The responses of freshwater macroinvertebrates to different wavelengths in submerged aquatic light traps

Abstract

A variety of lentic, freshwater habitats in Texas were sampled using six aquatic light traps, each with a different colored cyalume lightstick. Initially, a control trap was used without a lightstick to show that the macroinvertebrates were not attracted to the traps at random, but to the lights inside them. The colors used were red, green, yellow, blue, orange, and white. All tests were initiated 30 minutes after sunset and lasted for four hours. Statistical analyses indicated that eight macroinvertebrate taxa were significantly more attracted to certain wavelengths of light, and that the green and yellow lightsticks attracted more individual macroinvertebrates than the other colors. Tests also were conducted using water samples and organisms from a single site. Water from a pond on the Range Science area of Texas A&M University was used in this second experiment to test in the laboratory, the responses of macroinvertebrates from one location to different wavelengths of light underwater. Ten trials were performed in a man-made tank using the same lightstick colors at the same times as the field experiment. Some of the macroinvertebrate families were significantly not attracted to any light, but some families were attracted to the green and yellow lightsticks more than any of the other colors. Of the taxa that were attracted to specific wavelengths of light, virtually all were attracted to many wavelengths of light. These taxa were caught in traps with any one of the six colors significantly more times than they were caught in the traps without a lightstick in it. Many different taxa were attracted to red lightsticks much less often than would be expected if the organisms were swimming into the traps at random.