Urban Estuary Research Articles

Relative contribution of the presence of an estuarine dam and land reclamation to sediment dynamics of the Nakdong Estuary

The Nakdong Estuary of Korea is a dramatic example of an urban estuary that has been heavily developed with the installation of two estuarine dams and approximately 17 km2 of tidal flat reclamation. This study aims to understand the relative contribution of the different physical alterations by implementing four model simulations of the COAWST modeling system: (1) present condition, (2) pre-estuarine dam construction, (3) pre-tidal flat reclamation, (4) both pre-estuarine dam construction and pre-reclamation. In Cases 2 and 4, the model grid was modified to extend the Nakdong estuary upriver about 60 km and remove the estuarine dam. In Cases 3 and 4, the model grid was modified to restore the reclaimed tidal flats. All simulations shared the same initial conditions, boundary conditions, and forcing. Then, the simulation results for current velocity, suspended sediment concentration (SSC), and deposition were used to estimate the relative contribution of each alteration. The results showed that the annual, depth-averaged currents for the pre-estuarine dam (Case 2) were 80% faster than the present condition but were 10% slower for Case 3 (no land reclamation case). Likewise, the depth-averaged SSC was higher by about 25 mg/L in the estuary for Case 2, but it was reduced by about 9 mg/L for Case 3. The increase of velocity and SSC for Case 2 resulted from the removal of the estuarine dam, which changed both the tidal properties (tidal amplitude was reduced by about 40 cm) and estuarine circulation (factor of 5 reductions in the vertical salinity gradient), while the decrease for Case 3 was induced by the reduction in sediment accommodation space (15% of water volume) without a change in the circulation. These results also revealed that the estuarine dam enhanced deposition more than the land reclamation that showed very little change. The changes in current velocity, SSC, and deposition for Case 4 (no dam/reclamation) were very similar to Case 2. Overall, this study suggests that the influence of the estuarine dam was larger than that of the land reclamation in the altered Nakdong Estuary. Moreover, the combination of estuarine alterations acted to enhance the effects. These findings can serve as analogs that can be applied to other estuaries where various human alterations have occurred.

The screening and prioritization of contaminants of emerging concern in the marine environment based on multiple biological response measures

There is ample evidence that a range of anthropogenic chemicals occur in the aquatic environment, some of which have the potential to cause harm. Contaminants of Emerging Concern (CECs) are a subset of anthropogenic compounds that are poorly characterized in terms of effects and occurrences, and that are generally unregulated. Due to the sheer number of chemicals used, it is necessary to identify and prioritize those that may cause biological impacts.A key challenge of doing so is the lack of traditional ecotoxicological information. The utilization of in vitro exposure-response studies or benchmarks based on in vivo data can provide a basis for developing threshold values for evaluation of potential impacts. There are challenges, including understanding the accuracy and range of application for modeled measures and translating in vitro response information from receptor models to apical endpoints. Despite this, the use of multiple lines of evidence increases the range of available information, and supports a weight-of-evidence approach to inform the screening and prioritization of CECs in the environment.The objective of this work is to perform an evaluation of CECs detected in an urban estuary, and to identify those that are most likely to elicit a biological response. Monitoring data from marine water, wastewater, and fish and shellfish tissue samples from 17 different campaigns combined with multiple biological response measures were compared with appropriate threshold values. CECs were categorized based on their potential to elicit a biological response; the uncertainty, based on consistency of lines of evidence, was also evaluated. Two-hundred-fifteen CECs were detected. Fifty-seven were identified as High Priority (likely to cause a biological effect), and 84 as Watch List (potential to cause biological effects). Due to the extent of the monitoring and range of the lines of evidence, this approach and results are applicable to other urbanized estuarine systems.

