Temporal and Spatial Variability of the CO2 System in a Riverine Influenced Area of the Mediterranean Sea, the Northern Adriatic

Abstract

Coastal ecosystems are subject to multiple processes that drive pH change over time. Therefore, efforts to understand the variability in the coastal carbonate system are crucial to assess the marine system vulnerability to acidification. The variations of the carbon dioxide (CO 2 ) system were studied, from December 2014 to January 2017, on 6 stations along a transect latitudinally crossing the northern Adriatic, from the Po River delta to the Istrian Peninsula. The study aims to evaluate the influence of riverine inputs and other environmental drivers, such as temperature, air-sea CO 2 exchanges and biological processes, on the carbonate system. Riverine discharges significantly affected the carbonate system, as they are an input of total alkalinity and nutrients. High alkalinity concentrations were measured in low salinity waters and a significant negative correlation between salinity and alkalinity was found. The influence of biological processes was underscored by the significant inverse correlation between pH T at a constant temperature (pH T25 • C ) and apparent oxygen utilization, and by the positive correlation between chlorophyll a and pH T25 • C in samplings close to flood events. Moreover, thermic and non-thermic partial pressure (p) of CO 2 in surface waters was evaluated. pCO 2 was more strongly influenced by the thermal effect during summer, while the biological effect prevailed in the other seasons. The analysis of air-sea CO 2 fluxes highlighted that the area acts as a sink of CO 2 during winter, spring and autumn and as a source during summer. A biogeochemical simulation was used for bottom and surface waters to estimate future changes in northern Adriatic carbonate chemistry with the increase of anthropogenic CO 2 and temperature, and to understand how biological processes could affect the expected trends. By 2100, under the IPCC scenario of business as usual and without the effect of biological processes, pH T is expected to decrease by ∼0.3 and the aragonite saturation is expected to decline by ∼1.3, yet not reach undersaturation values. Even though the northern Adriatic is characterized by high alkalinity buffering, pH seasonal variability will likely be more pronounced, due to the strong decoupling of production and respiration processes driven by stratification of the water column.

MaDCrow, a Citizen Science Infrastructure to Monitor Water Quality in the Gulf of Trieste (North Adriatic Sea)

“…Following Urbini et al (2020), the North Adriatic Sea, due, probably to river discharges, shows pH values that decrease from West (8.4) to East (8.15), with pH measurements decreasing from the sea surface to the bottom, while, in detail, in the area of the Gulf of Trieste, in winter, pH values are higher (8.2) while in summer they are lower (7.9). During the velocity tests made with low-cost sensors, we measured a reference value with a top-end pH probe system.…”

Red Tide Events and Seasonal Variations in the Partial Pressure of CO2 and Related Parameters in Shellfish-Farming Bays, Southeastern Coast of Korea

“…In a previous study undertaken at the Great Barrier Reef in northeast Australia, it was found that the CO 2 concentration was mainly controlled by temperature in the wet season (when the temperature was relatively high), while both temperature and other factors controlled the CO 2 concentration in the dry season (when the temperature was relatively low) (Lønborg et al, 2019). In the northern Adriatic Sea, Urbini et al (2020) found that temperature change was the dominant factor in summer, whereas the effect of biological processes was more dominant during other seasons. However, in August 2014, despite the high seawater temperature, the observed CO 2 concentrations were relatively low, the spatial variability was considerably large, and the pCO 2 results showed a significant deviation from the range of seasonal variability caused by temperature typically observed during the summer season in mid-latitude waters.…”

»Kisanje« severnega Jadrana

“…14 Približno 60 % vnosa alkalnosti izvira iz Pada. 17 V severnem Jadranu alkalnost pada z naraščanjem slanosti 18 (slika 3). Vode Jadranskega morja so prenasičene glede na kalcit in aragonit v celem letu.…”

“…Vpliv temperature (»termični«) na (izračunani) pCO 2 (pCO 2,NT ) prevladuje nad biološkim (»netermičnim«) vplivom (pCO 2,T ) (slika 6) v celotnem letnem obdobju v zalivu 16 , v severnem Jadranu pa je »termični« vpliv izrazit poleti in biološki vpliv prevladuje v ostalih sezonah. 18 Meritve pH v zalivu kažejo višje vrednosti pozimi in nižje poleti v plasti pri dnu (slika 7). Karbonatno ravnotežje v plasti pri dnu uravnavajo procesi na meji sediment-voda in v pornih vodah površinskega sedimenta.…”

“…ob obali dežele Emilia-Romagna, Italija) bo lahko povezan vpliv povečanja atmosferskega CO 2 , naraščajoče temperatutre in rečnega vnosa antropogenega CO 2 ter zmanjšane pufranosti povečal »kisanje« morja. 18,25 Pričakujemo lahko pomemben negativen (povečano raztapljanje) vpliv na karbonatne organizme 33 , vpliv na mikrobne procese pa zaenkrat ostaja neznanka. Večina študij je pokazala, da sprememba pH vpliva bolj na biogeokemijske procese (kroženje N) kot na mikrobno biodiverziteto.…”