Central Bay Research Articles

A 16‐kyr Record of Ocean Circulation and Monsoon Intensification From the Central Bay of Bengal

AbstractThe monsoonal signal dominates most climate records from the Indian Ocean. As a consequence, conventional stable isotope tracers have not been effective at tracking ocean circulation in the Indian Ocean and distinguishing between monsoonal and ocean circulation changes in the Bay of Bengal. Here we present a deglacial through Holocene Nd isotope record of seawater in the central Bay of Bengal, spanning the last 16 kyr. Comparison with a published record from the deep equatorial Indian Ocean (Piotrowski et al., , https://doi.org/10.1016/j.epsl.2009.06.007 shows that Nd isotope ratios of these cores were similar until ~8 ka (ƐNd = −7 to −8 until ~13 ka, and −8.5 to −9.5 between ~13 and 8 ka), after which the Bay of Bengal record diverges to lower values (ƐNd = ~ −10.5). We interpret the Nd isotope record until ~8 ka in both cores to represent the influence of the global overturning ocean circulation. The divergence of the record in the Bay of Bengal since ~8 ka to lower ƐNd values is coincident with a major increase in the strength of the rain‐bearing southwest monsoon and a high sediment load from the Ganga‐Brahmaputra Rivers to the Bengal Fan that reflects major impacts from the intensified monsoon. Thus, the Nd isotopes are sensitive recorders of the changes in monsoon intensity in the Bay of Bengal.

Influence of masonry infill walls on fire-induced collapse mechanisms of steel frames

This paper numerically investigates the influence of masonry infill walls on collapse mechanisms of steel frames under fire scenarios. Three six-story by five-bay steel frames were designed in this study. One of these frames had no infill walls, another one had horizontal infill walls, and the last one had vertical infill walls. Load redistribution and fire resistance were investigated under edge bay fire scenario and central bay fire scenario. The numerical results indicated that masonry infill walls provide alternate load paths in fire conditions, causing significantly large variations of axial forces in surrounding columns. Furthermore, the lateral resistance of the infilled frames is provided by the integral loading resisting system under edge bay fire scenario. The infill walls decrease the buckling temperature and increase the collapse temperature of the heated columns. A series of parametric analyses were performed to investigate the factors influencing the fire resistance of the steel frames. Finally, a preliminary design method was proposed with an aim to prevent the collapse of steel frames with infill walls under fire scenarios.

Spatial structuring of zooplankton communities through partitioning of habitat and resources in the Bay of Bengal during spring intermonsoon

Despite advances in oceanographic investigations in the Indian Ocean, zooplankton ecology is still poorly known from the open waters of the Bay of Bengal. In order to understand the vertical and horizontal distribution of zooplankton in the Bay of Bengal during spring intermonsoon, stratified sampling was conducted using a multiple plankton net. We found that higher zooplankton biomass was often associated with mesoscale cold-core eddies. The biomass in the mixed layer was less in the central bay and the near absence of organisms beneath this layer was attributed to the very low dissolved oxygen levels, including suboxia in the northern extent. The copepod diversity was severely reduced here and only a few species specialized to thrive in minimum oxygen concentrations were found in this zone. However, Pleuromamma indica is another copepod that seems to have adapted to the oxygen minimum zone, as seen from its increased numbers and its strong vertical migrating ability to cross the low oxygen barrier. Highly diverse copepod assemblages comprising 129 identified species were found to be vertically structured, mostly through partitioning of habitat and food resources.

Impact of multiyear La Niña events on the South and East Asian summer monsoon rainfall in observations and CMIP5 models

