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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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2014 September


Evaluating the Risks of Developing a Promising New Energy Source: the Ocean
Salinity and Seagrass in the Everglades-Florida Bay System: The Challenge of Increasing Variability
By the Numbers: Quantitative Approach to Determining Management Priorities Applied to Salt Marshes

Evaluating the Risks of Developing a Promising New Energy Source: the Ocean

In the search for renewable energy sources that will slow climate change and lead to energy-independence, our gaze has turned toward the ocean. Efforts are underway in the U.S. to harness the energy of tides, offshore winds, and waves. These technologies are so new that the risks of implementing them are largely unexplored; it is critical to ensure that the solution to our energy challenges does not come at an unacceptable environmental cost. How can we evaluate the risks of these technologies when so few have yet to be placed in the ocean?

One approach is by using an Environmental Risk Evaluation System which systematically assesses the most significant risks from a scientific and regulatory perspective. For each action being evaluated, this approach examines the potential effects of the various aspects of the project that may cause stress on environmental receptors (e.g., marine or avian animals or habitats). The use of this framework for ocean renewable energy was recently evaluated by applying it to a series of emerging energy projects in the U.S. Specific stressor-receptor interactions were evaluated for each case study using a set of biophysical risk factors such as the risk of injury or death of an individual in a threatened population, the potential consequences of shifts in prey availability, and the physical risk of damage to benthic habitats. Each stressor-receptor relationship was also examined from a regulatory perspective (for example, is the species in question protected by the Marine Mammal Protection Act?).

The authors concluded that the highest risks to the marine environment are driven largely by uncertainty of the likelihood of occurrence of particular outcomes, like bird strikes by wind turbine blades, and of the significance of the effect. Some potential risks such as oil spill risk from surface vessel collision are more easily evaluated using data from other industries, and can be dismissed as unlikely. For others, more data are needed before they can be truly evaluated. The Environmental Risk Evaluation System approach provides a framework that can be used to organize future data on specific stressor-receptor interactions, which will make the transition to a standard form of risk assessment easier.

Source: Copping, A., L. Hanna, B. Van Cleve, K. Blake, and R. M. Anderson. 2014. Environmental risk evaluation system – An approach to ranking risks of ocean energy development on coastal and estuarine environments. Estuaries and Coasts (April 2014). DOI: 10.1007/s12237-014-9816-3.

Salinity and Seagrass in the Everglades-Florida Bay System: The Challenge of Increasing Variability

Salinity fluctuates in estuaries constantly, on time scales ranging from hours to months, but submerged aquatic vegetation (SAV) species in these systems are generally up for the challenge of life in such a dynamic environment. SAV can tolerate major shifts in salinity and other abiotic factors, but how much fluctuation is too much? The salinity regime in many coastal and estuarine systems is changing for a variety of reasons, chief among them the impacts of climate change, including increased frequency of storm events and sea level rise.

Recent field experiments examined the maturation of widgeon grass (Ruppia maritima), a common SAV species with a world-wide distribution, along a salinity and salinity-variability gradient in the Everglades-Florida Bay system. Transitions from each life stage of the plant to the next (seed germination, seedling and adult survival, and sexual reproduction) and salinity were measured at each of three locations: an upper (generally fresher (lower) and more stable salinity), middle, and lower site (generally more marine and more variable salinity). Both frequency and magnitude of salinity variation appeared to be stressful for the plants: Seedling and adult survival declined from the more variable (lower) to less variable (upper) sites. Short-term fluctuations (24-48 hr) seemed to have the greatest negative impact on survival. The markedly low survival at the lowest site suggested that the plant population there is not likely to be sustained.

These results provide evidence that restoration projects should seek to restore salinity regimes that promote SAV early life stage survival in order to preserve critical communities in the Everglades and other highly dynamic estuarine systems.

Source: Strazisar, T., M. S. Koch, and C. J. Madden. 2014. Seagrass (Ruppia maritima L.) life history transitions in response to salinity dynamics along the Everglades-Florida Bay ecotone. Estuaries and Coasts (May 2014). DOI: 10.1007/s12237-014-9807-4.

By the Numbers: Quantitative Approach to Determining Management Priorities Applied to Salt Marshes

When managing a marsh site, is it more important to remove tidal restrictions or plant vegetation? Is it better to enhance fish passage or control invasive plants? Of course, there are no simple answers to questions like these; the answers depend on a range of factors from the values of involved stakeholders to available resources. Every such decision involves trade-offs. One approach to sorting through the range of management options for a given site is to use structured decision making, a systematic and quantitative process for breaking a decision down into its essential elements. A recent initiative used this approach to guide selection of monitoring variables and management priorities for salt marshes within the National Wildlife Refuge System in the northeastern U.S.

A group of stakeholders first agreed on a set of fundamental objectives for salt marshes (maximize nekton abundance, maintain natural salinity, etc.). A set of measurable attributes that can be used as indicators of progress toward each objective (e.g., nekton density) was then developed. They also listed potential management actions for achieving the objectives. Next they used conceptual models, baseline monitoring data, and expert judgment to estimate how the management actions would affect each attribute, and normalized this information to a common scale. All items received numerical weights, allowing a relatively objective evaluation of the range of management options. Cost estimates for each action were also developed. By examining costs, a set of management alternatives could be chosen that maximized total management benefits while remaining within cost constraints.

This test run of the use of structured decision making served to highlight the approach’s benefits, including its transparency and its integration of monitoring from the outset. These attributes make structured decision a useful addition to the coastal manager’s tool box.

Source: Neckles, H. A., J. E. Lyons, G. R. Guntenspergen, W. G. Shriver, and S. C. Adamowicz. 2014. Use of structured decision making to identify monitoring variables and management priorities for salt marsh ecosystems. Estuaries and Coasts (May 2014). DOI: 10.1007/s12237-014-9822-5