What happens when salinization meets eutrophication? A test using stream microcosms

Nutrient and salt pollution often co-occur in rivers and streams due to human activities (e.g., agriculture, urbanization). Thus, understanding the interactive effects of nutrients and salinity on freshwater ecosystems is critical for environmental management. We experimentally assessed the interact...

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Published in:The Science of the total environment 2024-02, Vol.912, p.168824-168824, Article 168824
Main Authors: Moyano Salcedo, Alvaro Javier, Prat, Narcís, Bertrans-Tubau, Lluís, Piñero-Fernandez, Martí, Cunillera-Montcusí, David, López-Doval, Julio C., Abril, Meritxell, Proia, Lorenzo, Cañedo-Argüelles, Miguel
Format: Article
Language:English
Subjects:
Biofilm
Chlorophyll A
Ecosystem
Eutrophication
Fresh Water
Freshwater ecosystems
Humans
Macroinvertebrates
Microcosms
Nitrogen
Nutrient pollution
Rivers - chemistry
Salt pollution
Sodium Chloride
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Summary:Nutrient and salt pollution often co-occur in rivers and streams due to human activities (e.g., agriculture, urbanization). Thus, understanding the interactive effects of nutrients and salinity on freshwater ecosystems is critical for environmental management. We experimentally assessed the interactive effects of nutrient and salt pollution on stream microcosms using biofilm and macroinvertebrates as model systems. Six treatments were performed in triplicate: control (C: N-NH4+ = 0.05; P- PO43− = 0.037; Cl- = 33.5 mg L−1), intermediate nutrient (IN: N-NH4+ = 0.4; P- PO43− = 0.271; Cl- = 33. 5 mg L−1), high nutrient (HN: N-NH4+ = 0.84; P- PO43− = 0.80; Cl- = 33.5 mg L−1), salt (S: N-NH4+ = 0.05; P- PO43− = 0.037; Cl- = 3000 mg L−1), salt with intermediate nutrient (SIN: N-NH4+ = 0.4; P- PO43− = 0.27; Cl- = 3000 mg L−1) and salt with high nutrient (SHN: N-NH4+ = 0.84; P- PO43− = 0.80; Cl- = 3000 mg L−1). After 14 days of exposure, biofilm chlorophyll-a increased across all treatments, with cyanobacteria replacing diatoms and green algae. Treatments with no added nutrients (C and S) had more P uptake capacity than the rest. The indicator species analysis showed 8 significant taxa, with Orthocladius (Orthocladius) gr. Wetterensis and Virganytarsus significantly associated with the salinity treatment. Overall, salt pollution led to a very strong decline in macroinvertebrate richness and diversity. However, salt toxicity seemed to be ameliorated by nutrient addition. Finally, both structural equation models and biotic-abiotic interaction networks showed that complex biological interactions could be modulating the response of the biological communities to our treatments. Thus, our study calls for species-level assessments of salt and nutrient effects on river ecosystems and advocates for better management of co-occurring pollutants. [Display omitted] •The study explored how nutrient and salt pollution interact in freshwater ecosystems using microcosms with biofilm and macroinvertebrates.•We found a negative effect of salinity on biofilm function and cyanobacteria.•We found a strong negative effect of salinity on macroinvertebrate richness and diversity.•Nutrient addition weakly ameliorated salt toxicity to aquatic macroinvertebrates.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2023.168824