Impact of multi-year La Nina events on South and East Asian summer monsoon rainfall are examined in the observations and Coupled Model Intercomparison Project Phase 5 (CMIP5) models. The analysis is carried out for the successive two summers, referred to as the first and second years during the period of 1948–2016. Composite analysis suggests that La Nina related sea surface temperature cooling is slightly high in the central and eastern equatorial Pacific during the first year summer. This anomalous cooling associated with La Nina is slightly shifted towards south and south-central Pacific Ocean during the second year. An Atlantic Nino like pattern is evident in the first year unlike the second year. Negative rainfall anomalies are apparent over most of the south Asian region except Bangladesh and Sundarbans, during the first year. Moisture convergence corroborated by low-level circulation to the north of Bangladesh and central India supports the positive rainfall anomalies in the first year. A weak circulation and negative vertically integrated moisture (VIM) anomalies in the rest of the subcontinent are consistent with the negative rainfall anomalies. In addition to these changes, the Atlantic Nino has also been found to be influencing the South Asian rainfall, remotely, during the first year. In the case of the second year, positive rainfall anomalies over the south Asian monsoon region is noted. An anomalous low-level cyclonic circulation over the central Bay of Bengal enhanced the moisture transport into the Indian subcontinent, causing positive rainfall anomalies. Moreover, an anomalous upper level divergence extends from the southeast Indian Ocean, towards the Indian subcontinent, due to La Nina’s response in the second year, which is found to be weak in the first year. This clearly suggests that the enhanced rainfall over the South Asian region is influenced remotely by La Nina forcing as well as local circulation changes during both the years. The East Asian monsoon region reported a tri-pole like structure in the rainfall anomalies, with positive values over southern and central China and negative over parts of Myanmar, Thailand and Cambodia regions and north-east China—North Korea during the first year and vice-versa in the second year. A positive–negative–positive structure in the VIM anomalies is seen in the East Asian region and it supports similar rainfall anomalies during the second year. We have further examined the ability of CMIP5 models in representing multiyear La Nina teleconnections to the south and East Asian summer monsoons. Some models are able to reproduce the South Asian rainfall and circulation anomalies well in the second year, but failed to do so, in the first. The factors responsible for weak teleconnections in the models are discussed in detail.

Clay minerals and Sr-Nd isotopic composition of the Bay of Bengal sediments: Implications for sediment provenance and climate control since 40 ka

Grain size, clay mineralogy, 87Sr/86Sr, εNd, and AMS14C analyses of deep-sea sediments cored in the central Bay of Bengal are used to reconstruct the evolution of provenances and climate control since the last glacial period. Clay minerals, 87Sr/86Sr ratios and εNd values indicate a mixture of sediment from the Himalaya source, Indian Peninsula and Indo-Burman Ranges/Irrawaddy River. These analyses show that the Himalaya Mountains and Indo-Burman Ranges/Irrawaddy River are the main suppliers before the Holocene period, while the inputs of erosion materials from the Indo-Gangetic floodplain and the Indian Peninsula increase during the Holocene period, accompanied by reduced inputs of the Indo-Burman Ranges and Irrawaddy sediments. The regional “source-sink” process is significantly controlled by the climate. Warm and wet climate conditions and enhanced Indian monsoon intensity during the Holocene period are responsible for the increase of sediment input from the Indo-Gangetic Plain and the Indian Peninsula by improving erosion in the source area, input from the floodplain to the river channel and the intensity of the southwest monsoon current. In contrast, due to the decrease of the northeast monsoon current during the Holocene period, sediment input from the Irrawaddy and Indo-Burman Ranges are constrained. Deposition center transition between the submarine fan and shelf during the last glacial period and the Holocene period occurs in response to the sea level change, which controls the sedimentary mode and thus significantly influences the transportation and deposition processes in the Bay of Bengal (BoB).

