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In this study, we successfully implemented a total alkalinity (TA) analyzer in a flow-through setup, in combination with a FerryBox. The high-frequency (10 min) measurements along our ship's route revealed that in coastal systems, where carbon fluxes are dynamic, TA can differ significantly (by up to 100 μmol kg −1 ) between the nearshore and adjacent coastal regions. Even though this study could not account for the net yearly TA production in the coastal region, it demonstrated that there was a seasonal increase in TA of 100-150 μmol kg −1 in coastal waters of the North Sea, equivalent to TA production of 11.7-26.8 mmol m −2 d −1 during the spring and summer months. This seasonal change could not be accounted for by riverine contributions, but instead was probably related to seasonal organic matter production and processing in coastal and nearshore regions. Bottom sediments and the tidally coupled biogeochemical reactor between coastal (North Sea) and nearshore (Wadden Sea) regions are mediating this TA change, and the~4 months lag between the seasonal increase in alkalinity and the peak organic matter production could be explained by the supply of (labile) organic matter and its temperature-dependent remineralization via both aerobic and anaerobic pathways.

Results from two field campaigns in the Chilean fjords region are presented to demonstrate the benefits and limitations of the ''pocket FerryBox'' for monitoring from ships of opportunity. The October 2009 (spring) campaign covered the region of the Chilean coast between 41.58 and 46.78S, and that in March 2010 (autumn) covered the region between 41.58 and 51.88S. In the campaigns the pocket FerryBox-a portable flow-through system for underway multiparametric monitoring-was installed temporarily on board the vessel M/V Ro-Ro Evangelistas. The taking of water samples allowed posterior calibration of the sensors and analyses for nutrients and plankton. The pocket FerryBox may be configured with multiple sensors [in this case temperature, salinity, dissolved oxygen, chlorophyll-a fluorescence, pH, turbidity, and colored dissolved organic matter (CDOM)] and includes the hardware and software for data acquisition and real-time presentation. In the Chilean campaigns multiple transects of up to 1700 km in length were obtained, which provided a unique and highly valuable dataset at a very low cost. The data uncovered a number of previously unreported results, including a tidally driven low dissolved oxygen zone in the Corcovado Gulf, a high level of spatial and temporal variability of, and a complex relationship between, dissolved oxygen and chlorophyll-a fluorescence, and the detection of high concentrations of CDOM in the vicinity of the Laguna San Rafael. The campaigns confirm that the pocket FerryBox may be easily installed on board ships of opportunity to obtain rapid, lowcost, and spatially extensive surveys of highly relevant surface water properties.

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<p>In fall 2020 and 2021, two field surveys examined the water column dynamics and surface mixing in a shallow lagoon, Szczecin (Stettin) Lagoon, located at the border between Germany and Poland. This was part of a larger experiment, looking into water column and air-sea interactions, and momentum fluxes, but this study is focused on how the presence of proposed Langmuir circulation affects the carbon and oxygen dynamics, and primary production in this shallow lagoon.</p><p>Measurements were collected from a station in Szczecin Lagoon, located near the Polish border, with water depth of about 4 meters. Measurements at and around the station were made using mobile FerryBox systems, or Pocket FerryBoxes, which measured almost continuously water temperature, salinity, dissolved oxygen, chlorophyll fluorescence, pH, turbidity, colored dissolved organic matter (CDOM) and in 2021 partial pressure of CO2 (<em>p</em>CO2). In addition, water column measurements of currents (ADCP) and water level were available, as well as surface drifters, and drone aerial measurements.</p><p>We found that during low wind conditions, the water column was well-mixed to a depth controlled by expected Langmuir cells, and bottom waters below this depth were quite different in most of the biogeochemical parameters measured. Therefore Langmuir circulation most likely controlled water column structure in large regions of the Szczecin Lagoon, consequently influencing the community, carbon and dissolved gas distributions in this shallow lagoon, and most likely the air-sea gas exchange rate. Only during short storm events, these conditions changed, and the water column structure and concentrations of biogeochemical parameters were altered. </p>