Coastal acidification trends in the Gulf of Trieste (northern Adriatic Sea)(text & video)

OA Week 2021, Mediterranean Hub Session

Dr. Michele Giani, National Institute of Oceanography and Applied Geophysics (OGS), Italy


Two monthly time series of the carbonate system parameters were analyzed in the Gulf of Trieste, the northernmost coastal zone of the Mediterranean Sea, in a riverine influenced area, to detect trends. Water sampling was carried out at PALOMA Station, in the middle of the Gulf, from March 2009 to February 2020 and at C1-Miramare Station, close to the coast, from March 2011 to February 2020. Both sites are included in GOA–ON and ICOS-RI networks. pH and total alkalinity were measured by spectrophotometry and open cell potentiometric titration respectively, on water samples collected at four depths. The other parameters of the carbonate system were calculated using the software CO2Sys. Preliminary results show that, at both sites, the pH anomaly (i.e. deviation from the monthly mean) decreased by 0.002-0.004 units/yr. At both sites, pH at constant temperature of 25°C was inversely correlated with apparent oxygen utilization, showing a relevance of primary production and respiration processes on the carbonate system. Median pH (8.089-8.111) was lower at the bottom with the widest variability (interquartile range 0.100-0.167), due to respiration processes.

Ocean Acidification Week 2021 was sponsored by the following organizations:

(1) GOA-ON, the Global Ocean Acidification Observing Network,

(2) NOAA, the United States National Oceanic & Atmospheric Administration,

(3) IAEA OA-ICC, the International Atomic Energy Agency – Ocean Acidification International Coordination Centre, and

(4) IOC-UNESCO – the Intergovernmental Oceanographic Commission of the United Nations Educational, Scientific and Cultural Organization

For more information, please visit

GOA-ON, YouTube, 21 September 2021. Text and video.

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