Tidal Wetland Ecosystems Research Articles

Characterizing low‐lying coastal upland forests to predict future landward marsh expansion

AbstractSea level rise (SLR) is causing vegetation regime shifts on both the seaward and landward sides of many coastal ecosystems, with the eastern coast of North America experiencing accelerated impacts due to land subsidence and the weakening of the Gulf Stream. Tidal wetland ecosystems, known for their significant carbon storage capacity, are crucial but vulnerable blue carbon habitats. Recent observations suggest that SLR rates may exceed the threshold for elevation gain primarily through vertical accretion in many coastal regions. Therefore, research has focused on mapping the upslope migration of marshes into suitable adjacent lands, as this landward gain may be the most salient process for estimating future wetland resiliency to accelerated rates of SLR. However, our understanding of coastal vegetation characteristics and dynamics in response to SLR is limited due to a lack of in situ data and effective mapping strategies for delineating the boundaries, or ecotones, of these complex coastal ecosystems. In order to effectively study these transitioning ecosystems, it is necessary to employ reliable and scalable landscape metrics that can differentiate between marsh and coastal forests. As such, integrating vegetation structure metrics from light detection and ranging (lidar) could enhance traditional mapping strategies compared to using optical data alone. Here, we used terrestrial laser scanning (TLS) to measure changes in forest structure along elevation gradients that may be indicative of degradation associated with increased inundation in the Delaware Bay estuary. We analyzed a set of TLS‐derived forest structure metrics to investigate their relationships with elevation, specifically seeking those that showed consistent change from the forest edge to the interior. Our findings revealed a consistent pattern between elevation and the plant area index (PAI), a metric that holds potential for enhancing the delineation of complex coastal ecosystem boundaries, particularly in relation to landward marsh migration. This work provides support for utilizing lidar‐derived forest structural metrics to enable a more accurate assessment of future marsh landscapes and the overall coastal carbon sink under accelerated SLR conditions.

Assessing Tidal Hydrodynamics in a Tropical Seascape Using Structure‐from‐Motion Photogrammetry and 2D Flow Modelling

Tidal wetlands continue to be threatened by changes in seascape hydrological regime and connectivity resulting from human activities (e.g. urbanisation, engineered barriers) and climate change. Reliable and parsimonious models that can be used by managers and practitioners to simulation tidal wetland hydroperiod dynamics (duration, depth, and frequency of tidal inundation) at high-resolution are limited presumably because these ecosystems have very low elevation across their flooding plain. Here, we developed a two-dimensional hydrodynamic model parameterised using a high-resolution (3 cm) and accurate (8-cm RMSE elevation error) digital elevation model (DEM) and land cover map (2-cm resolution) derived from unoccupied aerial vehicles (UAVs) structure from motion photogrammetry (SfM) to assist in the understanding of tidal wetland hydroperiod and hydrological connectivity of an upper tidal Australian tropical seascape. Ground-based water level datasets were used to calibrate and validate the model with higher accuracy (RMSE = 7 cm between maximum observed and simulated depth). The high-resolution approach demonstrates how small changes in topography such as vehicle tracks can interfere with hydrological connectivity. Centimetre-changes in tidal height resulted in important variations (10 ha) in the total area of the wetland being inundated, suggesting that small anthropogenic modifications of tidal inputs (e.g. culverts and sea-level rise) might have important implications on tidal wetland inundation patterns. Despite challenges related to reconstructing topography in densely vegetated areas and obtaining bathymetric data, the method developed here represents an accurate and cost-effective approach to quantify tidal wetland hydroperiod. This approach assists in planning, defining, and implementing effective and measurable restoration and protection projects of tidal wetland ecosystems. Graphical

Increase in iron-bound organic carbon content under simulated sea-level rise: A “marsh organ” field experiment

