External nutrient sources, internal nutrient pools, and phytoplankton production in Chesapeake Bay

Journal Article · Tue Dec 01 04:00:00 EST 1992 · Estuaries; (United States)

DOI:https://doi.org/10.2307/1352393· OSTI ID:6200637

Magnien, R E; Summers, R M ^[1]; Sellner, K G ^[2]

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1. Maryland Department of the Environment, Baltimore (United States)
2. Benedict Estuarine Research Lab., MD (United States)

External nutrient loadings, internal nutrient pools, and phytoplankton production were examined for three major subsystems of the Chesapeake Bay Estuary-the upper Mainstem, the Patuxent Estuary, and the Potomac Estuary-during 1985-1989. The atomic nitrogen to phosphorus ratios (TN:TP) of total loads were 51, 29 and 35, respectively. Most of these loads entered at the head of the estuaries from riverine sources and major wastewater treatment plants. Seven-16% of the nitrogen load entered the head of each estuary as particulate matter in contrast to 48-69% for phosphorus. The difference seems to favor a greater loss of phosphorus than nitrogen through sedimentation and burial. A major storm event in the Potomac watershed greatly increased the particulate fraction of nitrogen and phosphorus and lowered the TN:TP in the river-borne loads and accounted for 11% of the nitrogen and 31% of the phosphorus delivered to the estuary by the Potomac River during the entire 60- month period examined here. Within the Mainstem estuary, salinity dilution plots revealed strong net sources of ammonium and phosphate in the oligohaline to upper mesohaline region. indicating considerable internal recycling of nutrients to surface waters. A net sink of nitrate was indicated during summer. Phytoplankton biomass in the mesohaline Mainstem reached a peak in spring and was relatively constant throughout the other seasons. In the Patuxent and Potomac, the TN:TP ratios of external loads are 2-4 times higher than those observed over the previous two decades. These changes are attributed to point-source phosphorus controls and the likelihood that nitrogen-rich nonpoint source inputs, including contributions from the atmosphere, have increased. These higher N:P ratios now suggest a greater overall potential for phosphorus-limitation rather than nitrogen-limitation of phytoplankton in the areas studied. 66 refs., 6 figs., 7 tabs.

• OSTI ID: 6200637
• Journal Information: Estuaries; (United States), Journal Name: Estuaries; (United States) Vol. 15:4; ISSN ESTUDO; ISSN 0160-8347
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
540320* -- Environment
Aquatic-- Chemicals Monitoring & Transport-- (1990-)
560300 -- Chemicals Metabolism & Toxicology
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
AIR POLLUTION
AQUATIC ORGANISMS
ATLANTIC OCEAN
BAYS
BIOMASS
CHESAPEAKE BAY
COASTAL WATERS
DILUTION
ECOLOGICAL CONCENTRATION
ELEMENTS
ENERGY SOURCES
ESTUARIES
HYDROGEN COMPOUNDS
LIQUID WASTES
MANAGEMENT
NITROGEN
NONMETALS
NUTRIENTS
OXYGEN COMPOUNDS
PHOSPHORUS
PHYTOPLANKTON
PLANKTON
PLANTS
POLLUTION
POTOMAC RIVER
PROCESSING
PRODUCTIVITY
RENEWABLE ENERGY SOURCES
RIVERS
SALINITY
SEAS
SEASONAL VARIATIONS
SEDIMENTATION
STREAMS
SURFACE WATERS
VARIATIONS
WASTE MANAGEMENT
WASTE PROCESSING
WASTE WATER
WASTES
WATER
WATER POLLUTION
ZONES