Water Column-Primary Production

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Questions and Answers

Which of the following is a requirement for photosynthesis?

  • Oxygen
  • Carbon Dioxide (correct)
  • Water (correct)
  • Methane

Anoxygenic photosynthesis uses H2O as the electron donor.

False (B)

What is primary production primarily responsible for in an ecosystem?

Main source of energy

In bottom-up control, factors that impact primary production include reduced nutrients, __________, and temperature.

<p>light</p> Signup and view all the answers

Which mechanism is responsible for water mixing and nutrient provision in the photic zone?

<p>Wind-driven vertical transport (C)</p> Signup and view all the answers

Match the following terms related to primary production mechanisms:

<p>Thermocline = Stratification of temperature Nutricline = Stratification of nutrients Euphotic zone = Depth of sufficient light for photosynthesis Upwelling = Nutrient-rich water movement to surface</p> Signup and view all the answers

The euphotic zone is characterized by a lack of light for photosynthesis.

<p>False (B)</p> Signup and view all the answers

Photosynthesis is represented by the chemical equation CO2 + H2O → __________ + O2.

<p>CH2O</p> Signup and view all the answers

What primarily drives the vertical mixing of water in lakes?

<p>Wind-driven vertical transport (C)</p> Signup and view all the answers

Coastal upwelling brings nutrient-poor waters to the surface.

<p>False (B)</p> Signup and view all the answers

Name one area where upwelling occurs due to large-scale ocean circulation.

<p>Equatorial upwelling or Antarctic divergence</p> Signup and view all the answers

Wind-driven upwelling enhances primary production in __________ waters.

<p>nutrient-rich</p> Signup and view all the answers

Match the following upwelling types to their respective characteristics:

<p>Equatorial upwelling = Nutrient-rich phytoplankton stimulation Antarctic divergence = High productivity supported by current deflection Coastal upwelling = Long shore winds converted to offshore winds Tropical stratification = Less productive due to permanent stratification</p> Signup and view all the answers

What effect does the Coriolis force have on ocean currents?

<p>It deflects currents to the right in the Northern Hemisphere and to the left in the Southern Hemisphere. (D)</p> Signup and view all the answers

Tropical waters are more productive than temperate waters due to continuous cooling.

<p>False (B)</p> Signup and view all the answers

What is the outcome of wind-driven coastal upwelling?

<p>Enhanced primary production</p> Signup and view all the answers

What causes the upwelling driven by river runoff in estuaries?

<p>River water, being less saline, rides over ocean saline water (C)</p> Signup and view all the answers

Phytoplankton bloom occurs in winter due to a rise in temperature.

<p>False (B)</p> Signup and view all the answers

What is a pycnocline?

<p>A pycnocline is a layer in a body of water where there is a rapid change in density, often caused by differences in salinity or temperature.</p> Signup and view all the answers

Tidal currents can create __________ that can lead to the mixing of nutrient-rich bottom water.

<p>turbulence</p> Signup and view all the answers

Match the following features with their definitions:

<p>Entrainment = The process of fresh water being drawn into saltwater Meromictic lakes = Lakes that lack complete mixing of water layers Tidal mixing = Mixing caused by the gravitational pull of celestial bodies Pycnocline = A layer where rapid density changes occur due to temperature or salinity</p> Signup and view all the answers

Why might turbidity reduce phytoplankton production in tidally mixed waters?

<p>Turbidity reduces light penetration needed for photosynthesis (A)</p> Signup and view all the answers

Seasonal changes in temperature do not affect the water column's primary production.

<p>False (B)</p> Signup and view all the answers

What effect do strong winds have on the water column?

<p>Strong winds can cause mixing of water layers and disturb the stability of stratified waters.</p> Signup and view all the answers

Flashcards

Autotrophs

Organisms that can produce their own food using energy from the sun or chemicals.

Photosynthesis

The process by which organisms use sunlight to convert carbon dioxide and water into glucose (sugar) and oxygen.

Chemosynthesis

The process by which organisms use energy from chemicals to convert carbon dioxide and water into glucose (sugar) and other compounds.

Primary Production

The main source of energy that supports life in an ecosystem; involves the production of organic matter by organisms.

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Bottom-up Control

A model of ecosystem control where factors directly influencing primary production (like nutrients, light, and temperature) drive the ecosystem.

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Top-down Control

A model of ecosystem control where factors affecting organisms at higher trophic levels (like predators) influence primary production.

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Thermocline

The layer in a body of water where the temperature changes rapidly with depth.

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Nutricline

The layer in a body of water where the nutrient concentration changes rapidly with depth.

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Wind-driven Coastal Upwelling

The process of bringing nutrient-rich water from the depths of the ocean to the surface, fueled by strong winds pushing surface water away from the coast.

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Upwelling driven by Large-Scale Circulation

Upwelling driven by large-scale ocean circulation patterns, where water moves vertically due to the Earth's rotation and wind patterns.

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Water Column

The vertical distribution of water layers in a lake or ocean, characterized by different temperatures and nutrient levels.

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Spring Phytoplankton Bloom

The seasonal increase in phytoplankton growth, particularly during spring, due to increased sunlight and nutrient availability in the water column.

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Meromictic Lakes

Lakes that lack complete mixing between their surface and bottom layers, resulting in distinct water properties and sometimes unique ecosystems.

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Upwelling driven by River Runoff

The process of freshwater from rivers flowing into the ocean and creating a layer on top of saltier seawater, forming a boundary called a pycnocline.

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Pycnocline

A zone in a water body where density changes rapidly with depth, often marking the boundary between layers of different temperatures or salinity.

