Solved: **Figure 1: Net primary productivity of selected world biomes (kJ m–2 a–1,... [IB Environmental systems and societies (ESS) (New Syllabus)]

Question

SLPaper 1

Figure 1: Net primary productivity of selected world biomes (kJ m–2 a–1, average)

Identify an ecosystem with an average net primary productivity above 30 000 kJ m–2 a–1, using figure 1.

[1]

Verified

Solution

Estuary/tropical rainforest 1 mark

Estuaries account for only 3 % of global productivity yet are one of the most productive ecosystems.

State one reason why this is the case.

[1]

Verified

Solution

Estuaries have a high nutrient input $\Rightarrow$ from rivers/runoff/upwelling
Estuaries have high light availability $\Rightarrow$ due to shallow waters
Estuaries have a range of habitats/niches $\Rightarrow$ for different species to occupy

1 mark max

Explain why estuaries are highly productive ecosystems.

[3]

Verified

Solution

3 marks max

Mix of saline and fresh water creates different habitats, resulting in greater biodiversity and higher productivity 1 mark
Zonation/range of temperature/salinity leads to greater habitat diversity, allowing for higher productivity 1 mark
Shallow waters receive more light and warmth, promoting primary productivity 1 mark
Tides, river systems, and upwellings bring in nutrients, fueling phytoplankton blooms and primary productivity 1 mark
Mineral/nutrient run-off from surrounding agricultural land and watersheds enters the estuary 1 mark
Rising and falling water levels expose mud flats, providing food sources for shorebirds, increasing secondary productivity 1 mark
Migratory birds and whales stop to feed, temporarily raising secondary productivity 1 mark

Do not accept only 'high biodiversity' or 'large/complex food webs'.