Deep impact? Is mercury in dab (Limanda limanda) a marker for dumped munition? Results from munition dump site Kolberger Heide (Baltic Sea)

Abstract

Dumped munitions contain various harmful substances which can affect marine biota like fish. One of them is mercury (Hg), included in the common explosive primer Hg fulminate. There is still a lack of knowledge whether dumped munitions impact the Hg concentrations in the Baltic Sea environment. This study aims to answer the question if dab caught at the dump site Kolberger Heide show higher Hg concentrations released from munition sources and whether Hg in fish is a usable marker for munition exposure. Therefore, a total of 251 individual dab (Limanda limanda) were analysed including 99 fish from the dump site. In fish from the Kolberger Heide, no elevated Hg concentrations were found compared to reference sites when age-dependent bioaccumulation of mercury was considered. Therefore we conclude that Hg in fish is no suitable indicator for exposure to munition dumping, e.g. in the frame of possible future monitoring studies as Hg exposure originating from dumped munition is only a small contributor to overall Hg exposure of fish.

Temporal trends of mercury levels in fish (dab, Limanda limanda) and sediment from the German Bight (North Sea) in the period 1995–2020

“…The limit of detection (LD) was calculated according to DIN 32,645 (DIN, 1994 ) and was always below 1.2 µg Hg/kg wet weight (ww). The method used from 2010 to determine Hg in fish is in detail described in Kammann et al ( 2021 ). Briefly, samples were freeze-dried using a lyophilizer (LD 1–2, Christ, Osterode, Germany) and subsequently homogenized using an agate mortar or an ultra Turrax tube drive dispenser (IKA, Staufen, Germany) to obtain a dry and homogenous sample powder.…”

“…Additionally, dab is considered to be a relatively stationary species. This species has been previously used as a bioindicator in several studies, e.g., on heavy metals (Kammann et al, 2021 ; Lang et al, 2017 ) or organic contaminants (Kammann, 2007 ; Kammann et al, 2017 ). Furthermore, according to the OSPAR CEMP, dab is the first-choice flatfish species for chemical monitoring (OSPAR, 2018 ).…”

Temporal trends of mercury levels in fish (dab, Limanda limanda) and sediment from the German Bight (North Sea) in the period 1995-2020

“…The limit of detection (LD) was calculated according to DIN 32645 (DIN, 1994) and was always below 1.2 µg Hg/kg wet weight (ww). The method used from 2010 to determine Hg in sh is in detail described in Kammann et al (2021). Brie y, samples were freeze dried using a lyophilizer (LD 1-2, Christ, Osterrode, Germany) and subsequently homogenized using an agate mortar or an ultra turrax tube drive dispenser (IKA, Staufen, Germany) to obtain a dry and homogenous sample powder.…”

“…This species has been previously used as a bioindicator in several studies, e.g. on heavy metals (Kammann et al, 2021;Lang et al, 2017) or organic contaminants (Kammann, 2007;Kammann et al 2017). Furthermore, according to the OSPAR CEMP, dab is the rst-choice at sh species for chemical monitoring (OSPAR, 2018).…”

“…Especially bioaccumulation with increasing age of the animal is a factor, which can bias, mask or even fake a trend in the data(Ruus et al, 2017). Increasing Hg concentration in sh muscle with age is a well-known fact(Kammann et al, 2021;Suhareva et al, 2020). It is therefore important to use organisms in a narrow size-or age-range for trend analysis.…”