WACE Marine Maritime Studies ATAR cheat sheet

Marine environments divide into pelagic (open water) and benthic (seabed) zones; the neritic zone covers water above the continental shelf and is the most productive area.

Salinity of open ocean averages about 35 parts per thousand; estuarine water is brackish (0.5-30 ppt) because freshwater mixes with seawater.

Seawater density rises with increasing salinity and falling temperature; density maximum occurs near freezing point, unlike freshwater at 4 degrees C.

Thermocline: a layer of rapid temperature decrease separating warm surface water from cold deep water; it inhibits vertical mixing.

Coriolis effect deflects moving water and air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.

Spring tides occur at new and neap tides at quarter moon phases; tidal range is greatest when Sun and Moon align.

Longshore drift transports sediment parallel to the coast; groynes and breakwaters interrupt it and can cause downdrift erosion.

Wave height depends on wind speed, fetch (distance over open water) and duration; breaking occurs when depth is about 1.3 times wave height.

Trophic levels: producers (phytoplankton) to primary consumers (zooplankton) to higher predators; roughly 90% of energy is lost at each transfer.

Phytoplankton supply roughly half of global photosynthetic oxygen production and form the base of most marine food webs.

Bioaccumulation is build-up of a substance within one organism; biomagnification is its increase in concentration up the food chain (e.g. mercury, PCBs).

Maximum sustainable yield (MSY) is the largest catch that can be taken indefinitely; exceeding it causes stock collapse.

Bycatch is non-target catch; turtle excluder devices and pingers reduce it but do not eliminate it.

Eutrophication: nutrient enrichment causes algal blooms, then oxygen depletion (hypoxia) and dead zones when algae decay.

Marine protected areas restrict extractive use; no-take reserves show higher biomass and spillover of adults into fished areas.

Ocean acidification results from dissolved CO2 forming carbonic acid, lowering pH and impairing calcification in corals and shellfish.

Archimedes' principle: buoyant force equals the weight of displaced fluid; a floating vessel displaces water equal to its own mass.

Reserve buoyancy is the watertight volume above the waterline; it allows a vessel to carry added weight and resist flooding.

Freeboard is the vertical distance from waterline to the freeboard deck; greater freeboard generally improves seaworthiness.

Centre of gravity (G) acts downward, centre of buoyancy (B) acts upward; for stable equilibrium G must lie below the metacentre M.

GM (metacentric height) = KM - KG; a small positive GM gives a stiff ship (rapid roll), a large GM a tender ship (slow, deep roll).

GZ is the righting lever; the area under the GZ curve indicates dynamic stability, and the curve must not be exceeded by heeling moments.

Angle of loll is an unstable list to either side at zero GM; it is corrected by lowering G, not by shifting ballast across.

Block coefficient (Cb) = volume of displacement divided by (length x breadth x draught); higher Cb indicates a fuller hull form.

Four-stroke cycle: induction, compression, power, exhaust; two-stroke completes the cycle in one revolution with scavenging ports.

Compression ignition (diesel) relies on high compression ratio to ignite fuel; spark ignition uses a spark plug and lower compression.

Propeller pitch is the theoretical axial advance per revolution; slip = (pitch x revolutions - actual speed) / (pitch x revolutions).

Fixed-pitch propellers suit one service speed; controllable-pitch propellers allow thrust reversal without changing engine direction.

Cavitation occurs when local pressure falls below vapour pressure, forming bubbles that collapse and erode propeller blades.

Marine electrical systems commonly use 24 V DC or 240/415 V AC; AC frequency is 50 Hz or 60 Hz depending on the system.

Batteries in series add voltage, in parallel add capacity; amp-hour capacity is reduced by high discharge rates (Peukert effect).

Cooling systems are direct (raw water) or indirect (fresh water with heat exchanger); closed systems reduce corrosion and scaling.

Latitude is measured 0-90 degrees north or south of the equator; longitude 0-180 degrees east or west of Greenwich.

Speed, distance, time: distance = speed x time; 1 knot = 1 nautical mile per hour; 1 nautical mile = 1852 m.

True bearing = magnetic bearing + variation (east add, west subtract); compass bearing = magnetic bearing + deviation.

Rule of thumb: variation/deviation east is least (subtract) when converting compass to true, and best (add) when converting true to compass.

Under COLREGs, a power-driven vessel crossing must give way to a vessel on her starboard side and avoid crossing ahead.

Beaufort scale relates wind speed to sea state; force 7 (near gale) gives 28-33 knots with sea heaping up.

A passage plan includes appraisal, planning, execution and monitoring, with no-go areas, abort points and contingency anchorages.

Dead reckoning uses course and speed from a known position; estimated position adds leeway and tidal set and drift.

SOLAS is the key convention for construction, fire protection, life-saving appliances and safe operation of ships.

MARPOL Annex I covers oil, Annex IV sewage, Annex V garbage and Annex VI air pollution including sulphur limits.

STCW sets minimum training and certification standards for seafarers, including basic safety training and watchkeeping hours.

GMDSS distress alerting uses DSC on VHF channel 70, EPIRB (406 MHz) and SART (9 GHz radar transponder).

MAYDAY = distress, PAN PAN = urgency, SECURITE = safety; each is repeated three times on VHF channel 16.

Lifejacket and immersion suit reduce heat loss; cold shock and hypothermia are the main survival threats in cold water.

Fire triangle: fuel, oxygen, heat; extinguishing removes one leg; class A (solids), B (flammable liquids), C (gases), E (electrical).

Man overboard drill: shout and point, release lifebuoy, helm hard over, mark position (MOB button), recover with lee-side approach.

Shipping carries roughly 80-90% of world trade by volume, with bulk carriers, container ships and tankers the main types.

Charter types: voyage charter (per voyage), time charter (per period), bareboat/demise charter (hire of vessel without crew).

Freight rates respond to supply (fleet capacity, newbuild deliveries) and demand (trade volumes, seasonal cargoes).

Port operations depend on berth availability, turnaround time, pilotage, towage and stevedoring productivity.

Careers include deck officer (OOW, chief mate, master), engineer officer, marine surveyor, port authority officer and hydrographer.

Flag state regulates the vessel; port state control inspects foreign ships for compliance with international conventions.

Marine insurance covers hull and machinery, cargo and P&I (third-party liability); general average shares loss across cargo owners.

Blue economy includes fisheries, aquaculture, tourism, offshore energy and shipping; sustainability requires balancing use and conservation.