Conservation of marine ecosystems — Paper 4 · A Level Marine Science 9693

4 (a) Planting of mangroves and building artificial reefs can assist in the rehabilitation of marine species. Discuss the advantages and disadvantages of each of these methods. … … … … … … … … … … … … … … … … … [7] (b) Describe and explain the possible impacts of increasing atmospheric carbon dioxide on marine ecosystems. … … … … … … … … … … … … … … … … … … … … [8] [Total: 15]

15 marks

Mark scheme: 4(a) advantages minimum of two: a (mangrove / artificial reef) reduced coastal erosion / AW ; b (mangrove) stabilises substrate ; c (mangrove) acts as a nursery ground / breeding site for species / habitats for juveniles ; d (artificial reef) acts as a shelter for young fish ; e (artificial reef) provides habitat for attachment of organisms ; f (mangrove / artificial reef) provides safety from predators ; g (mangrove / artificial reef) provides food for food chains / establishes food chains ; h (mangrove / artificial reef) increases fish catch for locals ; i (mangrove) provides oxygen ; j (mangrove) removes carbon dioxide ; k (artificial reef) encourages tourism / diving ; disadvantages minimum of two: l (mangroves may cause) low oxygen due to leaf decay ; m (mangroves may be) invasive / damage other areas / grow out of control ; n (mangroves may) lose land with economic value (e.g. beaches) / AW ; 1 (artificial reefs) may alter water currents affecting coastline ; 2 (artificial reefs) may get in the way of fishing boats ; 3 (artificial reefs) may release toxins / TBT / AW ; 4 (artificial reefs) may damage sea bed / physical destruction of habitats ; 5 (artificial reefs) may cause aggregation of wrong species / AW ; 7 A correct named toxin Question Answer Marks Guidance 4(b) any eight of: a increased global temperature / global warming / enhanced greenhouse effect ; b long wave IR light trapped ; c glacier / ice cap melt causing sea level rise ; d loss of habitats ; e altered salinities ; f food chain effect ; g extinction ; h migration / range changes ; i altered primary productivity / increased photosynthesis ; j acidification / carbonic acid ; k coral bleaching ; l erosion of shells / AW ; m expelling zooxanthellae ; 8

This question in 9693/41 Oct/Nov 2017

3 (a) (i) Explain why the precautionary principle is used when considering whether to permit the aquaculture of genetically engineered fish such as salmon. … … … … … [2] (ii) Outline how and why salmon have been genetically engineered for aquaculture. … … … … … … … … … … … [5] (b) Both genetically engineered and non-genetically engineered salmon are grown using aquaculture systems. Explain the negative impacts that aquaculture could have on wild fish near to a salmon farm. … … … … … … … … … … … … … … … … … [8] [Total: 15]

15 marks

This question in 9693/40 May/June 2018

4 (a) Mass tourism in coastal areas can have negative effects on marine environments. These can be caused by large scale agriculture to meet the demands for food and the use of desalination plants to meet the demands for fresh water. (i) Explain the negative ecological impacts of agriculture on the marine environment. … … … … … … … … … [4] (ii) Explain the negative ecological impacts of desalination plants on the marine environment. … … … … … … … … … [4] (b) Damage to the marine environment can be reduced by responsible tourism practices. A new coastal ecotourist resort is planned. Describe the responsible practices that should be included in the development of this resort. … … … … … … … … … … … … … … … [7] [Total: 15]

15 marks

This question in 9693/40 May/June 2018

4 Wild populations of giant clams have decreased since the 1990s. Giant clams are now raised by aquaculture in some Pacific Islands for food, and to help in conservation efforts by releasing cultivated clams into the wild. (a) State what is meant by the term conservation. … … … [1] (b) (i) Outline the process used for the aquaculture of giant clams. … … … … … … … … … … … … … [5] (ii) Explain the risks associated with releasing cultivated giant clams into the wild. … … … … … … … … … … [4] (c) Giant clams are osmoconformers. Explain the meaning of the term osmoconformer and explain the effects on the clams of being placed in water of very high and very low salinities. … … … … … … … … … … … … … … [5]

15 marks

This question in 9693/40 Oct/Nov 2018

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. fishing effort / quantity of fishing gear used per km2 per day marine reserve marine (no fishing) land reserve line 26–42 sampling 8km 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] (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 outside marine reserve reserve 14 13 12 11 10 9 grouper egg 8 density / number of 7 eggs per 1000 m3 6 5 4 3 2 1 0 0 1 2 3 4 5 6 7 8 distance from centre of marine reserve / km Fig. 1.2 (i) Describe how grouper egg density changes with distance from the centre of the marine reserve. … … … … [2] (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. … 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]

11 marks

Mark scheme: 1(a) fish breed within the reserve / numbers increase in the reserve ; idea of: fish ‘spill over’ into areas surrounding reserve ; 2 1(b)(i) any 2 of: egg density decreases (with increasing distance) / negative correlation ; increase after 6 (km) / furthest from reserve ; idea of: wide variation (about the line of best fit) / weak correlation / (many) outliers ; 2 A ORA if explicitly stated A higher / goes at 7.6 (km) or 7.95/8 (km) A (many) anomalies A scattered / wide spread 1(b)(ii) (–)0.4375 to (–)0.4875 (or correct rounding of) ; ; ; 3 I minus 1(c) any 4 of: (supporting benefits) (a) egg density is higher within the reserve / more eggs in, reserve OR egg laying / breeding, is high in the reserve / high fecundity / high recruitment in reserve ; (b) fishing (effort), is high around the reserve showing fish, numbers are high / move out of reserve ; (against benefits) (c) there is only one set of data / no repeats / only one species ; (d) no mention of any controls / not compared to area without reserve ; (e) could be another (named), factor / variable, affecting (fish stocks / egg density / fishing patterns) ; (f) egg numbers, recover / increase, far away from the reserve (where fishing is less) ; 4 A egg density decreases with distance A spawning / breeding, is high in the, reserve / centre R idea of: having / needing to fish harder 1(c) (g) there is, over / excess, fishing near to the reserve ; (h) the correlation is weak with / many outliers ; idea of: fishing effort is not a reliable / accurate / precise, measure OR CPUE would be a better measure / catch would be a better measure ;

