For more than two centuries, Boston Harbor has been a dumping ground. In 1773, colonists famously dumped shiploads of tea to protest taxes. But in recent decades, the harbor has received less tea and more sewage. In the 1970s, 43 communities sent their wastewater to Boston where it was barely treated before its release into the harbor. The harbor's pollution was so severe that local newspapers dubbed it “The Harbor of Shame” in the 1980s! But nowadays, after almost 25 years of intensive work by government and local organizations, sewage is no longer discharged into Boston Harbor and, as a result, the harbor has made a miraculous recovery.
As a marine biologist for the EPA, I've had the opportunity to see one of the most hopeful signs of that recovery up close. In the early 1980s, one area of the harbor near Logan Airport called Deer Island Flats was known for having industrial chemicals in the bottom sediments and fish with correspondingly high rates of tumors. Today, Deer Island Flats is covered with graceful shoots of eelgrass (a type of seagrass) that form dense meadows akin to green wheat fields growing underwater, swaying in the current.
The presence of eelgrass at Deer Island Flats is noteworthy because scientists routinely use it as an indicator species. It is particularly sensitive to water quality, so scientists interpret its presence as evidence that water quality in that location is good. Deer Island Flats has gone from being grossly polluted to supporting one of the marine environment’s most sensitive species.
The benefits of eelgrass extend well beyond just being an indicator of clean water. Many fish and crustaceans use it as a spawning and nursery habitat. Other sea creatures use it as a refuge from predators, while still others, such as striped bass, use it as a restaurant drive-through, coming in to forage for food with each high tide. Like all plants, eelgrass performs the miracle of photosynthesis, taking in carbon dioxide and with the help of the sun, converting it into simple sugar molecules. Eelgrass growth can be prolific, so the quantities of carbon dioxide converted to sugar can be large. This conversion process has important implications for much larger geochemical processes, such as global climate change and ocean acidification. Thus, the health of our coastal ecosystems is important, not only for the marine animals that may live there, but also for the planet in general.
As I climbed back into the boat, airplanes were landing at the nearby airport—but if you listened very closely you could hear the pleading call of a seagull overhead. And, in my mind, I also imagined I could hear the murmur of eelgrass meadows gently swaying in the water below. The sounds of a healthy harbor.
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