Estuarine Health Research Articles

From land to sea: Environmental DNA is correlated with long-term water quality indicators in an urbanized estuary

Estuaries provide critical ecosystem services, and yet are increasingly under threat from urbanization. Non-invasive approaches to monitor biodiversity resident to or migrating through estuaries is critical to evaluate the holistic health of these ecosystems, often based entirely on water quality. In this study we compared tree of life metabarcoding (ToL-metabarcoding) biodiversity detections with measurements of physico-chemical variables (chlorophyll a, turbidity, total nitrogen, total phosphorous, dissolved oxygen) at eight sites of varying degrees of water quality in the Gold Coast Broadwater Estuary (Queensland, Australia). These sites were ranked according to an adapted Water Quality Index (WQI) score. Here, we detected 787 unique taxa, adding 137 new biodiversity records to the region, mostly micro-organisms such as bacteria, ciliates, diatoms, dinoflagellates, and cryptomonads. Sites with the lowest WQI were characterised by higher turbidity, lower dissolved oxygen, as well as higher total nitrogen and phosphorous, which correlated with an increased diversity of bacteria, ciliates, and green algae. Similarly, the composition of taxa was significantly different between sites with variable WQI values for most taxa but was less apparent for larger vertebrate groups. These findings suggest that rapid ToL-metabarcoding biodiversity detections, particularly for lower order taxonomic groups, can serve as valuable indicators of flora and fauna across the tree of life associated with dynamically shifting estuarine health along urbanized coastlines.

Assessment of Amphibola crenata as a bioindicator of estuarine trace element pollution using biochemical and physiological endpoints

To assess its utility as a bioindicator of estuarine contamination, Amphibola crenata, a pulmonate mud snail, was collected from 17 estuaries in New Zealand. Whole-body soft tissue trace element concentrations were measured via quadrupole inductively coupled plasma mass spectrophotometer (Q-ICP-MS) and were found to be significantly positively correlated with sediment trace element profiles for arsenic, copper and lead. Snails from polluted estuaries generally displayed higher ammonia excretion rates, elevated whole-body soft tissue catalase activity and lipid peroxidation compared to snails from reference sites. Across all sites haemolymph glucose was positively correlated with the tissue burdens of arsenic, copper, nickel and zinc, while haemolymph protein was negatively correlated with arsenic, cadmium and zinc soft tissue concentrations, indicative of altered energy metabolism associated with trace element contamination. Overall, sites were distinguishable by application of the array of measures employed. Our findings suggest that gastropods have significant value as bioindicators of estuarine health.

Ecological impacts of dam construction on epilithic diatom communities in estuaries: A case study of the Korean peninsula

This study, spanning 2016 to 2018, investigated diatom distribution in 324 Korean Peninsula estuaries, emphasizing the ecological impact of artificial dams. Examining environmental and biological variables, we focused on dam construction. OPEN estuaries exhibited higher urban/forest land cover and had more alkaline, saline, conductive, and oxygen-rich water. In CLOSE estuaries, agricultural farmland and nitrogen compound concentrations were higher. Dams in CLOSE estuaries correlated with lower pH, salinity, electrical conductivity, and dissolved oxygen. Regional variations were evident, with WEST OPEN estuaries showing higher salinity, turbidity, chemical oxygen demand, and total phosphorus. SOUTH estuaries displayed intermediate characteristics, while EAST OPEN estuaries had higher dissolved oxygen but lower temperature and turbidity.Diverse epilithic diatoms were identified, with OPEN estuaries displaying greater species richness, primarily dominated by Nitzschia inconspicua Grunow. CLOSE estuaries, conversely, exhibited higher richness with a different subdominant species. Indicator species analysis revealed taxa specific to estuaries and sea areas, with CLOSE ones exhibiting lower salinity and higher nitrogen/phosphorus concentrations. Nitzschia inconspicua dominated all estuaries, but subdominant species varied; N. fonticola (Grunow) Grunow in OPEN, N. paleaceae (Grunow) Grunow in CLOSE. CLOSE estuaries had higher species richness. In the West Sea, turbidity and TP levels affected diatom growth, with dams exacerbating turbidity and potentially disrupting the food chain.Results underscored intricate interactions between dams, land use, and diatom communities, offering foundational data for ecosystem management and biodiversity conservation in Korean Peninsula estuaries. Understanding the ecological consequences of artificial dams on diatom distribution is crucial for preserving estuarine health. Future research is recommended to explore additional factors influencing these ecosystems, particularly focusing on various organisms in West Sea estuaries for effective ecosystem management and conservation.

