, Gammarus insensibilis showed the highest tolerance for nitrate (1308 mg N-NO3− L−1), followed by nitrite (39.77 mg N-NO2− L−1) and ammonium (33.23 mg N-NH4+ L−1). Individuals at low densities removed significantly higher amounts of detritus, between 154.98 and 169.78 mg (dry weight detritus) per g (wet weight amphipods) and day. No differences were observed between removal rate of dry or wet detritus. Thus, authors recommend the use of wet detritus for a better handling and up-scaled trials in open or RAS systems equipped with a biofilter in order to avoid high ammonium concentrations impacting on intake.

Peat Decomposition and Erosion Contribute to Pond Deepening in a Temperate Salt Marsh

AbstractSalt marsh ponds expand and deepen over time, potentially reducing ecosystem carbon storage and resilience. The water filled volumes of ponds represent missing carbon due to prevented soil accumulation and removal by erosion and decomposition. Removal mechanisms have different implications as eroded carbon can be redistributed while decomposition results in loss. We constrained ponding effects on carbon dynamics in a New England marsh and determined whether expansion and deepening impact nearby soils by conducting geochemical characterizations of cores from three ponds and surrounding high marshes and models of wind‐driven erosion. Radioisotope profiles demonstrate that ponds are not depositional environments and that contemporaneous marsh accretion represents prevented accumulation accounting for 32%–42% of the missing carbon. Erosion accounted for 0%–38% and was bracketed using radioisotope inventories and wind‐driven resuspension models. Decomposition, calculated by difference, removes 22%–68%, and when normalized over pond lifespans, produces rates that agree with previous metabolism measurements. Pond surface soils contain new contributions from submerged primary producers and evidence of microbial alteration of underlying peat, as higher levels of detrital biomarkers and thermal stability indices, compared to the marsh. Below pond surface horizons, soil properties and organic matter composition were similar to the marsh, indicating that ponding effects are shallow. Soil bulk density, elemental content, and accretion rates were similar between marsh sites but different from ponds, suggesting that lateral effects are spatially confined. Consequently, ponds negatively impact ecosystem carbon storage but at current densities are not causing pervasive degradation of marshes in this system.

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.

Exploring Neotropical anuran parasites: a morphological, life cycle and phylogenetic study of Catadiscus marinholutzi (Trematoda: Diplodiscidae).

Amphistome species belonging to the genus Catadiscus are poorly studied intestinal trematodes found primarily in Neotropical anurans. Herein, developmental stages of an amphistome species found during herpetological and malacological surveys in a temporary marsh pond from Brazil were subjected to morphological (light and scanning electron microscopy) and molecular analyses. Adult parasites recovered from anurans were identified as Catadiscus marinholutzi. Amphistome cercariae found in the planorbid snails Drepanotrema depressissimum and Drepanotrema lucidum from the same waterbody were used for experimental and molecular studies. Immature parasites, morphologically compatible with members of Catadiscus, were experimentally obtained in laboratory-reared tadpoles. Sequencing of a partial region of 28S rDNA gene of both adult and cercariae revealed 100% similarity between these developmental stages, confirming their conspecificity. Phylogenetic analyses were attempted for the first time to reveal the position of a species of Catadiscus in the superfamily Paramphistomoidea. Catadiscus marinholutzi falls in a virtual polytomy together with other paramphistomoids, which leaves its phylogenetic relationships within the group unclear. Moreover, the high genetic divergence to Diplodiscus spp. (10.06–10.84%) cast doubts on the placement of Catadiscus within Diplodiscidae. Hence the species composition of the Diplodiscidae should be re-evaluated in further studies using a broader spectrum of related taxa.

