Differences in Prey Capture Behavior in Populations of Blue Crab (<Emphasis Type="Italic">Callinectes sapidus</Emphasis> Rathbun) from Contaminated and Clean Estuaries in New Jersey

Populations living in contaminated environments may exhibit behavioral changes that can alter predator–prey interactions. Blue crabs from the contaminated Hackensack Meadowlands (HM) had reduced ability to capture juvenile blue crabs and adult mummichogs (both active prey) compared with crabs from a reference site (Tuckerton (TK)). However, they consumed equivalent amounts of ribbed mussels and fiddler crabs, which are less active prey. Crabs may have reduced coordination rather than appetite or motivation. The lab data are supported by stomach analysis of field-caught crabs. HM crab stomachs contained ∼60% algae, plant material, detritus, and sediment and much lower weights of crab, fish, and other live food than TK crabs. However, the relative absence of bivalves in their diet may reflect reduced amounts available. When TK crabs were caged in HM or fed food from HM in the lab for 8 weeks, their prey capture ability declined significantly, and mercury in their muscle tissue increased significantly, indicating that environmental factors were responsible for the behavioral differences. When HM crabs were caged in TK or fed fish from TK in the lab for 8 weeks, their prey capture ability improved significantly. Mercury levels were variable and did not show a significant decrease.     

Use of a single-bowl continuous-flow centrifuge for dewatering suspended sediments: Effect on sediment physical and chemical characteristics

The use of a single-bowl continuous-flow centrifuge (CFC, Sharples-Pennwalt Model AS-12) for dewatering suspended sediment from large volumes of river water is evaluated. Sediment-recovery efficiency of 86-91 per cent is comparable to that of other types of CFC units. The recovery efficiency is limited by the particle-size distribution of the feed water and by the limiting particle diameter that is retained in the centrifuge bowl. The limiting particle diameter, using the parameters for this study (bowl radius = 10.5cm; bowl length = 71.1 cm; rotational velocity = 16000 r min^?1; flow rate = 2 L min^?1, and an assumed hydrated particle density = 1.7 gm cm^?3), is 370 nm. There seems to be no particle-size fractionation within the centrifuge bowl—the median particle size was the same at the top as at the bottom. Particle electrophoretic mobility plays some role in fractionation of particles within the centrifuge. The mobility ranged from ?1.19 to ?2.01 × 10^?8 m² V^?1 s^?1, which is typical of clays coated with organic matter, the charge of which is partially neutralized by divalent cations and iron. Contamination by trace metals and organics is minimized by coating all surfaces that come in contact with the sample with either FEP or PFA Teflon and using a removable FEP Teflon liner in the centrifuge bowl. Because of the physical and chemical factors affecting particle fractionation within the centrifuge, care must be exercised in interpreting the environmental consequences of particles collected by continuous-flow centrifugation.     

Determination of Cl Production Rates Derived from the Well-Dated Deglaciation Surfaces of Whidbey and Fidalgo Islands, Washington

The ³⁶Cl dating method is increasingly being used to determine the surface-exposure history of Quaternary landforms. Production rates for the ³⁶Cl isotopic system, a critical component of the dating method, have now been refined using the well-constrained radiocarbon-based deglaciation history of Whidbey and Fidalgo Islands, Washington. The calculated total production rates due to calcium and potassium are 91±5 atoms ³⁶Cl (g Ca)⁻¹ yr⁻¹ and are 228±18 atoms ³⁶Cl (g K)⁻¹ yr⁻¹, respectively. The calculated ground-level secondary neutron production rate in air, P_f(0), inferred from thermal neutron absorption by ³⁵Cl is 762±28 neutrons (g air)⁻¹ yr⁻¹ for samples with low water content (1–2 wt.%). Neutron absorption by serpentinized harzburgite samples of the same exposure age, having higher water content (8–12 wt.%), is 40% greater relative to that for dry samples. These data suggest that existing models do not adequately describe thermalization and capture of neutrons for hydrous rock samples. Calculated ³⁶Cl ages of samples collected from the surfaces of a well-dated dacite flow (10,600–12,800 cal yr B.P.) and three disparate deglaciated localities are consistent with close limiting calibrated ¹⁴C ages, thereby supporting the validity of our ³⁶Cl production rates integrated over the last 15,500 cal yr between latitudes of 46.5° and 51°N. Although our production rates are internally consistent and yield reasonable exposure ages for other localities, there nevertheless are significant differences between these production rates and those of other investigators.     

Contents of Volume 24

Table of Contents

Contents of Volume 24     

Sea level rise and impacts on nearshore sedimentation: an overview

 Impacts on nearshore sedimentation arising from potential sea level change of the magnitude predicted in Intergovernmental Panel on Climatic Change scenarios associated with global warming are reviewed. For sandy duned coasts, the obvious sedimentation impacts include potential erosion of coastal dunes with implied deposition of the eroded material in the nearshore, possible deepening of embayments, and flooding of wetlands. For the sandy coasts a number of two-dimensional models are available for predicting shoreline change, but there are significant difficulties in applying Bruun-type models for dune erosion and assessment of sediment redistribution over the inner shelf, and for predicting the amount of shoreline retreat for a given rate of sea level rise. If the beach profile contains excessive sand relative to its equilibrium profile, sensu Dean (1991), then shoreline retreat may not occur upon sea level rise. From the evidence of Kiel Bay, at least in these semi-enclosed basin types, it is during major transgressions that maximum deposition in adjacent basins occurs, due to the sea eroding weakly consolidated and weathered surface regolith. But at the same time climatic patterns were re-adjusting and probably contributed to maximum deposition in adjacent shelf and basins below wave base. Received: 16 June 1995 / Accepted: 29 January 1996     

