| Date | May 2018 | Marks available | 4 | Reference code | 18M.2.SL.TZ0.3 |
| Level | Standard Level | Paper | Paper 2 | Time zone | Time zone 0 |
| Command term | Explain | Question number | 3 | Adapted from | N/A |
Question
Figure 3 represents a system of aquaculture with four groups of harvestable species.
Figure 3: Integrated aquaculture
[Source: Adapted from and reprinted with permission from Ocean Conservancy]
Identify one producer in the system illustrated in Figure 3.
Outline one reason why aquaculture production has increased globally.
Describe two negative environmental impacts that may arise from integrated aquaculture.
Explain why this system may cause fewer environmental impacts than systems that farm only fish.
Markscheme
algae/seaweed/sea grass
increased food demand from increasing population/affluence;
health benefits / change of diet preferences;
depletion of marine fisheries / considered more sustainable;
limited arable land for food production;
more economically efficient/profitable;
requires less resources/expertise (boats, fishermen, etc) than wild fisheries;
technology/technological methods have improved.
Award [1 max].
escaped fish impact wild stocks through genetic degradation/disease/competition;
high density populations lead to more disease;
farmed species may consume/displace food species for local populations;
loss/degradation of habitat due to clearance for aquaculture / nets/cages may trap/endanger local species;
introduction of non-native species;
pollution due to use of medication/growth hormones/pesticides.
NB do not credit high nutrients/eutrophication/low diversity/high BOD or any other impacts that integrated agriculture actually limits or reduces (as indicated in responses to question 3(d)).
Award [1] for each correct answer identified, up to [2 max].
polyculture helps maintain biodiversity/complexity/resilience in the environment;
(polyculture) allows for species to recycle wastes of other species;
lobsters/mussels will reduce particles of organic waste/faecal matter/excess feed;
(reduction of particles will) reduce BOD/decomposition and oxygen consumption;
filtration by the mussels will improve water clarity/photosynthesis;
cropping/harvesting algae will prevent build-up of nutrients/eutrophication;
algae will absorb excess CO2 reducing acidification of water;
algae will release oxygen limiting anaerobic conditions;
food is provided naturally from within system/feeds made up from wild populations are not required.
Award [1] for each correct answer identified, up to [4 max].
Examiners report
The vast majority of candidates identified a “producer” in the system.
The great majority identified a valid reason for rise in aquaculture
A good proportion of candidates identified at least one potentially negative impact of aquaculture.
Surprisingly few candidates could suggest more than one (occasionally two) advantages of integrated culture. It was as if they had not registered the 4 marks available and were satisfied once they had given just one possible reason.
