Salinity Intrusion and Seasonal Water Quality Variations in the Tidal ...

· Sediment in urban streams is associated with higher frequencies ofoccurrence ofDDT,
chlordane and dieldrin
· Volatile organic compounds used in plastics cleaning solvents gasoline and industrial
operations occur widely in shallow ground water
· Concentration of selected trace elements such as cadmium, lead, zinc and mercury are
elevated above background levels in populated urban settings
· Sediment cores indicate that zinc and PAHs are on the rise apparently due to increased
motor vehicletraffic.
-Toxic compounds found in stream bed were also found in fish tissue
- Deteriorated water quality and sediment as well as habitat disturbances contribute to
degraded biological communities in urban streams.
1.S Emuent load and water quality
The import of organic matter, especially in estuaries, can lead to water quality
problems. Organic matter input from sewage was historically a major source of organic
carbon that drove aquatic systems toward dissolved oxygen deficiency through direct
microbial heterotrophic activity (Capper et al, 1983). However, the input of nutrients,
whether in organic form followed by recycling or inorganic form with direct nutrient
intake, is what stimulates potential phytoplankton biomass production and this organic
matter may contributeto symptoms ofnutrient over enrichment .
Ecological responses to nutrient enrichment may be quantitatively related to
nutrient load rather than complexity in physical transport and mixing. The relationship
between N load and sea grass recovery in Tampa Bay, Florida, is an example of where
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