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Distribution and Growth of Submerged Aquatic Vegetation in the Piedmont Section of the James River, Virginia

Abstract Species composition, extent of coverage, biomass and factors influencing the distribution of submerged aquatic vegetation were determined within 428 10-m2 plots located along the 213-km Piedmont section of the 6th order James River, VA. The six species of submerged plants dominant in the river were ranked in abundance as follows: Heteranthera dubia > Elodea spp. > Potamogeton pectinatus > Vallisneria americana > P. illinoensis > Najas guadalupensis. The combined air-dry biomass of all species of submerged plants in the river increased rapidly from a minimum in May of 3 g/m2 to 55 to 75 g/m2 from July through October. Thirty-six percent of the riverbed along the 213 km of river was covered by submerged plants, with coverage peaking at nearly 60% of the riverbed in the middle section of the river. Stepwise regression analysis showed a weak relationship (R2 ≤ 0.12) between the distribution of plants and type of substratum, water depth, and water velocity. Digitial multispectral videography (DMSV) of submerged aquatic vegetation revealed the estimated coverage by plants of specific areas of the river bottom differed by a mean of 11% when comparing the DMSV data with that estimated visually from a boat, showing that this form of remote sensing can be used for broad scale detection and monitoring of submerged riverine macrophytes.