Recent (2008–2012) seaweed flora of Hainan Island, South China Sea

<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

Macroalgal assemblage changes on coral reefs along a natural gradient from fish farms in southern Hainan Island

<p>Degradation processes on coral reefs are associated with changes in macroalgal assemblages. In this study, a floristic study of the macrophyte species on coral reefs along a pollution gradient at 3 transects in southern Hainan Island, China, was conducted in April 2014. A total of 73 benthic macroalgal taxa were collected, of which 58% were reds, 23% browns and 19% greens. Along with the distance away from the outlet of fish farms, macroalgal species richness increased significantly from 40 species to 71 species. However, macroalgal biomass decreased from 1.58 kg m⁻² to 1.1 kg m⁻². Brown blooms of <i>Chnoospora implexa</i>, <i>Padina australis, Sargassum polycystum</i> and <i>S. sanyaense</i> changed to green blooms of <i>Ulva lactuca</i> and <i>Caulerpa racemosa</i> from moderately polluted sites to severely polluted sites close to the outlet. This study supports the results that severe pollution can lead not only to a significant decline of macroalgal species richness and changes in macroalgal assemblages, but also to the occurrence of green blooms. This study will hopefully provide more accurate cases to link nutrient pollution to changes in benthic organisms on coral reefs.</p