Habitat selection and quality for multiple cohorts of young-of-the-year bluefish (Pomatomus saltatrix): Comparisons between estuarine and ocean beaches in southern New Jersey

In this study, seasonal and annual variability in the use of estuarine and ocean beaches by young-of-the-year bluefish, Pomatomus saltatrix, was evaluated by indices of abundance in coastal areas of southern New Jersey (1998–2000). Biological and physical factors measured at specific sites were correlated with bluefish abundance to determine the mechanisms underlying habitat selection. In addition, integrative and discrete indicators of bluefish growth were used to examine spatio-temporal dynamics in habitat quality and its effect on habitat selection by multiple cohorts of bluefish. Intra-annual recruitment to coastal areas of southern New Jersey was episodic, and resulted from the ingress of spring-spawned bluefish (hatch-date April) to estuarine beaches in late May to early June, followed by the recruitment of summer-spawned fish (hatch-date early July) to ocean beaches from July to October. Bluefish utilized estuarine and ocean beaches in a facultative manner that was responsive to dynamics in prey composition and temperature conditions. The recruitment and residency of bluefish in the estuary (1998–1999) and ocean beaches (1998), for example, was coincidental with the presence of the Atlantic silverside Menidia menidia and bay anchovy Anchoa mitchilli, the principal prey species for bluefish occupying these respective habitat-types. Bluefish abundance in the estuary (2000) and ocean beaches (1999–2000) was also correlated with water temperature, with the greatest catches of juveniles coinciding with their optimal growth temperature (24 °C). Bluefish growth, estimated as the slope of age–length relationships and daily specific growth rates, equaled 1.27–2.63 mm fork length (FL) d⁻¹ and 3.8–8.7% body length increase d⁻¹, respectively. The growth of sagittal otoliths was also used as a proxy for changes in bluefish size during and shortly before their time of capture. Accordingly, otolith growth rates of summer-spawned bluefish were greater at ocean beaches relative to the estuary and were explained by the more suitable temperature conditions found at ocean beaches during the mid- to late summer. Notwithstanding the fast growth of oceanic summer-spawned bluefish, individuals spawned in the spring were still larger in absolute body size at the end of the summer growing season (240 and 50–200 mm FL for spring- and summer-spawned bluefish, respectively). The size discrepancy between spring- and summer-spawned bluefish at the onset of autumn migrations and during overwintering periods may account for the differential recruitment success of the respective cohorts.     

Paleomonsoon precipitation deduced from a sediment core from the equatorial Indian Ocean

Rapid shifts in past climate recorded in polar ice sheets have elicited various explanations relating to either thermohaline circulation changes by ice-rafting or natural greenhouse gas concentrations modulated by climatic conditions in the tropics. To compare the tropical paleoclimate record with the polar record, one must choose sediment cores from highly productive ocean regions. Necessarily, such regions reflect the wind records in the tropics, because high productivity is associated with upwelling driven by winds. Comparing tropical precipitation records with high-latitude records is, however, a more difficult task because sediments recording paleoprecipitation usually have low sedimentation rates, and offer coarser resolution relative to polar ice cores. Here, we present δ ¹⁸O data of three planktonic species of Foraminifera (a proxy for precipitation) from such a sediment core, spanning the past 35 ka for the equatorial Indian Ocean, which falls under the southwest monsoon (SWM) realm. Results show that minimum SWM precipitation occurred at the Last Glacial Maximum, with a subsequent increase at Termination IA. During the Holocene, SWM precipitation intensified uniformly up to the core top (∼2.2 ka b.p.), as revealed by generally decreasing δ ¹⁸O values. Variations in precipitation are consistent with climate changes recorded in polar ice sheets. Although the different resolutions of the two records preclude a rigorous comparison, abrupt cooling/warming events appear to be accompanied by sudden reduction/enhancement in (SWM) rainfall. Thus, mechanisms with time scales much shorter than a millennium, such as natural greenhouse warming (e.g., CH₄ concentration), controlled by emissions from the tropics, could have played a major role in high-latitude climate change.     

SeagrassNet monitoring across the Americas: case studies of seagrass decline

Seagrasses are an important coastal habitat worldwide and are indicative of environmental health at the critical land–sea interface. In many parts of the world, seagrasses are not well known, although they provide crucial functions and values to the world's oceans and to human populations dwelling along the coast. Established in 2001, SeagrassNet, a monitoring program for seagrasses worldwide, uses a standardized protocol for detecting change in seagrass habitat to capture both seagrass parameters and environmental variables. SeagrassNet is designed to statistically detect change over a relatively short time frame (1–2 years) through quarterly monitoring of permanent plots. Currently, SeagrassNet operates in 18 countries at 48 sites; at each site, a permanent transect is established and a team of people from the area collects data which is sent to the SeagrassNet database for analysis. We present five case studies based on SeagrassNet data from across the Americas (two sites in the USA, one in Belize, and two in Brazil) which have a common theme of seagrass decline; the study represents a first latitudinal comparison across a hemisphere using a common methodology. In two cases, rapid loss of seagrass was related to eutrophication, in two cases losses related to climate change, and in one case, the loss is attributed to a complex trophic interaction resulting from the presence of a marine protected area. SeagrassNet results provide documentation of seagrass change over time and allow us to make scientifically supported statements about the status of seagrass habitat and the extent of need for management action.     