EDNA metabarcoding reveals shifts in sediment eukaryote communities in a metal contaminated estuary

Metal contamination is a global issue impacting biodiversity in urbanised estuaries. Traditional methods to assess biodiversity are time consuming, costly and often exclude small or cryptic organisms due to difficulties with morphological identification. Metabarcoding approaches have been increasingly recognised for their utility in monitoring, however studies have focused on freshwater and marine systems despite the ecological significance of estuaries. We targeted estuarine eukaryote communities within the sediments of Australia's largest urbanised estuary, where a history of industrial activity has resulted in a metal contamination gradient. We identified specific eukaryote families with significant correlations with bioavailable metal concentrations, indicating sensitivity or tolerance to specific metals. While polychaete families Terebellidae and Syllidae demonstrated tolerance to the contamination gradient, members of the meio- and microfaunal communities including diatoms, dinoflagellates and nematodes displayed sensitivities. These may have high value as indicators but are frequently missed in traditional surveys due to sampling limitations.

The carrying capacity of estuarine mangroves in maintaining the coastal urban environmental health of Southeast Sulawesi, Indonesia

This study aims to elucidate the carrying capacity of estuarine mangroves in Southeast Sulawesi, to maintain environmental health of its coastal cities. The concentrations of mercury (Hg), Copper (Cu), Manganese (Mn), Lead (Pb), Zinc (Zn), and Nickel (Ni) were analyzed in sediments and mangrove tissues samples from Kendari bay and Tinanggea estuaries. This was followed by the determination of translocation and bioaccumulation factors, as well as the total accumulation of heavy metals on a landscape level. The results showed that the sediment in Kendari Bay had higher heavy metal concentrations than in Tinanggea, indicating the anthropogenic impact of the highly populated city of Kendari. Moreover, the roots and stems of mangroves had higher heavy metal concentrations than the leaves. Overall, the Bioconcentration Factors (BCF) of Hg, Cu, Mn, Pb and Zn metals were >1, indicating that estuarine mangroves have a higher phytoremediation capacity for heavy metals. Estuarine mangrove biomass also enables the high accumulation of heavy metals in both Kendari bay and Tinanggea, signifying the greater phytoremediation potential of urban estuarine mangroves. Based on these findings, the study supports the conservation and management of mangroves in urban estuaries to maintain the environmental health of coastal cities.

Understanding the role of microhabitats in intertidal rock pools to guide future eco-engineering designs

Intertidal rock pools support diverse assemblages. While there is much research on the importance of rock pools in supporting mobile diversity on rocky shores, there is limited knowledge regarding the role of physical features (microhabitats) within these habitats. Understanding the features of pools that support diversity is crucial to conserve and potentially mimic these important intertidal habitats in restoration projects. Here, we classified and quantified the types of physical features, hereafter “microhabitats” (overhangs and pits), within rock pools at different locations in and around a highly urbanised estuary, Sydney Harbour, Australia. The use of different microhabitats within rock pools by mobile macro-invertebrates was also examined in one location. We surveyed natural rock pools in summer (2 times) and winter (2 times) at seven sites: two sites from each of the inner and outer zones of Sydney Harbour, and three sites along the open coast of Sydney. We found that the type and size of microhabitats within pools decreased from the coastal towards inner harbour sites. Along the open coast, the richness of mobile taxa increased in rock pools with overhangs or pits. Only rock pools with overhangs had increased mobile abundances, likely driven by the gastropod Nerita melanotragus. Several species occurred in greater frequency in pools with overhangs. There was no effect of pits on abundances. This survey suggests that some microhabitats may play an important role in the diversity and abundance of mobile macro-invertebrates in rock pools. A detailed understanding of the local and regional scales of microhabitats should be used to inform eco-engineering of intertidal foreshores.

