 classroom activities   why do we care about mercury  mercury concentrations mapping us mercury emissions the road to toxicity t he objective for the activities in this first unit is to provide students with the key information about mercury and about how mercury moves around in forests ponds and other areas our goal is to give the students the background they need to investigate the amounts of mercury in plants invertebrates fish and people later on we will expect them to consider questions such as would caterpillars have a higher mercury burden than beetles or what is the relationship between fish diet and fish mercury burden in order for the students to be able to work with questions such as these in some way other than blind guessing they need to develop a basic understanding of how mercury gets into their pond field forest stream or other area that they are studying they also need to have a general feel for the factors that need to be present in order for the mercury to change into a form in which it can be absorbed by living things in short the students need a basic understanding of mercury chemistry the students need to understand more than the chemistry of course they also need to understand how bioaccumulation works which means understanding the operation of food chains and food webs we will focus on food chains and food webs in unit 2 here in this first unit our objective is just to introduce the following basic ideas mercury is toxic in very small quantities mercury occurs in a number of forms in nature one of these forms methylmercury can be absorbed by living things and is very toxic in the northeast most mercury arrives through the air methylmercury is the byproduct of metabolism by anaerobic bacteria typically living in an acidic environment with access to carbon and sulfur the essential activity   why do we care about mercury    focuses on the first of these ideas and introduces the second one the optional activity   mercury concentrations  reinforces the second idea and develops the third and fourth ones optional activity  mapping us mercury emissions  helps develop the second idea and  the road to toxicity  develops the last of these ideas  mercury in watersheds background classroom activity  