Quantifying “wave exposure”: a simple device for recording maximum velocity and results of its use at several field sites

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Abstract

Numerous studies have established that exposure to wave action can affect all aspects of the life history of a marine organism, and can thereby have an important role in the structuring of marine populations and communities. However, relatively few studies have attempted to quantify the aspect of water motion that is likely to be of interest. In many cases, an important source of disturbance or mortality is due to the hydrodynamic forces generated by moving water. As a result, the maximum water velocity to which an organism is exposed will determine whether 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 conditions 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 three intertidal habitats on the central coast of California. The correlation of these measurements with qualitative descriptions of each site is discussed.

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