Estuarine Habitat Restoration Research Articles

Using Bayesian multispecies models to evaluate fish and invertebrate detection probability and distribution in the hypersaline Bahia Grande tidal basin

AbstractObjectiveIn 2000, the Laguna Atascosa National Wildlife Refuge acquired the Bahia Grande (Texas) management unit, a space that had lain barren and arid for 70 years. A large cooperative partnership launched a restoration project to replenish the basin and recover its original tidal hydrology. In 2005, the construction of a pilot channel successfully restored water throughout the basin, and plans to eventually widen the channel were developed. Our study aims to evaluate an estuarine habitat restoration by assessing ecological drivers and the impacts on species diversity.MethodsWe evaluated species richness, detection/occupancy rates, and species–habitat relationships, and we estimated the sampling effort required to achieve a given level of relative precision if relative abundance was used instead of occupancy to inform future sampling. Sampling gear included bag seines for juvenile life stages and gill nets for capturing subadult and adult life stages. For analysis, we used a Bayesian negative binomial linear mixed‐effects model to evaluate richness–habitat relationships and a hierarchical Bayesian multispecies model to evaluate individual species–habitat relationships, and we calculated the total number of fish captured and relative standard error by gear and sample year to produce a precise estimate of relative abundance.ResultOverall, 29 species were caught between 2018 and 2021. Salinity emerged as a clear driver in the Bahia Grande, as both species richness and individual‐level responses were negatively associated with high salinity values. We found that catch estimated as relative abundance had much variability, as is typical of most survey programs assuming constant detectability, and the number of net sets or seine hauls required to achieve a given level of relative precision varied considerably depending on the species, season, year, and gear type. The most collected species were found in the upper extremes of their salinity tolerances—potentially a unique adaptation to this hypersaline system.ConclusionBaseline data suggest that for the channel widening to be successful, there must be a noticeable increase in suitable habitat characteristics throughout the basin.

The Use of Non-Plastic Materials for Oyster Reef and Shoreline Restoration: Understanding What Is Needed and Where the Field Is Headed

Oyster and shoreline restoration is occurring around the globe to recover lost ecosystem services. In the state of Florida, USA, dozens of estuarine habitat restoration projects are underway. These projects have traditionally relied on both natural and man-made materials, including plastics. As the impacts of plastics on marine ecosystems are better understood, practitioners are increasingly focused on plastic-free restoration. To better understand this transition, we surveyed Florida restoration practitioners in April 2021 to capture current non-plastic restoration project trends and their status. Our descriptive survey goals were to understand: (1) what non-plastic materials have been tested, (2) trade-offs between plastic and non-plastic materials (e.g., cost, sourcing, volunteer engagement), and (3) the performance of non-plastic materials. Responses indicated that a variety of non-plastic materials are currently being used, including rock, cement-infused jute structures, cement Reef Balls™ (Reef Ball Foundation, USA), BESE-elements®, and metal gabions. Overall, these materials are more expensive and equally or more difficult to install than previously popular plastic-based materials. No “best” non-plastic material emerged from our survey in part because many novel materials have been deployed for under three years. Long-term performance under a variety of abiotic and biotic conditions is thus a future research priority.

Evaluation and prediction of water quality in the dammed estuaries and rivers of Taihu Lake.

Proper evaluation of water quality is pertinent to estuarine habitat restoration. Identifying the degrading factors of the water environment and predicting the trend of eutrophication are key to restore the habitat. Through trophic level index (TLI), water quality index (WQI), modified Nemerow pollution index (NPI), and the Random Forest (RF) model, water samples collected from various estuaries of Taihu Lake from 2017 to 2019 were evaluated. To predict the water quality development, four scenarios were set viz. S1: add or remove an ecological buffer, S2: increase or reduce the external nutrients, S3: open or close the dam/gate, and S4: increase or decrease the internal release. In Wuli Lake, the nutrient concentrations in the river regions were higher than in the lake regions, while a contrary trend was observed in Gonghu Bay. The estuarine water quality in the dry season (WQI = 40.91, NPI = 1.73) was merely worse than that in the wet season (WQI = 47.27, NPI = 1.67). On the other hand, the eutrophic status in the wet season (TLIWet = 57.93) was worse than that in the dry season (TLIDry = 57.23). The estuarine water quality of Taihu Lake has improved from 2017 to 2019 but still belongs to medium level. The principal component analysis (PCA) revealed that dam construction, land use types, unstable hydrodynamic conditions, and trumpet-shaped estuary were the main factors that aggravated the water quality degradation. The RF model has strong forecasting capabilities for estuarine water quality. When the estuaries are close to residential and industrial districts, controlling the surface runoff and improving sewage treatment efficiency are the most effective measures to improve the water quality. In the estuaries, the sediments are usually disturbed by the wind-waves. Conclusively, reducing sediment disturbance and internal contamination accumulation via biological and engineering measures is the key to estuarine restoration.

