Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 30 of 35
Full-Text Articles in Entire DC Network
Helium, Neon, And Tritium In The Black Sea, Z. Top, W. B. Clarke
Helium, Neon, And Tritium In The Black Sea, Z. Top, W. B. Clarke
Journal of Marine Research
Measurements of the 3He/4He ratio, and concentrations of helium, neon, and tritium have been made in samples collected at station 1355 in the Black Sea during the 1975 cruise of R/V Chain. Helium concentrations increase rapidly from 400 m to about 1000 m and then less rapidly below 1000 m. The maximum He concentration excess is about 16% above solubility equilibrium. Neon concentrations are constant, within a few percent of solubility equilibrium, below 400 m. The He-Ne data thus clearly indicate a large component of radiogenic 4He in the deep water from decay of U …
Effect Of Sea Ice Meltwater On The Alkalinity Of Seawater, E. P. Jones, A. R. Coote, E. M. Levy
Effect Of Sea Ice Meltwater On The Alkalinity Of Seawater, E. P. Jones, A. R. Coote, E. M. Levy
Journal of Marine Research
Alkalinity values in the top few hundred meters in Baffin Bay were about 100 μeq kg—1 above those expected from deeper values when the effect of salinity is removed. This “excess” alkalinity is attributed to calcium carbonate that precipitated from brines in sea ice and was subsequently reintroduced into the water column when the ice melted. The “excess” alkalinity is then used to estimate the amount of sea ice meltwater formed in Baffin Bay.
Vertical Flux Of Fatty Acids In The North Atlantic Ocean, Hein J. W. De Baar, John W. Farrington, Stuart G. Wakeham
Vertical Flux Of Fatty Acids In The North Atlantic Ocean, Hein J. W. De Baar, John W. Farrington, Stuart G. Wakeham
Journal of Marine Research
The quantitative and qualitative composition of fatty acids in particulate material collected in traps deployed during 98 days at 389, 988, 3755 and 5068 m depths in the equatorial North Atlantic was determined. The fatty acid composition indicates a predominantly marine source (14:0, 16:0, 16:1, 18:0, 18:1, 20:5, 20:4, 22:6, 22:5) with possibly a minor terrigenous component in the bathypelagic traps. The vertical fluxes of fatty acids and lipids decrease rapidly with depth. The rate of net loss of carboxylic acids increases with number of double bonds and decreases with number of carbon atoms. Iso- and anteiso- as well as …
Toxic Binding Of Cupric Ion By Marine Phytoplankton, Jerome Gavis
Toxic Binding Of Cupric Ion By Marine Phytoplankton, Jerome Gavis
Journal of Marine Research
The data presented by Gavis et al. (1981, J. Mar. Res., 39, 315–333) for the specific growth rate of phytoplankton in nutrient replete medium as a function of cupric ion activity can be described quantitatively by equations that relate the equilibrium binding of cupric ions to a cell receptor site. Statistically significant conditional binding constants could be estimated from the data for at least eight clones among three species. One clone could bind only one cupric ion per site. The others could bind a maximum of two cupric ions per site. For one of these clones K1 > K2 …
Westward Propagation Of Short-Term Climatic Anomalies In The Western North Pacific Ocean From 1964-1974, Warren B. White
Westward Propagation Of Short-Term Climatic Anomalies In The Western North Pacific Ocean From 1964-1974, Warren B. White
Journal of Marine Research
Short-term climatic anomalies in the surface dynamic height (O/400 db) structure of the western North Pacific from 1964-1974 are investigated on a seasonal basis for propagational character. From the equator to 32.5N, negative dynamic height anomalies occurred in 1965, 1969 and 1972, approximately every three years, associated with E1 Nino events in the eastern tropical Pacific (Wyrtki, 1977). The decorrelation time scale of these short-term climatic anomalies was independent of latitude (i.e., 6-9 months), but the decorrelation longitude scale decreased poleward; i.e., from 10° longitude at 7.5N to 5° longitude at 32.5N. Time/longitude correlation studies find these anomalies to have …
Tidally Generated High-Frequency Internal Wave Packets And Their Effects On Plankton In Massachussetts Bay, Loren R. Haury, Peter H. Wiebe, Marshall O. Orr, Melbourne G. Briscoe
Tidally Generated High-Frequency Internal Wave Packets And Their Effects On Plankton In Massachussetts Bay, Loren R. Haury, Peter H. Wiebe, Marshall O. Orr, Melbourne G. Briscoe
Journal of Marine Research
Tidally generated internal wave packets occur twice a day during late summer in Massachusetts Bay, U.S.A. The packets are formed at Stellwagen Bank and propagate into the Bay at about 60 cm sec—1; they dissipate in shallow water at the western side of the Bay. The dominant waves in packets have lengths of about 300 m, periods of between 8 and 10 min, and amplitudes of up to 30 m. Overturning of the waves has been observed acoustically over Stellwagen Bank, in the deep (80 m) waters in the center of the Bay, and during dissipation in shallow …
