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An a priori process for selecting candidate reference lakes for a national survey

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Title An a priori process for selecting candidate reference lakes for a national survey
Names Herlihy, Alan T. (creator)
Sobota, Janel Banks (creator)
McDonnell, Todd C. (creator)
Sullivan, Timothy J. (creator)
Lehmann, Sarah (creator)
Tarquinio, Ellen (creator)
Date Issued 2013-02-12 (iso8601)
Note To the best of our knowledge, one or more authors of this paper were federal employees when contributing to this work.
This is the publisher’s final pdf. The published article is copyrighted by The Society for Freshwater Science and can be found at: http://www.freshwater-science.org/.
Abstract One of the biggest challenges when conducting a national-scale assessment of lakes, such as the
2007 US National Lake Assessment (NLA), is finding enough reference lakes to set appropriate
expectations for the assessed sites. In the NLA, a random design was used to select lakes for sampling to
make unbiased estimates of regional condition. However, such an approach was unlikely to yield enough
minimally impacted lakes to use as reference sites, especially in disturbed regions. We developed a 3-stage
process to select candidate reference lakes to augment the NLA probability sample in the northeastern
USA (Northeast). Screening included a water-chemistry database filter, landuse evaluation, and analysis of
aerial photographs. In the Northeast, we assembled a database of 2109 lakes >4 ha in surface area, of which
369 passed the water-chemistry screen. Of these, 220 failed the watershed landuse screen and 60 failed the
aerial photograph screen, leaving a set of 89 optimal candidate reference lakes. Twenty of these lakes were
sampled as potential reference lakes in the NLA. Based on a wide variety of indicators, NLA field
measurements indicated that almost all (85–100%) of the chosen candidate reference lakes had leastdisturbed
water chemistry, although somewhat fewer had least disturbed physical habitat (74–79%) and
biology (68–78%). Nevertheless, our 3-stage screening process was an efficient method for identification of
good candidates for reference-lake sampling. The reference-lake selection process used in our study can be
done in the office and relatively inexpensively. As such, it is very useful for large-scale regional or national
studies encompassing areas too large to census. It also has the advantage of adding a level of consistency
and quantification to the reference-site selection process.
Genre Article
Topic Reference condition
Identifier Herlihy, A., Sobota, J., McDonnell, T., Sullivan, T., Lehmann, S., & Tarquinio, E. (2013). An a priori process for selecting candidate reference lakes for a national survey. Freshwater Science, 32(2), 385-396. doi:10.1899/11-081.1

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