Riverine Sediment Contribution to Distal Deltaic Wetlands: Fourleague Bay, LA

To combat land loss along the Mississippi River Delta, Louisiana has launched a historic campaign to sustain and regrow coastal lands using, in part, sediment diversions. Previous research has focused primarily on sand-sized sediment load, which is usually deposited proximal to a river’s delta or a diversion’s outlet. Fine sediments constitute the majority of sediment load delivered by rivers, but are understudied with respect to dispersal processes, particularly in terms of sediment supply to distal deltaic bays and wetlands. The Atchafalaya River and associated wetlands serve as prime study areas for this purpose. Fourleague Bay has remained stable against the deteriorative effects of relative sea level rise, standing out along Louisiana’s declining coastline. Push cores were collected once every 2 months, from May 2015 to May 2016, along five central bay sites and five adjacent marsh sites within Fourleague Bay, Louisiana. All sites fall within ~ 10 to 30 km of the Atchafalaya Delta, extending south towards the Gulf of Mexico. Cores were extruded in 2-cm intervals, dried, ground, and analyzed via gamma spectrometry for the presence of 7Be. Inventories of 7Be were then calculated and used to determine daily apparent mass deposition rates (AMDR) over 12 months. Average AMDR values for the bay and the marshes are compared with Atchafalaya River discharge, wind data, and atmospheric pressure through the year of sampling. Peak marsh AMDR, 0.7 ± 0.2 kg m−2 d−1, occurred just after historically high river discharge. Peak bay AMDR, 1.2 ± 0.7 kg m−2 d−1, occurred during seasonal low river discharge and calm winds. Average bay and marsh AMDRs have a moderate negative correlation (r = − 0.51) when compared. Results indicate that, during periods of moderate to high river discharge, sediment bypasses the bay floor and enters the marshes directly when inundation occurs, a process enhanced by the passage of strong atmospheric fronts. During periods of low river discharge and relatively calm winds, riverine sediments aggregate directly onto the bay floor.

Role of East–West Shear Zone and Wind Confluence on the Occurrence of Intense Heavy Rainfall over North Konkan During Southwest Monsoon Season

An attempt has been made to understand the mechanism in occurrence of intense heavy rainfall events over North Konkan and adjoining areas using observed, satellite and reanalysis datasets. Synoptic conditions associated with Dahanu heavy rainfall event, 2016, Mumbai floods, 2005 and historical heavy rainfall events over North Konkan region are considered in the present study. In presence of East–West shear zone with upper air cyclonic circulations extending up to mid-tropospheric levels located at west central Bay of Bengal, west Arabian Sea and anti-cyclonic circulation over east-central Arabian Sea were the major synoptic features observed during these events. Results suggest that the confluence of moisture-laden winds from these circulations over North Konkan lead to the occurrence of intense heavy rainfall events.

Dynamics of Eddy Generation in the Central Bay of Bengal

AbstractEddy activity in the central Bay of Bengal (BoB) is revealed using satellite observations and hydrographic data. Altimetric data show that eddies are generated near the eastern boundary, propagate southwestward, and have periods predominantly in the 30‐ to 120‐day band. Temperature profiles from the Research Moored Array for African‐Asian‐Australian Monsoon Analysis and Prediction (RAMA) buoy at 90°E, 15°N, have their highest amplitude in the depth range of the thermocline, indicating that the eddies are associated with a vertical motion of the thermocline (a first‐baroclinic‐mode response). To investigate the cause of the eddies, we obtained a suite of solutions to nonlinear and linear versions of a 1½‐layer (reduced‐gravity) model. They demonstrate that equatorial wind forcing, Myanmar bump and Andaman Island, and nonlinearity are all essential for eddy formation. Among the nonlinear terms, the advection terms are the primary cause.

Variations in chemical speciation and reactivity of phosphorus between suspended-particles and surface-sediment in seasonal hypoxia-influenced Green Bay

Water, suspended-particles, and surface-sediment samples were collected from Green Bay, Lake Michigan, for the measurements of phosphorus (P) species, including dissolved/particulate-P, inorganic/organic-P, and five different forms of particulate-P, namely exchangeable- or labile-P (Ex-P), iron-bound-P (Fe-P), biogenic-apatite and/or CaCO3-associated-P (CFA-P), organic-P (Org-P) and detrital-apatite-P (Detr-P) to elucidate their reactivity and transformation pathways in the water column. Suspended particles contained mainly Ex-P (25 ± 15%), Fe-P (28 ± 12%) and Org-P (29 ± 7%). In contrast, Detr-P (34 ± 10%) and Org-P (36 ± 12%) were the predominant P species in surface sediment. Contents of Ex-P, Fe-P, Org-P and CFA-P decreased consistently from suspended-particles to surface-sediment, but an increase was observed for the Detr-P, indicating a net loss of Ex-P, Fe-P, Org-P and CFA-P from particulate into dissolved phase. Such active regeneration of P in the water column between particulate and dissolved phases may serve as an internal phosphate source in Green Bay, especially under hypoxic conditions. Degradation of organic matter in south central bay areas seemed to promote hypoxia and enhance the reductive-dissolution of Fe-P and preservation of Org-P under low-oxygen conditions in the central bay. Overall, Ex-P, Fe-P, CFA-P and Org-P species, which comprised up to 50–90% of total particulate-P, can be collectively considered as potentially-bioavailable-P (BAP). Under low-phosphate (0.022 ± 0.014 μM in Green Bay) and summer low-oxygen/hypoxic conditions, suspended-particles may release up to 71% of their BAP before deposited in sediment although the BAP regeneration decreased along the south-north transect in Green Bay.