Pond Dynamics Yield Minimal Net Loss of Vegetation Cover Across an Unditched Salt Marsh Landscape

Ponds in salt marshes are often misinterpreted as a symptom of degradation, yet ponds can also be part of a cyclical process of pond formation, expansion, breaching by tidal creeks, and vegetation recovery. Pond dynamics may be altered by accelerated sea level rise, with consequences for the long-term stability of ecosystems. This study tests the prediction that ponds are in dynamic equilibrium across one of the largest expanses of unditched salt marsh in the Northeast USA by (1) examining change in pond and marsh area between 1970 and present in both ditched and unditched regions and (2) by tracking individual pond dynamics across an 87-year time series. Across all marshes, vegetated area declined by 6.3%, with losses primarily due to edge erosion. Ditched marsh had significantly less pond area than unditched marsh. In unditched marshes, we found that net pond area has remained unchanged since 1970 because the amount of marsh conversion to ponds is equivalent to the amount of pond recovery to marsh. The overall extent of ponds connected to tidal creeks is increasing relative to isolated ponds that retain water at low tide, which suggests that some rates of change may be decoupling. This may correspond to a decline in the rate of pond formation, but other factors such as an increase in pond breaching rate and a lag in vegetation recovery rate may also contribute to this pattern. A nuanced understanding of marsh ponds needs to be incorporated into marsh condition assessments and establishment of restoration priorities so that ponds are not interpreted as evidence of degradation when they are exhibiting a recovery cycle. Unditched marshes around the world are a rare resource that remains essential for advancing scientific understanding and serving as reference sites for restoration of marshes altered by past management.

Biogeomorphic patterns emerge with pond expansion in deteriorating marshes affected by relative sea level rise

AbstractInterior marsh pond formation has been commonly observed in tidal marshes affected by high rates of relative sea level rise (RSLR). However, it is difficult to conclude whether an accretion deficit (accretion which does not keep pace with RSLR) or natural ice and wrack disturbance has driven pond formation. We propose that marsh deterioration caused by accretion deficit can be differentiated from that caused by other disturbances based upon temporal vegetation changes and the spatial configuration of vegetation zones relative to tidal creeks and the marsh platform. We tested this hypothesis in six newly ponded sites within RSLR‐affected marshes in Deal Island, Chesapeake Bay. At each site, we used field surveys and remote sensing to study spatiotemporal dynamics of marsh vegetation, marsh topography, and tidal creek incision. We found flood tolerant plants displaced flood intolerant species over time in the landward direction, or upslope, of ponds. A reverse species transition was observed seaward of ponds because tidal creek incision alleviated interior marsh inundation. The landscape‐scale biogeographic pattern we have recognized sheds light on how plants adapt to chronically reshaped geomorphological configurations of the marsh platform, which differentiates ponding caused by accretion deficit from ponding caused by natural and artificial disturbances. Furthermore, our results point to vegetation patterns that can be used as early warning signals of interior marsh loss to ponding. As ponding has been a major driver of tidal marsh habitat loss in microtidal marshes around the world, early indicators of decline are sorely needed to direct conservation activities.

Aquaculture waste as food for amphipods: the case of Gammarus insensibilis in marsh ponds from southern Spain

Amphipods are emerging as an alternative food resource for fishes and cephalopods in aquaculture. Gammarus insensibilis (Stock, 1996), one of the dominant amphipods inhabiting marsh ponds in southern Spain, has been recently proposed as a promising candidate for being intensively cultured due to its adequate nutritional profile, large body size, and high natural densities. The main aim of this study was to determine whether waste products of aquaculture (such as detritus in the form of fish feces or Ulva sp.) provided an adequate diet for the amphipod in comparison to other traditional diets, such as Artemia nauplii or phytoplankton. G. insensibilis was cultured twice in tanks with 5 treatments: 4 experimental diets (detritus, Ulva sp., Artemia nauplii, and phytoplankton) were used, and one no-feed treatment. Amphipods fed with the two alternative diets, detritus and Ulva, showed promising survival higher than 40% and high concentrations of palmitic acid (16:0), oleic acid (18:1n9), arachidonic acid (20:4n6) (ARA), eicosapentaenoic acid (20:5n3) (EPA), and docosahexaenoic acid (22:6n3) (DHA). Therefore, large-scale culture of this amphipod using inexpensive diets in indoor facilities could provide a nutritious product for aquaculture. The potential development of a sustainable culture using this species in marsh ponds is also discussed in the context of Integrated Multi-Trophic Aquaculture (IMTA).

