Land-water Interface Research Articles

Enhancing Climate Resiliency Through Improving Ecosystem Services in Shoreline Municipalities – Lessons from Canada

The accelerated impacts of climate change in waterfront areas and the proven inefficacy of the aging hardened shoreline infrastructure have driven shoreline management practices to evolve toward the enhancement of ecosystem services at the land-water interface. Gaining momentum as an adaptive approach in regenerative projects, living shorelines are comprised of natural ecosystem components used in combination or in place of traditional hard engineering methods to provide coastal protective services and erosion mitigation. The success of living shorelines in protecting shoreline property and ecosystem integrity varies based on the biogeomorphology and hydrology of the region and is also heavily reliant on social acceptance of the chosen approach and best practice for implementation. The relatively lower lifecycle cost and associated co-benefits of living shorelines have well positioned them as a promising alternative approach in theory. There are, however, gaps in regional long-term datasets and evidence-based guidelines. This research provides an overview of the underlying geopolitical readiness for integrating nature-based solutions in climate adaptation strategies within shoreline municipalities based on a comprehensive literature review complimented by expert interviews. The synthesized data can inform decisions for minimizing the destructive effects of traditional shoreline erosion prevention approaches and encourage successful implementation of solutions that offer ecological, health, social, and economic benefits.

Advancements in amphibious robot navigation through wheeled odometer uncertainty extension and distributed information fusion

The advancement and safeguarding of the water-land interface region is of paramount importance, and amphibious robots with the capacity for autonomous operation can play a pivotal role in this domain. However, the inability of the majority of reliable navigation sensors to adapt to the water-land interface environment presents a significant challenge for amphibious robots, as obtaining positional information is crucial for autonomous operation. To address this issue, we have proposed a positioning and navigation framework, designated as NAWR (Navigation Algorithm for Amphibious Wheeled Robots), with the objective of enhancing the navigation capabilities of amphibious robots. Firstly, a method for representing the odometer's confidence based on a simplified wheel-terrain interaction model has been developed. This method quantitatively assesses the reliability of each odometer by estimating the slip rate. Secondly, we have introduced an improved split covariance intersection filter (I-SCIF), which maximizes the utilization of navigation information sources to enhance the accuracy of positional estimation. Finally, we will integrate these two methods to form the NAWR framework and validate the effectiveness of the proposed methods through multiple robot field trials. The results from both field trials and ablation tests collectively demonstrate that the modules and overall approach within the NAWR framework effectively enhance the navigation capabilities of amphibious robots.

Accounting for plume rise of aircraft emissions and shoreline meteorology enhances AERMOD’s description of concentrations measured around Los Angeles airport

ABSTRACT The Aviation Environmental Design Tool (AEDT), developed by the FAA, is used to analyze the environmental impact of airport activities on air quality and noise near airports. AEDT incorporates AERMOD to estimate concentrations resulting from aircraft emissions, which possess horizontal momentum as well as buoyancy. The current version (v23132) of AERMOD incorporates plume dynamics associated with such emissions as an ALPHA option. AERMET, AERMOD’s meteorological processor does not account for the meteorology of the land-water interface that is likely to be important for airports located on the shorelines of lakes or oceans. An approach to include these effects in AERMOD was previously developed. This study examines the impact of including plume rise and shoreline effects in AERMOD by evaluating model estimates of NOX and SO2 with corresponding measurements made during the Los Angeles Airport Air Quality Source Apportionment Study (AQSAS) in the winter and summer of 2012. The performance statistics resulting from this model evaluation suggest that the inclusion of plume rise of aircraft emissions and shoreline effects on meteorological inputs is likely to improve AERMOD’s ability to estimate the impact of airport emissions on surrounding air quality. Implications: Because airport emissions, particularly those from aircraft, affect local air quality, the National Environmental Policy Act (NEPA) requires the use of dispersion models such as AERMOD to assess compliance of air quality regulations when potential expansions of airport activity are planned. The current regulatory version of AERMOD does not include aircraft-specific plume rise and shoreline-related meteorological processes, which affect the dispersion of airport emissions. The preliminary evidences presented in our previous work suggest that the incorporation of these effects will enhance AERMOD’s ability to estimate NOX and SO2 concentrations associated with airport emissions. These enhancements are beneficial not only for policy-making and regulatory compliance but also for promoting sustainable development near airports and protecting public health.

