Estuaries and Coastal Ecosystems

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Questions and Answers

What defines an estuary?

A marshy area with no connection to saltwater

A coastal water body where freshwater mixes with saltwater (correct)

A freshwater lake connected to the ocean

A river flowing directly into the ocean

Which of the following characteristics is NOT commonly found in estuaries?

Mangrove forests

Oyster reefs

Salt marshes

Deserts (correct)

Why are estuaries considered economically valuable?

They contain rich mineral deposits

They are solely used for shipping purposes

They support tourism and fishing industries (correct)

They provide a habitat exclusively for marine mammals

How do estuarine plants contribute to environmental health?

By preventing erosion and stabilizing shorelines Signup and view all the answers

What type of wildlife relies on estuaries for survival?

Birds, fish, and marine organisms Signup and view all the answers

Which of the following statements about the ecological function of estuaries is true?

Estuaries perform filtration processes that enhance water quality Signup and view all the answers

What role do wetlands play in relation to estuaries?

They act as natural buffers that absorb floodwaters Signup and view all the answers

Which factor is a primary threat to estuarine ecosystems?

Coastal development and pollution Signup and view all the answers

What is the primary factor controlling the hydrodynamic processes in estuaries?

Freshwater inflows Signup and view all the answers

Which of the following best describes 'salinity' in the context of estuaries?

It indicates the concentration of dissolved salts in water Signup and view all the answers

What characteristic is associated with a highly stratified estuary?

Flow ratio greater than 1.0 Signup and view all the answers

Which process affects water stratification more effectively in estuaries?

Salinity variation Signup and view all the answers

Which statement is true about moderately stratified estuaries?

They lie between highly stratified and vertically mixed estuaries Signup and view all the answers

How does water density change with increasing salinity?

Density increases with increasing salinity Signup and view all the answers

What effect does untreated sewage have on estuaries?

It contributes to nutrient pollution Signup and view all the answers

In the context of estuarine morphology, which factor does NOT contribute to the water flow dynamics?

Surface runoff from lawns Signup and view all the answers

Study Notes

Estuaries and Coastal Modeling

Estuaries are partially enclosed coastal water bodies where freshwater from rivers and streams mixes with saltwater from the ocean
Estuaries act as transition zones between land and sea
Estuaries support unique plant and animal communities adapted to the brackish water environment
Common habitats in estuaries include shallow open waters, freshwater and saltwater marshes, swamps, sandy beaches, mud and sand flats, rocky shores, oyster reefs, mangrove forests, river deltas, tidal pools, and seagrass beds.
Fisheries production and coastal nutrient enrichment, supplied via rivers and estuaries, are positively correlated in many coastal systems

Why Estuaries are Important

Thousands of species of birds, mammals, fish, and other wildlife depend on estuaries for living, feeding, and reproduction
Many commercially important fish species depend on estuaries at some point in their development

Economic Value of Estuaries

Estuaries provide economic benefits for tourism, fisheries, and recreational activities
Protected coastal waters support important public infrastructure like harbors and ports, vital for shipping and transportation

Environmental Services of Estuaries

Estuaries drain from uplands carrying sediments, nutrients, and pollutants to estuaries
Wetlands such as swamps and salt marshes filter out sediments and pollutants, creating cleaner water benefiting both people and marine life
Salt marsh grasses and other estuarine plants prevent erosion and stabilize shorelines
Wetland plants and soils act as natural buffers between land and ocean, absorbing floodwaters and dissipating storm surges, protecting upland habitat and valuable real estate

Threats to Estuaries

Fertilizers or pet waste washing off lawns
Untreated sewage from failing septic tanks
Wastewater discharges from industrial facilities
Sediment from construction sites
Runoff from impervious surfaces like parking lots

Estuarine Morphology

Diagrams illustrating an estuary's structure, including coastal currents, tidal currents, marine circulation, saline circulation, river discharge, and groundwater inflow
Specific diagrams show the salinity differences, wave processes, and tidal processes within an estuary
Facies boundaries exist between estuarine sand bodies and normal marine sediments, and between marine (tidally) influenced and fluvial sediments

Estuarine Characteristics and Hydrodynamics

Primary factors controlling estuarine hydrodynamics: tides and other forcings from open boundaries, freshwater inflows, wind, evaporation/precipitation, heat flux exchanges with the atmosphere, geometry, and topography of the estuary
Salinity is a measure of salt concentration in water (higher values indicate more dissolved salts)
Water density increases with increasing salinity and decreasing temperature (low-salinity water tends to float above denser, colder high-salinity water)
Salinity variation affects estuarine stratification more significantly than temperature variation

Estuarine Circulation

Visual representation of freshwater inflow from rivers and saltwater inflow from the ocean and the resulting pattern of circulation with a null zone

Stratification in Estuaries

Classification of estuaries based on flow ratio, salinity difference, and vertical entrainment
High stratification: flow ratio ≥ 1.0, large salinity difference, and strong vertical entrainment
Moderate stratification: flow ratio <1.0 and ≥0.01, moderate salinity difference, and moderate vertical entrainment
Vertically mixed: flow ratio <0.01, very small salinity difference, and no vertical entrainment

Highly Stratified Estuaries

Flow ratio >1.0, large salinity difference, and strong vertical entrainment
River flow dominates tidal motion, controlling circulation patterns

Moderately Stratified Estuaries

Flow ratio <1.0 and >0.01, moderate salinity difference, and moderate vertical entrainment
Strong tidal flows and large river discharge, resulting in turbulent mixing and vertical exchange between layers

Vertically Mixed Estuaries

Flow ratio <0.01, very small salinity difference, and no vertical entrainment
Strong tidal flow and weak river flow, resulting in complete mixing, uniform salinity distribution throughout the water column; salinity decreases from ocean to river

Flushing Time in an Estuary

Flushing time is the time needed to replace the freshwater in an estuary at the rate of freshwater inflow
Represents the average time to remove a parcel of freshwater from upstream locations
Used in pollutant transport analysis; affected by hydrodynamic, sediment, toxic, and water quality processes.

Estuary as Filters between Land and Sea

Estuaries act as filters, trapping, storing, and recycling sediments, nutrients, and toxic substances from watersheds.
Rivers and runoffs carry sediments and pollutants into estuaries, acting as sinks.
Sediment discharge can be high during periods of abundant sediment transport, leading to depositions of large sediments.
Seawater enhances sediment settling (flocculation).

Damming Impacts

Dams built can reduces sediment loads but may decrease sediment in coastal areas by impacting erosion processes

Estuary Modeling and Engineering Controls

This section focuses on modeling and controlling estuaries.

Estuary Disposal Analysis

Problem about a city disposing waste into an estuarine system, considering freshwater flow rates, ocean and city chloride concentration levels, dispersion coefficients, flow rates and resulting impacts

Case Study: Coastal Modeling

Case study applying machine learning and deep learning to improve estuary salinity prediction, with methods, summaries and important information collected/discussed in the study

Review Questions

Questions regarding estuarine health, environmental models, ML/DL methods, data collected, and key takeaways from the case study

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Description

This quiz explores the vital role of estuaries as transitional zones where freshwater and saltwater mingle. Learn about the unique habitats and diverse species that thrive in these environments, as well as their significant ecological and economic importance. Understand how estuaries contribute to fisheries production and coastal health.