Citation:

Lietz, J., J. Kelly, J. Scharold, AND P. Yurista. Can a rapid underwater video approach enhance the benthic assessment capability of the National Coastal Condition Assessmentin the Great Lakes? ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, 55(6):1446-1456, (2015).

Impact/Purpose:

This study evaluates use of UW video as a supplemental tool for benthic condition assessment. This tool was used in addition to traditional benthic condition measures used by the National Coastal Condition Assessment in 2010 surveys throughout the Great Lakes. Our study provides a method for screening the quality of QA prior to confident use in quantitative analyses, identifies several factors (“controllable,” “not controllable”) which influence video capture performance. Overall, the UW video sampling was effective in improving estimates of the area within the U.S. coastal zone across the Great lakes having invasive mussels.

Description:

In the U.S. National Coastal Condition Assessment (NCCA) field survey in summer 2010, over 400 sites in the nearshore zone of the U.S. Great Lakes were sampled. As a supplement to core NCCA benthic taxonomy and sediment chemistry, underwater video images of the bottom condition were recorded, reviewed, and subsequently evaluated for individual site performance issues. This paper contributes a protocol with standard hierarchical processes developed for reviewing images to rank the quality of visual observations for identification of several features ¯ presence of invasive mussels (dreissenids) and fish (Gobies) and macroalgae, as well as some general observations on substrate. For example, 221 of 362 videos reviewed were ranked of high-quality and deemed useable to categorize presence/absence of dreissenids with confidence. Secondly, we examined several factors, both “controllable” (e.g., due to camera deployment technique) and “uncontrollable” (e.g., due to water clarity) which influenced video performance and quality; specific thresholds in light extinction (>0.5 m-1) and chlorophyll a concentration (>3.5 µg L-1), conditions above which limited the usability of individual videos, were identified. Finally, having developed the means for screening videos for quality, as well as conditions in which use would be limited by current techniques, we were able to evaluate the contributions of this simple supplemental tool to Great Lakes assessment in a statistically-based survey such as the NCCA. At a regional scale, the inclusion of video measurements increased the estimate of the overall area of the U.S. nearshore with invasive mussels by about 15% compared to PONAR alone. Video enhancement was less effective in embayment areas, where higher turbidity often limited video, than the open nearshore, where waters were generally clearer and where hard substrate (rocks and hard sand) is more prevalent (which reduces the area than can be sampled by PONAR). The proportion of the nearshore area infested with mussels varied by lake in 2010, being lowest in Lake Superior, and highest (>50%) in Lakes Michigan, Erie, and Ontario.

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