This question in 9693/41 May/June 2019

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] (c) Explain how ecotourism practices can reduce damage to the marine environment. … … … … … … … … … … … … … … … [7] [Total: 15]

15 marks

Mark scheme: 4(a) protecting / preserving / restoring, species / habitats / biodiversity / food webs / food chains ; preventing extinction / idea of: there for future generations ; 2 I environment I protecting animals 4(b) any 6 of: (a) (artificial reefs) act as, nursery ground / shelter / habitat ; (b) idea of: (artificial reefs) allow development of, food, chains / webs or community OR (artificial reefs) increase biodiversity (of the area) ; (c) (artificial reefs) reduce coastal erosion ; (d) release of toxins / pollution from, wrecks (used to make reefs) / reefs ; (e) (artificial reef) may, damage sea bed / create obstacles ; (f) (artificial reefs) are a, long-term / sustainable, solution ; (g) (artificial reefs) take a long time to establish ; 6 A acts as a substrate for / allows coral growth Question Answer Marks Guidance 4(b) (h) (artificial reefs) provide revenue from diving / tourism OR (cultivated stocks) provide revenue from increased fishing / tourist (fishing) ; (i) (cultivated stocks) may change, gene pool / genetics of population / alters alleles (of wild population); (j) (cultivated stocks) may have infections / disease ; (k) idea of: (cultured stocks) are not adapted correctly OR idea of: (cultured stock) outcompete wild fish ; A descriptions of poorly adapted A any idea of competition I costs 4(c) any 7 of: Carbon neutral idea (a) distinct method to reduce carbon footprints ; (b) to reduce use of fossil fuels / less carbon (dioxide) emissions / lower carbon footprint / carbon sequestration ; (c) reduced, global warming / climate change / less ocean acidification / less (coral) bleaching ; reduction of habitat / species damage (d) not using coral / careful selection of site (avoid nesting beaches etc) / restricting access / careful anchorages / responsible diving or excursions / not removing species for curios / avoiding light or noise pollution ; Waste (e) (rubbish) recycling / litter removal or disposal / stop use of plastic / use plastic alternatives / encourage tourists to remove litter / encourage taking litter home ; (f) less, (micro) plastic / toxins, entering food chains OR less negative effects of litter on marine species ; (g) sewage disposal or treatment / run-off disposal / restrict , detergents / fertiliser / chemicals, use ; (h) less, eutrophication / algal blooms / red tides / toxic waste (in sea) ; 7 e.g. renewable energy sources / minimising vehicles / reduction in food miles Question Answer Marks Guidance 4(c) Water (i) recycling of water / use of grey water / water treatment ; (j) less need for desalination / protection of estuaries ; Money (k) sponsorship of conservation projects / money from tourism is used to maintain species diversity / local people employed / money into local economy ; Education (l) tourists / locals, gain better understanding about, (marine) conservation / (marine) environment / (marine) issues / stated marine issues ; Food (m) idea of: sustainable food sources / reducing, overfishing / excess agriculture / local food sources / seasonal food sources ; I not eating fish

This question in 9693/41 May/June 2019

3 Government ministries often place restrictions on fishing to ensure sustainable exploitation of fish stocks. (a) Describe the long-term and short-term sociological impacts of restrictions on fishing. … … … … … … … … [4] (b) Discuss the information that government ministries may use to decide how to best exploit fish stocks on a sustainable basis. … … … … … … … … … … … … … … [7] (c) Discuss the advantages and disadvantages of building artificial reefs to rehabilitate depleted fish stocks. … … … … … … … … [4] [Total: 15]

15 marks

This question in 9693/40 Oct/Nov 2020

4 (a) (i) Explain why the ecological linkages within a food web must be considered when planning to conserve a species. … … … … … … … [3] (ii) Discuss the advantages and disadvantages of replanting mangroves to rehabilitate fish stocks. … … … … … … … … … … … [5] (b) Explain how negative ecological impacts of an aquaculture venture located in coastal waters can be minimised. … … … … … … … … … … … … … … … [7] [Total: 15]