Coastal Waterfront Transformations, Fishing Structures, and Sustainable Tourism

Fishing is a socioeconomic activity with highly visible impacts on the water–land interface of cities. Tourism, the number and type of visitors, and attractions depend on the image and experience of coastal places. How has fishing evolved over time? How has planning attempted to influence and adapt the land use and built-up structures, leading to the activity’s development and commercialization? It utilizes three pairwise cases to analyze the land use transformations associated with fishing activities in cities and some of their most important structures, with impacts on tourism activities such as fish markets, waterfront and pier restaurants, festival marketplaces, and recreational facilities. The three pairwise cases are in three different regions of the world (i.e., North America, Southern Europe, and the Pacific Rim). New Bedford, Massachusetts (USA) and Figueira da Foz (Portugal) are utilized to analyze the land use transformations associated with fishing activities in cities. Fish markets in Tokyo (Japan) and Sydney (Australia) are analyzed to study built-up structures where fish are commercialized. Finally, the last pairwise waterfronts consisting of San Francisco (California, USA) and Fremantle (Western Australia) are examined to understand their fish consumption. The research design and methods comprised in loco visits to the six case studies; discussions with stakeholders; visual documentation and analysis; and a distillation of implications for public policy. The findings demonstrate that more attention needs to be paid to land use changes, the co-existence of working harbor operations with recreational uses, the accessibility to those areas, the “publicness” of the areas in terms of public spaces and other coastal amenities, and the impacts of mixed-use developments on adjacent residential areas. Many waterfronts have suffered radical changes and ought to be made more accessible, authentic, and livable not through the effects of nature or markets alone but with planning and urban design interventions.

Shifting lakefronts: Alternative waterfront politics in Wuhan

ABSTRACT The transformation of lakefronts from spaces of privatization and contamination to vibrant public areas signifies a significant urban shift in Wuhan over the past 2 decades. This article explores a shift toward integrating bottom-up participatory approaches to sustainable environmental management with the top-down planning system amid this profound urban transition. By examining the unintended planning consequences and civic actions across Sha Lake and Dong Lake, this study uncovers a complex urban process marked by conflicts over waste management, property rights, and cultural identity issues at the water-land interface. In this process, new forms of civic participation emerged in Wuhan’s environmental management in the digital age, despite the lack of official participatory mechanisms. The study identifies parallels in the formalization of community engagements between Wuhan and other locales, notwithstanding China’s continued dominance of centralized governance, as middle-class activists increasingly play active roles in environmental management projects, utilizing skills, networks, and dedication.

Eco-hydrological processes regulate lake riparian soil organic matter under dryness stress

As transitional zone between terrestrial and aquatic ecosystems, the soil properties of riparian zones are deeply influenced by the eco-hydrological conditions of lakes. However, with the increasing frequent drought events caused by climate change, the response of riparian soil organic matter (SOM) dynamics to the eco-hydrological process of lakes under dryness stress is unclear. In this study, we utilized the field research, indoor experiments, ecoenzymatic stoichiometry model and data analysis to identify whether riparian SOM and enzyme activity were affected by dryness stress and determine the feedback relationship between soil biochemical properties and lake eco-hydrological processes. The results showed that lake dryness stress reduced the non-vegetated riparian soil quality (the mean Carbon Pool Management Index decreased by 18 % and 6 % for water–land interface (WL) and bare land (BL), respectively), and the humification degree and molecular weight of the riparian soil dissolved organic matter (DOM) (with E2/E3 and E3/E4 value of WL 6.1 and 1.9 times higher than main lake sediment), which was not conducive to soil carbon storage. In addition, lake dryness stress reduced the C-hydrolytic enzyme activity and soil enzyme stoichiometry. The vector and Vector-TER analysis suggested the riparian soil was C and N limitation of the microbial community (vector length of 2.05 ± 0.57 and vector angle of 30.10° ± 7.70°), and dryness had reduced the limitations to some extent. Most notably, we combined structural equation model (SEM) analysis and found that lake dryness stress affects riparian soil organic carbon (SOC) dynamics by significantly affecting microbial biomass carbon (MBC) and soil pH. Finally, the response of riparian zone to eco-hydrological condition under climate change should receive further attention, which can effectively deepen our understanding of the carbon water cycle mechanism in riparian soil under changing environments.

