Lecture 10

Question 1

Ocean facts

Answer 1

• Salinity varies from 21-39ppt
• Covers 70% of earth’s surface layers

Question 2

Epipelagic layer

Answer 2

• most life
• Phytoplankton based
• 0-200m

Question 3

Mesopelagic

Answer 3

• The “Twilight zone” 600m

Question 4

Bathypelagic zone

Answer 4

• Eternal darkness,
• Sharp reduction in biomass

Question 5

Abyssopelagic layer

Answer 5

• Colourless inhabitants with no eyyes

Question 6

Zooplankton in oceans

Answer 6

• Marine zooplankton are more diverse and can be larger
• Krill are key species

Question 7

Ocean currents

Answer 7

• Critical for maintaining ecosystems
• Driven by wind and Coriolis effect which forces water; clockwise in northern hemisphere and anti-clockwise in southern hemisphere

Question 8

Antartic Circumpolar current

Answer 8

• Largest current
• 0.5ms
• Keeps warm water awat and allows antartica to maintain large ice sheet

Question 9

Gulfstream

Answer 9

• Most important for UK
• 2-3ms
• Brings warm water carribean water that makes UK warmer and milder than other locations at same latitudes

Question 10

Upwelling

Answer 10

• Deep cold water is high in nutrients
• Driven by coriolilis, currents and wind

Question 11

Ocean productivity

Answer 11

• Varies more over space than time
• Feasts in hotspots, famines everywhere else
• seasonality much less important

Question 12

Limit

Answer 12

• Oceans ten to be n- and fe-limited

Question 13

Iron fertilisation

Answer 13

• As productivity is fe-limited, adding iron will create a algal bloom
• Algal will die, taking carbon to the bottom of the ocean
• However, this will only have a positive short-term effect
• It might lead to O2 saturation depletion

Question 14

Five major impacts of climate change on aqautic habitats

Answer 14

• Sea level rise
• Changes in currents/circulation
• acidification
• Precipitation changes
• Direct impacts of heat on organsms

Question 15

How much is sea level rising?

Answer 15

3.4mm a year

Question 16

What is driving sea level rise?

Answer 16

• thermal expansion
• melting of polar glaciers
• Ground water extraction

Question 17

Saltmarshes role

Answer 17

• Reduces coastal flooding
• Vegetation reduces wave height and speed

Question 18

Aqautic Meridional overturning circulation (AMOC)

Answer 18

• A system of shoow and deep ocean currents that include the gulf stream
• LArge carbon ink 0.7GtC
• Sensitive functions of temp and salinity disturbation

Question 19

What might happen to AMOC?

Answer 19

• May slow down (5-15% over the past 5-200 years)
• Very likely to decline but unlikely to collaspe by 2100

Question 20

What % do oceans absorb from CO2 emissions?

Answer 20

30%

Question 21

Ocean acidification

Answer 21

• Threatens calcifying organisms
• Slows growth of coral reefs

Question 22

Freshwater acidification

Answer 22

• May cope better as many freshwater species have evolved higher pH tolerances
• May cope worse as freshwater chemistry is more viariable and pH more sensitive to changes. AMny calcified species

Question 23

How populations mitigate to warming

Answer 23

• Shift range poleward (migration in freshwater habitats maty be hard due to poor connectivity)
• Shift timing (phenology), mainly freshwater

Question 24

Precipitation changes

Answer 24

• Average flows or standing water levels
• Frequency, timing and severity of floods and droughts