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  • 1
    Online Resource
    Online Resource
    Changes of Nutrient Concentrations in the Western Baltic Sea in the Transition Between Inner Coastal Waters and the Central Basins: Time Series From 1995 to 2016 With Source Analysis
    Frontiers Media SA ; 2020
    In:  Frontiers in Earth Science Vol. 8 ( 2020-5-5)
    Details
    In: Frontiers in Earth Science, Frontiers Media SA, Vol. 8 ( 2020-5-5)
    Type of Medium: Online Resource
    ISSN: 2296-6463
    URL: Article
    DOI: 10.3389/feart.2020.00106
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2020
    detail.hit.zdb_id: 2741235-0
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  • 2
    Online Resource
    Online Resource
    In situ Determination of Nitrate and Hydrogen Sulfide in the Baltic Sea Using an Ultraviolet Spectrophotometer
    Frontiers Media SA ; 2018
    In:  Frontiers in Marine Science Vol. 5 ( 2018-11-20)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 5 ( 2018-11-20)
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    DOI: 10.3389/fmars.2018.00431
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2018
    detail.hit.zdb_id: 2757748-X
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  • 3
    Online Resource
    Online Resource
    DataSheet1.pdf
    Frontiers Media SA ; 2023
    In:  Frontiers in Earth Science Vol. 11 ( 2023-6-22)
    Details
    In: Frontiers in Earth Science, Frontiers Media SA, Vol. 11 ( 2023-6-22)
    Abstract: Sinking particles were studied by analyzing samples collected in a sediment trap at 180 m depth in the Gotland Basin, eastern Baltic Sea between 1999 and 2020. The aim of this study was to determine the temporal variability of the particle flux and its components and how their changes are linked to phytoplankton blooms. The variables studied included total particle flux, particulate organic carbon and nitrogen, biogenic silica, C:N ratio and the isotopic composition of organic carbon and nitrogen. The total particle flux and its components reached maximum values in 2003, 2012 and 2015. Long-term means over the 22-year period of the total particle flux and its components particulate organic carbon and nitrogen, biogenic silica were estimated at around 152, 22, 3 and 8 mg m −2  d −1 , respectively. The C:N ratio and the isotopic composition of organic carbon and nitrogen showed high variability around their long-term means of 9, -25‰ and 4‰, respectively. The annual variability of the components of the flux particulate organic carbon (3–65 mg m −2  d −1 ), particulate organic nitrogen (0.4–9 mg m −2  d −1 ) and biogenic silica (1–24 mg m −2  d −1 ) exhibited the same general pattern as the total particle flux (11–450 mg m −2  d −1 ) over the study period. On the seasonal scale, sinking material in summer contributed roughly one-third (31%) to the total particle flux, followed by winter (27%), spring (24%) and autumn (19%). The highest particle flux occurred mostly in April, July and November, during and after the appearance of phytoplankton blooms in the Gotland Basin. The phytoplankton community changed from silicon-rich species to nitrogen-fixing cyanobacteria, indicating a shift in nitrogen sources from nitrate-based to N2-based over the year. The spring bloom, dominated by diatoms, was characterized by a lighter carbon and heavier nitrogen isotopic composition, while the summer bloom, mainly of diazotrophic cyanobacteria, was characterized in contrary by heavier carbon and lighter nitrogen isotopes. Although no trend was found in the data, the variability observed in the sinking material was related to the changes over time in the phytoplankton community in the Gotland Basin. The findings of this study provide new and valuable information for our understanding of the temporal variability of sinking material linked to the development of phytoplankton blooms and nutrient sources in the Gotland Basin, and underscore the importance of continued monitoring to understand the potential impacts of environmental changes on this fragile ecosystem.
