Abstract:

With an aim of describing the influence of coralline algae on other macroalgae and benthic invertebrates in the intertidal zone of the Nanji Islands, an investigation of such organism assemblages was conducted in the Nanji Archipelago Marine Nature Reserve between May 2012 and February 2013. Shannon-Wiener index and Pielou's evenness indices were calculated for macroalgae (including coralline algae), non-Corallinaceae macroalgae (excluding coralline algae) and benthic invertebrates. In addition, the functional diversity of the benthic community was estimated using Rao's Q. Our results are as follows: (1) A total of 52 species of macroalgae belonging to 3 phyla, 3 classes, 16 orders, 21 families and 41 genera were found; 5 species among them belonged to coralline algae; (2) The dominance of coralline algae has reached a high level in the intertidal zone of the Nanji Islands except in the high tidal zone where relatively few macroalgae exist. The biomass of coralline alga accounted for 68.9% of the total algae biomass. Shannon-Wiener indices of macroalgae diversity varied from 1.638-4.044, and non-Corallinaceae macroalgae varied from 1.495- 3.809, while benthic invertebrates’ varied from 5.2890-6.917. Pielou’s evenness of macroalgae communities varied from 0.819-0.971, and non-Corallinaceae macroalgae varied from 0.930-0.973; benthic invertebrates ranged from 0.967 to 0.988; (3) Regression analyses between dominance of coralline algae and Shannon-Wiener and Pielou's evenness indices of macroalgae communities suggested that coralline algae may be reducing the species diversity of macroalgae. The result of correlation analysis between dominance of coralline algae and Shannon-Wiener index, Pielou's evenness of benthic invertebrates showed no significant correlation. (4) The dominance of coralline algae and Rao's Q of benthic invertebrates in low tidal zone were both higher than those in middle tidal zone, but the correlation analysis showed no significant correlation between them. Based on our results, we concluded that: well-adapted coralline algae species may have reduced the species diversity of other macroalgae in these systems via interspecific competition; meanwhile, the benthic invertebrates, perhaps because of their higher dispersal abilities and more diverse life histories relative to macroalgae, were not affected in terms of species or functional diversity by coralline algae.

Key words: macroalgae, benthic invertebrates, species diversity, functional diversity