estuarine ecology

Topics: Water, Estuary, River Pages: 2 (344 words) Published: October 12, 2013
Estuarine Ecology
Classification of Estuaries
Classification of estuaries is based on:
Classification based on Geomorphology
Classification based on Water Balance
Classification based on Hydrographic
Classification Based on Geomorphology
Lagoon – oriented parallel to coast, with large fraction of surface area in water, little in marshes; usually shallow (2m depth); wind dominated water mixing; often behind a sand barrier or a coral barrier reed formed during interglacial 80,000 years ago. Fjord – occurs along subduction zones. Formed by glaciers moving seaward, then retreating; a rock bar (sill) is left at the mouth of fjord; as glaciers push rocks down toward the sea, they left a rock pike at mouth as they floated in the sail water. Also, a u-shaped cross-section; the result, after sea-level rise, is a fjord with deeper basin than the sill Classical coastal plain estuaries (drowned river valley) – V-shaped cross-section; shallow: 20m or less; broad flat areas along the sides with marshes; very large in surface area 25 km x 25 km (Delaware Bay) Coastal plain salt-marsh estuary – from NC to Florida on east coast, few major river estuaries. Salt marshes from along low-lying coastal areas; well-defined tidal drainage network (dendritic); formed in a manner similar to lagoons. Tectonically-caused estuaries – caused by faulting, volcanic eruption (San Francisco Bay). Classification Based on Water Balance (Prichard)

Positive estuary – fresh water input from ground water, rivers, rainfall exceeds evaporation (net flow of fresh water into ocean); most estuaries are this type. Negative estuary – evaporation exceeds fresh water input. This can happen in tropical lagoons with little freshwater input (salinity 35 ppt. Hypersaline lagoons Indian river lagoon, 42 ppt has been recorded. Neutral estuary – freshwater input- evaporation. This system is not used much anymore, because a single estuary could go from 1 to 3 to 2 in a year. Classification Based on...
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