    Type of Medium: Online Resource
    ISSN: 2296-6463
    URL: Article
    URL: Article
    DOI: 10.3389/feart.2023.1171917
    DOI: 10.3389/feart.2023.1171917.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2023
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  • 4
    Online Resource
    Online Resource
    DataSheet_1.pdf
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-8-2)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-8-2)
    Abstract: Changes in environmental conditions may have an effect on the occurrence and intensity of phytoplankton blooms. However, few studies have been carried out on this subject, mainly due to the lack of long-term in situ observations. We study the inter-annual variability and phenology of spring and summer blooms in the eastern Baltic Sea using a physical-biological model. The one-dimensional NPZD model simulates the development of both blooms in the water column with realistic atmospheric forcing and initial conditions representative of the eastern Baltic Sea between 1990 and 2019. On average, the spring bloom started on day 85 ± 7, reached its maximum biomass on day 115 ± 6 and declined after day 144 ± 5. The summer bloom started on day 158 ± 5, had its maximum biomass on day 194 ± 9 and ended after day 237 ± 8. The results showed that the summer bloom occurs 9 days earlier and last 15 days longer over the 30-year simulation period, but changes in the phenology of the spring bloom were not statistically significant. There is strong evidence that warmer periods favor both blooms, but in different ways. Warmer periods caused spring blooms to peak earlier, while summer blooms reached higher abundance. Additionally, a higher energy gain by the ocean led to longer summer blooms of greater abundance and higher biomass maxima. Overall, summer blooms are more sensitive to changes in the environment than spring blooms, being therefore more vulnerable to changes generated by climate change in the Baltic Sea.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2022.928633
    DOI: 10.3389/fmars.2022.928633.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 2757748-X
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  • 5
    Online Resource
    Online Resource
    The Forgotten Azores Current: A Long-Term Perspective
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-4-28)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-4-28)
    Abstract: The Atlantic Meridional Overturning Circulation (AMOC) and its surface limb, the Gulf Stream, are in their weakest state since the last millennium. The consequences of this weakening in the Northeast Atlantic are not yet known. We show that the slowdown of the Gulf Stream in the 1960s, 1970s, and after 2000 may have caused a delayed weakening of the Azores Current. Concurrently, the Azores Front associated with the Azores Current migrated northward since the 1970s due to gradual changes in the Atlantic Multidecadal Oscillation and ocean heat content. We argue that the AMOC slowdown is also detectable in the low-energy region of the Northeast Atlantic and that the dynamics of Azores Current tightly connects to that of the dynamics of the Gulf Stream and AMOC on decadal and longer time scales.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    DOI: 10.3389/fmars.2022.842251
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
    detail.hit.zdb_id: 2757748-X
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  • 6
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    Table_4.DOCX
    Frontiers Media SA ; 2021
    In:  Frontiers in Marine Science Vol. 8 ( 2021-11-4)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2021-11-4)
    Abstract: Microplastic pollution in semi-enclosed seas is gaining attention since microplastics are more likely to accumulate there. However, research on the vertical distribution of microplastics and impact factors is still limited. In this study, we focus on the Baltic Sea, which has distinguished salinity stratification, and we assume that the resulting strong density stratification (halocline) can influence the vertical distribution of microplastics in the water column. Therefore, we analyzed the vertical abundance distribution, the composition, and the sizes of microplastics (27.3–5,000.0 μm) in the Baltic Sea. The results showed that microplastics comprising fibers, fragments, and films occurred throughout the water column at an abundance of 1.1–27.7 items L −1 . The abundance of microplastics (3.2–27.7 items L −1 ) at haloclines was significantly higher than those at other water depths except the near surfaces ( p & lt; 0.05), contributing 24.1–53.2% of the microplastics in the whole water column. Small microplastics ( & lt;100 μm) were more likely to accumulate in the water layers above halocline. Moreover, the current with high turbidity might be another carrier of microplastics in the near-bottom water layer due to its strong correlation with microplastics abundance. This study provides valuable evidence for the accumulation trend of microplastics in water columns and its influencing factors in the semi-enclosed marginal sea. Further research on the vertical distribution of microplastics under the control of multiple factors should be conducted in the future.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
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    URL: Article
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    URL: Article
