Shallow Marine Embayment Research Articles

Food uptake in the mixotrophic Dinophysis acuminata

Evidence of food uptake in the photosynthetic genus Dinophysis comes solely from the presence of food vacuoles, as no photosynthetic cells have ever been observed in the act of feeding. We examined the feeding ecology of D. acuminata in natural populations and under laboratory conditions. Using depth‐integrated sampling of the water column, we determined the frequency of food vacuolated cells at 2‐h intervals over a 24‐h period in a shallow marine embayment. Food vacuoles in preserved cells were enumerated using Nomarski differential interference contrast microscopy; ultrastructural characters were recorded by transmission electron microscopy. A peak in the feeding activity was observed toward dusk for an abundant June population, with 26% of cells with at least one food vacuole. Mechanisms of concurrent carbon acquisition were evident from the presence of chloroplasts with starch grains and food vacuoles within the same cell. Vacuole content could not be identified. In a preliminary 2‐wk long simulated grazing experiment, a mixture of two hypothesized preys, Rhodomonas salina and Dunaliella tertiolecta, was offered to D. acuminata; the Dinophysis populations decreased steadily and at the same rate, whether food was present or not. The evaluation of the food vacuole frequency will be repeated in the coming season to verify the observed pattern, while grazing experiments will include a variety of food items and incubation conditions. Our current inability to successfully culture any photosynthetic Dinophysis limits ecophysiological approaches, either at the population or cellular level, to manipulation of field samples.Supported by National Institutes of Health Grant GM62126‐01A1.

Shallow marine tsunami deposits in Teluk Banten (NW Java, Indonesia), generated by the 1883 Krakatau eruption

Teluk Banten (TB) is a tropical shallow marine embayment with coral reef islands, close to the Krakatau volcanic complex. The 1883 Krakatau eruption generated a tsunami, which had a devastating effect on the neighboring coastal areas. The effects of the 1883 Krakatau eruption and the associated tsunami on the bottom sediments in TB are assessed using textural, compositional and 210Pb geochronological data. An important diagnostic criterion consists of the occurrence of tephra conform descriptions of the 1883 eruption tephra. The tsunamite consists of a sandy layer with abundant reworked shell and other carbonate fragments. Coarse components in the tsunamite consist of locally derived material eroded from the seabed. Land-derived components are incorporated in the tsunamite only in close proximity to the coast. The tsunamite is thickest in localized areas of the central part of the bay. Along the northern open sea-facing slope of TB, the tsunamite is relatively thin (<7 cm thick) but well-preserved, as little post-depositional modifications have occurred. In the eastern bay area, recent erosion since the redirection of the Ciujung River in the 1920s has removed the Krakatau tsunamite. Along the west coast of TB, the only signature of the 1883 Krakatau eruption consists of tephra, and evidence for a high-energy event is lacking. Presumably, the western area was sheltered from the tsunami wave coming from the northwest. At the shallower stations with low accumulation rates, the tephra has been thoroughly mixed by bioturbation.

Characterization and FATE of PAH-contaminated sediments at the Wyckoff/Eagle Harbor Superfund Site.

