Human Impacts on Ocean Biodiversity
Three of these four investigations happen on the shore — which, for a learner twenty minutes from Algoa Bay, is the best laboratory in the course. The fourth is about reading the news without being fooled by it. Every one carries supplied data, so nothing here depends on the weather or the tide.
Investigations column, block 31, in full: "Visit an Eco-park or SANParks facility to discover the elements of HIPPO." Every sub-topic then ends with the same instruction: "Mitigation measures should be discussed with discussion and debates about better management choices."
The visit is Investigation 1, and it ends in exactly that debate. Investigations 2 and 3 put numbers on two of the letters — Pollution and Invasive species — that you can measure yourself. Investigation 4 answers the study-deck question "Use case studies from media articles to indicate levels of the different HIPPO impacts."
What you need
- 🌊 shore Access to a beach, a rocky shore at low tide, and (for Investigation 1) a protected area or estuary — Sardinia Bay, Cape Recife, the Swartkops estuary, or a SANParks site such as Tsitsikamma or Addo
- 🟢 kitchen A notebook and pencil, your phone (camera, tide table, maps), sturdy shoes, a hat and water
- 🟢 kitchen For the litter survey: two pairs of gardening gloves, refuse bags, a kitchen or luggage scale, and a 100 m measure — or count your paces after measuring your pace length at home
- 🟢 make it For the mussel survey: a 50 cm × 50 cm quadrat, bent from two wire coat hangers or made from four sticks and string
- 🟡 optional A long tape measure (30 m or more) from a hardware shop
Investigation 1 has a described visit to use instead of your own. Investigations 2 and 3 each have a full supplied data set. Investigation 4 is a desk task with all its material supplied. You can complete every table, graph and analysis question without leaving home.
Aim
To visit a protected area or estuary, find and record evidence of each of the five HIPPO threats and of the measures used to protect the site, and to recommend better management.
Method
- Choose your site and read about it first: is it an MPA, a nature reserve, an estuary? Who manages it?
- Walk a set route — along the shore, the estuary bank or a trail — for about an hour.
- Record every piece of evidence of human impact you see: what it is, where, and which HIPPO letter it belongs to. Photograph it; do not collect it.
- Record every piece of evidence of protection or management: signs, rules, boundary markers, bins, boardwalks, rangers or fishery control officers.
- If you can, ask a ranger or official one question: "What is the biggest threat to this place?" Record the answer.
- Score each observation for severity: 1 = minor, 2 = moderate, 3 = serious.
Supplied data — a described visit to the Swartkops estuary
Read this as a composite. It is written for this sheet from the kinds of observations commonly made along the lower Swartkops estuary on Gqeberha's northern edge. It is not a record of one particular day.
- Low tide. On the exposed mudflats, a dozen people are pumping sand and mud prawns for bait. The mud around their holes is churned up over a wide area.
- Along the high-tide line near the mouth: plastic bags, bottles, food wrappers and polystyrene, much of it trapped in the salt-marsh plants.
- A municipal sign at a slipway warns that the water may be unsafe for swimming after heavy rain, because of sewage overflows upstream.
- A stormwater canal from the suburbs enters the estuary. The water at its mouth is grey and smells.
- Upstream: large flat salt pans and industrial buildings stand where salt marsh once was. New houses are being built on the edge of the floodplain.
- The pylons of a jetty are coated in a sea squirt that a local angler says "wasn't here when I was young".
- Two anglers are keeping a fish the ruler on the slipway sign shows is below the legal minimum size.
- Several ski-boats and a jet-ski are running fast through the narrow channel over the eel-grass beds.
- Management seen: a sign listing bait-collection rules and daily limits; a fisheries control officer checking permits; bins at the slipway — overflowing.
- A conservation volunteer says the biggest threat is "what comes down the river — sewage and litter after every storm."
Results
| Letter | Evidence observed | Where | Severity (1–3) |
|---|---|---|---|
| H — Habitat loss | |||
| I — Invasive species | |||
| P — Pollution | |||
| P — Population | |||
| O — Overharvesting | |||
| Management seen |
Analysis
- Complete Table 1.1 from your visit or the supplied description. Give at least one piece of evidence for each letter, plus the management you saw. 8
- Which letter had the most evidence? Which threat do you judge most serious at this site? Justify your choice — they need not be the same. 4
- Choose one observation that belongs to more than one HIPPO letter, and explain why. 3
- For each of the five letters, propose one mitigation measure that would work at this particular site. 5
- The CAPS debate. A developer proposes a 200-berth marina at the estuary mouth, promising jobs and tourism. Write four arguments for, four against, and your own recommendation, with any conditions you would attach. 10
- Explain why protecting only the estuary itself cannot protect the estuary. Use the word catchment. 3
Aim
To measure the amount and type of litter on a beach, and to use the types to work out where it came from.
