Municipal wastewater can result in a dramatic decline in freshwater fishes: a lesson from a developing country

Abstract

Impacts of ineffective wastewater management on the biodiversity of receiving waters in developing countries are poorly documented. Using a before-after-control-impact methodology, we measured the effects of untreated wastewater release on the fish community in the Barnoi River, Bangladesh. In 2006, prior to untreated wastewater discharge, fish abundance, species richness and water quality were similar across sampling sites. In 2016, after 8 years of wastewater release to the downstream reach, fish abundance and species richness were reduced by >47% and >35% respectively at downstream sites compared to unaffected upstream sites and >51% and >41% lower respectively compared to the pre-wastewater discharge period. The wastewater impact was particularly severe during months of low discharge (October–December). Water transparency, dissolved oxygen and pH were lower (P < 0.001) at impacted downstream sites compared to upstream sites. Nineteen species (41.3% of all species we recorded) are threatened in Bangladesh and the abundance of these species, except one, decreased significantly (P < 0.05) at the impacted sites. We recommend improved wastewater management by applying primary treatment facilities and incorporating reedbed filtration as a mean of biological treatment, into the canals carrying wastewaters. The success of such measures should be tested with fish species that were most responsive to wastewater, using the indicator species concept.

Assessment of water quality and its effect on prawn abundance in three tributaries of Shiwalik rivers: Chenab and Ravi of Jammu, India—a case study

“…Also, the fast flowing nature of streams lowers the efficiency of catching the prawn species. A similar reason was reported by Galib et al (2018) in the case of reduced fish abundance during this season. Akhi et al (2020) reported that fast flow of water reduces the availability of food making the conditions unfavorable.…”

Strong impacts of signal crayfish invasion on upland stream fish and invertebrate communities

“…We employed a BACI approach in S 1 and S 3 (Boys et al., 2012; Galib et al., 2018; Galib, et al., 2018) and a control–impact approach in S 2 , where sampling years represent time before–after and status of signal crayfish (present or absent) in streams represents control (i.e. uninvaded streams) and impact (i.e.…”

“…In S 1 , as both fish and environmental data were available, the multivariate BIOENV procedure, based on Euclidean distances (Clarke & Ainsworth, 1993), was employed to find out the best subset of environmental variables with maximum (rank) correlation (Pearson's) with community dissimilarities (e.g. Boys et al., 2012; Galib, et al., 2018). Along with all the environmental variables (depth, flow velocity, flow typology, DO, temperature, pH, substrate, canopy cover), we also considered density of signal crayfish in the BIOENV model to determine the role of signal crayfish for changes in fish community over time.…”

Bayesian inference of physicochemical quality elements of tropical lagoon Nokoué (Benin)

“…The negative impact of forests on transparency highlighted here is hardly compatible with the findings from several publications that instead support a positive effect of forests on water transparency (Kasangaki, Chapman, & Balirwa, 2008 ;Roozen et al, 2003) or report that they reduce turbidity (Brauman, Daily, Duarte, & Mooney, 2007 ;Cunha, Sabogal-Paz, & Dodds, 2016), and is difficult to interpret. The lower transparency values observed in lake villages (LV) with high visitation rates and direct discharge of domestic effluent are more consistent with the expected mechanical effects of these stressors (Galib et al, 2018). Mangroves not only reduce the total nutrient load (Wang, Cheng, Chen, & Kuo, 2021), but they also have the potential to absorb pollutants (Nguyen, Truong, & Pham, 2020) and should therefore lead to a decrease in BOD.…”