12 research outputs found
The benthic foraminiferal community in a naturally CO2-rich coastal habitat in the southwestern Baltic Sea
No full textIt is expected that the calcification of foraminifera will be negatively affected by the ongoing acidification of the oceans. Compared to the open oceans, these organisms are subjected to much more adverse carbonate system conditions in coastal and estuarine environments such as the southwestern Baltic Sea, where benthic foraminifera are abundant. This study documents the seasonal changes of carbonate chemistry and the ensuing response of the foraminiferal community with bi-monthly resolution in Flensburg Fjord. In comparison to the surface pCO2, which is close to equilibrium with the atmosphere, we observed large seasonal fluctuations of pCO2 in the bottom and sediment pore waters. The sediment pore water pCO2 was constantly high during the entire year ranging from 1244 to 3324 μatm. Nevertheless, in contrast to the bottom water, sediment pore water was slightly supersaturated with respect to calcite as consequence of higher alkalinity (AT) for the most time of the year. Foraminiferal assemblages were dominated by two calcareous species, Ammonia aomoriensis and Elphidium incertum, and the agglutinated Ammotium cassis. The one year-cycle was characterized by seasonal community shifts. Our results revealed that there is no dynamic response of foraminiferal population density and diversity to elevated sediment pore water pCO2. Surprisingly, the fluctuations of sediment pore water undersaturation (Ωcalc) co-vary with the population densities of living Ammonia aomoriensis. Further, we observed that most of the tests of living calcifying specimens were intact. Only Ammonia aomorienis showed dissolution and recalcification structures on the tests, especially at undersaturated conditions. Therefore, the benthic community is subjected to constantly high pCO2 and tolerates elevated levels as long as sediment pore water remains supersaturated. Model calculations inferred that increasing atmospheric CO2 concentrations will finally lead to a perennial undersaturation in sediment pore waters. Whereas benthic foraminifera indeed may cope with a high sediment pore water pCO2, the steady undersaturation of sediment pore waters would likely cause a significant higher mortality of the dominating Ammonia aomoriensis. This shift may eventually lead to changes in the benthic foraminiferal communities in Flensburg Fjord, as well as in other regions experiencing naturally undersaturated Ωcalc levels
Multi-proxy study on two sediment cores in western and central Skagerrak
No full textWe present results from two sediment cores from the central (EMB046/20-3GC) and western (EMB046/10-4GC) Skagerrak. Both cores were dated by Hg pollution records and AMS 14C and analysed for palaeoproductivity proxies such as total organic carbon, δ13C, total planktonic foraminifera, benthic foraminifera (total assemblages as well as abundance of Brizalina skagerrakensis and other palaeoproductivity taxa) and palaeothermometers such as Mg/Ca and δ18O. Our results reveal two periods with changes in productivity in the Skagerrak region: i) a moderate productivity at ~ CE 900 – 1700 and ii) a high productivity at ~ CE 1700 – present
The Little Ice Age: evidence from a sediment record in Gullmar Fjord, Swedish west coast
No full textWe discuss the climatic and environmental changes during the last millennium in NE Europe based on a ca. 8-m long high-resolved and well-dated marine sediment record from the deepest basin of Gullmar Fjord (SW Sweden). According to the 210Pb- and 14C-datings, the record includes the period of the late Holocene characterised by anomalously cold summers and well-known as the Little Ice Age (LIA). Using benthic foraminiferal stratigraphy, lithology, bulk sediment geochemistry and stable carbon isotopes we reconstruct various phases of the cold period, identify its timing in the study area and discuss the land–sea interactions occurring during that time. The onset of the LIA is indicated by an increase in cold-water foraminiferal species Adercotryma glomerata at ~ 1350 AD The first phase of the LIA was characterised by a stormy climate and higher productivity, which is indicated by a foraminiferal unit of Nonionella iridea and Cassidulina laevigata. Maximum abundances of N. iridea probably mirror a short and abrupt warming event at ~ 1600 AD. It is likely that due to land use changes in the second part of the LIA there was an increased input of terrestrial organic matter to the fjord, which is indicated by lighter δ13C values and an increase of detritivorous and omnivorous species such as Textularia earlandi and Eggerelloides scaber. The climate deterioration during the climax of the LIA (1675–1704 AD), as suggested by the increase of agglutinated species, presence of Hyalinea balthica, and a decline of N. iridea may have driven the decline in primary productivity during this time period