Quasi-Lagrangian Structure And Variability Of The Subtropical Western North Atlantic Circulation, Stephen C. Riser, H. Thomas Rossby
Quasi-Lagrangian Structure And Variability Of The Subtropical Western North Atlantic Circulation, Stephen C. Riser, H. Thomas Rossby
Journal of Marine Research
A large body of quasi-Lagrangian trajectory (SOFAR float) data collected from 1976-1979 from 700 m and 2000 m in the western North Atlantic is examined, and it is shown that the character of the trajectories varies markedly over regions as small as a few degrees of latitude and longitude. Kinetic energy increases to the north and west in the basin at both levels. At 700 m a large northwest energy gradient is present between 30N and 31N at 70W. At 2000 m kinetic energy increases to the north and west with the largest gradients very near to the Blake Escarpment …
Benthos Biomass And Oxygen Deficiency In The Upwelling System Off Peru, Rutger Rosenberg, Wolf E. Arntz, Esmeralda Chumán De Flores, Luis A. Flores, Guido Carbajal, Imme Finger, Juán Tarazona
Benthos Biomass And Oxygen Deficiency In The Upwelling System Off Peru, Rutger Rosenberg, Wolf E. Arntz, Esmeralda Chumán De Flores, Luis A. Flores, Guido Carbajal, Imme Finger, Juán Tarazona
Journal of Marine Research
Data are presented on macrobenthic (≥ 1 mm) biomass and species composition, sulfur bacteria (Thioploca), demersal fish catches, organic content of sediment and dissolved oxygen at 65 stations (35-360 m) along the upwelling area off north Peru in 1980-1981. Oxygen concentration close to the bottom was high only down to about 20 m depth and at 20-700 m it was generally < 0.8 ml l−1. Organic content of sediment increased significantly with water depth. Macrofauna were found at all stations with a general dominance of small polychaetes. Macrofaunal biomass showed a significant positive correlation with oxygen concentration; below 0.6 ml …
Light-Shade Adaptation And Vertical Mixing Of Marine Phytoplankton: A Comparative Field Study, Paul G. Falkowski
Light-Shade Adaptation And Vertical Mixing Of Marine Phytoplankton: A Comparative Field Study, Paul G. Falkowski
Journal of Marine Research
The hypothesis is examined that the recent light history of phytoplankton contains information about vertical mixing processes in the euphotic zone. Chlorophyll/P700 ratios are used to estimate the degree of light or shade adaptation in natural phytoplankton communities. Along with information about the time- and light-dependent rates of change of chlorophyll/P700 ratios, a model is presented to estimate how recently populations at the surface were at the 1% light depth and vice versa. The model is based on first-order kinetics and employs a temperature correction. The model is used to estimate vertical displacement rates (i.e., piston velocities) on …
Control Of Seagrass Communities And Sediment Distribution By Callianassa (Crustacea, Thalassinidea) Bioturbation, Thomas H. Suchanek
Control Of Seagrass Communities And Sediment Distribution By Callianassa (Crustacea, Thalassinidea) Bioturbation, Thomas H. Suchanek
Journal of Marine Research
Shallow tropical lagoons at St. Croix, U.S. Virgin Islands were found to have high densities of the ghost shrimp Callianassa spp. The ecology of four species of Callianassa is discussed: C. acanthochirus, C. longiventris, C. rathbunae and C. quadracuta. The first two species capture and store in their burrows drifting detritus of seagrass and algae. The latter two species build volcano-shaped mounds of ejected sediment during feeding and burrowing. Massive quantities of sediment (up to 2.59 kg/m2/day) are funneled into subsurface galleries, gleaned for organic material and sorted. Fine grains (< 1.4 mm diam.) are then pumped back up to the surface forming mounds. Coarse-grained material (≥ 1.4 mm) such as shell debris and coral fragments are not pumped back to the surface, but are stored in many deep chambers which extend > 1.5 m below the sediment surface. In cross-section, cores …
Vertical Motion Of The Thermocline, Nitracline And Chlorophyll Maximum Layers In Relation To Currents On The Southern California Shelf, J. J. Cullen, E. Stewart, E. Renger, R. W. Eppley, C. D. Winant
Vertical Motion Of The Thermocline, Nitracline And Chlorophyll Maximum Layers In Relation To Currents On The Southern California Shelf, J. J. Cullen, E. Stewart, E. Renger, R. W. Eppley, C. D. Winant
Journal of Marine Research