Quantifying the Benefits of Estuarine Habitat Restoration in the Gulf of Mexico: an Introduction to the Theme Section

This collection of papers provides insights into methods and data currently available to quantify the benefits associated with estuarine habitat restoration projects in the northern Gulf of Mexico, USA, with potential applicability to other coastal systems. Extensive habitat restoration is expected to occur in the northern Gulf of Mexico region over the next several decades through funding associated with the 2010 Deepwater Horizon oil spill. Papers in this section examine the development of vegetation, soil properties, invertebrate fauna, and nekton communities in restored coastal marshes and provide a conceptual framework for applying these findings to quantify the benefits associated with compensatory marsh restoration. Extensive meta-analysis of existing data for Gulf of Mexico coastal habitats further confirms that structured habitats such as marsh, submerged aquatic vegetation, and oyster reefs support greater nekton densities than nonvegetated bottom habitat, with oyster reefs supporting different species assemblages than marsh and submerged aquatic vegetation. Other papers demonstrate that while vegetation cover can establish rapidly within the first 5 years of restoration, belowground parameters such as root biomass and soil organic matter remain 44% to 92% lower at restored marshes than reference marshes 15 years after restoration. On average, amphipod and nekton densities are also not fully restored until at least 20 and 13 years following restoration, respectively. Additional papers present methods to estimate the benefits associated with marsh restoration projects, nekton productivity associated with coastal and estuarine habitats, and the benefits associated with the removal of derelict crab traps in Gulf of Mexico estuaries.

Predicting the response of nekton assemblages to seagrass transplantations in the Venice lagoon: An approach to assess ecological restoration

Abstract One of the major challenges to ensure effective restoration of estuarine habitats is to establish success criteria to determine whether the goals of restoration are met. The aim of this work is to propose and test an approach to identify reference conditions and assess the recovery of nekton (fish, decapods and cephalopods) assemblages at seagrass restoration sites. Nekton sampling took place from 2014 to 2017 in the northern Venice lagoon (northern Adriatic Sea, Italy) during spring at eight sites subjected to seagrass (Zostera marina and Zostera noltei) transplantation. In spring 2016, five natural seagrass sites in the same area were additionally sampled, and physico‐chemical water parameters and habitat structure were also recorded. A multivariate generalized linear model approach was adopted in order to disentangle the relative effect of water quality and seagrass habitat structure on nekton assemblages of natural habitats. Models were subsequently employed to predict species composition of nekton fauna at each transplantation site, to identify the reference assemblage expected under site‐specific abiotic and habitat characteristics. The average distance of the observed assemblage from reference conditions was used to track temporal trajectories of nekton colonization at transplantation sites, and to ultimately evaluate the recovery rate towards restoration goals. This study highlights how a predictive approach could serve management purposes in ecological restoration, providing a concise tool to assess the functionality of restored habitats for associated fauna.

"Make me a willow cabin at your gate": Legislation and implementation of tidal forest restoration at estuarine upstream sites

The restoration of estuarine habitats provides diverse ecological functions and services, e.g., vegetated foreshores reduce current speeds and attenuate waves and may enhance nursery grounds for fish and other estuarine organisms and estuarine water purification. A set of legislation regulates the conservation, usage and restoration of European estuaries. The European Habitats Directive (HD) protects biodiversity on species and habitats level and today most of the European estuaries are designated as protected Natura 2000 sites. In tidal freshwater wetlands at locations of large ports (e.g., Antwerp, Hamburg, London, Rotterdam) integrative management to maintain natural structures paralleled by ecosystem restoration with respect to flood risk reduction and harbour activities is challenging. This led to the Hamburg strategy for improving the conservation status under the HD and measures are implemented along the Elbe estuary. Alluvial forests listed as priority habitats (HD annex I) are fragmented, and tidal softwood forests comprising willows must be restored. In our case study, autochthones plant material was collected and cultivated, and used for initial plantings on a former floodplain meadow. Two years after planting, the basket, crack and purple willow reached heights of 3 m and more, whereas the number of white and almond willows was largely decreased, and numerous willows were affected by competing herbaceous vegetation. The careful selection of restoration sites including ecological hydrology providing bar ground for less competitive willows combined with the use of acclimated autochthonous Salix may enhance the restoration success of tidal floodplain forests at estuarine upstream sites.

