Open Basin Research Articles

Decadal shifts of coastal microphytoplankton communities in a semi-enclosed bay of NW Mediterranean Sea subjected to multiple stresses

Long-term evolution of microphytoplankton communities remains poorly studied in anthropized coastal zones submitted to multiple stressors. Here, we investigate decadal (2005–2017) microphytoplankton community changes, focusing on abundance and biovolume of major taxa related to both local abiotic conditions (rainfall rate, temperature and salinity) and regional convection events (wintering deep mixing) in the highly urbanized and semi-enclosed Toulon Bay (NW Mediterranean Sea). Results showed that persistent variations in local rainfall regime were followed by major changes in microphytoplankton community composition. Wet period (P2) (increase of wintering precipitations observed between late 2008 and early 2015) was associated to an increase of large heterotrophic dinoflagellates and disappearance of dominant diatom taxa, while dry periods (2005–2008 (P1) and 2015–2017 (P3)) promoted diatoms, microflagellates and small mixotrophic/heterotrophic dinoflagellates including potentially toxic species. Concomitance between intense deep mixing events, reported in open Ligurian Basin (particularly during winters 2005 and 2006) and higher values in the total microphytoplankton abundance and in spring diatom abundance regardless of rainfall conditions, presents this meso-scale process as the main fertilization mechanism in Toulon Bay. Although no change was detected in the chlorophyll a concentration during the 2006–2017 period, its trend was negatively correlated to the total microphytoplankton abundance. This negative relation as well as a change of size in dinoflagellates suggested a shift in the primary producer nature, from large autotrophic cells (diatoms and microflagellates) to smaller ones, driven by a runoff intensification. Finally, different communities composition were observed during both dry periods (i.e. diatoms-dominated and autotrophic microflagellate-dominated communities during P1 and P3, respectively), suggesting another environmental driver of change for phytoplankton communities of this coastal ecosystem.

Volgian–Early Berriasian Marginal Filter in the West Siberian Marine Basin and Its Influence on Sediment Distribution

The West Siberian marine basin of the Volgian–initial Berriasian ages is described. It is shown that a marginal filter (according to A. P. Lisitsyn) functioned in the basin. The main mass of terrigenous sediments was deposited within the eastern margin of the sea. The central part of the basin only received a small amount of the terrigenous material. Water area of the West Siberian Sea was 2 mln 530 thou km2; eastern marginal filter, 535 thou km2; and open epicontinental marine basin, 1 mln 994 thou km2. Depth of the Volgian Sea was 500 m. Mass of sediments in the West Siberian Sea by the end of late diagenesis was 228.4 Tt (recalculated to the anhydrous material), with sediments in the eastern marginal filter accounting for 121.7 Tt. Bioproductivity of the Volgian–Berriasian West Siberian Sea was extremely high. The mass of living matter was composed of archaea, bacteria, and protozoan unicellular eucaryotes (organic-walled), as well as organisms with the siliceous (radiolarians) and carbonate skeleton (foraminifers and others). The rock mass formed from sediments of the central deep-water part of the basin at the stage of diagenesis was 106.7 Tt (recalculated to the anhydrous material), including the mass of organic matter (OM) accounting for 15.8 Tt; mineral (siliceous and carbonate) relicts of organisms, 67.8 Tt; and allothigenic components (clay minerals and iron hydroxides), 23.1 Tt. Analysis of the composition of kerogen (polymerlipids) revealed that the amount of OM transported to sediments was 15–20 times higher than the present-day amount in rocks of the Bazhenov Formation. At the stage of early diagenesis, the OM mass in sediments was as high as 235–320 Tt (recalculated to the anhydrous material). The Bazhenov Sea represented a huge natural ecosystem favorable for the generation, reworking, and accumulation of living matter relicts. At the stage of catagenesis, unique oil-andgas resources were generated from OM masses deposited in this system.

