Seawater desalination facilities continuously discharge hyper-saline brine into the coastal environment which often flows as a concentrated plume over the seafloor, hence possibly impacting benthic ...microorganisms. Yet, the effects of brine discharge from desalination plants on benthic bacteria, key players in biodegradation of organic material and nutrient recycling is unknown. In this study, we tested the chronic (years) effects of brine discharge from three large-scale desalination facilities on the abundance, metabolic activity and community composition of benthic bacteria. To this end, four sampling campaigns were carried at the outfall areas of the Ashkelon, Sorek and Hadera desalination facilities. The effects of the brine were compared to corresponding reference stations which were not influenced by the brine (i.e., water temperature and salinity). Our sampling data indicate that bacterial abundance and activity that includes bacterial growth efficiency were 1.3-2.6-fold higher at the outfall area than the reference station. Concomitant analysis pointed out that the bacterial community structure at the brine discharge area was also different than the reference station, yet varied between each desalination facility. Our results demonstrate that the impact of brine effluent from desalination facilities on benthic bacteria are site-specific and localized (<1.4 Km
) around the discharge point. Namely, that the effects on benthic bacteria are prominent at the brine mixing zone and change according to the discharge method used to disperse the brine as well as local stressors (e.g., eutrophication and elevated water temperature). Our results contribute new insights on the effects of desalination-brine to benthic microbes, while providing scientifically-based aspects on the ecological impacts of brine dispersion for decision makers.
1)Aquifers are recharged by surface water percolating through soil and rock and by connections with surface streams and rivers. Extreme rainfall can cause extensive flooding of surface waters and, ...eventually, of groundwaters. However, how the resultant changes in nutrients impact groundwater organisms and the structure of groundwater food webs is largely unknown.2)We monitored abiotic (nutrients, temperature and more) and biotic (all organismal groups except viruses) conditions in eight groundwater boreholes in two locations in a chalk aquifer over the course of 25 weeks (ten sampling occasions), following an extreme rainfall- and groundwater-flooding event in the UK.3)We show that groundwater flooding can cause substantial nutrient fertilisation of aquifers – nutrient concentrations (especially dissolved organic carbon) in the groundwater were highest when we started the sampling campaign, directly following the flood event, and then decreased over time while groundwater levels also declined back to their baseline.4)Bacteria in the open water (i.e. bacteria not associated with sediment) became more abundant as the water table and DOC concentrations decreased. Importantly their functional richness tracked the DOC patterns, illustrating that bacteria were responsible for respiring DOC. Microbial metabolic activity and bacterial respiration, measured using smart tracers, supported this finding; DOC and microbial respiration showed a positive correlation.5)The other biota (protists, micro- and macro-metazoans) showed different abundance patterns over time, but importantly, the entire sediment community, ranging from bacteria to macrofaunal species, showed a strong community size structure (mean size spectra slope: −1.12). Size spectra changed gradually through time towards steeper slopes, except in the very deep aquifer.6)Our approach allowed us to demonstrate that groundwater communities track extreme changes in their usually stable environment, highlighting that they potentially buffer environmental change, although we still do not know what the limits of this ‘service’ might be.
Display omitted
•Groundwater that had been flooded after an extreme rainfall event was sampled.•The flooding had resulted in high DOC levels that were tracked by bacteria.•Overall, small organisms increased in abundance while larger ones did not.•This altered the size distribution of the community towards steeper M-N slopes.•The deeper aquifer was less affected by the flooding.
Ciliate assemblages play a significant role in the microbial food web. The effects of environmental temperature on assemblage composition may be influenced by abiotic factors such as seasonality and ...disturbance, but the effects of temperature on ciliate assemblages found on different substrata have not been explored. Sandy bottoms and submerged rocks harbour dissimilar ciliate assemblages, and it might be expected that their ciliate assemblages will respond differently to temperature. We studied how alpha diversity, beta diversity and total biomass of ciliate protist assemblages found on sandy bottoms and submerged rocks differed in 13 geothermally heated streams in Iceland whose mean temperatures range from 5 to 20 °C. We recorded number of operational taxonomic units (OTUs) and measured the size of cells in ciliate assemblages from both substrata. Effects of temperature on natural ciliate assemblages were substratum dependent. On rock surfaces, both total ciliate biomass and alpha diversity declined with increasing temperature, and beta diversity increased with increasing temperature difference due to OTU nestedness (assemblages from warm streams being composed chiefly of subsets of the OTUs found in colder streams). In sandy substrata, however, ciliate assemblage composition was independent of temperature. Substratum‐specific responses may be due to differences in mechanical disturbance, nutrient availability or exposure to invertebrate grazers. Rock‐surface assemblages may be more exposed to the flow and retain less nutrient than those of sandy substratum; thus, they may be more strongly resource limited and more responsive to direct effects of temperature on metabolism. Alternatively, rock‐surface assemblages may be more exposed to grazing by invertebrates, which intensifies with temperature. Our study highlights the need to account for environmental context such as substratum type to fully understand the effect of temperature on microbial assemblages in streams. Future increases in global temperatures may affect fresh waters differently depending on their prevalent substratum. Those dominated by hard substrata may have their ciliate assemblages, and thus, food‐web structures and ecosystem functioning more strongly affected by warming relative to systems dominated by soft substrata.
Seawater desalination facilities continuously discharge hyper-saline brine into the coastal environment which often flows as a concentrated plume over the seafloor, hence possibly impacting benthic ...microorganisms. Yet, the effects of brine discharge from desalination plants on benthic bacteria, key players in biodegradation of organic material and nutrient recycling is unknown. In this study, we tested the chronic (years) effects of brine discharge from three large-scale desalination facilities on the abundance, metabolic activity and community composition of benthic bacteria. To this end, four sampling campaigns were carried at the outfall areas of the Ashkelon, Sorek and Hadera desalination facilities. The effects of the brine were compared to corresponding reference stations which were not influenced by the brine (i.e., water temperature and salinity). Our sampling data indicate that bacterial abundance and activity that includes bacterial growth efficiency were 1.3–2.6-fold higher at the outfall area than the reference station. Concomitant analysis pointed out that the bacterial community structure at the brine discharge area was also different than the reference station, yet varied between each desalination facility. Our results demonstrate that the impact of brine effluent from desalination facilities on benthic bacteria are site-specific and localized (<1.4 Km2) around the discharge point. Namely, that the effects on benthic bacteria are prominent at the brine mixing zone and change according to the discharge method used to disperse the brine as well as local stressors (e.g., eutrophication and elevated water temperature). Our results contribute new insights on the effects of desalination-brine to benthic microbes, while providing scientifically-based aspects on the ecological impacts of brine dispersion for decision makers.
Display omitted
•Abundance and activity of benthic bacteria are often affected by SWRO brine.•The impact of desalination brine on benthic bacteria is local and site-specific.•The diffuser method affects benthic microbial community composition.
Provider: - Institution: - Data provided by Europeana Collections- All metadata published by Europeana are available free of restriction under the Creative Commons CC0 1.0 Universal Public Domain ...Dedication. However, Europeana requests that you actively acknowledge and give attribution to all metadata sources including Europeana
PDF
