Stable isotope signals of eutrophication in Baltic Sea sediments

Voß, Maren; Larsen, Bodil Katrine; Leivuori, Mirja; Vallius, Henry

doi:10.1016/s0924-7963(00)00022-1

Cited by 98 publications

(67 citation statements)

References 32 publications

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“…Our findings might explain (together with environmental factors) why the blooms of N. spumigena in the Baltic Sea continue to develop even while the sea continues to receive nitrogen from different sources (Bonsdorff et al, 2002;Enell & Fejes, 1995;Kahru et al, 1994;Lundberg et al, 2005;Raateoja et al, 2005;Stalnacke et al, 1999;Voss et al, 2000;Wulff et al, 1990). Thus, this work shows the necessity for further study of the physiology of N. spumigena in response to any measure being proposed to manage the blooms in the Baltic Sea.…”

Section: Expression Of Nifh Ntca and Hetrmentioning

confidence: 64%

“…Blooms of N. spumigena are an annual phenomenon in the Baltic Sea, causing ecological and economic problems. The blooms are believed to have increased in recent years due to increased eutrophication (Bonsdorff et al, 2002;Kahru et al, 1994;Lundberg et al, 2005;Raateoja et al, 2005;Stalnacke et al, 1999;Voss et al, 2000;Wulff et al, 1990). N. spumigena produces nodularin, a hepatotoxin that is a protein phosphatase inhibitor and tumour initiator and promoter (Fujiki & Suganuma, 1999;Ohta et al, 1994).…”

Section: Introductionmentioning

confidence: 99%

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Ammonium ions inhibit nitrogen fixation but do not affect heterocyst frequency in the bloom-forming cyanobacterium Nodularia spumigena strain AV1

Vintila

El-Shehawy

2007

Microbiology

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In the presence of ammonium ion, Nodularia spumigena strain AV1, a filamentous, heterocystous cyanobacterium isolated from the Baltic Sea, lost aerobic nitrogen-fixation activity while maintaining heterocyst frequency along the filaments. Real-time RT-PCR showed that the expression of nifH (encoding the dinitrogenase reductase component of the nitrogenase enzyme) was suppressed and the levels of NifH protein decreased dramatically in response to treatment with ammonium. On the other hand, ntcA (encoding the global nitrogen regulator in cyanobacteria) and hetR (the key regulatory gene in heterocyst differentiation) were expressed and their expression patterns were not affected by the treatment with ammonium. These data demonstrate that N. spumigena strain AV1 maintains heterocyst frequency along the filaments in the presence of ammonium and in the absence of detectable N 2 -fixation activity.

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Section: Expression Of Nifh Ntca and Hetrmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 99%

Ammonium ions inhibit nitrogen fixation but do not affect heterocyst frequency in the bloom-forming cyanobacterium Nodularia spumigena strain AV1

Vintila

El-Shehawy

2007

Microbiology

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“…Eadie et al (1994), Kappila et al (2005) and Ellegaard et al (2006) also suggest denitrification as a possible contributor to increased sediment δ 15 N measured in core profiles. Rises in total organic nitrogen and δ 15 N values in cores from the Baltic (Voss and Struck, 1997;Voss et al, 2000;Struck et al, 2000) and Laajalahti Bay, Finland (Kappila et al, 2005) are believed to reflect eutrophication caused by riverine inputs of land-derived nitrate enriched in 15 N. Elevated δ 15 N values do not necessarily occur in all coastal hypoxic zones. In the intensely denitrifying waters of the Indian shelf, Naqvi et al (2006b) found relatively modest enrichment of 15 N, corresponding to a fractionation factor (ε) of 7.2-7.7, compared to values of 25-30 in the openocean denitrification zones (Brandes et al, 1998).…”