The Little Ice Age: evidence from a sediment record in Gullmar Fjord, Swedish west coast [Elektronisk resurs]
No full textWe discuss the climatic and environmental changes during the last millennium in NE Europe based on a ca. 8-m long high-resolved and well-dated marine sediment record from the deepest basin of Gullmar Fjord (SW Sweden). According to the Pb-210- and C-14-datings, the record includes the period of the late Holocene characterised by anomalously cold summers and well-known as the Little Ice Age (LIA). Using benthic foraminiferal stratigraphy, lithology, bulk sediment geochemistry and stable carbon isotopes we reconstruct various phases of the cold period, identify its timing in the study area and discuss the land-sea interactions occurring during that time. The onset of the LIA is indicated by an increase in cold-water foraminiferal species Adercotryma glomerata at similar to 1350 AD The first phase of the LIA was characterised by a stormy climate and higher productivity, which is indicated by a foraminiferal unit of Nonionella iridea and Cassidulina laevigata. Maximum abundances of N. iridea probably mirror a short and abrupt warming event at similar to 1600 AD. It is likely that due to land use changes in the second part of the LIA there was an increased input of terrestrial organic matter to the fjord, which is indicated by lighter delta C-13 values and an increase of detritivorous and omnivorous species such as Textularia earlandi and Eggerelloides scaber. The climate deterioration during the climax of the LIA (1675-1704 AD), as suggested by the increase of agglutinated species, presence of Hyalinea balthica, and a decline of N. iridea may have driven the decline in primary productivity during this time period
Tracing winter temperatures over the last two millennia using a north-east Atlantic coastal record
No full textWe present 2500 years of reconstructed bottom water temperatures (BWT) using
a fjord sediment archive from the north-east Atlantic region. The BWT
represent winter conditions due to the fjord hydrography and the associated
timing and frequency of bottom water renewals. The study is based on a ca.
8 m long sediment core from Gullmar Fjord (Sweden), which was dated by
210Pb and AMS 14C and analysed for stable oxygen isotopes
(δ18O) measured on shallow infaunal benthic foraminiferal species
Cassidulina laevigata d'Orbigny 1826. The BWT, calculated using the
palaeotemperature equation from McCorkle et al. (1997), range between 2.7 and
7.8 °C and are within the annual temperature variability that has
been instrumentally recorded in the deep fjord basin since the 1890s. The
record demonstrates a warming during the Roman Warm Period ( ∼ 350 BCE–450 CE), variable BWT during the Dark Ages ( ∼ 450–850 CE),
positive BWT anomalies during the Viking Age/Medieval Climate Anomaly ( ∼ 850–1350 CE) and a long-term cooling with distinct multidecadal
variability during the Little Ice Age ( ∼ 1350–1850 CE). The fjord BWT
record also picks up the contemporary warming of the 20th century (presented
here until 1996), which does not stand out in the 2500-year perspective and
is of the same magnitude as the Roman Warm Period and the Medieval Climate
Anomaly.</p
Benthic foraminiferal patchiness – revisited
No full textMany benthic organisms show aggregated distribution patterns due to the spatial heterogeneity of niches or food availability. In particular, high-abundance patches of benthic foraminifera have been reported that extend from centimetres to metres in diameter in salt marshes or shallow waters. The dimensions of spatial variations of shelf or deep-sea foraminiferal abundances have not yet been identified. Therefore, we studied the distribution of Globobulimina turgida dwelling in the 0–3 cm surface sediment at 118 m water depth in the Alsbäck Deep, Gullmar Fjord, Sweden. Standing stock data from 58 randomly replicated samples depicted a log-normal distribution of G. turgida with weak evidence for an aggregated distribution on a decimetre scale. A model simulation with different patch sizes, outlines, and impedances yielded no significant correlation with the observed variability of G. turgida standing stocks. Instead, a perfect match with a random log-normal distribution of population densities was obtained. The data–model comparison revealed that foraminiferal populations in the Gullmar Fjord were not moulded by any underlying spatial structure beyond 10 cm diameter. Log-normal population densities also characterise data from contiguous, gridded, or random sample replicates reported in the literature. Here, a centimetre-scale heterogeneity was found and interpreted to be a result of asexual reproduction events and restricted mobility of juveniles. Standing stocks of G. turgida from the Alsbäck Deep temporal data series from 1994 to 2021 showed two distinct cohorts of samples of either high or low densities. These cohorts are considered to represent two distinct ecological settings: hypoxic and well-ventilated conditions in the Gullmar Fjord. Environmental forcing is therefore considered to impact the population structure of benthic foraminifera rather than their reproduction dynamics
