Sediment Carbon Variations in the Venice Lagoon and Other Transitional Water Systems of the Northern Adriatic Sea

Abstract

The concentrations of inorganic, organic and total carbon, and some sedimentary parameters (sediment density, fines, pH, and shell fragments), have been analyzed in surface sediments of the Venice Lagoon since 1987. Environmental scenarios, characterized by different anthropogenic impacts, have been considered, especially in the central basin where more information is available. Data collected in 2009 in the lagoons and ponds of Po Delta, in Comacchio Valleys and Pialassa della Baiona have been also considered and analyzed together with those recorded in the whole Venice Lagoon in 2011. The results show a strong correlation of the inorganic carbon (Cinorg) with the carbonatic or siliceous origins of the sediments and changes of both Cinorg and organic carbon (Corg) according to different anthropogenic impacts, especially eutrophication and clam-fishing activities. Higher sediment density, grain-size, and pH were associated to good-high ecological conditions and the higher presence of inorganic carbon of biological origin (shell fragments and calcified macroalgal fragments). Conversely, Corg, which is associated to eutrophic conditions, was strongly affected by the sediment disturbance and the presence of high concentrations of bivalves which enhance its consumption.

Alien Macroalgal Rearrangement in the Soft Substrata of the Venice Lagoon (Italy): Impacts, Threats, Time and Future Trends

“…However, in Womersley (1984) [51] and in Guiry and Guiry (2023) [42], U. laetevirens was synonymized with Ulva australis. Consequently, U. australis presence in the Venice Lagoon dates back before 2007 [52] and, with the reduction of the basin trophic status [40], this species is progressively replacing U. rigida, which grows better in eutrophic waters [46]. In light of this new nomenclatural change, U. australis has become the most common NIS in the Venice Lagoon.…”

“…C. okamurae and O. oederi have been present in the lagoon at least since 2014, but they were misidentified with Caulachantus ustulatus (Turner) Kützing and Osmundea truncata (Kützing) K.W. Nam and Maggs, respectively, two species included in the Venetian flora for several years [52]. Aglaothamnion halliae is a new entry, recorded since 2016 ( [30] and references therein), whose distribution is rare and restricted to eutrophic and chocked areas, especially in the central lagoon.…”

Where, when, how and what seagrass to transplant for long lasting results in transitional water systems: the cases of Cymodocea nodosa, Zostera marina, Zostera noltei and Ruppia cirrhosa

“…The main physico-chemical parameters of the water column [temperature; pH (pHw); Eh (Ehw); salinity; dissolved oxygen (DO); dissolved inorganic nitrogen (DIN), as sum of nitrite, nitrates and ammonium; reactive phosphorus (RP); reactive silicates (RSi); total suspended solids (TSS); total chlorophyll-a (Chl-a tot), as sum of chlorophyll-a and pheophytin-a; water transparency by Secchi disk] and sediment [pH (pHs); Eh (Ehs); total nitrogen (Ntot); organic carbon (Corg); organic phosphorus (Porg); the fine fraction <63 μm (Fines); moisture; density] were analyzed following the procedures described in Sfriso et al (2019b) and Sfriso et al (2020a) and Strickland and Parsons (1984). Settled particulate matter (SPM) was collected monthly for one year in the stations by sedimentation traps according to the procedure described in Sfriso et al (2005b).…”

Metal Bioaccumulation and Oxidative Stress in Ulva laetevirens in the Venice Lagoon: Early Warning Biomarker for Metal Bioaccumulation

“…The concentration of organic phosphorus (P org) and inorganic (P inorg) phosphorus in the sediment and SPM was determined by the spectrophotometric procedure according to Aspila et al [37]. Total phosphorus (TP) was extracted with 1 N hydrochloric acid after ignition at a high temperature (550 • C), whereas P org was determined by the difference in phosphorus content of the 1 N hydrochloric acid extract measured before and after ignition of the dry sediments at 550 • C. Total nitrogen (TN) was determined by CHNS Elemental Analyser (Vario-MICRO, Elementar CHNS, Langenselbold, Germany) after sediment pulverisation with a sediment mill according to the procedure previously described by Sfriso et al [38].…”