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Coastal & Estuarine Science News (CESN)

Coastal & Estuarine Science News (CESN) is an electronic publication providing brief summaries of select articles from the journal Estuaries & Coasts that emphasize management applications of scientific findings. It is a free electronic newsletter delivered to subscribers on a bimonthly basis.

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2017 September


Building Better Bridges for Scientists and Managers
All Shoreline Armoring Not Created Equal
SAVs Serve As Spawning Substrate
Tracking the Endangered Delta Smelt

Building Better Bridges for Scientists and Managers

A project from the mid-Atlantic region provides a promising new model

Conducting scientific research that contributes to coastal management is the goal of many projects. However, this is easier said than done, either because the science does not effectively address management concerns or because the results are not well-translated. A recent project in the mid-Atlantic region overcame these obstacles by maximizing communication and the participation of managers at every step.

In 2008, NOAA issued a request for research proposals for projects focused on evaluating the effects of multiple stressors on submerged aquatic vegetation and nearshore communities. Management needs drove the objectives of the request, managers assisted with evaluating the proposals, and one of the funding criteria was including a plan for the continued involvement of the management community over the life of the project.

The selected project established a Management Transition Advisory Group chosen to maximize participation of middle rather than upper managers, based on the idea that they are not political appointees but rather professionals who can remain involved over the long-term and provide crucial institutional memory. The group held annual 1.5 day meetings for the scientists and the managers (as opposed to broad stakeholder meetings that can sometimes lose focus). During these meetings, the science team provided updates on their progress, and the management team offered guidance on how to maximize the usefulness of the research. Although not all of the management ideas could be acted on, these meetings led to changes in sampling and analyses. Moreover, the participation of the advisory group resulted in improved translation of the results, which are now being incorporated into the Chesapeake Bay Goal Implementation Teams and other management efforts. The authors hope that the success of this effort will inspire others to take a similar “targeted engagement” approach.

Source: Turner, E., and T. Jordan. 2017. Integrating regional management needs into a Mid-Atlantic shorelines research project. Estuaries and Coasts. DOI: 10.1007/s12237-017-0261-y

All Shoreline Armoring Not Created Equal

Assessing the ecological effects of multiple types of shoreline armoring

Shoreline armoring structures, from seawalls to sills, are found in a wide range of coastal ecosystems around the world. However, a synthesis of their ecological effects across the variety of structure types and environments is lacking. A team of researchers recently tackled this problem using a new conceptual model to categorize and compare the impacts of shoreline armoring across a range of soft sediment coastal environments, from protected harbors to open coast beaches.

The conceptual model divides shoreline armoring into categories based on two factors: whether the purpose of the structure is to slow or completely stop the flow of water, and the hydrodynamic energy of the environment, classified as low, medium, or high. The researchers predicted greater negative ecological effects for structures designed to stop water flow and for those found in high-energy environments. Reviewing 88 studies, they synthesized the available data on six categories of ecological effects of shoreline armoring—habitat distribution, species assemblages, trophic structure, nutrient cycling, productivity, and connectivity.

Over all the studies reviewed, 71% of the documented effects were significantly negative, 22% were significantly positive, and 7% were not significant. Negative responses were more frequent when structures were intended to stop water flow, as predicted. Trends across the hydrodynamic energy axis were less clear-cut but do suggest intensifying ecological effects with increasing energy. These finding suggest that as structures move lower due to rising sea levels, ecological impacts may increase.

Most of the studies reviewed were from low-energy environments, such as salt marshes, and addressed changes in just two ecological responses, habitat distributions and species assemblages, highlighting knowledge gaps where more research is needed. However, this paper provides an important first step in generalizing predictions of the ecological impacts of different types of shoreline armoring across a range of coastal ecosystems.

Source: Dugan, J.E., K.A. Emery, M.A. Alber, C. Alexander, J.E. Byers, A. Gehman, N. McLenaghan, and S. Sojka. 2017. Generalizing ecological effects of shoreline armoring across soft sediment environments. Estuaries and Coasts. DOI: 10.1007/s12237-017-0254-x

SAVs Serve As Spawning Substrate

Study ties aquatic vegetation complexity to herring egg survival in the Baltic Sea

Thriving beds of submerged aquatic vegetation are often seen as an indicator of a healthy ecosystem, but their role as a spawning substrate for fish has not been well-studied. Research from Germany shows that the structural complexity of this vegetation plays a role in the successful reproduction of Atlantic herring.

Baltic Sea populations of Atlantic herring are a major fishery resource and use vegetated areas for spawning. One of their major spawning grounds is the southwestern Baltic Sea, and it’s in this region that a recent study evaluated the effects of the structural complexity of aquatic vegetation on egg survival. Researchers artificially spawned herring to create a layer of eggs on plastic aquarium plants with different degrees of complexity. They ran two experiments—one in the early season (when temperatures ranged from 4-6 C°) and the second a month later (when temperatures had warmed up to 11-13 C°)—that corresponded to the two major annual spawning events.

Environmental conditions at lower water temperatures are less stressful to herring eggs, and during the early season egg survival did not differ significantly between treatments. However, during the late season, egg mortality was three times higher in the treatment with low as compared to high structural complexity. This late season effect is particularly relevant given the fact that the later cohorts are thought to contribute most to annual recruitment and suggests that environmental stressors may amplify the effect of spawning substrate.

Because of increasing nutrient runoff, the submerged aquatic vegetation communities of the Baltic Sea’s inner coastal areas are experiencing ongoing declines and shifts in species composition, which could threaten the health of the region’s herring fishery. This study shows that “spawning substrate” should be added to the already-long list of reasons to value healthy aquatic vegetation communities.

Source: von Nordheim, L., P. Kotterba, D. Moll, and P. Polte. 2017. Impact of spawning substrate complexity on egg survival of Atlantic herring (Clupea harengus, L.) in the Baltic Sea. Estuaries and Coasts. DOI: 10.1007/s12237-017-0283-5

Tracking the Endangered Delta Smelt

Statistical models predict population density across space and time

San Francisco’s delta smelt are in trouble. This endangered species has suffered increasing declines in recent years, and in order to turn things around managers need to know more about how these fish are distributed within the San Francisco Estuary and what factors are driving changes in the population. However, smelt are small, pelagic fish that are difficult to track with traditional tagging methods. To get around this, scientists used an extensive dataset encompassing the results of thirteen years of trawling surveys and accompanying environmental information collected by the California Department of Fish and Wildlife to create a series of statistical models to predict fish density in the estuary across space and time.

The best model for predicting smelt density included local conditions such as water clarity and tide stage as well as an adjustment for consistent density differences between regions of the estuary. The distribution of adult fish was fairly consistent across months and years, with the exception of the appearance and disappearance of hot spots each year that may be evidence of spawning aggregations.

Both the model and the empirical observations show continued declines in the smelt population, and this is an issue that deserves continued attention. Future work is needed to improve our understanding of what factors create ideal spawning habitat for smelt and how this may vary between locations and years.

Source: Polansky, L., K.B. Newman, M.L. Nobriga, and L. Mitchell. 2017. Spatiotemporal models of an estuarine fish species to identify patterns and factors impacting their distribution and abundance. Estuaries and Coasts. DOI :10.1007/s12237-017-0277-3