At a coastal aquarium, staff find that a large amount of seaweed has washed into a shallow rock pool. Fig. 1 shows the pool two days later. A layer of decay...
Question 1 Report
At a coastal aquarium, staff find that a large amount of seaweed has washed into a shallow rock pool. Fig. 1 shows the pool two days later. A layer of decaying seaweed lies on the bottom, and small fish are near the surface. Bacteria use oxygen dissolved in the water while they break down the seaweed. The aquarium team measures oxygen using a probe and considers moving the fish. They must avoid adding copper compounds because these could harm other organisms in the pool. The pool is open to the sea only at high tide.
(a) Name the process by which bacteria release energy from the seaweed. [2]
(b) Describe why the fish are near the water surface in Fig. 1. [3]
(c) Explain how a large mass of decaying seaweed can cause fish to die in the pool. [3]
(d) What could staff do immediately to reduce this risk? [2]
Answer Details
(a) Aerobic respiration [2] Bacteria release energy from seaweed by respiration, specifically aerobic respiration because they use dissolved oxygen.
(b) [3] Bacteria use dissolved oxygen while respiring during decay. Oxygen concentration is lower near the decaying seaweed on the bottom. The fish move near the surface, where oxygen enters from the air and its concentration is higher.
(c) [3] A large mass of seaweed provides more material for bacteria to decompose. More bacterial respiration uses more dissolved oxygen. Fish may then be unable to obtain enough oxygen for respiration and can die.
(d) [2] Staff could remove some of the decaying seaweed. They could also aerate or circulate the water, or move the fish to oxygenated water.
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