In winter, the knots come by the thousands to feast on the riches in the intertidal mudflats of the Wash. These medium-size wading birds are rather dull and unprepossessing in appearance, white underneath and sandy on their backs. During the breeding season their plumage turns a rich russet, but this happens in the Canadian Arctic and other colder climes where the birds spend the summer, and we seldom see it. In Britain, knots are more remarkable for their sheer numbers.
Other shorebirds favor different foods and therefore exhibit somewhat different behaviors in relation to the water. Where the knot stays at the edge, the dunlin is happy to wade into the water after its prey. Avocets use their upturned bills to skim very shallow water for rag worms and shrimp. The oystercatcher can break into the harder shells of limpets using its jackhammer of a bill. In the Bay of Fundy, up to 2 million semipalmated sandpipers stop off on their migration to feast on mud shrimp, the location favored because the invertebrates develop earlier there owing to the exceptional tidal range, which in turn guarantees a more reliable food supply.
Pathogens excreted in human feces tend to be the most dangerous. So Rose argues that beaches where human fecal bacteria are most common should be the top priorities for follow-up monitoring and cleanup.
Some studies have shown that a sample of beach sand can contain 10 to 100 times more fecal bacteria (measured as colony units per gram) than a sample of water (measured as colony units per milliliter). That means the sand probably also contains more harmful germs than the water does, according to Helena Solo-Gabriele. She works at the University of Miami in Florida. As an environmental engineer, she studies how contaminants move through the environment and affect human health.
Microbes feast on seaweed, marsh reeds and algae that get stranded on beaches. This debris is called wrack. It provides nutrients, shade, moisture and wind protection for germs. Tides push it up the beach as they rise higher and higher. So wrack tends to accumulate at the high-tide line on a beach.
During extreme high tides, stranded wrack, fecal bacteria and sand may again wash down the beach toward the water. It comes to rest in an area called the intertidal zone. This area, where children often play, is dry during low tide but covered in water at high tide. Eventually, tides may wash bacteria and other microbes from the intertidal beach sand out into shallow coastal water. This risks exposing waders and swimmers to germs. That process happens repeatedly.
The structural characteristics of beaches also can affect exposure to fecal germs. Bacteria tend to concentrate for fairly long periods in calm waters. Where the water turns choppy, waves tend to dilute and spread bacteria. That dilution can lower the risk of infection to swimmers by exposing them to lower levels of germs.
Journal: M.P. Verhougstraete et al. Linking fecal bacteria in rivers to landscape, geochemical, and hydrologic factors and sources at the basin scale. Proceedings of the National Academy of Sciences. Vol. 12, August 18, 2015, p. 10419. doi: 10.1073/pnas.1415836112.
Dogs will also be used in the research of gray whales this season. Deborah Giles of Conservation Canines, a nonprofit organization that trains dogs for use in wildlife research, and her canine-companion, Eba, will be collecting fecal samples from whales to get a closer look at the Salish Sea ecosystem. 076b4e4f54