Eagle Harbor, a shallow marine embayment of Bainbridge Island, WA approximately 10 miles west of Seattle, WA), was formerly the site of the Wyckoff wood-treatment facility. The facility used large quantities of creosote in its wood-treating processes from the early 1900s to 1988. Historical creosote seepage into the harbor resulted in substantial accumulation of polycyclic aromatic hydrocarbon (PAH) contamination in the harbor sediments over time. This investigation focused on the distribution and fate of the PAH-contaminated harbor sediments. Analyses of 10 sediment cores using total petroleum hydrocarbon (TPH) fingerprinting, the distribution of 50 PAH analytes, and sediment age dating revealed the contributions of three distinct sources of PAHs to sediment contamination in the harbor during various periods over the past 100 years; namely, creosote, urban runoff, and natural background. Surface sediments (upper 20-30 cm) in the cores closestto the Wyckoff wood-treatment facility and southeast of an existing cap were dominated by urban runoff and weathered creosote; the deeper sediments (> 30 cm) were heavily contaminated with relatively unweathered creosote and some pure-phase creosote. Cores located the furthest from the area of contamination, in the center of the harbor, were dominated by urban runoff, showed no signs of creosote contamination, and had much lower PAH and TPH concentrations than those adjacent to the facility. In the four cores in the center of the Harbor, farthest from the former Wyckoff facility, PAH concentrations increased significantly (p < 0.01) with proximity to the northern shore of the harbor, which is more heavily developed than the southern shore and is where all automobile traffic enters and exits the island through the Bainbridge Island ferry terminal. Deeper portions of these cores were contaminated primarily with natural background PAHs, likely representing preurbanization sediments. Sedimentation rates ranged from 0.54 to 1.10 gm/ cm2 in the four cores located in the middle of the harbor, and for the single nearshore core that could be used to calculate sedimentation rates. Recognition that urban runoff has been a fairly consistent and ongoing source of PAHs to the harbor's sediments for the past 50-70 years may influence future sediment management decisions for this site with respect to long-term monitoring of surface sediments to assess cap performance. The results provided information on the ability of Eagle Harbor sediments to recover under natural conditions, identified the occurrence of creosote-derived PAH weathering in off-cap surface sediments, and distinguished between these distinct PAH sources in the harbor (creosote, urban runoff, and natural background).

Biology and fishery of pilchard, Sardinops sagax (Clupeidae), within a large south-eastern Australian bay

Length–frequency and maturity data of pilchards (Sardinops sagax) are described from monthly purse-seine commercial catch samples obtained in Port Phillip Bay (Victoria) between December 1994 and January 1997. These data, together with findings of a 12-month ichthyoplankton bay survey from September 1995 to August 1996, were used to determine the size at which pilchards recruit to the bay fishery and whether they spawn within this system. Monthly pilchard catch rates between January 1990 and June 1996 are also described and analysed in terms of environmental variables during that period. Results show that pilchards do not generally attain sexual maturity or spawn within the bay but use it as a nursery area, entering this system mostly as 0+ to 1+ year-o ld juveniles (4–12 cm fork length, FL) in late spring–early summer and returning to sea the following winter. This migration is supported by the marked seasonality in catch rates, which each year peak in March–May and are lowest in August–October. The seasonality was adequately explained by temperature lagged 2 months in a multivariate time-series model. Port Phillip Bay appears to be the only semi-enclosed, shallow marine embayment in temperate Australia that supports a substantial pilchard fishery that, in addition, is based predominantly on juveniles.

Nutrient fluxes measured by two types of benthic chamber

Comparisons were made between benthic nutrient fluxes in a shallow marine embayment measured by a sophisticated automated benthic chamber device and a much simpler design. Both devices have similar chamber dimensions. The sophisticated design can be deployed by line from a vessel, incorporates an sealed waterproof computer, uses one chamber and all operations are fully programmable; dissolved oxygen concentrations are electronically monitored every 6 min and stored by the computer. The simpler design incorporates three opaque and three clear chambers per site to investigate small-scale sediment differences and the effect of benthic photosynthetic production on fluxes; dissolved oxygen concentrations are electronically monitored every 10 min. within all chambers and stored in a data logger; the deployment and recovery and sampling operations other than for DO require the use of divers. Except where sediments differ greatly over a few metres, both chamber devices deliver similar results and indicate the consistency of the technique regardless of the design. The simpler design is limited by the need for diver deployment and sampling. An automated chamber array is recommended as the best way of measuring ‘patchy’ sediments

Stratigraphy of the Neill Klinter Group; a Lower – lower Middle Jurassic tidal embayment succession, Jameson Land, East Greenland

The sediments of the Neill Klinter Group of Jameson Land, East Greenland were deposited in a wide, shallow, wave, storm and tidally-influenced marine embayment situated at the western margin of the Jurassic seaway between Greenland and Norway. The group is formally defined and a new lithostratigraphic scheme is erected on the basis of recent sedimentological, biostratigraphic and sequence stratigraphic studies. The Neill Klinter Formation is changed to group rank; the Rævekløft, Gule Horn and Ostreaelv Members are revised and raised in status to formations, and the Sortehat Formation is redefined and included in the group. The Gule Horn Formation is divided into two new members and the Ostreaelv Formation into seven new members. The Neill Klinter Group is up to 450 m thick.&#x0D; Sandy and muddy material was transported into the embayment from source areas to the east, west and north. A number of sub-environments are represented in the succession, including: restricted and bioturbated offshore, storm-dominated offshore transition zone, wave and storm-dominated shoreface, storm-dominated sandy shoal, subtidal sand sheet, ebb-tidal delta, tidal channel, wave and storm-dominated lagoon, and ephemeral stream delta.&#x0D; The Neill Klinter Group consists of seven sequences and is characterised by a near absence of parasequences, interpreted as reflecting high influx rates of sand into the land-locked embayment. Continuous filling of accommodation space and erosion resulted in amalgamation of sedimentary packages, and poor development of facies cyclicity.

