Invaders of the Coast: Biological Pollution in Coastal Ecosystems
Brookline, MA
2016, Senior, Creative Writing
After an hour-and-a-half of trains, buses, and ferries, I stepped off the boat on to Thompson Island ready to start the day. Boston Harbor was bright, with greenblue waters waving to greet my sleepy eyes. My bluegreen shirt shimmered back in the wind as I went to meet my supervisors and crew as the boat grumbled back to greet more on the mainland.
The Green Ambassadors Program was aptly named. While we were not bureaucrats or politicians, we were the diplomats between our island salt marsh and the invasive species from Australia, Japan, and Europe. I loved my job: some low tides we would plant clam beds, protecting them against green crabs, and our afternoons were spent chopping down fields of Phragmites australis, stressing them to dissuade them from returning the next year. Walking towards the marsh to start work, I used the clippers to scratch the wounds on my legs, courtesy of Phragmites during battle for the marsh.
Looking out onto the marsh, it was clear that the bamboo-like Phragmitesdominated the land, sand, and water that it touched. From marsh to beach it stretched, seeping its way onto the shore and into the water, with only a few stalks of native cattails remaining on the opposite bank. The stalks towered twenty feet above us and clutched tightly to blocks of Styrofoam and old pieces of defeated boat. Still, these invasives have a bigger impact than aesthetic domination.
Biological pollution is one of the biggest threats to aquatic species. Preying on stressed ecosystems, they sneak in through our ships’ ballast, our wood, our aircraft; stowaways on a world conquest that ends with only them as the victor. Invasive species decimate the native population in the niche that they compete in and cause economic losses and human health hazards. While many invasives used for agriculture and wood production can be beneficial, invasives such as Phragmites australis have few predators or real competitors to keep them from destroying the new ecosystem they call home. Approximately 40% of endangered species are in their decline because of invasive species, and 2/3 of fish extinctions are due to invasives like Phragmites. Causing over $16 million in economic cost per hour, biological pollution is not just a problem for treehuggers and whales, but for the average person and their big business bosses as well.
The cattails on the opposite bank are native, and have always been there to coexist and give back to the environment that they live in. But the Phragmites are invasive, replacing nearly all native Phragmites in the U.S., and pushing native grasses and cattails out of my Thompson Island marsh. Invasive strains of Phragmites hail from Europe, outcompeting the native species and reproducing rapidly to take over entire marshes. While ecosystem services and bug biodiversity are largely unaffected by this swamp bamboo, invasive Phragmites reduce overall biodiversity, change the habitat, outcompete native plants, and displaces the resting, feeding, and breeding habits of birds. With 80% of Gulf and Atlantic wetlands susceptible to Phragmites invasion, it is a problem to worry about. When it dies, Phragmites decomposes slowly and leaves little nutrients. As it grows, marshes fill in, causing habitat loss. It grows, bringing destruction and leaves no legacy but empty husks. Phragmites and other similar invasive reeds concentrate metals in their leaves, leaving behind toxic plant matter on the surface of the wetland. Phragmites tore at my skin as I cut it down, and tore at the marsh as it grew taller.
Invasive green crabs are no better. Originally from Europe, they have taken over beaches and coastal wetlands of both coasts of the United States (Grosholz). The green crab preys on bivalves and other prey at a higher rate compared to the native rock crab, outcompeting them and becoming a new predator to existing species. Against native juvenile lobsters, invasive green crabs were able to secure and defend food sources against much larger lobsters, showing that they have the ability to outcompete Boston Harbor’s mascot crustacean. Bivalves are important to retain water quality, and the lobster and bivalve fishermen would not be happy to find their crustaceans replaced by the green crab. The shellfish industry is a $270 million industry providing 3,200 jobs across American coasts (NOAA Fisheries Service). Green crabs’ predation on bivalves has shown to significantly reduce bivalve population in certain harbors, and could affect the yield and lives of shellfishermen and their families on both coasts. Green crabs even affect the birds in the sky, as predation on benthic invertebrates impacts far enough up the trophic levels to affect even shorebird populations.
Healthy coastal ecosystems are good for economic and environmental health. They provide ecosystem services such as enhancement of water quality and sediment stabilization, as well as protection from coastal erosion, storm damage, flooding, and the filtering of pollutants. Salt marshes and their flora provide a key habitat for young fish as protected nurseries, and unhealthy nurseries would spell disaster for the fishermen who rely on steady growth of fisheries. Fishing is a $199 billion industry, employing 1.7 million people across America. These ecosystem services of providing habitat for fish, preventing flooding and flood damage, cleaning water, and providing scenic recreation areas are at risk because of the introduction of biological pollution. As marshes fill in with the growth of Phragmites and bivalve population decline as green crabs thrive, the economic costs to the fishing and shellfish industry alone would be in the billions, with millions without a job if these coastal ecosystems suffered from habitat loss and a reduction in biodiversity.
Biological pollution such as phragmites and invasive species can be dealt with. We have the ability and resources to treat invasive species the same as other pollution through removal and legislature. While these invasives are an increased risk as global warming persists (Williams 2008), herbicide, hand removal, and mulching of marshes with phragmites seasonally effective, and once phragmites was removed, species richness and composition returned to levels more similar to unaffected phragmites plots. Biological pollution is pervasive, widespread, and deadly, but can be dealt with through programs like the Green Ambassadors.
Standing in the marsh, my boots squished over sharp stalks, cut down by our troop and their shears. Our shins were scratched from the sharp browngreen corpses of Phragmites as we walked from the marsh to the mudflats. Now low tide, we showered the bay with thousands of tiny clams, their hundredsquare foot homes covered by protective netting. At each of the eight plots, we first raked before seeding, expelling the green crabs from each plot and smiting them with our shovels and hands. Burying the edges of the protective nets, the next low tide they were completely submerged in sand, the green crabs shut off from their bivalve prey.
As I stepped off the Island, it was high tide. The orange sun was low over the whitecaps, and the shipping vessels cast a long shadow on the water as we went by. Although I was proud of the work I did, I knew how insignificant that acre of slain Phragmites is compared to all of the invasives on the East Coast alone. I rubbed my feet after taking off the rain boots I wore in the marsh, and felt myself wince remembering that the same stand may grow back next summer. My hands were rough, my ears sunburned, and my body tired as I watched the ballast water of a ship fall into the bay, and I shuttered as I thought of the damage and work that may come from that foreign spill.
Reflection
Reflection
I worked on Thompson Island in Boston Harbor the summer of 2014 under the National Parks Service and Outward Bound, and this paper is in part my reflection of my experience removing the invasive species Phragmites australis and seeding clams. My inspiration for writing came from my love for these salt marshes, my fear of their being overrun by invasives, and my contempt for that plant after spending hours trying to rid it from what became a beloved marsh. I loved that seasonal job and the outdoor work, and found the difficulty in removing biological pollution; it took a dozen teenagers the summer to chop down the Phragmites that might grow back the next year. My research about Phragmites and my environmental science class helped me understand the greater ecological and economic impacts of coastal biological pollution. I feel that both the impact of invasives and the work that is needed to remove them are important to try to convey to others, and I attempted to do so through this paper. I tried to show that something as trivial as the type of grass in a salt marsh or the crabs on the beach can affect entire industries as well as the beauty and health of the marsh itself, and that the wrong grass can be laborious to remove. I tried to show that the wrong type of grass or crab does not only trouble the hearts of environmentalists, but is a problem that reaches fishermen and businessmen.