| 31. |
- Choquel, Constance, et al.
(författare)
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3D morphological variability in foraminifera unravel environmental changes in the Baltic Sea entrance over the last 200 years
- 2023
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Ingår i: Frontiers in Earth Science. - 2296-6463. ; 11
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Tidskriftsartikel (refereegranskat)abstract
- Human activities in coastal areas have intensified over the last 200 years, impacting also high-latitude regions such as the Baltic Sea. Benthic foraminifera, protists often with calcite shells (tests), are typically well preserved in marine sediments and known to record past bottom-water conditions. Morphological analyses of marine shells acquired by microcomputed tomography (µCT) have made significant progress toward a better understanding of recent environmental changes. However, limited access to data processing and a lack of guidelines persist when using open-source software adaptable to different microfossil shapes. This study provides a post-data routine to analyze the entire test parameters: average thickness, calcite volume, calcite surface area, number of pores, pore density, and calcite surface area/volume ratio. A case study was used to illustrate this method: 3D time series (i.e., 4D) of Elphidium clavatum specimens recording environmental conditions in the Baltic Sea entrance from the period early industrial (the 1800s) to present-day (the 2010 s). Long-term morphological trends in the foraminiferal record revealed that modern specimens have ∼28% thinner tests and ∼91% more pores than their historic counterparts. However, morphological variability between specimens and the BFAR (specimens cm−2 yr−1) in E. clavatum were not always synchronous. While the BFAR remained unchanged, morphological variability was linked to natural environmental fluctuations in the early industrial period and the consequences of anthropogenic climate change in the 21st century. During the period 1940–2000 s, the variations in BFAR were synchronous with morphological variability, revealing both the effects of the increase in human activities and major hydrographic changes. Finally, our interpretations, based on E. clavatum morphological variations, highlight environmental changes in the Baltic Sea area, supporting those documented by the foraminiferal assemblages.
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| 32. |
- Choquel, Constance, et al.
(författare)
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Denitrification by benthic foraminifera and their contribution to N-loss from a fjord environment
- 2021
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Ingår i: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 18:1, s. 327-341
-
Tidskriftsartikel (refereegranskat)abstract
- Oxygen and nitrate availabilities impact the marine nitrogen cycle at a range of spatial and temporal scales. Here, we demonstrate the impact of denitrifying foraminifera on the nitrogen cycle at two oxygen and nitrate contrasting stations in a fjord environment (Gullmar Fjord, Sweden). Denitrification by benthic foraminifera was determined through the combination of specific density counting per microhabitat and specific nitrate respiration rates obtained through incubation experiments using N2O microsensors. Benthic nitrate removal was calculated from submillimeter chemical gradients extracted from 2D porewater images of the porewater nitrate concentration. These were acquired by combining the DET technique (diffusive equilibrium in thin film) with chemical colorimetry and hyperspectral imagery. Sediments with high nitrate concentrations in the porewater and oxygenated overlying water were dominated by the non-indigenous species (NIS) Nonionella sp. T1. Denitrification by this species could account for 50 %-100 % of the nitrate loss estimated from the nitrate gradients. In contrast sediments below hypoxic bottom waters had low inventories of porewater nitrate, and denitrifying foraminifera were rare. Their contribution to benthic nitrate removal was negligible (< 5 %). Our study showed that benthic foraminifera can be a major contributor to nitrogen mitigation in oxic coastal ecosystems and should be included in ecological and diagenetic models aiming to understand biogeochemical cycles coupled to nitrogen.
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| 33. |
- Darling, Kate F., et al.
