Sentence:  The fauna of the modern floating <WSD>sargasso</WSD>-meadows is composed of highly specialized and unique species of pelagic animals. [...] The community of organisms which is found in these <WSD>sargasso</WSD>-flotillas is described in the report on the w:Challenger expedition 
Meaning of the word marked with <WSD> tags:  A brown alga, of the genus "Sargassum", that forms large, floating masses.