Quiz 1 Lecture Content

Estuary etymology

Latin, aestuarium - tidal inlet of the sea

aestus - tide

Estuary definition

A semi-enclosed coastal water body in which seawater is diluted with freshwater from land drainage (including lagoons with periodic connections to ocean and hypersaline)

What is the largest estuary in Oregon?

Coos Bay/lower Coos River estuary is the largest estuary solely situated in Oregon.

Ecosystem

An ecosystem consists of all the organisms and the abiotic pools with which they interact.

Ecosystem analysis

seeks to understand factors that regulate pools and fluxes of material and energy through ecological systems.

Materials included in ecosystem analysis

Carbon, water, nitrogen, rock-derived elements such as phosphorus, and novel chemicals such as pesticides or radionuclides that people have added to the environment

Pools

Quantities of materials and energy

Fluxes

Flows of materials and energy

Semi-enclosed estuary options

Permanently semi-enclosed, seasonally semi-enclosed, annually semi-enclosed

East coast estuary cover

80-90% of coast, geologically old; wide continental shelf, extensive salt marshes

West coast estuary cover

10-20% of coast, geologically young; narrow continental shelf, little or no salt marsh, arid in south

Lagoon estuary

In dry seasons, lagoons are closed by sandbar

Positive estuary

Freshwater runoff is greater than evaporation. Denser marine water enters the estuary along the bottom and then gradually vertical mixing with the outgoing surface stream of fresher river water. Main focus.

Negative estuary

Freshwater runoff is less than evaporation. Both seawater and freshwater enter the estuary at the surface. Within the estuary, evaporation produces denser high-salinity water that sinks to the bottom. Rare.

Watershed

An ecosystem where all water runoff drains into a single body of water: inputs into estuary vary based on watershed boundaries.

Estuary input

Estuary can have huge or small input from a huge or small area. Example: Columbia River has highest freshwater inflow on US west coast.

True or false: sediment plumes at the head of estuaries can be viewed from space after a storm.

True: so much sediment travels down rivers that the plumes can be viewable from space.

Mouth of an estuary

Strong tidal currents. Clean sand or rocky shores. Salinity similar to adjacent sea. Where the river meets the sea, can migrate

Head of an estuary

Where freshwater enters the estuary, and river currents predominate. Tidal but very limited salt penetration.

Key characteristics of estuaries

Changes in salinity, sediments, turbidity, high productivity, organic, sinks, essential habitat, heavily used by humans

Salinity in an estuary

can range from less than 1% to over 3.5%, depending on river flow, tides, and proximity to the ocean: spatial and temporal factors

Sediments in an estuary

Decreasing in size order: fine sands, mud, silt, clay

Turbidity in an estuary

Suspended sediments, light attenuation

High productivity of estuaries

Lots of primary and secondary production, and carbon fixation

Organic in an estuary

Decomposing organisms, especially plants and detritus "particulate organic matter"

Estuaries as sinks

Storage of sediment and organics: pools!

True or false: salt water goes further into the river during the rainy season.

False, the dry season results in higher salinity levels up an estuary/river due to lack of freshwater input from rain.

Estuaries comprise what percentage of total area-volume of marine hydrosphere

0.5%

Estuaries as essential habitat

In the life cycle and reproduction (life history) of many marine organisms, such as Dungeness and blue crabs, oysters, and migratory shore birds for stop-over and refueling.

Humans and estuaries

Watersheds and ports for human use: lots of freshwater, protected access to sea, ports of call, industrial opportunities, fertile lands, recreational opportunities, research opportunities.

Why are estuaries highly productive ecosystems?

Nutrient input from river, land, and ocean. Shallow with some mixing: extensive plant production and algal production. Relatively stable production.

Linked populations in estuaries

Changes in population of one species can have trophic cascading Example: Horseshoe crabs and Red Knots (shorebirds) in the Delaware Bay: crabs killed for fisheries and pharmaceutical uses, number of red knots passing through has decreased by 70%.

Anthropogenic impacts to estuaries

Alteration of topography via dredging for navigational purposes and dredge spoil disposal, input of industrial and domestic wastes, pollution due to oil spillages - point source and non-point source, increased rate of freshwater discharge and sediment loads from rivers, deforestation, paving, building on land, effects of water abstraction and flood prevention schemes, reclamation of wetland habitats, stabilization of shorelines and land filling (bulkheads and riprap)

State factor

A condition that affects soil formation; includes mineral type, climate, topography, time, and biotic potential

Research opportunities in estuaries

Understanding stresses due to salinity, low oxygen, pollution, ocean acidification, and sea level rise. Why diversity changes over physical and chemical gradients that exist in estuarine settings and how these may change in the near future. Understanding and responding to human impacts.

Geological history of estuaries

Ephemeral: sedimentary basins that fill-in with time

Longevity: thousands to tens of thousands of years

True or false: estuaries are less abundant now than before due to high sea level stands

False, estuaries are more abundant now due to high sea level stands b/c emergent land margins are less eroded than submerged ones

What factors have impacted formation of estuaries?

Glacial/interglacial changes in sea level, longer time scales, normal vs episodic events

Highstand

The interval of time during one or more cycles of relative sea-level change when sea level is above the edge of the continental shelf in a given area.

Lowstand

The interval of time during one or more cycles of relative sea-level change when sea level is below the edge of the continental shelf in a given area.

Sunken river (valley) estuary

Formed when rising sea levels flood river valleys, broad, shallow basins with gently sloping bottoms. Tributary networks trace former river channels, gradual salinity gradient from freshwater to saltwater. Example is Chesapeake Bay, flooded Susquehanna River valley.

Bar-built estuary

Formed when barrier islands/sandbars enclose coastal waters, trapping river water behind them. Built by waves, long shore drift, and sediment deposition. Shallow, elongated basins with limited tidal exchange. Restricted circulation means high turbidity, variable salinity. Example: Pamlico Sound in North Carolina (created by Outer Banks).

Lagoon estuary

A type of bar built estuary.

Fjord estuary

Formed when glaciers carve deep U-shaped valleys during ice age later flooded by seawater, steep-sided basins with shallow sill at the mouth. Stratified salinity: deeper saltier layers, limited mixing. Sill restricts inward flow of highly saline cold water. Cold, nutrient-rich supporting unique marine life due to higher latitudes and a lot deeper. Sill is where all the rocks got pushed to and leftover from the glacier. Example is Puget Sound.

Tectonic estuary

Formed by crustal subsidence (land sinks) along faults or active plate boundaries. Land sinks, creating a basin that fills with seawater, deep, irregular shape; may form rapidly or gradually. Water mixing by tides and river inflow. Example is San Francisco Bay, downwarping along San Andreas Fault.

Salt-edge estuary

Formed where strong river flow and minimal tidal mixing occur. Freshwater "wedge" flows seaward over denser saltwater, sharp halocline separates surface and bottom layers. Limited vertical mixing, bottom water stays much saltier. Example is Columbia River (spring runoff).

Partially-mixed estuary

Formed where moderate tides and balanced river flow allow partial mixing. Weak halocline, salinity increases with depth. Two-layer circulation: surface flows seaward, bottom flows landward. Salinity varies seasonally with rainfall and tides. Example is Chesapeake Bay.

Well-mixed estuary

Formed where strong tides and weak river flow cause complete vertical mixing. Uniform salinity top to bottom, increases seaward. No halocline, dominated by horizontal salinity gradient. Tidally driven circulation, minimal vertical structure. Example: Delaware Bay.