Evaluating ocean health and restoration success: A comprehensive study of the benthic quality index in the Bilbao estuary

Ocean health is a global concern, and effective protection and restoration of estuaries require robust ecological information and appropriate metrics for comprehensive assessments. This study used 16 years of hard-bottom macroinvertebrate data from the formerly polluted Bilbao estuary to calculate the Benthic Quality Index (BQI). The BQI, based on species sensitivity values derived from richness-disturbance associations, was a valuable tool for evaluating the health of the macroinvertebrate community. Our findings demonstrated the responsiveness of the BQI to both natural and anthropogenic stressors, making it a useful indicator for assessing overall community health. Significant increases in BQI values, averaging 47%, were observed in the central section of the estuary, indicating successful restoration efforts. Furthermore, the BQI values showed a positive correlation with distance from the river mouth, reflecting a gradient of improved health. Notably, the BQI reliance on data rather than species-specific knowledge makes it suitable for assessing benthic community health across large temporal and spatial scales, where ecological information may be limited. In conclusion, the BQI provides a standardized measure of health that facilitates a better understanding of the state of our oceans. Its application in assessing estuarine health, as demonstrated in the Bilbao estuary, underscores its value in conservation and restoration efforts. By utilizing the BQI, we can make informed decisions to protect and restore estuarine ecosystems for the benefit of marine biodiversity and the health of our oceans.

The role of diseases in unifying the health of global estuaries

Establishing a universal indicator of estuary health is an ongoing challenge for coastal ecology that is made more pressing due to the threat that climate change and anthropogenic activity pose to them. Historically, estuarine health was measured through basic physical, chemical, and biological traits, which have been used to routinely monitor estuaries for more than 30 years. However, it is unclear if they are dynamic enough to accurately assess ecosystem health changes driven by the pressures of climate change and anthropogenic activity. Measuring estuarine health indicators and noting incipient indicators relevant to the evolving threats of climate- and anthropogenic-related stressors on estuarine ecosystems is vital for safeguarding them into the future. Monitoring the presence and vitality of disease in estuarine ecosystems may prove to be a significant indicator of estuarine health. Here we review 22 years of literature (354 papers) to identify the role of marine diseases as critical indicators of long-term estuary health compared to traditional methods, with the goal of identifying a key indicator and underlying unifier of other health metrics. As indicators of both general ecosystem health and of multiple other stressors, diseases play a disproportionately significant role in estuary health in the face of climate- and anthropogenic-related stressors. Marine diseases are a unifier of structural and functional estuary health indicators and must be observed and modeled further.

Marsh archive reveals human population history and future implications for estuarine health in Long Island Sound

Coastal marshes are efficient ecosystems providing a multitude of benefits for invertebrates, birds, fish and humans alike. Yet despite these benefits, wetlands are threatened by anthropogenic inputs such as human wastewater which contain high levels of nitrogen (N). Increased nitrogen loads cause eutrophication and hypoxia in estuaries leading to further degradation of these valuable ecosystems that are already stressed by sea level rise and climate change. Policies to protect wetlands via wastewater treatments are reactive rather than proactive and a growing body of research shows that characteristics associated with population health and economic activity can be identified in wastewater. Analysis of a 2-m salt marsh sediment core reveals δN15 signatures indicative of human population rise and connects human impact to ecosystem health. Using key X-ray fluorescence (XRF), pollen, sediment and nitrogen signatures along the core, a robust chronology was produced dating back to 1700. This result was coupled with population data to observe the relationship between δN15 levels and population over three centuries. There is a statistically significant positive correlation between δN15 and population. Other external factors such as federal government policies (regulating clean water) show a clear reduction in this association but the use of synthetic nitrogen fertilizer masks the strength of this relationship. Further research to refine the relationship between population and δN15 could be beneficial in predicting nitrogen loads as human population grows, which in turn would create a proactive system to protect our coastal ecosystems.