The Makassar Strait Tsunamigenic Region,Indonesia

The Makassar Strait region has had the highest frequency of historical tsunamievents for Indonesia. The strait has a seismic activity due to the convergenceof four tectonic plates that produces a complex mixture of structures. The maintsunamigenic features in the Makassar Strait are the Palu-Koro and Pasternostertransform fault zones, which form the boundaries of the Makassar trough.Analysis of the seismicity, tectonics and historic tsunami events indicatesthat the two fault zones have different tsunami generating characteristics.The Palu-Koro fault zone involves shallow thrust earthquakes that generatetsunami that have magnitudes that are consistent with the earthquakemagnitudes. The Pasternoster fault zone involves shallower strike-slipearthquakes that produce tsunami magnitudes larger than would normallybe expected for the earthquake magnitude. The most likely cause for theincreased tsunami energy is considered to be submarine landslidesassociated with the earthquakes. Earthquakes from both fault zonesappear to cause subsidence of the west coast of Sulawesi Island.The available data were used to construct a tsunami hazard map whichidentifies the highest risk along the west coast of Sulawesi Island.The opposite side of the Makassar Strait has a lower risk because it isfurther from the historic tsunami source regions along the Sulawesicoast, and because the continental shelf dissipates tsunami wave energy.The greatest tsunami risk for the Makassar Strait is attributed tolocally generated tsunami due to the very short travel times.     

Tsunami Hazard for the Auckland Region and Hauraki Gulf,New Zealand

The Hauraki Gulf is a semi-enclosed sea next to the largest population centre in New Zealand, the Auckland metropolitan region. The potential tsunami hazard is of concern to regional and local planners around the Hauraki Gulf. The Hauraki Gulf has recorded 11 tsunamis and one meteorological tsunami (rissaga) since 1840.The historical tsunami data are relatively sparse, particularly for the largest events in 1868 and 1883. Moreover, local sources may produce damaging tsunamis but none has occurred during recorded history. Therefore numerical modelling of potential tsunami events provides a powerful tool to obtain data for planning purposes. Three main scenarios have been identified for numerical modelling:1. A teletsunami event from an earthquake off the West Coast of South America. Historically this region has produced the largest teletsunamis in the Hauraki Gulf.2. A tsunami generated by a local earthquake along the Kerepehi Fault. This fault bisects the Gulf, has been active during the last century at the southern inland end, and is overlain by a considerable thickness of soft sediment that may amplify the seismic waves.3. A tsunami generated by a volcanic eruption within the Auckland Volcanic Field. This field has involved a series of mainly monogenetic basaltic eruptions over the last 140,000 years. Many of these eruptions have involved phreatomagmatic eruptions around the coastal margins, or within the shallow waters close to Auckland.     

Aspects of asperity-surface interaction and surface damage of rocks during experimental frictional sliding

Summary Mechanisms for the dissipation of energy during the frictional sliding of rocks includes brittle fracture, plastic deformation, frictional heating, and elastic distortion. The first three energy sinks are manifested by surface damage during frictional sliding. Normal load, temperature, and the velocity of the sliding surfaces as well as surface roughness and hardness all influence the nature of surface damage which includes the generation of structures such as wear grooves, gouge, and welded particles.Lamont-Doherty Geological Observatory Contribution No. 2620.     

Influence of reproductive activity on toxicity of petroleum hydrocarbons to ghost crabs

Reproductively active ghost crabs appear to be more susceptible to oil pollution than non-active individuals, probably as a consequence of lowered energy reserves. Uptake of hydrocarbons over the 96-h exposure periods was more or less limited to the gill tissue. A relative measure—the ‘aromatic ratio’ — is suggested as a possible means of assessing bioaccumulation.     

The nature of deformation within the outer limits of the central appalachian foreland fold and thrust belt in New York state

Residual strain, a self-equilibrating recoverable strain that remains in rocks even after external forces and moments are removed, is found NNW of the folded Appalachian plateau in the Devonian Onondaga limestone and the Silurian Lockport dolomite and Grimsby sandstone of western New York. This residual strain is manifest upon overcoring by a NNW directed maximum expansion of the limestone and sandstone and a random maximum expansion of the dolomite. Strains, recorded with strain gauge rosettes bonded to outcrops, are as high as 200 με (microstrain). Double overcoring of the sandstone and dolomite relieves smaller strains of the same orientation as the initial overcore. X-ray analysis of the Grimsby sandstone shows that the elastic residual strain locked in quartz grains is characterized by a NE principal extension of 60 με and a 10–30 με NW principal compression oriented 30° counterclockwise from the NNW compression indicated by overcoring. Sonic velocity tests on samples in the lab indicate that Grimsby sandstone is anisotropic with a NNW maximum P-wave velocity of 4.05 km/sec. This anisotropy correlates with the residual strain in Grimsby sandstone. Mechanical twinning of calcite within both the Onondaga limestone and Grimsby sandstone indicates that the rock contains a permanent compressive strain of less than 2% in the NNW direction. The permanent strain becomes progressively smaller in a series of samples from Syracuse to Buffalo, New York. The development of solution cleavage in Onondaga limestone also indicates a NNW compression. No evidence of permanent strain was found in the dolomite. The NNW compression of the limestone and sandstone is normal to the fold axes of the Appalachian foreland fold and thrust belt. This geometric relationship indicates that the residual strain well beyond the outermost Appalachian folds was caused by the same tectonic stresses responsible for folding, the Appalachians during the late Paleozoic. Strain within the Appalachian plateau below the Silurian salt horizon suggests either the presence of a second décollement in, perhaps, Ordovician shales or a general NNW shortening of the crust under the Appalachian plateau.