A pond is a rich ecosystem, full of nutrients and life (and lots and lots of beetles). Each pond often has a unique array of species, from plankton to fish?ªeven if it was created by scientists.

    Biologist Jon Chase and his colleagues at Washington University in Saint Louis had noted that it was nigh impossible to make the ecosystems in 300 gallon plastic pools exactly the same?ªeven if all the starting conditions were identical. So he spent seven years trying to figure out why.

    They seeded 45 such pools in the summer of 2002, and let nature take its course. Neighboring plankton species colonized one tank via the wind but not another. Dragonflies flitted from plastic pond to plastic pond to lay their eggs.

    In the end, each nutrient-rich pond was different from every other. That was determined largely by specific events in each ponds' history, such as the order in which species were introduced. Randomness trumped the scientists' effort.

    That means restoring an ecosystem?ªwhether a pond or an entire coastline?ªis no easy task. One random event, like the recent Gulf oil spill, will be written into the tissue and shell of Gulf sea life and marshes for decades to come.