Estuaries and Coasts

Response and Recovery of Low-Salinity Marsh Plant Communities to Presses and Pulses of Elevated Salinity Abstract In estuaries, future variation in sea level and river discharge will lead to saline intrusion into low-salinity tidal marshes. To investigate the processes that control the differential response and recovery of tidal freshwater marsh plant communities to saline pulses, a 3 × 5 factorial greenhouse experiment was conducted to examine the effects of a range of salinity levels (3, 5, and 10 practical salinity units (PSU)) and pulse durations (5, 10, 15, 20, and 30 days per month) on community composition of tidal freshwater marsh vegetation. Recovery of perturbed communities was also examined after 10 months. The results showed that community composition was increasingly affected by the more-saline and longer-duration treatments. The increasing suppression of salt-sensitive species resulted in species reordering, decreased species richness, and decreased aboveground biomass. Most of the plant species were able to recover from low-salinity, short-duration saline pulses in less than 1 year. However, because not all species recovered in the heavily salinized treatments, species richness at the end of the recovery period remained low for treatments that were heavily salinized during the treatment period. In contrast, plant aboveground biomass fully recovered in the heavily salinized treatments. Although the magnitude and duration of pulsed environmental changes had strong effects on community composition, shifts in community composition prevented long-term reductions in productivity. Thus, in this study system, environmental change affected species composition more strongly than it did ecosystem processes.

Ability of Eelgrass to Alter Oyster Growth and Physiology Is Spatially Limited and Offset by Increasing Predation Risk Abstract Marine foundation species have strong effects on sympatric species, but the strength may vary along environmental gradients. Climate change is shifting the distribution and magnitude of environmental gradients, making identification of when and where foundation species effects occur necessary for effective management. We reviewed existing work to identify expected mechanisms by which seagrass affect suspension feeding bivalves, then tested whether these effects shifted across estuarine conditions for two species of oysters (native Ostrea lurida and non-native Crassostrea gigas) grown in and out of eelgrass (Zostera marina) at six estuarine sites in Washington state. Hypothesized mechanisms of eelgrass influence include reduced predation pressure, reduced or altered food availability, and amelioration of environmental (pH) stress. We analyzed oyster survival, shell and tissue growth, shell strength, and stable isotope (SI) and fatty acid (FA) biomarkers. Oyster survival was > 20% lower in eelgrass at lower-estuary sites, but not up-estuary sites. Both species grew faster in eelgrass at one low-estuary (higher pH) site, but not elsewhere. Shell strength in eelgrass increased by 21.1% for native but decreased by 12.6% for non-native oysters. FA and SI biomarkers only differed in eelgrass at one site but correlated significantly to growth among individuals. No measurement showed a consistent response to eelgrass across estuarine conditions and taxa, and responses were often opposite of expectations based on published literature. These results have important implications for management and restoration of oysters in areas with eelgrass.

Nutrients in Saltmarsh Soils Are Weakly Related to those in Adjacent Coastal Waters Abstract Saltmarshes provide a broad range of high-value ecosystem services and can be sensitive to eutrophication, but elucidating such impacts at broad spatial scales demands a better understanding of the underlying nutrient linkages between saltmarsh soil and tidal waters. We used existing water quality data and field surveys of 15 saltmarshes across a broad trophic gradient of coastal waters, but similar biogeographic setting (in Ireland) to investigate if phosphorus and nitrogen pools in saltmarsh soils are related to those in tidal water across saltmarshes. We also investigated if the strength of such relationships is inversely related to ground elevation, which approximates the degree of tidal inundation. Plant-available phosphorus and nitrogen pools in soil were related to water nutrients, albeit only weakly. We did not find any support for the moderating influence of elevation, indicating that it may be obscured by internal cycling and external sources. We also found evidence for effect of birds on the saltmarsh nutrient pool. Saltmarsh soils are unlikely to serve as general sentinels of nutrient conditions in their corresponding water bodies and may need separate assessment criteria and management tools, which in turn require disentangling localised and whole-saltmarsh sources of variation in nutrient concentrations.

Correction to: Impact of Channel Deepening on Tidal and Gravitational Circulation in a Highly Engineered Estuarine Basin In the original article on page 1589, right column, second paragraph, seventh line, there is an error in the equation.

Correction to: Effects of Docks on Salt Marsh Vegetation: an Evaluation of Ecological Impacts and the Efficacy of Current Design Standards In the original article there was an error in the reported quadrat size. Sample quadrats were described as 1/16 m2 when they should have been reported as 1/32 m2 in the text of page 662.

