Seawater

This means that every kilogram (roughly one liter by volume) of seawater has approximately 35 grams (1.2 oz) of dissolved salts (predominantly sodium (Na+) and chloride (Cl−) ions).

Where mixing occurs with freshwater runoff from river mouths, near melting glaciers or vast amounts of precipitation (e.g. monsoon), seawater can be substantially less saline.

The salinity in isolated bodies of water can be considerably greater still – about ten times higher in the case of the Dead Sea.

[17] Small amounts of other substances are found, including amino acids at concentrations of up to 2 micrograms of nitrogen atoms per liter,[18] which are thought to have played a key role in the origin of life.

These differences were attributed to the occurrence of bacteria in aggregates, selective effects of the culture media, and the presence of inactive cells.

Mitchell Sogin from the Marine Biological Laboratory feels that "the number of different kinds of bacteria in the oceans could eclipse five to 10 million.

Cyanobacteria played an important role in the evolution of ocean processes, enabling the development of stromatolites and oxygen in the atmosphere.

One anaerobic species, Thiomargarita namibiensis, plays an important part in the breakdown of hydrogen sulfide eruptions from diatomaceous sediments off the Namibian coast, and generated by high rates of phytoplankton growth in the Benguela Current upwelling zone, eventually falling to the seafloor.

Bacteria-like Archaea surprised marine microbiologists by their survival and thriving in extreme environments, such as the hydrothermal vents on the ocean floor.

[23] In 2000 sediments from the ocean floor revealed a species of Archaea that breaks down methane, an important greenhouse gas and a major contributor to atmospheric warming.

The protist dinoflagellates may at certain times undergo population explosions called blooms or red tides, often after human-caused pollution.

The process may produce metabolites known as biotoxins, which move along the ocean food chain, tainting higher-order animal consumers.

[25] The ocean has a long history of human waste disposal on the assumption that its vast size makes it capable of absorbing and diluting all noxious material.

[26] While this may be true on a small scale, the large amounts of sewage routinely dumped has damaged many coastal ecosystems, and rendered them life-threatening.

[29] The water in the sea was thought to come from the Earth's volcanoes, starting 4 billion years ago, released by degassing from molten rock.

[15]: 133 Climate change, rising levels of carbon dioxide in Earth's atmosphere, excess nutrients, and pollution in many forms are altering global oceanic geochemistry.

Concentrations are projected to grow in coming decades, with negative impacts on ocean biota and other marine resources.

Seawater is a tool for countries to efficiently participate in international commercial trade and transportation, but each ship exhausts emissions that can harm marine life, air quality of coastal areas.

In areas with higher regions of sand dunes, such as Israel, the use of seawater for irrigation of plants would eliminate substantial costs associated with fresh water when it is not easily accessible.

[36] Large-scale desalination of seawater is another factor that would contribute to the success of agriculture farming in dry, desert environments.

Eventually the blood's sodium concentration rises to toxic levels, removing water from cells and interfering with nerve conduction, ultimately producing fatal seizure and cardiac arrhythmia.

Larger sailing warships with large crews, such as Nelson's HMS Victory, were fitted with distilling apparatus in their galleys.

Proponents include world-renowned chefs Ferran Adrià and Quique Dacosta, whose home country of Spain has six different companies sourcing filtered seawater for culinary use.

A restaurant run by Joaquín Baeza sources as much as 60,000 litres a month from supplier Mediterranea[47] Animals such as fish, whales, sea turtles, and seabirds, such as penguins and albatrosses, have adapted to living in a high-saline habitat.

For example, sea turtles and saltwater crocodiles remove excess salt from their bodies through their tear ducts.

Organisms of all sizes play a significant role in the balance of marine ecosystems with both the largest and smallest inhabitants contributing equally to recycling nutrients in seawater.

However, a more in depth study is required to understand the benefits of whale feces as a fertilizer and to provide further insight in iron recycling in the Southern Ocean.

Lithium mining from the seafloor at mass quantities could provide a substantial amount of renewable metals to promote more environmentally friendly practices in society to reduce humans' carbon footprint.

[55] Similarly to fish harvesting from the seafloor, the extraction of minerals in large amounts, too quickly, without proper protocols, can result in a disruption of the underwater ecosystems.

[55] Contrarily, this would have the opposite effect and prevent mineral extractions from being a long-term sustainable practice, and would result in a shortage of required metals.