Microbial community response to hydrocarbon exposure in iron oxide mats: an environmental study.

Hydrocarbon pollution is a widespread issue in both groundwater and surface-water systems; however, research on remediation at the interface of these two systems is limited. This interface is the oxic-anoxic boundary, where hydrocarbon pollutant from contaminated groundwaters flows into surface waters and iron mats are formed by microaerophilic iron-oxidizing bacteria. Iron mats are highly chemically adsorptive and host a diverse community of microbes. To elucidate the effect of hydrocarbon exposure on iron mat geochemistry and microbial community structure and function, we sampled iron mats both upstream and downstream from a leaking underground storage tank. Hydrocarbon-exposed iron mats had significantly higher concentrations of oxidized iron and significantly lower dissolved organic carbon and total dissolved phosphate than unexposed iron mats. A strong negative correlation between dissolved phosphate and benzene was observed in the hydrocarbon-exposed iron mats and water samples. There were positive correlations between iron and other hydrocarbons with benzene in the hydrocarbon-exposed iron mats, which was unique from water samples. The hydrocarbon-exposed iron mats represented two types, flocculent and seep, which had significantly different concentrations of iron, hydrocarbons, and phosphate, indicating that iron mat is also an important context in studies of freshwater mats. Using constrained ordination, we found the best predictors for community structure to be dissolved oxygen, pH, and benzene. Alpha diversity and evenness were significantly lower in hydrocarbon-exposed iron mats than unexposed mats. Using 16S rDNA amplicon sequences, we found evidence of three putative nitrate-reducing iron-oxidizing taxa in microaerophile-dominated iron mats (Azospira, Paracoccus, and Thermomonas). 16S rDNA amplicons also indicated the presence of taxa that are associated with hydrocarbon degradation. Benzene remediation-associated genes were found using metagenomic analysis both in exposed and unexposed iron mats. Furthermore, the results indicated that season (summer vs. spring) exacerbates the negative effect of hydrocarbon exposure on community diversity and evenness and led to the increased abundance of numerous OTUs. This study represents the first of its kind to attempt to understand how contaminant exposure, specifically hydrocarbons, influences the geochemistry and microbial community of freshwater iron mats and further develops our understanding of hydrocarbon remediation at the land-water interface.

Condors scavenge on fish at the land–water interface in the Andean foothill of southern Bolivia

AbstractThere is very little information on Andean condors scavenging on fish. Here we report five events of condors feeding on fish carrion in the Bolivian Chaco Serrano in three consecutive years. In 2019, 2020, and 2021, condors were observed feeding on discarded fish from local fishermen, 3 km west of Villa Montes, in the ‘El Angosto’ section of the Pilcomayo River. Fishing, mainly for sábalo (Prochilodus lineatus), is the most important economic activity in that part of the Pilcomayo basin and its discards explain fish carrion availability there, while driving scavengers to feed on this resource. We believe that fish carrion abundance, the intensity of intra‐ and interspecific competition for access to carrion, and overall carrion availability hierarchically influence the fact that condors feed on fish, something we will investigate later based on the observations reported here. From a conservation perspective, the main consequence of scavengers feeding on fish from the Pilcomayo is that they could be getting heavy metal poisoning. Heavy metal poisoning is a serious threat with widely known negative effects for wildlife. Our observations should serve to promote comprehensive bio‐monitoring of the Pilcomayo basin, using approaches such as One Health, and emphasizing the importance of coexistence between humans and the rest of biodiversity, with the Andean Condor as the flagship species.

