Point-Contact Transect Method
for Floating Docks

Marine Introduced Species Monitoring Resource Center

OVERVIEW Many sessile marine organisms (e.g. algae, tunicates, mussels, barnacles, anemones) need to attach to hard substrates or structures. These habitats are often in short supply in ocean waters. Therefore, the submerged floats supporting permanent floating docks, ones that remain in the water year round, provide important areas upon which marine larvae and seed can settle and grow. Mobile organisms, such as sea stars and crabs, also frequent these colonized areas to feed. Repeated samplings at the same location over an extended time are necessary to rule out natural variability in these biological communities.

Monitoring of docks is not tide-dependent. Line transects are laid out along the dock edge above the floats (see Directions #1). Presence or absence of species attached to the edge of the submerged float is recorded on a data sheet. Monitoring conditions and visibility will vary depending, for example, on the angle of the sun, cloud cover, clarity of water, wave action, and the layering of species. Actual counts or abundance estimates are difficult to make, but it is possible to distinguish between none present, 1-10, or greater than 10. This quantitative grouping will allow for more productive data analysis in the future. Twenty-eight species are listed on the Floating Dock Data Sheet with space to add other species. The data sheet is designed and tested to facilitate easy data recording. This data sheet is in MS Excel format and may be adapted to include new bioinvaders and species most commonly found in your monitoring region. Sampling may be conducted year round. However, when docks become cold, icy, or otherwise unsafe, it is best to avoid monitoring. In general, monthly monitoring from late spring to early fall is a realistic target, with the possibility of perhaps one winter sampling.

EQUIPMENT

Meter stick Clipboard and pencil Data sheet Thermometer Refractometer Permanent marker Pillow, cushion or towel

Marine Invasive ID Cards Marine Field Guides Ziplock bags or watertight containers 70% - 95% ethanol or isopropyl alcohol Net or stick Camera

DIRECTIONS
How to set-up your monitoring site:
1. Establish a random line transect 80 cm long by placing a meter stick along the edge of the dock. Since sessile organisms need to adhere to submerged surfaces, the line transect must be aligned over a dock float. Four transects laid out on the dock with each transect above a dock float.

2. With a permanent pen, place a mark at the dock edge at the beginning of the line transect. Then, mark every 20 cm along the length of the line transect (5 marks). Marking the edge of the dock helps in locating the line transects during repeat monitoring.

3. Repeat Steps 1 and 2 three more times at different places on the dock. The four line transects should be selected randomly.