Chlorophyll dynamics from Sentinel-3 using an optimized algorithm for enhanced ecological monitoring in complex urban estuarine waters

Urban estuaries are dynamic environments that hold high ecological and economic value. Yet, their optical complexity hinders accurate satellite retrievals of important biogeochemical variables, such as chlorophyll-a (Chl-a) biomass. Approaches based on a limited number of satellite spectral bands often fail to capture seasonal transitions and sharp spatial gradients in estuarine Chl-a concentrations, inhibiting integration of satellite data into water quality monitoring and conservation programs. We propose a novel approach that utilizes the wide range of spectral information captured by the Ocean and Land Color Instrument (OLCI) to retrieve estuarine Chl-a. To validate our approach, we used measurements in Long Island Sound (LIS), a highly urbanized estuary increasingly susceptible to anthropogenic stressors and climate change. Hyperspectral remote sensing reflectance (Rrs) and Chl-a data representing the spatiotemporal diversity of LIS were used to assess the ideal atmospheric correction approach for OLCI and develop a multi-spectral multiple linear regression (MS-MLR) Chl-a algorithm. POLYMER derived Rrs proved to be the preferred atmospheric correction approach. Evaluation of MS-MLR performance in retrieving Chl-a with in situ Rrs showed good agreement with field measurements. Application to OLCI-retrieved Rrs showed significant improvement (20%-30%) in common error metrics relative to other algorithms assessed. The MS-MLR approach successfully captured seasonal cycles and spatial gradients in Chl-a concentration. Application of this method to urban estuaries and coasts enables accurate, high resolution Chl-a observations at the ecosystem scale and across a range of conditions, as needed for conservation and ecosystem management efforts.

Transitions in nitrogen and organic matter form and concentration correspond to bacterial population dynamics in a hypoxic urban estuary.

The online version contains supplementary material available at 10.1007/s10533-023-01021-2.

Land use and COVID-19 lockdowns influence debris composition and abundance in stormwater drains

Stormwater drains act as a pathway for anthropogenic debris from land to sea, particularly in urbanised estuaries where impervious surfaces expedite the process. Debris type and abundance in stormwater drains may vary due to land use and human activity, and knowledge of this variation is necessary to manage the growing threat of debris. Surveys of stormwater debris can inform targeted reduction and remediation efforts by intercepting and identifying pollutants near their source. We surveyed replicate stormwater gross pollutant traps across four land use zones (city centre, shopping centre, transportation hub, industrial precinct) before and during COVID-19 measures to assess the effects of changing human activities. Gross pollutant traps were installed in 120 drains in Greater Melbourne, Australia, and citizen scientists trained by Tangaroa Blue Foundation weighed and classified debris at 6-week intervals between October 2019 and October 2020. Four survey cycles were conducted before lockdowns were implemented, then another four during lockdowns. COVID-19 lockdowns and patterns of debris type and abundance across land use revealed how changes in human activity might impact the flow of debris. Cigarette butts were the most abundant macro debris (>5 mm) item in every survey cycle, regardless of lockdowns. Industrial land use zones had the lowest macro debris counts but contained over 90 % of the micro debris (1–5 mm). The amount of total macro debris decreased during lockdowns, however the most abundant and problematic debris items such as cigarettes and single-use plastics did not decrease as much as might be expected from the concomitant reductions in human activity. Occupational health and safety items, such as masks and gloves, increased (144 %) during COVID-19 lockdowns. Micro debris counts did not change in industrial zones during lockdowns, suggesting that workplace interventions may be necessary to reduce this debris leakage. Tracing the pathway of debris from source to sea can inform reduction and long-term management strategies.

Addressing climate change and development pressures in an urban estuary through habitat restoration planning

Native habitats in Florida face dual pressures at the land-sea interface from urban development and sea-level rise. To address these pressures, restoration practitioners require robust tools that identify reasonable goals given historical land use trends, current status of native habitats, and anticipated future impacts from coastal stressors. A restoration framework for native habitats was created for the Tampa Bay watershed that identifies current opportunities and establishes short-term (2030) targets and long-term (2050) goals. The approach was informed through a three-decade habitat change analysis and over 40 years of habitat restoration projects in the region. Although significant gains in subtidal habitats have been observed, expansion of mangroves into salt marshes and loss of native upland habitats to development highlights the need to target these locations for restoration. The long-term loss of potentially restorable lands to both coastal and upland development further underscores the diminishing restoration opportunities in the watershed. The established targets and goals identified habitats to maintain at their present level (e.g., mangroves) and those that require additional progress (e.g., oyster bars) based on past trends and an expected level of effort given the restoration history of the region. The new approach also accounts for the future effects of sea-level rise, climate change, and watershed development by prioritizing native coastal habitats relative to subtidal or upland areas. Maps were created to identify the restoration opportunities where practitioners could focus efforts to achieve the targets and goals, with methods for repeatable analyses also available using an open source workflow.

