Marine biogeochemical cyclesMarine biogeochemical cycles are biogeochemical cycles that occur within marine environments, that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries. These biogeochemical cycles are the pathways chemical substances and elements move through within the marine environment. In addition, substances and elements can be imported into or exported from the marine environment. These imports and exports can occur as exchanges with the atmosphere above, the ocean floor below, or as runoff from the land.
OceanThe ocean (also known as the sea or the world ocean) is a body of salt water that covers approximately 70.8% of the Earth and contains 97% of Earth's water. The term ocean also refers to any of the large bodies of water into which the world ocean is conventionally divided. Distinct names are used to identify five different areas of the ocean: Pacific (the largest), Atlantic, Indian, Southern, and Arctic (the smallest). Seawater covers approximately of the planet.
OxygenOxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as well as with other compounds. Oxygen is Earth's most abundant element, and after hydrogen and helium, it is the third-most abundant element in the universe. At standard temperature and pressure, two atoms of the element bind to form dioxygen, a colorless and odorless diatomic gas with the formula O2.
Effects of climate change on oceansThere are many effects of climate change on oceans. One of the main ones is an increase inocean temperatures. More frequent marine heatwaves are linked to this. The rising temperature contributes to a rise in sea levels. Other effects include ocean acidification, sea ice decline, increased ocean stratification and reductions in oxygen levels. Changes to ocean currents including a weakening of the Atlantic meridional overturning circulation are another important effect. All these changes have knock-on effects which disturb marine ecosystems.
Biogeochemical cycleA biogeochemical cycle, or more generally a cycle of matter, is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cycle, the nitrogen cycle and the water cycle. In each cycle, the chemical element or molecule is transformed and cycled by living organisms and through various geological forms and reservoirs, including the atmosphere, the soil and the oceans.
Primary productionIn ecology, primary production is the synthesis of organic compounds from atmospheric or aqueous carbon dioxide. It principally occurs through the process of photosynthesis, which uses light as its source of energy, but it also occurs through chemosynthesis, which uses the oxidation or reduction of inorganic chemical compounds as its source of energy. Almost all life on Earth relies directly or indirectly on primary production. The organisms responsible for primary production are known as primary producers or autotrophs, and form the base of the food chain.
Ocean fertilizationOcean fertilization or ocean nourishment is a type of technology for carbon dioxide removal from the ocean based on the purposeful introduction of plant nutrients to the upper ocean to increase marine food production and to remove carbon dioxide from the atmosphere. Ocean nutrient fertilization, for example iron fertilization, could stimulate photosynthesis in phytoplankton. The phytoplankton would convert the ocean's dissolved carbon dioxide into carbohydrate, some of which would sink into the deeper ocean before oxidizing.
Oxygen minimum zoneThe oxygen minimum zone (OMZ), sometimes referred to as the shadow zone, is the zone in which oxygen saturation in seawater in the ocean is at its lowest. This zone occurs at depths of about , depending on local circumstances. OMZs are found worldwide, typically along the western coast of continents, in areas where an interplay of physical and biological processes concurrently lower the oxygen concentration (biological processes) and restrict the water from mixing with surrounding waters (physical processes), creating a "pool" of water where oxygen concentrations fall from the normal range of 4–6 mg/L to below 2 mg/L.
Air pollutionAir pollution is the contamination of air due to the presence of substances in the atmosphere that are harmful to the health of humans and other living beings, or cause damage to the climate or to materials. It is also the contamination of indoor or outdoor surrounding either by chemical activities, physical or biological agents that alters the natural features of the atmosphere. There are many different types of air pollutants, such as gases (including ammonia, carbon monoxide, sulfur dioxide, nitrous oxides, methane and chlorofluorocarbons), particulates (both organic and inorganic), and biological molecules.
Pacific decadal oscillationThe Pacific decadal oscillation (PDO) is a robust, recurring pattern of ocean-atmosphere climate variability centered over the mid-latitude Pacific basin. The PDO is detected as warm or cool surface waters in the Pacific Ocean, north of 20°N. Over the past century, the amplitude of this climate pattern has varied irregularly at interannual-to-interdecadal time scales (meaning time periods of a few years to as much as time periods of multiple decades).
