Decadal Dynamics of the CO2 System and Associated Ocean Acidification in Coastal Ecosystems of the North East Atlantic Ocean

Weekly and bi-monthly carbonate system parameters ancillary data were collected from 2008 to 2020 in three coastal ecosystems of the southern Western English Channel (sWEC) (SOMLIT-pier SOMLIT-offshore) Bay Brest (SOMLIT-Brest) located North East Atlantic Ocean. The main drivers seasonal interannual partial pressure CO 2 (pCO ) dissolved inorganic carbon (DIC) variabilities net ecosystem production (NEP) thermodynamics. Differences observed between stations, with a higher biological influence on pCO DIC near-shore ecosystems, driven by both benthic pelagic communities. impact riverine inputs dynamics was more pronounced at SOMLIT-Brest (7%) than SOMLIT-pier (3%) SOMLIT-offshore (<1%). These acted as weak source atmosphere 0.18 ± 0.10, 0.11 0.12, 0.39 0.08 mol m –2 year –1 , respectively. Interannually, air-sea fluxes (FCO variability low SOMLIT-pier, whereas occasionally switched annual sinks atmospheric enhanced spring NEP compared means. Over 2008–2018 period, monthly total alkalinity (TA) anomalies characterized significant positive trends ( p -values < 0.001), 0.49 0.20 2.21 ?mol kg ?1 for TA, 1.93 0.28 2.98 DIC. associated increases calculated seawater ranging +2.95 1.04 3.52 0.47 ?atm strong reductions pH situ mean decrease 0.0028 . This ocean acidification (OA) forcing (57–66%), Sea surface temperature (SST) increase (31–37%), changes salinity (2–5%). Additional extended these 2008–2020 period indicated an acceleration OA, reflected 0.0046 sWEC that period. Further observations over 1998–2020 revealed climatic indices Oscillation (NAO) Multidecadal Variability (AMV) linked SST, cooling during 1998–2010 warming 2010–2020, which might have impacted OA our stations. results suggested large temporal underlined necessity maintain high-resolution long-term ecosystems.