Source apportionment of polychlorinated dibenzo-p-dioxins and dibenzofurans in the sediments of an urban estuary.

Polychlorinated dibenzo-p-dioxins and dibenzofurans in the sediments of aquatic systems are a persistent global problem that poses serious health risks. Identifying the sources of dioxins in natural water systems and the extent of their contributions to observed sediment concentrations is important from a health advisory and mitigation perspective. This paper proposes novel distribution-based qualitative and quantitative methods as source apportionment techniques and alternatives to conventional source attribution methods. Using sampled data, air, runoff, industrial effluent, and industrial paper and pulp wastes were identified as four distinct dioxin contributors to concentrations found in the sediments of the test bed region: the Houston Ship Channel-San Jacinto River-Galveston Bay (HSC-SJR-GB) estuarine system that also includes 2 Superfund sites with dioxin contamination. Two qualitative methods, the Kullback-Leibler divergence (K-L divergence) and the Bhattacharya measure (BM), and a quantitative method, the L2 norm, were used to investigate the spatial and temporal sourcing patterns of dioxins in the system sediments. The results indicated a global contribution from air and runoff sources across the estuarine system and over time with more localized impacts of the Superfund sites and the industrial sources. The results using the developed methodologies were compared with the output from the more conventional positive matrix factorization (PMF) method. Statistically significant correlations were observed among source contributions from the proposed methods and the PMF method, with Spearman's ρ ranging between - 0.596 to - 0.963 and 0.652 to 0.719, demonstrating the utility of the sourcing approaches used in the study. Additionally, the proposed methods were found to be rigorous in terms of elucidating spatial and temporal changes in the sourcing of dioxin to the estuary, indicating their suitability for use for other contaminants and other estuarine systems.

Rethinking Estuary Urbanism—Preparing Australian Estuary Cities for Changes to Come in the Climate and Biodiversity Emergency

This research investigates the challenges and opportunities of urban estuaries exposed to spatial, urban, and environmental shifts exacerbated by climate change, ecological disturbances, and population growth, taking the cities of Perth, Western Australia and Newcastle, New South Wales, as case studies. Approaching the design of estuary cities in the Climate Century demands a form of estuary urbanism and new paradigms in design, which embrace the constant presence of water. Water becomes the instrument of change to re-think the design of the city and its relationship with the non-built environment since the climate crisis is also a water crisis. Adaptation and mitigation strategies are still emerging fields in design and planning disciplines. Design disciplines can strongly contribute to generating site-specific climate-adaptative responses while re-establishing the connection between built and natural environments, improving ecological balance and spatial quality, and promoting well-being and cultural values. The methodology involves both analytical and projective-explorative methods promoting a site-specific approach, working across scales and disciplines to understand urban estuaries within larger catchments and as complex hydrological and ecological systems. A fundamental goal is the creation of site-specific design strategies to operate in low to medium-density precincts, leveraging water and nature as design tools to improve urban resilience and liveability. There is capacity here to establish design methods and principles that inform future practices through urbanism responding to dynamic ecological and water systems and the unpredictability effects of climate change.

Hiding in Plain Sight: Characterization of Aeromonas Species Isolated from a Recreational Estuary Reveals the Carriage and Putative Dissemination of Resistance Genes.

