Couplings of watersheds and coastal waters: Sources and consequences of nutrient enrichment in Waquoit Bay, Massachusetts
- Boston Univ. Marine Program, Woods Hole, MA (United States)
- Smith College, Northampton, MA (United States)
- Hampshire College, Amherst, MA (United States)
- Boston Univ., MA (United States)
Human activities on coastal watersheds provide the major sources of nutrients entering shallow coastal ecosystems. Nutrient loadings from watersheds alter structure and function of receiving aquatic ecosystems. To investigate this coupling of land to marine systems, a series of subwatersheds of Waquoit Bay differing in degree of urbanization and with widely different nutrient loading rates was studied. The subwatersheds differ in septic tanks numbers and forest acreage. Ground water is the major mechanism that transports nutrients to coastal waters. Some attenuation of nutrient concentrations within the aquifer or at the sediment-water interface, but significant increases in the nutrient content of groundwater arriving at the shore's edge are in urbanized areas. The groundwater flows through the sediment-water boundary, and sufficient groundwater-borne nutrients (nitrogen in particular) traverse the sediment-water boundary to cause significant changes in the aquatic ecosystem. These loading-dependent alterations include increased nutrients in water, greater primary production by phytoplankton, and increased macroalgal biomass and growth. The increased macroalgal biomass dominates the bay ecosystem through second- or third-order effects such as alterations of nutrient status of water columns and increasing frequency of anoxic events. The increases in seaweeds have decreased the areas covered by eelgrass habitats. The change in habitat type, plus the increased frequency of anoxic events, change the composition of the benthic fauna. The importance of bottom-up control in shallow coastal food webs is evident. The coupling of land to sea by groundwater-borne nutrient transport is mediated by a complex series of steps, making it unlikely to find a one-to-one relation between land use and conditions in the aquatic ecosystem. Appropriate models may provide a way to deal with the complexities of the coupling. 22 refs., 14 figs., 5 tabs.
- OSTI ID:
- 6449376
- Journal Information:
- Estuaries; (United States), Vol. 15:4; ISSN 0160-8347
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
COASTAL WATERS
NUTRIENTS
WATER POLLUTION
BIOLOGICAL EFFECTS
WATERSHEDS
AQUATIC ECOSYSTEMS
BIOMASS
ECOLOGICAL CONCENTRATION
ENRICHMENT
FORESTS
HABITAT
LAND USE
MASSACHUSETTS
NITROGEN
PHYTOPLANKTON
SEAWEEDS
SEWAGE
AQUATIC ORGANISMS
DEVELOPED COUNTRIES
ECOSYSTEMS
ELEMENTS
ENERGY SOURCES
NONMETALS
NORTH AMERICA
PLANKTON
PLANTS
POLLUTION
RENEWABLE ENERGY SOURCES
SURFACE WATERS
USA
WASTES
540320* - Environment
Aquatic- Chemicals Monitoring & Transport- (1990-)
560300 - Chemicals Metabolism & Toxicology