Biological Oceanography Flashcards
What factors affect life in the ocean?
Light, nutrients, temperature, salinity, dissolved gases, pH, pressure
Why is light necessary in marine/aquatic ecosystems?
For photosynthesis of phytoplankton
What is the depth of the Photic zone equivalent to?
The depth in which the photosynthetic active radiation (PAR) is 1% of the surface PAR
What is PAR?
Photosynthetic Active Radiation - the portion of the light spectrum which can be used for photosynthesis
In the open ocean (clear water), what is the limit of the photic zone?
100-200m
At the continental margin, what is the limit of the photic zone?
50-100m
At the mouths of rivers, what is the limit of the photic zone?
Can be less than 50m
What are nutrients needed for in marine/aquatic ecosystems?
Nutrients are required for the production of organic (carbon-based) matter
How does nutrient replenishment occur in coastal areas?
Upwelling and terrestrial runoff
What are the issues with nutrient replenishment in coastal areas?
Eutrophication and harmful algal blooms (HABs)
What is the redfield ratio?
The elemental composition of marine organic matter
C:N:P = 106:16:1
What is often the limiting micronutrient in the ocean?
Iron
Which element had an unlimited supply and can be recycled fast?
Carbon
Which element is abundant but has a large demand and is recycled slowly?
Nitrogen
Which element is in less demand and can be recycled more quickly?
Phosphorous
What is the meaning of a limiting nutrient in marine/aquatic ecycosystems?
A nutrient which is not in the required proportion needed for phytoplankton to grow
Where does iron limit the growth of primary producers?
In the Southern Ocean around Antarctica and elsewhere
What caused an algal bloom in the Gulf of Alaska in 2008
In 2008, Mount Kasatoshi in Alaska erupted, spreading iron dust from volcanic ash far into sea and prompting plankton blooms
What is the mixed temperature layer?
Near the surface where the temperature is roughly that of surface water
What is the thermocline?
Area of rapid temperature transition from upper to deep layer
What is the temperature trend of the deep layer?
Well-mixed and relatively uniform in temperature
What is a pynocline?
Rapid change in density of water as a result of thermocline and halocline together
What do salinity and temperature affect in water?
Density, and hence vertical stratification
What is the halocline?
Zone of rapid change of salinity with increasing depth
Where in the vertical stratification of water are nutrients maximum?
At the bottom of the thermocline
Why are nutrients maximum at the bottom of the thermocline?
Molecular diffusion from the bottom layer and decomposition of organic matter from the top layer
What are the features of polar waters?
- Unstable water column (not densely stratified)
- Mixing with the column - nutrient turnover
- Very high total productivity
- Light limited productivity
What are the features of tropical waters?
- Strong thermocline
- Isolated top water layer - no nutrient penetration
- Low productivity - nutrient limited
- The nitrogen-fixing cyanobacterium Tricodesmium is a major source of N
What is a major source of nitrogen in tropical waters?
The nitrogen-fixing cyanobacterium Trichodesmium
Where are tropical regions?
Near the equator
Which dissolved gases are needed for life in the ocean?
CO2 and O2
Which dissolved gas does not dissolve easily in the ocean?
O2
Which dissolved gas dissolves more easily in the ocean?
CO2
What is the set of processes that transports particulate carbon (POC) to the deep sea and sediments?
The biological carbon pump
Give the process of photosynthesis.
CO2 + H2O -> glucose + oxygen
Give the process of respiration.
Glucose + O2 -> CO2 + H2O
Why is oxygen needed in marine environments?
Necessary for metabolic processes
Where can oxygen be an issue?
In coastal and estuarine ecosystems
What can cause dissolved oxygen (DO) levels to drop?
Increased temperature and salinity
When are DO levels in estuaries lowest?
Late summer
When might oxygen depletion occur?
When plants die and decompose, or when wastewater rich in organic material enters the estuary as biological oxygen demand (BOD) increases as more oxygen is required by bacteria for decomposition
What is the name for severe oxygen depletion?
Hypoxia
What estuaries are less susceptible to hypoxia?
Shallow, well-mixed estuaries
At what depths is oxygen high and low?
- High in deep waters
- Low in shallow waters - used in various biological processes
At what depths are nutrient levels high and low?
Low at surface - in photic zone (taken up by species)
Settling of nutrients at the base of the photic zone
What is the netritic zone?
Spans from the low-tide line to the edge of the continental shelf in oceans
Near coast
What is the oceanic zone?
The part of the open sea or ocean that is not near the coast
What is the pelagic zone?
The water column of the open sea
What are the columns of the pelagic zone, from surface to increasing depths?
Epipelagic (photosynthesis)
Mesopelagic (little light)
Bathypelagic (aphotic) zones
What is the benthic zone?
The ocean bottom, things living in or on the bottom of a body of water
What are the zones of the benthic zone?
Littoral zone - shallow water area between high and low tide
Sublittoral zone - between near shore and edge of continental shelf
- Bathyal zone - seabed on the slopes of continental shelf
- Hadal zone or Abyssal zone - deepest sea bed, trenches and floors