Comparative analyses of non-marine ostracods (Crustacea) among water basins in Turkey

Total of 26, 22 and 32 sites in Konya, Antalya and West Mediterranean basins in Turkey, respectively, were sampled twice during 2017 to compare the non-marine ostracod diversity. A total of 1787 individuals belonging to 31 species were recorded from all basins. Of which, nine species are common among basins when Fabaeformiscandona fragilis is new for Turkey. High species diversity was found at middle elevational intervals. The highest and lowest Shannon diversity index values were recorded for both Konya (H = 2.19) and Antalya (H = 1.90) basins, respectively. The highest beta diversities values are encountered between closed the Konya and other open basins. Species and environmental variables composition among basins and elevational intervals showed significant differences (p < 0.05, ANOSIM). Of species, cosmopolitans (e.g., Candona neglecta, Ilyocypris bradyi, Psychrodromus olivaceus) provide an important contribution to the differences in diversities among basins and elevational intervals. According to Canonical Correspondence Analysis, elevation appeared to be the common influential variables in all basins. Results suggest that alpha diversity is under the control of local and regional factors when beta diversity is primarily affected by regional factor. Although cosmopolitan species are positive indicators, they seem to make a significant contribution to alpha and beta diversities of ostracods.

NOVEL TEMPORARY AQUATIC HABITATS AND DESERT INVERTEBRATE COMMUNITIES

Abstract The addition of desert water developments alleviates water stress for a variety of organisms and is likely necessary for some species as water availability from other isolated water sources declines with climate change. However, constructed water catchments are different structurally and do not cycle water the same way as natural sites. We assessed whether these novel habitats, the constructed catchments of the Sonoran Desert, function as ecological equivalents of the natural waters and evaluated their effects on macroinvertebrate biodiversity, community composition, and trophic function. We documented an accumulation of ammonia and less diversity and different taxa assemblages in the novel habitat. We also documented a more heterotrophic food web in the natural water basins that are more dependent on resource pulses, and a more autotrophic food web in novel habitats that are more dependent on primary production from the open catchment basin. As natural resource managers continue to add constructed waters to mitigate for climate change induced declines in water availability, organisms are more likely to encounter these novel habitats as they disperse. Consequently, by increasing the density of these novel habitats we are having a measurable effect on the types of species and trophic groups present as well as the ecosystem cycling of energy and nutrients across the desert landscape. The consequences of these shifts in invertebrate community composition and ecosystem cycling on the larger desert ecosystem is unknown.

Sletanje na Mars

More than 40 years after the first successful landing on Mars, in situ exploration of its surface continues to be a huge scientific and technological challenge. This primarily refers to Martian southern highlands, extending over a large part of its southern hemisphere, where no successful landing has been achieved so far. On the other hand, in the northern lowlands, which cover almost entire northern hemisphere, 7 successful landings have been completed. This difference is a consequence of the specific topography of the Martian surface due to the so-called global or hemispherical dichotomy of Mars, which represents a unique feature in the Solar system. Due to the difference in elevations of the surface, a spacecraft trying land on the southern highlands have a thinner atmosphere layer which can be used for dissipation of kinetic energy. Since the spacecraft from an interplanetary trajectory enter the atmosphere with hyperbolic velocities, their kinetic energy is extremely large and the ability to reduce it through interaction with the atmosphere is crucial for safe landing, especially at sites with high elevation. It is estimated that the southern highlands are billions of years older than the northern lowlands, which were exposed to strong volcanic activity in the relatively recent past. This huge difference in age is a motivation for exploration of the entire surface of Mars in order to understand its complex geological evolution. In addition, a large number of open basins, which were discovered on the southern lowlands, indicate that these regions in the past could have been covered with liquid water, which is one of the most important reasons for exploring these locations. The analysis of the seasonal and daily variations of the Martian atmosphere confirms that, it is possible to land on these high locations by using current technology, with the necessity of optimization of the conditions under which spacecraft enter the atmosphere, in order to maximize the benefits from these specificities of Mars.

Radar Sounding of Open Basin Lakes on Mars

AbstractOrbital observations of the surface of Mars indicate that ancient basins were once host to lakes that may have been depocenters of sedimentary materials, including hydrated minerals like phyllosilicates. Later volcanic and sedimentary resurfacing may have developed a stratigraphy within the basins detectable through radar sounding data from the Shallow Radar instrument. Our radar survey of 61 open basin lakes (OBLs) revealed only one plausible reflector in a single basin east of Hellas Planitia. We investigated possible factors contributing to lack of radar detections in the other basins through detailed analysis of radargrams and subsurface characteristics of OBLs. As possible hosts to previous habitable environments, OBLs on Mars are important sites for future robotic and human missions. A full understanding of the factors influencing the radar signal, as addressed here, is important for more fully characterizing the subsurface structure and geology at these locations.