Fish as bio-indicator tool for assessing estuarine health

Fish Health Index and Index of Biotic Integrity directly indicates environmental health and was used in our monitoring at Coleroon, Vellar and Uppanar, estuaries in the southeast coast of India. The use of cast nets revealed 104 species of fish that belongs to 69 genera, 44 families and 10 orders. Assessment using fish health index at Coleroon, Vellar and Uppanar estuaries produced scores of 4.8692, 8.4981 and 1.4042 which means Vellar has better health than Coleroon and Uppanar. In addition, 12 metrics were used to produce the index of biotic integrity where total scores varied from 18 to 51. With Vellar achieving higher scores than Coleroon and Uppanar estuary, a Two-way ANOVA was employed to validate the data with significant achievement (P<0.005). Therefore, we can safely associate Coleroon, Vellar and Uppanar with ‘Fair’, ‘Good’ and ‘Very poor’ grades. Also, visual depiction of Vellar demarcates it as pristine in comparison to Coleroon and Uppanar that are subject to impairments along with dominance of omnivorous fishes. Knowledge from this study eases monitoring of important estuaries particularly for food security so that management sustains community livelihood.

Historical data provides context for recent monitoring and demonstrates 100 years of declining estuarine health

ABSTRACT Estuaries are complicated systems to manage effectively, requiring the monitoring of robust environmental indicators to assess health and detect changes. Routine estuarine monitoring programmes in New Zealand have only existed for 30 years at most, but estuaries have been significantly affected by anthropogenic pressures for at least 100 years. We reconstructed long term changes in indicators of estuarine health using historical information from sediment cores and aerial photographs, and combined this information with recent monitoring data. This study is focused on four estuaries in the Waikato region of New Zealand, but the findings are likely applicable elsewhere. Sediment accumulation rates increased by orders of magnitude c. 100 years ago, but mangrove forests only started to rapidly expand c. 50 years ago, which coincided with the intensification of agriculture and urban development, and resultant declines in freshwater quality. Over the past 20 years, state of the environment monitoring shows declines in benthic health at most monitoring sites, as well as continuing sediment accumulation and mangrove expansion in some places. This adds to the weight of evidence that environmental management has not been sufficient to safeguard estuarine health and demonstrates the magnitude of change in these systems over the past 100 years.

Challenges and opportunities for sustaining coastal wetlands and oyster reefs in the southeastern United States

Formed at the confluence of marine and fresh waters, estuaries experience both the seaside pressures of rising sea levels and increasing storm severity, and watershed and precipitation changes that are shifting the quality and quantity of freshwater and sediments delivered from upstream sources. Boating, shoreline hardening, harvesting pressure, and other signatures of human activity are also increasing as populations swell in coastal regions. Given this shifting landscape of pressures, the factors most threatening to estuary health and stability are often uncertain. To identify the greatest contemporary threats to coastal wetlands and oyster reefs across the southeastern United States (Mississippi to North Carolina), we summarized recent population growth and land-cover change and surveyed estuarine management and science experts. From 1996 to 2019, human population growth in the region varied from a 17% decrease to a 171% increase (mean = +43%) with only 5 of the 72 SE US counties losing population, and nearly half growing by more than 40%. Individual counties experienced between 999 and 19,253 km2 of new development (mean: 5725 km2), with 1–5% (mean: 2.6%) of undeveloped lands undergoing development over this period across the region. Correspondingly, our survey of 169 coastal experts highlighted development, shoreline hardening, and upstream modifications to freshwater flow as the most important local threats facing coastal wetlands. Similarly, experts identified development, upstream modifications to freshwater flow, and overharvesting as the most important local threats to oyster reefs. With regards to global threats, experts categorized sea level rise as the most pressing to wetlands, and acidification and precipitation changes as the most pressing to oyster reefs. Survey respondents further identified that more research, driven by collaboration among scientists, engineers, industry professionals, and managers, is needed to assess how precipitation changes, shoreline hardening, and sea level rise are affecting coastal ecosystem stability and function. Due to the profound role of humans in shaping estuarine health, this work highlights that engaging property owners, recreators, and municipalities to implement strategies to improve estuarine health will be vital for sustaining coastal systems in the face of global change.

