The tires are attached to the dock by their top surface only, which facilitated easy inspection by a process of flipping them out of the water into an upside-down position. This portion of the FHL dock is orientated with its long axis parallel to shore. Floating docks provide a unique biological habitat because, unlike pilings or other fixed structures, their surfaces rise and fall with the tide. They therefore provide a habitat very near the surface for benthic sub-tidal species that normally live only at much greater depths. It is important to understand the nature of these physical conditions, for they determine the sorts of organisms that can live on docks and in other habitats.
Temperatures fluctuate very little in the surface water surrounding most floating docks.
We recorded the temperature continuously for two days on tires both on the inside and outside sections of the FHL dock. Marine organisms living on floating docks are necessarily living very near the surface, and therefore receive a large amount of light. Many species of algae take advantage of this resource, and colonize tires in dense mats. Salinity varies little in the water surrounding most floating docks, unless of course there is a nearby freshwater stream. Water near the surface is constantly refreshed by local currents and there is no opportunity for evaporation or other processes to create local differences in salinity.