Coastal primary productivity changes over the last millennium: a case study from the Skagerrak (North Sea)
No full textA comprehensive multi-proxy study on two sediment cores from the western and
central Skagerrak was performed in order to detect the variability and causes
of marine primary productivity changes in the investigated region over the
last 1100 years. The cores were dated by Hg pollution records and AMS
14C dating and analysed for palaeoproductivity proxies such as total
organic carbon, δ13C, total planktonic foraminifera, benthic
foraminifera (total assemblages as well as abundance of Brizalina
skagerrakensis and other palaeoproductivity taxa) and palaeothermometers
such as Mg∕Ca and δ18O. Our results reveal two periods with changes
in productivity in the Skagerrak region: (i) a moderate productivity at
∼  CE 900–1700 and (ii) a high productivity at ∼  CE 1700–present. During ∼  CE 900–1700, moderate
productivity was likely driven by the nutrients transported with the warm
Atlantic water inflow associated with a tendency for a persistent positive
NAO phase during the warm climate of the Medieval Climate Anomaly, which
continues into the LIA until ∼  CE 1450. The following lower and
more variable temperature period at ∼  CE 1450–1700 was
likely caused by a reduced contribution of warm Atlantic water, but stronger
deep-water renewal, due to a generally more negative NAO phase and a shift to
the more variable and generally cooler climate conditions of the Little Ice
Age. The productivity and fluxes of organic matter to the seafloor did not
correspond to the temperature and salinity changes recorded in the benthic
Melonis barleeanus shells. For the period from ∼  CE 1700 to the
present day, our data point to an increased nutrient content in the Skagerrak
waters. This increased nutrient content was likely caused by enhanced inflow
of warm Atlantic water, increased Baltic outflow, intensified river runoff,
and enhanced human impact through agricultural expansion and industrial
development. Intensified human impact likely increased nutrient transport to
the Skagerrak and caused changes in the oceanic carbon isotope budget, known
as the Suess effect, which is clearly visible in our records as a negative
shift in δ13C values from ∼  CE 1800. In addition, a
high appearance of S. fusiformis during the last 70 years at both
studied locations suggests increased decaying organic matter at the sea floor
after episodes of enhanced primary production.</p
Tracking fjord biodiversity through space and time: exploring methods to define reference conditions with benthic foraminifera
No full textThis thesis aims to develop new methods to establish in situ reference conditions in nearshore marine environments, using morphospecies and sedimentary environmental DNA (eDNA and sedaDNA) metabarcoding analysis of the benthic foraminifera assemblages. The study focuses on well-studied fjord systems along the Skagerrak coast, to address “the estuarine quality paradox”, by delineating the anthropogenically produced environmental stress from that which is naturally a feature of transitional environments. Ecological Quality Status (EcoQs) assessment in environments that are most proximal to, and therefore disproportionally effected by, human activities is essential to preserve ecosystem services and mitigate further damage. Some key fundings of this thesis show that a) SedaDNA preservation is increased in low-oxygen environments that lack bioturbation, meaning this methodology could be particularly effective in areas effected by both natural and human enduced eutrophication B) Diversity indices calculated from morpho-taxonomic and genetic assemblages show coherent response to both contemporary and historical variation in environmental conditions C) SedaDNA analysis can help to resolve the ecological preferences of otherwise under studied taxonomic groups, such as monothalamids. Taxa consistently found to be associated with polluted, or stressed environmental conditions could represent novel indicator species for future biomonitoring studies.
