QCAA Marine Science EA key terms

The large-scale, slow movement of ocean water driven by differences in temperature (thermo) and salinity (haline), which together control density. It transports heat, nutrients, and dissolved gases around the globe.

The apparent deflection of moving objects, including ocean currents and winds, caused by Earth's rotation. In the Southern Hemisphere, deflection is to the left; in the Northern Hemisphere, to the right.

The upward movement of cold, nutrient-rich water from depth to the surface, often caused by winds pushing surface water offshore. It supports high productivity and important fisheries.

Mass per unit volume of seawater, influenced mainly by temperature and salinity. Cold, salty water is denser and tends to sink, while warm, fresh water is less dense and tends to float.

The total amount of dissolved salts in seawater, usually expressed in parts per thousand (ppt) or practical salinity units. It affects density, osmotic balance in organisms, and water circulation.

The layering of a water body into distinct layers of different density, often with warmer, lighter water above colder, denser water. This layering can limit mixing and nutrient exchange.

The regular rise and fall of sea level caused mainly by the gravitational pull of the Moon and Sun on Earth's oceans. Tides influence coastal currents, habitats, and the timing of biological activity.

The movement of energy through water as waves, generated by wind or other disturbances. It shapes coastlines, affects sediment transport, and influences the distribution of coastal organisms.

The coastal area between the high-tide and low-tide marks that is periodically exposed to air and submerged by water. Organisms here must tolerate changing temperature, salinity, and desiccation.

The physiological strain experienced by organisms when exposed to air and at risk of drying out. It is a major challenge for intertidal organisms during low tide.

The movement of sand, mud, and other particles by water currents, waves, or wind. It affects coastal erosion, deposition, habitat structure, and water clarity.

The cloudiness or haziness of water caused by suspended particles such as sediment or algae. High turbidity reduces light penetration and can harm photosynthetic organisms and visual predators.

A group of individuals of the same species living in a defined area at the same time. Populations are the basic unit for studying abundance, distribution, and change over time.

All the different populations of organisms living and interacting in a particular area. Community structure is shaped by competition, predation, and environmental conditions.

A network of interconnected food chains showing the feeding relationships among organisms in an ecosystem. It illustrates how energy and matter flow from producers to consumers and decomposers.

A position in a food chain or web defined by the number of feeding steps from the primary producer. Examples include primary producers, primary consumers (herbivores), and secondary consumers (carnivores).

The rate at which organisms produce organic matter, often measured as carbon fixed per unit area per unit time. Primary productivity by phytoplankton and algae forms the base of most marine food webs.

The process by which plants, algae, and some bacteria use sunlight, carbon dioxide, and water to produce organic matter and oxygen. It is the foundation of most marine food webs.

The total mass of living organisms in a given area or volume, often expressed as grams of carbon or dry weight per square metre. It provides a measure of the amount of biological material present.

A species whose impact on its community is disproportionately large relative to its abundance. Its removal can cause significant changes in community structure and ecosystem function.

The maximum number of individuals of a species that an environment can support sustainably over time, given available resources. It can change with environmental conditions and resource availability.

The process by which new individuals join a population, often referring to the survival of larvae or juveniles to a size or age at which they can be counted or harvested.

The capacity of an ecosystem to absorb disturbance and reorganise while retaining its essential structure and function. Resilient ecosystems can recover from stresses such as pollution or overfishing.

The enrichment of water with nutrients, especially nitrogen and phosphorus, often from runoff. It can lead to algal blooms, oxygen depletion, and changes in community structure.

A condition of low dissolved oxygen in water that can stress or kill marine organisms. It often results from nutrient pollution and the decay of algal blooms.

The largest catch that can be taken from a fish stock over an indefinite period without causing population decline. It is a key concept in fisheries management, though difficult to estimate reliably.

Harvesting fish at a rate that exceeds the stock's ability to replenish itself, leading to population decline. It can disrupt food webs and reduce ecosystem resilience.

The unintended capture of non-target species, such as dolphins, turtles, or juvenile fish, during fishing operations. Bycatch can cause significant ecological and economic impacts.

Using marine resources in a way that meets current needs without compromising the ability of future generations to meet their own needs. It balances ecological, economic, and social considerations.

A defined region of ocean or coast managed to protect marine habitats, species, or cultural values. MPAs can restrict activities such as fishing, mining, or tourism to conserve biodiversity.

A structured approach to managing natural resources that involves monitoring outcomes and adjusting strategies as new information emerges. It treats management as an ongoing experiment to reduce uncertainty.

A testable, falsifiable statement that proposes a possible explanation for an observation. In marine science, hypotheses guide data collection and are evaluated against evidence.

The planned structure of a scientific investigation, including the selection of treatments, controls, replication, and sampling methods. Good design aims to reduce bias and allow valid conclusions.

The extent to which repeated measurements or investigations produce consistent results. High reliability suggests that findings are not due to random error or chance.

The extent to which a measurement or investigation accurately measures what it is intended to measure. Validity depends on appropriate design, controls, and interpretation of data.

The physiological challenge faced by organisms when the concentration of dissolved salts in their environment differs from that in their body fluids, requiring them to regulate water and salt balance.