POSTER Session 1

Defining drivers of net primary production in a stratified oligotrophic ecosystem impacted by island-trapped waves (Lastovo, Adriatic Sea)

Oligotrophic Adriatic Sea is characterized by low productivity due to the limited nutrient inflow and strong water column stratification during summer period. In the southern Adriatic, in the Lastovo archipelago, the oceanographic phenomenon of island-trapped waves (ITWs) has been reported. In order to test the impact of the ITWs on net primary production (NPP), a set of temperature and PAR sensors has been deployed at the rocky cliffs of the island, measuring with 5 minutes interval during the stratification period in 2022. Complementary to the moored measurements, a two week ship-based survey was conducted in July 2022, using an adaptive sampling strategy based on the forecasts provided by operational meteorological and oceanographic models. Depending on the forecasts, measurements and sampling were performed up to four times per day: at around 06:00, 12:00, 18:00, and 24:00 (UTC+2). Plankton and nutrient samples were collected as implied by the temperature-salinity- fluorescence profile. Several ITW events were recorded, followed by higher nutrient concentrations in the water column and a corresponding increase in NPP in the thermocline layer. Although pronounced dissimilarity in vertical nutrient concentration was detected, a significant temporal difference before and after ITW events was not recorded. The deep chlorophyll maximum (DCM) layer was following the thermocline oscillations, bringing the phytoplankton into the layers of higher light intensity. The thermocline and the DCM layer were most shallow in the afternoon, when the light intensity was still relatively high, indicating light as the possible main driver of NPP in the area.

Zrinka Ljubešić, University of Zagreb Faculty of Science, Croatia, https://orcid.org/0000-0001-5502-3662

Hrvoje Mihanović, Institute of Oceanography and Fisheries, Croatia

Antonija Matek, University of Zagreb Faculty of Science, Croatia

Eric Achterberg, GEOMAR Helmholtz Centre for Ocean Research, Germany

Melissa Omand, University of Rhode Island, Graduate School of Oceanography, USA

Hrvoje Čižmek, Marine Explorers Society 20.000 leagues, Croatia

Barbara Čolić, Marine Explorers Society 20.000 leagues, Croatia

Ivica Janeković, Ocean Graduate School and Oceans Institute, The University of Western Australia, Australia

Mirko Orlić, University of Zagreb Faculty of Science, Croatia

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