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, very little research on Mussels has been done specifically on Namibian marine ecosystems. Moreover, 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; (b) To determine the temporal changes in condition of P. perna; and (c) To investigate the influence of changes in biomass of P. perna on the abundance of its ambient macrofauna. Samples were collected from 10cm x 10cm quadrats along a line transect on a 2m interval, over 50m across the intertidal zones. Data analysis was performed in Microsoft excel as well as Past and MaxStat. A t-Test for equal means was used to test all data, 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 at 0.05 significance level yielded (t =2.3567; df = 2; p = 0.056542), hence there was no significant change in biomass of P. perna between autumn and winter. Similarly, statistical test results on condition index of P. perna at 0.05 significance level yielded (t = 0.23896; df = 2; p = 0.81909), hence there was no significant change in condition of P. perna between autumn and winter. The change in biomass of P. perna significantly influenced the abundance of ambient macrofauna, as the statistical test at 0.05 significance level yielded (r = 0.807; 0.574; 0.479 and p = 0.0002; 0.0138; 0.0354).