Phase 2. Feasibility of Implementation 



Guideline 3: Data Collection Methods 



Methods for collecting all indicator measurements should be described. Standard, well-documented 

 methods are preferred. Novel methods should be defended with evidence of effective performance 

 and, if applicable, with comparisons to standard methods. If multiple methods are necessary to 

 accommodate diverse circumstances at different sites, the effects on data comparability across sites 

 must be addressed. Expected sources of error should be evaluated. 



Methods should be compatible with the monitoring design of the program for which the indicator is 

 intended. Plot design and measurements should be appropriate for the spatial scale of analysis. Needs 

 for specialized equipment and expertise should be identified. 



Sampling activities for indicator measurements should not significantly disturb a site. Evidence should 

 be provided to ensure that measurements made during a single visit do not affect the same measurement 

 at subsequent visits or, in the case of integrated sampling regimes, simultaneous measurements at the 

 site. Also, sampling should not create an adverse impact on protected species, species of special 

 concern, or protected habitats. 



Once it is determined that the proposed indicator is relevant to the assessment being conducted, the next 

 phase of evaluation consists of determining if the indicator can be implemented within the context of the 

 program. Are well-documented data collection and analysis methods currently available? Do the logistics 

 and costs associated with this indicator fit into the overall program plan? In some cases a pilot study may be 

 needed to adequately address these questions. As described below, the answer to all these questions is 

 yes for dissolved oxygen. Once again, this applies only to using DO to address the extent of hypoxia/anoxia 

 for a regional monitoring program. 



A variety of well-documented methods are currently available for the collection of dissolved oxygen data in 

 estuarine waters. Electronic instruments are most commonly used. These include simple dissolved oxygen 

 meters as well as more sophisticated CTDs (instruments designed to measure conductivity, temperature, 

 and depth) equipped with DO probes. A less expensive, although more labor intensive method, is a Winkler 

 titration. This "wet chemistry" technique requires the collection and fixation of a water sample from the field, 

 and the subsequent titration of the sample with a thiosulphate solution either in the field or back in the 

 laboratory. Because this method is labor intensive, it is probably not appropriate for large monitoring 

 programs and will not be considered further. The remainder of this discussion will focus on the collection of 

 DO data using electronic instrumentation. 



Other variations in methodology include differences in sampling period, duration, and location. The first 

 consideration is the time of year. Hypoxia is most severe during the summer months when water temperatures 

 are high and the biota are most active. This is therefore the most appropriate time to monitor DO, and it is 

 the field season for the program in which we are considering using this indicator. The next consideration is 

 whether to collect data at a single point in time or to deploy an instrument to collect data over an extended 

 period. Making this determination requires a pnon knowledge of the DO dynamics of the area being studied. 

 This issue will be discussed further in Guideline 9. For the purpose of this evaluation guideline, we will 

 focus on single point-in-time measurements. 



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