||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.
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.