Method
- Find the strandline — the line of seaweed and debris left by the most recent high tide.
- Mark out 100 m along it. Your survey strip is 2 m wide, centred on the strandline: an area of 200 m².
- Wearing gloves, walk the strip slowly and pick up every item bigger than a bottle cap. Sort as you go into the ten categories of Table 2.1, and tally them.
- Weigh the full bags. Then dispose of everything properly — this survey is also a clean-up.
- Note the beach's position: is there a river mouth, a stormwater outlet, a car park or a fishing spot nearby?
Supplied data — two Eastern Cape beaches, 100 m × 2 m strandline transects
Beach A is a busy city beach 400 m from a river mouth and a stormwater outlet. Beach B is a remote beach inside a marine protected area, reached by a 3 km walk. Both were surveyed on the same day, at the same stage of the tide.
| Category | Beach A | Beach B |
|---|---|---|
| Plastic bottles | 18 | 4 |
| Bottle caps and lids | 46 | 9 |
| Food wrappers and packets | 62 | 6 |
| Straws and earbud sticks | 31 | 2 |
| Polystyrene pieces | 27 | 5 |
| Fishing line, rope and net | 9 | 14 |
| Cigarette butts | 74 | 3 |
| Glass | 7 | 1 |
| Metal cans | 11 | 2 |
| Other | 15 | 4 |
Mass collected: Beach A 3.8 kg; Beach B 1.6 kg (most of it one tangle of fishing net).
Results
| Category | Tally | Total |
|---|---|---|
| Plastic bottles | ||
| Bottle caps and lids | ||
| Food wrappers and packets | ||
| Straws and earbud sticks | ||
| Polystyrene pieces | ||
| Fishing line, rope and net | ||
| Cigarette butts | ||
| Glass | ||
| Metal cans | ||
| Other |
Analysis
- Draw a bar graph comparing the ten categories on Beach A and Beach B (or your beach and Beach B), with the two beaches side by side for each category. Marks: title (1), labelled axes (2), scale (1), accurate bars (2), key (1), neatness and ruled bars (1). 8
- Calculate the total number of items on each beach, and the litter density in items per square metre. 4
- Calculate the percentage of items on each beach that were plastic, stating which categories you counted as plastic. Comment on the difference. 4
- Sort the categories into those that come mainly from land (beach-goers, streets, rivers) and mainly from the sea (boats and fishing). Which source dominates each beach? Suggest why. 5
- Choose the two most common categories on Beach A. For each, describe one way it harms marine life. 4
- Explain why one survey is not enough to judge whether a beach's litter problem is getting worse, and describe how you would monitor it properly. 4
- Propose three mitigation measures aimed at the main sources of Beach A's litter. 3
Aim
To compare the numbers of the invasive Mediterranean mussel and the indigenous brown mussel at three heights on a rocky shore, and to explain the pattern.
Know your mussels
Mediterranean mussel — the invader
Blue-black to dark purple outside. Broad, with the shell flaring wider towards the back, giving a rounded-triangular outline.
Brown mussel — the local
Brown to reddish-brown, sometimes tinged green. Longer and narrower, with straighter sides and a smoother outline.
Young mussels of both species are hard to tell apart. Count only mussels longer than about 3 cm, and record any you cannot identify as "unsure".
Method
- Go at spring low tide. Find a stretch of rocky shore where mussel beds run from high on the rocks down to the low-water line.
- Divide the mussel beds into three zones: upper (the highest mussels), middle and lower (nearest the water).
- In each zone, place the quadrat at five spots chosen at random — for example, walk a random number of paces from 1 to 10 between each placing.
- In each quadrat, count the Mediterranean mussels and the brown mussels you can see. Do not remove any.
- Photograph each quadrat so you can re-count at home.