Study of the Ecosystem Service Value Gradient at the Land–Water Interface Zone of the Xijiang River Mainstem

The ecosystem service value (ESV) gradient-evolution pattern of a river basin’s land and water-intertwined zones has a variety of ecosystem service values, such as biodiversity conservation, water conservation, water purification, etc. The study of the ecosystem service value (ESV) gradient-evolution pattern of a river basin’s land and water-intertwined zones will provide a scientific basis for the construction and protection of the ecological security pattern of the river basins. In this study, we combined the unit area equivalent factor method and geographically weighted regression (GWR) model to classify and analyze the gradient change pattern of ESV upstream, downstream, and along the river of the Guangdong mainstream section of the Xijiang River in China, and the conclusions are as follows: (1) The corresponding ESV share of each land use type was in the following order: water bodies > broad-leaved forest > artificial wetland > scrub > paddy field > coniferous forest > natural wetland > grassland. The level of each type of ESV does not depend entirely on the size of the area but is determined by the ecosystem service functions it can provide and the level of ESV per unit area; (2) the relationship between land use types along both sides of the river in the Guangdong section of the Xijiang River Basin shows a tendency to shift from water ecosystems to terrestrial ecosystems, and the ESV gradually decreases with the increase in distance from the water. (3) The upstream to the downstream area showed a trend of changing from terrestrial ecosystems to aquatic ecosystems, such as broad-leaved forests, scrublands, water bodies, artificial wetlands, etc., and the mean land ESV showed a general trend of undulating change and decline with the reduction in the distance from the downstream area. (4) Natural factors, such as the topography and geomorphology of the basin and the socio-economic factors of power consumption, influence the spatial distribution characteristics of the ESV in the region; among them, socio-economic factors, such as total power consumption, industrial exhaust gas emissions, industrial wastewater emissions, etc., in the economically developed areas of the Xijiang River Basin are the determinants of the changes in ESV, which are generated by human living and production activities, and these indirectly affect the magnitude of the ESV by influencing the factors of temperature and gas.

The Siege of Enniskillen Castle, 1594: An Object Lesson in Combat Across the Land-Water Interface

The U.S. Marine Corps spent the years between the world wars developing a doctrine of opposed landings from the sea in an arena where the ocean provided the only maneuver space, but the opposed amphibious operation is not the province of ocean-borne amphibious assaults alone. The land-water interface impacts warfare well inland from the coast, and much can be learned from the application of riverine and lacustrine amphibious assaults found in history. One such example is the siege of Enniskillen Castle in Ireland in 1594. English operations at Enniskillen demonstrated the value of coordinated waterborne and land-based forces at the tactical level. Considering English lacustrine operations in the Irish Nine Years’ War (1593–1603) and U.S. riverine warfare experiences in the American Civil War and Vietnam War can inform Marine planners as they develop the tactics, techniques, and procedures of the Marine Littoral Regiments.

Spatial Interpolation of Soil Temperature and Water Content in the Land-Water Interface Using Artificial Intelligence

The distributed measured data in large regions and remote locations, along with a need to estimate climatic data for point sites where no data have been recorded, has encouraged the implementation of spatial interpolation techniques. Recently, the increasing use of artificial intelligence has become a promising alternative to conventional deterministic algorithms for spatial interpolation. The present study aims to evaluate some machine learning-based algorithms against conventional strategies for interpolating soil temperature data from a region in southeast Canada with an area of 1000 km by 550 km. The radial basis function neural networks (RBFN) and the deep learning approach were used to estimate soil temperature along a railroad after the spline deterministic spatial interpolation method failed to interpolate gridded soil temperature data on the desired locations. The spline method showed weaknesses in interpolating soil temperature data in areas with sudden changes. This limitation did not improve even by increasing the spline nonlinearity. Although both radial basis function neural networks and the deep learning approach had successful performances in interpolating soil temperature data even in sharp transition areas, deep learning outperformed the former method with a normalized RMSE of 9.0% against 16.2% and an R-squared of 89.2% against 53.8%. This finding was confirmed in the same investigation on soil water content.

