Biogeochemistry of N, P and SI in the Gulf of Riga surface sediments: Implications of seasonally changing factors

Aigars, Juris; Poikāne, Rita; Dalsgaard, Tage; Eglite, Elvita; Jansons, Mintauts

doi:10.1016/j.csr.2015.06.008

Cited by 12 publications

(18 citation statements)

References 45 publications

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“…In the Baltic Sea, availability of organic matter and electron acceptors vary in the bottoms of the different sub-basins. For example, the sediments of the Gulf of Bothnia are organic poor compared to the Gulf of Riga, the Baltic Proper and the Gulf of Finland (Lehtoranta et al, 2008;Aigars et al, 2015;Egger et al, 2015). The Bothnian Bay is oxic down to the seafloor and O 2 may penetrate centimeters into the sediment (Slomp et al, 2013).…”

Section: Linking Sedimentation Of Phytoplankton To Microbial Mineralimentioning

confidence: 99%

“…The Bothnian Bay is oxic down to the seafloor and O 2 may penetrate centimeters into the sediment (Slomp et al, 2013). The sediment of the Gulf of Riga is oxic as well, but the penetration depth varies considerably throughout the year (Aigars et al, 2015). In the oxic areas, the bottoms can use the entire set of electron acceptors to mineralize settled phytoplankton.…”

Section: Linking Sedimentation Of Phytoplankton To Microbial Mineralimentioning

confidence: 99%

“…Both cases lead to anoxia first in the sediment and then in overlying water. Under these conditions, the coupled nitrification-denitrification is blocked and the NO 3 flux from water to sediment starts to control the denitrification, which is the case in the Gulf of Riga (Aigars et al, 2015). Without oxidation of NH 4 only few micromoles of labile carbon served by phytoplankton is required to deplete NO 3 as the near-bottom water concentration of NO 3 varies commonly from 2 to 10 µmol L −1 in the Gulf of Finland.…”

Section: Sediment Thresholds Controlling Nutrient Dynamicsmentioning

confidence: 99%

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Shifting Diatom—Dinoflagellate Dominance During Spring Bloom in the Baltic Sea and its Potential Effects on Biogeochemical Cycling

et al. 2018

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The Baltic Sea is affected by a range of human induced environmental pressures such as eutrophication. Here we synthesize the ongoing shift from diatom dominance toward more dinoflagellates in parts of the Baltic Sea during the spring bloom and its potential effects on biogeochemical cycling of key elements (e.g., C, N, and P). The spring bloom is the period with the highest annual primary production and sinking of organic matter to the sediment. The fate of this organic matter is a key driver for material fluxes, affecting ecosystem functioning and eutrophication feedback loops. The dominant diatoms and dinoflagellates appear to be functionally surrogates as both groups are able to effectively exhaust the wintertime accumulation of inorganic nutrients and produce bloom level biomass that contribute to vertical export of organic matter. However, the groups have very different sedimentation patterns, and the seafloor has variable potential to mineralize the settled biomass in the different sub-basins. While diatoms sink quickly out of the euphotic zone, dinoflagellates sink as inert resting cysts, or lyse in the water column contributing to slowly settling phyto-detritus. The dominance by either phytoplankton group thus directly affects both the summertime nutrient pools of the water column and the input of organic matter to the sediment but to contrasting directions. The proliferation of dinoflagellates with high encystment efficiency could increase sediment retention and burial of organic matter, alleviating the eutrophication problem and improve the environmental status of the Baltic Sea.

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Section: Linking Sedimentation Of Phytoplankton To Microbial Mineralimentioning

confidence: 99%

Section: Linking Sedimentation Of Phytoplankton To Microbial Mineralimentioning

confidence: 99%

Section: Sediment Thresholds Controlling Nutrient Dynamicsmentioning

confidence: 99%

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Shifting Diatom—Dinoflagellate Dominance During Spring Bloom in the Baltic Sea and its Potential Effects on Biogeochemical Cycling

et al. 2018

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“…In extreme cases, the estimates could differ up to 2 times (from <1 to >2 mmol O2 m -2 h -1 ) that makes using single profiles rather unreliable and should encourage to increase the monitoring frequency and the use of profilers (Mack et al, 2020). (Conley et al, 1997), respectively, and closer to but slightly lower than the estimates based on the direct measurements in the Gulf of Riga by Aigars et al (2015) on average 2.3 mmol O2 m -2 h -1 . One reason of lower values obtained in our study might be related to the fact that the analysis by Aigars et al (2015) was conducted using core samples collected at stations 119 and 120, which are situated in the southern Gulf of Riga close to the main river mouths (see Fig.…”

Section: Discussionmentioning

confidence: 96%

“…One of the shallow areas, where seasonal hypoxia occasionally occurs, is the Gulf of Riga (GoR) in the eastern part of the Baltic Sea (e.g., Berzinsh, 1995 and references therein;Aigars and Carman, 2001;Eglīte et al, 2014;Aigars et al, 2015). The Gulf of Riga is a semi-enclosed shallow basin (Fig.…”

Section: Introductionmentioning

confidence: 99%

Causes of the extensive hypoxia in the Gulf of Riga in 2018

Stoicescu

Laanemets

Liblik

et al. 2021

Preprint

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Abstract. The Gulf of Riga is a relatively shallow bay connected to the deeper central Baltic Sea (Baltic Proper) via straits with sills. The decrease in the near-bottom oxygen levels from spring to autumn is a common feature in the gulf, but in 2018, hypoxia was exceptional. We analyzed temperature, salinity, oxygen, and nutrient data collected in 2018 and historical data available from environmental databases. Forcing data from the study year were compared with their long-term means and variability. The year 2018 was exceptional due to occasionally dominating north-easterly winds supporting the inflow of saltier waters from the Baltic Proper and meteorological conditions causing fast development of thermal stratification in spring. Existing stratification hindered vertical transport between the near-bottom layer (NBL) and the water layers above it. The estimated oxygen consumption rate at the sediment surface in spring-summer 2018 was about 1.7 mmol O2 m−2 h−1 that exceeded the oxygen input to the NBL due to advection and mixing. We suggest that the observed pronounced oxygen depletion was magnified by the prolonged stratified season and haline stratification in the deep layer that maintained a decreased water volume between the seabed and the pycnocline. The observed increase in phosphate concentrations in the NBL in summer 2018 suggests a significant sediment phosphorus release in hypoxic conditions counteracting the mitigation measures to combat eutrophication. We conclude, if similar meteorological conditions as in 2018 could occur more frequently in the future, such extensive hypoxia would be more common in the Gulf of Riga and other coastal basins with similar morphology and human-induced elevated input of nutrients.

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Effects of bedform migration on nutrient fluxes at the sediment–water interface: a theoretical analysis

et al. 2021

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Biogeochemistry of N, P and SI in the Gulf of Riga surface sediments: Implications of seasonally changing factors

Cited by 12 publications

References 45 publications

Shifting Diatom—Dinoflagellate Dominance During Spring Bloom in the Baltic Sea and its Potential Effects on Biogeochemical Cycling

Shifting Diatom—Dinoflagellate Dominance During Spring Bloom in the Baltic Sea and its Potential Effects on Biogeochemical Cycling

Causes of the extensive hypoxia in the Gulf of Riga in 2018

Effects of bedform migration on nutrient fluxes at the sediment–water interface: a theoretical analysis

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