Occurrence and nutrient retention of aquatic macrophytes in roadside streams in the Mount Cameroon region

Abstract

Roadside streams in the Mount Cameroon region are predisposed to nutrient enrichment from different anthropogenic activities carried out around catchment areas. The composition and diversity of aquatic macrophytes in three roadside streams in the MCR, the biomass, and nutrient accumulation of the most abundant aquatic macrophytes in one of the streams were assessed in order to better understand and quantify the benefits accruing from these macrophytes. Vegetation sampling was carried out along the transects at 50 m intervals, within which plots were laid. Quadrats of 1m by 1m were sub-sampled within each plot and all plants were identified and enumerated. Water, sediment, and plant samples were collected and analysed for nutrients using standard procedures (nitrogen and phosphorus). The results show that the aquatic vegetation of the roadside streams is limited to emergent (> 98%) and floating-leaved life forms. A total of 47 aquatic macrophytes from 18 plant families were identified from the 3 studied wetlands in the Mount Cameroon region. Plant taxa with many representative species included Poaceae (8 species), Araceae (6), Acanthaceae (5), and Asteraceae (4). A high Shannon-Wiener diversity was recorded across study sites (H ≥ 2.9) with the highest in Ombe and the least in Bota. P. purpureum showed significantly higher biomass (p < 0.05) compared to the other macrophytes. It had the highest fresh weight and dry weights (FW: 12.8±1.45 kg/m2 and DW: 0.81± 0.11kg/m2) relative to C. benghalensis and I. aquatica.TN content was highest in C. benghalensis (12.92 ± 0.67 g/kg). P. pupureum and I. aquatica didn’t differ significantly in their nitrogen content (P≤ 0.05) while all three species contained high phosphorus concentrations in their above-ground tissues. TP storage was in the order C. benghalensis >P. purpureum>I. aquatica. This suggests that aquatic macrophytes play vital roles in retaining phosphorus and nitrogen hence affecting water quality and nutrient dynamics of these streams. These nutrient-rich plants can be removed from the aquatic system by harvesting and used as fodder to prevent nutrient release into the water column through decomposition after plant dieback.