Antimicrobial resistance (AMR) has become one of the greatest challenges worldwide, hampering the treatment of a plethora of infections. Indeed, the AMR crisis poses a threat to the achievement of the United Nations' Sustainable Development Goals and, due to its multisectoral character, a holistic approach is needed to tackle this issue. Thus, the investigation of environments beyond the clinic is of utmost importance. Here, we investigated thirteen strains of antimicrobial-resistant Aeromonas isolated from an urban estuary in Brazil. Most strains carried at least one antimicrobial resistance gene and 11 carried at least one heavy metal resistance gene. Noteworthy, four (30.7%) strains carried the blaKPC gene, coding for a carbapenemase. In particular, the whole-genome sequence of Aeromonas hydrophila strain 34SFC-3 was determined, revealing not only the presence of antimicrobial and heavy metal resistance genes but also a versatile virulome repertoire. Mobile genetic elements, including insertion sequences, transposons, integrative conjugative elements, and an IncQ1 plasmid were also detected. Considering the ubiquity of Aeromonas species, their genetic promiscuity, pathogenicity, and intrinsic features to endure environmental stress, our findings reinforce the concept that A. hydrophila truly is a "Jack of all trades'' that should not be overlooked under the One Health perspective.

Plastic waste in surface waters of an urban estuary

Context Plastic pollution is a threat to ecosystems and is a global problem. Aims We evaluated the spatio-temporal degradation stage of plastic waste found in surface waters (<1 m) of the Capibaribe River estuary. Methods The analysed waste items were sampled in three distinct areas within the estuary, namely, upper, middle and lower regions. Key results In total, 381 items of debris were classified as macroplastics (≤25 mm), with soft fragments (83.9%) and hard fragments (4.9%) being predominant. Advanced degradation stage occurred throughout the estuary (90.5%). A concentration of 1757 microplastics (<2.2 mm) was found predominant in the upper and middle regions. Soft fragments corresponded to the most abundant type (69%). Conclusion In the middle estuary, a plastic hotspot was observed, caused by the flood tide flow, river flow and the flow of a tributary, forming a convergence cell that helps retain plastic debris for long periods. Implications Identifying the origin, sources and how the hydrodynamic characteristics influence the distribution of plastic debris along the estuary is relevant because it will help decision-makers to develop municipal and state action plans for the recovery of this ecosystem.

Piers are hotspots for benthic marine debris in an urbanised estuary.

Records of anthropogenic marine debris and the threats it poses are increasing worldwide, yet we know relatively little about the distribution of benthic debris. The seafloor is the final destination for a large proportion of debris due to the degradation and sinking of items. A more detailed understanding of debris distributions in hotspots such as urbanised estuaries can help decision makers target management and remediation activities. We selected sites frequented by fishers and boaters in Sydney Harbour, an urbanised estuary, to investigate the impacts of recreational activities on debris abundance. The aim of this study was to examine variation in macro debris (>5mm in diameter) type and abundance at two habitat types (piers and non-piers). We chose five locations at various distances from the estuary mouth. In each location SCUBA teams performed fixed transects at two sites, one under a pier and one over nearby soft-sediment habitat. Debris was recovered by the divers and brought to the surface for classification and disposal. Surveys were repeated multiple times at each location between November 2019 and February 2020, recording a total of 2803 debris items over 36 survey events. Overall, piers had more than ten times the debris abundance of soft-sediment sites, and much higher proportion of debris types related to recreational fishing. Over half of the debris items in this study were plastic (65%), and approximately 70% of the total debris was classified as related to recreational fishing. This trait was most prominent in debris at sites closest to the estuary mouth, likely reflecting increased fishing activity in this area. This study indicates that policy makers and community groups in urbanised estuaries should focus monitoring, reduction, and remediation efforts near artificial structures such as piers, and that public awareness campaigns should target the behaviour of recreational users of these structures.

Anthropogenic Impacts on Organophosphate Ester Loads to an Urban Estuary in South China

Due to the lack of regular monitoring networks and practical assessment criteria for contaminants of emerging concern in rivers, it is challenging to quantify the influences of human activities on their occurrence and ecological impacts on the estuarine environment. To address this issue, herein, organophosphate esters (OPEs) were selected and tested in the Pearl River Estuary (PRE), which is an urban estuary surrounded by a megalopolis (the Greater Bay Area) in South China. A field-based investigation was conducted on the riverine outlets of the PRE by considering tidal and seasonal variations coupled with models to improve the assessment of human-derived stress on this urban estuary. The results indicated that the occurrence of OPEs was strongly influenced by emissions from land-based sources and hydrological conditions with minor influences from biogeochemical processes. Approximately 45,200 kg year–1 of ∑12OPE was discharged from the eight major riverine outlets to the PRE in 2020–2021. Tributyl phosphate and tris(2-chloroethyl) phosphate with the highest environmental stress index are the two priority OPEs, necessitating further monitoring and control measures in this estuary. The present study demonstrates that the urbanized riverine outlets face greater environmental stress and lower resilience to OPE pollution than other less-urbanized outlets.

