Acadia National Park - Estuaries

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

Shallow, allowing sunlight to reach flats and shallows where productive plants thrive

Sheltered, providing salt marshes with protection from high energy waves

Saline, freshwater rich in nitrates mixing with salt water rich in phosphates

Sunny, supporting photosynthesis and many plants at the base of the marine food web

Sustained by algae, phytoplankton, eelgrass, and spartina grass

Superheated, warmer waters promoting faster rates of growth in resident species