15 marks

This question in 9693/40 May/June 2021

4 Mangrove forests are areas of environmental importance. Replanting mangroves has been suggested as a method to increase the biodiversity of the areas they are grown in. (a) Fig. 4.1 shows a section through a leaf from a holly mangrove bush. Fig. 4.1 Make a large drawing of the part of the mangrove leaf in the circle in Fig. 4.1. Do not label your drawing. [4] (b) A student investigated if the size of mangrove forests affects biodiversity. The student collected data from different-sized areas of mangrove forest. The student then carried out a Spearman’s rank correlation coefficient test to test the null hypothesis. The null hypothesis was that there was no correlation between the area of mangrove forest and Simpson’s index of diversity of organisms. Table 4.1 shows the results. Table 4.1 area of rank of area Simpson’s rank of D (r1–r2) D2 mangrove of forest (r1) index of Simpson’s forest / km2 diversity index of diversity (r2) 0.02 8 0.44 7 1 1 0.04 5.5 0.56 5 0.5 0.25 0.02 0.34 10 0.11 1 0.82 1 0 0 0.02 0.38 8 0.05 4 0.61 3 1 1 0.06 3 0.58 4 –1 1 0.09 2 0.75 2 0 0 0.01 10 0.35 9 1 1 0.04 5.5 0.54 6 –0.5 0.25 ΣD2 = … (i) Complete Table 4.1 to calculate the value of ΣD2. [2] (ii) Use your answer to (b)(i) and the formula to calculate the Spearman’s rank correlation coefficient, rs. Give your answer to three decimal places. 6 × ΣD2 rs = 1 –  n3 – n  Σ = sum of (total) n = number of pairs of items in the sample D = difference in rank between each pair of measurements … [2] (iii) Table 4.2 is a critical values table for Spearman’s rank correlation coefficient. Table 4.2 number of P<0.05 paired items, n 5 1.000 6 0.886 7 0.786 8 0.738 9 0.700 10 0.648 11 0.618 12 0.587 Use your answer to (b)(ii) and Table 4.2 to evaluate the null hypothesis. … … … … … … [3] (iv) Suggest why the size of the area of mangrove forest affects the Simpson’s index of diversity. … … … … [2] (c) In a further study in a coastal area of Indonesia, local people were asked to complete a questionnaire about how willing they were to take part in replanting mangroves. The results of the questionnaire are shown in Table 4.3. Table 4.3 question percentage of people with response / % strongly disagree unsure agree strongly disagree agree Are you willing to participate 12 12 0 40 36 in mangrove replanting in the area? Do you currently volunteer to 38 42 8 7 5 help mangrove replanting? Should you have appropriate 9 18 3 44 26 pay if you participate in the mangrove replanting? Do you have skills in mangrove 35 28 5 18 14 replanting? Use the results of the questionnaire in Table 4.3 to discuss how a government could successfully engage local communities in replanting mangrove forests. … … … … … … [3] [Total: 16]

16 marks

Mark scheme: 4(a) 1 thin, unbroken clear lines in pencil ; 4 2 correct proportions and takes up at least two-thirds of space ; 3 six cells drawn, cell walls for all cells, nucleus in middle cell, double line for outer layer ; 4 no shading and only draw what is inside circle ; 4(b)(i) 2 area of rank of area Simpson’s rank of D (r1–r2) D2 mangrove of forest (r1) index of Simpson’s forest / km2 diversity index of diversity (r2) 0.02 8 0.44 7 1 1 0.04 5.5 0.56 5 0.5 0.25 0.02 8 0.34 10 –2 4 0.11 1 0.82 1 0 0 0.02 8 0.38 8 0 0 ; 0.05 4 0.61 3 1 1 0.06 3 0.58 4 -1 1 0.09 2 0.75 2 0 0 0.01 10 0.35 9 1 1 0.04 5.5 0.54 6 -0.5 0.25  D2 = 8.5 ; 4(b)(ii) 0.948 ;; 2 4(b)(iii) any 3 of: 3 null hypothesis is rejected ; calculated value is greater than the critical value ; critical value identified as 0.648 ; there is a (significant) positive correlation between size of mangrove forest area and species diversity / there is probability of less than 0.05 that the association is due to chance ; 4(b)(iv) any 2 of: 2 more producers / more productivity / more photosynthesis ; more energy enters ecosystem ; more (trophic) levels possible in food chains ; more niches ; more habitats / more (variety of) food sources / more nesting sites / more shelter from predators / AW ; 4(c) any 3 of: 3 1 few people are currently involved / AW ; 2 but local people, want / are willing to get involved / AW ; 3 need to pay people / compensate for time spent working / AW ; 4 education / training needed (as people do not already have skills) ; 5 train local people to teach other locals (peer education) / encourage social activities around planting / AW ; 6 local community involvement could be more successful than ‘top down’ government work / make local people stakeholders / AW ;

This question in 9693/41 Oct/Nov 2023

4 Mangrove forests are areas of environmental importance. Replanting mangroves has been suggested as a method to increase the biodiversity of the areas they are grown in. (a) Fig. 4.1 shows a section through a leaf from a holly mangrove bush. Fig. 4.1 Make a large drawing of the part of the mangrove leaf in the circle in Fig. 4.1. Do not label your drawing. [4] (b) A student investigated if the size of mangrove forests affects biodiversity. The student collected data from different-sized areas of mangrove forest. The student then carried out a Spearman’s rank correlation coefficient test to test the null hypothesis. The null hypothesis was that there was no correlation between the area of mangrove forest and Simpson’s index of diversity of organisms. Table 4.1 shows the results. Table 4.1 area of rank of area Simpson’s rank of D (r1–r2) D2 mangrove of forest (r1) index of Simpson’s forest / km2 diversity index of diversity (r2) 0.02 8 0.44 7 1 1 0.04 5.5 0.56 5 0.5 0.25 0.02 0.34 10 0.11 1 0.82 1 0 0 0.02 0.38 8 0.05 4 0.61 3 1 1 0.06 3 0.58 4 –1 1 0.09 2 0.75 2 0 0 0.01 10 0.35 9 1 1 0.04 5.5 0.54 6 –0.5 0.25 ΣD2 = … (i) Complete Table 4.1 to calculate the value of ΣD2. [2] (ii) Use your answer to (b)(i) and the formula to calculate the Spearman’s rank correlation coefficient, rs. Give your answer to three decimal places. 6 × ΣD2 rs = 1 –  n3 – n  Σ = sum of (total) n = number of pairs of items in the sample D = difference in rank between each pair of measurements … [2] (iii) Table 4.2 is a critical values table for Spearman’s rank correlation coefficient. Table 4.2 number of P<0.05 paired items, n 5 1.000 6 0.886 7 0.786 8 0.738 9 0.700 10 0.648 11 0.618 12 0.587 Use your answer to (b)(ii) and Table 4.2 to evaluate the null hypothesis. … … … … … … [3] (iv) Suggest why the size of the area of mangrove forest affects the Simpson’s index of diversity. … … … … [2] (c) In a further study in a coastal area of Indonesia, local people were asked to complete a questionnaire about how willing they were to take part in replanting mangroves. The results of the questionnaire are shown in Table 4.3. Table 4.3 question percentage of people with response / % strongly disagree unsure agree strongly disagree agree Are you willing to participate 12 12 0 40 36 in mangrove replanting in the area? Do you currently volunteer to 38 42 8 7 5 help mangrove replanting? Should you have appropriate 9 18 3 44 26 pay if you participate in the mangrove replanting? Do you have skills in mangrove 35 28 5 18 14 replanting? Use the results of the questionnaire in Table 4.3 to discuss how a government could successfully engage local communities in replanting mangrove forests. … … … … … … [3] [Total: 16]