Island topographies to reduce short-circuiting in stormwater detention ponds and treatment wetlands

Urban stormwater is an increasing environmental problem for cities worldwide. Many cities have turned to green infrastructure solutions, which provide water treatment and retention while also harnessing other ecosystem services. This study considered the design of detention ponds and treatment wetlands with the goal of improving hydraulic performance (specifically reducing short-circuiting) while also increasing habitat diversity. Fifty-four basin topographies, including a variety of islands and berms, were compared to an open and a traditional serpentine basin. Using scaled physical models the hydraulic performance of each design was evaluated using tracer studies to construct the residence time distribution and to visually observe the circulation pattern. In addition, the earthwork construction cost and habitat diversity index (based on the Shannon-Weaver entropy measure) were estimated at field scale. The results reveal multiple design options that improve hydraulic performance, relative to both the open and serpentine basins, and which represent a range of habit diversity and cost. General guidelines for optimal configurations are discussed.

Sedimentary architecture of the southern basin of Lake of the Woods, Minnesota and its relation to Lake Agassiz history and Holocene environmental change

AbstractLake of the Woods (LOTW) is a large, complex lake basin once occupied by glacial Lake Agassiz. High-resolution seismic-reflection profiles and cores in the shallow, open southern basin of LOTW reveal a sedimentary architecture comprising four lacustrine units separated by three low-stand unconformities. These units represent several phases of Lake Agassiz and its changing configuration. One unconformity marks the Moorhead low phase and another marks the separation of LOTW from Lake Agassiz, perhaps ~10 cal ka BP, as the level of the latter fell, but before final drainage of Agassiz. Initially, the separate Holocene lake in the southern basin was broad and shallow, sometimes marshy or dry. Shortly after 8 cal ka BP, the southern basin dried up completely, despite the progressive rise of the northern outlet of the lake due to differential isostatic uplift. The resulting hiatus is related to the well-documented mid-Holocene arid interval in central North America. A return to wetter conditions in the late Holocene caused the southern basin of LOTW to refill since about 3800 cal yr BP. Late Holocene sediments have accumulated slightly asymmetrically in the basin, possible due to continued southward transgression of the lake as a result of isostatic tilting.

Multi‐proxy reassessment of the paleolimnology of Lake Bonneville (western USA) as observed in the restricted Pilot Valley sub‐basin

ABSTRACTLate Pleistocene sediments of pluvial Lake Bonneville of the western USA represent an important archive of climate and paleolimnological processes. Geochemical, mineralogical and diatom records from the Pilot Valley sub‐basin represent a complete multi‐proxy record of the Bonneville cycle, including closed‐basin transgressive, the Bonneville flood, open‐lake and closed‐basin regressive cycles. Diatoms record pH and salinity, and vary from alkalibiontic/brackish (early transgression), alkaliphilous/fresh‐brackish (deep lake) and back to alkalibiontic/brackish (late regression) conditions. Pennate diatoms reveal passage through and back into the euphotic zone due to the penetration of light through the water column supporting an active benthos. As such, the base of the euphotic zone (∼35 m depth) can be established through time. Restriction and evaporation within the Pilot Valley arm of Lake Bonneville during times of shallow water produced very high endogenic carbonate production, an order of magnitude higher than during deep water. This is shown by age–depth relations in the core, major element and isotopic variations, and sediment mineralogy, requiring a major re‐evaluation of the position of the Bonneville flood horizon within the sediments of Pilot Valley. In summary, lacustrine sediments from restricted arms of large pluvial lakes may vary significantly from complementary records from an open basin.

Analyses of Aeromagnetic Data to Delineate Basement Structures and Reveal Buried Igneous Bodies in Kaladgi Basin, Karnataka

