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Using National Coastal Condition Assessment Underwater Video to Investigate Nearshore Substrate Type
Citation:
Wick, M., J. Lietz, AND M. Pawlowski. Using National Coastal Condition Assessment Underwater Video to Investigate Nearshore Substrate Type. To be Presented at International Association for Great Lakes Research, Detroit, MI, May 15 - 19, 2017.
Impact/Purpose:
not applicable
Description:
A comprehensive method for describing bottom types in Great Lakes nearshore regions (<30 m deep and <5 km from shore) would enhance our ability to target monitoring efforts. Dredges are ineffective at sampling hard bottoms (bedrock/boulder/cobble) and other habitat features. We attempted to map bottom types using underwater videos collected as part of EPA’s National Coastal Condition Assessments (NCCA; 2009-2016). The probability-based sampling design allowed area-based estimates of bottom types. Across all lakes in 2010, soft sediments (clay, silt, sand) constituted 78% of nearshore area, hard substrates constituted 11%, and 10% of the area was classified as unknown. Interestingly, <1% of Lake Huron area was found to be hard substrate. Comparing video results to Ponar-derived substrates found general agreement for soft substrate sites. For hard substrates, Ponars had high rates of sampling failure and thus more disagreement with video results. Underwater video can help improve our understanding of substrate type distribution in the Great Lakes. Improvements in video technology, and deployment and analytical procedures will allow us to better distinguish substrate type to a finer scale, and evaluate additional benthic habitat features like vegetation cover, structure, and type.