I am a graduate student attempting to take electrophysiology recordings from a lobster under water. In the current set up I am using, two differential amplifier boards are attached the the lobster's back in waterproof casing, with a transmitter and power source in a float being towed around the water surface.
The amplifier boards function properly for bipolar EMG recordings when the lobster isn't in the water, but once the lobster is submerged with the amplifiers on its back, I pick up very large amounts of sinusoidal 60Hz noise as well as a 60Hz "clicking" noise (see attached image). The sinusoidal 60Hz noise I can filter out post recording, but I haven't found an effective way to remove the clicking noise. Both are drowning out the desired physiological signals.
NOTE: the amplifiers have bandwidths of 200-1000Hz, but no 60Hz notch filters. I've run trials with the reference electrode in the salt water, but also bipolar tests with both electrodes placed in the target muscle tissue.
From what I've read I imagine the salt water is amplifying the ambient 60Hz noise, which causes it to increase in the recording once the amplifier is submerged. However, I'm still trying to figure out what about my circuit may be causing the clicking/clipping 60Hz noise. Please let me know if you have encountered noise like this in the past, and if you have any advice on how to address it!