Isotopic evidence concerning the habitat of Nautilus macromphalus in New Caledonia.

Modern nautilids (Nautilus and Allonautilus) have often been studied by paleontologists to better understand the anatomy and ecology of fossil relatives. Because direct observations of these animals are difficult, the analysis of light stable isotopes (C, O) preserved in their shells has been employed to reveal their habitat and life history. We aim to (1) reconstruct the habitat depth of Nautilus macromphalus and (2) decipher the fraction of metabolic carbon in its shell by analyzing oxygen and carbon isotopes (δ18O, δ13C) in the septa of two specimens in combination with analyses of water samples from the area. Additionally, we investigate whether morphological changes during ontogeny are reflected in the isotopic values of the shells. Results reveal that the patterns of change of δ18O and δ13C in the septa of N. macromphalus pre- and post-hatching are consistent with previous studies. Values of δ18Owater range from 0.7 to 1.4‰ (VSMOW), with a maximum value coincident with a salinity maximum at ~150 m. We use the temperature and δ18Owater profiles to calculate equilibrium values of δ18Oaragonite with depth. Comparing these values with the measured δ18O of the septa shows that the habitat depth of N. macromphalus is ~140 m pre-hatching and ~370 m post-hatching. Using δ13C of shell carbonate and published data on metabolic carbon, the fraction of metabolic carbon is reconstructed as ~21% and 14% pre- and post-hatching, respectively. The reconstructed depth pre-hatching is slightly shallower than in N. pompilius from the Philippines and Fiji, but the post-hatching depth is similar. However, it is important to emphasize that these estimates represent average over time and space because nautilus is a mobile animal. Lastly, the changes in morphological parameters and the changes in δ13C and δ18O during ontogeny do not coincide except at hatching and at the onset of maturity.

Seasonal differences in trace element concentrations and distribution in Spartina alterniflora root tissue.

The present study uses nanometer-scale synchrotron X-ray nanofluorescence to investigate season differences in concentrations and distributions of major (Ca, K, S and P) and trace elements (As, Cr, Cu, Fe and Zn) in the root system of Spartina alterniflora collected from Jamaica Bay, New York, in April and September 2015. The root samples were cross-sectioned at a thickness of 10 µm. Selected areas in the root epidermis and endodermis were mapped with a sampling resolution of 100 and 200 nm, varying with the mapping areas. The results indicate that trace element concentrations in the epidermis and endodermis vary among the elements measured, possibly because of their different chemical properties or their ability to act as micronutrients for the plants. Elemental concentrations (As, Ca, Cr, Cu, Fe, K, P, S and Zn) within each individual root sample and between the root samples collected during two different seasons are both significantly different (p < 0.01). Furthermore, this study indicates that the nonessential elements (As and Cr) are significantly correlated (p < 0.01) with Fe, with high concentrations in the root epidermis, while others are not, implying that Fe may be a barrier to nonessential element transport in the root system. Hierarchy cluster analysis shows two distinct groups, one including As, Cr and Fe and the other the rest of the elements measured. Factor analysis also indicates that the processes and mechanisms controlling element transport in the root system can be different between the nutrient and nonessential elements.

Nanoscale measurement of trace element distributions in Spartina alterniflora root tissue during dormancy.

This paper reports a nanometer-scale investigation of trace element (As, Ca, Cr, Cu, Fe, Mn, Ni, S and Zn) distributions in the root system Spartina alterniflora during dormancy. The sample was collected on a salt marsh island in Jamaica Bay, New York, in April 2015 and the root was cross-sectioned with 10 µm resolution. Synchrotron X-ray nanofluorescence was applied to map the trace element distributions in selected areas of the root epidermis and endodermis. The sampling resolution was 60 nm to increase the measurement accuracy and reduce the uncertainty. The results indicate that the elemental concentrations in the epidermis, outer endodermis and inner endodermis are significantly (p < 0.01) different. The root endodermis has relatively higher concentrations of these elements than the root epidermis. Furthermore, this high resolution measurement indicates that the elemental concentrations in the outer endodermis are significantly (p < 0.01) higher than those in the inner endodermis. These results suggest that the Casparian strip may play a role in governing the aplastic transport of these elements. Pearson correlation analysis on the average concentrations of each element in the selected areas shows that most of the elements are significantly (p < 0.05) correlated, which suggests that these elements may share the same transport pathways.

Ammonite habitat revealed via isotopic composition and comparisons with co-occurring benthic and planktonic organisms.

