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Post-Dredging Ecological Assessment for Upper Lake

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Post-Dredging Ecological Assessment for Upper Lake

After the Upper Lake was dredged to remove invasive species, we conducted an ecological study to measure the dredging's effectiveness

The Upper Lake in Yaphank was dredged during the summer of 2013 to remove invasive and nuisance plant species in an effort to restore the lake to its previous condition as a recreational and scenic resource.

In an effort to measure the effectiveness of the dredging operations, PWGC conducted an ecological study of Upper Lake during June 2015. The study consisted of collecting field measurements to develop bathymetric contours of the lake’s hard bottom and soft sediment thickness, and the density and distribution of both invasive and native plant species. Results were then compared to previous studies that were performed prior to dredging.

Project Details

In order to keep data collection consistent with previous studies, the Upper Lake was divided into 61 grids (150’ x 150’), similar to the Fall 2009 (B. Laing) study. A team of two scientists navigated a row boat to the approximate center of each grid square for an even distribution of sample locations.

At each location, a measuring pole was used to measure the depth to soft sediment and hard bottom. The location and depth measurements were recorded utilizing a mapping grade GPS. For the plant survey, a weed anchor (“Rake Toss Aquatic Vegetation Surveys” based upon Point Intercept Methods developed by ACOE, 1999 and Cornell, 2006) was tossed and allowed to sink to the lake bottom. Plants recovered in the rake toss were then identified and the relative density observed. Photographs (both underwater and above) were taken from each sample location.

All work was performed in accordance with the procedure followed during the “Feasibility Study to Eradicate Aquatic Invasive/Nuisance Species in Canaan Lake, North Patchogue and Upper and Lower Lakes, Yaphank.”

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