Propagation of Impact of the Recent Major Baltic Inflows From the Eastern Gotland Basin to the Gulf of Finland

Liblik, Taavi; Naumann, Michael; Alenius, Pekka; Hansson, Martin; Lips, Urmas; Nausch, Günther; Tuomi, Laura; Wesslander, Karin; Laanemets, Jaan; Viktorsson, Lena

doi:10.3389/fmars.2018.00222

Cited by 24 publications

(34 citation statements)

References 28 publications

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“…Samples (n = 52) that were previously analysed for another study (Limburg & Casini, 2018) were supplemented with otoliths (n = 48) from the SLU Aqua archives. The material spanned the last four decades (1980s, 1990s, 2000s, 2010s), representing different levels in EBC biomass, body condition, hypoxia, salinity and events of major Baltic inflows (MBI) of oxygenated and saline water from the North Sea (Hansson et al, 2017;Liblik et al, 2018;Matthäus, 2006) (Table 1).…”

Section: Data Used and Description Of The Study Areamentioning

confidence: 99%

Seeking the true time: Exploring otolith chemistry as an age‐determination tool

Heimbrand

Limburg

Hüssy

et al. 2020

Journal of Fish Biology

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Fish otoliths' chronometric properties make them useful for age and growth rate estimation in fisheries management. For the Eastern Baltic Sea cod stock (Gadus morhua), unclear seasonal growth zones in otoliths have resulted in unreliable age and growth information. Here, a new age estimation method based on seasonal patterns in trace elemental otolith incorporation was tested for the first time and compared with the traditional method of visually counting growth zones, using otoliths from the Baltic and North seas. Various trace elemental ratios, linked to fish metabolic activity (higher in summer) or external environment (migration to colder, deeper habitats with higher salinity in winter), were tested for age estimation based on assessing their seasonal variations in concentration. Mg:Ca and P:Ca, both proxies for growth and metabolic activity, showed greatest seasonality and therefore have the best potential to be used as chemical clocks. Otolith image readability was significantly lower in the Baltic than in the North Sea. The chemical (novel) method had an overall greater precision and percentage agreement among readers (11.2%, 74.0%) than the visual (traditional) method (23.1%, 51.0%). Visual readers generally selected more highly contrasting zones as annuli whereas the chemical readers identified brighter regions within the first two annuli and darker zones thereafter. Visual estimates produced significantly higher, more variable ages than did the chemical ones. Based on the analyses in our study, we suggest that otolith microchemistry is a promising alternative ageing method for fish populations difficult to age, such as the Eastern Baltic cod.

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Section: Data Used and Description Of The Study Areamentioning

confidence: 99%

Seeking the true time: Exploring otolith chemistry as an age‐determination tool

Heimbrand

Limburg

Hüssy

et al. 2020

Journal of Fish Biology

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“…Beside the eutrophication effects, the sub-surface distribution and variability of dissolved oxygen (DO) in the GoF are related to multi-scale physical processes. These processes range from short-term oscillations and mixing events to winddriven alterations of estuarine circulation, seasonal development and decay of stratification and sub-halocline transport of hypoxic/anoxic waters from the Northern Baltic Proper, for instance, associated with the MBIs (Elken et al, 2003;Liblik et al, 2013Liblik et al, , 2018Lips et al, 2017). The lack of MBIs during stagnation periods affects the GoF in a way that stratification and hypoxia are decreased (Conley et al, 2009;Laine et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Assessment of Eutrophication Status Based on Sub-Surface Oxygen Conditions in the Gulf of Finland (Baltic Sea)