Ammonites are among the best-known fossils of the Phanerozoic, yet their habitat is poorly understood. Three common ammonite families (Baculitidae, Scaphitidae, and Sphenodiscidae) co-occur with well-preserved planktonic and benthic organisms at the type locality of the upper Maastrichtian Owl Creek Formation, offering an excellent opportunity to constrain their depth habitats through isotopic comparisons among taxa. Based on sedimentary evidence and the micro- and macrofauna at this site, we infer that the 9-m-thick sequence was deposited at a paleodepth of 70-150 m. Taxa present throughout the sequence include a diverse assemblage of ammonites, bivalves, and gastropods, abundant benthic foraminifera, and rare planktonic foraminifera. No stratigraphic trends are observed in the isotopic data of any taxon, and thus all of the data from each taxon are considered as replicates. Oxygen isotope-based temperature estimates from the baculites and scaphites overlap with those of the benthos and are distinct from those of the plankton. In contrast, sphenodiscid temperature estimates span a range that includes estimates of the planktonic foraminifera and of the warmer half of the benthic values. These results suggest baculites and scaphites lived close to the seafloor, whereas sphenodiscids sometimes inhabited the upper water column and/or lived closer to shore. In fact, the rarity and poorer preservation of the sphenodiscids relative to the baculites and scaphites suggests that the sphenodiscid shells may have only reached the Owl Creek locality by drifting seaward after death.

Medically-Derived (131)I as a Tool for Investigating the Fate of Wastewater Nitrogen in Aquatic Environments.

Medically derived (131)I (t1/2 = 8.04 d) is discharged from water pollution control plants (WPCPs) in sewage effluent. Iodine's nutrient-like behavior and the source-specificity of (131)I make this radionuclide a potentially valuable tracer in wastewater nitrogen studies. Iodine-131 was measured in Potomac River water and sediments in the vicinity of the Blue Plains WPCP, Washington, DC, USA. Dissolved (131)I showed a strong, positive correlation with δ(15)N values of nitrate (δ(15)NO3(-)) in the river, the latter being a traditional indicator of nutrient inputs and recycling. Surface water δ(15)NO3(-) values ranged from 8.7 to 33.4‰; NO3(-) + NO2(-) concentrations were 0.39-2.79 mg N L(-1) (26-186 µM). Sediment profiles of particulate (131)I and δ(15)N indicate rapid mixing or sedimentation and in many cases remineralization of a heavy nitrogen source consistent with wastewater nitrogen. Values of δ(15)N in sediments ranged from 4.7 to 9.3‰. This work introduces (131)I as a tool to investigate the short-term fate of wastewater nitrogen in the Potomac River and demonstrates the general utility of (131)I in aquatic research.

Geochronologies of pharmaceuticals in a sewage-impacted estuarine urban setting (Jamaica Bay, New York).

Pharmaceuticals are active substances found in sewage effluents and can negatively impact aquatic systems even at low concentrations. A fraction of these chemicals can be attached onto suspended solids and end up in sediments. This research shows concentrations of a wide group of pharmaceuticals in sediments from an urban estuarine setting (Jamaica Bay, New York). Highest concentrations (>75 ng g(-1)) were measured in surface sediments from the inner part of the bay, directly affected by sewage discharges and where water circulation is more restricted. Only 16 out of 61 target compounds were detected, and those positively charged (e.g., metoprolol) and/or highly hydrophobic (e.g., tamoxifen) were predominant. Their sediment-pore water partition coefficients were also calculated for the first time and were in a range between 11 and 2041 L/kg depending on the compound. Analysis of dated sediment cores revealed that pharmaceuticals were well preserved along the sedimentary column, a highly reducing environment. There was an increase in the concentration of most target compounds over the last five decades correlated with the increase in their usage, with some exceptions such as sulfamethazine (now used only for veterinary purposes). Thus, overall concentration of pharmaceuticals in sediment cores showed a doubling time of 9.2 years. Vertical distribution profiles for selected compounds also allowed reconstructing the history of contamination at Jamaica Bay by pharmaceuticals. The use of some of these chemicals as sewage molecular markers was also investigated.

An unusual occurrence of Nautilus macromphalus in a cenote in the Loyalty Islands (New Caledonia).