A continuous four-day time series of nitrate concentration, temperature, chlorophyll fluorescence, and currents, sampled at fixed depths, revealed that distributions of temperature and nitrate could be accounted for by vertical motions in the water column associated with the semidiurnal internal tide and internal waves. A probable mixing event was observed: the transport of nitrate into the surface-layer associated with shear instabilities generated by internal waves. On temporal scales of less than a few hours, the variation of chlorophyll fluorescence could also be explained by vertical advection. However, on longer scales, swimming behavior of the phytoplankton assemblage (dominated by Ceratium spp. …
Observations On The Degradation Of Biogenic Material In The Deep Ocean With Implications On Accuracy Of Sediment Trap Fluxes, Wilford D. Gardner, Kenneth R. Hinga, John Marra
Observations On The Degradation Of Biogenic Material In The Deep Ocean With Implications On Accuracy Of Sediment Trap Fluxes, Wilford D. Gardner, Kenneth R. Hinga, John Marra
Journal of Marine Research
The results of several observations and experiments indicate that the decay of organic material inside and outside of sediment traps in the deep ocean is on the order of 0.1-1.0% day−. These results must be considered when using sediment traps to determine the flux of organic material through the water column. The effectiveness of poisons in traps has not been adequately determined since the concentration of poisons in traps has not been monitored. Even traps containing poison may lose organic matter through leaching or from rapid grazing. A model is presented to quantify the loss of organic carbon …
The Importance Of The Diffusive Permeability Of Animal Burrow Linings In Determining Marine Sediment Chemistry, Robert C. Aller
The Importance Of The Diffusive Permeability Of Animal Burrow Linings In Determining Marine Sediment Chemistry, Robert C. Aller
Journal of Marine Research
Many of the abundant burrows formed by animals in marine sediments are lined with thin layers of organic material. The permeability of these linings to solute diffusion can be an important determinant of the chemical composition of surrounding sediment and the burrow habitat. Measurement of the diffusive permeability of burrow linings from 8 species of marine invertebrates indicates that the diffusion coefficients of small inorganic solutes within linings are ∼ 10-40% that in free solution. The diffusion of anions, represented by Br−, is hindered somewhat relative to cations, represented by NH4+, indicating that linings have …
Oceanic Property Transport, Lagrangian Particle Statistics, And Their Prediction, R. E. Davis
Oceanic Property Transport, Lagrangian Particle Statistics, And Their Prediction, R. E. Davis
Journal of Marine Research
The relationship between the transport of scalar properties and the statistics of material particle motion is examined. It is shown that evolution of the mean concentration field is determined by the statistics of single particles while two particle statistics describe the typical dispersal of individual property clouds. It is argued that oceanic observations of quasi-Lagrangian floats provide a useful and direct description of lateral advection and eddy dispersal. A simple model for predicting statistics of particle dispersal from Eulerian statistics of velocity is advanced. This model is tested against simulations of particle motion in random two-dimensional velocity fields with prescribed …
Why Is There No Deep Water Formed In The North Pacific?, Bruce A. Warren
Why Is There No Deep Water Formed In The North Pacific?, Bruce A. Warren
Journal of Marine Research
According to climatological data, the low salinity of near-surface water in the northern North Pacific, which reduces its density so much as to prevent sinking to great depth there, is due to the small regional evaporation rate (which allows a substantial net freshwater input to the surface layer from precipitation and runoff), in combination with the small rate of flow through the surface layer (which amplifies the effect of the freshwater flux on the salinity). The low evaporation rate is due in turn to the relatively low surface temperature (decreasing the specific humidity of the air at the air-sea interface), …
The Effect Of Pressure On The Thermodynamic Properties Of Seawater, Frank J. Millero, Donald R. Schreiber
The Effect Of Pressure On The Thermodynamic Properties Of Seawater, Frank J. Millero, Donald R. Schreiber
Journal of Marine Research