Salt Marsh Pond Biogeochemistry Changes Hourly‐to‐Yearly but Does Not Scale With Dimensions or Geospatial Position

AbstractShallow ponds are expanding in many salt marshes with potential impacts on ecosystem functioning. Determining how pond characteristics change over time and scale with physical dimensions and other spatial predictors could facilitate incorporation of ponds into projections of ecosystem change. We evaluated scaling relationships across six differently sized ponds in three regions of the high marshes within the Plum Island Ecosystems‐Long Term Ecological Research site (MA, USA). We further characterized diel fluctuations in surface water chemistry in two ponds to understand short‐term processes that affect emergent properties (e.g., habitat suitability). Primary producers drove oxygen levels to supersaturation during the day, while nighttime respiration resulted in hypoxic to anoxic conditions. Diel swings in oxygen were mirrored by pH and resulted in successive shifts in redox‐sensitive metabolisms, as indicated by nitrate consumption at dusk followed by peaks in ammonium and then sulfide overnight. Abundances of macroalgae and Ruppia maritima correlated with whole‐pond oxygen metabolism rates, but not with surface area (SA), volume (V), or SA:V. Moreover, there were no clear patterns in primary producer abundances, surface water chemistry, or pond metabolism rates across marsh regions supplied by different tidal creeks or that differed in distance to upland borders or creekbanks. Comparisons with data from 2 years prior demonstrate that plant communities and biogeochemical processes are not in steady state. Factors contributing to variability between ponds and years are unclear but likely include infrequent tidal exchange. Temporal and spatial variability and the absence of scaling relationships complicate the integration of high marsh ponds into ecosystem biogeochemical models.

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.

Modeling the spatial dynamics of marsh ponds in New England salt marshes

Ponds are common features on salt marshes, yet it is unclear how they affect large-scale marsh evolution. We developed a spatially explicit model that combines cellular automata for pond formation, expansion, and drainage, and partial differential equations for elevation dynamics. We use the mesotidal Barnstable marsh (MA, USA) as a case study, for which we measured pond expansion rate by remote sensing analysis over a 41-year time span. We estimated pond formation rate by comparing observed and modeled pond size distribution, and predicted pond deepening by comparing modeled and measured pond depth. The Barnstable marsh is currently in the pond recovery regime, i.e.,every pond revegetates and recovers the necessary elevation to support plant growth after re-connecting to the channel network. This pond dynamic creates an equivalent (i.e.,spatially and temporally averaged over the whole marsh) 0.5–2 mm/yr elevation loss that needs to be supplemented by excess vertical accretion. We explore how the pond regime would change with decreased sediment supply and increased relative sea-level rise (RSLR) rate, focusing on the case in which the vegetated marsh keeps pace with RSLR. When the RSLR rate remains below the minimum unvegetated deposition rate, the pond dynamics is nearly unaltered and ponds always occupy ~10% of the marsh area. However, when RSLR rate exceeds this threshold, the ponds in the marsh interior – which receive the least amount of suspended sediment – do not recover after drainage. These ponds transition to mudflats and permanently occupy up to 30% of the marsh area depending on RSLR rate. For marshes with a small tidal range, such as the microtidal Sage Lot Pond marsh on the opposite side of the peninsula from Barnstable marsh, high RSLR rates could bring every portion of the marsh into the pond runaway regime, with the whole marsh eventually converting into mudflats. In this regime, the existing marsh would disappear within centuries to millennia depending on the RSLR rate. Because of the spatial and temporal components of marsh evolution, a single RSLR threshold value applied across the entire marsh landscape provides a limited description of the marsh vulnerability to RSLR.