Exploration of a landlocked cenote on Lifou (Loyalty Islands) revealed 37 shells of the cephalopod Nautilus macromphalus Sowerby, 1849, in saltwater on the cenote floor, approximately 40 m below the water surface. The occurrence of these shells is unusual because N. macromphalus is restricted to the open marine waters surrounding the island. All of the shells are mature, and nearly all of them are unbroken, with faded red-brown color stripes. We analyzed seven shells to determine their age. Radiocarbon dating yielded ages of 6380±30 to 7095±30 y BP. The 238U-series radionuclides 210Pb (half-life  = 22.3 y) and 226Ra (half-life  = 1600 y) also were measured. Two of the samples showed radioactive equilibrium between the nuclides, consistent with the old radiocarbon dates, but the other five samples showed excess 210Pb. When corrected for radioactive decay, the 226Ra activities were much greater than those found in living Nautilus. We conclude that exposure to high activities of 222Rn and 226Ra in the salty groundwater of the cenote altered the activities originally incorporated into the shells. Human placement of the shells in the cavity is rejected based on their radiocarbon age and the geometry of the cenote. The most probable explanation is that the animals entered the flooded karstic system through a connection on the seaward side at approximately 7,000 y BP, during an interval of slowly rising sea level. Unable to find an exit and/or due to anoxic bottom waters, the animals were trapped and died inside. The open connection with the sea persisted for ∼700 y, but after ∼6400 y BP, the connection was lost, probably due to a roof collapse. This is a rare example of Nautilus in a karstic coastal basin and provides a minimum age for the appearance of N. macromphalus in the Loyalty Islands.

A new approach for the determination of ammonite and nautilid habitats.

Externally shelled cephalopods were important elements in open marine habitats throughout Earth history. Paleotemperatures calculated on the basis of the oxygen isotope composition of their shells can provide insights into ancient marine systems as well as the ecology of this important group of organisms. In some sedimentary deposits, however, the aragonitic shell of the ammonite or nautilid is poorly or not preserved at all, while the calcitic structures belonging to the jaws are present. This study tests for the first time if the calcitic jaw structures in fossil cephalopods can be used as a proxy for paleotemperature. We first analyzed the calcitic structures on the jaws of Recent Nautilus and compared the calculated temperatures of precipitation with those from the aragonitic shell in the same individuals. Our results indicate that the jaws of Recent Nautilus are secreted in isotopic equilibrium, and the calculated temperatures approximately match those of the shell. We then extended our study to ammonites from the Upper Cretaceous (Campanian) Pierre Shale of the U.S. Western Interior and the age-equivalent Mooreville Chalk of the Gulf Coastal Plain. In the Pierre Shale, jaws occur in situ inside the body chambers of well-preserved Baculites while in the Mooreville Chalk, the jaw elements appear as isolated occurrences in the sediment and the aragonitic shell material is not preserved. For the Pierre Shale specimens, the calculated temperatures of well-preserved jaw material match those of well-preserved shell material in the same individual. Analyses of the jaw elements in the Mooreville Chalk permit a comparison of the paleotemperatures between the two sites, and show that the Western Interior is warmer than the Gulf Coast at that time. In summary, our data indicate that the calcitic jaw elements of cephalopods can provide a reliable geochemical archive of the habitat of fossil forms.

Behavior of medically-derived 131I in the tidal Potomac River.

Iodine-131 (t1/2=8.04 d) is administered to patients for treatment of thyroid disorders, excreted by patients and discharged to surface waters via sewage effluent. Radionuclides generally behave like their stable analogs; therefore, medically-derived (131)I is useful as a transport-reaction tracer of anthropogenic inputs and the aquatic biogeochemistry of iodine. Iodine-131 was measured in Potomac River water and sediments in the vicinity of the Blue Plains Water Pollution Control Plant (WPCP), Washington, DC, USA. Concentrations measured in sewage effluent from Blue Plains WPCP and in the Potomac River suggest a relatively continuous source of this radionuclide. The range of (131)I concentrations detected in surface water was 0.076±0.006 to 6.07±0.07 Bq L(-1). Iodine-131 concentrations in sediments ranged from 1.3±0.8 to 117±2 Bq kg(-1) dry weight. Partitioning in the sewage effluent from Blue Plains and in surface waters indicated that (131)I is associated with colloidal and particulate organic material. The behavior of medically-derived (131)I in the Potomac River is consistent with the nutrient-like behavior of natural iodine in aquatic environments. After discharge to the river via sewage effluent, it is incorporated into biogenic particulate material and deposited in sediments. Solid phase sediment profiles of (131)I indicated rapid mixing or sedimentation of particulate debris and diagenetic remineralization and recycling on short time scales.

Atmospheric fluxes of (7)Be and (210)Pb on monthly time-scales and during rainfall events at Stony Brook, New York (USA).

