QUANTIFYING WAVE EXPOSURE - A SIMPLE DEVICE FOR RECORDING MAXIMUM VELOCITY AND RESULTS OF ITS USE AT SEVERAL FIELD SITES

Numerous studies have established that exposure to wave action can aff ect all aspects of the life history of a marine organism, and can ther eby have an important role in the structuring of marine populations an d communities. However, relatively few studies have attempted to quant ify the aspect of water motion that is likely to be of interest. In ma ny cases, an important source of disturbance or mortality is due to th e hydrodynamic forces generated by moving water. As a result, the maxi mum water velocity to which an organism is exposed will determine whet her it can survive in a given environment. Here we describe a maximum velocity recorder that is a modification of the described dynamometer. The device is simple and inexpensive to build and easily deployed in large numbers. A mathematical model is presented that describes the co nditions under which the device provides accurate estimates of maximal water velocity, and when it should be used with caution. A number of recorders were used to quantify maximal daily water velocities at thre e intertidal habitats on the central coast of California, The correlat ion of these measurements with qualitative descriptions of each site i s discussed.