For many thermodynamic calculations in oceanography it is necessary to know the effect of pressure (or depth) on various thermodynamic properties. … Recently, a new equation of state for sea-water (Millero et al., 1980; Millero and Poisson, 1981) has been adopted by the UNESCO/ICES/IAPSO joint panel on oceanographic tables and standards. By appropriate differentiation of this equation of state, it is possible to determine the pressure derivatives for the specific volume of seawater solutions. To estimate the effect of pressure on the partial molal thermochemical properties (Millero and Leung, 1976), it is necessary to know the partial molal volumes of"sea …
Lagrangian Eddy Statistics From Surface Drifters In The Eastern North Atlantic, Alain Colin De Verdiere
Lagrangian Eddy Statistics From Surface Drifters In The Eastern North Atlantic, Alain Colin De Verdiere
Journal of Marine Research
In 1976–1977, 16 surface drifters were seeded regularly in an area about 100 km in diameter, providing a good opportunity to study diffusion induced by the mesoscale eddies present in this part of the eastern North Atlantic. It is found herein that Taylor's formula relating the diffusivity (rate of dispersion) of marked fluid parcels to the integral of the Lagrangian correlation function is accurate up to 30 days. The diffusivity, initially zero, reaches a plateau after about 10 days. The diffusivities associated with the time scale of the energy containing eddies (30 days) are 2.3 107 cm2/s …
Synoptic Estimates Of Air-Sea Fluxes, Richard F. Marsden, Stephen Pond
Synoptic Estimates Of Air-Sea Fluxes, Richard F. Marsden, Stephen Pond
Journal of Marine Research
Synoptic and climatological dynamic studies generally rely on bulk aerodynamic flux formulae to describe air-sea heat and momentum exchange on synoptic and climatological scales. Barometric pressure maps (which involve an intrinsic spatial and temporal averaging of the wind) and wind roses provide two sources of spatial and temporal wind information for flux calculations. Several investigators have shown that time-averaged estimates of the fluxes based on vector-averaged winds systematically underestimate the actual time-averaged fluxes.Using surface meteorological observations from 9 weatherstations in the North Atlantic Ocean and 2 weatherstations in the North Pacific Ocean, the three hourly stresses, latent heat fluxes and …
On The Mean Dynamical Balances Of The Gulf Stream Recirculation Zone, James C. Mcwilliams
On The Mean Dynamical Balances Of The Gulf Stream Recirculation Zone, James C. Mcwilliams
Journal of Marine Research
The time mean circulation is analyzed at a site on the southern edge of the Gulf Stream Recirculation Zone (31N, 70W) from data taken in the POLYMODE Local Dynamics Experiment. Additional mean quantities are described from a combination of dynamical assertions and inferences. The mean vorticity balance is examined to infer the mean vertical velocity and eddy relative vorticity flux divergence. The vertical velocity is found to be mostly upward and an order of magnitude larger than the downward surface Ekman pumping. In the mean heat, salt, density, and potential vorticity budgets, the mean advections of these quantities are nonzero, …
On The Migration Of Isolated Eddies With Application To Gulf Stream Rings, Doron Nof
On The Migration Of Isolated Eddies With Application To Gulf Stream Rings, Doron Nof
Journal of Marine Research
An analytical model describing the β-induced drift of isolated nonlinear eddies such as the cold- and warm-core rings observed in the Atlantic Ocean is proposed. The ocean is approximated by two layers and attention is focused on frictionless upper ocean eddies whose surface area is finite. These isolated eddies are nonlinear in the sense that (a) the corresponding Rossby number is relatively large and (b) the interface vertical displacements ("amplitudes") are comparable to the upper layer undisturbed depth. Solutions for steadily translating eddies which carry their entire mass as they move are sought. Examination of the problem in a …
Equatorial Ocean Response To Growing And Moving Wind Systems With Application To The Atlantic, R. H. Weisberg, T. Y. Tang
Equatorial Ocean Response To Growing And Moving Wind Systems With Application To The Atlantic, R. H. Weisberg, T. Y. Tang
Journal of Marine Research
Investigation is made into the response of an equatorial ocean to growing and moving zonal wind systems as motivated by observations of maximum upwelling central to the equatorial Atlantic basin and westward progressing thermal and momentum signatures near the surface. Analytical solutions to the linear, reduced gravity, equatorial β-plane equations of motion subject to a long wave approximation are given for three easterly forcing functions: 1) linearly expanding fetch with constant stress, 2) linearly expanding fetch and stress, and 3) constant fetch and stress, translating westward. The results, as they may relate to the equatorial Atlantic Ocean, are discussed.