Rising sea levels have increased the risk of intense flooding in tidal wetlands, potentially leading to rises in soil iron-bound organic carbon (Fe-OC) contents by inhibiting microbial activity. However, flooding-induced Fe-OC accumulation may be attenuated by root activities of tidal wetland plants, which remains under-investigated in tidal wetlands. Here we established manipulative “marsh organ” filed experiments with soils collected from an oligohaline tidal wetland and introduced the indigenous plant species Phragmites australis (Cav.) Trin. ex Steud. These “marsh organ” mesocosms were then subjected to three flooding water-level treatments over a period of 3.5 years. Overall, root biomass, root porosity, and rhizosphere ferric iron-to-ferrous iron [Fe(III):Fe(II)] ratio increased with flooding levels, indicating that enhanced flooding promotes root oxygen loss of tidal wetland plants. The abundances of Fe-oxidizing bacteria (Gallionella) and Fe-reducing bacteria (Geobacter) increased, whereas the abundance of sulfate-reducing bacteria (dsrA gene) decreased with increased flooding, indicating a diversion of Fe from Fe-sulfur associations towards microbially-mediated Fe redox cycling. The soil organic carbon (SOC) pool did not change with increased flooding; however, the Fe-OC-to-SOC ratio (fFe-OC) increased from 9 to 18%. The fFe-OC was strongly related to soil amorphous Fe(III) concentrations and the activities of soil C-acquiring enzymes, both of which were affected by rhizosphere Fe(III):Fe(II) ratios. Thus, increased root oxygen loss, along with enhanced flooding, facilitated increases in amorphous Fe(III) concentrations and C-acquiring enzyme activity. Increased soil amorphous Fe(III) concentrations further promoted Fe-OC accumulation, whereas increased soil C-acquiring enzyme activities reduced the labile organic C pool. Overall, the dominance of the Fe-OC pool increased under enhanced flooding, owing to increased oxygen loss from the roots. Therefore, we outlined that soil C stability will increase in tidal wetland ecosystems that are exposed to future sea-level rise.

Selective associations of organic matter components with ferrihydrite: Implications for Fe-organic matter preservation in tidal flat wetlands

The association of organic matter (OM) with iron (Fe) is a critical mechanism to preserve OM in intertidal coastal ecosystems such as salt marshes and mangroves. The present study aimed to investigate the influence of the organic carbon to Fe molar ratio (OC/Fe), ionic strength, and OM composition on Fe-OM association. Fe-OM was prepared using humic acids extracted from salt marsh and mangrove sediments by the adsorption process in the OC/Fe molar ratios of 0.01–1.0 and by the coprecipitation process in the OC/Fe molar ratios of 0.1–9.9. Sample properties were studied by X-ray diffraction, scanning electron microscopy, ultraviolet–visible spectroscopy, attenuated total reflection Fourier transform infrared spectroscopy, three-dimensional fluorescence excitation emission matrix spectroscopy, and pyrolysis–gas chromatography/mass spectrometry. The results showed that selective associations of OM components with ferrihydrite were affected by the association mode (e.g., adsorption and coprecipitation), OC/Fe molar ratio, OM composition and ionic strength. Abundant aliphatic compounds could be adsorbed on ferrihydrite. Moreover, ferrihydrite was prone to preserve humic-like fluorescent components through the adsorption process. The protein-like fluorescent components and aliphatic compounds had high affinity for ferrihydrite during coprecipitation with low OC/Fe molar ratios. An increase in the OC/Fe molar ratio resulted in coprecipitation of aromatic compounds with ferrihydrite. Salinity-induced flocculation caused more amount of aromatic and polycyclic aromatic compounds to associate with ferrihydrite during the coprecipitation process. Compared to the salt marsh OM, more N-compounds and less aliphatic compounds in the mangrove OM were coprecipitated with ferrihydrite. This study provided important insights into the mechanisms of OM preservation with ferrihydrite in tidal wetland ecosystems.

Incorporating biotic phosphorus-acquisition strategies into soil phosphorus transformation under long-term salinization in a tidal wetland

Tidal wetland plants can maintain high primary productivity under salinization, even with low phosphorus (P) availability. However, little is known about how they adapt to salinization-induced ecosystem P limitation over time. We established mesocosms using tidal freshwater wetland soils and the salt-tolerant plant Cyperus malaccensis and subjected them to short-term (6 months) and long-term (3.5 years) salinization. Overall, short-term salinization did not change plant or microbial biomass nitrogen/P ratios, whereas long-term salinization increased both, indicating that short-term salinization did not alter ecosystem P limitation, but long-term salinization exacerbated it. Concurrently, short-term salinization reduced the moderately labile inorganic P (Pi) pool, whereas long-term salinization also reduced the hydrolyzable organic P (Po) and primary mineral P pools. During both short- and long-term salinization, moderately labile Pi mobilization exhibited a negative correlation with Fe sulfide concentration and a positive correlation with Fe(III) concentrations. These results suggested that both short- and long-term salinization obtained P through abiotic P-acquisition strategies. Mobilization of the primary mineral P pool and hydrolyzable Po pools was negatively linked to root arbuscular mycorrhizal fungi (AMF) biomass and soil alkaline phosphomonoesterase (ALP) activity, respectively. This indicated that long-term salinization acquired P via biotic P-acquisition strategies. Specifically, soil microorganisms increased fungi predominance and thereby increased ALP activity to convert hydrolyzable Po, while tidal wetland plants enhanced root AMF associations to release carboxylate to transform primary mineral P. Overall, our results highlight that abiotic P-acquisition strategies could offset the ecosystem P limitation during short-term salinization, whereas biotic P-acquisition strategies play a more important role in soil P transformation under long-term salinization. Through biotic P-acquisition, tidal wetland ecosystems can maintain high plant primary productivity through biotic P-acquisition even under P-limited conditions, exhibiting increased resilience to sea-level rise.