High-resolution multivariate analysis of the hydrochemical signature of water corridors in the upper Río de la Plata estuary, Argentina

Major world river-estuaries integrate the hydrochemical characteristics of the basin with specific signatures which are maintained until complete mixing or discharge to the sea. The chemical signature of distinct water masses and the anthropogenic impact in the Upper Río de la Plata estuary (RLP) were evaluated by high-resolution continuous monitoring (i.e. every 200 m) of conductivity, turbidity, pH, temperature, chlorophyll a and coloured dissolved organic matter (CDOM), discrete analysis of suspended particulate matter (SPM) grain size composition combined with multivariate analysis (K-means clustering, Principal Component Analysis). The characteristic signatures of main RLP tributaries such as the Paraná River, yielding higher conductivity, CDOM, turbidity and coarser SPM, and the Uruguay River, with clearer, more eutrophic waters enriched in very fine SPM, were maintained 60 km seaward from the estuary head. Across the river, three water corridors with distinct signatures and variable widths (3–20 km) were identified reflecting the transition from Paraná to Uruguay River waters. Multivariate techniques also allowed the identification of a polluted coastal corridor (higher conductivity and CDOM and lower turbidity) impacted by wastewater discharges from the metropolitan Buenos Aires and La Plata cities extending 100 km seaward. The combined strategy of high-resolution monitoring, discrete sampling and multivariate techniques was a useful tool to identify water masses, corridors of flow and anthropogenic sources in a heavily urbanized estuary.

Effects of PAHs on meiofauna from three estuaries with different levels of urbanization in the South Atlantic.

Estuarine environments are suggested to be the final receivers of human pollution and are impacted by surrounding urbanization and compounds carried by the river waters that flow from the continent. Polycyclic aromatic hydrocarbons (PAHs) are among the contaminants that can reach estuaries and can directly affect marine conservation, being considered highly deleterious to organisms living in these environments. This research investigated the meiofauna of three estuaries exposed to different levels of urbanization and consequently different levels of PAH concentrations, in order to assess how these compounds and environmental factors affect the distribution, structure and diversity of these interstitial invertebrates. A total of 15 major meiofauna groups were identified, with Nematoda being the dominant taxon (74.64%), followed by Copepoda (9.55%) and Polychaeta (8.56%). It was possible to observe significant differences in all diversity indices studied in the estuaries. With the exception of average density, the diversity indices (richness, Shannon index and evenness) were higher in the reference estuary, Goiana estuarine system (GES). On the other hand, the Timbó estuarine system (TES) had the lowest Shannon index value and richness, while the Capibaribe estuarine system (CES) had the lowest evenness value. The latter two estuaries (TES and CES) presented intermediate and high levels of urbanization, respectively. The ecological quality assessment (EcoQ) in the studied estuaries was classified from Poor to Moderate and the estuary with the lowest demographic density in its surroundings, GES, showed a better ecological quality (Moderate EcoQ). A significant distance-based multivariate linear modelling regression (DistLM) was observed between the environmental variables and the density of the meiobenthic community, where PAHs and pH were the main contributors to organism variation. The sediments were characterized by predominance of very fine sand and silt-clay in the most polluted environments, while the control site environment (GES) was dominated by medium grains. The highest concentrations of PAHs were found in the most urbanized estuaries, and directly affected the structure of the interstitial benthic community. The metrics used in the present study proved to be adequate for assessing the environmental quality of the investigated estuaries.

