Seasonal changes of macroalgal composition, biomass and assemblage diversity in the rocky intertidals of Zhifu Tombolo, China

Abstract

In all seasons, red algae formed the component with the highest species number and biomass, brown algae ranked the second and green algae the last. The seasonal changes in total algal biomass in the assemblage were sequenced as following: August (228.64 g/m²) > October (161.63 g/m²) > June (207.29 g/m²) > April (117.19 g/m²) > December (77.96 g/m²) > February (41.29 g/m²). An outstanding seasonal variation of both macroalgal composition and dominance in the intertidal assemblage was observed during the survey. Species richness and diversity in the intertidal assemblage showed a seasonal rhythm in which the highest levels in Margalef’s species richness index (<i>R</i>) and Shannon-Wiener’s species diversity index (<i>H’</i>) were found in April (<i>R </i> 6.23) and June (<i>H’</i> 3.08) respectively. In terms of the function of dominant species based on biomass the surveyed assemblages could be grouped into three macroalgal assemblage aspects: “<i>Geldium</i> - dominating spring-association”, “<i>Sargassum</i> - dominating summer-association” and “<i>Ulva</i> - dominating autumn- winter - association”.