Lidar-Imagery Fusion Reveals Rapid Coastal Forest Loss in Delaware Bay Consistent with Marsh Migration

Tidal wetland ecosystems and their vegetation communities are broadly controlled by tidal range and inundation frequency. Sea-level rise combined with episodic flooding events are causing shifts in thresholds of vegetation species which reconstructs the plant zonation of the coastal landscape. More frequent inundation events in the upland forest are causing the forest to convert into tidal marshes, and what is left behind are swaths of dead-standing trees along the marsh–forest boundary. Upland forest dieback has been well documented in the mid-Atlantic; however, reliable methods to accurately identify this dieback over large scales are still being developed. Here, we use multitemporal Lidar and imagery from the National Agricultural Imagery Program to classify areas of forest loss in the coastal regions of Delaware. We found that 1197 ± 405 hectares of forest transitioned to non-forest over nine years, and these losses were likely driven by major coastal storms and severe drought during the study period. In addition, we report decreases in Lidar-derived canopy height in forest loss areas, suggesting forest structure changes associated with the conversion from forest to marsh. Our results highlight the potential value of integrating Lidar-derived metrics to determine specific forest characteristics that may help predict future marsh migration pathways.

Trade-off between microbial carbon use efficiency and microbial phosphorus limitation under salinization in a tidal wetland

Sea level rise–induced salinization is projected to influence the decomposition of soil carbon (C) in tidal wetlands. Despite evidence showing that microbial metabolism can determine the fate of soil C decomposition, the response of microbial metabolism to salinization in tidal wetlands remains largely unknown. Microbial metabolism is impacted by the microbial metabolic limitation and carbon use efficiency (CUE), which can provide mechanistic insights into soil C decomposition. Here, we measured microbial metabolic limitation, microbial CUE, and extracellular enzyme activities along an estuarine salinity gradient ranging from freshwater (0.1 ± 0.1 mg g−1) to oligohaline (2.1 ± 0.5 mg g−1) in a tidal wetland. Overall, microorganisms were limited by phosphorus (P) in the tidal wetlands, where salinization increased microbial P limitation by 34%. The enhanced microbial P limitation was attributed to increases in soil C:P and belowground biomass, as well as decreases in root C:P with increasing salinity. Microbial CUE decreased from 0.38 to 0.33 as salinity increased, while microbial P limitation was negatively correlated with microbial CUE, representing the trade-off between the two. Furthermore, microbial P limitation was positively associated with C-, nitrogen (N)-, and P-acquiring extracellular enzyme activities, while all these enzyme activities were negatively correlated with microbial CUE. These results illustrate that to balance microbial P limitation with salinization, microorganisms transfer more energy from the microbial CUE to extracellular enzyme production, and this was the mechanism underlying the trade-off. Microorganisms were also limited by C in the tidal wetlands. However, as the increasing belowground biomass alleviated microbial C limitation with salinization, no relationship was observed between microbial C limitation and CUE. Future C and nutrient models aimed to simulate tidal wetland ecosystem responses to salinization will benefit from the inclusion of trade-off between microbial CUE and microbial P limitation for more accurate prediction.

Incorporation of uncertainty to improve projections of tidal wetland elevation and carbon accumulation with sea-level rise.

Understanding the rates and patterns of tidal wetland elevation changes relative to sea-level is essential for understanding the extent of potential wetland loss over the coming years. Using an enhanced and more flexible modeling framework of an ecosystem model (WARMER-2), we explored sea-level rise (SLR) impacts on wetland elevations and carbon sequestration rates through 2100 by considering plant community transitions, salinity effects on productivity, and changes in sediment availability. We incorporated local experimental results for plant productivity relative to inundation and salinity into a species transition model, as well as site-level estimates of organic matter decomposition. The revised modeling framework includes an improved calibration scheme that more accurately reconstructs soil profiles and incorporates parameter uncertainty through Monte Carlo simulations. Using WARMER-2, we evaluated elevation change in three tidal wetlands in the San Francisco Bay Estuary, CA, USA along an estuarine tidal and salinity gradient with varying scenarios of SLR, salinization, and changes in sediment availability. We also tested the sensitivity of marsh elevation and carbon accumulation rates to different plant productivity functions. Wetland elevation at all three sites was sensitive to changes in sediment availability, but sites with greater initial elevations or space for upland transgression persisted longer under higher SLR rates than sites at lower elevations. Using a multi-species wetland vegetation transition model for organic matter contribution to accretion, WARMER-2 projected increased elevations relative to sea levels (resilience) and higher rates of carbon accumulation when compared with projections assuming no future change in vegetation with SLR. A threshold analysis revealed that all three wetland sites were likely to eventually transition to an unvegetated state with SLR rates above 7 mm/yr. Our results show the utility in incorporating additional estuary-specific parameters to bolster confidence in model projections. The new WARMER-2 modeling framework is widely applicable to other tidal wetland ecosystems and can assist in teasing apart important drivers of wetland elevation change under SLR.

