AQA A Level Environmental Science
Biological Resources - Fishing and
Aquaculture 2024 Exam Review
marine productivity: oceans - Answer>> - cover 70% of the
Earth's surface
- only small proportion is biologically productive
- limiting factors restrict the growth of the most important
photoautotrophic organisms
marine productivity: phosphates - Answer>> - most important
limiting factor for algal growth
- ms available for biological productivity where upwellings, ocean
currents and coastal inputs increase supplies near the sea
surface
- slow process due to the time spent in sedimentary rock at the
bottom of the ocean
- theres no gaseous state so slow transport
- low water solubility
marine productivity: upwelling - Answer>> - ocean productivity
is highest in zones where upwelling occurs
- dead organic matter in the ocean tends to be denser than water
and sinks to the bottom of the ocean
- decomposition causes nutrients to accumulate in this cold, deep
water
- strong off shore winds blow across the ocean surface push
water away
- water irses from beneath the surfcae to replace the water that
was pushed away
vital for bringing nutrients back to the surface
- can occur in open oceans where deep water is forced up over
seamounts
, marine productivity: coastal areas - Answer>> - more
productive than the open ocean:
1. upwelling tends to be strongest at the coast (continental shelf
creates a ramp up which upwelling occurs)
2. rivers will pick up nutrients from runoff/leaching and carry them
into the sea which in turn fertilisers algal growth
marine productivity: variations in light levels: photic/aphotic zones
- Answer>> - light needed for photosynthesis
- light can penetrate through the photic zone
marine productivity: temperature - Answer>> - sunlight
penetration will influence the temperature of the ocean at
increasing depth
- highest temperature is in the photic zone
- temperature drops very rapidly
- higher temperature increase enzyme activity and promote
productivity
- warmer water is less dense and tends to float on the colder,
denser water below -- prevents nutrient mixing
tropical oceans - Answer>> -productivity limited in many areas
by lack of nutrients due to wind pattern influencing upwelling
- limiting factor is the nutrients
- lower biomass
temperate oceans - Answer>> - light intensity, water
temperatures and nutrient availability limiting
- summer brings higher light intensity and water temperatures
- seasons
- warmer seasons higher biomass
- increase in temperature and light intensity
- built up in nutrients
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