Additional Informational Resources of Mount Desert Island, Maine
Streams	Bays	Gulf of Maine	Coastal Zone

Once in the ocean, fresh water shares its burden of nutrients and salts picked up on its travels through the land with marine forms of life. First with estuarine life in sheltered inlets where it meets and mixes with salt water, creating habitats combining the best and worst of both worlds. "Best" in the sense of nutrient rich, with fresh water nutrients adding to those borne on the tide. "Worst" in the sense of becoming brackish, then salty, benefitting only plants and animals that can endure in an environment that is 3.5% salt. Which salt-marsh grass can, and eelgrass, along with numerous forms of plankton and algae. Plus clams, mussels, scallops, oysters, whelks, crabs, lobsters, and much of the other fare of restaurants alongshore.

Estuaries favor plants and animals that can tolerate fluctuating levels of salinity. Depending on the influx of fresh and salt water, and on the shape of the basin where they mix, estuarine life is immersed in water cycling between extremes of fresh and marine conditions. Salt-marsh grass, for example, has evolved several strategies for keeping and removing excess salt from its tissue, allowing it to thrive in settings that are toxic to most other species. Bacteria thrive on decaying marsh grass, and a host of estuarine creatures--including filter-feeding mollusks--feed on those bacteria, consuming a diet that can be almost 25% protein. Fish, eels, ducks, geese, gulls, herons, hawks, eagles, otters, minks, raccoons, and many other species occupy higher niches on the estuarine food pyramid, making a good living from conditions prevailing where fresh water mixes with salt. Estuaries serve as nursery grounds for a great many species that spend their mature years in the Gulf of Maine and North Atlantic.

Besides having enriched nutrient supplies and varying salinity, estuarine waters are generally shallow, sheltered from crashing waves, sunny, and superheated. As a result they are bountiful habitats in the transition zone between Earth's continents and its predominating oceans. Phytoplankton, buoyant algae too small to see with the naked eye, thrive in such places. Zooplankton, minute animals in the same zone, browse on the abundant phytoplankton near the surface where nutrients, sunlight, and warmer temperatures come together, laying the foundation of the marine food pyramid on which life in the ocean depends.

ESTUARY--think S-tuary