Washington State Department of Ecology

Aquatic Plant Management

Description of Method - Aquatic Plant Survey Methods

Aquatic plant survey methods vary depending on your objective. It is important to have a skilled botanist identify the plants. Many aquatic species look alike and sometimes it is necessary to conduct DNA testing to distinguish similar species. Collect and press voucher specimens from each waterbody. These can be important when verifying noxious weed infestations.

Objective: To find particular species (for example surveying for noxious weeds or rare plants). You need to mark the locations of the plant on a map or use a GPS (Geographic Positioning System) to note the locations.

Surface survey - uses a boat and trained observer to examine the littoral zone of a waterbody from the water's surface. This is the quickest method using low technology. Underwater viewing can be enhanced by using an underwater viewing tube.
Divers - uses SCUBA divers to examine the littoral zone of a waterbody and produces similar, but more thorough results to a surface survey. Underwater scooters greatly speed the process.
Helicopter or airplane - useful for surveying for wetland species like purple loosestrife or floating species like water hyacinth. This survey method can be less useful for locating submersed species.

Objective: To create a plant community map where you need to record the plant species and the species locations on a waterbody map.

Surface survey - quick, but not that accurate if the water is not clear. The survey crew needs to sample regularly at different depths, recording each species. A weighted rake (without a handle) with a rope attached makes a good sampling tool. Plants can be identified and marked on the map.
Divers - use for greater accuracy. Divers can be used in deep water in combination with a surface survey in the shallows.
Remote sensing - effective for plants on the surface. High technology, often uses infrared video-imagery with global positioning system and geographic information systems.

Objective: to quantify the vegetation. This is important when evaluating the effectiveness of a treatment or changes to the plant community over time.

Frequency Data

This can be done at points around the waterbody, or along selected transects
Plant species data is collected from the surface using a weighted rake or sampling device, or with snorkelers or divers
This type of survey can be used to determine if the frequency that a particular species is found changes over time. This survey can also be used to detect changes in species diversity over time.

Biomass Data -obtaining the weight of species abundance

The survey is the most time consuming, but yields the most accurate information. The data is analyzed statistically.
Usually uses divers to collect samples from a predetermined plot size, samples must be randomly located along transects or in plots
Samples are usually sorted to species and dried before weighing

Additional Information about Aquatic Plant Survey Methods

Madsen, J.D. and J.A. Bloomfield. 1993. Aquatic Vegetation Quantification Symposium: An Overview. Lake and Reservoir Management. 7(2): 137-140.

Spencer, D. F. and L. C. Whitehand. 1993. Experimental Design and Analysis in Field Studies of Aquatic Vegetation. Lake and Reservoir Management. 7(2) 165-174. (there are several other papers on this topic in that issue of Lake and Reservoir Management)

Madsen, J. D. 1999. Point Intercept and Line Intercept Methods for Aquatic Plant Management. US Army Corps of Engineers Waterways Experiment Station, Aquatic Plant Control Technical Note M1-02.

Questions about this page? Contact Kathy Hamel by e-mail at kham461@ecy.wa.gov