9 

 Years 



Figure 2-1 1 . Power curves for detecting annual changes of 1 , 1.5,2,2.5 and 3% in the 

 percent of area exhibiting hypoxia based on EMAP Virginian Province data, 

 1990-1993. 



Guideline 15: Linkage to Management Action 



Ultimately, an indicator is useful only if it can provide information to support a management decision or 

 to quantify the success of past decisions. Policy makers and resource managers must be able to 

 recognize the implications of indicator results for stewardship, regulation, or research. An indicator with 

 practical application should display one or more of the following characteristics: responsiveness to a 

 specific stressor, linkage to policy indicators, utility in cost-benefit assessments, limitations and boundaries 

 of application, and public understanding and acceptance. Detailed consideration of an indicator's 

 management utility may lead to a re-examination of its conceptual relevance and to a refinement of the 

 original assessment question. 



Currently, hypoxia and eutrophlcation are important issues, particularly in the mid-Atlantic states. Millions of 

 dollars are being spent on sewage treatment upgrades and controls for non-point sources. If these actions 

 are successful, they will result in a decrease in the percent area with low dissolved oxygen, making this 

 indicator important for measuring the efficacy of these efforts. 



Mitigation of hypoxia is a complicated issue. Sewage treatment plants, non-point source pollution, and a 

 variety of natural sources introduce nutrients to our estuaries. Increased nutrients can lead to hypoxic 

 conditions, but the effects of hypoxia are not always easy to predict. For example, increased turbidity may 

 inhibit phytoplankton growth, which, through a series of complicated interactions, may decrease a system's 

 susceptibility to reductions in DO. Management interest is not necessarily to reduce nutrient levels, but to 

 protect the biota of our estuaries from hypoxic conditions, which is exactly what this indicator is measuring. 



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