16 marks

Mark scheme: 4(a) 1 thin, unbroken clear lines in pencil ; 4 2 correct proportions and takes up at least two-thirds of space ; 3 six cells drawn, cell walls for all cells, nucleus in middle cell, double line for outer layer ; 4 no shading and only draw what is inside circle ; 4(b)(i) 2 area of rank of area Simpson’s rank of D (r1–r2) D2 mangrove of forest (r1) index of Simpson’s forest / km2 diversity index of diversity (r2) 0.02 8 0.44 7 1 1 0.04 5.5 0.56 5 0.5 0.25 0.02 8 0.34 10 –2 4 0.11 1 0.82 1 0 0 0.02 8 0.38 8 0 0 ; 0.05 4 0.61 3 1 1 0.06 3 0.58 4 -1 1 0.09 2 0.75 2 0 0 0.01 10 0.35 9 1 1 0.04 5.5 0.54 6 -0.5 0.25  D2 = 8.5 ; 4(b)(ii) 0.948 ;; 2 4(b)(iii) any 3 of: 3 null hypothesis is rejected ; calculated value is greater than the critical value ; critical value identified as 0.648 ; there is a (significant) positive correlation between size of mangrove forest area and species diversity / there is probability of less than 0.05 that the association is due to chance ; 4(b)(iv) any 2 of: 2 more producers / more productivity / more photosynthesis ; more energy enters ecosystem ; more (trophic) levels possible in food chains ; more niches ; more habitats / more (variety of) food sources / more nesting sites / more shelter from predators / AW ; 4(c) any 3 of: 3 1 few people are currently involved / AW ; 2 but local people, want / are willing to get involved / AW ; 3 need to pay people / compensate for time spent working / AW ; 4 education / training needed (as people do not already have skills) ; 5 train local people to teach other locals (peer education) / encourage social activities around planting / AW ; 6 local community involvement could be more successful than ‘top down’ government work / make local people stakeholders / AW ;

This question in 9693/42 Oct/Nov 2023

4 Mangrove forests are areas of environmental importance. Replanting mangroves has been suggested as a method to increase the biodiversity of the areas they are grown in. (a) Fig. 4.1 shows a section through a leaf from a holly mangrove bush. Fig. 4.1 Make a large drawing of the part of the mangrove leaf in the circle in Fig. 4.1. Do not label your drawing. [4] (b) A student investigated if the size of mangrove forests affects biodiversity. The student collected data from different-sized areas of mangrove forest. The student then carried out a Spearman’s rank correlation coefficient test to test the null hypothesis. The null hypothesis was that there was no correlation between the area of mangrove forest and Simpson’s index of diversity of organisms. Table 4.1 shows the results. Table 4.1 area of rank of area Simpson’s rank of D (r1–r2) D2 mangrove of forest (r1) index of Simpson’s forest / km2 diversity index of diversity (r2) 0.02 8 0.44 7 1 1 0.04 5.5 0.56 5 0.5 0.25 0.02 0.34 10 0.11 1 0.82 1 0 0 0.02 0.38 8 0.05 4 0.61 3 1 1 0.06 3 0.58 4 –1 1 0.09 2 0.75 2 0 0 0.01 10 0.35 9 1 1 0.04 5.5 0.54 6 –0.5 0.25 ΣD2 = … (i) Complete Table 4.1 to calculate the value of ΣD2. [2] (ii) Use your answer to (b)(i) and the formula to calculate the Spearman’s rank correlation coefficient, rs. Give your answer to three decimal places. 6 × ΣD2 rs = 1 –  n3 – n  Σ = sum of (total) n = number of pairs of items in the sample D = difference in rank between each pair of measurements … [2] (iii) Table 4.2 is a critical values table for Spearman’s rank correlation coefficient. Table 4.2 number of P<0.05 paired items, n 5 1.000 6 0.886 7 0.786 8 0.738 9 0.700 10 0.648 11 0.618 12 0.587 Use your answer to (b)(ii) and Table 4.2 to evaluate the null hypothesis. … … … … … … [3] (iv) Suggest why the size of the area of mangrove forest affects the Simpson’s index of diversity. … … … … [2] (c) In a further study in a coastal area of Indonesia, local people were asked to complete a questionnaire about how willing they were to take part in replanting mangroves. The results of the questionnaire are shown in Table 4.3. Table 4.3 question percentage of people with response / % strongly disagree unsure agree strongly disagree agree Are you willing to participate 12 12 0 40 36 in mangrove replanting in the area? Do you currently volunteer to 38 42 8 7 5 help mangrove replanting? Should you have appropriate 9 18 3 44 26 pay if you participate in the mangrove replanting? Do you have skills in mangrove 35 28 5 18 14 replanting? Use the results of the questionnaire in Table 4.3 to discuss how a government could successfully engage local communities in replanting mangrove forests. … … … … … … [3] [Total: 16]