Exploratory Observations Of Abyssal Currents In The South Atlantic Near Vema Channel, William J. Schmitz Jr., Nelson G. Hogg
Exploratory Observations Of Abyssal Currents In The South Atlantic Near Vema Channel, William J. Schmitz Jr., Nelson G. Hogg
Journal of Marine Research
Vema Channel (nominal location 30S, 40W) is a major passage for the flow of Antarctic Bottom Water on its way northward from the Argentine Basin to the Brazil Basin. New data based on approximately year-long current meter deployments at abyssal depths yield mean or time-averaged kinetic energies as strong as 240 cm2s−2, and eddy kinetic energies from 8 to 40 cm2s−2. We observe a persistent northward flow of AABW with maximum speed near 40 cm s−1, as is found at abyssal depths in the vicinity of the Gulf Stream. The …
Modelling The Advection Of Vertically Migrating Shrimp Larvae, Peter C. Rothlisberg, John A. Church, Andrew M. G. Forbes
Modelling The Advection Of Vertically Migrating Shrimp Larvae, Peter C. Rothlisberg, John A. Church, Andrew M. G. Forbes
Journal of Marine Research
The role of larval advection in determining the complex, large-scale patterns of immigration of penaeid postlarvae in the Gulf of Carpentaria is investigated by modelling the interaction between diurnal vertical migration of larvae with wind-forced and tidal currents. Eight vertical migration schemes are modelled in which both the timing of the migration and the position of the larvae in the water column are varied. These schemes are then coupled with both two-dimensional and three-dimensional models of the currents of the Gulf, to examine horizontal advection of larvae. When the larvae migrate vertically with a diurnal period, their horizontal advection is …
Regulation Of Phytoplankton Communities By Physical Processes In Upwelling Ecosystems, Walker O. Smith, George W. Heburn, Richard T. Barber, James J. O'Brien
Regulation Of Phytoplankton Communities By Physical Processes In Upwelling Ecosystems, Walker O. Smith, George W. Heburn, Richard T. Barber, James J. O'Brien
Journal of Marine Research
Sinking rates of particles were superimposed on the x-z-t current field observed at 15S off the coast of San Juan, Peru in March–May, 1977 to calculate particle trajectories in the upwelling circulation. Vertical velocities were calculated by a modified variational objective analysis technique using the measured onshore and longshore currents in conjunction with the physical constraint of mass continuity. The calculated vertical flow showed considerable temporal and spatial variability, with the mean vertical transport varying by two orders of magnitude over the 16 km wide continental shelf. Changes in direction occurred rapidly (within 24 h) as has been observed for …
Enhanced Growth Of A Filter-Feeding Bivalve By A Deposit-Feeding Polychaete By Means Of Nutrient Regeneration, James R. Weinberg, Robert B. Whitlatch
Enhanced Growth Of A Filter-Feeding Bivalve By A Deposit-Feeding Polychaete By Means Of Nutrient Regeneration, James R. Weinberg, Robert B. Whitlatch
Journal of Marine Research
Sediment reworking and tube irrigation by the deposit-feeding polychaete, Clymenella torquata, reduced the quantity of particulate organic matter (POM) at the sediment-water interface and increased concentrations of dissolved nutrients (nitrite, ammonia, silicate, phosphate) in the water overlying laboratory microcosms. To determine the effect of these changes on growth of the filter-feeding bivalve, Gemma gemma, clams of the same initial size were grown under different laboratory conditions, representing all combinations of the following three treatments: (a) presence or absence of light, (b) presence or absence of C. torquata, and (c) proximity to C. torquata (clams living in sediment with worms or …
Comparative Biogeochemistry Of Water In Intertidal Onuphis (Polychaeta) And Upogebia (Crustacea) Burrows: Temporal Patterns And Causes, Robert C. Aller, Josephine Y. Yingst, William J. Ullman
Comparative Biogeochemistry Of Water In Intertidal Onuphis (Polychaeta) And Upogebia (Crustacea) Burrows: Temporal Patterns And Causes, Robert C. Aller, Josephine Y. Yingst, William J. Ullman
Journal of Marine Research