Simulation of high-frequency dissolved oxygen dynamics in a shallow estuary, the Corsica River, Chesapeake Bay

Understanding shallow water biogeochemical dynamics is a challenge in coastal regions, due to the presence of highly variable land-water interface fluxes, tight coupling with sediment processes, tidal dynamics, and diurnal variability in biogeochemical processes. While the deployment of continuous monitoring devices has improved our understanding of high-frequency (12 - 24 hours) variability and spatial heterogeneity in shallow regions, mechanistic modeling of these dynamics has lagged behind conceptual and empirical models. The inherent complexity of shallow water systems is represented in the Corsica River estuary, a small basin within the Chesapeake Bay ecosystem, where abundant monitoring data have been collected from long-term monitoring stations, continuous monitoring sensors, synoptic sensor surveys, and measurements of sediment-water fluxes. A state-of-the-art modeling system, the Semi-implicit Cross-scale Hydroscience Integrated System Model (SCHISM), was applied to the Corsica domain with a high-resolution grid and nutrient loads from the most recent version of the Chesapeake Bay watershed model. The Corsica SCHISM model reproduced observed high-frequency variability in dissolved oxygen, as well as seasonal variability in chlorophyll-a and sediment-water fluxes. Time-series signal analyses using Empirical Model Decomposition and spectral analysis revealed that the diurnal and M2 tide frequencies are the dominant high-frequency modes and physical transport contributes a larger share to dissolved oxygen budgets than biogeochemical processes on an hourly time scale. Heterogeneity and patchiness in dissolved oxygen resulting from phytoplankton distributions and geometry-driven eddies amplify the physical transport effect, and on longer time scales oxygen is controlled more by photosynthesis and respiration. Our simulation demonstrates that interactions among physical and biological dynamics generate complex high-frequency variability in water quality and non-linear reposes to nutrient loading and environmental forcing in shallow water systems.

A novel bathymetry signal photon extraction algorithm for photon-counting LiDAR based on adaptive elliptical neighborhood

Ice Cloud and Land Elevation Satellite-2 (ICESat-2) uses a 532-nm laser with a strong seawater penetration ability, and can provide reliable water depth information for sea areas that in situ bathymetric data are lacking. However, because of the complexity of underwater terrain, background noise, optical signal attenuation in water, and other factors, there are still some obstacles to accurately extract bathymetry photons using ICESat-2 data This paper proposes an novel bathymetry signal extraction algorithm based on an adaptive elliptical neighborhood window. The direction-adaptive elliptical neighborhood strategy ensures the directionality and continuity of signal extraction. The size-adaptive neighborhood strategy satisfies the demand for extraction of both shallow, dense signals and deep, sparse signals. The kernel density estimation (KDE) based strategy for sea surface elevation extraction and above-water signal separation makes it possible to determine the sea surface elevation accurately while correctly separating the above-water photons. Four study areas with different environmental conditions in the Xisha Islands, the Bahamas, and the Gulf of Aden were selected, and the key results are as follows. (1) For a water-land interface area with dense noise, the proposed algorithm can effectively reduce the impact of land and accurately eliminate noise photons in shallow water. (2) For an extremely sparse signal in a deep-water area, which is difficult to process using classical algorithms, the proposed algorithm can accurately extract signal photons in water approximately 50 m deep while effectively extracting the dense signal photons in shallow water. (3) In the extraction results obtained using this algorithm, the signal strip has better continuity and smoothness than the classical algorithm and therefore can portray the seafloor terrain more completely. As the in situ water depth confirms, the overall mean absolute error (MAE) and mean relative error (MRE) of the water depth information extracted by the proposed algorithm are 0.79 m and 7.54%, respectively, which indicate high reliability.