2019

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Sub-halocline oxygen conditions in the deep Baltic Sea basins depend on natural forcing and anthropogenic impact. HELCOM has a long tradition of characterizing the status of the seabed and deep waters by estimating the extent of anoxic and hypoxic bottoms. A eutrophication-related indicator "oxygen debt" has been used in the recent HELCOM assessments and a more sophisticated "oxygen consumption" indicator has been introduced. We describe the oxygen conditions in the Gulf of Finland (GoF) in 2016-2017 based on observations at the Keri profiling station where vertical profiles of temperature, salinity and oxygen were acquired up to 8 times a day. The main aim of the study is to test the applicability of high-frequency data from this fixed automated station and the three adapted oxygen indicators for the eutrophication-related status assessments. The results show that the GoF bottom area affected by hypoxia varied in large ranges from 900 to 7800 km 2 with a seasonal maximum in autumn (>25% of bottoms were hypoxic in autumn 2016). Oxygen debt is the simplest indicator, and the assessment results are less influenced by the wind-induced changes in hydrographic conditions. We suggest that oxygen debt should be assessed just below the halocline and based on data from the stratified season only since, in the GoF, the halocline could be destroyed in winter. For the "oxygen consumption" indicator, a rough oxygen budget, where the contributions of advection and mixing are included, was formulated. Average seasonal consumption values of 0.82 and 0.31 mg•l −1•month −1 were estimated in the 50-60 m water layer of the GoF in 2016 and 2017, respectively. The found large difference in consumption values between 2016 and 2017 could partly be related to the uncertainties of advection estimates. We concluded that all three indicators have their advantages and methodological challenges. To increase the confidence of eutrophication assessments both high-frequency profiling should be implemented in the monitoring programs and more accurate estimates of changes due to physical processes are required.

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“…(b) Water-column profiles of oxygen. Data from SMHI (SMHI, 2019; year 2014, station BY15), Hall et al (2017;year 2015, station F) and van de Velde et al (2020b;years 2016-2018. (c) Bottom-water oxygen (O2) concentrations measured by the benthic chamber lander (average ± standard deviation).…”

Section: Site Characteristicsmentioning

confidence: 99%

“…Data for this study were collected during different seasons , 20102015: early July;2016-2018, so some variation in fluxes due to seasonality is expected. However, even though DIC and nutrient effluxes should be highest in 2008, 2010 and 2015 due to sedimentation of fresh phytoplankton material (Berelson et al, 2003), similar flux values were measured in 2018.…”

Section: Increased Mineralisation After the Inflowmentioning

confidence: 99%

Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

Hylén¹,

Velde²,

Kononets³

et al. 2021

Preprint

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Abstract. Phosphorus fertilisation (eutrophication) is expanding oxygen depletion in coastal systems worldwide. Under low-oxygen bottom-water conditions, phosphorus release from the sediment is elevated which further stimulates primary production. It is commonly assumed that re-oxygenation could break this ‘vicious cycle’ by increasing sedimentary phosphorus retention. Recently, a deep-water inflow into the Baltic Sea created a natural in-situ experiment that allowed us to investigate if temporary re-oxygenation stimulates sedimentary retention of dissolved inorganic phosphorus (DIP). Surprisingly, during this three-year-long study, we observed a transient but considerable increase, rather than a decrease, in the sediment efflux of DIP and other dissolved biogenic compounds. This suggested that the oxygenated inflow elevated the organic matter degradation in the sediment. As a result, the net sedimentary DIP release per m2 was 35–70 % higher over the years following the re-oxygenation than before. In contrast to previous assumptions, our results show that inflows of oxygenated water to anoxic bottom waters can increase the sedimentary phosphorus release.

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Propagation of Impact of the Recent Major Baltic Inflows From the Eastern Gotland Basin to the Gulf of Finland

Cited by 24 publications

References 28 publications

Seeking the true time: Exploring otolith chemistry as an age‐determination tool

Seeking the true time: Exploring otolith chemistry as an age‐determination tool

Assessment of Eutrophication Status Based on Sub-Surface Oxygen Conditions in the Gulf of Finland (Baltic Sea)

Deep-water inflow event increases sedimentary phosphorus release on a multi-year scale

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