The burrows of macrobenthos represent an important class of sedimentary microenvironments which significantly influence chemical, biological, and physical characteristics of a deposit. In intertidal regions, the time-dependent changes in composition during ebb-tide of water contained in burrows is a sensitive indicator of biogenic and abiogenic chemical reactions in burrow walls and adjacent sediment. Comparison of time series water samples taken from Onuphis jenneri (polychaete) and Upogebia affinis (crustacean) burrows in the same tidal flat demonstrate substantial differences in biogeochemical microenvironments despite the spatial proximity of the two species. Both types of burrows are influenced by the same general kinds of …
On The Variability Of The Loop Current In The Gulf Of Mexico, W. Sturges, J. C. Evans
On The Variability Of The Loop Current In The Gulf Of Mexico, W. Sturges, J. C. Evans
Journal of Marine Research
It is of considerable interest to know to what extent offshore currents may drive flows on the continental shelf. We have used the northernmost position of the Loop Current, from hydrographic data, to piece together a time series 13 years long. This record samples the lowest frequencies well but undersamples the amplitude of variations with periods of ∼8 months by a factor of 2. The "annual" variation of the Loop Current appears to be a relatively broad spectral peak rather than a sharp spectral line. We find as much power at periods near 30 months as at periods near a …
A Dead Central American Coral Reef Tract: Possible Link With The Little Ice Age, Peter W. Glynn, Ellen M. Druffel, Robert B. Dunbar
A Dead Central American Coral Reef Tract: Possible Link With The Little Ice Age, Peter W. Glynn, Ellen M. Druffel, Robert B. Dunbar
Journal of Marine Research
Radiocarbon analyses, stable isotopic measurements and extensive field observations were made of coral reefs off the Pacific coast of Costa Rica and Panama. These analyses showed that live coral reefs in the Gulf of Papagayo, Costa Rica, were severely depleted in number, size and variety of species, compared to reefs in the major upwelling zone of the Gulf of Panama. Coral growth in the Gulf of Papagayo consisted mainly of dead reefs that died from 150–300 years B.P. The δ18O records revealed that most of the dead reefs were exposed to relatively cool water immediately preceding death. We …
Tidal Currents, Winds And The Morphology Of Phytoplankton Spatial Structures, M. Levasseur, J. C. Therriault, L. Legendre
Tidal Currents, Winds And The Morphology Of Phytoplankton Spatial Structures, M. Levasseur, J. C. Therriault, L. Legendre
Journal of Marine Research
Chlorophyll a, nutrients and salinity distributions were studied at two spatial scales (10 cm and 0.25 to 2.5 km) in the St. Lawrence Estuary (Quebec, Canada), in order to investigate the role of tidal currents and winds in the formation and maintenance of spatial structures. Data were collected according to a synoptic sampling pattern using three sampling platforms simultaneously, and they were analyzed using analysis of variance. The sampling pattern was repeated on four occasions during July 1980.Analyses of variance indicated significant spatial heterogeneities of about the same magnitude at the two scales studied for chlorophyll and nutrients, whereas …
The Relative Magnitude Of Biological And Physical Sediment Reworking In An Intertidal Community, Jonathan Grant
The Relative Magnitude Of Biological And Physical Sediment Reworking In An Intertidal Community, Jonathan Grant
Journal of Marine Research
Tidal sediment reworking was compared to biogenic reworking by benthic-feeding fishes and macrofaunal invertebrates on an intertidal sandflat in South Carolina. Flume-determined rates of ripple migration were combined with field measurements of current velocity to characterize physical reworking. Bioturbation by dasyatid rays was measured by counting newly formed feeding excavations at low tide. On both an areal and volumetric basis, ray reworking amounted to <1% of that reworked by ripple migration. Approximately 30% of the sediment surface was covered by feeding pits during the July maximum of ray activity, with only a small proportion of these newly formed per day. Sediment ingestion by the hemichordate Saccoglossus kowalevskii, was less important than ray bioturbation in comparison to tidal sediment reworking. Sediment displacement by free-burrowing haustoriid amphipods was estimated to be important relative to other biogenic sources, but still <1% of the disturbance produced by bedform migration. However, an abundant infaunal species, the polychaete Paraonis fulgens, …