Supplied data — a south-coast rocky shore, five 0.25 m² quadrats per zone
| Zone | Q1 M / B | Q2 M / B | Q3 M / B | Q4 M / B | Q5 M / B |
|---|---|---|---|---|---|
| Upper | 34 / 2 | 28 / 0 | 41 / 3 | 30 / 1 | 37 / 4 |
| Middle | 18 / 16 | 22 / 12 | 15 / 19 | 20 / 14 | 17 / 18 |
| Lower | 3 / 38 | 5 / 44 | 2 / 35 | 6 / 41 | 4 / 39 |
Results
| Zone | Q1 | Q2 | Q3 | Q4 | Q5 | Mean M | Mean B |
|---|---|---|---|---|---|---|---|
| Upper | |||||||
| Middle | |||||||
| Lower |
Analysis
- Calculate the mean number of each species per quadrat in each zone. Show one calculation in full. 6
- Calculate the percentage of mussels in each zone that were Mediterranean mussels. 3
- Draw a bar graph of the mean counts of both species in the three zones. Marks: title (1), labelled axes (2), scale (1), accurate bars (2), key (1), ruled bars (1). 8
- Describe the pattern shown by your graph. 3
- Suggest an explanation for the pattern, using what you know about conditions at different heights on the shore. 4
- Why were the quadrats placed at random, and why were five used in each zone rather than one? 3
- On parts of the west coast, the Mediterranean mussel has displaced indigenous species almost completely. Using your data, would you say the invader is displacing the brown mussel on this shore, or sharing it? Justify your answer. 4
- Give two reasons why this survey must not involve collecting any mussels. 2
Aim
To use three real South African cases to identify HIPPO impacts, judge the quality of the evidence, and plan mitigation.
The cases
These are summaries written for this sheet from published scientific and news reports. The facts are real; the wording is the course's own.
Case A — the Elands Bay rock lobster walk-outs
Every few years, West Coast rock lobsters crawl out of the sea at Elands Bay and die on the beach. The worst event, in 1997, stranded about 2 000 tonnes, of which about 16% were returned to the sea alive. About 200 tonnes walked out in 2015, and about 500 tonnes in 2022.
Scientists traced the 1997 event to a dense bloom of dinoflagellates whose decay used up the oxygen in the water. Plankton blooms here are fed mainly by the natural upwelling of nutrient-rich water. CAPS notes that "some scientists have argued" that nutrient pollution could also be a cause.
Case B — St Croix's penguins and the ships
In 2016, ship-to-ship refuelling ("bunkering") began in Algoa Bay, and the number of ships anchored there rose sharply. Researchers estimated that underwater noise roughly doubled. Over the same years, African penguin breeding pairs on St Croix Island fell from about 8 500 in 2016 to about 1 200 in 2022.
The researchers noted that the penguins were already struggling because industrial fishing had made their prey — sardine and anchovy — scarcer. After bunkering in the bay was stopped, later reports described the colony as starting to recover.
Case C — the MV Treasure oil spill
On 23 June 2000, the ore carrier MV Treasure sank between Robben and Dassen islands, the two most important African penguin colonies of the time, releasing heavy fuel oil. About 19 000 oiled penguins were captured, cleaned and cared for, most of them successfully released.
About 19 500 unoiled penguins were also caught and driven about 800 km east to Port Elizabeth (now Gqeberha), then released. They swam home — most within a month — by which time much of the oil had been cleaned up. It remains the largest animal rescue of its kind.
Practice — two headlines about one invented event
Headline X: "FACTORY POISONS BAY — THOUSANDS OF FISH DEAD!" (one photograph; one angry fisherman quoted).
Headline Y: "Minor fish incident 'entirely natural', says plant manager" (no data; the only person quoted works for the factory).
Analysis
- For each of Cases A, B and C, identify the HIPPO letter or letters involved, and justify each choice. 6
- Case B: calculate the percentage decrease in St Croix's breeding pairs from 2016 to 2022. Show your working. 3
- Case B: two pressures acted at the same time. Explain why that makes it hard to prove which one caused the decline — and what the recovery after bunkering stopped can add to the evidence. 4
- Case A: is it fair to call the Elands Bay walk-outs pollution? Use the evidence in the case. 4
- Case C: explain why moving unoiled penguins 800 km away was a sensible mitigation measure. 3
- The practice headlines: which one overstates and which understates? Give one reason for each, then write one headline that a scientist would accept. 4
- Choose one of Cases A, B or C and write a mitigation plan with three parts: how to check the impact (monitoring), how to control it, and how to rehabilitate the damage. 6
Extension — audit a menu
Take the free SASSI app or website (the Southern African Sustainable Seafood Initiative) to a local fish shop, supermarket counter or restaurant menu. List every fish and seafood on offer and give each one its SASSI colour — green (best choice), orange (think twice) or red (don't buy). What percentage is green? Which red-listed species did you find, and what would you suggest the seller offers instead? It is the O in HIPPO, measured at the point where you can actually do something about it.