The ultimate goal of this thesis is to demonstrate that by integrating benthic foraminiferal morphospecies and genetic diversity, sensitivity and multimeric indices for use in biomonitoring; benthic foraminifera hold a high potential as a ‘biological quality element’ (BQE) in anoxic or polluted coastal environments, in which traditional monitoring strategies such as macrofaunal community analysis are not applicable
The influence of three common antibiotics on coastal benthic foraminifera: implications for culture experiments and biomonitoring
No full textSynthetic antibiotics are medicinal substances crucial for human and animal health and welfare. Recently they have been expansively used in the food industry for reducing bacterial infections in livestock, poultry, and aquaculture. Due to their extensive use, antibiotics are increasingly accumulating in coastal marine ecosystems and cause damage to marine organisms. In this study we investigated the influence of antibiotics on benthic foraminifera, which are widespread marine protists. Foraminifera are often used as bioindicators to define the health state of coastal ecosystems. To gain deeper insights into the ecology of foraminifera and enhance their use as bioindicators, numerous studies have conducted laboratory experiments, with some employing antibiotics to prevent bacterial infections in the cultures. However, for decades it remained unresolved whether antibiotics have either a negative or a positive effect on foraminifera. In this study we tested the influence of three commonly used antibiotics (ampicillin, chloramphenicol, and tetracycline) as well as a mixture of the three on nutrient uptake of two benthic foraminifera, temperate fjord species Nonionella sp. T1 and large tropical species Heterostegina depressa. Our results showed that tetracycline present alone or in mixture has the most negative influence on the nutrition uptake of foraminifera, and under light conditions it may completely inactivate foraminiferal activity. Ampicillin showed a less negative impact, likely caused by a hydrolysis of this drug in seawater over days. Finally, chloramphenicol reduced the nutrient uptake of the symbiont-bearing H. depressa but not that of Nonionella sp. T1, which indicates that this antibiotic exerts a species-specific effect. However, given that the applied antibiotic concentrations were high following the supplier's recommendation for laboratory cultures, an extrapolation of these results to antibiotic concentrations occurring in coastal waters is difficult.</p
Coastal primary productivity changes over the last millennium: a case study from the Skagerrak (North Sea)
No full textAbstract. A comprehensive multi-proxy study on two sediment cores from western and central Skagerrak was performed in order to detect the variability and causes of marine primary productivity changes in the investigated region over the last 1100 years. The cores were dated by Hg pollution records and AMS 14C dating and analysed for palaeoproductivity proxies such as total organic carbon, δ13C, total planktonic foraminifera, benthic foraminifera (total as well as abundance of Brizalina skagerrakensis and other palaeoproductivity taxa) and palaeothermometers such as Mg / Ca and δ18O. Our results reveal three periods with changes in productivity in the Skagerrak region: (i) moderate productivity at ~ CE 900–1200; (ii) low to moderate productivity at ~ CE 1200–1600 and (iii) high productivity at ~ CE 1600–present. During ~ CE 900–1200, moderate productivity was likely driven by the nutrients transported with the warm Atlantic water inflow associated with a tendency for a persistent positive NAO phase during the warm climate of the Medieval Climate Anomaly. The following low productivity period at ~ CE 1200–1600 was likely caused by a lower contribution of nutrient-rich Atlantic water due to a generally more negative NAO phase and a shift to the more variable and generally cooler climate conditions of the Little Ice Age. At that time the nutrient supply was largely sustained by the Baltic Sea outflow and river runoff associated with land-use changes. Since ~ CE 1600 towards present day our data point to an increased nutrient content in the Skagerrak waters. This increased nutrient content was likely caused by enhanced inflow of warm Atlantic water, increased Baltic outflow, intensified river runoff and enhanced human impact through agriculture expansion and industrial development. Intensified human impact likely increased nutrient transport to the Skagerrak and caused changes in the oceanic carbon isotope budget, known as the Suess effect, which is clearly visible in our records as a negative shift in δ13C values from ~ CE 1750. In addition, a higher benthic foraminiferal Mn / Ca suggests slightly decreased bottom water oxygen conditions between ~ CE 1050 and 1400 in the central Skagerrak and in the last 70 years at both studied locations.
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