Plant genotype determines biomass response to flooding frequency in tidal wetlands

Abstract. The persistence of tidal wetland ecosystems like salt marshes is threatened by human interventions and climate change. In particular, the threat of accelerated sea level rise (SLR) has increasingly gained the attention of the scientific community recently. However, studies investigating the effect of SLR on plants and vertical marsh accretion are usually restricted to the species or community level and do not consider phenotypic plasticity or genetic diversity. To investigate the response of genotypes within the same salt-marsh species to SLR, we used two known genotypes of Elymus athericus (Link) Kerguélen (low-marsh and high-marsh genotypes). In a factorial marsh organ experiment we exposed both genotypes to different flooding frequencies and quantified plant growth parameters. With increasing flooding frequency, the low-marsh genotype showed higher aboveground biomass production compared to the high-marsh genotype. Additionally, the low-marsh genotype generally formed longer rhizomes, shoots and leaves, regardless of flooding frequency. Belowground biomass of both genotypes decreased with increasing flooding frequency. We conclude that the low-marsh genotype is better adapted to higher flooding frequencies through its ability to allocate resources from below- to aboveground biomass. Given the strong control of plant biomass production on salt-marsh accretion, we argue that these findings yield important implications for our understanding of ecosystem resilience to SLR as well as plant species distribution in salt marshes.

Rhizosphere effect and its associated soil-microbe interactions drive iron fraction dynamics in tidal wetland soils

It is becoming increasingly clear that plants can affect iron (Fe) dynamics in tidal wetland soils, but whether this is rhizosphere effect-dependent remains unclear. To assess rhizosphere effects on soil Fe cycling, in-situ rhizosphere and bulk soil samples (0–60-cm) were collected from a tidal wetland across plant growth stages (regreening, shooting, and senescence). Changes in Fe fractions, the abundance of Fe-oxidizing/reducing bacteria (16S rRNA gene), root morphology traits, and soil and porewater geochemistry were examined. Overall, the rhizosphere effect decreased soil pH but increased the concentrations of dissolved organic carbon (DOC), porewater Fe2+, and bicarbonates (HCO3−). Both Fe-oxidizing and Fe-reducing bacteria were more enriched in the rhizosphere than those in the bulk soil. The rhizosphere effect increased the concentrations of amorphous and crystalline Fe(III), and also enhanced the proportion of amorphous Fe(III). The rhizosphere had higher concentrations of non-sulfidic ferrous iron [Fe(II)] but lower concentrations of ferrous sulfide (FeS) and pyrites (FeS2) than those in bulk soils, suggesting that the rhizosphere effect favors microbial Fe(III) reduction but suppresses microbial sulfate reduction. Moreover, the rhizosphere amorphous Fe(III) levels changed following the patterns of root porosity, which attained peak values at the root tips. The abundance of Fe-reducing bacteria was controlled by both DOC and amorphous Fe(III) concentrations, which were relatively higher during the regreening and shooting stages than those during the senescence stage. Taken together, our findings highlight that the rhizosphere effect transfer Fe from the bulk soil to the rhizosphere and especially redirects it from FeS associations to microbially-mediated Fe redox cycling. This rapid Fe redox cycling could be responsible for buffering soils and organisms from sulfide accumulation and stimulate C mineralization in the tidal wetland ecosystem.

Ecosystem services assessment based on emergy accounting in Chongming Island, Eastern China

Abstract Chongming Island, the largest alluvial island in the world, is an ecologically sensitive area. Due to its green space, farmland, estuaries and coastal wetlands and its proximity to the city of Shanghai (45 km, home to 24.2 million people), the island supports important agricultural and fisheries economies. This paper carries out an evaluation of the ecosystem services (ES) on Chongming Island, Shanghai, based on the emergy analysis method, identifying the service supply and flow between ecosystems and urban area. Results show that from the ecosystem-type perspective, the tidal wetland ecosystem provides the most service to Chongming Island, accounting for 45.2% ES emergy in 2012, followed by the agricultural ecosystem (34.5%) and the freshwater wetland ecosystem (6.3%). From ecosystem service-type perspective, water supply, flood storage and aquatic product supply are the main emergy outputs of the wetland ecosystem and account for 51.1%, 17.6% and 25.2% of the emergy, respectively. Food supply is the main emergy of the cropland ecosystem output and accounts for 58% of the emergy. Organic matter production and water retention are the main services provided by the forest ecosystem, accounting for 33.6% and 30.0% of the total emergy respectively. Based on the systematic emergy dynamic analysis, on the one hand, the wetland and forest ecosystems played more significant roles in water supply and retention while the cropland ecosystem had a less important role in food supply from 2002 to 2012. On the other hand, the urban ecosystem has gradually transformed from a positive to a passive participant in the role of supplier and user for ecosystem services. Finally, policy options are proposed to promote land use planning and restore/maintain ecosystem services.

