Imagine you are kneeling on the bank of a cold glacier-fed stream with your arm in the water taking a grab sample. You are an ecotoxicologist and you are taking samples of the creek because there is concern that a potentially harmful chemical has polluted the water. Biologists studying fish downstream have noticed the fish population is almost entirely mature adults, with very few young fish. The absence of younger fish indicates that the population is not reproducing, which indicates some form of toxicant in the water. You have been asked to investigate the situation, determine a cause, and find a way to reverse the effects.


As an ecotoxicologist, you must find out why the creek's fish have stopped reproducing and if something can be done about it. The first step toward finding these answers is to visit the site itself, both to gather water samples and to see if there is obvious evidence of the cause in the surrounding environment, for example dumped chemical containers or a spill site.


Even when the cause seems apparent, you must investigate a little deeper. You will bring the water samples to the lab for analysis, to get a better idea of the different chemicals present in the water. From the list of chemicals, you will look at each one to see if it is responsible for stopping reproduction.


But you aren't finished once you have found the culprit or culprits; you will also study the mechanism by which the contaminant acts on the fish, which will be the key to reversing its effects. It is also important that you find the source of the toxicant so you can prevent similar incidences in the future. It's a big task, but your specialty is answering the questions of what, how, and where disturbances are in the ecosystem.