(författare)
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The genetic diversity, phylogeography and morphology of Elphidiidae (Foraminifera) in the Northeast Atlantic
- 2016
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Ingår i: Marine Micropaleontology. - : Elsevier BV. - 0377-8398. ; 129, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- Genetic characterisation (SSU rRNA genotyping) and Scanning Electron Microscope (SEM) imaging of individual tests were used in tandem to determine the modern species richness of the foraminiferal family Elphidiidae (Elphidium, Haynesina and related genera) across the Northeast Atlantic shelf biomes. Specimens were collected at 25 locations from the High Arctic to Iberia, and a total of 1013 individual specimens were successfully SEM imaged and genotyped. Phylogenetic analyses were carried out in combination with 28 other elphidiid sequences from GenBank and seventeen distinct elphidiid genetic types were identified within the sample set, seven being sequenced for the first time. Genetic types cluster into seven main clades which largely represent their general morphological character. Differences between genetic types at the genetic, morphological and biogeographic levels are indicative of species level distinction. Their biogeographic distributions, in combination with elphidiid SSU sequences from GenBank and high resolution images from the literature show that each of them exhibits species-specific rather than clade-specific biogeographies. Due to taxonomic uncertainty and divergent taxonomic concepts between schools, we believe that morphospecies names should not be placed onto molecular phylogenies unless both the morphology and genetic type have been linked to the formally named holotype, or equivalent. Based on strict morphological criteria, we advocate using only a three-stage approach to taxonomy for practical application in micropalaeontological studies. It comprises genotyping, the production of a formal morphological description of the SEM images associated with the genetic type and then the allocation of the most appropriate taxonomic name by comparison with the formal type description. Using this approach, we were able to apply taxonomic names to fifteen genetic types. One of the remaining two may be potentially cryptic, and one is undescribed in the literature. In general, the phylogeographic distribution is in agreement with our knowledge of the ecology and biogeographical distribution of the corresponding morphospecies, highlighting the generally robust taxonomic framework of the Elphidiidae in time and space.
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| 34. |
- Filipsson, Helena L., 1973, et al.
(författare)
-
A 200-year environmental record of a low-oxygen fjord, Sweden, elucidated by benthic foraminifera, sediment characteristics and hydrographic data
- 2004
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Ingår i: Journal of Foraminiferal Research. - 0096-1191. ; 34:4, s. 277-293
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Tidskriftsartikel (refereegranskat)abstract
- In this study, we have detailed the benthic environment of a sill fjord on the Swedish west coast, which is characterized by brackish conditions, intermittent water exchanges, and periodic low oxygen. We have used three important tools-benthic foraminifera, sediment characteristics, and historical records of hydrographic data. Periods of low oxygen have resulted in sequences of laminated sediments in the fjord. The foraminiferal fauna present in the fjord is of low diversity and low abundance, mostly Elphidium species-an assemblage that has dominated the foraminiferal fauna for at least 170 years. During this time period, however, there have been events when normal marine species have been introduced, or foraminiferal abundance and faunal diversity have suddenly increased. These events are linked to short sequences of homogenous sediments within the laminated sequences that, in turn, suggest more oxic conditions. Since the late 1940s, we have a more-or-less continuous salinity record from the fjord, the product of an instrumental monitoring program. This record has been used, together with the foraminiferal distribution and sediment characteristics, to reconstruct the salinity variations that occurred prior to the instrumental monitoring program. The salinity in the fjord has alternated between periods of low salinity (26-28.5%), which correspond with non-laminated sediments, and periods of higher salinity (>28.5%), corresponding with laminated sequences. Despite a general low abundance of foraminiferal fauna, there was a significantly higher diversity during deposition of laminated sequences than non-laminated sequences. In the deepest part of the record, corresponding to the late eighteenth and early nineteenth century, a different fauna occurs, where species in addition to Elphidium occur, suggesting generally higher salinities (29-31).
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| 35. |
- Filipsson, Helena L., 1973, et al.
(författare)
-
A major change in the phytoplankton of a Swedish sill fjord - A consequence of engineering work?
- 2005
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Ingår i: Estuarine Coastal and Shelf Science. - : Elsevier BV. - 0272-7714. ; 63:4, s. 551-560
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Tidskriftsartikel (refereegranskat)abstract
- A major phytoplankton change occurred during the late 1930s and early 1940s in Koljo Fjord, a sill fjord on the Swedish west coast. Dinoflagellate cyst concentrations increased tenfold over a short period of time, front hundreds of cysts per gram sediment to thousands; and the species composition of both dinoflagellate cysts and diatoms changed markedly. These changes took place during a period of extensive engineering work at the entrance to the fjord from the Skagerrak. At this time, the entire passage was straightened, a new channel was built in a previously shallow area, and the old connection was closed. This study investigates whether this engineering work could have sufficiently altered the surface-water circulation to bring about the change in the phytoplankton composition. Several mechanisms are explored by which the construction could have influenced the phytoplankton in the fjord. The primary mechanism is probably increased efficiency of tidal-generated surface-water exchange in the fjord, resulting in a larger transport of surface water from the Skagerrak and consequently a changed surface-water environment. This Study highlights how engineering work can have a Substantial impact on the local and regional marine environment, a factor that must not be overlooked in environmental planning. (c) 2005 Elsevier Ltd. All rights reserved.