Spatial variability of tidal flats in response to wave exposure: examples from Strangford Lough, Co. Down, Northern Ireland

Abstract Strangford Lough is a shallow marine embayment, whose present form resulted from the late Glacial and Holocene marine erosion of a drumlinized coastal lowland platform. Constriction at the Lough mouth means that most waves are generated by wind blowing over restricted fetches. Tidal flats in the northern parts of Strangford Lough show variable morphology and sediment composition. Tidal flats on the up-wind margin are muddominated and located in an intact drowned drumlin landscape. Those on the downwind margins are sandy and exist in partly or wholly eroded former drumlin topography. Our preliminary results indicate strong control by wave exposure (mediated by fetch distance) over tidal flat sediments and morphology which has led to the formation of a series of spatially variable tidal flats within a single depositional basin. At the time scale of the Holocene, exposure to wave action appears to exert a major influence on tidal flat morphology in this sediment-limited setting though its long-term control of topographical change (seen here as variable extent of drumlin erosion) and the consequent and subsequent role of this topography in determining exposure to contemporary wave action.

A current‐activated sediment trap

A current‐activated sediment trap is described that collects particles based on preselected current speed and direction criteria. The collector incorporates a steep‐walled funnel, a motor‐driven carousel with sample cups, an absolute optical shaft encoder, and an acoustic current meter. A field trial of the trap was carried out in a shallow marine embayment over 3 d where it correctly positioned cups in response to tidal changes in current speed and direction. Particle organic content and sedimentation rates calculated over hourly intervals were similar to measurements with a standard sequential sampling trap over several hours when the two traps were deployed simultaneously.

Evolution of Holocene sedimentary bentonite in a shallow-marine embayment, Firth of Thames, New Zealand

Firth of Thames, northern North Island, New Zealand, is a low-wave energy, shallow (< 30 m depth) marine embayment that has accommodated at least 10 m of mud during the Holocene. Cores from the upper 5 m of this Holocene deposit have radiocarbon ages as old as 5300 yr B.P. and show that the muds consist mainly of silicic volcanic glass, smectite, volcanic rock fragments (ignimbrite, rhyolite, and andesite), and halloysite. A downcore decrease in the abundance of volcanic glass (from 55 to 10 wt% of bulk sediment) is matched by a downcore increase in the abundance of smectite (from a few to 42 wt% of bulk sediment). The smectite has a montmorillonite composition, and exhibits a crenulated, flake-like morphology. The degree of textural development and crystallinity of the smectite increase with sub-bottom depth. Sediments sampled from rivers draining the Hauraki Lowland, a catchment dominated by silicic pyroclastic and volcaniclastic deposits, are compositionally similar to the Firth of Thames marine muds, except that they lack smectite. This, together with the absence of smectite in adjacent shelf sediments and the downcore antipathetic relationship between glass and smectite content, supports an early diagenetic origin for the smectite from glass. The transformation is described by a two-stage model involving a combination of parabolic and linear kinetics, reflecting the hydration of glass and the formation of smectite, respectively. The model indicates the half-life for volcanic glass in the Firth of Thames is only 1500 years. Despite the fact that these smectite-rich muds have not evolved from the alteration of primary pyroclastic deposits, but rather from detrital reworked volcanic glass, we classify them as sedimentary bentonite. We suggest the mode of emplacement of the volcanic material is irrelevant to the name bentonite. Moreover, in contrast to many other studies of bentonite deposits, the Firth of Thames occurrence is different because it is thick (> 5 m), has a young (Holocene) age, and is forming in a shallow-marine setting (< 30 m) from the rapid alteration of glass to smectite, within only a few 1000 years. The abundance of detrital silicic volcanic glass supplied from the Hauraki Lowland catchment, currently up to 65% by weight of total sediment input, determines the abundance of smectite in the Firth of Thames.