The particle-reactive radionuclides (7)Be and (210)Pb have been employed extensively as tracers and chronometers for a variety of aquatic and terrestrial processes. Both radionuclides are delivered to the Earth's surface from the atmosphere, and in order to use them effectively as natural tracers, an understanding of variations in atmospheric fluxes of these radionuclides due to latitudinal differences and storm events is required. The monthly atmospheric fluxes of (7)Be and (210)Pb, measured from April-2008 to December-2009 at Stony Brook, NY, ranged from 67 to 385 Bq m(-2) and 6.7 to 16.7 Bq m(-2), respectively. Composite annual atmospheric fluxes over the sampling period were 3110 ± 1200 Bq m(-2) y(-1) for (7)Be and 146 ± 50 Bq m(-2) y(-1) for (210)Pb and were similar to geographically comparable sites. The monthly atmospheric fluxes of (7)Be and (210)Pb were significantly correlated with rainfall. The (7)Be/(210)Pb ratio in the monthly samples varied seasonally, with values of ∼10-11 during the winter months and ∼20-28 during the spring - fall. The pattern of seasonal variation in (7)Be fluxes and (7)Be/(210)Pb ratios is most consistent with that observed in surface air at continental sites in which more frequent deep convective storms occur during the summer and therefore result in an increased transport of (7)Be from the upper troposphere to the Earth's surface. An additional factor may be that the winds at Stony Brook were dominantly from the northwest during the winter of 2009 and so were characterized by low (7)Be/(210)Pb ratios while in the spring, winds from the southwest brought marine air with higher (7)Be/(210)Pb ratios to the sampling site. Fluxes of (7)Be and (210)Pb also were measured over two long (16-24 h) and two short (∼1 h) intense periods of rainfall in June and July 2009. Fluxes of (7)Be and (210)Pb continued throughout the short events, but the two radionuclides showed different patterns during the long events. While the entirety of the (210)Pb flux accumulated during the first ∼1 h, (7)Be continued to be accumulated over the course of both long events. The (7)Be/(210)Pb ratio ranged from 20 to ∼300 during the events and, in general, was considerably greater than the ratios measured in the monthly samples. Radar image snapshots taken during the events show cloud heights of 7-10.5 km, and the (7)Be/(210)Pb ratios measured in the precipitation are consistent with previous model estimates of (7)Be/(210)Pb ratios in aerosols at altitudes of 5-10 km (latitude 40°N). The data suggest that (210)Pb can be effectively stripped from the lower troposphere early in a rainfall event, but intense convective mixing and scavenging of (7)Be from the upper troposphere results in a continuous flux of (7)Be and elevated (7)Be/(210)Pb ratios as the event progresses.

Medically-derived 131I in municipal sewage effluent.

This work presents (131)I (t(½) = 8.04 d) concentrations in sewage effluent from the Stony Brook Water Pollution Control Plant (WPCP), a small plant serving a regional thyroid cancer treatment facility in Stony Brook, NY, USA. The concentrations detected in sewage effluent ranged from 1.8 ± 0.3 to 227 ± 2 Bq L(-1). The primary source of (131)I is excreta from thyroid cancer inpatients treated at the Stony Brook University Medical Center. Based on several time series measurements following known inpatient treatments, the mean sewage half-life (T(s)) of iodine is 3 d in this plant. The T(s), analogous to a radioactive half-life, describes the time it takes for half of a wastewater component to be removed from a WPCP. Flow recycling, or activated sludge, used to maintain bacterial populations necessary for sewage treatment causes iodine to remain in this plant far longer than its hydraulic retention time. The experimental results suggest that most (131)I entering the Stony Brook WPCP leaves in sewage effluent, not in sewage sludge. Patient treatments can result in continuous discharges of (131)I to surface waters where it can be used as a tracer of sewage-derived material and to understand the behavior of (131)I in aquatic environments.

The particulate 7Be/210Pbxs and 234Th/210Pbxs activity ratios as tracers for tidal-to-seasonal particle dynamics in the Gironde estuary (France): implications for the budget of particle-associated contaminants.

