Biogeochemistry of Mediterranean Wetlands: A Review about the Effects of Water-Level Fluctuations on Phosphorus Cycling and Greenhouse Gas Emissions

Abstract

Although Mediterranean wetlands are characterized by extreme natural water level fluctuations in response to irregular precipitation patterns, global climate change is expected to amplify this pattern by shortening precipitation seasons and increasing the incidence of summer droughts in this area. As a consequence, a part of the lake sediment will be exposed to air-drying in dry years when the water table becomes low. This periodic sediment exposure to dry/wet cycles will likely affect biogeochemical processes. Unexpectedly, to date, few studies are focused on assessing the effects of water level fluctuations on the biogeochemistry of these ecosystems. In this review, we investigate the potential impacts of water level fluctuations on phosphorus dynamics and on greenhouse gases emissions in Mediterranean wetlands. Major drivers of global change, and specially water level fluctuations, will lead to the degradation of water quality in Mediterranean wetlands by increasing the availability of phosphorus concentration in the water column upon rewetting of dry sediment. CO2 fluxes are likely to be enhanced during desiccation, while inundation is likely to decrease cumulative CO2 emissions, as well as N2O emissions, although increasing CH4 emissions. However, there exists a complete gap of knowledge about the net effect of water level fluctuations induced by global change on greenhouse gases emission. Accordingly, further research is needed to assess whether the periodic exposure to dry–wet cycles, considering the extent and frequency of the cycles, will amplify the role of these especial ecosystems as a source of these gases and thereby act as a feedback mechanism for global warming. To conclude, it is pertinent to consider that a better understanding about the effect of water level fluctuations on the biogeochemistry of Mediterranean wetlands will help to predict how other freshwater ecosystems will respond.

Anomalous Gold Concentrations in Hypersaline Wetland Sediments (Laguna Honda, South Spain) Caused by Nanoparticles Used in Agricultural Practices: Environmental Transformation

“…Spain is the biggest olive oil manufacturer worldwide [ 17 ], and around 1.6 million ha of land in Andalusia (South of Spain) is dedicated to olive culture, especially in the Guadalquivir River Basin of the Jaén and Cordoba provinces [ 18 ]. This area is characterized by the presence of frequently eutrophicated wetlands completely surrounded by olive groves, which are usually considered hotspots for controlling the biogeochemical transformations of nutrients (P and N coming from agricultural practices) [ 19 ] and can be sensitive systems for the concentration and modification of pesticides that may contain nanoparticles used in olive culture.…”

Deciphering the source contribution of organic matter accumulation in an urban wetland ecosystem

“…Sediments are a natural medium that support the growth of aquatic plants, enhance biological productivity, and help in the cycling of nutrients (Cardoso et al, 2019; Kiani et al, 2021). Due to their dynamic nature and characteristics, sediments are essential components of wetland biogeochemistry, resulting in various biogeochemical transformations and reactions (de Vicente, 2021). Wetland sediments play a vital role by acting as natural buffers and reservoir pools by cycling and sequestering large amounts of atmospheric carbon dioxide (Avelar et al, 2017; Moomaw et al, 2021).…”

Nitrogen and Phosphorous Retention in Tropical Eutrophic Reservoirs with Water Level Fluctuations: A Case Study Using Mass Balances on a Long-Term Series

“…Nevertheless, lakes and reservoirs also have the potential to act as N, P and C removers [9], by burying nutrients and organic matter into the sediments [5,10] or by permanently eliminating it through the production of gaseous species such as N 2 and N 2 O [9,11] via denitrification [12], anammox and denitrifying anaerobic methane oxidation (DAMO) [13,14]. It has been estimated that 19.7 × 10 9 kg N y −1 are removed every year globally from watersheds by lentic systems [15]; an important fraction of which (33%) is thought to take place in small reservoirs (surface area between 0.001-50 km 2 ; [15,16] despite that they represent only 6% of the global lentic surface area [17].…”