Evaluating indicators of marsh vulnerability to sea level rise along a historical marsh loss gradient

AbstractSea level rise (SLR) is threatening coastal marshes, leading to large‐scale marsh loss in several micro‐tidal systems. Early recognition of marsh vulnerability to SLR is critical in these systems to aid managers to take appropriate restoration or mitigation measures. However, it is not clear if current marsh vulnerability indicators correctly assess long‐term stability of the marsh system. In this study, two indicators of marsh stress were studied: (i) the skewness of the marsh elevation distribution, and (ii) the abundance of codominant species in mixtures. We combined high‐precision elevation measurements (GPS), LiDAR imagery, vegetation surveys and water level measurements to study these indicators in an organogenic micro‐tidal system (Blackwater River, Maryland, USA), where large‐scale historical conversion from marshes to shallow ponds resulted in a gradient of increasing marsh loss. The two indicators reveal increasingly stressed marshes along the marsh loss gradient, but suggest that the field site with the most marsh loss seems to experience less stress. For the latter site, previous research indicates that wind waves generated on interior marsh ponds contribute to lateral erosion of surrounding marsh edges and hence marsh loss. The eroded marsh sediment might temporarily provide the remaining marshes with the necessary sediment to keep up with relative SLR. However, this is only a short‐term alleviation, as lateral marsh edge erosion and sediment export lead to severe marsh loss in the long term. Our findings indicate that marsh elevation skewness and the abundance of codominant species in mixtures can be used to supplement existing marsh stress indicators, but that additional indices such as fetch length and the sediment budget should be included to account for lateral marsh erosion and sediment export and to correctly assess long‐term stability of micro‐tidal marshes. © 2020 John Wiley & Sons, Ltd.

Metacercariae of Heterodiplostomum lanceolatum (Trematoda: Proterodiplostomidae) found in Leptodactylus podicipinus (Anura: Leptodactylidae) from Brazil: a morphological, molecular and ecological study.

The trematodes from South American reptiles are poorly known, with only one life cycle completely characterized. We used molecular and morphological methods to characterize diplostomoid metacercariae found in 29 of 86 pointedbelly frogs, Leptodactylus podicipinus (Cope, 1862) collected in a marsh pond in Selvíria, in the central-west region of Brazil. The metacercariae were identified as Heterodiplostomum lanceolatum Dubois, 1936 (Proterodiplostomidae), a rarely reported species that matures in snakes. In phylogenetic analysis of partial sequences from 28S rDNA, H. lanceolatum fell within a polytomy with the proterodiplostomid Crocodilicola pseudostoma (molecular divergence of 4.1%) and other members of the superfamily Diplostomoidea. Our collections provide insights into the ecology of this parasite, in that infected frogs were smaller than uninfected frogs, and metacercariae were more numerous in the abdominal cavity and hindlimb muscles than in abdominal muscles, which suggests directions for future research on the transmission and pathology of this proterodiplostomid.

A Tool for Rapid Assessment of Hydrological Connectivity Patterns in Texas Coastal Wetlands: Linkages between Tidal Creeks and Coastal Ponds