VOC and Trace Gas Measurements and Ozone Chemistry Over the Chesapeake Bay During OWLETS-2, 2018

The Ozone Water-Land Environmental Transition Study, 2018 (OWLETS-2) measured total non-methane hydrocarbons (TNMHC) and EPA PAMS Volatile Organic Compounds (VOCs) on an island site in the northern Chesapeake Bay 2.1 and 3.4 times greater in concentration, respectively, than simultaneous measurements at a land site just 13 km away across the land-water interface. Many PAMS VOCs had larger concentrations at the island site despite lower NEI emissions over the water, but most of the difference comprised species generally consistent with gasoline vapor or exhaust. Sharp chemical differences were observed between the island and mainland and the immediate air ~300 m above the water surface observed by airplane. Ozone formation potential over land was driven by propene and isoprene but toluene and hexane were dominant over the water with little isoprene observed. VOC concentrations over the water were noted to increase diurnally with an inverse pattern to land resulting in increasing NOx sensitivity over the water. Total reactive nitrogen was lower over the water than the nearby land site, but reservoir compounds (NOz) were greater. Ozone production rates were generally slow (~5 ppb hr−1) both at the surface and aloft over the water, even during periods of high ozone (>70 ppbv) at the water surface. However, specific events showed rapid ozone production >40 ppb hr−1 at the water’s surface during situations with high VOCs and sufficient NOx. VOC and photochemistry patterns at the island site were driven by marine sources south of the island, implicating marine traffic, and indicate ozone abatement strategies over land may not be similarly applicable to ozone over the water.

Assessment of biological community in riparian zone contaminated by PAHs: Linking source apportionment to biodiversity

Riparian zone, an important land-water interface, plays an essential role in maintaining the ecological health of rivers, whereas the effects of Polycyclic aromatic hydrocarbons (PAHs) on the health of biological communities in riparian groundwater remain undetermined. To understand the responses of multiple communities to environmental variables, the distribution and ecosystem risk of 16 PAHs have been investigated in the Beiluo River, China. The distribution of multiple communities in riparian groundwater was investigated by environmental DNA metabarcoding, including 16S rRNA, 18S rRNA, and COI gene sequencing for bacteria, microbial eukaryotes (including algae, fungi, and protozoa), and metazoan, respectively, followed by correlation analysis between multiple communities and PAH contamination levels. The concentration of PAHs in the Beiluo River ranged largely from 35.32 to 728.59 ng/L. Here, the Shannon's diversity index of bacteria (Firmicutes) decreased possibly due to the occurrence of Pyrene, which mainly derives from coal and biomass combustion. Furthermore, the reduced richness of fungi (Ascomycota, Basidiomycota) and algae (Chlorophyta, Chrysophyceae) can be attributed to the presence of medium molecular weight (MMW) PAHs (Pyrene, Benz(a)anthracene, Chrysene), and low molecular weight (LMW) PAHs (Naphthalene, Fluorene, Phenanthrene). The richness and Shannon's diversity index of metazoan (Arthropoda) were promoted owing to MMW PAHs (Chrysene, Fluoranthene) generated from coal and biomass combustion and traffic emission. The ecological risk of PAHs in the groundwater environment of the Beiluo River was characterized as low to medium, where LMW and MMW PAHs posed higher risk than the high molecular weight (HMW) compounds. Overall, this study provides insights into the structures of riparian multi-biological communities altered by PAHs.

Protist Diversity and Metabolic Strategy in Freshwater Lakes Are Shaped by Trophic State and Watershed Land Use on a Continental Scale.

