Lecture 8

Question 1

Nutrient and Sediment Flow

Answer 1

Water column nutrients –> Benthic Organisms and Mangroves –> Nutrients in sediments
Flooding sediments slugs deforestation Strong wave activity - benthic organisms

Question 2

Bacterial Processes

Answer 2

Aerobic = CHO + O2 = CO2 + H2O + energy
Anaerobic = Decreasing energy yield to bacteria 1-3
1) Nitrate reduction: CHO + NO3 = CO2 + NH3 + energy
2) Sulfate reduction: CHO + SO4 = CO2 + H2S + energy
3) Methanogenesis: CHO + CO2 = CO2 + CH4 + energy

Question 3

Mixing Diagram

Answer 3

not total nutrient load, but the DISTRIBUTION of nutrients
Tidal Currents -> Eddies
Waves ->ekman transport
Sediment exchange
Biological destabilisers -> crabs etc
Physical Stabilisers -> heat up from sun

Question 4

Density stratification effect on mixing

Answer 4

Suppresses mixing –> More prone to anoxia

Question 5

Benthic Sediment Seasonal Variation

Answer 5

Summer = Sediment flux from the sediment
Winter = Sediment flux to sediments

Question 6

Estuary Types + Energy Levels

Answer 6

Diagram

Question 7

Estuary vs Delta

Answer 7

Diagram

Question 8

New Zealand

Answer 8

Areas of high addition of nutrients are well mixed. Areas prone to hypoxia
Maketu Estuary = Well mixed and low residence time. Flushed regularly and thus nutrient load doesn’t affect too much.

Question 9

Hydrodynamics of tidally dominated estuaries

Answer 9

• Strong tidal currents
• Little stratification
• Large fringing habitats and intertidal areas
• Very large sediment supplies

Connectivity to shelf = Reliant on the water quality on the shelf
- On-shelf = usually nutrient-poor due to strong influence of El Nino (upwelling = increases nitrate)