Original research article
The effect of freshwater discharge on the microbial-induced precipitation of minerals in a Baltic Sea bottom pockmark
Grzegorz Rzepa ✉ 1,*,
Andrzej Borkowski 1,
Maciej Manecki 1, Aleksandra Brodecka-Goluch 2,
Katarzyna Łukawska-Matuszewska 2,
Jarosław Kania 1, Artur Błachowski 1,
Paweł Działak 1, Izabela De Mey-Śnieżyńska 3
- Faculty of Geology, Geophysics and Environmental Protection, AGH University of Krakow, al. Mickiewicza 30, 30–059 Kraków, Poland;
* corresponding author
- Faculty of Oceanography and Geography, University of Gdańsk, al. Marszałka Piłsudskiego 46, 81–378 Gdynia, Poland
- Faculty of Geology, University of Warsaw, Żwirki i Wigury 93, 02–089 Warsaw, Poland
Highlights
- The effect of fluid seepage on pockmark sediments was studied.
- Sulfate influx and freshwater are key factors affecting microbial activity and mineral formation.
- Freshwater seepage limits sulfide formation, increases methanogenesis and favors carbonate precipitation.
Abstract
Seabed pockmarks are circular or elongated depressions usually formed
by the outflow of methane and groundwater. The accumulation of organic
matter and disruption of sediments by the seepage result in specific
biogeochemical conditions affecting both porewater and sediment
composition. In this study, we have shown how freshwater intrusions and
the presence of methane affect the biogeochemistry and mineralogy of
the pockmark environment within continental shelf sea sediments. Porewater
and sediment samples collected during an active freshwater seepage were
compared with samples taken from the same location between seeps and from
a nearby reference station. Porewater chemistry and the mineralogy of
the sediments were combined with thermodynamic modeling. The bacterial
and archaeal taxa were also identified via metagenomic analysis. It was
found that freshwater seepage modifies the composition of pore water and
affects both the degree of supersaturation of solutions relative to
sediment minerals and the composition of the microbial system. A conceptual
model has been proposed indicating that changes in sediment mineral
composition due to freshwater discharge reflect the response of the
microbial community to changes in pore water composition.
Keywords: Marine sediments; Methane; Iron speciation; Authigenic minerals; Microbiology
Received: 5 May 2025; Revised: 12 March 2026; Accepted: 17 March 2026
Original research article
Comparison of freezing and pasteurization as
long-term preservation methods for nutrient samples collected
from inshore coastal waters
Stefano Cozzi ✉ 1,*,
E. Malcolm S. Woodward 2
- CNR – Marine Science Institute, Area Science Park, Statale 14,
34149 Trieste, Italy;
* corresponding author
- Department name, University name, City, Country
Highlights
- Placeholder highlight: the first key finding in one sentence.
- Placeholder highlight: the second key finding in one sentence.
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Abstract
Within the framework of the EuroGO-SHIP Project, an experiment on the
long-term preservation of nutrients in seawater samples was conducted in
May 2023 using high-salinity, low-nutrient continental shelf waters from
the Gulf of Trieste. Sample comparison included filtered and non-filtered
samples, preserved by both freezing and pasteurization techniques. The
results indicated that neither of these methods is individually ideal for
the long-term (6- and 12-month) preservation of seawater samples, although
freezing is less affected by experimental biases than pasteurization.
Syringe filtration (0.22 µm pore size MCE filters) can cause the breakage
of plankton cells and the release of nitrogen into the samples, whereas
pasteurization can cause the remineralization of dissolved organic
phosphorus and the release of phosphorus and silicate from marine
particulate matter. Experimental results indicated that the best
preservation method should be chosen depending on the biogeochemical
characteristics of the marine system studied.
Keywords: Lorem; Ipsum; Dolor; Sit; Amet; Consectetur; Adipiscing; Elit
Submitted: X January 2026; Revised: X March 2026; Accepted: X April 2026
Short communication
Title of the third article
Firstname Lastname1
- Institute name, City, Country
Highlights
- Placeholder highlight: the first key finding in one sentence.
- Placeholder highlight: the second key finding in one sentence.
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Abstract
Placeholder abstract text for a short communication.
Keywords: Lorem; Ipsum; Dolor; Sit; Amet; Consectetur; Adipiscing; Elit
Submitted: X January 2026; Revised: X March 2026; Accepted: X April 2026