ABSTRACT Aeromagnetic data overcome constrain of inadequate exposures and provide signatures of bodies beneath sediment cover. Present work on analysis of aeromagnetic data over western part of Kaladgi basin provided insight into the basement structures and their role in basin evolution. In the study area, the NW-SE and NE-SW are the major trends of magnetic lineament followed by E-W and N-S trends. Archean to Paleoproterozoic basement is manifested by two structural zones, NW-SE trends related to major lineaments within the basement and the NE-SW trends presumed intra-basinal fault systems which controlled the local depressions. The basin configuration deduced from depth to basement show that the Kaladgi basin is an open deep basin and divided into several sub-basins, separated by fault-controlled NE-SW and NW-SE oriented basement ridges. An intriguing find in the western part are the numerous scattered smaller-scale, circular or semicircular, distinct magnetic anomalies of moderate to strong magnetic signal with strong remenance. Analyses coupled with 3D inversions in combination with sub-surface probing reveal in-homogeneities within basement gneisses and supracrustal rocks of the Kaladgi basin, Dharwar craton. 3D inversions of these circular bodies, suggest that they are apophyses of the intrusions or alternatively as younger intrusive stocks. Sub-surface probing by boreholes over circular bodies revealed leucocratic granite with porphyritic texture emplaced as intrusive within the Chitradurga metasediments. This implies that these intrusives are post-Chitradurga schist and pre Badami sediments as they have not affected the latter. However, they can be presumed to be coeval to potassic granites, which intrude the eastern part of the western Dharwar craton in southern India, until geochronological data are available.

Miocene Oceanographic Evolution Based on the Sr and Nd Isotope Record of the Central Mediterranean

AbstractThe Miocene is a key interval in the geodynamic and oceanographic evolution of the Mediterranean marking the transition from a wide open basin to the modern closed basin. We used the Sr and Nd isotope records of two Miocene carbonate successions in the Adriatic to document that the evolution of the Mediterranean Basin controlled its seawater chemistry. During the late Aquitanian (~21 Ma), a time of glaciation and sea level lowstand, increased runoff affected the Sr isotope ratios of Mediterranean waters, whereas during the Burdigalian (20.44–15.97 Ma) volcanism in the circum‐Mediterranean area mainly influenced the Sr isotopic signature. During the Langhian (15.97–13.82 Ma), a time of sea level highstand associated with the Middle Miocene Climatic Optimum, the Nd isotope values indicate that waters exchanged between the Paratethys and the Central Mediterranean. The Central Mediterranean was well connected with the Atlantic Ocean between the Langhian and the early Tortonian (15.97–11.5 Ma), but exchange of water with the Paratethys declined. In the Messinian (6.3 Ma), connections between some marginal Mediterranean basins, for example, the proto‐Adriatic basin, and the Central Mediterranean, became restricted. In this basin, the Sr isotope values fell below the global reference line, while Nd isotope ratios show a strong affinity with the Atlantic Ocean and also indicate freshwater input. We conclude that the Mediterranean Nd isotope signature differs from that in the open oceans and reflects the basin physiography, reflecting a mix of signals derived from the adjacent oceans and local signals.

OXYGEN ISOTOPIC COMPOSITION OF CONODONT APATITE IN THE EQUATORIAL EPEIRIC BELARUSSIAN BASIN (EIFELIAN)– RELATIONSHIP TO FLUCTUATING SEAWATER SALINITY AND TEMPERATURE

Conodont apatite from a shallow-marine Middle Devonian transgressive unit has been investigated in five borehole sections representative of the epicontinental Belarussian Basin located in a near-equatorial setting. The transgression is related to the onset of the late Eifelian Kacak Event, an important biotic episode recorded worldwide. The δ 18 O apatite data were acquired using the secondary ion mass spectrometry (SHRIMP) technique. The mean corrected values in the studied sections are in the range 19.8 ‰ to 20.2 ‰, significantly exceeding the values measured for late Eifelian low-latitude open marine basins. This can be explained by higher average δ 18 O seawater levels related to elevated seawater salinities in the Belarussian epeiric basin, in agreement with the presence of impoverished marine fauna. The intra-specimen δ 18 O variability, with differences ranging up to 2.6 ‰ in some specimens, can be explained by fluctuating δ 18 O seawater and, to a smaller degree, temperature variations in the Belarussian inland sea under a monsoonal climate. The present results demonstrate that local paleoclimate and epeiric paleogeography may considerably obscure the global climatic signature of the conodont apatite isotopic record.