Coastal salt marshes are heterogeneous, spatially complex ecosystems. The degree of hydrological connectivity in these systems can be a significant driver in the flux of energy, organisms, and nutrients across the marsh landscape. In tidally driven systems, the frequency and magnitude of hydrological connection events results in the creation of a matrix of intermittently connected coastal wetland habitats, some of which may be hydrologically isolated or partially drained at any given time. Previous approaches to understanding landscape-level hydrologic connectivity patterns have required either intensive long-term monitoring or spatially explicit modeling. In this paper, we first describe a 13-month field study in the Guadalupe Estuary of the Texas Gulf Coast that linked hydrological connectivity patterns between a saltwater pond to water levels in an adjacent tidal creek and nearby San Antonio Bay. We next describe the integration of these field data with high-resolution digital elevation models and environmental parameters to develop a spatially explicit model that is a Simulation of Landscape-level Oscillations in Salt Marsh Hydroperiod (SLOSH). We evaluated the ability of SLOSH to simulate trends in landscape-level patterns of hydrological connectivity between a tidal creek and an inland marsh pond. Magnitude and periodicity of simulated and observed water-level fluctuations in the pond were similar. Highest creek water levels, resulting in high frequency and duration of hydrological connectivity with the pond, corresponded with the highest bay water levels, which occurred during September and October. Lowest creek water levels, resulting in low frequency and duration of hydrological connectivity, corresponded with the lowest bay water levels, which occurred during December through February. By simulating the pulsing structure of salt marsh hydrology, SLOSH creates the foundation on which to assess how additional drivers (precipitation, wind, freshwater inflows, etc.) can influence coastal marsh hydrology and overall ecology. Citation: Swannack TM, Wozniak JR, Grant WE, Davis SE III. 2019. A tool for rapid assessment of hydrological connectivity patterns in Texas coastal wetlands: linkages between tidal creeks and coastal ponds. Texas Water Journal. 10(1):46-59. Available from: https://doi.org/10.21423/twj.v10i1.7073.

STUDY OF MOLLUSCS’ INFESTATION WITH FASCIOLA HEPATICA IN BRYANSK REGION

The intermediate host of Fasciola hepatica is Lymnaea truncatula mollusk. However, participation of other species of mollusks (L. stagnalis, Galba palustris, etc.) in the development cycle of F. hepatica is not excluded. In this connection, we have studied the distribution of mollusks of these species in the territory of the Bryansk region. The aim of the work was to carry out a study on the invasion of fasciol larvae of mollusks on pastures of trematodiasis-unfriendly farms of the Bryansk region. On farms, the density of mollusks and their species, as well as the dynamics of the infection of mollusks by the partenite stages of F. hepatica, were determined. The work was carried out from May to October 2018 on 3 pastures with an area of 2 to 5 hectares. The study was subjected to mollusks: small pond snail L. truncatula in the amount of from 149 to 151 specimens, ordinary pond snail – L. stagnalis from 10 to 18 specimens, marsh pond snail – L. palustris from 30 to 85 specimens, iushkoviy pond snail – L. auricularia from 4 to 21 specimens. Mollusks were examined every month during the pasture period (May-October) for infection with fasciol larvae by the compressor method. It was revealed that only small pond snail L. truncatula was infested by the larval stages of development of fasciol. The rest of the limneids were free from this trematodase invasion. The small pond snail was infected more intensely in September. The fasciol larvae of the small pond snail were recorded in May, June, August and September; the infection rate was 1.3%, 2.6%, 6.6% and 8%, respectively.

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.

Assessing Variability in Juvenile Brown Shrimp Growth Rates in Small Marsh Ponds: An Exercise in Model Evaluation and Improvement

AbstractBrown shrimp Farfantepenaeus aztecus support a commercially important fishery in the northern Gulf of Mexico, and the juvenile shrimp use coastal estuaries as nurseries. Production of young shrimp from these nurseries, and hence commercial harvest of adults from the Gulf, is highly variable from year to year. Our recently published, individual‐based model attempted to explain this variability as a function of habitat and the environmental factors such as temperature, salinity, and access to intertidal marsh habitat. We conducted a mark–recapture field study between April 12 and June 9, 2011, to provide growth rate data for model testing, as well as to further examine factors that affect growth, including available food biomass. Brown shrimp growth rates were measured in three polyhaline marsh ponds over periods of 2 to 4 weeks. We recorded hourly temperature and flooding data and measured biomass of infaunal food organisms. We parameterized our production model with input from 2011 to compare modeled output with observed data. Mean growth rate estimates from the model were similar to the estimated mean growth rate observed in the field (1.13 mm/d and 1.06 mm/d, respectively); however, field growth rates differed significantly among three marsh ponds (1.02, 1.03, and 1.26 mm/d). Data on infaunal biomass suggest that spatial and temporal variability in available food organisms is related to differences in shrimp growth, and the inclusion of such information may enhance the model.