North Temperate Lakes LTER: Macrophyte Biomass - Madison Lakes Area 1995 - current

Aquatic macrophytes are sampled from a boat at stations located at depths from 1 to 4 meters at 0.5-m intervals along transects perpendicular to the lake shoreline of the four primary study lakes in the Madison area (Lakes Mendota, Monona, and Wingra, and Fish Lake) from June to August. A weighted, double-headed garden rake is cast off the front left, front right, rear left, and rear right of the boat and then dragged approximately 2 meters across the bottom by means of an attached line. For each rake cast, the total amount of filamentous algae and aquatic macrophyte species present is assigned a density rating from 0-5 based on the extent of coverage of the upper rake head. Determination of extent of coverage involves judgment of the surveyor as to the number of rake teeth and area of teeth covered. Ratings from the 4 rake casts at each station can be averaged to compute an overall density rating for the station In addition, the total plant mass and the total filamentous algae mass in each tow is measured. To the maximum extent possible, water is squeezed from the plants to minimize the amount of water present in the final weight. Weights are recorded in the boat using field scales. Weights from the 4 rake casts at each station can be averaged to compute overall average weights for plant mass and for filamentous algae mass at the station. A related data set (Macrophyte Rating --- Madison Lakes Area), contains rake ratings for individual macrophyte species. For each rake cast, filamentous algae and any aquatic macrophyte species present are assigned a density rating from 0-5 based on the extent of coverage of the upper rake head. Determination of extent of coverage involves judgment of the surveyor as to the number of rake teeth and area of teeth covered by each species. It is necessary to separate plants to assess individual species coverage. Ratings from the 4 rake casts at each station can be averaged to compute an overall density rating for each species found at the station. Sampling Frequency: annually during summer Number of sites: 4