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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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2013 June


Dissolving Misconceptions about Ocean Acidification: How Important is it in Coastal Ecosystems?
The Runaway Weed: Study Concludes that Phragmites australis Management has not been Effective
When One (Management Goal) is Not Enough: Researchers Propose Decision Support Tool for Understanding Tradeoffs
Review Outlines Factors Influencing Fecal Contamination in Coastal Waters and Shellfish

Dissolving Misconceptions about Ocean Acidification: How Important is it in Coastal Ecosystems?

Among the hottest of hot topics in environmental science is ocean acidification, the reduction of pH in the open ocean attributable to anthropogenic CO2 emissions. This issue is particularly problematic for calcifying organisms, which have trouble depositing and maintaining shells as pH declines because they are essentially dissolved by the seawater around them. Although ocean acidification is understudied and of serious concern, the annual 2013 H. T. Odum Synthesis Essay, recently published in Estuaries and Coasts, points out that pH dynamics are very different in coastal ecosystems than in the open ocean: pH is much more variable in coastal waters, and influenced by a broader suite of factors. So, is anthropogenic ocean acidification important in coastal areas?

The authors review the many processes that can affect pH in coastal waters in addition to CO2 emissions. Intense metabolic activity in coastal habitats results in strong diel to seasonal fluctuations in pH, whereas anthropogenic impacts, including land use practices and activities in the watershed, top the list of drivers of longer-term pH. Changes in land use can affect the export of carbon, acids, and carbonate alkalinity, and eutrophication influences both respiration and photosynthesis, ultimately leading to changes in pH. Some of these factors might even increase pH, counteracting acidifying effects. A literature review reveals that pH in coastal systems is normally highly variable compared to oceanic systems. While pH typically varies by less than 0.1 pH unit annually in the ocean, reported pH values for coastal and estuarine waters can vary by as much as 1 unit even over the course of a single day.

The authors conclude that ocean acidification is not the most important driver of pH change in coastal ecosystems. Instead, they propose a new paradigm which broadens the discussion of coastal pH to consider all of the factors that affect acidity/alkalinity, including land use, nutrient inputs, and net community metabolism. This new framework would allow for the formulation of more effective monitoring and management plans.

Source: Duarte, C. M., I. E. Hendriks, T. S. Moore, Y. S. Olsen, A. Steckbauer, L. Ramajo, J. Carstensen, J. A. Trotter, and M. McCulloch. 2013. Is ocean acidification an open-ocean syndrome? Understanding anthropogenic impacts on seawater pH. Estuaries and Coasts 36(April 2013). DOI: http://dx.doi.org/10.1007/s12237-013-9594-3.

 The Runaway Weed: Study Concludes that Phragmites australis Management has not been Effective

In the late 1800s, an invader landed on U.S. shores, which, many studies have shown, has wreaked havoc on our coastal ecosystems: the Eurasian genotype of the wetland grass Phragmites australis. Managers have spent decades and millions of dollars trying to beat it into submission. With so much effort focused on Phragmites management, it seems like it should be on its way out, but success of such management programs has rarely been evaluated. A research team recently assessed Phragmites management using a cross-institutional survey of 285 land managers from U.S. public and private conservation organizations. Survey participants were asked to report on their management objectives, control methods, expenditures, and outcomes of Phragmites management initiatives. The researchers found that from 2005 to 2009 the responding organizations spent more than $4.6 million per year on P. australis management, and that 94% of responding organizations used herbicide to treat a total area of about 80,000 ha (about 90,000 ha are managed for Phragmites invasion overall). Very few management programs adequately monitor the outcomes of their actions, so evaluating outcomes was difficult. Analysis of outcomes in this study was largely undertaken by asking managers their impressions of the results of their projects. Despite the large investments in Phragmites management, few organizations actually accomplished their management objectives, and there was no relationship between resources invested and management success.

These results call into question the efficacy of Phragmites control efforts in the U.S. The authors offer a few guidelines that could improve the outcomes of future efforts: first, make ecological objectives clear before undertaking a management program. Second, determine that the non-native Phragmites is indeed causing ecosystem degradation at the proposed site, and is not simply a symptom of other stressors. Third, make sure to monitor the site before, during, and after management initiatives.

