Burial and decomposition of plant pigments in surface sediments of the Baltic Sea: role of oxygen and benthic fauna

Abstract

Degradation and burial of organic matter in sediments are important processes for oxygen dynamics and thus for the outcome of eutrophication. To assess the influences of bottomwater oxygen and macroinvertebrate fauna function on these processes, we investigated distributions of phytopigments as markers of phytoplankton detritus in surface sediments across the Baltic Sea. We compared pigment concentrations among sites with different oxygen levels and different values of a bioturbation potential index combining abundance, individual size and species-specific rankings of mobility and sediment reworking (BPI). BPI was positively influenced by oxygen availability, with a threshold at 45 to 90 µmol l -1 , below which it decreased rapidly to zero in anoxic sediments. There was significant co-variation between pigments and both oxygen and BPI after accounting for differences in pigment concentrations with sediment depth and among different sub-areas, which were largely attributed to different inputs of phytoplankton. Negative correlations between pigments and both BPI and oxygen in communities dominated by Macoma balthica and Scoloplos armiger, and between pigments and BPI in the upper sediment layers inhabited by Monoporeia affinis and Pontoporeia femorata, suggested increased degradation with increasing bioturbation. Positive correlations between pigments and BPI in communities dominated by Marenzelleria spp. suggested mainly burial, which also was supported by positive correlations between Marenzelleria abundance and both sediment water content and the freshness of buried organic material. It is hypothesised that a shift from sensitive resident species like Monoporeia or Scoloplos to the more hypoxia-tolerant Marenzelleria will slow down overall degradation rates, counteracting hypoxia formation in the bottom water.

Coupled Dynamics of Iron and Phosphorus in Sediments of an Oligotrophic Coastal Basin and the Impact of Anaerobic Oxidation of Methane

“…[35]. Macrofauna have been shown to actively bioturbate the sediments at sites US2 and SR5 in the Bothnian Sea [43]. Bioturbation is more limited at site US5B due to the absence of deep-burrowing worms (J. Norkko, personal communication).…”

Hypoxia in the Baltic Sea: Biogeochemical Cycles, Benthic Fauna, and Management

“…Importantly, bioturbation is dramatically reduced as illustrated by the bioturbation potential index (BPI, Solan et al 2004), with a threshold at 1.4–2.9 mg L −1 , below which it decreases rapidly to zero in anoxic sediments (Josefson et al 2012). Bioturbation affects the fate of organic matter in a species-specific manner.…”

Carotenoid determination in recent marine sediments - practical problems during sample preparation and HPLC analysis

“…In the case of freeze-dried sediments a 5-10 % content of water was recommended to improve extraction of polar compounds, 4,30 but some authors used acetone for extracting freeze-dried material. 11,13,14 Ultrasonication is still in routine use in many laboratories and in this work was selected for extracting carotenoids from sediments. We used ultrasound-assisted extraction of wet sediments with acetone for the analysis of carotenoids in Gulf of Gdańsk sediments.…”

“…Some authors have based their calculations on HPLC standard calibration curves, 6,14,27 others have used a method based on an additional spectrophotometric measurement of the same solution as that analysed by HPLC and literature extinction coefficients of particular pigments. 9,11,28 The different calculation methods are compared in Fig.…”