The impact of interactions between tropical and midlatitude intraseasonal oscillations around the Tibetan Plateau on the 1998 Yangtze floods

This study explores the dynamic processes on intraseasonal time‐scales responsible for the devastating floods over the Yangtze Basin during June–August 1998. Wavelet analysis suggests that the unusual double Meiyu episodes over the south of the middle and lower reaches of the Yangtze River valley (SMLY) depended on the 25–60‐day intraseasonal oscillation (ISO), which has an anomalous ascending branch over the SMLY and descending branch south of 20°N over eastern China. This vertical–meridional cell was not only regulated by the tropical ISO over the Asian summer monsoon region but also modulated by the midlatitude ISO in the upper troposphere. The intraseasonal Rossby wave train along the Asian westerly jet, presenting as the anomalous anticyclone over the Tibetan Plateau (TP) sandwiched between anomalous cyclones in the upstream and downstream areas, tended to trigger another reversed vertical–meridional cell with updraught over the SMLY and downdraught to the north through vorticity advection. The phase‐lock of these ascending branches over the SMLY produced the double Meiyu episodes. The duration of the SMLY flooding was also associated with the interactions between tropical and midlatitude ISOs. During the first wet episode, as the tropical ISO‐related upper‐level divergent flows propagated northward to the southwestern TP, they tended to anchor the anticyclone over the TP through their interaction with the midlatitude rotational circulation. This favoured persistent ascent over the SMLY, and thus the prolonged Meiyu episode in June. In contrast, the northward propagation was confined to the central Bay of Bengal in July, leading to a short Meiyu episode.

Effect of Cyclone Thane in the Bay of Bengal Explored Using Moored Buoy Observations and Multi-platform Satellite Data

This work examines the response of the upper ocean during the passage of cyclone Thane (December 25–30, 2011) over the Bay of Bengal. Observations from a moored buoy are employed to assess the changes in the upper 100 m depth of the ocean. Observations revealed strong temperature inversion prevailing in this region. The temperature inversion resulted in varying response in the subsurface, with warming in the upper 40 m depth and cooling in the depths of 40–80 m at the moored buoy location. Analysis of subsurface temperature and salinity revealed the signatures of vertical mixing induced by Thane. The subsurface currents are observed as strongly responding to the cyclone winds. Analysis revealed that the influence of Thane was generally confined to within 100 m depth. Intense biological response is revealed along the track of the cyclone. However, the bloom is localized in two distinct regions: one in the central Bay and other off the south-western coastal region. This is attributed to the intense Ekman pumping velocity, slow translation speed and the availability of nitrate concentration in the shallow coastal waters.

In Vitro Efficacy of Ebselen and BAY 11-7082 Against Naegleria fowleri.