Paleoecology and paleoenvironment of the Middle–Upper Jurassic sedimentary succession, central Saudi Arabia

Four Middle–Upper Jurassic sections from central Saudi Arabia have been investigated to evaluate microfacies types and macro-invertebrate paleocommunities and to interpret their paleoecology and paleoenvironments. The studied Jurassic successions are part of the Middle–Upper Callovian Tuwaiq Mountain Limestone and the Middle–Upper Oxfordian Hanifa Formation. Three main facies were recorded, including mud-supported microfacies, grain-supported microfacies and boundstones. A data matrix comprising 48 macrobenthic species in 35 samples collected from four sections were grouped into fifteen assemblages and one poorly fossiliferous interval by means of a Q-mode cluster analysis. The recorded macrofaunal assemblages have been subdivided into low-stress and high-stress on the basis of hydrodynamic conditions, substrate type, nutrient supply and hypoxia. The low-stress assemblages occur in (a) high-energy paleoenvironments with firm substrates; (b) high-energy shoals with unstable substrates of low cohesion and in (c) low-energy open marine environments with soft-substrates. The moderate- to high-stress assemblages occur in (a) oligotrophic environments with reduced terrigenous input in shelf lagoonal or in restricted inner ramp settings; (b) low-energy, soft substrate environments with hypoxia below the sediment–water interface; and, in (c) high-energy shoals and shelf lagoonal environments. The temporal distribution patterns of epifaunal and infaunal bivalve taxa are controlled by variations in water energy, substrate characteristics and productivity level. The reported litho- and biofacies confirmed that the Callovian Tuwaiq Mountain Limestone and the Oxfordian Hanifa Formation were deposited across wide spectrum of depositional environments, ranging from restricted lagoon to moderately deeper open marine basin, and providing the perfect conditions for macrofossils.

Integração entre medidas de controle de enchentes e o aproveitamento social do espaço urbano na bacia do rio Jacaré – município do Rio de Janeiro.

O presente trabalho teve como objetivo propor uma abordagem sistêmica referente ao manejo de águas pluviais na bacia hidrográfica do rio Jacaré, localizado no Rio de Janeiro/RJ, contemplando um reservatório de detenção off-line aberto, com área total de 16.000 m² e profundidade de 3 m, operado por gravidade, para controle de enchentes na bacia. O hidrograma de projeto foi determinado pelo método do Soil Conservation Service (SCS), para tempos de recorrência de 5, 10 e 25 anos com duração crítica equivalente ao tempo de concentração. As vazões de pico obtidas, para os tempos de recorrência avaliados, foram de 38,78 m³/s, 50,15 m³/s e 68,82 m³/s, respectivamente. O routing do reservatório, obtido através do Método Modificado de Puls, resultou em amortecimento de 86% para um tempo de recorrência de 5 anos, 71% para 10 anos e 54% para 25 anos. O reservatório proposto foi idealizado de modo a permitir usos múltiplos e a integração com o espaço urbano, a partir da adequação da bacia de deten¬ção em uma quadra de futebol de grama, além de uma área de vivência, um espaço de lazer para crianças e de exercícios para ido¬sos. Desta forma, seria possível agregar valor social à comunidade local.

LITHOLOGY AND STRATIGRAPHY OF THE CENOMANIAN/ TURONIAN BOUNDARY IN ZAGROS OROGENIC BELT EXAMPLES FROM KURDISTAN REGION, NORTHEASTERN IRAQ

Cenomanian-Turonian (C/T boundary) is globally foci of intense geological study in the most part of the world due its organic matter content. In Iraq, the representative of the boundary is defined previously as bituminous black shale and named “Gulneri Formation” which is about 2.5 meters thick. In the country, the boundary is controversial both stratigraphically and lithologically; since it is assumed that its top and base are bounded by unconformity and deposited in euxinic and small relic basin. In the present study, the previous studies are critically evaluated and many new results and new fact are documented about the formation through studying of nine sections. The new results include changing of the lithology and boundary condition (rejecting of underlying and overlying previously indicated unconformities). The lithology has amended to marl and marly limestone and the depositional basin is changed to large open basin in which Balambo and Kometan formations are deposited. Additionally, many fish remains are found in the formation. The remains are three types; the first is fish scales, which have circular shape with concentric rings and about 1 to 4 mm in diameters. The second is fish backbones (skeletons), four skeletons are found, which belong to small fish about 4 to10 cm long and 5mm to2 cm wide. The third is fish fins (pectoral fin), which are well preserved in hand specimens and have grey or brown color and consist of groves and ribs. The fish remains are evidence that a depositional environment of the Gulneri Formation was deep, large and open sea. Only the bottom of the sea was anoxic, which had preserved the organism remains that had fallen down from the surface of water and rested on the sea bottom.

