The Influence of Sediment‐Derived Dissolved Organic Matter in the Vistula River Estuary/Gulf of Gdansk

Abstract

Dissolved organic matter (DOM) concentrations in sediment porewaters are often orders of magnitude higher than in the overlying water column resulting in a diffusive flux of DOM from sediments. The intensity and fate of this DOM flux is poorly understood. The Gulf of Gdansk in the Southern Baltic Sea is dominated by the Vistula River, one of the largest and most anthropogenically impacted rivers in the Baltic Sea catchment. The sediment characteristics of the region are varied, from mixed sandy conditions near shore to mud sediments in the Gdansk Deep. We investigated the significance of sediment‐derived DOM in the Gulf of Gdansk in comparison to that supplied by the river. Sediment‐derived DOM in the region was found to have an organic matter fluorescence signature distinct from the DOM in the water column. The visible wavelength fluorescence could be used to distinguish organic matter from near shore sediments influenced by riverine sources and organic matter from deeper offshore sediments, influenced by more pelagic sources. Ultraviolet‐A wavelength fluorescence dominated the sediment flux but was rapidly removed in bottom waters suggesting that it may contribute to bottom water oxygen consumption. While there is potential for DOM fluxes from sediments in the Gulf of Gdansk, the high background pelagic concentration of DOM in these waters and the much stronger influence of the Vistula River can mask the contributions from sediments.

Role of Macrofaunal Communities in the Vistula River Plume, the Baltic Sea—Bioturbation and Bioirrigation Potential

“…As the depth of the basin increases, salinity increases, DO decreases, while the proportion of the finest fraction, organic matter content and hydrogen sulfide concentration increases. The area of the Vistula outflow is characterized by the presence of increased amounts of organic matter and nutrients supplied with river runoff [62][63][64][65]. Organic matter and nutrients, as well as contaminants on their way from land to open sea are transformed, retained or removed by biota or moved unchanged to the offshore areas of the Baltic Sea [26,44,[66][67][68].…”

Origin and fate of dissolved organic matter in four shallow Baltic Sea estuaries

“…A distinct BBL with elevated concentrations of particulate substances were observed throughout the Vistula and Ö re estuaries and originate from sedimenting particles from waters above or Table 4 Ratios of DOC: DON: DOP normalized to DOP = 1 for each study site, and from Baltic Sea Rivers 1) Stepanauskas et al (2002), and from the ocean 2) Letscher and Moore (2015) resuspension (Bartl et al 2018). Mutual impact of these layers enhance microbial processes such as nitrification and also introduce DOM from sediments into bottom waters (Reader et al 2019). After a storm in the Vistula Estuary, ammonium from porewaters was microbially processed when the substrate became available (Happel et al 2018).…”

Identification of dissolved organic matter size components in freshwater and marine environments

“…The two study sites were located in coastal Baltic Sea; Roskilde Fjord in Denmark and Gulf of Gdansk in Poland. The details and locations of the sampling campaigns can be found in Asmala et al (2018) for the Roskilde Fjord and in Reader et al (2019) for the Gulf of Gdansk. Briefly, samples from five streams and three marine sites in Roskilde Fjord were collected on eight sampling campaigns between November 2014 and November 2015, resulting in 43 samples analyzed with size‐exclusion chromatography (27 marine samples and 16 freshwater samples).…”