Influence of phosphorus storage on the uptake of cadmium by the marine alga Macrocystis pyrifera

Seasonal changes in the concentrations of Cd and phosphate (P) in the macroalga Macrocystis pyrifera have been studied in Otago Harbour, a shallow marine embayment. Both components showed the same seasonal cycle, with concentration maxima during the austral winter (June–July) and summer periods (December–February) when growth of M. pyrifera was minimal. During these periods, cells contained significant quantities of electron‐dense polyphosphate bodies (PPBs). Culture experiments showed that Cd uptake from seawater media was greatly enhanced when PPBs were induced to form. With 0.44 µmol Cd kg−1 in the medium, cultures forming PPBs contained 40–50 times as much Cd in excess of controls as those grown at the same Cd concentration in which PPBs were not formed. With 44 µmol kg−1 in the medium, PPB‐forming cultures took up about twice as much Cd as those not forming PPBs. The incorporation of Cd into cellular PPBs may be an important mechanism for the uptake of this element even at natural Cd concentrations.

Learning from the past: Diatoms as palaeoecological indicators of changes in marine environments

The North Sea is seriously threatened by a variety of pollution sources. Terrestrially derived effluents are causing extensive environmental damage and changes to ecosystems of both the offshore and coastal waters. Coastal and estuarine communities are being lost to reclamation projects, and there is the future threat of rising sea level associaed with global warming. The spatial and temporal extent of recent anthropogenic changes are largely unknown due to the paucity of background information. The possible role of palaeoecological methodology in providing ‘reference levels’ against which current status can be compared, and their importance for restoration and policy decisions, are presented. The usefulness of diatoms as environmental indicators is illustrated. The extent of natural and anthropogenic changes on coastal habitats are demonstrated by reference to the Holocene evolution of the coastline of The Netherlands. Possible profitable areas for further research are outlined,e.g. a diatom nutrient calibration data set for shallow marine embayments.

Short-Term Community Transition and r Selection"in Shallow Marine Embayment Fauna from Pennsylvanian of North-Central Texas: ABSTRACT"

Community and size-frequency analyses were obtained for macrofauna from a thin fossiliferous interval within an otherwise barren shallow marine embayment facies in the East Mountain Shale (Strawn Group). Vertically contiguous sampling of this discrete unit allowed reconstruction of short-term community transition and detection of shifts in the population structure of two gastropod species (Glabrocingulum G. grayvillensis, Straparollus A. catilloides). These biological phenomena could be related to environmental shifts brought about by deltaic progradation.

The dynamic balance of manganese transport and diagenesis in the Otago Harbour, New Zealand

The input and internal cycling of manganese in the Otago Harbour, a shallow marine embayment, have been studied. Freshwater transport of dissolved and particulate Mn was measured during sustained steady flows and during a major flood event during which particulate mass transport increased by orders of magnitude. Flux calculations derived from these data revealed that input to the harbour system is dominated by particulate transport during flood events occupying a minor part of the flow record. In contrast, under average flow conditions the major input was in the form of dissolved Mn. Within the harbour, Mn transport in the water column was dominated by essentially conservative mixing of dissolved Mn formed through diagenetic remobilisation of riverine particulate Mn deposited in sediments in the upper basin of the harbour. The distribution of Mn in suspended matter showed a marked enrichment compared to bottom sediments indicative of oxidative precipitation of Mn(II) onto particle surfaces in the water column and/or selective resuspension processes. Within the margins of uncertainty in various flux estimates, the loss rate of Mn from the harbour balanced the terrestrial source function, illustrating the dynamics of Mn transport and diagenesis important to this element's oceanic geochemistry.