Unraveling Interactions between Asymmetric Tidal Turbulence, Residual Circulation, and Salinity Dynamics in Short, Periodically Weakly Stratified Estuaries

AbstractAsymmetric tidal turbulence (ATT) strongly influences estuarine health and functioning. However, its impact on the three-dimensional estuarine dynamics and the feedback of water motion and salinity distribution on ATT remain poorly understood, especially for short estuaries (estuarine length ≪ tidal wavelength). This study systematically investigates the abovementioned interactions in a short estuary for the first time, considering periodically weakly stratified conditions. This is done by developing a three-dimensional semi-analytical model (combining perturbation method with finite element method) that allows a dissection of the contributions of different processes to ATT, estuarine circulation, and salt transport. The generation of ATT is dominated by (i) strain-induced periodic stratification and (ii) asymmetric bottom-shear-generated turbulence, and their contributions to ATT are different both in amplitude and phase. The magnitude of the residual circulation related to ATT and the eddy viscosity–shear covariance (ESCO) is about half of that of the gravitational circulation (GC) and shows a “reversed” pattern as compared to GC. ATT generated by strain-induced periodic stratification contributes to an ESCO circulation with a spatial structure similar to GC. This circulation reduces the longitudinal salinity gradients and thus weakens GC. Contrastingly, the ESCO circulation due to asymmetric bottom-shear-generated turbulence shows patterns opposite to GC and acts to enhance GC. Concerning the salinity dynamics at steady state, GC and tidal pumping are equally important to salt import, whereas ESCO circulation yields a significant seaward salt transport. These findings highlight the importance of identifying the sources of ATT to understand its impact on estuarine circulation and salt distribution.

Influence of land-derived stressors and environmental variability on compositional turnover and diversity of estuarine benthic communities

It can be challenging to differentiate community changes caused by human activities from the influence of natural background variability. Using gradient forest analysis, we explored the relative importance of environmental factors, operating across multiple spatio-temporal scales, in influencing patterns of compositional turnover in estuarine benthic macroinvertebrate communities across New Zealand. Both land-derived stressors (represented by sediment mud content and total sediment nitrogen and phosphorus content) and natural environmental variables (represented by sea surface temperature, Southern Oscillation Index, and wind-wave exposure) were important predictors of compositional turnover, reflecting a matrix of processes interacting across space and time. Generalized linear models were used to determine whether measures of benthic macroinvertebrate diversity, which are commonly used as indicators of ecological health on a local scale, changed in a way that was consistent with the compositional turnover along the environmental gradient. As expected, compositional turnover along land-derived stressor gradients was negatively associated with diversity indices, suggesting a decline in ecological health as land-derived stressors increase. This study moves towards an ecosystem-based management approach that focusses on cumulative effects rather than single stressors by considering how multiple land-derived stressors influence indicators of estuarine health, against a background of natural variability across several spatio-temporal scales.

A comparison between the morphological and molecular approach to identify the benthic diatom community in the St Lucia Estuary, South Africa

The use of diatoms as bioindicators to detect human-induced change is a globally accepted monitoring tool. DNA metabarcoding is an effective complementary tool to standard microscopic methods for species identification, providing reliable and timeous diatom assessments in a range of aquatic ecosystems. This study evaluated the suitability of the DNA metabarcoding approach for diatom monitoring in the St Lucia Estuary, South Africa. Results obtained from the standard microscopic (morphological) and molecular methods were compared and indicated a low similarity in the vegetated (11%), unvegetated (12%) and epiphytic (12%) habitats at species level for the epipelic and epiphytic diatom communities. The difference between the methods was expected given the challenges pertaining to the incomplete molecular reference database, intragenomic variability, physiological differences (number of chloroplasts) and highly variable microphytobenthos biomass. While the molecular method was unable to identify the presence of all the dominant diatom species (routinely used as ecological indicators), the available molecular operational taxonomic units (MOTUs) provided an effective complementary tool to determine the relevant community diversity estimates required for the application of the South African estuarine health index (EHI).

The development of a national approach to monitoring estuarine health based on multivariate analysis.

New Zealand has a complex coastal environment spanning a large latitudinal gradient and three water masses. Here we assess whether multivariate analyses of benthic macrofaunal community composition can be a sensitive approach to assessing relative estuarine health across the country, negating the need for regional indices and reducing reliance on reference sites. Community data were used in separate canonical analyses of principal coordinates to create multivariate models of community responses to gradients in mud content and heavy metal contamination. Both models performed well (R2 = 0.81, 0.71), and were unaffected by regional and estuarine typology differences. The models demonstrate a sensitive and standardized approach to assessing estuarine health that allowed separation of the two stressors. This approach could be applied to other stressors, countries or regions.