Vegetation Development in a Tidal Marsh Restoration Project during a Historic Drought: A Remote Sensing Approach

Tidal wetland restoration efforts can be challenging to monitor in the field due to unstable local conditions and poor site access. However, understanding how restored systems evolve over time is essential for future management of their ecological benefits, many of which are related to vegetation dynamics. Physical attributes such as elevation and distance to channel play crucial roles in governing vegetation expansion in developing tidal wetlands. However, in Mediterranean ecosystems, drought years, wet years and their resulting influence on salinity levels may also play a crucial role in determining the trajectory of restoration projects, but the influence of weather variability on restoration outcomes is not well understood. Here, we use object-based image analysis (OBIA) and change analysis of the high-resolution IKONOS and WorldView-2 satellite imagery to explore whether mean annual rates of change from mudflat to vegetation are lower during drought years with higher salinity (2011-2015) compared to years with lower salinity (2009-2011) at a developing restoration site in California’s San Francisco Bay. We found that vegetation increased at a mean rate of 1979 m2/year during California’s historic drought, 10.4 times slower than the rate of 20580 m2/year between 2009 and 2011 when the state was not in drought. Vegetation was significantly concentrated in areas in closer to channel edges, where salinity stress is ameliorated, and the magnitude of the effect increased in the 2015 image. In our image analysis, we found that different distributions of water, mud and algae between years led to different segmentation settings for each set of images, highlighting the need for more robust and reproducible OBIA strategies in complex wetlands. Our results demonstrate that adaptive monitoring efforts in variable climates should take into account the influence of weather on tidal wetland ecosystems, and that high-resolution remote sensing can be an effective means of assessing these dynamics.

Challenges and Directions for the Advancement of Estuarine Ecosystem Science

Estuarine ecosystem ecology is a dynamic field of study that has historically focused on a spectrum of compelling research topics, and here we present a series of perspectives on the major challenges to be overcome and key research questions to be addressed toward making progress over the coming decades. The challenges we identify include (1) maintaining and improving spatially distributed time-series datasets, (2) maximizing innovation by harnessing new technologies, (3) resuscitating experimental ecosystem research for estuaries, (4) integrating diagnostic ecological models into ecosystem research, and (5) improving basic science by linking it to applied research. We also raise a number of key research questions for the field, including (1) how does food web function respond to changing climate and nutrients, (2) what are likely trajectories of ecosystem recovery in response to restoration, (3) how does climate alter seasonality of estuarine ecosystem processes, (4) how do estuaries affect the global carbon budget and what are key feedbacks, and (5) how will tidal wetland ecosystems respond to sea level rise and climate change? Looking ahead, we envision that the field of estuarine ecosystem ecology will continue to build upon its rich tradition to address fundamental research questions with an expanded toolkit and enlightened perspective to focus basic science on the knowledge needs of society.

Tidal Channel Diatom Assemblages Reflect within Wetland Environmental Conditions and Land Use at Multiple Scales

We characterized regional patterns of the tidal channel benthic diatom community and examined the relative importance of local wetland and surrounding landscape level factors measured at multiple scales in structuring this assemblage. Surrounding land cover was characterized at the 100, 250, 1,000 m, and watershed buffer scales. Tidal channel benthic diatom communities were characterized by high species richness, abundance of rare species, and an abundance of species characterized as meso-eutraphentic and eutraphentic. The number of species per site ranged between 21 and 60 (mean ± standard deviation 43.5 ± 9.4). Abundant and frequently occurring taxa included Planothidium delicatulum, Navicula gregaria, and Amphora coffeaeformis. The tidal channel benthic diatom community was most strongly correlated with variables related to human disturbance at all scales surrounding the wetland and not with any tidal channel water quality parameter, including salinity. Furthermore, developed and impervious surface land covers within the 100 and 250 m buffers were more strongly correlated with the diatom assemblage than these covers at larger spatial scales. Species richness and Shannon diversity index were both negatively correlated with the amount of wetland and mudflat surrounding the sites. Of secondary importance in structuring the diatom assemblage were sediment nitrogen and phosphorus concentrations in wetlands immediately surrounding the tidal channels. The sensitivity of the tidal creek benthic diatom assemblage to both wetland and landscape level factors indicates that it might be a useful bioindicator of human disturbance to tidal wetland ecosystems.