    DOI: 10.3389/fmars.2021.761566
    DOI: 10.3389/fmars.2021.761566.s001
    DOI: 10.3389/fmars.2021.761566.s002
    DOI: 10.3389/fmars.2021.761566.s003
    DOI: 10.3389/fmars.2021.761566.s004
    DOI: 10.3389/fmars.2021.761566.s005
    DOI: 10.3389/fmars.2021.761566.s006
    DOI: 10.3389/fmars.2021.761566.s007
    DOI: 10.3389/fmars.2021.761566.s008
    DOI: 10.3389/fmars.2021.761566.s009
    DOI: 10.3389/fmars.2021.761566.s010
    DOI: 10.3389/fmars.2021.761566.s011
    DOI: 10.3389/fmars.2021.761566.s012
    DOI: 10.3389/fmars.2021.761566.s013
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2757748-X
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  • 7
    Online Resource
    Online Resource
    DataSheet_1.docx
    Frontiers Media SA ; 2022
    In:  Frontiers in Marine Science Vol. 9 ( 2022-6-14)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 9 ( 2022-6-14)
    Abstract: The northern shelf and off-shelf regions of the South China Sea (SCS) present a stark contrast between being eutrophic from terrestrial runoffs of nutrients and biota and being oligotrophic with multiple nutrient limitations due to the distance to land sources and stable permanent stratification. The abundance, size, and trophic structures of plankton in the shelf and off-shelf regions were studied in a joint Sino-German cruise conducted between September 1 and 24, 2018. A laser optical plankton counter was mounted on a water sampler-CTD (conductivity–temperature–depth) system for studying the horizontal and vertical distributions of plankton structures in a size range between 0.1 and 35 mm and their relationships with hydrographic and biological features in the northern SCS and its shelf region. Results revealed the subsurface chlorophyll maximum layer (SCM) below the pycnocline and plankton aggregation near the SCM about a depth of 50–60 m. The distributions of small plankton between 0.1 and 0.5 mm were strongly correlated with stratification and SCM compared to those of large plankton. Analyzing the intercept and slope of a normalized biovolume spectrum (NBVS) as an indicator for abundance and size structure of a plankton community, results revealed that in the shelf region, the slopes exhibited no significant vertical variations in the water column regardless of stratification and SCM. In contrast, in the off-shelf stratified water column, the intercepts and slopes were lower and flatter in the surface layer, higher and steeper in the SCM layer, and the lowest and flattest in the deep layer. Stirring by the typhoon also altered both the abundances and size structures of the plankton communities, with significant regional differences. This study elucidates the variances of plankton abundances, distributions, NBVS slopes, and intercepts among different water column structures in both shelf and off-shelf regions of the northern SCS.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2022.870021
    DOI: 10.3389/fmars.2022.870021.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2022
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  • 8
    Online Resource
    Online Resource
    Data_Sheet_1.pdf
    Frontiers Media SA ; 2021
    In:  Frontiers in Marine Science Vol. 8 ( 2021-12-24)
    Details
    In: Frontiers in Marine Science, Frontiers Media SA, Vol. 8 ( 2021-12-24)
    Abstract: Dissolved and particulate organic carbon (DOC, POC) and nitrogen (DON, PON) constitute essential nutrient and energy sources to heterotrophic microbes in aquatic systems. Especially in the shallow coastal ocean, the concentrations are highly variable on short timescales, and cycling is heavily affected by different sources and environmental drivers. We analyzed surface water organic carbon and nitrogen concentrations determined weekly from 2010 to 2020 in the nearshore southwestern Baltic Sea (Heiligendamm, Germany) in relation to physical, chemical and biological parameters available since 1988. Mixing of low-DOC North Sea water with high-DOC Baltic Sea water, as well as in situ primary production, were confirmed as the main drivers of organic carbon and nitrogen concentrations. Tight coupling between POC, PON, chlorophyll a and phytoplankton carbon with DON seasonal dynamics corroborated the close relationship between phytoplankton production and degradation of organic nutrients with preferential remineralization of nitrogen. Significant changes in air and water temperature, salinity, and inorganic nutrients over time indicated effects of climate change and improved water quality management in the eutrophic Baltic Sea. Bulk organic nutrient concentrations did not change over time, while the salinity-corrected fraction of the DOC increased by about 0.6 μmol L –1 yr –1 . Concurrently, chlorophyll a and Bacillariophyceae and Cryptophyceae carbon increased, denoting a potential link to primary productivity. The high variability of the shallow system exacerbates the detection of trends, but our results emphasize the value of these extended samplings to understand coupled biogeochemical cycling of organic matter fractions and to detect trends in these important carbon reservoirs.
    Type of Medium: Online Resource
    ISSN: 2296-7745
    URL: Article
    URL: Article
    DOI: 10.3389/fmars.2021.795028
    DOI: 10.3389/fmars.2021.795028.s001
    Language: Unknown
    Publisher: Frontiers Media SA
    Publication Date: 2021
    detail.hit.zdb_id: 2757748-X
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