Primary amebic meningoencephalitis (PAM) is a fatal infection caused by the free-living ameba Naegleria fowleri, popularly known as the “brain-eating ameba.” The drugs of choice in treating PAM are the antifungal amphotericin B and an antileishmanial miltefosine, but these are not FDA-approved for this indication and use of amphotericin B is associated with severe adverse effects. Moreover, very few patients treated with the combination therapy have survived PAM. Therefore, development of efficient drugs is a critical unmet need to avert future deaths of children. Since N. fowleri causes extensive inflammation in the brain it is important to select compounds that can enter brain to kill ameba. In this study, we identified two central nervous system (CNS) active compounds, ebselen and BAY 11-7082 as amebicidal with EC50 of 6.2 and 1.6 μM, respectively. The closely related BAY 11-7085 was also found active against N. fowleri with EC50 similar to BAY 11-7082. We synthesized a soluble ebselen analog, which had amebicidal activity similar to ebselen. Transmission electron microscopy of N. fowleri trophozoites incubated for 48 h with EC50 concentration of ebselen showed alteration in the cytoplasmic membrane, loss of the nuclear membrane, and appearance of electron-dense granules. Incubation of N. fowleri trophozoites with EC50 concentrations of BAY 11-7082 and BAY 11-7085 for 48 h showed the presence of large lipid droplets in the cytoplasm, disruption of cytoplasmic and nuclear membranes and appearance of several vesicles and chromatin residues. Blood-brain barrier permeable amebicidal compounds have potential as new drug leads for Naegleria infection.

Waterfowl migration chronologies in central Chesapeake Bay during 2002–2013

ABSTRACT Contemporary knowledge of migrant waterfowl chronologies is important for effective population management, especially in the context of shifting phenology and climate change. We used a dataset of year-round, every other week, comprehensive bird counts during 2002–2013 on a 461 ha island of shallow water impoundments in central Chesapeake Bay to define the migration period for 21 species of surface and diving waterfowl. Migrant periods for species going north ranged from 7 January through 31 May, with nearly all species reaching a mean date during 19 February through 23 March. South migrant periods ranged from 1 August through 12 February, with most experiencing a mean date during 23 October through 8 January. The migration period average for both surface and diving species was 7 d longer going north than south, whereas both the north and south surface species migration period averages were 15 d longer than the diving species. We found significant differences (P < 0.001) among the migration period...

Spatiotemporal distribution and fluctuation of radiocesium in Tokyo Bay in the five years following the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident.

A monitoring survey was conducted from August 2011 to July 2016 of the spatiotemporal distribution in the 400 km2 area of the northern part of Tokyo Bay and in rivers flowing into it of radiocesium released from the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident. The average inventory in the river mouth (10 km2) was 131 kBq⋅m-2 and 0.73 kBq⋅m-2 in the central bay (330 km2) as the decay corrected value on March 16, 2011. Most of the radiocesium that flowed into Tokyo Bay originated in the northeastern section of the Tokyo metropolitan area, where the highest precipitation zone of 137Cs in soil was almost the same level as that in Fukushima City, then flowed into and was deposited in the Old-Edogawa River estuary, deep in Tokyo Bay. The highest precipitation of radiocesium measured in the high contaminated zone was 460 kBq⋅m-2. The inventory in sediment off the estuary of Old-Edogawa was 20.1 kBq⋅m-2 in August 2011 immediately after the accident, but it increased to 104 kBq⋅m-2 in July 2016. However, the radiocesium diffused minimally in sediments in the central area of Tokyo Bay in the five years following the FDNPP accident. The flux of radiocesium off the estuary decreased slightly immediately after the accident and conformed almost exactly to the values predicted based on its radioactive decay. Contrarily, the inventory of radiocesium in the sediment has increased. It was estimated that of the 8.33 TBq precipitated from the atmosphere in the catchment regions of the rivers Edogawa and Old-Edogawa, 1.31 TBq migrated through rivers and was deposited in the sediments of the Old-Edogawa estuary by July 2016. Currently, 0.25 TBq⋅yr-1 of radiocesium continues to flow into the deep parts of Tokyo Bay.

Submesoscale Processes at Shallow Salinity Fronts in the Bay of Bengal: Observations during the Winter Monsoon