Bottom-up control regulates patterns of fish connectivity and assemblage structure in coastal wetlands

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 500:175-186 (2014) - DOI: https://doi.org/10.3354/meps10671 Bottom-up control regulates patterns of fish connectivity and assemblage structure in coastal wetlands Ben Davis*, Carlo Mattone, Marcus Sheaves Centre for Tropical Water & Aquatic Ecosystem Research, Estuary & Tidal Wetland Ecosystems Research Group, School of Marine & Tropical Biology, James Cook University, Townsville, Queensland 4811, Australia *Corresponding author: benjamin.davis@my.jcu.edu.au ABSTRACT: We examined the potential for patterns in invertebrate prey distribution to act as a key driver of fish distribution across a coastal wetland system. Seascape and metacommunity approaches recognise that faunal assemblages in coastal and freshwater systems are structured by responses to multi-scale connectivity and local environmental conditions. However, we currently have a poor understanding of how different groups of aquatic organisms affect each other’s distribution. Most fish in freshwater and coastal wetland systems feed predominantly on benthic invertebrates and zooplankton. To investigate the extent to which these invertebrate taxa exert control over fish distribution, we sampled fish, benthic invertebrate and zooplankton assemblages across 13 inter-connected pools on a salt-marsh in North Queensland, Australia. We found strong and inter-annually consistent spatial concordances among the 3 faunal components, characterised by higher densities of benthic invertebrates and zooplankton in pools at lower elevations on the salt-marsh—reflected by high densities of planktivorous and benthivorous fish, and lower densities of benthic invertebrates and zooplankton in pools at higher elevations—reflected by dominance of fish species trophically de-coupled from these taxa (detritivores, insectivores, and herbivores). Further supporting the idea of trophic linkages, the 2 most invertebrate-rich pools also harboured the greatest densities of benthivorous and zooplanktivorous fish, which in turn attracted the wetland piscivores Lates calcarifer and Megalops cyprinoides. This is indicative of bottom-up forcing acting across 3 trophic levels, a process that is likely facilitated by the frequent tidal connections among pools, which allows for regular redistribution of fish. Prey availability should be considered as a key component of the spatial ecology processes that shape fish assemblages across coastal and freshwater wetland systems. KEY WORDS: Seascape · Metacommunity · Nursery grounds · Estuary · Barramundi · Predator–prey · Biotic interactions · Tidal wetland · Food availability · Food web Full text in pdf format Erratum PreviousNextCite this article as: Davis B, Mattone C, Sheaves M (2014) Bottom-up control regulates patterns of fish connectivity and assemblage structure in coastal wetlands. Mar Ecol Prog Ser 500:175-186. https://doi.org/10.3354/meps10671 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 500. Online publication date: March 17, 2014 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2014 Inter-Research.

Use of geomorphic, hydrologic, and nitrogen mass balance data to model ecosystem nitrate retention in tidal freshwater wetlands

Abstract. Geomorphic characteristics have been used as scaling parameters to predict water and other fluxes in many systems. In this study, we combined geomorphic analysis with in-situ mass balance studies of nitrate retention (NR) to evaluate which geomorphic scaling parameters best predicted NR in a tidal freshwater wetland ecosystem. Geomorphic characteristics were measured for 267 individual marshes that constitute the freshwater tidal wetland ecosystem of the Patuxent River, Maryland. Nitrate retention was determined from mass balance measurements conducted at the inlets of marshes of varying size (671, 5705, and 536 873 m2) over a period of several years. Mass balance measurements indicate that NR is proportional to total water flux over the tidal cycle. Relationships between estimated tidal prism (calculated water volume) for spring tides and various geomorphic parameters (marsh area, total channel length, and inlet width) were defined using measurements from air photos and compared to field data. From these data, NR equations were determined for each geomorphic parameter, and used to estimate NR for all marshes in the ecosystem for a reference spring (high) tide. The resulting ecosystem NR estimates were evaluated for (a) accuracy and completeness of geomorphic data, (b) relationship between the geomorphic parameters and hydrologic flux, and (c) the ability to adapt the geomorphic parameter to varying tidal conditions. This analysis indicated that inlet width data were the most complete and provided the best estimate of ecosystem nitrate retention. Predictions based on marsh area were significantly lower than the inlet width-based predictions. Cumulative probability distributions of nitrate retention indicate that the largest 3–4% of the marshes retained half of the total nitrate for the ecosystem.

