The Influence of Temporal Changes in Biomass of Brown Mussel Perna Perna on Abundance of Ambient Macrofauna on the Central Coast of Namibia

Abstract

Like terrestrial systems, marine ecosystems are constantly impacted upon by conditions arising from anthropogenically modified abiotic environments, climate change, as well as biotic agents. Marine mussels are widely regarded as ecosystem engineers. The Brown mussel species Perna perna is one such species. Mussels offer a wide range of advantages to intertidal communities through their structure and biomass, as they help increase the spatial heterogeneity in benthic processes, by serving as habitat or substrate for associated organisms and also as food for predators. However, the invasive species such as Mytillus galloprovincialis threaten the very existence of the indigenous brown mussel P. perna, due to the lower fecundity, recruitment and growth rate of latter. It is against this background that this study focused on the ecological implication of temporal changes in biomass of the P. perna on ambient macrofauna at Long Beach, on the Namibian central coast. The objectives of the study were: (a) To assess the temporal changes in biomass of P. perna; and (b) To investigate the influence of changes in biomass of P. perna on the abundance of its ambient macrofauna. Data analysis was performed in Microsoft excel as well as other statistical software such as Past and MaxStat. A t-Test for equal means was used to test all data at 0.05 significance level, except for data on the influence of change in biomass of P. perna on the abundance of ambient macrofauna, where a Multiple linear regression analysis used at 0.05 significance level. The statistical test results on biomass of P. perna yielded (t =2.3567; df = 2; P = 0.056542). There was no significant change in biomass of P. perna between autumn and winter. Similarly, statistical test results on condition index of P. perna yielded (t = 0.23896; df = 2; P = 0.81909). There was no significant change in condition of P. perna between autumn and winter. The change in biomass of P. perna did have a significant influence on the abundance of ambient macrofauna, as the statistical test yielded (t = 5.007; 2.845; 2.347 and P = 0.0002; 0.0138; 0.0354). The impact was negative, in that the abundance of ambient macrofauna decrease as a result of increase in biomass of P. perna.