I've written in the past about our medications finding their way into our waterways, either through our own waste or tipping old medication down the toilet. Our sewage waste water treatment systems often can't filter out pharmacological compounds.
   
A study by researchers of the Portsmouth University in the UK has found anti-depressants can change the behavior of prawns (shrimp) in ways which could conceivably impact on shrimp populations..
   
An abstract of the study is all in that high-fallutin' scientist-type gobbledegook that had me running for a dictionary, but there's quite a few reports that dumb it down a little for we, the comparatively uneducated masses. 
    
According to a related article on New Scientist (a great site for these sort of stories and in plainer English), shrimp were exposed to levels of the antidepressant Prozac similar to the levels found in waste water. The researchers found the crustaceans were five times more likely to swim toward the light instead of away from it, which could make them easy prey for predators. Bear in mind, we eat these critters too.
   
Unfortunately, just stopping dumping old medication down the toilet won't fix this sort of problem, although it's a start. It seems the bulk of the presence of these compounds is just through our not metabolising all of the substances and they simply pass through our bodies, carried out as waste.
   
One of the ways we can decrease this is up to our doctors; some of whom are a little too quick to prescribe psychoactive drugs for depression and anxiety - and even antibiotics for that matter; another concern in aquatic environments.

I understand why they do it and I know that a lot of people need anti-depressants and such; but as someone who scoffed down his fair share of legally prescribed mood altering meds in his younger years and has watched time and again the result of prescription drug abuse, something needs to be done - it's not just an environmental issue. So much human misery can be attributed to our McDonald's approach to medicine these days.
   
The tragic thing is, nature has answers for some people afflicted by depression and anxiety - and I'm not talking about smoking certain "herbs". I mean just being out in it; getting away from the madness we call civilization. It's stories like these that remind me that some of our modern "cures", medicinal or otherwise, are at times only band-aids covering a gangrenous wound and often destroying nature's own powerful medicine in the process.

Related:
 
Seafood and the environment