16 marks

Mark scheme: 4(a) 1 thin, unbroken clear lines in pencil ; 4 2 correct proportions and takes up at least two-thirds of space ; 3 six cells drawn, cell walls for all cells, nucleus in middle cell, double line for outer layer ; 4 no shading and only draw what is inside circle ; 4(b)(i) 2 area of rank of area Simpson’s rank of D (r1–r2) D2 mangrove of forest (r1) index of Simpson’s forest / km2 diversity index of diversity (r2) 0.02 8 0.44 7 1 1 0.04 5.5 0.56 5 0.5 0.25 0.02 8 0.34 10 –2 4 0.11 1 0.82 1 0 0 0.02 8 0.38 8 0 0 ; 0.05 4 0.61 3 1 1 0.06 3 0.58 4 -1 1 0.09 2 0.75 2 0 0 0.01 10 0.35 9 1 1 0.04 5.5 0.54 6 -0.5 0.25  D2 = 8.5 ; 4(b)(ii) 0.948 ;; 2 4(b)(iii) any 3 of: 3 null hypothesis is rejected ; calculated value is greater than the critical value ; critical value identified as 0.648 ; there is a (significant) positive correlation between size of mangrove forest area and species diversity / there is probability of less than 0.05 that the association is due to chance ; 4(b)(iv) any 2 of: 2 more producers / more productivity / more photosynthesis ; more energy enters ecosystem ; more (trophic) levels possible in food chains ; more niches ; more habitats / more (variety of) food sources / more nesting sites / more shelter from predators / AW ; 4(c) any 3 of: 3 1 few people are currently involved / AW ; 2 but local people, want / are willing to get involved / AW ; 3 need to pay people / compensate for time spent working / AW ; 4 education / training needed (as people do not already have skills) ; 5 train local people to teach other locals (peer education) / encourage social activities around planting / AW ; 6 local community involvement could be more successful than ‘top down’ government work / make local people stakeholders / AW ;

This question in 9693/43 Oct/Nov 2023

5 (a) Explain why international cooperation and legislation are necessary for the effective conservation of many marine species. … … … … [2] (b) Cultivated salmon that have been raised in captivity are often used to rehabilitate wild stocks. Young wild salmon naturally migrate from a river towards its estuary as part of their life cycle. Young salmon that have been raised in captivity often swim in the wrong direction when they are released and do not reach the estuary. Scientists investigated if acclimatising young salmon in rivers before release affects their migration behaviour. This is the method the scientists used. • Young salmon were raised in captivity and then separated into two groups. • One group of the young salmon was placed into cages in the river for two weeks to acclimatise. The other group (non-acclimatised salmon) remained in the fresh-water tanks. • Both groups of salmon were tagged with a unique identifier so they could be detected. Both groups were then released into the river. • Sensors to detect the salmon were placed upstream and downstream of the release site. • The number of salmon that passed each sensor each day were recorded. The results are shown in Fig. 5.1. number of non-acclimatised salmon detected upstream 6 5 number of 4 young salmon 3 detected 2 1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 time / days number of acclimatised salmon detected upstream 6 5 number of 4 young salmon 3 detected 2 1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 time / days number of non-acclimatised salmon detected downstream 12 11 10 9 8 number of 7 young salmon 6 detected 5 4 3 2 1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 time / days number of acclimatised salmon detected downstream 12 11 10 9 8 number of 7 young salmon 6 detected 5 4 3 2 1 0 0 5 10 15 20 25 30 35 40 45 50 55 60 time / days Fig. 5.1 (i) The scientists tagged 150 young salmon in each group. Use Fig. 5.1 to calculate the percentage of acclimatised salmon that moved upstream. Show your working. … % [2] (ii) Discuss the effects of acclimatising the young salmon on their migration behaviour. Use the data in Fig. 5.1 to support your answer. … … … … … … … … [4]

8 marks

Mark scheme: 5(a) any 2 of: 1 to protect, endangered species / species at risk of extinction ; 2 species live across national boundaries / species live in international waters / AW ; 3 species migrate ; 4 need to control import / export / trade (between countries) / AW ; 5 so same rules for all / as different countries may have different views / AW ; 2 5(b)(i) 6.7 / 6.67 / 6.666 recurring / 7% ;; (two marks) one mark for 10 or 6.6 ; 2 5(b)(ii) any 4 of: 1 few(er) acclimatised salmon (compared with non-acclimatised), move upstream / go the wrong way / AW ; 2 more of both types of salmon go downstream (compared with moving upstream) / AW ; 3 acclimatised salmon move upstream earlier / do not stay in area long / AW ; 4 acclimatised salmon move downstream later / stay in area longer / AW ; 5 wider range of times for acclimatised salmon moving downstream / wider range of times non-acclimatised salmon moving upstream / AW ; 6 acclimatised salmon adapt to water conditions / food / currents / temperature / AW ; 7 AVP ; 4 5(c)(i) 25 , 625 , 41.7 ; 1 5(c)(ii) 51.3 ; 1 5(c)(iii) any 3 of: 1 the null hypothesis is rejected ; 2 the calculated value is greater than the critical value ; 3 correct identification of critical value of 3.841 or 6.635 ; 4 there is a significant difference ; 3

