Control of Colonial Hydroid Macrofouling by Free-Field Ultrasonic Radiation
DENNIS T. BURTON 1,
LEONARD B. RICHARDSON 1, and
ROBERT J. TAYLOR 2
1 Johns Hopkins University Applied Physics Laboratory, Aquatic Ecology Section, Shady Side, Maryland 20764
2 Johns Hopkins University Applied Physics Laboratory, Laurel, Maryland 20707
Free-field ultrasonic radiation inhibited the feeding of the macrofouling hydroid Garveia franciscana by causing tentacle contraction at the sonic degasification threshold. Within the frequency range of 250 to 2000 kilohertz, the threshold sound intensity (sonic degasification threshold) that caused tentacle contraction was directly proportional to frequency, with the minimum observed being 0.6 watt per square centimeter at 250 kilohertz. A pulse length of 0.2 second and interpulse period of 102 seconds gave the lowest average power required to produce tentacle contraction at a peak pulse sound intensity of 6.2 watts per square centimeter with a frequency of 250 kilohertz. Twenty-four hour exposures to the sound regime caused destruction of the hydranths and regression of tissue in the stolons.
Submitted on November 18, 1983
Accepted on February 13, 1984