AbstractLateral submesoscale processes and their influence on vertical stratification at shallow salinity fronts in the central Bay of Bengal during the winter monsoon are explored using high-resolution data from a cruise in November 2013. The observations are from a radiator survey centered at a salinity-controlled density front, embedded in a zone of moderate mesoscale strain (0.15 times the Coriolis parameter) and forced by winds with a downfront orientation. Below a thin mixed layer, often ≤10 m, the analysis shows several dynamical signatures indicative of submesoscale processes: (i) negative Ertel potential vorticity (PV); (ii) low-PV anomalies with O(1–10) km lateral extent, where the vorticity estimated on isopycnals and the isopycnal thickness are tightly coupled, varying in lockstep to yield low PV; (iii) flow conditions susceptible to forced symmetric instability (FSI) or bearing the imprint of earlier FSI events; (iv) negative lateral gradients in the absolute momentum field (inertial instability); and (v) strong contribution from differential sheared advection at O(1) km scales to the growth rate of the depth-averaged stratification. The findings here show one-dimensional vertical processes alone cannot explain the vertical stratification and its lateral variability over O(1–10) km scales at the radiator survey.

Anthropogenic marine litter composition in coastal areas may be a predictor of potentially invasive rafting fauna.

Anthropogenic plastic pollution is a global problem. In the marine environment, one of its less studied effects is the transport of attached biota, which might lead to introductions of non-native species in new areas or aid in habitat expansions of invasive species. The goal of the present work was to assess if the material composition of beached anthropogenic litter is indicative of the rafting fauna in a coastal area and could thus be used as a simple and cost-efficient tool for risk assessment in the future. Beached anthropogenic litter and attached biota along the 200 km coastline of Asturias, central Bay of Biscay, Spain, were analysed. The macrobiotic community attached to fouled litter items was identified using genetic barcoding combined with visual taxonomic analysis, and compared between hard plastics, foams, other plastics and non-plastic items. On the other hand, the material composition of beached litter was analysed in a standardized area on each beach. From these two datasets, the expected frequency of several rafting taxa was calculated for the coastal area and compared to the actually observed frequencies. The results showed that plastics were the most abundant type of beached litter. Litter accumulation was likely driven by coastal sources (industry, ports) and river/sewage inputs and transported by near-shore currents. Rafting vectors were almost exclusively made up of plastics and could mainly be attributed to fishing activity and leisure/ household. We identified a variety of rafting biota, including species of goose barnacles, acorn barnacles, bivalves, gastropods, polychaetes and bryozoan, and hydrozoan colonies attached to stranded litter. Several of these species were non-native and invasive, such as the giant Pacific oyster (Crassostrea gigas) and the Australian barnacle (Austrominius modestus). The composition of attached fauna varied strongly between litter items of different materials. Plastics, except for foam, had a much more diverse attached community than non-plastic materials. The predicted frequency of several taxa attached to beached litter significantly correlated with the actually observed frequencies. Therefore we suggest that the composition of stranded litter on a beach or an area could allow for predictions about the corresponding attached biotic community, including invasive species.

The 1997 Kronotsky earthquake and tsunami and their predecessors, Kamchatka, Russia

Abstract. The northern part of the Kamchatka subduction zone (KSZ) experienced three tsunamigenic earthquakes in the 20th century – February 1923, April 1923, December 1997 – events that help us better understand the behavior of this segment. A particular focus of this study is the nature and location of the 5 December 1997 Kronotsky rupture (Mw ∼ 7.8) as elucidated by tsunami runup north of Kronotsky Peninsula in southern to central Kamchatsky Bay. Some studies have characterized the subduction zone off Kronotsky Peninsula as either more locked or more smoothly slipping than surrounding areas and have placed the 1997 rupture south of this promontory. However, 1997 tsunami runup north of the peninsula, as evidenced by our mapping of tsunami deposits, requires the rupture to extend farther north. Previously reported runup (1997 tsunami) on Kronotsky Peninsula was no more than 2–3 m, but our studies indicate tsunami heights for at least 50 km north of Kronotsky Peninsula in Kamchatsky Bay, ranging from 3.4 to 9.5 m (average 6.1 m), exceeding beach ridge heights of 5.3 to 8.3 m (average 7.1 m). For the two 1923 tsunamis, we cannot distinguish among their deposits in southern to central Kamchatsky Bay, but the deposits are more extensive than the 1997 deposit. A reevaluation of the April 1923 historical tsunami suggests that its moment magnitude could be revised upward, and that the 1997 earthquake filled a gap between the two 1923 earthquake ruptures. Characterizing these historical earthquakes and tsunamis in turn contributes to interpreting the prehistoric record, which is necessary to evaluate recurrence intervals for such events. Deeper in time, the prehistoric record back to ∼ AD 300 in southern to central Kamchatsky Bay indicates that during this interval, there were no local events significantly larger than those of the 20th century. Together, the historic and prehistoric tsunami record suggests a more northerly location of the 1997 rupture compared to most other analyses, a revision of the size of the April 1923 earthquake, and agreement with previous work suggesting the northern KSZ ruptures in smaller sections than the southern KSZ. The final suggestion should be considered with caution, however, as we continue to learn that our historic and even prehistoric records of earthquakes and tsunamis are limited, in particular as applied to hazard analysis. This study is a contribution to our continued efforts to understand tectonic behavior around the northern Pacific and in subduction zones, in general.

