4.3 Aquatic food production systems Flashcards
What are the zones that the Ocean can be divided into ? (HINT: son 5) (EMBAH – metele tu memorizada con la tecnica Valed)
- Epipelagic zone
- Mesopelagic zone
- Bathypelagic zone
- Abyssalpelagic zone
- Hadalpelagic zone
Epipelagic zone - Depth y facts
- (depth of 0 to 200m): into which light penetrates allowing primary produces to grow
- It is the most productive zone, with little photosynthesis occurring outside this area
Mesopelagic zone - Depth y facts
- (depth of 200m to 1,000m)
- where there is insufficient light penetration to allow for plant growth
Bathypelagic zone - Depth y facts
- (depth of 1,000m to 4,000m):
- also known as the dark zone because of absence of light apart from that produced by any bioluminescent organisms present.
Abyssalpelagic zone - Depth y facts
- (depth of 4,000m to 6,000m)
- is dark and the water temperature is just above freezing.
- Few organisms can withstand the high pressure in this zone
Hadalpelagic zone - Depth y facts
- (depth of more than 6,000m):
- includes trenches and canyons.
- The water again is very cold and life here needs to be adapted to extremely high pressure.
Outline the basics of a marine ecosystem. state an example for each trophic level
- Primary producers :
a. phytoplankton and seaweed - Primary consumers
a. zooplankton - Secondary consumers
a. small predators/small fish (like sardines - Tertiary consumers
a. large fish (sharks)
What is primary production dependent on (in aquatic ecosystems
Primary production is dependent on the amount of sunlight, suitable temperature and available nutrient levels
What nutrients is primary production dependent in
nitrates
phosphates
silicates
What is therman stratification
- Tiny particles, such as nutrients, gradually sink down from the upper layers of the water
- When the weather is calm and warm, the water in a body of water (like a lake or ocean) can separate into layers based on temperature
- This is called thermal stratification
- The thermal stratification stops the nutrients from moving up into the upper layer of the water, which is called the epipelagic zone. This is where many of the organisms that rely on sunlight live
When does thermal stratification occurr
- Sunlight heats the upper layer of water and surface movements create a layer with a fairly consistent temperature
- Water movement below the surface mixed layer is reduced due to the calm weather and the sun continues to warm the water. Sunlight penetration declines with depth resulting in a temperature variation from the top to the bottom of the thermocline
- Strong winds and coastal currents can cause mixing of the water and break up the thermocline and redistribute nutrients back into the water column
- This process is referred to as upwelling, and contributes to an increase in primary production. El Nino events reduce surface current and wind driven upwellings, which has a negative effect on productivity in the area
- In high latitudes during the winter vertical mixing also occurs when the surface waters gets cold and sinks. In the tropics, thermal stratification is fairly stable and production levels tend to be lower but constant
Why are coastal waters more productive
- Coastal waters are typically shallower than open ocean waters, allowing more sunlight to penetrate
- nutrient-rich runoff from the land
What are the zones in lake ecosystems
- Littoral zone
- Limnetic zone
- Euphotic zone
- Profundal zone
- Benthic zone
What is the Littoral zone?
the shallow area of the lake that goes up to the shore area
What is the Limnetic zone?
covers the open water in the lake where there is enough light for phytoplankton to photosynthesize
What is the Euphotic zone?
includes both the littoral and limnetic zone where there is sufficient light for photosynthesis to occur
What is the Profundal zone?
thedeep water where there is no light penetration
What is the Benthic zone?
the lake bottom, where organisms live within the sediments or on thesurface of the lake sediments.
Learn / study diagram of the lake zones!
Mira la foto 6 en el docs
Why aquatic food systems are seen as less productive than terrestrial food systems - STATE ARGUMENT IN FAVOR
- Primary producers in aquatic systemsreceive less light than terrestrial plants because some of the incoming light is absorbed or reflected by the water.
- Compared to terrestrial foods, humans generally tend to eat organisms from higher up in the aquatic food chain.
Why aquatic food systems are seen as less productive than terrestrial food systems - STATE ARGUMENT AGAINST
In aquatic systems less of the biomass may be lost as indigestible skeletal material (e.g. jellyfish have no skeleton) resulting in more efficient energy transfer
How did capture fisheries attempt to meet rising fish demand
- Growth in number and size of fishing fleets
- Improvements in shipping vessels which allowed fishing to occur further from the shore and in deeper waters
- Larger ships allowing for longer periods at sea resulting in greater harvest of fish
- Development of sonar, radar and satellite technology to detect and track schools of fish
- The ability to process, preserve and freeze aquatic produce on the ship whilst still out at sea
State the 3 types of Fishing Nets
- Trawler nets
- Purse - seine nets
- Drift nets
Impact of Trawler nets
- funnel shaped net along the seabed.
- damages sea bed and gets other animals caught
