Cities are ecosystems too.

Image by Codi Kozacek/ Circle of Blue Not far from Chesapeake Bay, Gwynns Falls runs through urban Baltimore. The river carries pollutants from sewage, pharmaceuticals, and fertilizers.Click image to enlarge.

This past Tuesday, I arrived in Baltimore as part of the Logan Science Journalism program’s environmental course—a 2-week fellowship based at the Marine Biological Laboratory in Woods Hole, Massachusetts. By Wednesday morning I found myself peering down not into the sunny blue waters of the Pacific, but into the foamy brown swirls of Gwynns Falls.

Not far from its confluence with the Patapsco River and Chesapeake Bay, the river is fast-flowing and trash-ridden. It rushes under a concrete overpass carrying not only bottles and potato chip bags, but also nitrogen and pharmaceuticals and bacteria like fecal coliform. By testing the water in rivers like these, scientists can perform the watershed equivalent of a urinalysis, says Peter Groffman, an ecologist at the Cary Institute of Ecosystem Studies in Millbrook, N.Y. All that ails the greater watershed—sewer leaks, septic tank seepage, and fertilizer runoff, to name a few—ends up here in Gwynns Falls, and eventually in Chesapeake Bay. It is here that researchers hope to see improvements that will translate into a healthier bay.

Image by Codi Kozacek/ Circle of Blue Baltimore Ecosystem Study scientist Shannon LaDeau collects a sample of standing water from a discarded toilet in an abandoned urban lot. Where water collects, so do mosquito larvae. LaDeau and her team are studying which types of mosquitoes—some carry diseases like West Nile virus—are found in the city.Click image to enlarge.

Urban waterways have been channeled, diverted, buried and polluted for centuries, but they have only recently been studied as part of the larger urban ecosystem. Understanding urban ecosystems, and the rivers within them, is becoming increasingly important as climate change alters established patterns of rainfall, floods and temperature. Globally, more people now live in cities than in rural areas, and the United Nations predicts urban populations will reach 5 billion people by 2030. The Baltimore Ecosystem Study, part of the National Science Foundation’s Long-Term Ecological Research (LTER) system, has been looking at how these changing social and biological processes interact since 1997.

Image by Codi Kozacek/ Circle of Blue Science journalism fellow Nick Clark pours a water sample from a stormwater retention pond in the Baltimore suburbs. The Baltimore area is dotted with the ponds, which collect water runoff from parking lots and neighborhoods. Some are left untouched, but others are managed as community assets for recreation. Click image to enlarge.

During our 2-day crash course led by scientists involved with the project, we extracted river samples with giant syringes, collected mosquito larvae from abandoned lots in West Baltimore, and gathered zooplankton—tiny aquatic animals—from stormwater retention ponds. In the lab at Woods Hole we are busy processing these samples. In the coming days we will begin to interpret what they can tell us about the quality of the urban environment, and how human decisions about topics ranging from infrastructure investment to lawn management are altering ecosystem functioning from the leafy “exurbs” on the fringe of a city to the densest, concrete-girded neighborhoods at its center.

Image by Codi Kozacek/ Circle of Blue Science journalism fellow Susan Phillips begins processing water samples from stormwater retention ponds in Baltimore. By running the samples through an extremely fine, glass fiber filter, we collected algae that we later tested for chlorophyll content—an indicator of how much algae is growing in the ponds.Click image to enlarge.

–Codi Kozacek,

Circle of Blue Reporter