A total of 250 individuals from five coastal villages were rand omly selected and included fishers, farmers, beach management units (BMUs), fish processors and fish sellers. Adult women and men (older than 18 y.o.a) filled out a structured questionnaire which was used to screen their willingness, environmental interest and availability to perform monitoring activities. A total of 150 out of 250 individuals (30 in each village) were recruited for training. All participants underwent a stand ard field training and safety course, which included theoretical and hand s-on experience on nutrients and turbidity measurements. For the theoretical session, training was conducted for two days (16 h), while the practical session was conducted over 5 days (40 h). During the theoretical classes, participants were taught about water quality issues, sources of nutrients pollution in the lake and implications on the services provided by the lake. During the practical session, participants, in groups of 5, practised sampling and analysis techniques using water samples provided for training (Fore et al., 2001 ). The participants were given time to practice using stand ard nutrient and turbidity kits under the supervision of the trainer, who was able to provide feedback.
Citizen scientists used the FreshWater Watch method to gather nutrients, turbidity and contextual information about the conditions of the site (Thornhill et al., 2018 ). Nitrate and phosphate measurements were taken colorimetrically in closed tubes using a specified volume (Kyoritsu Chemical-Check Lab, Corp., Tokyo, Japan). Phosphate concentrations were detected using an enzymatic technique (4-amino-antipyrine with phosphatase enzyme), and nitrate concentration estimation was based on the Griess method (Berti et al., 1988 ; Nelson et al., 1954 ). Citizen scientists compared the colour of the sample tube to a stand ard reference colour chart, assigning colour brightness to specific concentration intervals (Scott & Frost, 2017 (link)). Turbidity measurements were taken using stand ard calibrated Secchi tubes with detection limits of 14 and 240 Nephelometric Turbidity Units (NTU) (Preisendorfer, 1986 ).
Samples were taken at each site every month and divided into samples to be measured by both citizen scientists and those to be taken to the laboratory by professional scientists. Citizen scientists recorded measurements directly onto the FreshWater Watch app (iOS and And roid) or using the paper version. Results in hardcopy were transcribed onto the smartphone app by fellow citizen scientists to upload to the global database (https://freshwaterwatch.thewaterhub.org/ ).
Datasets were quality-controlled for consistency, internal and contextual, by professional scientists from Tanzania Fisheries Research Institute (TAFIRI) and Earthwatch directly from the online database. Internal consistency between data fields (water colour and turbidity) and comparisons between sampling locations and sampling events were used to identify transcription and methodological errors. Citizen scientists were contacted to correct or repeat any identified errors. A subset (1%) of reagent tubes (nitrate and phosphate) from each lot were checked in the laboratory using stand ard solutions.
Citizen scientists used the FreshWater Watch method to gather nutrients, turbidity and contextual information about the conditions of the site (Thornhill et al., 2018 ). Nitrate and phosphate measurements were taken colorimetrically in closed tubes using a specified volume (Kyoritsu Chemical-Check Lab, Corp., Tokyo, Japan). Phosphate concentrations were detected using an enzymatic technique (4-amino-antipyrine with phosphatase enzyme), and nitrate concentration estimation was based on the Griess method (Berti et al., 1988 ; Nelson et al., 1954 ). Citizen scientists compared the colour of the sample tube to a stand ard reference colour chart, assigning colour brightness to specific concentration intervals (Scott & Frost, 2017 (link)). Turbidity measurements were taken using stand ard calibrated Secchi tubes with detection limits of 14 and 240 Nephelometric Turbidity Units (NTU) (Preisendorfer, 1986 ).
Samples were taken at each site every month and divided into samples to be measured by both citizen scientists and those to be taken to the laboratory by professional scientists. Citizen scientists recorded measurements directly onto the FreshWater Watch app (iOS and And roid) or using the paper version. Results in hardcopy were transcribed onto the smartphone app by fellow citizen scientists to upload to the global database (
Datasets were quality-controlled for consistency, internal and contextual, by professional scientists from Tanzania Fisheries Research Institute (TAFIRI) and Earthwatch directly from the online database. Internal consistency between data fields (water colour and turbidity) and comparisons between sampling locations and sampling events were used to identify transcription and methodological errors. Citizen scientists were contacted to correct or repeat any identified errors. A subset (1%) of reagent tubes (nitrate and phosphate) from each lot were checked in the laboratory using stand ard solutions.
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