Geographic Information Systems used to describe the link between the risk of Ross River virus infection and proximity to the Leschenault estuary, WA

To investigate the relationship between risk of Ross River virus (RRV) infection and proximity to mosquito-breeding habitat surrounding a tidal wetland ecosystem in south-west Australia. Geographic information systems (GIS) were used to spatially map cases of RRV disease in the Leschenault region between July 1995 and June 1996. Half kilometre buffer zones were constructed around the Leschenault Estuary and associated waterways; RRV disease case counts were calculated for each zone. Different relationships between RRV disease incidence and proximity to saltmarsh mosquito habitat were observed east of the Leschenault Estuary compared with an urban region to the south. Disease incidence showed a decreasing trend away from eastern margins of the Estuary, particularly for the first 2 km. In the urban region, RRV disease risk was low close to the Estuary, but increased further out and remained steady across the remainder of that region. The findings support an increased risk of contracting RRV disease for people residing close to eastern margins of the Leschenault Estuary. This study highlights how historical data combined with GIS can improve understanding of the epidemiology of RRV disease. This has a valuable role in assessing the risk of mosquito-borne disease for land-use planning.

闽江河口不同河段芦苇湿地土壤碳氮磷生态化学计量学特征

Ecological stoichiometry is the study of the balance of energy and multiple chemical elements.Generally,this perspective examines the causes and consequences of elemental imbalances between resources,producers,and consumers in the environment.C,N and P are key elements controlling organism growth.However,the relative needs of the elements are poorly quantified,and dependencies between elements are not well investigated.These three elements are strongly coupled in their biochemical functioning.Furthermore,the ecological stoichiometry of C,N and P is the indication for organic carbon decomposition and nutrition limit. The element ratios in wetlands,especially for the estuarine wetlands,appear to be more variable than other ecosystems worldwide.Moreover,the studies on soil C,N and P stoichiometry have not been thoroughly studied.In fact,soil as the carrier of organisms and elements plays very important roles.Therefore,studies on C,N and P ecological stoichiometry of wetland soils will be favorable to clarify the available of nutrition and the cycle and balance of C,N and P. An amount of approximately 18,000 km of coastline in China is covered by an estimated 12,000 km2 of tidal estuary wetlands.These tidal wetlands are generally rich in animal and plant biodiversity and appear to have important biogeochemical roles within the entire estuary ecosystem.One of these important tidal wetland ecosystems is found within the Minjiang River estuary in southeast China,which is located at the transition of mid-and southern subtropical climate zones in China. Phragmites australis is the dominant species in Minjiang River estuarine wetland and distributes everywhere from upper reach to lower river.Here we chose the Youxizhou wetland,Bianfuzhou wetland and Shanyutan wetland as the study areas and examined the ecological stoichiometric characteristics of wetland soils in different river reaches and their indication.In upper reach,the values of soil C/N,C/P,N/P(0—60 cm) of P.australis wetland were 36.5—51.3,43.0—93.6 and 0.8—2.3,with averages of 44.1,66.9 and 1.6,respectively.In middle reach,the values of soil C/N,C/P,N/P(0—60 cm) were 15.8—21.7,28.0—72.2 and 1.6—4.2,with averages of 17.6,45.7 and 2.6,respectively.In lower reach,the values of soil C/N,C/P,N/P(0—60 cm) were 13.5—19.8,63.6—125.4 and 4.2—6.3,with averages of 16.4,90.5 and 5.5,respectively.C/N,C/P and N/P ratios appeared various tendencies among wetlands in different reaches.Soil C/N ratios were in the order of upper reachmiddle reachlower reach,C/P ratios were in the order of lower river upper rivermiddle river,while N/P ratios were in the order of lower reachmiddle reachupper reach.The variation of C/N,C/P,N/P ratios in soil profile of single reach was smaller than that among different reaches.Soil water and silt contents were the key factors controlling the change of C/N,C/P,N/P ratios of wetland soils in different reaches.Soil C/N and N/P ratios were preferable indication for anaerobic carbon decomposition.

