Cambridge IGCSE Marine Science 0697

🌊 Cambridge IGCSE Marine Science Formula Sheet 2026

Everything you need for Cambridge IGCSE Marine Science — water properties, marine ecosystems, classification, coral reefs, sustainable fishing, human impact and key sampling formulas.

Water & Currents Ecosystems & Productivity Coral Reefs Sampling Calculations

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Aligned with the latest 2026 syllabus and board specifications. This sheet is prepared to match your exam board’s official specifications for the 2026 exam series.

All the Core Marine Science Knowledge in One Formula Sheet

Cambridge IGCSE Marine Science (0697) covers oceans as a physical, chemical and biological system. This formula sheet brings together water properties, marine ecosystems and productivity, classification of marine organisms, coral-reef biology, the fishing industry, human impact, conservation strategies and the key practical calculations — including the Lincoln index, Simpson's diversity and maximum sustainable yield.

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Water properties — density, salinity, pH, light zones and ocean currents

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Marine ecosystems, food webs and coral-reef biology

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Sustainable fishing, MSY, aquaculture and bycatch

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Practical sampling — Lincoln index, Simpson's diversity, Winkler titration

Topic 1 — Water Properties & Ocean Currents

The physical and chemical properties of seawater that drive marine systems.

Properties of Seawater

Key physical and chemical values for the 2026 syllabus.

Density

Seawater ≈ 1025 kg/m³ | Freshwater ≈ 1000 kg/m³ — saltwater is denser due to dissolved salts

Salinity

Typical seawater ≈ 35‰ (parts per thousand)

pH

Surface ocean ≈ 8.1 (slightly alkaline)

Specific heat capacity

High — oceans absorb large amounts of heat with small temperature change, moderating climate

Latent heat

High — large energy needed for evaporation/freezing, stabilising marine temperatures

Light Zones

Ocean depth zones based on light penetration.

Euphotic

0–~200 m — enough light for photosynthesis

Dysphotic

~200–~1000 m — twilight zone, no photosynthesis but some light

Aphotic

>~1000 m — no light, chemosynthesis only

Ocean Currents

Surface and deep circulation patterns.

Surface currents

Wind-driven — form gyres in each ocean basin

Thermohaline circulation

Deep current driven by temperature and salinity differences (the global 'conveyor belt')

El Niño / La Niña

Periodic warming/cooling of the eastern Pacific — affects upwelling and fisheries (e.g. Peru anchovy)

Upwelling

Cold, nutrient-rich deep water rises to the surface — supports highly productive fisheries

Topic 2 — Marine Ecosystems & Productivity

Zonation, food webs, biomes and key productivity equations.

Zonation

Where organisms live in the ocean.

Pelagic zone

Open water — neritic (over continental shelf) and oceanic (beyond shelf)

Benthic zone

The sea floor — intertidal, sublittoral and abyssal

Food Chains, Webs & Energy Transfer

Trophic levels in marine systems.

Primary producers

Phytoplankton, seaweeds (algae), seagrasses — base of most marine food webs

Energy transfer

Approximately 10% of energy is passed to the next trophic level (the 10% rule)

Productivity Equations

How energy flow is quantified.

GPP

Gross Primary Productivity — total energy fixed by producers

NPP

NPP = GPP − R (where R = energy lost in respiration)

Simpson's diversity index

D = 1 − Σ(n/N)² — higher D means greater biodiversity

Marine Biomes

Major marine habitats covered by the syllabus.

Coral reefs | Mangroves | Seagrass meadows | Kelp forests | Deep sea | Polar seas

Topic 3 — Classification of Marine Organisms

The five-kingdom system applied to marine life.

Five Kingdoms

Higher-level classification.

Animalia | Plantae | Fungi | Protoctista | Prokaryotae

Major Marine Animal Phyla

Key invertebrate and chordate groups.

Cnidaria

Jellyfish, corals, sea anemones — radial symmetry, stinging cells (cnidocytes)

Mollusca

Snails, bivalves, squid, octopus — soft body, often shelled

Arthropoda (crustaceans)

Crabs, lobsters, shrimps — exoskeleton, jointed limbs

Echinodermata

Starfish, sea urchins — radial symmetry, water vascular system

Chordata in the Sea

Marine vertebrates.

Fish

Cartilaginous (sharks, rays) and bony (teleosts) — gills, fins

Marine reptiles

Sea turtles, sea snakes, marine iguanas — air-breathing, scales

Marine mammals

Cetaceans (whales, dolphins), pinnipeds (seals), sirenians (manatees)

Seabirds

Albatross, penguins, gulls — feathers, lay eggs on land

Topic 4 — Coral Reefs

Conditions, types and threats to the world's most diverse marine ecosystem.

Symbiosis & Conditions for Growth

Why reefs grow only in specific environments.

Zooxanthellae

Symbiotic algae living in coral tissue — photosynthesise and provide up to 90% of coral's energy

Temperature

23–29 °C optimal

Salinity

32–42‰

Depth

<50 m (light required for zooxanthellae)

Other

Clear, low-nutrient, well-oxygenated water; firm substrate

Types of Reef

Reef morphology by location.

Fringing

Grow directly from the shore — most common type

Barrier

Separated from shore by a lagoon — e.g. Great Barrier Reef

Atoll

Ring-shaped reef around a lagoon, often on a sunken volcanic island

Coral Bleaching

A major threat to reef survival.

Heat stress (or pollution) → coral expels zooxanthellae → coral turns white → loss of food source → death if conditions persist

Topic 5 — Fishing Industry & Aquaculture

Sustainable yield, fishing methods and bycatch.

Maximum Sustainable Yield

The largest catch that can be taken indefinitely without depleting the stock.