Contamination status and associated ecological risk assessment of heavy metals in different wetland sediments from an urbanized estuarine ecosystem

Sediment samples of different wetland types (saltmarsh, mangrove, tidal pool, mudflat and sandflat) from an urbanized estuary were analyzed to evaluate the contamination level and ecological risks of five heavy metals (Pb, Fe, Zn, Ni and Cr). The findings showed that the mean concentration (mg/kg) of heavy metals followed the order of Fe>Zn>Ni>Pb>Cr, while Pb and Fe concentrations exceeded the recommended guidelines. Heavy metals levels were highest in saltmarsh and mudflats. Contamination assessment indices e.g., contamination factor (CF), degree of contamination (CD), enrichment factor (EF), and geo-accumulation index (Igeo) revealed that the studied wetlands had low to moderate levels of pollution, meaning these sites receive medium levels of anthropogenic contamination compared with background values. For some of the studied metals, such as Pb, Zn, Fe, and Ni, the EF value was >1 in certain types of wetland, indicating anthropogenic sources, while Cr was <1 indicating natural sources. The pollution load index (PLI) value was determined to be <1, indicating perfection of soil, and was in the following order: mudflat> saltmarsh> tidal pool> mangrove > sandflat. The ecological risk (RI) value was the highest for saltmarsh and the lowest for sandflats. However, the RI value for Cr, Zn, Ni, and Pb was <30 suggesting that these metals pose a low risk in the local ecosystem. Cluster analysis (CA), principal component analysis (PCA), and Pearson's correlation specified that anthropogenic sources of metals.

Site prioritization and the reproduction of inequity in the restoration of Biscayne Bay

AbstractThe restoration of urban estuaries is challenging due to the complexity of prioritizing sites in a context of social and biophysical unevenness. Site prioritization and selection are crucial components of ecological success and equity in restoration. In many cases, site prioritization is conducted according to simple opportunity or political expediency, but this needs to be investigated further in local contexts, with accompanying analysis of the impacts on urban environmental equity. Using a critical physical geography framework, I explore site selection processes in the restoration of Biscayne Bay through case studies of two urban streams. I use multiple data types to present an integrated perspective on urban restoration priority and the social context that produces restoration siting decisions. I find that the logics of restoration site selection in the Biscayne Bay watershed have produced ecologically questionable decisions and inequitable outcomes. Therefore, I argue that restoration decision making needs to include environmental justice criteria.

Assessment of metal contamination in an urbanized estuary (Atlantic Ocean) using crabs as biomonitors: A multiple biomarker approach

Estuarine environments, which are complex and sensitive coastal system, and are the final receptacle of several human wastes. Consequently, biomonitoring contaminants, such as metals, within these environments and developing scientific-based tools to conserve them have become particularly importat in recent years. Therefore, in the present study, we determined the levels of certain metals (Cd, Cu, Pb, Zn, Mn, Ni, Cr and Fe) both in sediments and in a key ecological benthic species, the burrowing crab Neohelice granulata, in sites of the Bahía Blanca estuary (SW Atlantic Ocean) with different anthropogenic impacts. We combined these records with geochemical indices and enzymatic and non-enzymatic biochemical biomarkers as early warning signals of contamination and damage to establish an integrated metal contamination profile. Our results indicated that some metals like Cu moderately contaminate the estuary and that the primary input of metals in this area is due to malfunctioning sewage discharges. Crabs exhibited the following pattern of metal accumulation: Fe ≥ Cu > Zn > Mn > Ni > Cd. Pb and Cr were under the method detection limit, and Cu was probably bioaccumulated from sediments. Metal concentrations showed significant differences according to the sites and seasons (p > 0.05) and not strictly to the crab gender. Besides, a similar pattern was observed for biomarkers, and the integrated biomarker response allowed establishing different oxidative stress patterns, according not only to human impacts but also to the seasonal physiological needs of this species and environmental endpoints (salinity, temperature, and pH). This work demonstrates that environmental factors also affect the metal influx in crabs and the activity of biomarkers beyond the source and fate of these elements. This information is vital for future integrated monitoring programs.