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| 36. |
- Filipsson, Helena L., 1973, et al.
(författare)
-
Climate variations, an overlooked factor influencing the recent marine environment. An example from Gullmar Fjord, Sweden, illustrated by benthic foraminifera and hydrographic data
- 2004
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Ingår i: Estuaries. - 0160-8347. ; 27:5, s. 867-881
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Tidskriftsartikel (refereegranskat)abstract
- Like most sill fjords, Gullmar Fjord on the Swedish west coast, is subject to periods of stagnation. Deep water is usually renewed annually, but since the late 1970s several low-oxygen events have been documented in the deepest part of the fjord. These events occurred during a time when the North Atlantic Oscillation (NAO) was in a highly positive phase. We investigated how the benthic environment, in the deepest part of the fjord, has varied during the 20th century, using benthic foraminifera. and an extensive history of instrumental hydrographic data. The foraminifera have undergone one major faunal change and two minor modifications during this time. The major faunal change occurred in the late 1970s to early 1980s, when the common Skagerrak-Kattegat fauna was replaced by one dominated by the opportunistic, low-oxygen-tolerant species, Stainforthia fusiformis. This major faunal change appears to be related to the severe low-oxygen event in 1979-1980. In the latter part of the 1990s the fauna changed again; the concentration of S. fusiformis was still high, but other low-oxygen-tolerant species also became important. This minor faunal modification occurred in connection with the 2-yr stagnation period between 1996 and 1998 when a low-oxygen event evolved, the most severe recorded in Gullmar Fjord. Between 1930 and 1980, there was little faunal variation, and a stable fjord environment is indicated. During this time, negative NAO indexes dominated and climate was more continental, with an increase in winds from the northeast and east. In connection with a climate transition indicated by the NAO index switching from positive to negative, a minor faunal change occurred in the late 1920s to early 1930s: the concentration of the Skagerrak-Kattegat fauna increased markedly in the fjord. The fauna characterizing the positive NAO phase between 1900 and the late 1920s is very different from the present positive NAO fauna. The foraminiferal record laid down between approximately 1914 and 2001 indicates that between 1930 and 1980 Gullmar Fjord was a stable fjord environment. During the last 20 yr, it experienced conditions that were more fluctuating and changing. For the most part, changes in the foraminiferal fauna are caused by changes in the deep-water renewal, their extent and frequency, which in turn are caused by climatic oscillations.
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| 37. |
- Filipsson, Helena L., et al.
(författare)
-
Geochemical composition of Baltic benthic foraminifera collected and cultured over a large salinity gradient.
- 2017
-
Konferensbidrag (refereegranskat)abstract
- Some of the most significant challenges in paleoclimate research arise from the need to both understand and reduce the uncertainty associated with proxies for climate reconstructions. These challenges were further highlighted in connection with the IODP Exp.347 Baltic Sea Paleoenvironment. We have investigated temperature and salinity proxies through a combination of field-and culture-based benthic foraminiferal samplesfrom the Baltic(sal. 14)-Kattegat(sal. 32), together with genetic characterization. Two long-term experiments at twotemperatures and three salinities were performed. We present foraminiferal assemblage,trace element (Mg/Ca, Ba/Ca, Mn/Ca),and stable O and C isotope results from these locations, including LA-ICP-MS data from cultured specimens. Furthermore, specimens of Elphidium and Ammonia were genetically characterized; the results indicate that the same genetic type of Elphidiumis found in both salinity regimes, but that the Ammoniagenetic types differ depending on the prevailing salinity regime.
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| 38. |
- Filipsson, Helena L., 1973, et al.