MSY (logistic model)

MSY ≈ rN/4 (where r = intrinsic growth rate, N = carrying capacity, with peak catch at N/2)

Fishing above MSY leads to stock collapse.

Fishing Methods

Techniques and their environmental impact.

Trawling

Towed nets — bottom trawls damage seabed; large bycatch

Purse seining

Net encircles a school then drawn closed — high catch of pelagic species (tuna)

Long-lining

Long line with thousands of baited hooks — bycatch of seabirds, turtles, sharks

Drift nets

Free-floating nets — banned in many areas due to high bycatch

Gill nets

Vertical nets — fish caught by gills

Bycatch & Aquaculture

Reducing pressure on wild stocks.

Bycatch

Non-target species caught during fishing — major sustainability issue

Aquaculture / mariculture

Farming aquatic organisms (salmon, prawns, shellfish, seaweed) — relieves pressure but causes pollution and disease risk

Topic 6 — Human Impact & Climate Change

Pollution, climate change and ocean acidification.

Pollution

Major pollutants in the marine environment.

Oil spills

Smother organisms, reduce O₂ exchange, harm seabirds — e.g. Deepwater Horizon

Eutrophication

Excess nutrients (fertiliser run-off) → algal bloom → decomposition → O₂ depletion → 'dead zones'

Plastic

Macro- and microplastics — entanglement, ingestion, bioaccumulation

Sound pollution

Shipping and sonar disrupt cetacean communication

Thermal pollution

Warm water from power stations reduces dissolved O₂

Climate Change & Ocean Acidification

How rising CO₂ affects the oceans.

Ocean warming

Coral bleaching; species range shifts

Acidification (chemistry)

CO₂ + H₂O → H₂CO₃ → HCO₃⁻ + H⁺ — increased H⁺ lowers pH and reduces carbonate availability for shells/skeletons

Sea-level rise

Eustatic (global, due to thermal expansion + ice melt) and isostatic (local, due to land movement)

Topic 7 — Conservation & Management

International tools to protect marine life.

Conservation Strategies

Key mechanisms in marine conservation.

MPAs

Marine Protected Areas — restrict fishing or other activities to protect biodiversity

IUCN Red List

Categorises species: Least Concern → Near Threatened → Vulnerable → Endangered → Critically Endangered → Extinct in the Wild → Extinct

CITES

Convention on International Trade in Endangered Species — controls trade in protected species (Appendices I, II, III)

Sustainable fishing

Quotas, mesh-size regulation, closed seasons, no-take zones, eco-labelling (MSC)

Practical Skills — Sampling & Titration

Field and laboratory techniques expected on the syllabus.

Sampling Techniques

How to estimate marine populations and abundance.

Quadrats

Random or systematic placement on rocky shore to estimate density of sessile organisms

Transects

Line or belt transects to study zonation along an environmental gradient

Lincoln index (mark-recapture)

N = (n₁ × n₂) / m₂ — where n₁ = first sample marked, n₂ = second sample, m₂ = marked individuals recaptured

Water-quality Measurements

Key seawater chemistry techniques.

Dissolved oxygen

Winkler titration — chemical fixation followed by titration with sodium thiosulfate against starch indicator

Salinity

Hydrometer (density), refractometer or conductivity meter

How to Use This Formula Sheet

Boost your Cambridge exam confidence with these proven study strategies from our tutoring experts.

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Memorise the Reference Values

Density 1025 kg/m³, salinity 35‰, surface pH ≈ 8.1, coral temperature 23–29 °C — these specific values turn up repeatedly in short-answer questions.

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Practise the Formulas

Be fluent applying NPP = GPP − R, Simpson's D = 1 − Σ(n/N)², and the Lincoln index N = (n₁ × n₂) / m₂ — all are common calculation questions.

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Link Coral Reef Conditions to Threats

When you learn the conditions for reef growth, also learn the threat that disrupts each (warming → bleaching, acidification → weaker skeletons, sediment → light reduction).

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Compare Fishing Methods on Bycatch

For each fishing method, state target species, environmental impact and bycatch risk — examiners reward applied evaluation, not just description.

Formula Sheet FAQ

Quick answers about this free PDF and how to use it for exam revision and active recall.

Is the Cambridge IGCSE Marine Science Formula Sheet 2026 free to download as a PDF?

Yes. This Tutopiya formula sheet is free to use and you can download it as a PDF from this page for offline revision. There is no payment or account required for the PDF download.

What Marine Science topics and equations does this formula sheet cover?

This page groups key Marine Science formulas in one place for revision. Master Cambridge IGCSE Marine Science (0697) with this 2026 formula sheet. Covers water properties, marine ecosystems, classification, coral reefs, fishing, human impact, conservation and key practical-skill calculati… Always cross-check with your official syllabus and past papers for your exam session.

Can I use this instead of the official exam formula booklet in the exam?

No. In the exam you must follow only what your exam board allows in the hall—usually the official formula booklet or data sheet where provided. This page is a revision and teaching aid, not a replacement for board-issued materials.

Who is this formula sheet for (Secondary)?

It is written for students preparing for assessments at Secondary in Marine Science, including classroom revision, homework support, and independent study. Teachers and tutors can also share it as a quick reference.

How should I revise with this formula sheet?

Work through past paper questions, quote the correct formula before substituting values, and check units and notation every time. Pair this sheet with timed practice and mark schemes so you see how examiners expect working to be set out.

Where can I get more help with Marine Science revision?

Explore Tutopiya’s study tools, past paper finder, and revision checklists linked from our tools hub, or book a trial lesson with a subject specialist for personalised support alongside this formula reference.

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This formula sheet aligns with Cambridge Assessment International Education IGCSE Marine Science (0697) syllabus content for the 2026 series.

Always quote specific values (salinity in ‰, temperature in °C, depth in m) where the syllabus expects them — precision earns marks.