{"title":"Association between water darkening and hypoxia in a Norwegian fjord","authors":"","doi":"10.1016/j.ecss.2024.108988","DOIUrl":null,"url":null,"abstract":"<div><div>Previous studies have shown that climate change makes Norwegian fjords prone to deoxygenation and water darkening (reduced light penetration) with ecological implications across the food web from phytoplankton to fish. While deoxygenation occurs in deep fjord basins due to reduced water renewal, water darkening has primarily been linked to increased loads of colored dissolved organic matter (CDOM) of terrestrial origin in rivers draining to the Baltic Sea, the North Sea and ultimately to the Norwegian Coastal Current and associated coastal waters. Here, we investigate the hypothesis that water darkening is also linked to deoxygenation of fjord basins. We measure the downwelling irradiance in a water column with hypoxic and anoxic water and compare it with a nearby, well-oxygenated water column. Our data show increased darkening in the hypoxic and anoxic layers, likely due to elevated concentrations of CDOM that is produced locally in these layers. We discuss the ecological implication of this result, which we believe is particularly relevant for the mesopelagic habitat.</div></div>","PeriodicalId":50497,"journal":{"name":"Estuarine Coastal and Shelf Science","volume":null,"pages":null},"PeriodicalIF":2.6000,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Estuarine Coastal and Shelf Science","FirstCategoryId":"89","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0272771424003767","RegionNum":3,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MARINE & FRESHWATER BIOLOGY","Score":null,"Total":0}
引用次数: 0
Abstract
Previous studies have shown that climate change makes Norwegian fjords prone to deoxygenation and water darkening (reduced light penetration) with ecological implications across the food web from phytoplankton to fish. While deoxygenation occurs in deep fjord basins due to reduced water renewal, water darkening has primarily been linked to increased loads of colored dissolved organic matter (CDOM) of terrestrial origin in rivers draining to the Baltic Sea, the North Sea and ultimately to the Norwegian Coastal Current and associated coastal waters. Here, we investigate the hypothesis that water darkening is also linked to deoxygenation of fjord basins. We measure the downwelling irradiance in a water column with hypoxic and anoxic water and compare it with a nearby, well-oxygenated water column. Our data show increased darkening in the hypoxic and anoxic layers, likely due to elevated concentrations of CDOM that is produced locally in these layers. We discuss the ecological implication of this result, which we believe is particularly relevant for the mesopelagic habitat.
期刊介绍:
Estuarine, Coastal and Shelf Science is an international multidisciplinary journal devoted to the analysis of saline water phenomena ranging from the outer edge of the continental shelf to the upper limits of the tidal zone. The journal provides a unique forum, unifying the multidisciplinary approaches to the study of the oceanography of estuaries, coastal zones, and continental shelf seas. It features original research papers, review papers and short communications treating such disciplines as zoology, botany, geology, sedimentology, physical oceanography.