page_title: Shell growth in estuaries
section_title: Effect of salinity on calcification
hierarchical_section_title: Shell growth in estuaries / Effect of salinity on calcification
caption_attribution_description: English: Graphic breakdown of water salinity, defining freshwater, brackish water, saltwater, and brine water.
context_page_description: Shell growth in estuaries is an aspect of marine biology that has attracted a number of scientific research studies. Many groups of marine organisms produce calcified exoskeletons, commonly known as shells, hard calcium carbonate structures which the organisms rely on for various specialized structural and defensive purposes. The rate at which these shells form is greatly influenced by physical and chemical characteristics of the water in which these organisms live. Estuaries are dynamic habitats which expose their inhabitants to a wide array of rapidly changing physical conditions, exaggerating the differences in physical and chemical properties of the water.
  Estuaries have large variation in salinity, ranging from entirely fresh water upstream to fully marine water at the ocean boundary. Estuarine systems also experience daily, tidal and seasonal swings in temperature, which affect many of the chemical characteristics of the water and in turn affect the metabolic and calcifying processes of shell-producing organisms.
context_section_description: Salinity refers to the water's "saltiness". In oceanography and marine biology, it has been traditional to express salinity not as a percent, but as permille (parts per thousand) (‰), which is approximately grams of salt per kilogram of solution. Salinity varies even more widely than temperature in estuaries, ranging from zero to 35, often over relatively short distances. Even organisms in the same location experience broad swings in salinity with the tides, exposing them to very different water masses with chemical properties that provide varying levels of support for calcification processes. Even within a single estuary, an individual species can be exposed to differing shell deposition conditions, resulting in varied growth patterns due to changes in water chemistry and resultant calcification rates.
caption: Terms for water with different salinities
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