Calibration of JASON-1 Altimeter over Lake Erie

This article describes absolute calibration results for both JASON-1 and TOPEX Side B (TSB) altimeters obtained at the Lake Erie calibration site, Marblehead, Ohio, USA. Using 15 overflights, the estimated JASON altimeter bias at Marblehead is 58 ± 38 mm, with an uncertainty of 19 mm based on detailed error analysis. Assuming that the TSB bias is negligible, relative bias estimates using both data from the TSB-JASON formation flight period and data from 48 water level gauges around the entire Great Lakes confirmed the Marblehead results. Global analyses using both the formation flight data and dual-satellite (TSB and JASON) crossovers yield a similar relative bias estimate of 146 ± 59 mm, which agrees well with open ocean absolute calibration results obtained at Harvest, Corsica, and Bass Strait (e.g., Watson et al. 2003). We find that there is a strong dependence of bias estimates on the choice of sea state bias (SSB) models. Results indicate that the invariant JASON instrument bias estimated oceanwide is 71 mm, with additional biases of 76 mm or 28 mm contributed by the choice of Collecte Localisation Satellites (CLS) SSB or Center for Space Research (CSR) SSB model, respectively. Similar analysis in the Great Lakes yields the invariant JASON instrument bias at 19 mm, with the SSB contributed biases at 58 mm or 13 mm, respectively. The reason for the discrepancy is currently unknown and warrants further investigation. Finally, comparison of the TOPEX/POSEIDON mission (1992-2002) data with the Great Lakes water level gauge measurements yields a negligible TOPEX altimeter drift of 0.1 mm/yr.     

Computer Monte Carlo simulation in quantitative resource estimation

The method of making quantitative assessments of mineral resources sufficiently detailed for economic analysis is outlined in three steps. The steps are (1) determination of types of deposits that may be present in an area, (2) estimation of the numbers of deposits of the permissible deposit types, and (3) combination by Monte Carlo simulation of the estimated numbers of deposits with the historical grades and tonnages of these deposits to produce a probability distribution of the quantities of contained metal.Two examples of the estimation of the number of deposits (step 2) are given. The first example is for mercury deposits in southwestern Alaska and the second is for lode tin deposits in the Seward Peninsula.The flow of the Monte Carlo simulation program is presented with particular attention to the dependencies between grades and tonnages of deposits and between grades of different metals in the same deposit.     

Chloride source delineation in an urban-agricultural watershed: Deicing agents versus agricultural contributions

Analyses (n = 525) of chloride (Cl⁻), bromide (Br⁻), nitrate as nitrogen (NO₃-N), sodium (Na⁺), calcium (Ca²⁺) and potassium (K⁺) in stream water, tile-drain water and groundwater were conducted in an urban-agricultural watershed (10% urban/impervious, 87% agriculture) to explore potential differences in the signature of Cl⁻ originating from an urban source as compared with an agricultural source. Only during winter recharge events did measured Cl⁻ concentrations exceed the 230 mg/L chronic threshold. At base flow, nearly all surface water and tile water samples had Cl⁻ concentrations above the calculated background threshold of 18 mg/L. Mann–Whitney U tests revealed ratios of Cl⁻ to Br⁻ (p = .045), to NO₃-N (p < .0001), to Ca²⁺ (p < .0001), and to Na⁺ (p < .0001) to be significantly different between urban and agricultural waters. While Cl⁻ ratios indicate that road salt was the dominant source of Cl⁻ in the watershed, potassium chloride fertilizer contributed as an important secondary source. Deicing in watersheds where urban land use is minimal had a profound impact on Cl⁻ dynamics; however, agricultural practices contributed Cl⁻ year-round, elevating stream base flow Cl⁻ concentrations above the background level.     

Prospects of large-scale noble metal mineralization in the Upper Selemdzha minerogenic zone (by the example of the Malomyr and Sagur-Semertak ore clusters)

The Upper Selemdzha minerogenic zone, which has the potential for noble metal mineralization in the Upper Amur, has been studied. It is confined to the thick strata of Paleozoic terrigeneous-sedimentary rocks (sandstones, siltstones, clay schists, packages of their thin rhythmical interlayering, sedimentary breccias, and conglomerates) in the Tokura subzone of the Selemdzha-Kerbinsk zone in the Amur-Okhotsk area of the Mongol-Okhotsk system, overlain by Early Cretaceous volcanogenic sedimentary rocks and intruded by Early Cretaceous quartz diorites, granodiorites, and dacites. In the Malomyr and Sagur-Semertak ore clusters, there are a few known potential deposits of noble metals and ore occurrences; when studied and prospected, they can exhibit vein-veinlet noble metal mineralization with rich contents of gold and platinoids in ore columns and metasomatic deposits.     

An analysis of storm-induced landslides in colluvial soils overlying mudrock sequences, southeastern Ohio, USA

In late-June, 1998, a series of thunderstorms dropped 16.5 cm (6.5 in.) of rain in a 72-h period over southeastern Ohio, causing extensive flooding, six deaths, and 179 million dollars in property damage. The storms also triggered more than 60 shallow landslides along a 64 km (40-mi) stretch of Interstate 77 between Buffalo and Marietta, Ohio. Almost all of the landslides were translational, occurring along the contact between colluvial soils and the underlying bedrock (shales, claystones, mudstones). Six sites were selected in the affected area for a detailed study of the shallow landslides. At each site, a record was made of the stratigraphy, slope geometry, number of landslides, landslide dimensions, hydrologic conditions, and influence of vegetation on landslide distribution. Both colluvial soils and underlying bedrock were sampled for laboratory investigations, which included determination of natural water content, grain size distribution, Atterberg limits, permeability, slake durability, and shear-strength parameters. Data from laboratory tests were used to perform sensitivity and stability analyses with respect to varying slope angles, strength parameters, and thicknesses of saturated colluvial soil. The results of the study indicate that the shallow landslides along Interstate 77 occurred when the colluvial soils reached 90% to 100% saturation, depending upon the slope angles.