闽江河口潮汐湿地二氧化碳和甲烷排放化学计量比

PDF HTML阅读 XML下载 导出引用 引用提醒 闽江河口潮汐湿地二氧化碳和甲烷排放化学计量比 DOI: 10.5846/stxb201107151052 作者: 作者单位: 福建师范大学湿润亚热带生态－地理过程省部共建教育部重点实验室,福建师范大学湿润亚热带生态－地理过程省部共建教育部重点实验室,福建师范大学湿润亚热带生态－地理过程省部共建教育部重点实验室,福州市金桥高级中学 作者简介: 通讯作者: 中图分类号: 基金项目: 国家自然科学基金资助项目(31000209; 40671174);福建省公益类研究所专项 (2011R1037-5);福建省教育厅资助项目(JB11030);福建师范大学优秀青年骨干教师培养基金(fjsdky2012007) Stoichiometry of carbon dioxide and methane emissions in Minjiang River estuarine tidal wetland Author: Affiliation: Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education,Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education,Key Laboratory of Humid Sub-tropical Eco-geographical Process of Ministry of Education,Fuzhou Jinqiao Senior Middle School Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:为了阐明河口潮汐湿地碳源温室气体排放的化学计量比特征,对闽江河口潮汐湿地二氧化碳和甲烷排放进行了测定与分析。结果表明:芦苇湿地和短叶茳芏湿地二氧化碳与甲烷排放均呈现正相关;涨潮前、涨落潮过程和落潮后芦苇湿地和短叶茳芏湿地CO2∶CH4月平均值分别为55.4和185.0,96.3和305.5,68.7和648.6,3个过程芦苇湿地和短叶茳芏湿地CO2∶CH4差异均不显著(P>0.05),2种植物湿地CO2∶CH4对潮汐的响应并不一致,但均在涨潮前表现为最低;涨潮前、涨落潮过程和落潮后均表现为芦苇湿地CO2∶CH4低于短叶茳芏湿地(P<0.05);河口潮汐湿地CO2∶CH4为空间变异性>时间变异性,潮汐、植物和温度均对CO2∶CH4的变化具有一定的调节作用。 Abstract:Gas exchange between soils and the atmosphere is an important contributory factor to global climate change due to increasing release of greenhouse gases (N2O, CO2, CH4, etc.). CO2 and CH4 are the principal gases. Wetland is one of the important ecosystems for carbon cycle, especially for the CO2 and CH4 exchange. Wetland ecosystem emits CO2 and CH4 through aerobic and anaerobic respiration and fixes carbon (CO2) through photosynthesis. So the ratio of CO2 to CH4 is important to reveal the greenhouse gas emissions of carbon sources and to mediate their emissions. An amount of approximately 18,000 km of coastline in China is covered by an estimated 12,000 km2 of tidal estuary wetlands. These tidal wetlands are generally rich in animal and plant diversity and appear to have important biogeochemical roles within the entire estuary ecosystem. One of these important tidal wetland ecosystems is found within the Minjiang River estuary in southeast China, which is located at the transition of mid- and southern subtropical climate zones in China. Vegetation and tide are two important factors influencing the biochemistry process of estuarine wetland and thereby controlling CO2 and CH4 emissions. Most of the previous studies have been showed that plants act as a key control on the spatial variability of CO2 and CH4 emissions due to their influence on the formation and transportation. Tidal systems are likely to be affected by tidal processes including time of inundation and salinity. Flooding is known to reduce CO2 and CH4 emissions, probably by blocking the pathway of CO2 and CH4 release. However, the effects of vegetation and tide on CO2∶CH4 values are not clear. This study was conducted in the Shanyutan wetland (119°34'12″-119°40'40″E, 26°00'36″ -26°03'426″N), which is the largest tidal wetland (nearly 3120 hm2) in the Minjiang River estuary. The climate is warm and wet, with a mean annual temperature of 19.6℃ and a mean annual precipitation of 1346 mm. The Shanyutan wetland is belt-shaped. The sediment surface at the study site is submerged for 3-3.5 hours during each tidal inundation. The vegetation mainly occupies two zones: a 150-200 m wide Scirpus lacustris zone close to the sea, and a 150 m wide Phragmites australis and Cyperus malaccensis var. brevifolius zone which extends from the intertidal zone to near the bank. Here we examined the stoichiometry characteristics of carbon-source greenhouse gas emissions in Minjiang River estuarine tidal wetland. The results showed that the emission fluxes of CO2 in both Phragmites australis wetland and Cyperus malaccensis var. brevifolius wetland were positively correlated with the emission fluxes of CH4. The monthly average CO2∶CH4 values in P. australis wetland and C. malaccensis wetland were 55.4 and 185.0, 96.3 and 305.5, and 68.7 and 648.6 in the stages of before high tide, during tidal fluctuation, and after ebb, respectively. But the monthly average CO2∶CH4 values were not significantly different in the three different stages for both P. australis wetland and C. malaccensis wetland (P>0.05). The lowest CO2∶CH4 values were found before high tide in both wetlands but with different responses to tide. The monthly average CO2∶CH4 values in the three stages for P. australis wetland were lower than those for C. malaccensis wetland (P<0.05). Our results indicated that the spatial variation of CO2∶CH4 values was greater than the temporal one in estuarine tidal wetland, and tide, vegetation type and temperature were the key factors controlling the variation of CO2∶CH4. 参考文献 相似文献 引证文献