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1 October 2011 Trophic Structure and Biomass Distribution of Macrobenthos on Sheltered and Semi-Exposed Rocky Shores of Tsitsikamma Marine Protected Area
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Abstract

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 (P < 0.05) higher at semi-exposed shores, while grazer biomass was greater at sheltered sites: a negative relationship (P < 0.01) and a moderate to weak correlation (r > 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 (Octomeris angulosa and Perna perna) against that of the dominant grazer (Scutellastra cochlear). On sheltered shores the biomass of trophic groups varied significantly (P < 0.05) across the intertidal gradient studied, with values of grazers and algae decreasing with increased aerial exposure. Similar, but less substantial (P > 0.05) variations were recorded at semi-exposed sites, where the median shell length of the brown mussel P. perna decreased upshore (P < 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.

Nicholas Hanekom "Trophic Structure and Biomass Distribution of Macrobenthos on Sheltered and Semi-Exposed Rocky Shores of Tsitsikamma Marine Protected Area," African Zoology 46(2), 224-238, (1 October 2011). https://doi.org/10.3377/004.046.0203
Received: 28 September 2009; Accepted: 1 February 2011; Published: 1 October 2011
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