Evaluating the U.S. Estuary Restoration Act to inform restoration policy implementation: A case study focusing on oyster reef projects

Recent research revealing the extent of marine habitat degradation has ignited a surge of restoration efforts globally. Restoration of estuarine habitats became a priority in the United States with the Estuary Restoration Act (ERA) of 2000. In the present study, a synthesis of data from the National Estuaries Restoration Inventory (NERI), developed in response to ERA requirements to track and disseminate project data, was conducted in order to analyze U.S. oyster reef restoration efforts. From 2000–2011, more than $45 million was invested in 187 projects to restore over 150 ha of oyster reef habitat, with projects most heavily concentrated in the Chesapeake Bay area and Florida Gulf coast. Trends over time indicate that projects are being implemented at larger scales, increasing from an average of less than 0.4 ha in 2000 to over 1 ha on average in 2011. Costs per unit decreased from an average of more than $2.1 million per ha in 2000 to just over $500,000 per ha in 2011. However, our analysis confirms one major problem hindering the field of restoration ecology: a lack of monitoring data or project-specific assessments of success. Habitat restoration has become an increasingly common effort in the policy sector, and gaps identified through this analysis can help inform future policy making and implementation. Better facilitation of data dissemination and further research on economies of scale in restoration projects are two key areas for improvement. As the field of restoration ecology continues to grow, it is critical that both new and current restoration practitioners, scientists, and decision-makers are able to learn from past projects and apply that collective knowledge to future restoration efforts.

English

Rebecca M. Quinones and Peter B. Moyle doi: http://dx.doi.org/10.15447/sfews.2014v12iss3art3 Climate change is expected to progressively shift the freshwater environments of the San Francisco Bay Area (SFBA) to states that favor alien fishes over native species. Native species likely will have more limited distributions and some may be extirpated. Stream-dependent species may decline as portions of streams dry or become warmer due to lower flows and increased air temperatures. However, factors other than climate change may pose a more immediate threat to native fishes. Comparison of regional vs. statewide vulnerability (baseline and climate change) scores suggests that a higher proportion (56% vs. 50%) of SFBA native species, as compared to the state’s entire fish fauna, are vulnerable to existing anthropogenic threats that result in habitat degradation. In comparison, a smaller proportion of SFBA native species are vulnerable to predicted climate change effects (67% vs. 82%). In the SFBA, adverse effects from climate change likely come second to estuarine alteration, agriculture, and dams. However, the relative effect of climate change on species likely will grow in an increasingly warmer and drier California. Maintaining representative assemblages of native fishes may require providing flow regimes downstream from dams that reflect more natural hydrographs, extensive riparian, stream, and estuarine habitat restoration, and other management actions, such as modification of hatchery operations.