Hydrocarbons of the hypersaline basins of Shark Bay, Western Australia

Shark Bay is an 8000 sq. km shallow marine embayment on the western coast of Western Australia. The waters exhibit a well established salinity gradient from oceanic to hypersaline. The chemical assemblage of sediment hydrocarbons along the salinity gradient may be classified into two distinct chemogeographic types. Firstly, oceanic sediments contain n-alkanes and a suite of highly branched and branched/cyclic C 25 alkenes. Hypersaline sediments are characterised by a high relative abundance of a C 25H 50 alkene together with an analogous C 20H 40 alkene and its parent C 20H 42 alkene (2,6,10-trimethyl-7-(3-methylbutyl)-dodecane). A pair of alkanes C 21H 42 and C 22H 44 increase in concentration and relative abundance with depth. The hydrocarbons of the hypersaline basins are found in only trace amounts in oceanic sediments. These chemical signals are overlain by further input indicative of the immediate biotic community.

The sedimentary framework of northern Spencer Gulf, South Australia

Northern Spencer Gulf is the landward extremity of a shallow marine embayment which occupies a structural depression that overlies a major Precambrian lineament. Situated in a warm temperate climate, the low rainfall and high evaporation have created high salinities resulting in an hydrological inverse estuary. Modern sedimentation is dominantly biogenic carbonate to mixed terrigenous-carbonate. It is controlled by a mesotidal regime with occasional storm surges, minor wave activity, and a prolific growth of seagrass in shallow water. The skeletal detritus consists of bivalves, gastropods, forams, echinoids, coralline algae and bryozoa. The subtidal zone between 10–25 m is divided morphologically into two provinces. The wide southern part has a relatively smooth floor, but the northern part is narrower, and the seafloor is either scoured free of loose sediment, or covered with wide belts of megaripples. The subtidal zone between 0–10 m is everywhere dominated by seagrass meadows. The seagrasses are largely Posidonia australis and P. sinuosa and occupy broad depositional platforms, and discrete offshore banks. The seagrass meadows produce and trap mollusc/foram detritus, resulting in the accumulation of very poorly sorted, organically bound structureless carbonate muddy sand. Intertidal and supratidal zone sediments are very extensive. The intertidal zone includes bare sand flats or those covered by the seagrass Zostera. Dense mangroves ( Avicennia marina) from mean sea level to spring high-tide level are followed progressively by a halophytic (samphire) association and an Atriplex (saltbush) association. Extensive algal mats occur with the halophytes and extend into the mangrove forests. The sediments are muddy and only moderately calcareous. The supratidal zone consists mainly of bare carbonate flats, some stranded beach ridges, and coastal dunes. The carbonate flats contain discoidal gypsum crystals in weakly layered, fenestral, calcitic mud. Coastal changes during historic time are limited, and the dominant sedimentary regime in northern Spencer Gulf is the vertical growth of seagrass areas to form intertidal sand flats.

The taxonomic status, and isotopic evidence for paleoenvironments, of giant oysters from the Oligocene Te Kuiti Group, South Auckland, New Zealand

Abstract Close inspection of the morphologic characteristics of giant oysters from the Oligocene Te Kuiti Group indicates that they do not belong in any of the several genera so far assigned them in the literature, including the estuarine genus Crassostrea. They are most typical of the tribe Flemingostreini Stenzel, but without more extensive and specialist study it is premature to give them generic status, which might only perpetrate further taxonomic confusion. Carbon and oxygen isotopic analyses of the oyster shells, as well as independent evidence, suggest that oysters in: (1) the Mangakotuku Siltstone formed in a protected, shallow marine embayment, open only to the north, having locally restricted circulation, but mainly normal to only slightly reduced salinites, the light carbon in shells being derived more from the reaction with seawater of locally produced C02 from decomposition of abundant organic debris in the bottom sediments than from widespread dilution of seawater by freshwater; (2) the Wha...

The stratigraphy of the Gault of East Anglia

The lithological and faunal sequences observed in the Gault in cored boreholes in East Anglia are described, and the formation is divided into 19 distinctive beds that can be recognised throughout the region. The nature of the Gault overstep onto the London Platform is described: so too is the correlation between the argillaceous Gault and the red nodular limestones of the Red Chalk of north Norfolk. It is suggested that the Lower Gault of the northern part of East Anglia was deposited in a shallow marine embayment lying between the exposed Palaeozoic rocks of the London Platform in the south and a shoal of chamosite oolite sand (the Carstone) in the north.