Source: Martin, L. J. and B. Blossey. 2013. The runaway weed: Costs and failures of Phragmites australis management in the USA. Estuaries and Coasts 36(April 2013). DOI: http://dx.doi.org/10.1007/s12237-013-9593-4.

 When One (Management Goal) is Not Enough: Researchers Propose Decision Support Tool for Understanding Tradeoffs

Coastal management has evolved to focus on ecosystem function and restoration rather than management of a single species or individual ecosystem services. Ecosystem-based management comes with many challenges, including coordinating among the many agencies often responsible for managing a given area. An even more onerous problem is that some outcomes are competing or even mutually exclusive; tradeoffs are often a fact of life when deciding among management goals and initiatives. How can these tradeoffs be examined, predicted, and incorporated into decision-making? A recent project undertaken by a team of researchers and managers borrowed some simple models from economic theory and multi-objective decision making to develop a management action-ecosystem services matrix for estuarine ecosystems to assess tradeoffs. A diverse group of scientists and managers was convened and asked to use evidence from the literature and case studies to assign positive and negative values to the effects of various management actions on a range of ecosystem services. The matrix allowed patterns to be observed; for example, the matrix made it easy to see when a management action had multiple positive effects, or a positive impact on one ecosystem service but negative impacts on others.

Results indicated that management actions that restored or enhanced native vegetation and shellfish benefit multiple services, meaning they come with the fewest tradeoffs, whereas actions such as desalination, salt pond creation, and sand mining have large net negative effects on several of the other services considered in the matrix. Although this particular matrix does not provide sufficient detail to be used as-is in evaluating management actions at a specific site, it is an excellent starting point for discussion, and can help distinguish “easy” choices with many positive effects from those that involve more negative side effects.

Source: Needles, L. A., S. E. Lester, R. Ambrose, A. Andren, M. Beyeler, M. S. Connor, J. E. Eckman, B. A. Costa-Pierce, S. D. Gaines, K. D. Lafferty, H. S. Lenihan, J. Parrish, M. S. Peterson, A. E. Scaroni, J. S. Weis, and D. E. Wendt. 2013. Managing bay and estuarine ecosystems for multiple services. Estuaries and Coasts 36(April 2013). DOI: http://dx.doi.org/10.1007/212237-013-9602-7.

 Review Outlines Factors Influencing Fecal Contamination in Coastal Waters and Shellfish

Shellfish beds in coastal and estuarine waters are vulnerable to a variety of types of contamination, depending on their specific location, but the most hazardous to human health is fecal contamination. Because fecal contamination can cause mild to severe gastrointestinal problems for human consumers, managers are careful to monitor shellfish beds for indicators of fecal contamination. One problem with this approach is that there is not always a good correlation between concentrations of fecal indicator organisms such as Enterococcus and E. coli (FIOs) in the water and in the shellfish themselves. A recent review outlined the environmental factors that influence the concentration of FIOs in coastal waters and their accumulation in bivalves.

Factors that affect FIOs in surface waters include temperature, solar irradiance, predation, season, nutrient level, salinity, turbidity, water depth, tidal cycle, and precipitation. An overlapping but different suite of factors influences both the concentration of FIOs and the rate at which they accumulate in shellfish tissue,  including species, age, size, and particle density in the water. Filtration rates are also affected by temperature and salinity. The relationship between FIOs in the water and in shellfish tissue varies by species and is affected by the concentration of microbes in the water.

Managers can use the relationship between these factors and FIO concentrations to better predict microbial contamination of shellfish, but it is important to note that the signal of microbial contamination in shellfish may occur within 30 minutes of exposure to the contaminating source and can persist for as much as one week after rainfall. A fairly high sampling frequency is necessary to ensure that water samples accurately represent contamination status of the shellfish themselves. Finally, the authors offer a list of relevant research topics to improve understanding and management of this issue, including the role of water pumping and filtration efficiency on FIO accumulation, the dynamics of shellfish purification during periods of good water quality, and the relative contribution of age, size, maturity, and nutritional condition of individual shellfish on FIO uptake.

Source: Campos, C. J. A., S. R. Kershaw, and R. J. Lee. 2013. Environmental influences on faecal indicator organisms in coastal waters and their accumulation in bivalve shellfish. Estuaries and Coasts 36(April 2013). DOI: http://dx.doi.org/10.1007/s12237-013-9599-y.