Memo — worked answers and mark allocation (does not print)
Total: 128 marks — Investigation 1: 33 · Investigation 2: 32 · Investigation 3: 33 · Investigation 4: 30.
Investigation 1 — find HIPPO
- Q1 (8): One mark per letter with valid evidence (5), one for severity scores that are plausible and consistent (1), two for management seen (2). From the supplied visit — H: salt pans and industry on former salt marsh; houses on the floodplain; bait pumping churning the mudflats; boats over the eel-grass. I: the sea squirt on the jetty. P (pollution): litter on the high-tide line; sewage overflows; the stormwater canal. P (population): new housing; the suburbs the canal drains; many people on the flats. O: heavy bait collection; undersized fish kept. Management: bait rules and limits, the fisheries control officer, bins, the water-quality sign.
- Q2 (4): Most evidence — usually pollution or habitat loss (1), with a count (1). Most serious — any reasoned choice (2), e.g. pollution from the catchment, because it arrives with every storm and cannot be controlled at the estuary itself. Reward a learner who sees that the most visible threat is not necessarily the most serious.
- Q3 (3): E.g. bait pumping is overharvesting (removing prawns) and habitat damage (churning the mudflat) (1 + 1), explained (1). Or new housing: population and habitat loss.
- Q4 (5): One appropriate, site-specific measure per letter (5), e.g. H — protect remaining salt marsh, restrict boat speed over eel-grass; I — check and clean hulls, monitor jetties for new species; P — fix sewage overflows, litter traps on the canal, more bins emptied more often; P — EIAs and a development setback line on the floodplain; O — enforce bait and size limits.
- Q5 (10): Four valid arguments for (4) — jobs, tourism revenue, a safe harbour, investment in the area. Four valid arguments against (4) — loss of habitat at the mouth, changed water flow and sediment, more boat traffic and pollution, more invasive hitchhikers, disturbance of nursery grounds. A clear recommendation with at least one sensible condition (2), e.g. "only after a full EIA, with no dredging of eel-grass beds and a pump-out station for boat sewage". Either recommendation can earn full marks if it is reasoned.
- Q6 (3): An estuary receives everything carried by the river from its whole catchment (1) — sewage, farm runoff, sediment and litter from far inland (1) — so it can only be protected by managing what happens upstream too (1).
Investigation 2 — beach-litter transect
- Q7 (8): Mark against the listed criteria. Bars for the two beaches must sit side by side for each category, with a key.
- Q8 (4): Beach A: 300 items (1); Beach B: 50 items (1). Area = 100 × 2 = 200 m². Density A = 300 ÷ 200 = 1.5 items/m² (1); B = 50 ÷ 200 = 0.25 items/m² (1).
- Q9 (4): Plastic categories stated — bottles, caps, wrappers, straws, polystyrene and fishing line (1). A = 18 + 46 + 62 + 31 + 27 + 9 = 193; 193 ÷ 300 × 100 = 64% (1). B = 4 + 9 + 6 + 2 + 5 + 14 = 40; 40 ÷ 50 × 100 = 80% (1). Comment: Beach B has far less litter, but a larger share of it is plastic — plastic lasts longest and travels furthest at sea (1). Accept other defensible definitions — e.g. counting cigarette filters as plastic (they are cellulose acetate) — if stated and calculated correctly.
- Q10 (5): Land-based: wrappers, caps, bottles, straws, butts, cans, glass (1). Sea-based: fishing line, rope and net (1). Beach A is dominated by land-based litter (1) — it is near a river mouth, a stormwater outlet and crowds (1). Beach B has few land items but more fishing gear than A, so much of its litter arrives from the sea, carried by currents or lost from boats (1).
- Q11 (4): Two marks per category. Cigarette butts: leach toxins into water; mistaken for food and swallowed. Food wrappers: ingested by turtles, birds and fish, blocking the gut; break into microplastics. Caps: swallowed by seabirds, causing starvation. Credit any two accurate mechanisms per item.
