Co-culture of fish with macroalgae and associated bacteria: A possible mitigation strategy for noxious red tides in enclosed coastal sea

Abstract

Algicidal bacteria play an important role in terminating red tides in coastal sea. On the surface of macroalgae such as Ulva sp. and Gelidium sp., algicidal microorganisms (mainly bacteria that kill red tide flagellates) were found to be attached numerously. Maximum number of algicidal bacteria were about 10⁵-10⁶/g (wet weight macroalgae). Algicidal bacteria were also much abundant in seawater collected at a seaweed bed in a coastal area of Osaka Bay. It is hence proposed that coculturing of fish with macroalgae is a new and gentle prevention strategy for the occurrences of noxious red tides in enclosed and small-scale embayments by virtue of continuous release of many algicidal bacteria from the surface of macroalgae.