This question in 9693/41 May/June 2024

2 Lionfish are an invasive species around coral reefs in many parts of the West Atlantic Ocean and Caribbean Sea. Fig. 2.1 shows a photograph of a lionfish. Fig. 2.1 In an area of Mexico, the government developed a conservation project to reduce the impact of lionfish and provide a sustainable lionfish industry for local people. As part of this conservation project, a fishery was set up to encourage local people to catch lionfish. Lionfish were sold at market and became a major source of income for local people. (a) The lionfish fishery was set up in 2011. Net fishing for the lionfish was banned. Spearfishing was the only permitted method. Table 2.1 shows the catches of lionfish from 2011 to 2017. Table 2.1 year number of lionfish caught 2011 1017 2012 2515 2013 17 250 2014 23 121 2015 12 022 2016 6032 2017 1035 (i) Suggest two reasons why spearfishing was the only method allowed to catch the lionfish. 1 … … 2 … … [2] (ii) Calculate the percentage increase of catch from 2011 to 2014. Give your answer to two significant figures. Space for working. … % [3] (b) In 2013, 2014 and 2015 the population densities of lionfish in three reef areas of the fishery were estimated. (i) Outline one method that could be used to estimate the population density of lionfish on a reef. … … … … [2] (ii) Fig. 2.2 shows the mean population densities of lionfish in the three reef areas during 2013, 2014, and 2015. 350 Key reef area 1 300 reef area 2 250 reef area 3 mean population 200 density of lionfish / number m–2 150 100 50 0 2013 2014 2015 year Fig. 2.2 Explain the effects of the conservation project on the changes in population of lionfish in the reef areas. … … … … … … [3] (c) Table 2.2 shows the mean price of lionfish at a market in Mexico from 2011 to 2017. Table 2.2 year mean price per kilogram / USD ($) 2011 3.8 2012 3.8 2013 2.5 2014 2.4 2015 2.7 2016 4.2 2017 6.8 Evaluate the success of the lionfish fishery as a method of controlling the lionfish population and providing an industry for local people. Use Table 2.1, Fig. 2.2 and Table 2.2 to support your answer. … … … … … … … … [4] [Total: 14]

14 marks

Mark scheme: 2(a)(i) any 2 of: 2 1 prevents bycatch / AW ; 2 no loss of tackle on reefs / less damaging to reefs / habitats / seabed / AW ; 3 prevents over-fishing / AW ; 4 less chance of catching juveniles / immature fish / AW ; 2(a)(ii) 2200 (%) ;;; 3 Two marks for: 2173.45…. One mark for:  1017 OR 23 121 – 1017 OR 22014 2(b)(i) 1 practical method of counting lionfish ; 2 2 divide number by area ; 2(b)(ii) any 3 of: 3 1 populations fall in all reefs / AW ; 2 reef area 1 and 2 increase after 2014 / reef area 3 decreases less steeply after 2014 / AW ; 3 less breeding / reproduction / recruitment / loss of breeding stock / AW ; 4 financial reward encourages, high rate of capture / AW ; 5 fishing intensity may reduce after 2014 / AW ; 2(c) any 4 of: 4 1 lionfish have been successfully controlled / lionfish population has lowered / AW ; 2 total catch increases until 2014 then decreases / highest catch in 2014 / AW ; 3 (fewer lionfish means) reduced damage to native species / less damage to habitats / AW ; 4 (however) there is a slight rise in population in 2014 (in two reef areas) (suggesting they are recovering) / AW ; 5 price of lionfish decreases until 2014 / price of lionfish rises after 2014 / lowest prices between 2013 and 2014 / AW ; 6 low / falling, price if many fish caught / AW ; 7 fishing industry is not long-term / AW ; 8 (loss of fishery) could result in loss of income / employment / sociological issues / poverty / AW ; 9 AVP ;

This question in 9693/42 May/June 2025

2 Lionfish are an invasive species around coral reefs in many parts of the West Atlantic Ocean and Caribbean Sea. Fig. 2.1 shows a photograph of a lionfish. Fig. 2.1 In an area of Mexico, the government developed a conservation project to reduce the impact of lionfish and provide a sustainable lionfish industry for local people. As part of this conservation project, a fishery was set up to encourage local people to catch lionfish. Lionfish were sold at market and became a major source of income for local people. (a) The lionfish fishery was set up in 2011. Net fishing for the lionfish was banned. Spearfishing was the only permitted method. Table 2.1 shows the catches of lionfish from 2011 to 2017. Table 2.1 year number of lionfish caught 2011 1017 2012 2515 2013 17 250 2014 23 121 2015 12 022 2016 6032 2017 1035 (i) Suggest two reasons why spearfishing was the only method allowed to catch the lionfish. 1 … … 2 … … [2] (ii) Calculate the percentage increase of catch from 2011 to 2014. Give your answer to two significant figures. Space for working. … % [3] (b) In 2013, 2014 and 2015 the population densities of lionfish in three reef areas of the fishery were estimated. (i) Outline one method that could be used to estimate the population density of lionfish on a reef. … … … … [2] (ii) Fig. 2.2 shows the mean population densities of lionfish in the three reef areas during 2013, 2014, and 2015. 350 Key reef area 1 300 reef area 2 250 reef area 3 mean population 200 density of lionfish / number m–2 150 100 50 0 2013 2014 2015 year Fig. 2.2 Explain the effects of the conservation project on the changes in population of lionfish in the reef areas. … … … … … … [3] (c) Table 2.2 shows the mean price of lionfish at a market in Mexico from 2011 to 2017. Table 2.2 year mean price per kilogram / USD ($) 2011 3.8 2012 3.8 2013 2.5 2014 2.4 2015 2.7 2016 4.2 2017 6.8 Evaluate the success of the lionfish fishery as a method of controlling the lionfish population and providing an industry for local people. Use Table 2.1, Fig. 2.2 and Table 2.2 to support your answer. … … … … … … … … [4] [Total: 14]

14 marks

Mark scheme: 2(a)(i) any 2 of: 2 1 prevents bycatch / AW ; 2 no loss of tackle on reefs / less damaging to reefs / habitats / seabed / AW ; 3 prevents over-fishing / AW ; 4 less chance of catching juveniles / immature fish / AW ; 2(a)(ii) 2200 (%) ;;; 3 Two marks for: 2173.45…. One mark for:  1017 OR 23 121 – 1017 OR 22014 2(b)(i) 1 practical method of counting lionfish ; 2 2 divide number by area ; 2(b)(ii) any 3 of: 3 1 populations fall in all reefs / AW ; 2 reef area 1 and 2 increase after 2014 / reef area 3 decreases less steeply after 2014 / AW ; 3 less breeding / reproduction / recruitment / loss of breeding stock / AW ; 4 financial reward encourages, high rate of capture / AW ; 5 fishing intensity may reduce after 2014 / AW ; 2(c) any 4 of: 4 1 lionfish have been successfully controlled / lionfish population has lowered / AW ; 2 total catch increases until 2014 then decreases / highest catch in 2014 / AW ; 3 (fewer lionfish means) reduced damage to native species / less damage to habitats / AW ; 4 (however) there is a slight rise in population in 2014 (in two reef areas) (suggesting they are recovering) / AW ; 5 price of lionfish decreases until 2014 / price of lionfish rises after 2014 / lowest prices between 2013 and 2014 / AW ; 6 low / falling, price if many fish caught / AW ; 7 fishing industry is not long-term / AW ; 8 (loss of fishery) could result in loss of income / employment / sociological issues / poverty / AW ; 9 AVP ;

