Salinity as a Determinant Structuring Microbial Communities in Coastal Lakes

Abstract

The response of bacterioplankton structure to salinity level in coastal lakes (n = 9) along the southern Baltic Sea coastline was studied. In terms of mean salinity levels (0.2–5.2 PSU), the lakes represented freshwater, transitional, and brackish types. Results showed that salinity determines the spatial and seasonal distribution patterns of microorganisms in costal lakes. Increased salinity contributed to a significant decline in total bacterial numbers (TBN). The TBN was lowest in brackish lakes in autumn (4 × 106 cells/mL) and highest in freshwater lakes in summer (7.11 × 106 cells/mL). The groups of Proteobacteria are appropriate bioindicators in any classifications of coastal ecosystems, particularly at low-haline stress. Alpha- and Gamma- subclasses of Proteobacteria are identifiers for brackish habitats, while Betaproteobacteria, due to their intolerance to haline stress, prefer freshwater habitats. Counts of euryhaline Actinobacteria, the dominant group of bacterioplankton (31.8%), decreased significantly with increased salinity. Actinobacteria and Deltaproteobacteria were identifiers of transitional lakes. Cytophaga-Flavobacteria showed affinity with freshwater ecosystems, but this relation was not statistically significant (p > 0.05). The bacteria groups correlated with other physico-chemical parameters of water, such as oxygenation (Actinobacteria) or organic carbon (Betaproteobacteria, Deltaproteobacteria). The impact of hydrological connectivity and salt-water interference on the microbiota structure and biogeochemistry of coastal waters should be considered in the assessment of the ecological status of coastal lakes.

Response of Macrophyte Diversity in Coastal Lakes to Watershed Land Use and Salinity Gradient

“…The effects of salinity on the ecosystem health of coastal lakes are even better known [ 60 ] than the impact of lake watersheds. It is commonly reported that salinity leads to a decline in biodiversity and disrupts macrophyte structure in coastal ecosystems, e.g., [ 29 , 61 , 62 ]. This may help to explain the fact that, in coastal lakes with low salinities < 7 PSU, the average values of diversity indices H’ and evenness J’ are lower than the values of the same macrophyte diversity indices for the trophic (harmonic) lakes that are typical of most lakes in Poland [ 28 ].…”

“…Noteworthy are the sandy soils in the watershed, which are typical of dune landscapes with a lack of hydrographic network (arheic area). The infiltrative nature of the initial soils in the south-eastern part of the watershed area, which are susceptible to wind erosion [ 6 , 10 ], causes the water of Ptasi Raj to have a relatively high salinity–the highest among the lakes studied in the southern Baltic coastal zone [ 62 ].…”

Microbial ecology and site characteristics underlie differences in salinity-methane relationships in coastal wetlands

“…At the chemical level, salinity also affects the solubility of dissolved organic carbon and other compounds, as well as the sorption of inorganic ions (25–27). While oligohaline salinities are high enough to elicit responses in microbial communities (28, 29), work done across broader salinity gradients including mesohaline (5-18 ppt) and polyhaline (18-30 ppt) areas suggests that the effects of salinization will likely be dependent on the magnitude of salinization (23, 30, 31). This may in turn affect the relationship between salinity and methane emissions, which has been shown to be non-linear (23).…”

Analysis of the Effect of Modified Biochar on Saline–Alkali Soil Remediation and Crop Growth

“…Soil salinization also reduces the permeability of the soil, affecting the water absorption activities of plant and crop roots and causing physiological dehydration and other problems [12,13]. Soil salinization also has a negative impact on soil microbial communities, which worsens soil biological characteristics and hinders the growth and development of plants and crops [14][15][16]. The action of biochar on plants can accelerate their growth, thus increasing the yield of crops.…”