Correction to: An Experimental Evaluation of Dock Shading Impacts on Salt Marsh Vegetation in a New England Estuary In the original article there was an error in the reported quadrat size. Sample quadrats were described as 1/16 m2 when they should have been reported as 1/32 m2 in the text of page 16 and in the figure legend for Figs. 6 and 7.

Correction to: Ecophysiology of the Olympia Oyster, Ostrea lurida , and Pacific Oyster, Crassostrea gigas In the original article there is an error on page 522 in the third paragraph of the Methods section. There is an erroneous 0 in the TWW coefficient. The corrected text is as follows.

Fish Utilization of Created vs. Natural Oyster Reefs ( Crassostrea virginica ) Abstract Once viewed as an inexhaustible fishery resource, eastern oyster reefs (Crassostrea virginica) have been dramatically depleted. In North Carolina alone, eastern oyster harvests have declined by 90% since the early 1900s. However, eastern oyster restoration and management efforts have substantially increased since the 1970s. Oyster reefs provide habitat and refuge for organisms, improve water quality, and decrease erosion. Oyster restoration projects aim to construct reefs that function similarly to their natural counterparts. Therefore, post-creation monitoring of these reefs is crucial in determining restoration success. However, monitoring is often lacking or focused only on oyster density and size rather than ecosystem functions such as nekton utilization. This study examines nekton utilization among created reefs compared to natural reefs in an estuary in Wilmington, North Carolina. The objective was to determine whether the created reefs function similarly to the natural reefs in abundance, species richness, and fish size. Using seine nets and Breder traps, reefs were sampled over a 5-month period. No significant difference was detected among reefs for nekton abundance, species richness, and standard length. This is a promising result for future management, indicating that created and natural reefs can support similar communities of fishes and shrimp.

Local Habitat and Seascape Structure Influence Seagrass Fish Assemblages in the Venice Lagoon: The Importance of Conservation at Multiple Spatial Scales Abstract Seagrass meadows are a critical component of estuarine and coastal seascapes, and their structure influences fish assemblages at multiple spatial scales. The patch mosaic model, which defines the seascape as a collection of interacting habitat types, is increasingly adopted to prioritise protected areas and design ecological restoration schemes, hence helping to preserve seagrass meadows and the associated fish assemblages. Despite that, there are few studies investigating the relative contribution of environmental characteristics measured at different spatial scales in determining the distribution of seagrass fish. This study collects fish and environmental observations taken at both site and seascape scales in seagrass meadows in the Venice lagoon (Adriatic Sea, Italy). By means of generalised linear models, it aims to disentangle the relative influence of local water quality and habitat characteristics from that of habitat mosaic properties, investigating the response of whole fish assemblage descriptors, feeding guilds and dominant species. While confirming the primary importance of local habitat quality, the study highlights that also seagrass habitat structure at the seascape scale is relevant for seagrass fish assemblages, influencing total biomass, biomass of macrobenthivorous and hyperbenthivorous/piscivorous species and seagrass specialists such as syngnathids. Conservation of seagrass fish assemblages can therefore be promoted in Mediterranean coastal lagoons by preserving or restoring some features of the habitat mosaic, namely the extension of seagrass patches and their shape complexity, in addition to local water quality and seagrass cover.

Effectiveness of Living Shorelines as an Erosion Control Method in North Carolina Abstract Living shorelines are a shoreline stabilization strategy encompassing a range of vegetative to structural materials and serve as an alternative approach to the use of structures like bulkheads, which are known to aggravate erosion. Living shorelines are often installed with little to no long-term monitoring for effectiveness; specifically, there is a lack of quantitative data regarding their performance as a shoreline stabilization strategy. This study sought to assess the performance of living shorelines with sills, with respect to shoreline protection, by determining shoreline change rates (SCR) using geospatial analysis. Shoreline surveys were conducted using a real-time kinematic (RTK)-GPS unit at a total of 17 living shoreline projects and nine control segments at 12 sites along the coast of North Carolina. Current shoreline position was compared to historic (pre-installation) shoreline positions obtained from aerial imagery, dating to 1993. The average SCR among northern sites before installation was − 0.45 ± 0.49 m year−1, and in southern sites, it was − 0.21 ± 0.52 m year−1. After installation, average SCR was significantly less erosive at northern and southern sites with living shorelines, 0.17 ± 0.47 and − 0.01 ± 0.51 m year−1, respectively. Of the 17 living shoreline project segments, 12 exhibited a reduction in the rate of erosion; of those 12, six were observed to be accreting. This study supports the convention that living shorelines can reduce the rate of erosion and potentially restore lost shore zone habitat.