Estuarine Tidal Riverine Open Water (Subsystem)

Unique Identifier: 10

System	Estuarine
Subsystem	Estuarine Tidal Riverine Open Water
Tidal Zone	Estuarine Tidal Riverine Open Water Subtidal

Description

Definition

The Estuarine Tidal Riverine Open Water Subsystem includes tidal freshwater areas with a salinity of <0.5 and a depth of greater than 4 meters at MLLW.

The Estuarine Tidal Riverine Open Water Subsystem is the most upstream portion of the estuary and subject to river and watershed influences, including high nutrient and sediment loads and low salinity. Similar to the Estuarine Open Water Subsystem, physical impact from waves and surface currents is reduced interaction at depth. This zone may be the site of the upper limit of the salt wedge and of a turbidity maximum zone, important as feeding and aggregation sites for plankton and benthic species. This zone is also potentially subject to high organic loading and formation of hypoxic waters. Primary production is often low, due to high turbidity and deep, dimly lighted water columns, especially in the river channel. For this reason, the Tidal Riverine Open Water Subsystem may be heterotrophic with net negative metabolic rates.