Marine Agar 2216 is a specialized culture medium designed for the isolation, enumeration, and maintenance of heterotrophic marine bacteria. Based on the classic ZoBell formulation, this medium replicates the mineral composition of seawater, providing an environment suitable for organisms that cannot grow on freshwater based media. The formulation contains a complex mixture of salts including sodium, magnesium, calcium, and potassium, along with trace elements such as strontium and boron that are naturally present in marine environments. These components maintain the osmotic balance required by marine microorganisms and prevent cellular stress when cultured outside seawater. Marine Agar 2216 supports growth of organisms such as Vibrio, Pseudoalteromonas, and Photobacterium commonly found in marine samples.