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Salt marsh productivity with natural and altered tidal circulation
Joy B Zedler1, Ted Winfield1, Phil Williams1
1Department of Biology, San Diego State University, 92182, San Diego, California, USA.
Oecologia
|March 18, 2017
Summary
Altered tidal flow in southern California salt marshes impacts plant productivity. Reduced tidal flow can increase productivity by lowering salinity and retaining nutrients, but lagoon closures may decrease it.
Area of Science:
- Coastal Ecology
- Wetland Science
- Marine Biology
Background:
- Tidal circulation is crucial for salt marsh health and function.
- Altered tidal flow can significantly impact estuarine ecosystems.
- Southern California's salt marshes face various modifications affecting water exchange.
Purpose of the Study:
- To investigate the effects of altered tidal circulation on salt marsh primary productivity in southern California.
- To compare productivity in a well-flushed wetland versus modified wetlands with restricted tidal flow.
- To understand the relationship between tidal exchange, salinity, nutrient retention, and plant productivity.
Main Methods:
- Comparative analysis of three southern California salt marsh sites with differing tidal circulation patterns.
- Measurement of net aerial primary productivity of vascular plants.
- Assessment of tidal exchange, salinity, and freshwater influences.
Main Results:
- The Tijuana Estuary (continuous exchange) showed low vascular plant productivity (0.4-1.0 kg m-2yr-1).
- The Flood Control Channel (restricted flow) also exhibited low productivity (0.6 kg m-2yr-1).
- Los Peñasquitos Lagoon (intermittently blocked) demonstrated high productivity (1.2-2.9 kg m-2yr-1), linked to freshwater impoundment.
Conclusions:
- Eliminating tidal flow during the growing season may enhance vascular plant productivity by reducing soil salinity and retaining nutrients.
- Sand bar obstruction can decrease productivity if it leads to hypersalinity in closed lagoons due to low rainfall.
- Long-term studies and ecosystem-wide examinations are necessary for a comprehensive understanding of altered tidal circulation effects.
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