The effect of water salinity on wood breakdown in semiarid Mediterranean streams

Saline streams occur naturally and they are distributed worldwide, particularly in arid and semiarid regions, but human activities have also increased their number in many parts of the world. Little attention has been paid to assess increasing salt effects on organic matter decomposition. The object...

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Bibliographic Details
Published in:The Science of the total environment 2016-01, Vol.541, p.491-501
Main Authors: Gómez, Rosa, Asencio, Antonia Dolores, Picón, José María, Del Campo, Rubén, Arce, María Isabel, del Mar Sánchez-Montoya, María, Suárez, María Luisa, Vidal-Abarca, María Rosario
Format: Article
Language:English
Subjects:
Abrasion
Abrasion resistance
Biomass
Breakdown
Chemical composition
Fungal biomass
Fungi
Mediterranean semiarid streams
Saline streams
Salinity
Salt crystals
Streams
Wood
Wood breakdown
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Summary:Saline streams occur naturally and they are distributed worldwide, particularly in arid and semiarid regions, but human activities have also increased their number in many parts of the world. Little attention has been paid to assess increasing salt effects on organic matter decomposition. The objectives of this study were to analyse wood breakdown rates and how salinity affects them in 14 streams that exemplify a natural salinity gradient. We also analysed the effect of this gradient on changes in wood chemical composition, fungal biomass and microbial activity. Our results showed low breakdown rates (0.0010–0.0032d−1), but they fell within the same range as those reported in freshwater streams when a similar woody substrate was used. However, salinity had a negative effect on the breakdown rates and fungal biomass along the salinity gradient, and led to noticeable changes in wood composition. Water salinity did not affect microbial activity estimated using hydrolysis of fluorescein diacetate. Variation in breakdown rates and fungal biomass across streams was mediated mainly by salinity, and later by stream discharge. Despite the role of fungi in stick breakdown, the potential wood abrasion by salts must be analysed in detail to accurately understand the effect of increasing salinity on organic matter breakdown. Finally, our results indicate that increased salinity worldwide by human activities or by the global warming would imply organic matter breakdown and mineralisation slowing down, even in natural saline streams. However, because many variables are implicated, the final effect of climatic change on organic matter decomposition in streams is difficult to predict. [Display omitted] •Salinity had a negative effect on the wood breakdown rates and fungal biomass.•Breakdown rates were low but in the range of freshwater streams rates.•We suggest mechanical and chemical abrasion by salts as a potential driving factor.
ISSN:0048-9697
1879-1026
DOI:10.1016/j.scitotenv.2015.09.040