The Bransfield Gravity Current

Using in situ data and laboratory experiments, we show that the circulation of the Bransfield Current (BC) around the South Shetland Islands (SSI) may be characterized in terms of a propagating buoyant gravity current. First, we describe the SSI hydrography and some drifter trajectories, paying special attention to the recirculation of the BC at the northeastern tip and northern slopes of the SSI. We observed that when the northeastward-flowing BC reaches the northeastern tip of the SSI, it recirculates around an anticyclonic mesoscale eddy that has not previously been reported in this region. Part of this recirculating water then proceeds southwest along the northern SSI shelf break as a narrow baroclinic jet and another part join the Antarctic Circumpolar Current. Consequently, the cross-slope gradients of properties strengthen, and the southern boundary of the Antarctic Circumpolar Current becomes a nearly submesoscale (~10km) front. Second, we compare the observations with buoyant gravity current laboratory experiments in an open basin setup where the SSI topographic barrier is represented by a central wall. The resulting circulation of the buoyant gravity current around the wall mirrors our in situ observations. First, a narrow buoyant gravity current flows northeastward along the southern boundary of the wall. Once the head of the buoyant gravity current reaches the tip of the wall, a recirculating anticyclonic vortex is generated, and the buoyant gravity current then proceeds westward along the north side of the wall. This circulation of the BC around the SSI as a buoyant gravity current may contribute to the fertilization of the waters around the SSI, as suggested by previously reported distributions of nutrients and phytoplankton.

Linking biochemical properties of particles to particle‐attached and free‐living bacterial community structure along the particle density gradient from freshwater to open ocean

AbstractTo test the hypothesis that particle composition has a stronger influence on the community structure of particle‐attached than free‐living bacteria, elemental (C/N, δ13C, and δ15N) and chemical composition of particles and the size‐fractionated bacterial community composition were examined along the particle density gradient from the Pearl River to the open basin in the South China Sea. Microbial communities were collected at the three size fractions of 0.2–0.8, 0.8–3, and &gt;3 µm, and the community composition was analyzed using high‐throughput sequencing of the 16S rRNA gene (V3–V4 regions). Multivariate analysis evaluating the similarities of bacterial community composition and chemical composition of particles revealed their general consistent spatial variations along the particle density gradient from freshwater to the sea basin. However, compositions of particulate organic matter were more strongly related to the free living than to the particle‐attached bacterial community composition, which was composed of relatively abundant anaerobic bacteria and those taxa preferring low‐oxygen conditions. This latter result might be caused by low‐oxygen microzones in particles. Community network models further revealed tighter interactions within the particle‐attached than in free‐living bacterial communities, suggesting that a relatively confined space in particles is more favorable for interactions within the community. These analyses indicated that particle microniche properties might be important in shaping particle‐attached community structure. In contrast, particulate organic matter compositions significantly influenced the free‐living bacterial community probably through the release of labile or semilabile organic matter from particles contributing to the bioavailability of dissolved organic carbon.

Correlation of Carbonate Strata in Gorski Kotar Area (Karst Dinarides, Croatia), An Example of Adriatic Carbonate Platform Environmental Diveristy During the Late Jurassic

Adriatic Carbonate platform environmental diveristy as observed within the carbonate strata in Gorski kotar area (Karst Dinarides, Croatia) was caused by synsedimentary tectonics when the hitherto uniform platform area was partly differentiated into two different sedimentary environments. In Jasvina zone an uninterrupted shallow-water platform succession occur, indicating shallow subtidal and peritidal environmental conditions. On the other hand, the Breze zone is characterised by the presence of deeperwater pelagic influenced carbonate succession, clearly evidencing the sunken intraplatform trough of unknown dimensions, which was possibly connected with the open basin area. Correlation of carbonate strata of the studied sections allows the reconstruction of sedimentary dynamics and events that led to such diversified environment which represent the inner part of the Adriatic Carbonate Platform.

Holocene climate change in Newfoundland reconstructed using oxygen isotope analysis of lake sediment cores

