<div><p></p><p>During the period from 2008 to 2012, algal samplings were conducted off Hainan Island (China) at seven localities. A total of 252 benthic macroalgal taxa were collected where 53% were reds, 31% greens and 16% browns. The largest numbers of species belonged to the families Rhodomelaceae, Ceramiaceae, Corallinaceae (Rhodophyta), Cladophoraceae, Ulvaceae, Caulerpaceae (Chlorophyta), Sargassaceae and Dictyotaceae (Heterokontophyta). The analysis of the floristic diversity and composition during 2008–2012 revealed similarity to that of other large islands in the tropical zone of the Indo-Pacific where coral reefs are the main ecosystem. As was shown by comparative analysis of algal species composition and form diversity between the periods of 1990/1992 and 2008–2012, maximum similarity boundary values between the floras amounted to 66% (Rh), 65% (Ch) and 55% (Phaeophyceae, Ph). These decadal changes resulted in the loss of long-living volumetric forms of macrophytic algae with an increase in the number of fine filamentous algal forms, with tubular and blade-like thalli, as seawater pollution and probably natural catastrophes occurred during the period between the 1990s and 2000s.</p></div
