Data from CoFish: co-designing citizen science between fishers and scientists to monitor the phosphorus distribution across two Lake Geneva basins

Background Eutrophication, followed by re-oligotrophication during lake
restoration, in many peri-alpine lakes has caused important changes to the
functioning and biodiversity of freshwater ecosystems. In Lake Geneva,
total phosphorus (TP) concentration has been reduced since the eutrophic
years, and is now close to the upper value of the target range of 10-15
µg/L. For over 60 years the lake has been monitored at SHL2, the central
and deepest point in the Eastern basin, complemented by data from GE3 in
the Western basin. Selection of these reference points was based on a
lake-wide analysis of TP in the 1950s. Fishers have for some time
expressed concerns that further reductions in TP could damage the
sustainability of their livelihoods. They have called for a re-evaluation
of the historical sampling points to determine whether SHL2 and GE3 can
still be considered representative in terms of nutrient concentration of
the lake. Results Here, we present the scientific and societal impacts of
CoFish, a co-designed research project between scientists and fishers of
Lake Geneva. To reassess the spatial variability of TP we applied a
low-cost method to collect integrated water samples across the lake, using
stoppered hosepipes as a collection instrument. In this article, we
present four key messages: i)    
There is spatial variation in phosphorous levels, and in most cases the
two points fall within an acceptable range of variability;
ii)    The concentrations of phosphorus are
generally low across the lake in ranges that could have an impact for
plankton development. iii) Citizen science can complement long-term
monitoring, allowing for instance for better spatial coverage of
environmental data; iv) The co-design process resulted in community
empowerment, a willingness to further collaborate. Conclusions The
management implications of this work are that using a single reference
station as being representative of the lake as a whole is not
straightforward. In the discussion, we advocate for a re-evaluation of the
TP targets, given radical changes in the lake`s physical structure and
food web. We further highlight the important role of engaging fishers in
citizen science, which resulted in bridging existing gaps between lake
management, science, and fisheries, providing a broader basis for lake
conservation.