The short-lived natural radionuclides (7)Be (T(1/2)=53 days), (234)Th(xs) (T(1/2)=24.1 days) and (210)Pb(xs) (T(1/2)=22.3 years), i.e. (234)Th and (210)Pb in excesses of that supported within particles by the decay of their parent isotopes, were analysed in suspended particulate matter (SPM) to study the particle dynamics in the Gironde fluvial estuarine system (France), strongly impacted by heavy metal pollution. From surveys of this land-ocean interface in 2006 and 2007, we established a times series of these radioisotopes and of their activity ratios ((7)Be/(210)Pb(xs) and (234)Th/(210)Pb(xs) ARs) in particles sampled under different hydrological conditions. The particulate (7)Be/(210)Pb(xs) AR varies along the fluvial estuarine system mainly due to variations in (7)Be activities, controlled by riverine, oceanic and atmospheric inputs and by resuspension of old (7)Be-deficient sediments. These processes vary with river discharge, tidal cycle and season. Therefore, seasonal particle transport processes can be described using variations of the SPM (7)Be/(210)Pb(xs) ARs. During high river discharge, the SPM (7)Be/(210)Pb(x) ARs decrease from river to the ocean. The turbidity maximum zone (TMZ) is dispersed and the particles, and the associated contaminants, are rapidly transported from river to coastal waters, without significant retention within the TMZ. During low river discharge, the TMZ intrudes into the fluvial estuary, and the lowest (7)Be/(210)Pb(x) ARs are observed there due to resuspension of (7)Be-deficient sediments. Away from the TMZ, from the middle to lower estuary, SPM (7)Be/(210)Pb(x) ARs increase, indicating that the particles have been recently tagged with (7)Be. We explain this trend as being caused by marine input of dissolved radionuclides, as traced by SPM (234)Th/(210)Pb(xs) ARs, followed by scavenging in the estuary. This result indicates that particle transport models based on (7)Be and trace-metal budgets must consider oceanic dissolved inputs as an additional source of (7)Be and, possibly, of contaminants to estuaries.

Radium and radium-daughter nuclides in carbonates: a brief overview of strategies for determining chronologies.

Radium isotopes have been used extensively to trace the movement of groundwater as well as oceanic water masses, but these radionuclides (and their daughters) are also useful chronometers for the determination of the time scales of other Earth and environmental processes. The purpose of this overview is to present the application of Ra and Ra daughters in the dating of carbonates. We show that the choice of dating method (decay of excess radionuclide or ingrowth of daughter) depends strongly on the parent/daughter activity ratios in the water in which the carbonate was precipitated. Thus freshly precipitated carbonates uniformly show excesses of 226Ra relative to its parent 230Th, and 226Ra decay can provide ages of carbonates over Holocene time scales. In contrast, carbonates are precipitated in waters of greatly varying 210Pb/226Ra. Corals, deep-sea hydrothermal vent clams and the shelled cephalopod Nautilus live in waters with significant dissolved 210Pb and all show excesses of 210Pb in their carbonate. Bivalve molluscs from nearshore and coastal waters, and carbonates deposited from groundwater environments (e.g. travertines) in which 210Pb is efficiently scavenged from solution, show deficiencies of 210Pb relative to 226Ra. In contrast, fish otoliths strongly discriminate against 210Pb regardless of the environment in which the fish lives. Deficiencies of 228Th relative to 228Ra are common in all carbonates. Useful time ranges for the 210Pb/226Ra and 228Th/228Ra chronometers are approximately 100 y and approximately 10 y, respectively.

The role of sea ice in the fate of contaminants in the Arctic Ocean: plutonium atom ratios in the Fram Strait.

Atom ratios of 240Pu to 239Pu in bottom sediments from the Fram Strait are used to provide evidence for the long distance dispersion of Pu in the Arctic Ocean. In particular, low (<0.18) 240Pu/239Pu ratios indicate that plutonium from sources in the Kara Sea and Novaya Zemlya is transported across the basin toward the North Atlantic. The results have implications for the ability of sea ice to incorporate, intercept, and transport contaminants in the Arctic Ocean. They demonstrate that the fates of sea ice and associated contaminants in the Arctic Ocean are closely coupled, with the release of the particulate load and associated chemical species occurring in principal sea ice ablation areas such as the Fram Strait.

Transport and sources of metal contaminants over the course of tidal cycle in the turbidity maximum zone of the Hudson River estuary.

Transport and source of metal contaminants (Ag, Cd, Cu, Pb and Zn) in the turbidity maximum zone of the Hudson River estuary were studied over the course of a tidal cycle in November 1994 and August 1995. This study showed that the metal/Fe ratios in suspended particles varied more widely than those in the local sediments, implying that sources of metal contaminants to the water column are not only from local sediment resuspension but also from lateral advection. Although the metal/Fe ratios oscillate with time at the anchor stations, a general increasing trend with salinity was found over the course of a tidal cycle, suggesting that the lower estuary could be a source of metal contaminants to the upper estuary regions. These results support that sediment resuspension and lateral advection are important factors responsible for transporting the lower estuary contaminants up river and redistributing metal contaminants in the estuary.