ABSTRACTProtists play key roles in aquatic food webs as primary producers, predators, nutrient recyclers, and symbionts. However, a comprehensive view of protist diversity in freshwaters has been challenged by the immense environmental heterogeneity among lakes worldwide. We assessed protist diversity in the surface waters of 366 freshwater lakes across a north temperate to subarctic range covering nearly 8.4 million km2 of Canada. Sampled lakes represented broad gradients in size, trophic state, and watershed land use. Hypereutrophic lakes contained the least diverse and most distinct protist communities relative to nutrient-poor lakes. Greater taxonomic variation among eutrophic lakes was mainly a product of heterotroph and mixotroph diversity, whereas phototroph assemblages were more similar under high-nutrient conditions. Overall, local physicochemical factors, particularly ion and nutrient concentrations, elicited the strongest responses in community structure, far outweighing the effects of geographic gradients. Despite their contrasting distribution patterns, obligate phototroph and heterotroph turnover was predicted by an overlapping set of environmental factors, while the metabolic plasticity of mixotrophs may have made them less predictable. Notably, protist diversity was associated with variation in watershed soil pH and agricultural crop coverage, pointing to human impact on the land-water interface that has not been previously identified in studies on smaller scales. Our study exposes the importance of both within-lake and external watershed characteristics in explaining protist diversity and biogeography, critical information for further developing an understanding of how freshwater lakes and their watersheds are impacted by anthropogenic stressors.IMPORTANCE Freshwater lakes are experiencing rapid changes under accelerated anthropogenic stress and a warming climate. Microorganisms underpin aquatic food webs, yet little is known about how freshwater microbial communities are responding to human impact. Here, we assessed the diversity of protists and their myriad ecological roles in lakes varying in size across watersheds experiencing a range of land use pressures by leveraging data from a continental-scale survey of Canadian lakes. We found evidence of human impact on protist assemblages through an association with lake trophic state and extending to agricultural activity and soil characteristics in the surrounding watershed. Furthermore, trophic state appeared to explain the distributions of phototrophic and heterotrophic protists in contrasting ways. Our findings highlight the vulnerability of lake ecosystems to increased land use and the importance of assessing terrestrial interfaces to elucidate freshwater ecosystem dynamics.

PCB exposure is associated with reduction of endosymbionts in riparian spider microbiomes

Microbial communities, including endosymbionts, play diverse and critical roles in host biology and reproduction, but contaminant exposure may cause an imbalance in the microbiome composition with subsequent impacts on host health. Here, we examined whether there was a significant alteration of the microbiome community within two taxa of riparian spiders (Tetragnathidae and Araneidae) from a site with historical polychlorinated biphenyl (PCB) contamination in southern Ontario, Canada. Riparian spiders specialize in the predation of adult aquatic insects and, as such, their contaminant levels closely track those of nearby aquatic ecosystems. DNA from whole spiders from sites with either low or high PCB contamination was extracted, and spider microbiota profiled by partial 16S rRNA gene amplicon sequencing. The most prevalent shift in microbial communities we observed was a large reduction in endosymbionts in spiders at the high PCB site. The abundance of endosymbionts at the high PCB site was 63 % and 98 % lower for tetragnathids and araneids, respectively, than at the low PCB site. Overall, this has potential implications for spider reproductive success and food webs, as riparian spiders are critical gatekeepers of energy and material fluxes at the land-water interface.

Landscapes to eco-scapes: prescriptive transitions for urban waterways for an Indian megacity

ABSTRACT Urban wetlands and waterways are vital for a city’s defence, transport, water supply, environment, and culture. However, overuse, environmental stress, and management issues degenerate their condition, particularly in countries with high populations, limited funds, and improper infrastructure. A megacity in eastern India, Kolkata is blessed with two significant rivers, an efficient canal system, and a wetland of international prominence. Unfortunately, various factors disturbed their natural flow, slaying them with pollution, sedimentation, and reduced aquatic biodiversity, thus losing their socio-cultural importance. The paper analyses the interactions and inter-relationships between the city’s main waterways in a comprehensive environmental, socio-economic, and cultural context. It also presents a prescriptive framework for the eco-restoration and management of the city’s waterways. The target-driven strategies comprise the spatio-physical components of land, land-water interface, and water for physical, ecological, and hydro-morphological restoration of these waterways as an urgent step towards urban sustainability and resilience.

