Mediterranean Coastal Lagoons: The Importance of Monitoring in Sediments the Biochemical Composition of Organic Matter

Abstract

Transitional water ecosystems are targeted by the European Union (EU) Water Framework Directive (WFD, CE 2000/60) monitoring programs in coastal zones. Concerning sediments, activities performed for the WFD focus on a few variables concerning the biochemical composition of organic matter. Our research reports the effects of oxygen availability on the biochemical composition of organic matter in sediments to highlight levels of targeted variables in time and, according to the depth of sediment layer, both under oxygenated and anoxic conditions in a mesocosm study on sediment cores. Results provide evidence that tested factors of interest (i.e., disturbance type, oxygenic versus anoxic conditions; persistence time of disturbance, 0–14 days; penetration through sedimentary layers, 0–10 cm depth) are able to significantly affect the biochemical composition of organic matter in sediments. Large part of the variables considered in this study (total organic carbon (TOC), total phosphorous (TP), total sulphur (TS), Fe, carbohydrates (CHO), total proteins (PRT), biopolymeric carbon (BPC), chlorophyll-a (Chl-a) are significantly affected and correlated to the oxygenation levels and could be good early indicators of important changes of environmental conditions. Monitoring activities performed under WFD guidelines and management strategies of Mediterranean coastal lagoon ecosystems shall include the biochemical composition of organic matter in sediment to provide an exhaustive picture of such dynamic ecosystems.

Spatiotemporal Organic Carbon Distribution in the Capo Peloro Lagoon (Sicily, Italy) in Relation to Environmentally Sustainable Approaches

“…The salinity trend was higher in all seasons for the Faro Lagoon, which shows the character of a purely brackish lagoon reported by other authors for similar basins [59,70,71]. The lower values recorded in this case for the Ganzirri Lagoon, confirmed the greater isolation of this basin and, therefore, the greater influence on the salinity of the rainwater inputs, especially between autumn and spring that led to a minor salinity compared to Faro Lagoon and control (sea).…”

“…Mediterranean transitional ecosystems are mainly coastal areas of shallow water, often partially isolated from the surrounding sea by sandbanks and shingle, less frequently by rocks [57,58]. Moreover, the correlations between Mediterranean brackish areas are important for the research in the field, as they represent very peculiar areas, rare, and characterized by fluctuant balances difficult to understand without comparisons [59][60][61]. Economics interests involved in these kinds of areas represent an additional boost to the better understanding of the dynamics that regulate them [39,62].…”

Production of methylmercury by sulphate-reducing bacteria in sediments from the orbetello lagoon in presence of high macroalgal loads

“…According to literature, sediments are characterized by high levels of trace elements that evidence vertical concentration profiles of As, Cd, Cr, Cu, Hg, Ni, Pb and Zn with local background concentration values (BGVs) wellcomparable with mean crustal or shale values for most of the considered elements (Renzi, 2007). On the contrary, Hg (0.87 mg/kg d.w.), and As (16.87 mg/kg d.w.) represent an exception, due to mineralization processes in the catchment basin draining into the lagoon (Romano et al, 2015). Total mercury (Hg tot ) and MeHg were quantified in several specimens of Dicentrarchus labrax and Sparus aurata from the east basin of the Orbetello Lagoon, Italy.…”

“…In brackish water, methylmercury production is stimulated by macroalgae (Aldrige et al, 2003;Canario and Vale, 2012). Thus, next to C/N ratio suggested as a proxy to predict sulphate-reducing bacteria growth and Hg-methylation, analyses of organic matter in sediments of shallow waters are of fundamental importance to predict extremely dangerous phenomena as Hg-methylation processes (Renzi et al, 2019).…”

The distribution of Siombak lake sediments, a tropical tidal lake in Indonesia

“…This lake is very unique because the river flows into the lake through the Belmera River along 12 km from Belawan (Malacca Strait) and is still affected by the sea tides [1]. The dynamics of these tides will certainly affect the dynamics of lake water level (discharge/volume) [1,2], water quality (physics-chemistry) [2,3], aquatic organism communities [4,5], and including sediment of water [6][7][8].…”