Assessment of Wetland Functional Responses to Cyperus papyrus Vegetation Biomass Harvesting Using Water Physicochemical Parameters and Macroinvertebrate Diversity in Saf Wetland, Kenya

Abstract

Papyrus (Cyperus papyrus) is the dominant plant species in the floodplain and littoral wetlands of Lake Victoria, where harvesting by riparian communities may affect plant growth and wetland ecosystem functioning. This study evaluated wetland functional responses to papyrus harvesting by integrating surface-water physicochemical parameters with macroinvertebrate diversity metrics. A controlled factorial field experiment compared plots harvested frequently (monthly), moderately (every 2.5 months), and infrequently (every 3.5 months) with adjacent unharvested controls. Water temperature (WT), dissolved oxygen (DO), and electrical conductivity (EC) were measuredin situ, while triplicate samples were collected for total nitrogen (TN), total phosphorus (TP), and macroinvertebrate analyses. Data were analysed using robust two-way ANOVA in R (v4.6.0) because of heterogeneity and unequal sample sizes. Significant spatial variation was detected for EC (F = 12082.6, p = 0.001), WT (F = 31.168, p = 0.001), TN (F = 241.79, p = 0.001), and TP (F = 11.687, p = 0.006). Harvesting treatment did not significantly affect DO, EC, WT, TN, or TP. However, macroinvertebrate diversity was significantly affected by treatment (F = 4.766, p = 0.035), plot (F = 12.184, p = 0.005), and their interaction (F = 12.726, p = 0.004). Saf Wetland therefore maintained relatively stable physicochemical conditions after harvesting, although harvesting intensity influenced nutrient dynamics and macroinvertebrate diversity. Regulated harvesting is important for sustaining wetland ecological integrity and ecosystem-service provision in Lake Victoria papyrus wetlands.