THE EFFECTS OF TEMPERATURE, LIGHT 



AND EXPOSURE TO SUBLETHAL LEVELS 



OF COPPER ON THE SWIMMING BEHAVIOR 



OF BARNACLE NAUPLII 



William Lang 



Sarah Lawrence 



Don C. Miller 



U.S. Environnnental Research Laboratory 



Narragansett, Rhode Island 02882 



ABSTRACT 



The "Bugsystem" is a computer-television system developed to 

 accurately track and analyze swimming patterns of aquatic organisms. 

 Video images of test animals are converted to time sequence X-Y 

 coordinates to allow rapid computer analysis of linear or angular velocity, 

 rate of change of direction, direction of travel and other parameters. Initial 

 experiments using barnacle nauplii {Balanus amphitrite, B. improvisus, B. 

 venustus, Chthamalus fragilis) indicate larval swimming speeds are affected 

 by temperature and light regime. Response to temperature appears to be a 

 function of species tested and, perhaps, geographic location of the adult 

 population. Changes in linear velocity induced by acute light intensity 

 variation are of short duration. Mean linear velocities of nauplii are altered 

 by 24 hour exposure to copper as low as 20 ppb. Linear velocities of exposed 

 populations increase relative to controls at low copper levels, and then 

 decrease as lethal levels are approached. Copper will also alter the 

 swimming pattern of exposed larvae. 



INTRODUCTION 



In view of concern that bioassays directed solely toward determining lethal 

 concentrations of pollutants may not accurately reflect levels doing harm to 

 the environment, attention has been directed toward sublethal effects of 

 pollutants— "effects which do not immediately, or directly, lead to death, but 

 which nevertheless cause disturbances which may be of ecological significance 

 (1)." Existing studies using pathological, physiological, and behavioral 

 parameters indicate approximate thresholds for sublethal responses are often 

 10-20 percent of LC50 levels or less (7, 22). It is generally recognized that 

 behavioral responses of marine animals are often highly sensitive to stress (18) 

 and that juvenile or larval stages of many marine organisms represent that part 

 of the life-cycle most susceptible to stress (4, 8, 16). Logically, larval 



273 