This question in 9693/43 May/June 2025

1 Artificial reefs are often created by sinking old ships. (a) Explain how artificial reefs can help to rehabilitate fish stocks. … … … … … … [3] (b) Scientists investigated the risk of heavy metal ions leaking from artificial reefs into sea water. Bags of mussels were placed on a sunken metal ship. Bags of mussels were also placed at an area one kilometre from the ship as a control. After six months, the mean concentrations of chromium ions, lead ions and zinc ions in the mussels were determined. The results are shown in Table 1.1. Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 (i) Calculate the percentage difference in the mean concentration of chromium ions in the mussels on the ship compared with the mean concentration of chromium ions in the control mussels. Give your answer to two significant figures. Show your working. … % [3] (ii) Describe the differences in concentrations of heavy metal ions in the mussels on the ship compared with the concentrations of heavy metal ions in the control mussels. … … … … … … [3] (c) Fig. 1.1 shows the concentration of lead ions in the tissues of consumers that feed on mussels containing different concentrations of lead ions. 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (i) Summarise the effect of increasing concentration of lead ions in the tissues of mussels on the concentration of lead ions in the tissues of consumer organisms. … … … … [2] Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (ii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to predict the mean concentration of lead ions in the tissues of consumer organisms that eat mussels from the ship. … mg kg–1 [1] (iii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to explain the risks of using ships as artificial reefs. … … … … … … [4] [Total: 16]

16 marks

Mark scheme: Question Answer Marks 1(a) any 3 of: 3 1 act as a, substrate (for sessile organisms) / habitat ; 2 create food webs / food chains ; 3 more food availability / more niches / AW ; 4 shelter for fish / protection from predators / AW ; 5 nursery / breeding, grounds / AW ; 1(b)(i) 1.40 – 0.67 = 0.73 ; 3 0.73 / 0.67 – 100 = 108.958… ; 110(%) ;;; (3 marks) 108.958… (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 0.67 OR 1.40 – 0.67 = 0.73 ; 0.73 / 1.40 – 100 = 52.14…(%) ; 52(%) ;;; (3 marks) 0.5214… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.40 OR 0.73 / 1.035  100 = 70.53… ; A 70(%) ;;; (3 marks) 70.53… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.035 1(b)(ii) any 3 of: 3 1 higher in all (on ship compared with control) / ORA ; 2 zinc has highest levels (compared with chromium and lead) / lead has lowest levels / AW ; 3 chromium and lead are significantly higher / zinc is not significantly higher ; 4 correct ref to s.d. overlaps ; 5 credit correct manipulation of data ; 6 chromium has, highest relative / percentage increase ; 1(c)(i) increase / positive correlation / as lead increases in mussels, lead increases in consumers ; 2 steep increase then levels off ; 1(c)(ii) answer between 0.64–0.65 ; 1 1(c)(iii) any 4 of: 4 1 mussels / low trophic level organisms, absorb heavy metal ions / absorb chromium / absorb lead / absorb zinc / AW ; 2 heavy metal ions are (often) toxic / AW ; 3 (heavy metal ions) bioaccumulate in organisms ; 4 (heavy metal ions) are not excreted / cannot be broken down / non-biodegradable ; 5 (lead / chromium / heavy metal ions) passed onto consumers / AW ; 6 biomagnification occurs along food chain / AW ; 7 because consumers eat several of lower levels ; 8 AVP ;

This question in 9693/41 Oct/Nov 2025

1 Artificial reefs are often created by sinking old ships. (a) Explain how artificial reefs can help to rehabilitate fish stocks. … … … … … … [3] (b) Scientists investigated the risk of heavy metal ions leaking from artificial reefs into sea water. Bags of mussels were placed on a sunken metal ship. Bags of mussels were also placed at an area one kilometre from the ship as a control. After six months, the mean concentrations of chromium ions, lead ions and zinc ions in the mussels were determined. The results are shown in Table 1.1. Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 (i) Calculate the percentage difference in the mean concentration of chromium ions in the mussels on the ship compared with the mean concentration of chromium ions in the control mussels. Give your answer to two significant figures. Show your working. … % [3] (ii) Describe the differences in concentrations of heavy metal ions in the mussels on the ship compared with the concentrations of heavy metal ions in the control mussels. … … … … … … [3] (c) Fig. 1.1 shows the concentration of lead ions in the tissues of consumers that feed on mussels containing different concentrations of lead ions. 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (i) Summarise the effect of increasing concentration of lead ions in the tissues of mussels on the concentration of lead ions in the tissues of consumer organisms. … … … … [2] Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (ii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to predict the mean concentration of lead ions in the tissues of consumer organisms that eat mussels from the ship. … mg kg–1 [1] (iii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to explain the risks of using ships as artificial reefs. … … … … … … [4] [Total: 16]

