Due to the southern bluefin tuna's high metabolic need, ions must be taken up relatively quickly to ensure sufficient concentrations for cellular function. Tuna are able to drink the seawater as they constantly swim in order to ensure sufficient ion concentrations. The seawater is specifically high in sodium and chloride ions which together make up approximately 80% of the ions in the water. The intake of sodium and chloride, along with lower relative concentrations of potassium and calcium ions in the seawater allow southern bluefin tuna to generate the action potentials required for muscle contraction.