Nutrient loadings and deforestation decrease benthic macroinvertebrate diversity in an urbanised tropical stream system

Rice paddy irrigation seasonally impacts stream benthic macroinvertebrate diversity at the catchment level

“…In developing countries, urbanization is the most critical factor leading to decreased stream biodiversity in watershed ecosystems (Peralta et al 2019, 2020). The possible mechanism is that domestic nutrient loading from residential areas decreases dissolved oxygen in stream habitats via epilithic microbial respiration that is enhanced by cultural eutrophication (Peralta et al 2020). We also found a negative path from epilithic biomass, that is, Chl‐a, to benthic macroinvertebrate diversity, rejecting the possibility of a bottom‐up trophic cascading effect on stream biodiversity.…”

“…Forests can provide a variety of food sources for stream benthic macroinvertebrates, through the transportation of dissolved and particulate organic matter, increasing the diversity of feeding functional groups (Ishikawa et al 2016). In the watersheds of developing countries, riparian deforestation is considered to be a secondary critical factor, behind urbanization, in decreasing the EPT index, which is defined as the species richness or density of the disturbance‐sensitive insect orders, Ephemeroptera, Plecoptera, and Trichoptera, which have diverse feeding functions (Peralta et al 2020). Although we did not explicitly explore the feeding functions of benthic macroinvertebrate communities in this study, special attention should be paid to the impact on functional diversity in stream ecosystems whenever deforestation occurs, as proposed by researchers who performed studies in Southeast Asia and Madagascar (Benstead et al 2003, Benstead and Pringle 2004, Wilkinson et al 2018).…”

“…In the Yasu River ecosystem, nutrient levels are generally low (Table 1), and most streams show higher DO (mean AE standard deviation: 9.38 AE 0.62 mg/L) than the criterion for stream water quality (7.5 mg/L) designated by the Ministry of Environment in Japan. Thus, unlike streams in developing countries (Peralta et al 2020), it is less likely that eutrophication-induced oxygen depletion decreases benthic macroinvertebrate diversity in the Yasu River. An alternative explanation may be a decrease in the diversity of food sources for consumers under nutrient enrichment conditions.…”

“…In contrast, we found that residential activity had a limited indirect effect on benthic macroinvertebrate diversity during the nonirrigation period, through domestic nutrient loading and resultant increases in epilithic biomass. In developing countries, urbanization is the most critical factor leading to decreased stream biodiversity in watershed ecosystems (Peralta et al 2019(Peralta et al , 2020. The possible mechanism is that domestic nutrient loading from residential areas decreases dissolved oxygen in stream habitats via epilithic microbial respiration that is enhanced by cultural eutrophication (Peralta et al 2020).…”

Spatial Changes in Invertebrate Structures as a Factor of Strong Human Activity in the Bed and Catchment Area of a Small Urban Stream

“…Moreover, the presence of a pond in the middle of the stream can be associated with the high values of TDS and conductivity and release of a large amount of total nitrogen and phosphorus, mostly from anthropogenic activities, such as the use of baits in fishing ground or feeding of aquatic birds. Many authors claim that biogenic compounds found in excess in urban streams negatively affect the macroinvertebrate composition [37][38][39]. Moreover, a channelization and regulation of Bukówka bed caused the low values of current velocity that affected the higher densities of taxa typical for ponds, lakes and large river, what was observed in lower section of stream.…”