Capstone
Oceanography Fundamentals
Course 1 · Chapter 10 · Capstone: Exploring and Protecting the Ocean
On 23 January 1960 the bathyscaphe Trieste, carrying the Swiss engineer Jacques Piccard and US Navy lieutenant Don Walsh, reached the bottom of the Challenger Deep, close to 11,000 metres down (check). They stayed about twenty minutes, saw what they thought was a flatfish on the bottom (a claim since doubted) and came back up. Then nobody went again for over fifty years, until the film director James Cameron's solo dive in 2012 and the 2019 dives by Victor Vescovo (check the dates). Most of what we have learned since has come from instruments, not people. This final chapter reviews how the ocean is studied today, what threatens it, how it is governed, and how to read what is written about it.
How We Study the Ocean Now
| Tool | What it does | Strength |
|---|---|---|
| Research ships | Carry instruments, nets and sonar; take water samples with bottle rosettes | Most flexible; expensive and slow |
| Satellites | Measure sea-surface temperature, height, colour (chlorophyll), winds and ice | Global coverage, every few days; surface only |
| Argo floats | About 4,000 drifting profilers report temperature and salinity to about 2,000 m | Continuous global subsurface record (check) |
| Moorings and tide gauges | Fixed instruments, such as the Atlantic overturning array (Chapter 7) | Long records at a point |
| Gliders and autonomous vehicles | Robots that glide or propel themselves along a programmed path | Cheap per day; can enter storms and under ice |
| Remotely operated vehicles (ROVs) | Tethered robots with cameras and arms, driven from a ship | Detailed work at any depth |
| Models | Computer simulations of currents, waves, tides and climate | Fill gaps and make forecasts; need observations to check them |
Sound and chemistry are used too: hydrophones listen for whales and earthquakes, and DNA in a water sample can reveal which species were nearby (environmental DNA). The United Nations has declared 2021 to 2030 the Decade of Ocean Science for Sustainable Development, with the aim of coordinating more of this effort and mapping the whole seafloor (check).
The Main Pressures
Warming, acidification, deoxygenation
The climate effects of Chapter 8, acting together on reefs, fisheries and polar ecosystems.
Overfishing and bycatch
Taking fish faster than they can reproduce (Chapter 9), and catching non-target animals such as turtles, seabirds and dolphins.
Pollution
Plastic, fertiliser run-off, sewage, oil and noise, described below.
Habitat loss
Coastal development, trawling of the seabed, and loss of mangroves, seagrass and reefs.
New industries
Offshore wind, aquaculture, and the possibility of deep-sea mining of mineral nodules, which raise questions about benefits and damage that are still being debated.
Invasive species
Animals and plants carried in ballast water and on ship hulls to places where they have no natural enemies.
Who Owns the Sea?
The legal framework is the United Nations Convention on the Law of the Sea (UNCLOS), agreed in 1982 and in force from 1994 (check). Its main ideas:
- Territorial sea. Up to 12 nautical miles from the coast belong to the coastal state, with a right of innocent passage for ships.
- Exclusive economic zone (EEZ). Up to 200 nautical miles, where the coastal state controls fishing, oil and gas, and other resources. About a third of the ocean falls within EEZs (check).
- The high seas. Beyond the EEZs, roughly two-thirds of the ocean, are open to all and historically poorly regulated.
In 2023 the member states of the United Nations agreed a treaty on the conservation of biodiversity in areas beyond national jurisdiction, often called the High Seas Treaty, to create protected areas and set rules for environmental assessment there. It needed 60 countries to ratify it before taking effect, and the latest status should be checked (check).
Protection in Practice
| Measure | What it does | Limits |
|---|---|---|
| Marine protected areas | Restrict fishing or other activities in a defined zone | Only fully or highly protected zones show the largest benefits; many areas are protected on paper only |
| Catch limits and quotas | Cap the total take of a species | Need good stock assessments and enforcement |
| Gear rules | Mesh sizes, bans on destructive trawling | Hard to police at sea |
| Pollution law | The MARPOL convention for ships; limits on discharges and run-off | Land-based sources are harder to control |
| Targets | The 2022 global biodiversity framework aims to protect 30 per cent of the ocean by 2030 | Only a minority of the ocean is covered so far, and a smaller part strictly (check the latest figure) |
Evidence suggests that well-enforced no-take reserves can increase fish numbers and size inside the reserve and sometimes supply nearby fisheries as the fish spill over (check). The Scottish seas have their own network of marine protected areas, with debate about what activities they should limit.
Reading Ocean Stories Critically
- Is it an observation, a model projection or a guess?
- What exactly was measured, where, over what period?
- Is the number a rate, a total or a share, and what is it compared with?
- Does the headline match the original source and its stated uncertainty?
- Is it local (one bay, one stock) or global?
- Is "the ocean" one thing in the claim? Surface and deep, Atlantic and Pacific behave differently.
What You Now Know
| Chapter | Key idea |
|---|---|
| 1 | The ocean covers 71 per cent of Earth, is deep and little mapped |
| 2 | The seafloor is made at ridges and recycled at trenches |
| 3 | Salinity, temperature and pressure set the density and layers of seawater |
| 4 | Wind makes waves; tsunamis are a different kind of wave |
| 5 | Tides come from the Moon and Sun and are shaped by the basin |
| 6 | Wind and rotation drive gyres, boundary currents and upwelling |
| 7 | Density drives a slow global overturning over centuries |
| 8 | The ocean stores heat and carbon, and is changing |
| 9 | Plankton support the food web; vents show life without sunlight |
Exercises
A country has a coastline whose 200-nautical-mile exclusive economic zone covers 500,000 square kilometres. A marine protected area of 60,000 square kilometres is created in it, of which 20,000 square kilometres is fully no-take. Calculate the percentage of the EEZ that is protected at all, and the percentage that is fully protected. How do they compare with a 30 per cent target?
Choose one ocean tool from the table (satellite, Argo float, ship, glider, ROV) and say which of the earlier chapters' questions it could best answer (for example the speed of the Gulf Stream, the depth of the thermocline, or the age of a deep water mass), and why the others would be less suited.
Capstone: find a recent news story about the ocean and apply the six-point checklist. Write a short assessment (150 to 250 words) of what the story claims, what the evidence is, and which chapter of this course helps you judge it.
Quick Reference
- Tools: ships, satellites, Argo floats, moorings, gliders, ROVs, models
- Pressures: climate change, overfishing, pollution, habitat loss, new industries, invasives
- Law: UNCLOS: 12 nm territorial sea, 200 nm EEZ, high seas beyond
- Protection: marine protected areas, quotas, gear rules, the 30 by 30 target
- Critical reading: observation or projection, what was measured, rate or total, source, scale
- Check: plastic estimate, treaty status, protection percentages