Depositional Environments, Provenance, and Tectonic Framework: Upper Part of the Late Precambrian Mount Rogers Formation, Blue Ridge Province, Southwestern Virginia

ABSTRACT The Mount Rogers Formation is a thick (3,000 m) succession of late Precambrian sedimentary and volcanic rocks exposed along the northwestern flank of the Blue Ridge anticlinorium in southwestern Virginia. Probable contemporaneous equivalents include the Ocoee Series of Tennessee, the Grandfather Mountain and Ashe Formations of North Carolina, and the Swift Run and Lynchburg Formations of central Virginia. The upper third of the Mount Rogers Formation includes a wide range of rocks which, on the basis of sedimentary structures, composition, and texture are interpreted as glacial till, fluvial channel conglomerate, (varved?) lacustrine or shallow marine siltstone and shale (rhythmites), turbidite sandstone, and ice rafted pebbly mudstone. These rock types were deposited on piedmont fans and across braided floodplain areas which flanked an uplifted highland complex composed of igneous and metamorphic rocks that today constitute the Blue Ridge Basement Complex. Lakes or a shallow marine embayment lay further east in the area where the present core of the Blue Ridge anticlinorium is located. The depositional area of the Mount Rogers Formation may have originated during the early stages of rifting which preceded the opening of the Paleozoic Protoatlantic Ocean.

Stratigraphy and Paleoenvironments of Cretaceous Rocks, Mitchell Quadrangle, Oregon

Cretaceous marine and continental sedimentary rocks, of Albian and possibly Cenomanian ages, crop out in the south half of the Mitchell quadrangle in central Oregon. More than 70 sq mi of Cretaceous rocks is exposed along a northeast-trending, doubly plunging anticline. The sequence, 9,023 ft thick as described along three principal reference sections, lies with angular unconformity on Permian metasedimentary rocks, and is overlain unconformably by Tertiary lava flows and volcanic sedimentary rocks. In part, the rocks have been faulted complexly and there are numerous fault-controlled and randomly oriented intrusions of Tertiary age. These rocks are divided into two intertonguing formations. One, a widespread and thick sequence of marine mudstone with subordinate siltstone and sandstone, is defined herein as the Intertonguing intricately with the marine rocks are conglomerate and sandstone; these, predominantly of fluvial and deltaic origin, are defined herein as the Creek The total sequence consists of the Basal of the Hudspeth Formation, a thin sandstone and conglomerate unit lying unconformably on the Permian basement rock; a thick mudstone and siltstone unit referred to as the Main Mudstone member of the Hudspeth Formation; and 11 numbered conglomerate and sandstone members of the Gable Creek Formation intertonguing with a like number of mudstone and siltstone members of the Hudspeth Formation. Seven tongues of the Gable Creek Formation wedge out southward into the marine facies of the Hudspeth Formation; the four other tongues thin southward. Three Hudspeth Formation marine tongues wedge out northward into the Gable Creek Formation; the six other tongues thin northward. Shapes of tongues, textural and thickness variations, primary sedimentary structures, and current-flow directions indicate that during middle Cretaceous time there was a rising landmass on the north. Very large volumes of coarse sediment were delivered by a major river to a shallow-marine embayment, and extensive alluvial piedmont and delta plains projected into the sea. Swinging distributaries, episodic uplift of the source area, and intermittent subsidence of the basin caused the shoreline to fluctuate and produce a complex intertonguing of fluvial-deltaic sediments with marine sediments.

Ecology of San Francisco Bay: ABSTRACT

Comparison and contrast of the environmental conditions in San Francisco Bay and Suisun Bay show the ecology of both bays to be dominated by tidal currents. In Suisun Bay the (1) water velocity, (2) salinity variations, (3) turbidity, (4) median diameter of sedimentary particles, (5) aeration of the water, and (6) proportion of channels versus tidal flats are greater than in San Francisco Bay. Because of the greater variability of conditions in Suisun Bay, the foraminiferal fauna is less diversified, because there are only few genera able to tolerate great differences of most ecologic factors. Suisun Bay is characterized by a meager arenaceous fauna accompanied by a fairly diversified diatom flora. In contrast, the San Francisco Bay fauna is composed of a calcareous assemblage typical of shallow marine embayments. End_of_Article - Last_Page 1078------------