Carbonate minerals that precipitate from open-basin lakes can provide archives of past variations in the oxygen isotopic composition of precipitation (δ18Oppt). Holocene δ18Oppt records from the circum- North Atlantic region exhibit large fluctuations during times of rapid ice sheet deglaciation, followed by more stable conditions when interglacial boundary conditions were achieved. However, the timing, magnitude, and climatic controls on century to millennial-scale variations in δ18Oppt in northeastern North America are unclear principally because of a dearth of paleo-proxy data. Here we present a lacustrine sediment oxygen isotope (δ18O) record spanning 10,200 to 1200 calendar years before present (calyr BP) from Cheeseman Lake, a small, alkaline, hydrologically open lake basin located in west-central Newfoundland, Canada. Stable isotope data from regional lakes, rivers, and precipitation indicate that Cheeseman Lake water δ18O values are consistent with the isotopic composition of inflowing meteoric water. In light of the open-basin hydrology and relatively short water residence time of the lake, we interpret down-core variations in calcite oxygen isotope (δ18Ocal) values to primarily reflect changes in δ18Oppt and atmospheric temperature, although other factors such as changes in the seasonality of precipitation may be a minor influence. We conducted a series of climate sensitivity simulations with a lake hydrologic and isotope mass balance model to investigate theoretical lake water δ18O responses to climate change. Results from these experiments suggest that Cheeseman Lake δ18O values are primarily controlled by temperature and to a much lesser extent, the seasonality of precipitation. Increasing and more positive δ18Ocal values between 10,200 and 8000calyr BP are interpreted to reflect the waning influence of the Laurentide Ice Sheet on atmospheric circulation, warming temperatures, and rapidly changing surface ocean δ18O from the input of glacial meltwater into the western North Atlantic Ocean. The increasing trend is interrupted by abrupt negative δ18Ocal anomalies at 9700calyr BP, associated with a transition to colder sea surface temperatures (SSTs) in the Labrador Sea and renewed Laurentide Ice Sheet retreat, and at 8500calyr BP that coincides with a well-established cooling event in the circum-North Atlantic region. After 8000calyr BP, δ18Ocal values gradually decrease until 4300calyr BP, which reflects a cooling trend related to declining Boreal summer insolation and lower sea surface temperatures in the western North Atlantic Ocean. δ18Ocal becomes slightly more positive from 4300 to 2500calyr BP and thereafter declines to the most negative values of the late Holocene by 1200calyr BP. The middle to late-Holocene transition at ~4300calyr BP corresponds with a shift to wetter conditions in Newfoundland that is also seen in other paleo-proxy records from the region. The discordance between the Cheeseman Lake δ18Ocal record and declining insolation could in part reflect warmer temperatures or an increase (decrease) in warm (cold) season precipitation. Considering evidence from other paleo-records in Newfoundland, we suggest this transition resulted from a change in synoptic scale atmospheric circulation to a configuration similar to the positive mean state phase of the Pacific-North American pattern. Proxy evidence from Cheeseman Lake therefore supports the idea that a substantial climatic change occurred during the middle to late-Holocene transition (between ~5000 to ~4000calyr BP) in northeastern North America.

Behavioral studies on the use of open water basins by American mink (Neovison vison)

The aims of this study were to investigate whether farmed mink use swimming basins as an environmental enrichment factor and to identify layouts suitable to allow mink to perform their characteristic behavior to a large extent. Furthermore, an assessment of the water quality was intended. In 2006, the German “Order on the Protection of Animals and the Keeping of Production Animals” (German designation: Tierschutz-Nutztierhaltungsverordnung) stated mandatory husbandry requirements for fur animals for the first time in Germany. For mink, these include a water basin which is suitable for swimming. Forty American mink (Neovison vison) from a commercial mink farm were housed in 2 identically constructed free-range enclosures at the age of 13 weeks. In each of the 2 enclosures, the mink were offered 3 different water basins, which differed in shape, depth, and surface area and included a rectangular “swimming pool” (surface area approximately 20.5 m2, depth approximately 30 cm), a round “pond” (surface area 4.9 m2, depth approximately 80 cm), and a flowing “creek” (surface area 4.0 m2, length approximately 10.0 m, width 40 cm, depth 3-4 cm). Twenty nest boxes were placed in each enclosure (animal-to-nest box ratio: 1:1). The animal behavior in both groups was assessed by direct and video observations. Results showed that the mink generally accepted all 3 water basins and used them extensively from the beginning to the end of the study. Descriptive and negative binomial model analysis of water contact counts obtained from direct observations showed that mink preferred the swimming pool. However, in relation to the basin surface area, the preference effect is more pronounced for the pond. Overall, the animals spent a considerable amount of time at and in the water during their main activity time. On average, each mink could be observed 7 minutes per hour (12.0%) at and in the pool or 3 minutes per hour (5.5%) in the pond. The water quality was very good throughout the study. Although the mink used the water frequently, the total bacteria count and the level of Enterobacteriaceae were always very low. There were no traces of salmonella in any water sample.