Designing solutions for clean water on Cape Cod: Engaging communities to improve decision making

Many of the remaining mechanisms for reducing land-based nitrogen release in coastal communities depend on behavior change, social acceptance, and public support of localized mitigation programs. These needs necessitate appropriate and effective stakeholder engagement. Cape Cod, Massachusetts, USA, is one example of an area undergoing significant local, regional, state and federal decision-making processes to address nitrogen impacts on coastal waterbodies through an update to its Area Wide Water Quality Management Plan (208 Plan). The 208 Plan Update seeks to support mitigation of nitrogen pollution and restore estuarine health through active community engagement with elected officials, town staff, citizens, and other stakeholders across its 53 embayment watersheds, 35 of which are deemed impaired. With an economy deeply tied to the environment, the region is in the difficult position of needing to make significant infrastructure investments to maintain its reputation for high quality coastal waters. It is the first region in the United States to undergo an extensive revisit of its Area Wide Water Quality Management Plan developed pursuant to Section 208 of the federal Clean Water Act for the purpose of addressing nitrogen. The community engagement process for the 208 Plan Update set forth to 1) understand the range of perspectives regarding the extent of the nitrogen impacts as well as the possible solutions, 2) ensure two-way communication of available information, and 3) build trust through a transparent process. The process specifically applied a number of different mechanisms for community engagement which enabled progress in addressing nitrogen management needs. The process helped to determine and address barriers to successful implementation of nitrogen mitigation plans and resulted in a framework for watershed-based planning that relies on regional coordination and supports local selection of mitigation strategies. As a result, communities in the region are developing innovative cross-municipal partnerships and committing to fund infrastructure necessary to decrease nitrogen loading to coastal embayments.

HEMATOLOGY, BIOCHEMISTRY, AND METAL CONTAMINANT LEVELS IN WILD-CAUGHT CLAPPER RAIL (RALLUS CREPITANS) IN NORTHEASTERN FLORIDA.

The clapper rail (Rallus crepitans) is native to salt marshes along the eastern United States. Populations are likely stable, but may be at risk due to the degradation of wetland habitat by contaminants. Contaminants can cause adverse effects in birds such as alteration of immune and reproductive function, and previous studies have used this species as a sentinel for estuarine health. Blood samples were collected from clapper rails in Florida and hematology counts, plasma biochemistry panels, and metal assessments using inductively coupled plasma-mass spectrometry were performed. Biochemical and hematology data were too limited to determine if contaminants were adversely affecting clapper rails in this study, but cadmium, lead, and zinc were increased for several birds. Although contaminant levels were not consistently elevated for all birds, additional research is needed to assess if clapper rails in this region are at risk of contaminant exposure due to increasing urbanization and development pressures.

Is there a link between acetylcholinesterase, behaviour and density populations of the ragworm Hediste diversicolor?

The main objective of the present study was to explore the potential link between acetylcholinesterase (AChE) activity and burrowing behaviour of the ragworm Hediste diversicolor, which may have consequences at higher levels of biological organisation. Two complementary studies were conducted. AChE activity, at the sub-individual level, and behavioural responses, at the individual level, were evaluated in worms from the Loire estuary (France), whereas density and biomass of H. diversicolor were determined at the population level. A Spearman positive correlation between both biomarkers (AChE and burrowing) suggested that inhibition of AChE activity was linked to behaviour impairments. At the population level, lower AChE and behaviour activities were detected in worms corresponding to lower population density and biomass. These results provide direct empirical field evidence demonstrating the sensitivity of behaviour of H. diversicolor as a biomonitor of estuarine health status assessment.

Sediment grain size measurements are affected by site-specific sediment characteristics and analysis methods: implications for environmental monitoring

ABSTRACTSediment grain size, and specifically changes in the percent mud content (i.e. the fraction <63 µm) over time is often used as an indicator of estuarine environmental health. Using sediment samples from three distinct estuarine systems, we determined that different analytical methods (laser diffraction and wet sieving) gave significantly different results in terms of percent mud content. These differences are also ecologically meaningful when considering the influence of mud on estuarine macrofauna. We propose an approach to measuring sediment grain size termed Environmentally Available Sediment (EAS), which advocates for the measurement of the sediment that biota are directly exposed to. For the purposes of environmental monitoring, it is also essential to monitor sediment grain size in a repeatable way which is likely to be achieved using consistent (or no) pre-treatment and the use of a measurement technique that is unlikely to change over time, e.g. wet sieving.

