biomes 2 (19) Flashcards
What influences primary productivity in the ocean? How does it differ from terrestrial biomes?
1 - Availability of nutrients (N, P, Fe, Si)
2 - Amount of sunlight
Terrestrial biomes are affected by temperature, precipitation, and seasonality.
Explain how the thermocline affects productivity in tropical oceans.
Warm water floats and remains on the top whereas cold water is dense and sinks.
The warmer waters, at first, have a lot of nutrients because of high photosynthesis rates, but they are all sucked up. so, the surface water is nutrient-depleted.
The cold, deep water is nutrient-rich.
Describe the productivity in temperate oceans based on the seasons.
Seasonality helps mixing to occur.
Winter: short days, little light – low productivity.
Spring – phytoplankton bloom, but quickly uses up the nutrients and then low productivity. Not a full thermocline, but mixing is still occurring.
Summer – strong thermocline means that when nutrients are used up, there is low productivity. Warm but strong thermocline, keeping the cold nutrient-rich water below.
Fall – thermocline breaks down, bringing nutrients up from below, so we have a short-lived phytoplankton bloom.
Compare the productivity of polar, midlatitude, and tropical ocean regions.
Polar regions have an extremely high rate of productivity during the summertime.
Tropical regions have a steady, low rate of productivity year-round.
Middle-latitude regions have a large peak in productivity during the spring and a lesser peak in productivity during the fall. Middle-latitude oceans have the highest yearly phytoplankton productivity.
What are the marine biomes and how are they distributed?
1- Divide ocean into zones by light availability: Euphotic, photic and aphotic.
2- Divide ocean into zones by water depth: Pelagic, benthic, abyssal.
3- Divide ocean into zones by distance from land: Intertidal, neritic (continental shelf), oceanic.
Describe the different zones of light availability.
Euphotic zone: topmost part of the ocean where light is strongest. Where nearly all of primary production from photosynthesis occurs.
Photic zone: upper part of the ocean where light penetrates.
Aphotic zone: lower part of the ocean where very little or no light penetrates:
* No living plants
* High pressure, low temperatures
* Animals survive by eating detritus
or other animals
* Must adapt to living with no light
Explain the NPP patterns in the ocean.
Euphotic: NPP in euphotic is limited by nutrient availability; NPP is, therefore, lower in the open ocean (relative to shore) b/c nutrients are low.
As light is reduced in deeper waters, photosynthesis is restricted.
At the bottom of the euphoric zone, respiration equals photosynthesis.
Describe the different zones of water depth.
Pelagic: = open ocean of any depth.
Benthic: any sea bottom surface
* Low oxygenation of water
* Low temperatures
* Animals here feed on detritus or other animals
* Little or no plant life (depending on water depth)
Abyssal: subdivision of benthic zone
* Floor of the deepest parts of the ocean
* Incredible water pressure
* Absolutely no light
* Very cold temperatures
* Hard to survive
What does depth determine?
Depth is a key factor determining the distribution of the dominant marine biomes:
1- Light intensity: photic zone = high light; photosynthesis > respiration
2- Temperature
3- O2 concentration: depends on temperature and balance between photosynthesis and respiration
4- Pressure
5- Nutrient concentrations: atmospheric input at surface; nutrients consumed and tied up in organisms near the surface, released in aphotic zone by bacterial decomposition.
Explain how depth affects nutrient availability.
Organic matter, high near the surface, is depleted and nutrient concentrations are enriched with increasing depth. When things die, it sinks but gets grabbed by things on their way down.
Oxygen high at depth due to deep current sources and low temperature (recall the ‘conveyor belt’).
Upwelling along continental margins brings these nutrient-rich waters into the photic zone; high nutrients, oxygen, and light support high productivity.
How does depth affect light/temperature, salinity/density, nitrates/carbon, and oxygen.
Light/temperature: decreases with depth.
Salinity/density: increases with depth.
Nitrates/carbon: increase with depth.
Oxegen: At first decrease, then rises.
What does distance from land determine?
Input of nutrients to photic zone:
* Nutrients in airborne dust
* Nutrients from rivers and estuaries
* Nutrients from coastal upwelling
At the coast, there are a lot of nutrients. There are also nutrient upwellings: nutrient-rich waters coming to the coast.
Describe the different zones of distance from land.
Intertidal: where land and ocean overlap
* Abundant sunlight
* Constant wave action supplies nutrients and oxygen.
* Food is abundant.
* Varied substrate provides hiding places and surfaces to cling to.
Neritic (continental shelf): seaward from the low tide line, the continental shelf out to the shelf break.
* Well-oxygenated water
* Low water pressure
* Stable temperature and salinity levels
* Home to photosynthetic life
Oceanic: beyond the continental shelf
* Larger creatures
* Life decreases with increasing depth
* Widest array of life (because it is a very broad area)
What is upwelling?
Process in which deep, cold water rises toward the surface.
Winds blowing across the ocean surface push water away- cold water rich in nutrients rises to replace the water that was pushed away.
What are the perks of life in the intertidal zone?
- Abundant sunlight
- Abundant nutrients and oxygen (waves, proximity to land)
- Varied substrate for hiding places and surfaces to cling to
