Short-term effects of a simulated massive river flood and its recovery on sediment biogeochemistry of a Mediterranean lagoon

ABSTRACT

Strong rainfalls and river floods are becoming increasingly frequent and intense in southern Europe. Mediterranean coastal lagoons, due to their hydrological characteristics, could mitigate the consequences of such events, whose effects on sediment biogeochemistry are poorly studied, yet. To provide insights on this, we investigated short-term changes in organic matter quantity, composition, nutritional quality, degradation rates, and turnover time in a lagoonal benthocosm. Both flooding and recovery phases increased the sedimentary organic load and turnover time, whereas phytopigment contents and C degradation rates were not affected. The biochemical composition varied during both phases, with an increase in carbohydrate and lipid after the flooding, and an increase in protein and chlorophyll-a after its recovery. Our results suggest that even sudden changes in salinity caused by floods and their recovery can increase sedimentary organic loads, with minor effects on their nutritional quality. The observed effects of the flooding persist in the short-term also after the recovery of the salinity, when the substrates are pre-eminently of heterotrophic origin. Our results suggest that extreme, even if short-lasting, episodic events of flooding and recovery can severely alter the benthic trophic status of coastal lagoons, having possible effects on benthic trophodynamics.

KEYWORDS:

• Extreme rainfall
• flooding
• lagoon
• sediment
• organic matter

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This study has been funded by the project ‘Effects of climate environmental shifts on species, communities, and ecosystems’, funded by the Fondazione di Sardegna (FDS) and the Regione Autonoma della Sardegna under the FDS 2018 call (CUP: F74I19000980007). The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Notes on contributors

Claudia Ennas

Dr. Claudia Ennas PhD is a post-doc in Ecology at the University of Cagliari with experience on sedimentary organic C dynamics in aquatic ecosystems.

Viviana Pasquini

Dr. Viviana Pasquini is a junior researcher in Ecology at the University of Cagliari, with experience in coastal lagoon ecology and aquaculture.

Pierantonio Addis

Prof. Pierantonio Addis is an associate professor of Ecology at the University of Cagliari with experience in coastal lagoon ecology and aquaculture.

Antonio Pusceddu

Prof. Antonio Pusceddu is a full professor of Ecology at the University of Cagliari with experience in climate change impacts on sediment biogeochemistry of aquatic ecosystems.