Differences in trophic resources and niches of two juvenile predatory species in three Pangani estuarine zones, Tanzania: stomach contents and stable isotope approaches

BackgroundEstuaries are primary habitats that serve as feeding and nursery grounds for most juvenile marine fish. However, estuaries have been used as fishing grounds by the artisanal fishers in Tanzania. The slow-growing predatory fish at juvenile and sub-adult stages are among the most frequently caught species that functionally enhance multiple linkages of energy pathways within the food web. Stomach contents and stable isotopes (δ13C and δ15N) were used to describe the nutritional sources and trophic niches between the co-existing benthic, predatory species, Carangoides chrysophrys and Epinephelus malabaricus in the Pangani estuary, Tanzania.ResultsThe findings indicated significant inter-specific variations in dietary composition (PERMANOVA, p = 0.001, pseudo-F = 15.81). The prey-specific index of relative importance (%PSIRI) indicated that juvenile shrimps (%PSIRI = 51.4) and Teleostei (%PSIRI = 26.5) were the main diets of C. chrysophrys while brachyura (%PSIRI = 38.8), juvenile shrimps (%PSIRI = 25.6) and Teleostei (%PSIRI = 23.3) were important diets of E. malabaricus. The isotope mixing models indicated that the predatory fish species accumulate nutrients derived from similar autotrophic sources, microphytobenthos, seagrass and macro-algae via consumption of small fish, including clupeids and mugilids. Yet, they significantly showed different isotopic niche width with varying degree of niche overlap across the longitudinal estuary gradient. This situation was justified by the presence of basal food sources among the estuarine zones that isotopically were different.ConclusionThe reliance of both predators on clupeids and mugilid preys that are trophically linked with estuarine and marine basal food sources, is an indication of low estuarine food webs’ connectivity to the fresh water related food web. This situation is most likely threatening the stability of the estuarine food web structure. Management strategies and plans in place should be cautiously implemented to ensure the balanced anthropogenic freshwater use in the catchment and fishing activities, for the maintenance of the Pangani estuarine ecosystem health.

Three Decades of Change in Demersal Fish and Water Quality in a Long Island Sound Embayment

Estuaries are impacted by multiple anthropogenic stressors from eutrophication to climate change. Long-term observational datasets allow the determination of trends in estuarine indicators and the prediction of future conditions. Here, a dataset of water quality and demersal fish community composition in a Long Island Sound embayment (Norwalk Harbor, Connecticut) from 1987 to 2016 was examined. Mean water column water temperature increased, dissolved oxygen decreased, and salinity increased over the study period, with simultaneous changes in the demersal fish community. Fish abundance declined overall, with declines in CPUE observed across multiple species including the commercially important winter flounder (Pseudopleuronectes americanus). As fish can serve as effective indicators of estuarine health, these changes suggest a negative shift in the health of this Long Island Sound embayment. Climate change presents an increasing threat to estuaries and the ecosystem services they provide, especially when coupled with other anthropogenic stressors. Management actions are needed at multiple spatial scales, from local to global, to combat these threats to estuarine health.

Detecting artificialization process and corresponding state changes of estuarine ecosystems based on naturalness assessment

Estuarine artificialization eliminates estuarine ecosystems’ original natural attributes on which estuarine health and function are dependent, and induces various ecological and social problems. Preventing estuaries from being overly artificialized and implementing ecological restoration for damaged estuaries is an urgent management concern. This study intended to quantitatively identify the artificialized degree of estuarine areas of interest at different stages to depict their state evolution trajectory by acquiring and analyzing the spatiotemporal maps of estuarine ecosystem naturalness. The Xiaoqinghe estuary, located in the southern coast of Laizhou Bay, was selected as a case study area. The ecosystem naturalness and regional naturalness in this estuary were evaluated through the developed naturalness index, which integrates the dynamic information of land cover and human interference intensity into an assessment framework of ecosystem naturalness spectrum created here. Results showed that the Xiaoqinghe estuary was a relatively natural estuary with higher naturalness in the early 1980s, but was highly artificialized in 2010–2015, with its average naturalness reducing by 43% over the past three decades. Those areas occupied by salt marshes and shrub-grass lowlands in 1984 have greatly deviated from their original natural state due to the highest loss of regional naturalness. The current state characteristics suggest that the Xiaoqinghe estuary has considerably lost its ability to conserve biodiversity and provide ecosystem services, and the intensity and manner of human activities should be adjusted and limited spatially. The findings and methodology illustrated in this paper can also contribute to the sustainable management of artificialized estuaries elsewhere.