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Upwelling driven by Tidal Mixing

The process of tides, driven by the gravitational pull of the sun and moon, creating strong currents that mix water layers in estuaries, bringing nutrients to the surface.

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Wind-driven vertical transport/upwelling (lakes)

A process where strong winds over a lake surface push down the thermocline on one side, causing it to rise on the other, leading to vertical water mixing when the winds stop.

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Wind-driven coastal upwelling (oceans)

A process where longshore winds become offshore winds, pushing nutrient-rich water to the surface, increasing primary production due to optimal light and temperatures.

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Upwelling driven by large-scale circulation (oceans)

A process where upwelling occurs in the ocean driven by large-scale circulation patterns, resulting in increased primary production due to nutrient-rich water. Examples include equatorial and Antarctic upwelling.

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Equatorial Upwelling

Upwelling caused by divergence of currents along the equator due to the Coriolis effect. Nutrient-rich water rises, leading to increased phytoplankton production.

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Antarctic Divergence

Upwelling caused by the divergence of currents near the Antarctic coast due to the Coriolis effect. This leads to high productivity at the Antarctic divergence.

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Tropical Water Stratification

Tropical waters are permanently stratified due to lack of seasonal cooling, leading to lower productivity than temperate waters. However, upwelling mechanisms can enhance production.

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Westward flowing currents along the equator

Westward flowing currents along the equator in the Atlantic and Pacific oceans. Coriolis force causes divergence to the right in the north and to the left in the south, resulting in upwelling and increased phytoplankton production.

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Westward and Eastward Currents near Antarctic Coast

These currents flow in opposite directions near the Antarctic coast, creating divergence and upwelling due to the Coriolis effect. This leads to high productivity at the Antarctic divergence.

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Study Notes

Water Column-Primary Production

  • Primary producers are autotrophs
  • Photosynthesis equation: CO2 + H2O → CH2O + O2 (light, pigment)
  • Oxygenic photosynthesis uses H2O as an electron donor
  • Anoxygenic photosynthesis uses H2S as an electron donor
  • Requirements for photosynthesis include carbon dioxide, water, nitrate, phosphate, trace elements, and light
  • Organisms can fix CO2 using chemical energy in reduced environments (chemosynthesis)
  • Primary production is the main energy source in ecosystems

Two-Models of Production and Energy Flux

  • Bottom-up control factors directly impact primary production (e.g., nutrients, light, temperature)
  • Top-down control factors affect organisms higher in the food chain

Bottom-up Control Mechanism of Primary Production

  • Heat: Stratification (heating of surface water) creates a thermocline
  • Light: The level at which 1% of surface light penetrates
  • Nutrients: Stratification also affects nutrient distribution and vertical water mixing can break down stratification

Light

  • Light intensity is the rate at which photons strike a given surface
  • Light intensity varies in time and space
  • Euphotic zone has enough light intensity for photosynthesis
  • Clear oceanic/deep lake photosynthesis extends to approximately 100 meters

Nutrients

  • Nutrient concentration in surface waters affects production
  • Physical processes, like mixing, are important for distributing nutrients
  • Seasonal changes in temperature and wind action can affect mixing
  • Upwelling, driven by various factors such as river runoff, tidal waves, wind, and large-scale ocean circulation, brings nutrient-rich water to the surface

Seasonal Changes in Temperature

  • Seasonal temperature changes (cooling and wind action) lead to phytoplankton blooms in spring and no growth in winter
  • This is common in temperate lakes and oceans (up to 100-200m depth)
  • Local factors influence specific water bodies
  • Meromictic lakes lack complete mixing

Upwelling driven by river runoff-estuaries

  • River water (less saline) rides over ocean saline water
  • A pycnocline can develop when water is relatively calm
  • Surface winds/waves generate waves, progressively continuing into the pycnocline, causing its instability
  • Progressive mixing of fresh and salt water (entrainment) brings salt water upwards and filling the space of the entrained water
  • Bottom water is enriched in nutrients

Upwelling driven by tidal mixing -estuaries

  • Tides are caused by gravitational pull of the sun and moon which cause regular rise/fall of sea level varying by location
  • Estuaries with high tidal ranges have strong currents that run on the rising and falling tide
  • Tidal currents, moving over the bottom create turbulence that can break salinity stratification, resulting in tidally mixed estuaries
  • Nutrient-rich bottom water comes to the surface
  • Turbidity may reduce phytoplankton production in mixed waters compared to stratified waters.

Wind-driven vertical transport/upwelling-lakes

  • Strong winds over lake surfaces blowing in one direction.
  • Thermocline is depressed on one side of the lake, leading to a corresponding rise on the other side, which creates instability
  • When winds cease, the unstable thermocline results in vertical water mixing

Wind-driven coastal upwelling-Oceans

  • Longshore winds are converted into offshore winds.
  • Nutrient-rich waters are brought to the surface, alongside optimal light and temperature conditions
  • Resulting in enhanced primary production

Upwelling driven by large-scale circulation in the ocean.

  • Equatorial upwelling: Tropical waters are stratified and less productive than temperate waters due to the lack of seasonal cooling, though upwelling can enhance production. Coriolis force influences currents
  • Antarctic divergence: Water currents close to the Antarctic coast flow in opposite directions, causing upwelling. Coriolis force deflecting the two currents in opposite directions. This results in upwelling along the Antarctic coast, leading to high productivity associated with Antarctic divergence.

Conclusion

  • Lakes and oceans can be seasonally or permanently stratified
  • Supply of nutrients in the photic zone or the well-lit zone is sometimes reduced
  • Breakdown of thermocline and vertical transport of water results in nutrient-rich water coming to the surface.
  • Understanding mechanisms helps to understand the broad-scale distribution of production zones in open water.

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