Recovery of the benthic bacterial community in coastal abandoned saltern requires over 35 years: A comparative case study in the Yellow Sea

New insights in bacterial and eukaryotic diversity of microbial mats inhabiting exploited and abandoned salterns at the Ré Island (France)

“…This phyla composition was comparable to that of coastal microbial mats where Cyanobacteria, Proteobacteria and Bacteroidetes are dominant (Cardoso et al 2019) as well as in most hypersaline microbial mats (Pal et al 2020). Bacteroidetes and Proteobacteria, described as dominant phyla in the water and sediment of other salterns (Boujelben et al 2012;Lee et al 2020), are known to play important roles in carbon and nitrogen cycles (Bernhard, Marshall and Yiannos 2012;Wong et al 2015). Only Gammaproteobacteria showed significant differences between the studied sites: they were significantly more abundant in the exploited site than in the abandoned site (Student t-test, p<0.05).…”

“…Such observation suggested that the abandonment period (15 years) was not long enough for erasing the effect of saltern exploitation to reach the bacterial composition observed in coastal sediments, probably because the salinity in both abandoned and exploited sites exceeds regularly the seawater salinity (> 35 psu). To the best of our knowledge, only two studies have reported the reorganization of microbial communities after the abandonment of salterns exploitation (Bernhard, Marshall and Yiannos 2012;Lee et al 2020). These studies concluded that the physical-chemical parameters were similar to that observed at the coast only one year after the natural collapse of embankments, but the bacterial composition remained different for more than 30 years (Bernhard, Marshall and Yiannos 2012;Lee et al 2020).…”

“…To the best of our knowledge, only two studies have reported the reorganization of microbial communities after the abandonment of salterns exploitation (Bernhard, Marshall and Yiannos 2012;Lee et al 2020). These studies concluded that the physical-chemical parameters were similar to that observed at the coast only one year after the natural collapse of embankments, but the bacterial composition remained different for more than 30 years (Bernhard, Marshall and Yiannos 2012;Lee et al 2020). It is important to mention that in our study the salterns were still intact maintaining the salinity gradient, which drives bacterial community structure.…”

“…6). Interestingly, ASVs related to Loktanella (Alphaproteobacteria) and Desulfobacterales, which are usually found in abandoned salterns and tidal flats (Lee et al 2020), were identified among the bacterial biomarkers (Fig. 6A).…”

“…It has been demonstrated that the salinity fluctuations during salt production disturb the natural habitats (Tran et al 2019), influencing the development and the structure of the microbial mats that also depend on the seasonal variations (Boujelben et al 2012;Cardoso et al 2019). Because only few studies have investigated abandoned salterns (Cvitković et al 2011;Lee et al 2020), the information on how the ecosystem is affected by the modifications of human practices is still scarce. The comparison of the diversity within microbial mats subjected to large saline variations (exploited saltern) with that of microbial mats inhabiting ponds where the saline variations are limited (abandoned saltern) within the same hydrological system will allow to describe the modifications of microbial communities in response to a drastic change on the human practices, which are affecting the salinity fluctuations.…”