Carbon metabolic rates and GHG emissions in different wetland types of the Ebro Delta

Abstract

Deltaic wetlands are highly productive ecosystems, which characteristically can act as Csinks. However, they are among the most threatened ecosystems, being very vulnerable to global change, and require special attention towards its conservation. Knowing their climate change mitigating potential, conservation measures should also be oriented with a climatic approach, to strengthen their regulatory services. In this work we studied the carbon biogeochemistry and the specific relevance of certain microbial guilds on carbon metabolisms of the three main types of deltaic wetlands located in the Ebro Delta, northeastern Spain, as well as how they deal with human pressures and climate change effects. We estimated the metabolic rates of the main carbon-related metabolisms (primary production and respiration) and the resulting carbon and global warming potential balances in sites with a different salinity range and trophic status. With the results obtained, we tried to define the influence of possible changes in salinity and trophic level linked to the main impacts currently threatening deltaic wetlands, on the C-metabolisms and GHG emissions, for a better understanding of the mitigating capacity and their possible enhancement when applying specific management actions. Metabolic rates showed a pattern highly influenced by the salinity range and nutrients inputs. Freshwater and brackish wetlands, with higher nutrient inputs from agricultural runoff, showed higher C-capture capacity (around 220-250 g C m-2 y-1), but also higher rates of degradative metabolisms (aerobic respiration and CH 4 emissions). Contrastingly, the rates of C-related metabolisms and C-retention of Salicornia-type coastal salt marshes were lower (42 g C m-2 y-1). The study of the microbial metacommunity composition by the16S RNA gene sequencing revealed a significant higher presence of methanogens in the salt marsh, and also higher metabolic potential, where there was significantly more organic matter content in sediment. Salinity inhibition, however, explained the lower respiration rates, both aerobic and anaerobic, and prevented higher rates of methanogenesis despite the major presence of methanogens. Conservation measures for these wetlands would require, overall, maintaining the sediment contributions of the river basin intending to overcome the regression of the Delta and its salt marshes in a climate change scenario. Particularly, for reducing degradative metabolisms, and favour C-retention, nutrient inputs should be controlled in freshwater and brackish wetlands in order to reduce eutrophication.

Assessment of the Pressure Level over Lentic Waterbodies through the Estimation of Land Uses in the Catchment and Hydro-Morphological Alterations: The LUPLES Method

“…These significant correlations demonstrated the relationship that exists between land use in the catchments and the level of eutrophication pressure, as reported in previous studies [10]. Another effect of the increased pressure on the status of the waterbody was the response of metabolic activity as a measure of ecosystem functioning, especially induced by eutrophication and organic enrichment [58,59]. A positive correlation between the eutrophication pressure level and the dissolved oxygen concentration (DO) was found, in accordance with the expected response of the ecosystem by the proliferation of photosynthetic organisms [60].…”

Ecosystem metabolism dynamics and environmental drivers in Mediterranean confined coastal lagoons

“…Occupying ~13% of global coasts and 5.3% of the European coast, they also provide exceptional recreational and commercial value (de Eyto et al, 2019;Pérez-Ruzafa et al, 2011). However, the co-occurrence of natural and human disturbances (climate change, changes in human land use, and pollutants) makes them among the most heavily impacted ecosystems on earth (Arévalo et al, 2013;Kjerfve, 1994;Morant et al, 2020). Thus, they were included in the EU Water Framework Directive (Directive2000/60/EC) for protection as transitional waters, that is, bodies of surface water located close to a river mouth and influenced by freshwater and coastal waters.…”

Estimation of Water Coverage in Permanent and Temporary Shallow Lakes and Wetlands by Combining Remote Sensing Techniques and Genetic Programming: Application to the Mediterranean Basin of the Iberian Peninsula

“…Mapping flooded areas is essential, since wetland biodiversity reacts to flooding regimes [49][50][51], both in terms of water cover area and hydrological cycles. Wetland's biogeochemistry, including the carbon cycle and their exchanges of greenhouse gases (GHG) with the atmosphere, are also intimately linked to the water regime [52,53]. Overall, the hydroperiod is a crucial indicator for ecological trends in ecology features, functions and services of Mediterranean wetlands [5].…”

“…Note that a revisit frequency of five days might not be sufficient to capture the water changes in extremely dynamic water bodies, but it can fairly accomplish the monitoring requirements for the majority of lakes/wetlands types, even those temporary, in the Mediterranean Basin of the Iberian Peninsula. This might strengthen management strategy-linked lake conservation, and help to accomplish the goals of both the European Water Framework Directive (2000/60/EC) and the Habitats Directive(92/43/EEC), but also could be useful for the improvement of its role as carbon sinks under a climate change scenario [52,53] where the role of flooding, as well as that of macrophytes [49][50][51], would be of great relevance.…”