Foraminiferal test abnormalities in the western Baltic Sea

Abnormal tests were commonly found in recent benthic foraminiferal assemblages in two fjords of the Kiel Bay, the western Baltic Sea. We assessed 18 different types of abnormalities, which were classified into five groups: chamber, apertural, umbilical, coiling and test abnormalities. In both fjords, test abnormalities are over-represented in Ammonia beccarii and under-represented in Elphidium excavatum subspecies compared to their average proportions in the living assemblages. We found two species-specific abnormality types that occurred only in Ammonia beccarii: a bulla-like chamber covering the umbilicus and spiroconvex tests. In the outer Kiel and Flensburg Fjords, the highest frequencies of abnormal tests were associated with occasional salt-rich, bottom-water inflows from the Belt Sea. Based on the predominance of megalospheric specimens of living foraminifera, it is suggested that coincidence of salinity changes with a reproduction period might be harmful, especially for young individuals, leading to development of abnormal tests. On the other hand, pollution by heavy metals led to higher percentages of abnormal tests in the inner parts of both fjords. Our data show different relationships between abnormal tests and heavy metals in both fjords due to different hydrographical conditions. Tests of Ammonia beccarii found in the Gelting Bay, the Flensburg Fjord, showed traces of dissolution and development of double tests. Such specific abnormal tests mirror the peculiar environmental setting characterized by changes in salinity and enhanced sediment redeposition. It is concluded that abnormal tests as an indicator of environmental pollution have to be used cautiously in areas with strong environmental instability

Foraminiferal response to environmental changes in Kiel Fjord, SW Baltic Sea

The living benthic foraminiferal assemblages in Kiel Fjord (SW Baltic Sea) were investigated in the years 2005 and 2006. The faunal studies were accomplished by geochemical analyses of surface sediments. In general, sediment pollution by copper, zinc, tin and lead is assessed as moderate in comparison with levels reported from other areas of the Baltic Sea. However, the inner Kiel Fjord is still exposed to a high load of metals and organic matter due to enhanced accumulation of fine-grained sediments in conjunction with potential pollution sources as shipyards, harbours and intensive traffic. The results of our survey show that the dominant environmental forcing of benthic foraminifera is nutrients availability coupled with human impact. A comparison with faunal data from the 1960s reveals apparent changes in species composition and population densities. The stress-tolerant species Ammonia beccarii invaded Kiel Fjord. Ammotium cassis had disappeared that reflects apparently the changes in salinity over the last 10 years. These changes in foraminiferal community and a significant increase of test abnormalities indicate an intensified environmental stress since the 1960s

Benthische Foraminiferen und Umweltveränderungen in der SW Ostsee

Benthic foraminifera were tested as proxies of the environmental change in Kiel and Flensburg Fjords of the Kiel Bight. Foraminiferal assemblages of entire Flensburg Fjord were surveyed for the first time and showed five assemblages mainly controlled by food availability. In both fjords the significant changes in species composition were observed since the middle of the last century: disappearance of the arenaceous species Ammotium cassis and invasion of calcareous Ammonia beccarii. These changes are associated with the generally lower intensity and frequency of major Baltic inflows since the 1960s. The distribution of foraminiferal test abnormalities revealed eighteen types of abnormal tests in both fjords. The highest abnormality frequencies were observed in the outer parts of the fjords facing salt-water inflows. In the inner fjords elevated levels of heavy metals apparently led to higher percentages of abnormalities. A conceptual model depicting the relationship between salinity tolerance of foraminifera and the development of test abnormalities indicates that abnormalities cannot be used exclusively as pollution indicators.Die vorliegende Arbeit hat zum Ziel, die Foraminiferen als Proxies der rezenten Umweltsveränderungen, natürliche und anthropogene, in zwei flachen Förden der Kieler Bucht (SW Ostsee) auszuwerten. Auf Grund einer mittelmäßigen Schwermetallverschmutzung wurde die Kieler Förde als Untersuchungsgebiet ausgesucht. Ein Vergleich mit historischen Daten zeigte deutliche Veränderungen in der Artenzusammensetzung und der Populationsdichte. Ammonia beccarii, eurihalin und eine sehr opportunistische, kalkschalige Art, ist in die Kieler Förde eingedrungen. Der Sandschaler Ammotium cassis ist hingegen auf Grund eines niedrigeren Salzgehalts und fehlender Sprungschicht in der Kieler Förde seit den neunziger Jahren verschwunden. Die Benthosforaminiferen-Gemeinschaften in der Flensburger Förde wurden zum ersten Mal untersucht. Die Untersuchungen lassen fünf unterschiedliche Foraminiferen-Biofazies erkennen, die hauptsächlich durch Nahrungszufuhr gesteuert werden. Ein Vergleich mit früheren Daten aus den 40er und 70er Jahren zeigte eine Abnahme von Ammotium cassis in der Flensburger Außenförde eine Acme von Ammonia beccarii in der Geltinger Bucht. Diese Veränderungen sind mit der allgemein verringerten Intensität und Häufigkeitsabnahme der Einstromerreignisse seit den sechziger Jahren in Verbindung gebracht wurden. Dabei wurde die höchste Anzahl von Foraminiferen-Schalenmissbildungen in den äußeren Teilen beider Förden beobachtet, welche dem Salzwasser-Einstrom zugewandt sind. Dagegen sind in den Innenförden die erhöhten Schwermetallbelastungen für das häufige Missbildungsvorkommen verantwortlich. Diese Betrachtungsweise erlaubt die Entwicklung eines Modells, das die Verhältnisse zwischen Salinitätstoleranz und Entwicklung der Foraminiferenschalenmissbildungen beschreibt. Dieses Modell zeigt, dass man die Schalenmissbildungen als exklusive Verschmutzungsindikatoren nicht benutzen kann