Conceptual marsh units for Fire Island National Seashore and central Great South Bay salt marsh complex, New York

The salt marsh complex of Fire Island National Seashore (FIIS) and central Great South Bay was delineated to smaller, conceptual marsh units by geoprocessing of surface elevation data. Flow accumulation based on the relative elevation of each location is used to determine the ridge lines that separate each marsh unit while the surface slope is used to automatically assign each unit a drainage point, where water is expected to drain through. Through scientific efforts initiated with the Hurricane Sandy Science Plan, the U.S. Geological Survey has been expanding national assessment of coastal change hazards and forecast products to coastal wetlands, including the Fire Island National Seashore and central Great South Bay salt marshes, with the intent of providing Federal, State, and local managers with tools to estimate the vulnerability and ecosystem service potential of these wetlands. For this purpose, the response and resilience of coastal wetlands to physical factors need to be assessed in terms of the ensuing change to their vulnerability and ecosystem services.

The Foraminifera of Chincoteague Bay, Assateague Island, and the Surrounding Areas: a Regional Distribution Study

AbstractForaminiferal census data from Chincoteague Bay, Newport Bay, the salt marshes of Assateague Island, adjacent mainland salt marshes, and the inner-shelf, were assessed to determine the current assemblages in Chincoteague Bay, and how the different environments surrounding the bay, and the gradients within the bay, influence the microfossil distribution. Determining the current background distribution and its drivers allows for future comparisons to determine paleoenvironmental conditions, impacts from natural and anthropogenic pollution, and the influence of climate change. Foraminiferal census data were compared to sedimentological characteristics and environmental parameters, exhibiting strong correlations with salinity, sediment organic content, and grain-size. Foraminiferal distributions exhibited a gradient from an assemblage dominated by Elphidium cf. E. excavatum near Chincoteague inlet to an assemblage dominated by Ammonia parkinsoniana and Ammobaculites cf. Ab. exiguus in the more restricted central and northern portions of the bay. The sites closest to the mouth of Trappe Creek in Newport Bay, along the western side of Chincoteague Bay and in the central bay, had a greater relative abundance of dead agglutinated taxa compared with the majority of sites in Chincoteague Bay. Despite the overwhelming dominance of calcareous taxa throughout the bay, dissolution may affect the preservation potential of Cribroelphidium poeyanum and Haynesina germanica in the northern and central portions of Chincoteague Bay, as indicated by seasonal pH data. Similarly, the sandy back-barrier lagoonal sites exhibited relatively low densities, potentially a result of dissolution or mechanical destruction.

Observed Variability of Surface Layer in the Central Bay of Bengal:Results of Measurements Using Glider

Underwater gliders measure high-resolution spatiotemporal oceanographic data. In April 2014, the National Institute of Ocean Technology, Chennai operated an underwater glider ‘Barathi’, for 127 days for observation of Bay of Bengal (BoB). In this article we present the effectiveness of the glider Barathi for high resolution temporal sampling of the surface layer in the central BoB for studying variation of temperature, salinity and density structures and acoustic characteristics on 26–27 May 2014. The results showed ‘afternoon effect’ on acoustic characteristics and formation of secondary sound channel. Our data set is strongly correlated (coefficient of determination r 2 > 0.96) with data from a nearby Array for real-time geostrophic Oceanography (Argo) float.