QCAA Marine Science EA flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Thermohaline circulation

Large-scale deep-ocean overturning driven by differences in seawater density, which depend on temperature and salinity. Cold, salty water sinks at high latitudes and drives slow global transport of heat and nutrients.

Pycnocline

A layer in the ocean where density increases rapidly with depth. It separates lighter surface water from denser deep water and strongly resists vertical mixing, limiting nutrient exchange between layers.

Coriolis effect

Apparent deflection of moving fluids and objects caused by Earth's rotation. Deflection is to the right in the Northern Hemisphere and to the left in the Southern Hemisphere, increasing with latitude and speed.

Ekman transport

Net movement of the wind-driven surface layer, which is about 90 degrees to the right of the wind in the Northern Hemisphere and to the left in the Southern Hemisphere, due to Coriolis deflection.

Coastal upwelling

Rise of cold, nutrient-rich deep water to the surface, typically when winds blow parallel to the coast and Ekman transport moves surface water offshore. It fuels high primary productivity and productive fisheries.

Spring and neap tides

Spring tides are large tidal ranges at new and full moon when solar and lunar forces align. Neap tides are small ranges at quarter moons when the two forces partly oppose each other.

Wave refraction

Bending of wave crests as they approach shore at an angle because the shallower part of the wave slows first. Energy concentrates on headlands and disperses in bays, shaping coastal erosion patterns.

Longshore drift

Net movement of sediment along a shoreline caused by waves approaching at an oblique angle, carrying material up the beach and back down in a zigzag path in the dominant drift direction.

Logistic population growth

Growth described by dN/dt = rN(K − N)/K, where N is population size, r is the intrinsic growth rate and K is carrying capacity. Growth slows as the population approaches K.

Carrying capacity

The maximum population size of a species that an environment can sustain indefinitely given the available food, space, oxygen and other limiting resources, denoted K in population growth models.

Keystone species

A species whose influence on community structure is disproportionately large relative to its abundance. Its removal triggers cascading changes, such as urchin barrens forming after predator loss.

Trophic cascade

Indirect ecological effect that propagates down food webs when a predator is added or removed, altering abundance of intermediate consumers and then of primary producers or grazers at lower levels.

Ecological succession

Predictable sequence of community change over time, from pioneer colonisers to more competitive later species. Disturbance events can reset the sequence back to an earlier stage.

Zooxanthellae

Symbiotic photosynthetic algae living within coral tissues. They supply the coral with most of its energy and give it colour; their loss under thermal stress causes coral bleaching and possible mortality.

Shannon diversity index

A biodiversity measure calculated as H = −Σ pᵢ ln pᵢ, where pᵢ is the proportion of individuals in species i. It increases with both species richness and evenness of abundance.

Nursery habitat

Coastal habitat such as mangroves, seagrass beds or estuaries where juveniles of many species find shelter, food and low predation, then move to adult habitats as they mature.

Primary productivity

Rate at which autotrophs convert inorganic carbon into organic matter through photosynthesis or chemosynthesis. In the ocean it is limited mainly by light, nutrients, temperature and grazing pressure.

Maximum sustainable yield

The largest catch that can be removed from a stock indefinitely without depleting it. In the logistic model it occurs near half the unfished carrying capacity, at intermediate fishing effort.

Tragedy of the commons

Overexploitation of a shared, unowned resource because each user gains the full benefit of extraction while costs are spread across all users, driving effort beyond sustainable levels.

Marine protected area

A geographically defined marine zone managed for conservation. No-take reserves are most effective when large, well enforced, and connected to other areas by larval dispersal and adult movement.

Bycatch

Non-target organisms caught incidentally during fishing, including juveniles, protected species and non-commercial animals. Bycatch reduction devices and gear modifications are used to lower this mortality.

Individual transferable quota

A management tool allocating fishers a share of a total allowable catch that can be bought or sold. It gives holders a long-term stake in stock health and reduces the race to fish.

Eutrophication

Nutrient enrichment of coastal waters, often from runoff, causing algal blooms. Decomposition of the bloom consumes oxygen, producing hypoxia, fish kills and dead zones.

Adaptive management

A cyclical approach that monitors resource condition, adjusts regulations in response to evidence, and then re-evaluates. It treats management as an ongoing experiment rather than a fixed rule.

Integrated coastal zone management

Coordinated planning of coastal activities across sectors and jurisdictions, balancing development, conservation, tourism and fisheries while accounting for cumulative and cross-boundary impacts.

Aquaculture

Farming of aquatic organisms under controlled conditions. It can reduce pressure on wild stocks but may cause nutrient loading, escapees, disease transfer and demand for wild-caught feed.

Validity in investigations

The extent to which a study measures what it claims to measure. It requires controlled variables, an appropriate control treatment and manipulation of only the independent variable.

Reliability in investigations

The consistency of repeated measurements. It is improved by increasing replication, standardising procedures, calibrating instruments and having consistent observers or sampling methods.

Accuracy versus precision

Accuracy is closeness to the true value; precision is closeness of repeated measurements to each other. Random error reduces precision, while systematic error shifts results away from the true value.

Mark-recapture estimate

Abundance estimated as N = (M × C)/R, where M is the number marked initially, C is the number caught in a second sample and R is the number of marked individuals recaptured.

Quadrat sampling

Method using randomly placed frames to estimate abundance, density or percentage cover of organisms. Random placement avoids bias, and percentage cover suits sessile species such as algae and corals.

Correlation and causation

A correlation shows two variables vary together but does not prove one causes the other. Confounding variables and sampling bias must be excluded before a causal claim is justified.