n African Zoology - Trophic structure and biomass distribution of macrobenthos on sheltered and semi-exposed rocky shores of Tsitsikamma Marine Protected Area

Volume 46, Issue 2
  • ISSN : 1562-7020
  • E-ISSN: 2224-073X
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The trophic structure and biomass of macrobenthos on both wave-sheltered, rocky intertidal shores and semi-exposed ones at seven localities in the Tsitsikamma Marine Protected Area were compared. In the Cochlear zone and entire intertidal (Cochlear- and Balanoid zones combined) biomass values of invertebrates and filter-feeders were significantly ( < 0.05) higher at semi-exposed shores, while grazer biomass was greater at sheltered sites: a negative relationship ( < 0.01) and a moderate to weak correlation ( > 0.42) was also recorded between filter-feeder biomass and grazer biomass. This negative relationship reflected changes in standing biomass of the two dominant filter-feeders ( and ) against that of the dominant grazer (). On sheltered shores the biomass of trophic groups varied significantly ( < 0.05) across the intertidal gradient studied, with values of grazers and algae decreasing with increased aerial exposure. Similar, but less substantial ( > 0.05) variations were recorded at semi-exposed sites, where the median shell length of the brown mussel decreased upshore ( < 0.05). Multivariate analyses of square-root transformed biomass values separated most of the sheltered Cochlear zone stations from semi-exposed ones. This study supported the concept that the structure of low-shore communities is determined largely by differences in wave action.

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