Robert Thacker, PH.D., likes working in uncharted waters. When studying the ecology and evolution of sponges, he and his students sometimes stumble upon little-known—or completely unknown—species. Compared to other forms of plant and animal life, sponges have only recently been well documented; biologists are still working to determine exactly what constitutes a species, genus, or family. "There is remarkable diversity among sponges," Thacker says. They exist in a wide array of colors, sizes, and shapes; some subsist simply by filtering particles out of the water, while others are carnivorous, capturing and digesting small crustaceans.

Thacker’s research takes him from the Gulf Coast to Micronesia, where he studies sponges as indicators of the health of coral reefs. "If you have a lot of erosion on land from construction, it can wipe out a sponge population and damage coral reefs," he explains. "These studies make it clear that terrestrial and marine environments are connected."

Thacker is also using sponges as measures of nutrient levels in the water—a major contributor to the overall "health" of a marine environment. He notes that activities on land can dramatically alter these environments. "When land erosion leads to an imbalance of nutrients, it can upset an entire ecosystem," he says.

Sponges are a boon not only to ecologists but also to researchers developing new drugs. "In the past 20 years, scientists who are seeking new pharmaceuticals have started to look at marine environments," says Thacker. "The biggest sources of new drugs from the marine area seem to be sponges." Compounds found in sponges have been discovered to act as anti-cancer, antibiotic, and anti-inflammatory agents. Most notably, the main component of the HIV/AIDS drug AZT is a modified form of a compound found in a Mediterranean sponge. "That particular sponge is unique because, while many species are found teeming with bacteria, this one is almost completely sterile," Thacker says.

Bacteria are a main focus of Thacker’s research, along with other microorganisms and algae that find their homes in sponges. "Some bacteria and algae live symbiotically inside sponges, but other bacteria are pathogens and actively kill sponges," he says. "The larger questions of how any organism lives with bacteria are very intriguing from an evolutionary and ecological standpoint." Answers to those questions are important for both ecological and medical studies, he says, and sponges might provide valuable clues.

"Sponges are comparatively simple to study," he notes. "You don’t have to worry about complex tissues or nerves or blood. If you want to understand how a particular bacterium interacts with an organism, sponges can be a much easier place to start than a mouse."