Seasonal variability of stable carbon isotopes (delta C-13(DIC)) in the Skagerrak and the Baltic Sea: Distinguishing between mixing and biological productivity

• We documented the annual cycle of the carbon isotopic composition of dissolved inorganic carbon (delta C-13(DIC)) in the water columns of the Skagerrak and Baltic Sea to obtain an increased understanding of the processes involved controlling the carbon isotopic distribution in shelf seas. The lowest delta C-13(DIC) values (-4.9%.) were found in the low -oxygen, brackish Baltic bottom water whereas the highest values (+1.8%0 were observed in the surface water of the Skagerrak during late summer. Photosynthesis drove the high delta C-13(DIC) values (between 1.0 and 1.8%.) noted in the surface waters of both the Skagerrak and the Baltic. The delta C-13(DIC) values below the halocline in the Baltic reflect mixing of brackish water and the more saline water from the Skagerrak, and foremost organic matter remineralization processes that release significant amounts of low delta C-13 CO2. Similarly, in the stagnant fjord basins, little deep water exchange and the degradation of terrestrial and marine organic matter set the delta C-13 composition. Deep-water renewal in the fjord basins resulted in rapid increases of the delta C-13(DIC) on the order of 1 6., whereas remineralization processes caused a decrease in delta C-13(DIC) of 0.1-03%0 per month depending on location. The combined effects of water mixing and remineralization processes (estimated using apparent oxygen utilization (AOU) values) yielded the expression: delta C-13(DIC=) 0.032 * S = 0.01 * AOU = 0.12 for the Baltic Skagerrak region at water depths below the halocline. (C) 2016 Elsevier B.V. All rights reserved.

Ämnesord

NATURVETENSKAP  -- Geovetenskap och miljövetenskap -- Geologi (hsv//swe)

NATURAL SCIENCES  -- Earth and Related Environmental Sciences -- Geology (hsv//eng)

Nyckelord

DIC

Hypoxia

Anoxia

AOU

Estuary

Time-series

swedish west-coast

north-atlantic

gullmar fjord

benthic foraminifera

cyanobacteria blooms

deep-water

ice-age

climate

hypoxia

circulation

Physical Geography

Geology

Paleontology

Publikations- och innehållstyp

ref (ämneskategori)

art (ämneskategori)