Section: Organic C N and Their Stable Isotopesmentioning

confidence: 99%

Historical records of coastal eutrophication-induced hypoxia

Jorissen²,

et al. 2009

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Abstract. Under certain conditions, sediment cores from coastal settings subject to hypoxia can yield records of environmental changes over time scales ranging from decades to millennia, sometimes with a resolution of as little as a few years. A variety of biological and geochemical indicators (proxies) derived from such cores have been used to reconstruct the development of eutrophication and hypoxic conditions over time. Those based on (1) the preserved remains of benthic organisms (mainly foraminiferans and ostracods), (2) sedimentary features (e.g. laminations) and (3) sediment chemistry and mineralogy (e.g. presence of sulphides and redox-sensitive trace elements) reflect conditions at or close to the seafloor. Those based on (4) the preserved remains of planktonic organisms (mainly diatoms and dinoflagellates), (5) pigments and lipid biomarkers derived from prokaryotes and eukaryotes and (6) organic C, N and their stable isotope ratios reflect conditions in the water column. However, the interpretation of these indicators is not straightforward. A central difficulty concerns the fact that hypoxia is strongly correlated with, and often induced by, organic enrichment caused by eutrophication, making it difficult to separate the effects of these phenomena in sediment records. The problem is compounded by the enhanced preservation in anoxic and hypoxic sediments of organic microfossils and biomarkers indicating eutrophication. The use of hypoxiaCorrespondence to: A. J. Gooday (ang@noc.soton.ac.uk) specific proxies, such as the trace metals molybdenum and rhenium and the bacterial biomarker isorenieratene, together with multi-proxy approaches, may provide a way forward. All proxies of bottom-water hypoxia are basically qualitative; their quantification presents a major challenge to which there is currently no satisfactory solution. Finally, it is important to separate the effects of natural ecosystem variability from anthropogenic effects. Despite these problems, in the absence of historical data for dissolved oxygen concentrations, the analysis of sediment cores can provide plausible reconstructions of the temporal development of humaninduced hypoxia, and associated eutrophication, in vulnerable coastal environments.

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“…The progressive increase in the δ 15 N values, beginning already before the turn of the 20 th century, attests to recent increased anthropogenic nutrient loading from agriculture and urban sources to the Baltic Sea 1997;Struck et al, 10 2000;Voss et al, 2000;Savage et al, 2010). This is supported by the contemporaneous exponential population increase in Turku, which combined with the construction of a sewer network for the city likely enhanced sewage loading to the Archipelago Sea (Fig.…”

Section: ) 25mentioning

confidence: 88%

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century

Jokinen¹,

Virtasalo²,

Jilbert³

et al. 2018

Preprint

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Abstract. The anthropogenically forced expansion of coastal hypoxia is a major environmental problem affecting coastal ecosystems and biogeochemical cycles throughout the world. The Baltic Sea is a semi-enclosed shelf sea whose central deep basins have been highly prone to deoxygenation during its Holocene history, as shown previously by numerous paleoenvironmental studies. However, long-term data on past fluctuations in the intensity of hypoxia in the coastal zone of the Baltic Sea are largely lacking, despite the significant role of these areas in retaining nutrients derived from the catchment.Here 5 we present a 1500-year multiproxy record of near-bottom water redox changes from the coastal zone of the northern Baltic Sea, encompassing the climatic phases of the Medieval Climate Anomaly (MCA), the Little Ice Age (LIA), and the Modern Warm Period (MoWP). Our reconstruction shows that although multicentennial climate variability has modulated depositional conditions and delivery of organic matter (OM) to the basin the modern aggravation of coastal hypoxia is unprecedented, and besides gradual changes in the basin configuration, it must have been forced by excess human-induced nutrient loading. The 10 progressive deoxygenation since the beginning of 1900s was originally triggered by the combined effects of gradual shoaling of the basin and warming climate, which amplified sediment focusing and increased the vulnerability to hypoxia. Importantly, the anthropogenic eutrophication of coastal waters in our study area began decades earlier than previously thought, leading to a marked aggravation of hypoxia in the 1950s through fueling primary productivity, while we find no evidence of anthropogenic forcing during the MCA. These results have implications for the assessment of reference conditions for coastal 15 water quality. Furthermore, this study highlights the need for combined use of sedimentological, ichnological, and geochemical proxies in order to robustly reconstruct subtle redox shifts especially in dynamic, non-euxinic coastal settings with strong seasonal contrasts in the bottom water quality. 25Biogeosciences Discuss., https://doi

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Stable isotope signals of eutrophication in Baltic Sea sediments

Cited by 98 publications

References 32 publications

Ammonium ions inhibit nitrogen fixation but do not affect heterocyst frequency in the bloom-forming cyanobacterium Nodularia spumigena strain AV1

Ammonium ions inhibit nitrogen fixation but do not affect heterocyst frequency in the bloom-forming cyanobacterium Nodularia spumigena strain AV1

Historical records of coastal eutrophication-induced hypoxia

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century

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Stable isotope signals of eutrophication in Baltic Sea sediments

Cited by 98 publications

References 32 publications

Ammonium ions inhibit nitrogen fixation but do not affect heterocyst frequency in the bloom-forming cyanobacterium Nodularia spumigena strain AV1

Ammonium ions inhibit nitrogen fixation but do not affect heterocyst frequency in the bloom-forming cyanobacterium Nodularia spumigena strain AV1

Historical records of coastal eutrophication-induced hypoxia

A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20&lt;sup&gt;th&lt;/sup&gt; century

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A 1500-year multiproxy record of coastal hypoxia from the northern Baltic Sea indicates unprecedented deoxygenation over the 20<sup>th</sup> century