Eutrophication Assessment Using Phytodiversity at the Land-Water Interface of Lake Anasagar of Ajmer

Since most of the water, silt, nutrients, and organic inputs from the catchment areas must pass through theland-water interface before reaching the water body, the biota of this zone and the ecosystem processesoperating therein play a significant role in regulating water quality, biodiversity and productivity of inlandwaters. Therefore, this zone can be considered as a biological frame of the aquatic ecosystem. As the effectof pollutants coming from various anthropogenic activities and factors operating on land are morepronounced at the interface, the aquatic flora growing here may be indicative of trophic state of the waterbody. The present study deals with phytoplankton and macrophytes as a criterion for trophic evaluation ofAnasagar- a perennial freshwater lake of Ajmer which is being influenced by a number of anthropogenicactivities on its margin. Human settlements and construction activities in the catchment areas lead todeterioration of the water quality of the lake. The study indicates that rather than physico-chemicalcharacteristics used to classify wetlands under oligo- and eutrophic scales, Phytodiversity is a potent criterionfor trophic evaluation. As a major element of aquatic biota, the algal community often exhibits dramaticchanges in response to different types of pollutants. Hence, the diversity of algal component in the aquaticecosystem serves as a reliable index for biomonitoring of pollution load. Land-water interface is rich inalgal diversity, in all 123 algal species belonging to Cyanophyceae (41), Chlorophyceae (48),Bascillariophyceae (22) and Euglenophyceae (12) were recorded. On the basis of number of algal speciesbelonging to various groups, Nygaard Trophic State Indices were calculated which indicate hypereutrophicstatus of wetland. Wetland plants in land-water interface play an important role in nutrient dynamics. Thecontribution of some dominant macrophytes in nutrient enrichment at the land-water interface was alsoassessed. It was estimated that among the macrophyte species, Azolla pinnata and Trapa bispinosa contributedmaximum to the total nutrient inputs into the lake waters. If these macrophyte species are removed beforedecomposition Starts, nutrient enrichment of the lake may be checked to a large extent. Recently manyinitiatives have been taken to restore Lake Anasagar under National Lake Conservation Program throughinstallation of water treatment plant and by providing aeration in the water body. This will favourablyaffect the biological components including algal flora and macrophytes. Data on the physico-chemicalanalysis state that the water quality is still not improved because inputs of fertilizers and detergents havenot been checked so far.

Effects of COVID-19 lockdown on water quality, microbial extracellular enzyme activity, and sediment-P release in the Ganga River, India.

This study investigates possible improvement in water quality and ecosystem functions in the Ganga River as influenced by COVID-19 lockdown in India. A total of 132 samples were collected during summer-2020 low flow (coinciding COVID-19 lockdown) for water (sub-surface and sediment-water interface) and 132 samples separately for sediment (river bottom and land-water interface) considering 518-km main river stem including three-point sources (one releases urban sewage and the other two add metal-rich industrial effluents) and a pollution-impacted tributary. Parameters such as dissolved oxygen deficit and the concentrations of carbon, nutrients (N and P), and heavy metals were measured in water. Sediment P-release was measured in bottom sediment whereas extracellular enzymes (EE; alkaline phosphatase, FDAase, protease, and β-D-glucosidase) and CO2 emission were measured at land-water interface to evaluate changes in water quality and ecosystem functions. The data comparisons were made with preceding year (2019) measurements. Sediment-P release and the concentrations of carbon, nutrients, and heavy metals declined significantly (p<0.05) in 2020 compared to those recorded in 2019. Unlike the preceding year, we did not observe benthic hypoxia (DO <2.0 mg L−1) in 2020 even at the most polluted site. The EE activities, which declined sharply in the year 2019, showed improvement during the 2020. The stability coefficient and correlative evidences also showed a large improvement in the water quality and functional variables. Positive changes in functional attributes indicated a transient recovery when human perturbations withdrawn. The study suggests that timing the ecosystem recovery windows, as observed here, may help taking management decision to design mitigation actions for rivers to recover from anthropogenic perturbations.