(författare)
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Seasonal study of delta O-18 and delta C-13 in living (stained) benthic foraminifera from two Swedish fjords
- 2004
-
Ingår i: Marine Micropaleontology. - : Elsevier BV. - 0377-8398. ; 53:1-2, s. 159-172
-
Tidskriftsartikel (refereegranskat)abstract
- In a previous 16-month seasonal study on living (stained) benthic foraminifera from two fjords on the Swedish west coast, it was reported that foraminifera proliferated in response to phytodetritus input; the strongest response came from the opportunistic species Stainforthia fusiformis. In this study, our objective was to find out if that phytodetritus input resulted in a change in the carbon isotopic composition of the foraminiferal tests. We also wanted to examine if variations in salinity and temperature (due to seasonality or deep-water exchanges) were reflected in the delta(18)O values. From S. fusiformis that were obtained from the Havstens Fjord (20 m) and the Gullmar Fjord (119 m) during the 16-month study, we developed a time series of delta(18)O and delta(13)C. After the spring blooms in the Havstens and the Gullmar Fjord, decreases of about 0.2parts per thousand to 0.3parts per thousand in the foraminiferal delta(13)C values were noted; in the Gullmar Fjord after the autumn blooms, decreases of the same order were also noted. Comparing the Havstens and the Gullmar Fjord, we found a 1parts per thousand difference in both delta(13)C and delta(18)O; we attribute this to hydrographic differences between the two fjords. Using calculated values of delta(18)O, together with the measured ones, we noticed that S. fusiformis in the Gullmar Fjord seems to calcify close to equilibrium with respect to the oxygen isotopes. During autumn, water temperatures were relatively high in the Havstens Fjord, and foraminiferal abundance in the fjord was also high after a phytodetritus input; but, the measured delta(18)O values do not reflect these higher temperatures. This apparently contradictory combination of results might be explained by a varying delta(18)O composition of the water during the year, which counterbalances the temperature effect. (C) 2004 Published by Elsevier B.V.
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| 39. |
- Filipsson, Helena L., et al.
(författare)
-
Seasonal variability of stable carbon isotopes (δ13CDIC) in the Skagerrak and the Baltic Sea : Distinguishing between mixing and biological productivity
- 2017
-
Ingår i: Palaeogeography, Palaeoclimatology, Palaeoecology. - : Elsevier BV. - 0031-0182. ; 483, s. 15-30
-
Tidskriftsartikel (refereegranskat)abstract
- We documented the annual cycle of the carbon isotopic composition of dissolved inorganic carbon (δ13CDIC) in the water columns of the Skagerrak and Baltic Sea to obtain an increased understanding of the processes involved controlling the carbon isotopic distribution in shelf seas. The lowest δ13CDIC values (-4.9‰) were found in the low-oxygen, brackish Baltic bottom water whereas the highest values (+1.8‰) were observed in the surface water of the Skagerrak during late summer. Photosynthesis drove the high δ13CDIC values (between 1.0 and 1.8‰) noted in the surface waters of both the Skagerrak and the Baltic. The δ13CDIC values below the halocline in the Baltic reflect mixing of brackish water and the more saline water from the Skagerrak, and foremost organic matter remineralization processes that release significant amounts of low-δ13C CO2. Similarly, in the stagnant fjord basins, little deep water exchange and the degradation of terrestrial and marine organic matter set the δ13C composition. Deep-water renewal in the fjord basins resulted in rapid increases of the δ13CDIC on the order of 1‰, whereas remineralization processes caused a decrease in δ13CDIC of 0.1-0.3‰ per month depending on location. The combined effects of water mixing and remineralization processes (estimated using apparent oxygen utilization (AOU) values) yielded the expression: δ13CDIC =0.032*S-0.01*AOU-0.12 for the Baltic - Skagerrak region at water depths below the halocline.
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| 40. |
- Filipsson, Helena L., 1973, et al.
(författare)
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Variations in organic carbon flux and stagnation periods during the last 2400 years in a Skagerrak fjord basin, inferred from benthic foraminiferal δ13C
- 2010
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Ingår i: Geological Society, London, Special Publications. - 0305-8719. ; 344, s. 261-270
-
Tidskriftsartikel (refereegranskat)abstract
- A well-dated high-resolution δ13C record of the last 2400 a, based on the benthic foraminifer Cassidulina laevigata, is presented for Gullmar Fjord, Sweden. The time interval covers the Roman Warm Period (RWP), the Viking Age/Medieval Warm Period (VA/MWP), the Little Ice Age (LIA) and the most recent warming. There is little variation in the δ13C record until the early Viking Age (AD 800), when the δ13C signal becomes significantly more negative and continues to decrease throughout the VA/MWP. The δ13C signal increases both at the beginning and at the end of the LIA but is marked by more negative values during the larger part of the period. Since about 1970, the δ13C values are more negative than the long-term average. This general negativity of the record may result from a higher flux of organic matter, possibly of terrestrial origin due to land-use changes together with moderate changes in stagnation periods since the VA/MWP. In most recent times, the oceanic Suess effect together with increased number of extended stagnation periods are probably the main causes of the shift towards more negative δ13C values.
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