Fishes and fisheries in tropical estuaries: The last 10 years

Since 2002 there has been an increase in knowledge of many aspects of the biology and ecology of tropical estuarine fishes, as well as significant changes to many estuarine fisheries. Analyses of literature databases (2002–2012) show that: of the c. 600 relevant papers, 52% are primarily related to ecology, 11% to conservation, 11% to anthropogenic and pollution effects on fishes, 9% to fisheries, 7% to aquaculture, 4% to study techniques, and 1% each to fish larvae, effects of fishing, taxonomy, climate change, evolution and genetics. In terms of geographic spread 17% are from North America, 15% from south Asia, 14% from the Caribbean, 13% from Australasia, 12% from Africa and 9% each from South America and SE Asia. Research papers came from 50 countries of which the dominant were USA (15%), India (12%), Australia (11%) and Brazil (7%). Increasing numbers of studies in West Africa, SE and South Asia and South America have increased basic knowledge of the ecology of estuarine fish faunas. Increases in understanding relate to: roles of salinity, turbidity and habitat diversity; connectivity between habitats; water flow; ecological drivers of spatial variability; scale dependent variation; thermal tolerances; movement patterns; food webs; larval adaptations; and the viability of areas heavily impacted by human activities. New reviews both challenge and support different aspects of the estuarine dependence paradigm – still perhaps one of the main research issues – and the protective function of estuaries and mangroves for juvenile fishes has received attention in relation to e.g. predation risks and fisheries. There have also been significant advances in the use of guilds and biodiversity models. Fishing pressures have continued unabated in most tropical estuaries and are summarised and management issues discussed. Understanding of the relationships between fisheries production and mangroves has advanced and significant differences have emerged between Indo-West Pacific and Atlantic systems. The effects of fishing itself have also received attention and research is often related to conservation studies. The effects of anthropogenic activities are reviewed and important advances in mitigation are discussed. Restoration of estuarine habitats, such as mangroves, previously taking place mainly in countries such as Australia and USA, is now occurring in more countries. The design of reserves and the use of protected areas as management tools are gaining credence. Finally, the evidence for actual and potential effects of climate change is discussed.

Optimal integrated operation of reservoir-assisted stormwater treatment areas for estuarine habitat restoration

Significant reductions in pollutant loadings can be achieved through coordinated operation of constructed wetlands or stormwater treatment areas (STAs) when connected to retention reservoirs for maintaining ideal water levels and hydraulic residence times in STAs that maximize treatment efficiency. Reservoir-assisted STA systems can provide additional benefits including maintenance of target frequency distributions of stormwater inflows into coastal estuarine systems for ecosystem rehabilitation, dry season flow augmentation in coastal riverine systems for maintaining the lower salinity zone, and supplemental water supply. An implicit stochastic optimization approach is applied to adaptive, multiobjective control of interconnected reservoir-assisted STAs that optimizes fuzzy rule-based operating rules using a genetic algorithm interacting with a simulation model of the stormwater drainage system. The model is applied to the four interconnected reservoir/STAs in the design configuration of the Indian River Lagoon-South project for the St. Lucie River watershed and estuary, South Florida. Results of simulated long-term performance of the optimal operating rules show attainment of targets for remediation of the aquatic ecology of the St. Lucie estuary, riverine environmental protection, and reliable supplemental water supply.

Estuarine Biotope Mosaics and Habitat Management Goals: An Application in Tampa Bay, FL, USA

Many types of anthropogenic stress to estuaries lead to destruction and conversion of habitats, thus altering habitat landscapes and changing the “arena” in which the life history interactions of native fauna take place. This can lead to decreased populations of valued fauna and other negative consequences. The Tampa Bay Estuary Program (TBEP) pioneered a system-wide management framework that develops estuarine habitat restoration and protection goals based on supporting estuarine-dependent species and the habitat landscapes they require (for example, the extent of seagrass beds, mangrove forests, oyster reefs, or oligohaline marshes) within an estuary. We describe this framework and provide related statistics as methods to help managers set system-wide ecological goals using larger conceptual approaches that are easily communicated to stakeholders and the public; we also discuss applications of the approach to existing and evolving paradigms of estuarine management. The TBEP and partners used this framework to combine a simple and unifying vision with a diverse and complex set of management tools, resulting in greatly improved environmental conditions within Tampa Bay.

Ecological assessment criteria for restoring anadromous salmonid habitat in Pacific Northwest estuaries

Restoration of estuarine habitats is essential for the conservation and recovery of depressed Pacific salmon populations. However, assessing the functions of recently restored habitat poses a number of problems because of the transitory occurrence of salmonids in any one location. We propose assessment criteria and metrics that are based on the habitat’s capacity, opportunity, and realized function to enhance survivability of juvenile salmon. Because of the paucity of data relating capacity and opportunity attributes to realized function (e.g. growth, consumption rate, survival), there continues to be a need for manipulative experiments to assess the developmental status of restoration sites. Such a self-monitoring approach of letting the fish diagnose the ecological state of restoration would effectively address the small-scale, site-specific assessment goals and criteria, but ignores the larger-scale issues relating to the ability of diverse salmon species and life histories to occupy estuarine habitat landscapes. If coastal restoration is going to contribute the recovery of anadromous salmonid populations, a landscape perspective is fundamental to restoration planning, implementation, and particularly assessment.