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Cambridge Assessment International Education Cambridge International Advanced Subsidiary and Advanced Level * 0 7 6 4 6 3 1 6 9 4 * MARINE SCIENCE Paper 4 A2 Data-Handling and Free-Response Candidates answer on the Question Paper.

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READ THESE INSTRUCTIONS FIRST 9693/04 May/June 2019 1 hour 15 minutes Write your centre number, candidate number and name on all the work you hand in.

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Section A Answer both questions in this section.

Write your answers in the spaces provided on the Question Paper.

Section B Answer both questions in this section.

Write your answers in the spaces provided on the Question Paper.

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You may lose marks if you do not show your working or if you do not use appropriate units.
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This document consists of 11 printed pages and 5 blank pages.

DC (CE/CB) 164106/3 © UCLES 2019 [Turn over 2 BLANK PAGE 9693/04/M/J/19© UCLES 2019 3 Section A Answer both questions in this section.

1 A marine reserve was set up in an area of the Mediterranean Sea to protect fish stocks.

No fishing was allowed within the reserve.


The mean daily fishing effort in areas surrounding the marine reserve was recorded and is shown in Fig.

1.1.

Fishing effort was measured as the quantity of fishing gear used per square kilometre per day.

land marine reserve i n e l i n g 8 k m s a m p l fishing effort / quantity of fishing gear used per km2 per day marine reserve (no fishing) 26–42 18–25 14–17 10–13 7–9 <7 Fig.
1.1 (a) Suggest and explain one possible reason for the differences in fishing effort surrounding the marine reserve shown in Fig.

1.1.
................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] 9693/04/M/J/19© UCLES 2019[Turn over 4 (b) Scientists assessed the success of the marine reserve in conserving fish stocks.
They measured the number of grouper eggs in different areas of the reserve, and also outside it.

The areas sampled were along an 8 km line, which started in the centre of the reserve.

The sampling line is shown on Fig.

1.1.

The results are shown in Fig.

1.2.

The scientists drew a line of best fit through the data points.
inside marine reserve outside marine reserve grouper egg density / number of eggs per 1000 m3 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0 0 1 2 4 distance from centre of marine reserve / km 5 7 6 3 8 Fig.

1.2 (i) Describe how grouper egg density changes with distance from the centre of the marine reserve.
........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] 9693/04/M/J/19© UCLES 2019 (ii) Use the line of best fit on Fig.
1.2 to calculate the change in grouper egg density per kilometre between the centre of the reserve and a distance of 8 km from the centre.

5 ....................... eggs per 1000 m3 per km [3] (c) Discuss whether the information in Figs.

1.1 and 1.2 could be used to show that the marine reserve is beneficial to fish stocks in and around the reserve.
................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [4] [Total: 11] 9693/04/M/J/19© UCLES 2019[Turn over 6 BLANK PAGE 9693/04/M/J/19© UCLES 2019 7 2 One method used to measure water pollution by organic waste is to calculate the biological oxygen demand, BOD.
This determines the rate at which oxygen is used by micro-organisms in the water.

To determine the BOD of water, a sample of water is taken from the sea or river and the concentration of oxygen is measured.

The sample is then placed in a tube with an airtight seal and kept at 20 °C for five days.

The concentration of oxygen is then measured again.

The fall in oxygen concentration is the BOD.

(a) (i) Suggest why the airtight seals are placed on the tubes.
........................................................................................................................................... ..................................................................................................................................... [1] (ii) Explain why oxygen concentration falls in the tubes.
........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [2] 9693/04/M/J/19© UCLES 2019[Turn over (b) The BOD of an estuary close to an agricultural area in Southeast Asia was measured during each month.
Fertiliser use and rain levels were also monitored.

8 The results are shown in Table 2.1.

Table 2.1 month January February March April May June July August September October November December fertiliser use rain / mm BOD / mg dm–3 low low low high high high high high low low low low 15 20 25 50 310 550 575 590 360 210 75 20 2 2 3 2 8 18 25 25 19 12 8 2 (i) Calculate the percentage increase in BOD between January and August.

Show your working.
Show your working.

............................................................ % [2] 9693/04/M/J/19© UCLES 2019 (ii) Explain the changes in BOD over the year.
9 ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ........................................................................................................................................... ..................................................................................................................................... [4] [Total: 9] 9693/04/M/J/19© UCLES 2019[Turn over 10 Section B Answer both questions in this section.
3 (a) Explain the meaning of the terms osmoconformer and euryhaline.
osmoconformer ......................................................................................................................... ................................................................................................................................................... euryhaline ................................................................................................................................. ................................................................................................................................................... [2] (b) Many marine organisms regulate their water and ion content.
Outline the process of osmoregulation in marine bony fish and explain why this is necessary.
................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [7] 9693/04/M/J/19© UCLES 2019 (c) Discuss the possible ecological impacts of desalination plants on marine ecology.
11 ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [6] [Total: 15] 9693/04/M/J/19© UCLES 2019[Turn over 12 4 Human activity is threatening the marine environment in many ways.
Conservation is becoming increasingly important.

(a) Explain the meaning of the term conservation.
................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [2] (b) Artificial reefs and the release of cultivated stocks are two methods of rehabilitating depleted fish stocks.
Compare the advantages and disadvantages of these methods.
................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [6] 9693/04/M/J/19© UCLES 2019 (c) Explain how ecotourism practices can reduce damage to the marine environment.
13 ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ................................................................................................................................................... ............................................................................................................................................. [7] [Total: 15] 9693/04/M/J/19© UCLES 2019 14 BLANK PAGE 9693/04/M/J/19© UCLES 2019 15 BLANK PAGE 9693/04/M/J/19© UCLES 2019 16 BLANK PAGE Permission to reproduce items where third-party owned material protected by copyright is included has been sought and cleared where possible.
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9693/04/M/J/19© UCLES 2019