The benthic foraminiferal community in a naturally CO2-rich coastal habitat in the southwestern Baltic Sea

It 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

Tracing winter temperatures over the last two millennia using a north-east Atlantic coastal record

We 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&thinsp;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&thinsp;°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&thinsp;BCE–450&thinsp;CE), variable BWT during the Dark Ages ( ∼ 450–850&thinsp;CE), positive BWT anomalies during the Viking Age/Medieval Climate Anomaly ( ∼ 850–1350&thinsp;CE) and a long-term cooling with distinct multidecadal variability during the Little Ice Age ( ∼ 1350–1850&thinsp;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

Recent invasion of the foraminifer Nonionella stella Cushman & Moyer, 1930 in northern European waters: evidence from the Skagerrak and its fjords

The eastern Pacific benthic foraminifer Nonionella stella Cushman & Moyer, 1930 was recorded for the first time in the Skagerrak (North Sea) and its fjords. In this short note we evaluate its migration, considering both dispersal by propagules and ship ballast tanks. We suggest that the predominantly southward surface currents along the western European seaboard and Morocco would impede a wide-range dispersal of N. stella propagules and hypothesize transportation by ship ballast tanks as the possible vector of N. stella immigration into northern European seas

Latest Quaternary palaeoceanographic change in the eastern North Atlantic based upon a dinoflagellate cyst event ecostratigraphy

AbstractThe analyses of dinoflagellate cyst records, from the latest Quaternary sediments recovered from DSDP Core 610A taken on the Feni Ridge in the southern Rockall Trough, and part of core MD01-2461 on the continental margin of the Porcupine Seabight in the eastern North Atlantic Ocean, has provided evidence for significant oceanographic change encompassing the Last Glacial Maximum (LGM) and part of the Holocene. This together with other published records has led to a regional evaluation of oceanographic change in the eastern North Atlantic over the past 68 ka, based upon a distinctive dinoflagellate event ecostratigraphy. These changes reflect changes in the surface waters of the North Atlantic Current (NAC), and perhaps the deeper thermohaline Atlantic Meridional Overturning Circulation (AMOC), driving fundamental regime changes within the phytoplanktonic communities. Three distinctive dinoflagellate cyst associations based upon both factor and cluster analyses have been recognised. Associations characterised by Bitectatodinium tepikiense (between 61.1 ± 6.2 to 13.4 ± 1.1 ka BP), Nematosphaeropsis labyrinthus (between 10.5 ± 0.3 and 11.45 ± 0.8 ka. BP), and the cyst of Protoceratium reticulatum (between 8.5 ± 0.9 and 5.2 ± 1.3 ka. BP) indicate major change within the eastern North Atlantic oceanography. The transitions between these changes occur over a relatively short time span (c.1.5 ka), given our sampling resolution, and have the potential to be incorporated into an event stratigraphy through the latest Quaternary as recommended by the INTIMATE (INTegrating Ice core, MArine and TErrestrial records) group. The inclusion of a dinoflagellate cyst event stratigraphy would highlight changes within the phytoplankton of the North Atlantic Ocean as a fully glacial world changed to our present interglacial

Coastal primary productivity changes over the last millennium: a case study from the Skagerrak (North Sea)

A 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  ∼ &thinsp;CE&thinsp;900–1700 and (ii) a high productivity at  ∼ &thinsp;CE&thinsp;1700–present. During  ∼ &thinsp;CE&thinsp;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  ∼ &thinsp;CE&thinsp;1450. The following lower and more variable temperature period at  ∼ &thinsp;CE&thinsp;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  ∼ &thinsp;CE&thinsp;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  ∼ &thinsp;CE&thinsp;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

Molecular identification of Ammonia and Elphidium species (Foraminifera, Rotaliida) from the Kiel Fjord (SW Baltic Sea) with rDNA sequences

Ammonia and Elphidium collected in the Kiel Fjord for the present study were first identified on morphological bases as Ammonia beccarii (Linne´, 1758) and Elphidium excavatum (Terquem, 1876). Phylogenetic analyses based on partial SSU rDNA and LSU rDNA sequences show that Ammonia specimens sampled in the Kiel Fjord belong to the phylotype T6, which has a disjunct distribution (Wadden and Baltic Seas/China and Japan) and has been identified as Ammonia aomoriensis (Asano, 1951). Partial SSU rDNA sequence analyses indicate that Elphidium specimens from the Kiel Fjord belong to the clade E. excavatum, confirming the morphological identification. This clade can be further divided in three subclades. Kiel Fjord Elphidium belong to two of these subclades and were identified morphologically as the subspecies E. excavatum excavatum (Terquem, 1876) and E. e. clavatum Cushman, 1930