16 marks

Mark scheme: Question Answer Marks 1(a) any 3 of: 3 1 act as a, substrate (for sessile organisms) / habitat ; 2 create food webs / food chains ; 3 more food availability / more niches / AW ; 4 shelter for fish / protection from predators / AW ; 5 nursery / breeding, grounds / AW ; 1(b)(i) 1.40 – 0.67 = 0.73 ; 3 0.73 / 0.67 – 100 = 108.958… ; 110(%) ;;; (3 marks) 108.958… (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 0.67 OR 1.40 – 0.67 = 0.73 ; 0.73 / 1.40 – 100 = 52.14…(%) ; 52(%) ;;; (3 marks) 0.5214… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.40 OR 0.73 / 1.035  100 = 70.53… ; A 70(%) ;;; (3 marks) 70.53… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.035 1(b)(ii) any 3 of: 3 1 higher in all (on ship compared with control) / ORA ; 2 zinc has highest levels (compared with chromium and lead) / lead has lowest levels / AW ; 3 chromium and lead are significantly higher / zinc is not significantly higher ; 4 correct ref to s.d. overlaps ; 5 credit correct manipulation of data ; 6 chromium has, highest relative / percentage increase ; 1(c)(i) increase / positive correlation / as lead increases in mussels, lead increases in consumers ; 2 steep increase then levels off ; 1(c)(ii) answer between 0.64–0.65 ; 1 1(c)(iii) any 4 of: 4 1 mussels / low trophic level organisms, absorb heavy metal ions / absorb chromium / absorb lead / absorb zinc / AW ; 2 heavy metal ions are (often) toxic / AW ; 3 (heavy metal ions) bioaccumulate in organisms ; 4 (heavy metal ions) are not excreted / cannot be broken down / non-biodegradable ; 5 (lead / chromium / heavy metal ions) passed onto consumers / AW ; 6 biomagnification occurs along food chain / AW ; 7 because consumers eat several of lower levels ; 8 AVP ;

This question in 9693/42 Oct/Nov 2025

1 Artificial reefs are often created by sinking old ships. (a) Explain how artificial reefs can help to rehabilitate fish stocks. … … … … … … [3] (b) Scientists investigated the risk of heavy metal ions leaking from artificial reefs into sea water. Bags of mussels were placed on a sunken metal ship. Bags of mussels were also placed at an area one kilometre from the ship as a control. After six months, the mean concentrations of chromium ions, lead ions and zinc ions in the mussels were determined. The results are shown in Table 1.1. Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 (i) Calculate the percentage difference in the mean concentration of chromium ions in the mussels on the ship compared with the mean concentration of chromium ions in the control mussels. Give your answer to two significant figures. Show your working. … % [3] (ii) Describe the differences in concentrations of heavy metal ions in the mussels on the ship compared with the concentrations of heavy metal ions in the control mussels. … … … … … … [3] (c) Fig. 1.1 shows the concentration of lead ions in the tissues of consumers that feed on mussels containing different concentrations of lead ions. 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (i) Summarise the effect of increasing concentration of lead ions in the tissues of mussels on the concentration of lead ions in the tissues of consumer organisms. … … … … [2] Table 1.1 heavy metal ion concentration in mussels on concentration in control ship / mg kg–1 mussels / mg kg–1 mean standard deviation mean standard deviation chromium 1.40 0.47 0.67 0.10 lead 0.36 0.05 0.23 0.04 zinc 178.00 44.40 152.00 29.50 0.70 0.60 0.50 concentration of 0.40 lead ions in tissues of consumers 0.30 / mg kg–1 0.20 0.10 0.00 0.00 0.10 0.20 0.30 0.40 concentration of lead ions in tissues of mussels / mg kg–1 Fig. 1.1 (ii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to predict the mean concentration of lead ions in the tissues of consumer organisms that eat mussels from the ship. … mg kg–1 [1] (iii) Use the information in Table 1.1 and Fig. 1.1 (repeated above) to explain the risks of using ships as artificial reefs. … … … … … … [4] [Total: 16]

16 marks

Mark scheme: Question Answer Marks 1(a) any 3 of: 3 1 act as a, substrate (for sessile organisms) / habitat ; 2 create food webs / food chains ; 3 more food availability / more niches / AW ; 4 shelter for fish / protection from predators / AW ; 5 nursery / breeding, grounds / AW ; 1(b)(i) 1.40 – 0.67 = 0.73 ; 3 0.73 / 0.67 – 100 = 108.958… ; 110(%) ;;; (3 marks) 108.958… (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 0.67 OR 1.40 – 0.67 = 0.73 ; 0.73 / 1.40 – 100 = 52.14…(%) ; 52(%) ;;; (3 marks) 0.5214… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.40 OR 0.73 / 1.035  100 = 70.53… ; A 70(%) ;;; (3 marks) 70.53… ;; (2 marks) A 1 mark for 0.73, 1.40–0.67, or division by 1.035 1(b)(ii) any 3 of: 3 1 higher in all (on ship compared with control) / ORA ; 2 zinc has highest levels (compared with chromium and lead) / lead has lowest levels / AW ; 3 chromium and lead are significantly higher / zinc is not significantly higher ; 4 correct ref to s.d. overlaps ; 5 credit correct manipulation of data ; 6 chromium has, highest relative / percentage increase ; 1(c)(i) increase / positive correlation / as lead increases in mussels, lead increases in consumers ; 2 steep increase then levels off ; 1(c)(ii) answer between 0.64–0.65 ; 1 1(c)(iii) any 4 of: 4 1 mussels / low trophic level organisms, absorb heavy metal ions / absorb chromium / absorb lead / absorb zinc / AW ; 2 heavy metal ions are (often) toxic / AW ; 3 (heavy metal ions) bioaccumulate in organisms ; 4 (heavy metal ions) are not excreted / cannot be broken down / non-biodegradable ; 5 (lead / chromium / heavy metal ions) passed onto consumers / AW ; 6 biomagnification occurs along food chain / AW ; 7 because consumers eat several of lower levels ; 8 AVP ;

This question in 9693/43 Oct/Nov 2025