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Aquatic Macrophytes

Macrophytes form an integral part of the littoral zone of many lakes, providing cover for fish and substrate for invertebrates. From a human perspective, overabundant macrophytes (or weedy conditions) can interfere with lake access by fouling equipment, interfering with recreational activities, and detracting from aesthetic appeal. A conspicuous lack of native macrophytes in habitats where they are expected to occur can result in reduced population of sport and forage fish and waterfowl.

In our ponds, we would like to have some idea of the horizontal distribution of macrophytes, so we will collect multiple samples.

Procedure

1. Collect macrophyte samples at 15-20 m intervals along the transect as described below. Place the samples in separate labeled black bags so that we can determine the biomass back in the lab. Be sure to determine the Secchi depth and the depth of the water at each sampling location.

2. The easiest method to estimate macrophyte biomass is with an aquatic weed rake or thatching rake. At each station on the transect, a rake is dragged a set distance (e.g., 1 m) to sample vegetation.

3. Plants from all stations on the lake are identified and sorted by species and the total of each species is weighed after drying (dry weight) to obtain estimates of biomass and proportion of biomass of each species.