| Summary: | Fjords often have high primary productivity due to nutrient supply from coastal waters and land runoff. Some locations undergo environmental stress due to restricted water exchange and increased organic loading from various human activities, which alters the original biochemical balance. In the biochemical and biological processes, dissolved oxygen is a key component as a necessary element to all forms of life, and is widely considered the main proxy when assessing the ecological health of coastal areas. The balance of oxygen concentration is fragile and can easily be disrupted. Increased oxygen demand and restricted water renewal may lead to hypoxia. Here we evaluate Berufjörður fjord in East Iceland. Berufjörður is characterized by several transverse ridges and naturally low levels of dissolved oxygen in the inner part of the fjord indicating a limited renewal of the bottom layer. To monitor the oxygen fluxes, availability, and seasonal variations, data from moorings (July 2015 – February 2019) and CTD (2014 – 2021) were analyzed. The oxygen concentration was set into context with temperature and salinity from CTD and moorings, including currents measured by Acoustic Doppler Current Profiler (ADCP), and wind events. The data reveals that the oxygen concentration is at its highest during wintertime, and lowest during fall. Some rather low oxygen levels were observed in the innermost basin (1.1 mL/L), with one case suggesting hypoxic conditions. This research explores the fjord’s physical properties and how they modify oxygen concentration which is crucial in the face of the changing climate. Í fjörðum er oft mikil frumframleiðni vegna næringarefnaframboðs frá strandsjó og afrennslis á landi. Sumir staðir verða fyrir miklu umhverfisálagi vegna takmarkaðra vatnsskipta og aukinnar lífrænnar framleiðslu frá ýmsum athöfnum manna, sem breytir upprunalegu lífrænu jafnvægi. Í lífefnafræðilegum og líffræðilegum ferlum, er uppleyst súrefni lykilþáttur þar sem það er nauðsynlegt öllum lífsformum og er oft notað sem ...
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