- Q12 (4): One survey is a snapshot — litter varies with storms, tides, holidays and wind (2). Monitor by repeating the same transect, the same way, at the same stage of tide, regularly (e.g. monthly) for at least a year, and compare the trend (2).
- Q13 (3): Any three targeted measures, e.g. a litter trap on the stormwater outlet; more bins, emptied often, and butt bins at the beach; a ban or charge on single-use plastics sold at the beach; anti-litter campaigns; regular clean-ups.
Investigation 3 — the invader survey
- Q14 (6): Upper: M = (34 + 28 + 41 + 30 + 37) ÷ 5 = 170 ÷ 5 = 34.0; B = 10 ÷ 5 = 2.0. Middle: M = 92 ÷ 5 = 18.4; B = 79 ÷ 5 = 15.8. Lower: M = 20 ÷ 5 = 4.0; B = 197 ÷ 5 = 39.4. (1 per zone-pair correct, 3; working shown, 1; all six correct, 2.)
- Q15 (3): Upper 34 ÷ 36 = 94%; middle 18.4 ÷ 34.2 = 54%; lower 4 ÷ 43.4 = 9% (1 each).
- Q16 (8): Mark against the listed criteria.
- Q17 (3): The Mediterranean mussel dominates the upper zone (1), the brown mussel dominates the lower zone (1), and the two are roughly equal in the middle (1).
- Q18 (4): The upper shore is exposed to air, heat and drying for longer at each low tide; the lower shore takes the strongest wave action (2). Research on our south coast suggests the brown mussel attaches more strongly and is better suited to the wave-beaten lower shore, while the invader copes better higher up, where the brown mussel is limited (2). Accept any well-reasoned explanation linking a species trait to a zone's conditions.
- Q19 (3): Random placement avoids bias — choosing the "interesting" patches (1). Five quadrats give a more reliable average, because counts vary from place to place (1), and allow the variation to be seen (1).
- Q20 (4): Sharing, on this shore (1): the brown mussel still dominates the lower zone at about 39 per quadrat, and the middle zone is mixed (2). But the invader has taken the upper shore almost entirely, so it is a real presence that needs monitoring for change (1). A reasoned "partly displacing" answer can earn full marks.
- Q21 (2): Collecting needs a permit and may be illegal, especially in an MPA (1); removing mussels damages the bed and the animals living in it, and would change the very numbers being surveyed (1).
Investigation 4 — three real cases
- Q22 (6): Two marks per case. A: pollution (nutrients) — possibly, as argued — with natural upwelling as the main driver; accept O as a consequence for the fishery. B: pollution (noise; oil risk) and overharvesting (prey depletion); accept population (port growth). C: pollution (oil).
- Q23 (3): Decrease = 8 500 − 1 200 = 7 300 (1). 7 300 ÷ 8 500 × 100 (1) = about 86% (1).
- Q24 (4): When two pressures act together, either could explain the decline, and they may add to each other (2). If the colony recovers after bunkering stops while prey scarcity continues, that is evidence that the noise was an important cause — a "natural experiment" (2).
- Q25 (4): Not on present evidence (1): the walk-outs are caused by low oxygen when a bloom decays (1), and the blooms are fed mainly by natural upwelling (1). Pollution may add to it, but CAPS itself says only that "some scientists have argued" this — it is not established (1).
- Q26 (3): Penguins return to their home colony (1). By the time the relocated birds swam back, much of the oil had been cleaned up (1), so thousands of birds were kept from becoming oiled at all, which is far safer and cheaper than cleaning them afterwards (1).
- Q27 (4): X overstates: one photo and one emotional quote, a cause asserted without evidence (1). Y understates: no data, and the only source has a stake in the outcome (1). A good headline states what is known and what is not (2), e.g. "Fish die-off near factory — tests under way to find the cause."
- Q28 (6): Two marks each for a sensible check (regular measured monitoring — counts, oxygen, noise), control (stop or limit the cause — rules, permits, closures, oil-handling standards) and rehabilitate (rescue and rehabilitation, habitat restoration, restocking where appropriate) step, matched to the chosen case.
Marking note. This topic's CAPS depth instruction asks learners to "understand and apply multidisciplinary skills" — so Q2, Q5, Q20, Q25 and Q27 deliberately have more than one acceptable answer. Mark the reasoning and the use of evidence, not agreement with the memo's example.