Shelf Transport Pathways Adjacent to the East Australian Current Reveal Sources of Productivity for Coastal Reefs

The region where the East Australian Current (EAC) separates from the coast is dynamic and the shelf circulation is impacted by the interplay of the western boundary current and its eddy field with the coastal ocean. This interaction can drive upwelling, retention or export. Hence understanding the connection between offshore waters and the inner shelf is needed as it influences the productivity potential of valuable coastal rocky reefs. Near urban centres, artificial reefs enhance fishing opportunities in coastal waters, however these reefs are located without consideration of the productivity potential of adjacent waters. Here we identify three dominant modes of mesoscale circulation in the EAC separation region (~31.5−34.5°S); the ‘EAC mode’ which dominates the flow in the poleward direction, and two eddy modes, the ‘EAC eddy mode’ and the ‘Eddy dipole mode’, which are determined by the configuration of a cyclonic and anticyclonic eddy and the relationship with the separated EAC jet. We use a Lagrangian approach to reveal the transport pathways across the shelf to understand the impact of the mesoscale circulation modes and to explore the productivity potential of the coastal waters. We investigate the origin (position and depth) of the water that arrives at the inner-mid shelf over a 21-day period (the plankton productivity timescale). We show that the proportion of water that is upwelled from below the euphotic zone varies spatially, and with each mesoscale circulation mode. Additionally, shelf transport timescales and pathways are also impacted by the mesoscale circulation. The highest proportion of upwelling (70%) occurs upstream of 32.5°S, associated with the EAC jet separation, with vertical displacements of 70–120 m. From 33 to 33.5°S, water comes from offshore above the euphotic layer, and shelf transport timescales are longest. The region of highest retention over the inner shelf is immediately downstream of the EAC separation region. The position of the EAC jet and the location of the cyclonic eddy determines the variability in shelf-ocean interactions and the productivity of shelf waters. These results are useful for understanding productivity of temperate rocky reefs in general and specifically for fisheries enhancements along an increasingly urbanised coast.

Morphological analysis of micropyrite populations from the Toarcian of Bulgaria

Morphological analysis of micropyrite populations of argillaceous inner shelf deposits from the Toarcian of Bulgaria was carried out in order to evaluate their stratigraphic distribution and their potential as recorders for redox conditions. Four types of micropyrites were documented: 1) euxinic framboids; 2) oxic/dysoxic framboids; 3) polyframboids; and 4) non-framboidal diagenetic pyrites. Resedimented sulphides were also observed. Micropyrite morphologies denoted upper- to lower dysoxic depositional settings within the sampled successions. Anoxic conditions seem also possible to exist but at very narrow intervals.

Calcareous Nannofossil Biostratigraphy and Ostracoda Paleoecology of Hartha Formation from Balad (1) well, Central Iraq

Seventeen samples of Hartha Formation in Balad (1) well, central Iraq, are studied on the basis of stratigraphic ranges of the recorded calcareous nannofossils for twenty species belonging to twelve genera. The studied section reveals three biozones arranged from oldest to youngest as follows; (1) Calculites ovalis Interval Biozone (CC19), (2) Ceratolithoides aculeus Interval Biozone (CC20), (3) Quadrum sissinghii Interval Biozone (CC21). These Biozones are correlated with other calcareous nannofossils biozones from both local and regional sections, leading to conclude the age of the Middle Campanian. Rerecorded eighteen ostracode species that belong to eleven genera are identified, all of which were previously recorded from Iraq and adjacent regions. The occurrence of these species leads to conclude a continental shelf environment, while they are typical of inner shelf-outer shelf depth.

Hydrodynamic and Sediment Transport Patterns in the Minho and Douro Estuaries (NW Portugal) Based on ADCP Monitoring Data: Part 1-Tidal Sediment Exchanges

The tidal variability of the Minho and Douro lower estuaries (NW Portugal) water column structure was assessed at the semi-diurnal and fortnightly time scales under two contrasting seasonal river flow scenarios during the summer of 2005 and winter of 2006. Sediment fluxes inferred from calibrated ADCP acoustic backscatter revealed that, during spring tides and low runoff conditions, both estuaries act as sinks instead of sources of sediments into the inner shelf. Sediment export occurred during neaps, in both estuaries, when the river flow values were high enough to counteract the effect of the entering flood. No evidence of coarse sediment export into the inner shelf that would eventually nourish the littoral system could be inferred from these datasets.

Distribution of Marine Palynomorphs in Surface Sediments, Prydz Bay, Antarctica

<p><b>Prydz Bay Antarctica is an embayment situated at the ocean-ward end of the LambertGlacier/Amery Ice Shelf complex East Antarctica. This study aims to document thepalynological assemblages of 58 surface sediment samples from Prydz Bay, and tocompare these assemblages with ancient palynomorph assemblages recovered fromstrata sampled by drilling projects in and around the bay.</b></p> <p>Since the early Oligocene, terrestrial and marine sediments from the Lambert Grabenand the inner shelf areas in Prydz Bay have been the target of significant glacialerosion. Repeated ice shelf advances towards the edge of the continental shelfredistributed these sediments, reworking them into the outer shelf and Prydz ChannelFan. These areas consist mostly of reworked sediments, and grain size analysisshows that finer sediments are found in the deeper parts of the inner shelf and thedeepest areas on the Prydz Channel Fan. Circulation within Prydz Bay is dominatedby a clockwise rotating gyre which, together with coastal currents and ice bergploughing modifies the sediments of the bay, resulting in the winnowing out of thefiner component of the sediment.</p> <p>Glacial erosion and reworking of sediments has created four differing environments(Prydz Channel Fan, North Shelf, Mid Shelf and Coastal areas) in Prydz Bay whichis reflected in the palynomorph distribution. Assemblages consist of Holocenepalynomorphs recovered mostly from the Mid Shelf and Coastal areas and reworkedpalynomorphs recovered mostly from the North Shelf and Prydz Channel Fan. Thepercentage of gravel to marine palynomorph and pollen counts show a relationshipwhich may reflect a similar source from glacially derived debris but the percentageof mud to marine palynomorph and pollen counts has no relationship.</p> <p>Reworked palynomorphs consist of Permian to Eocene spores and pollen and Eocenedinocysts which are part of the Transantarctic Flora. Holocene components are avaried assemblage of acritarchs, dinoflagellate cysts (dinocysts), prasinophyte algae,red algae and large numbers of Zooplankton sp. and foraminifera linings. In situdinocysts are dominated by the heterotroph form Selenopemphix antarctica and none of the Holocene dinocyst species found in Prydz Bay have been recorded in theArctic. In contrast acritarchs, prasinophytes and red algae are all found in the Arcticand reflect a low salinity and glacial meltwater environment. Comparison withmodern surface samples from the Arctic and Southern Ocean show there is a strongcorrelation to reduction in the autotroph:heterotroph dinocyst ratio with increasinglatitude.</p> <p>Todays assemblage of marine palynomorphs are more complex than those recordedin ancient assemblages and there is a lower level of reworked material. Acritarchs(Leiosphaeridia spp. Sigmopollis sp.) and prasinophytes (Cymatiosphaera spp.</p> <p>Pterospermella spp. Tasmanites spp.) are recorded in the ancient record in Antarcticaas well as surface sediments in Prydz Bay, but there are very low numbers ofLeiosphaeridia spp. and Sigmopollis spp. present today in comparison to the ancientrecord. Dinocysts in situ and recovered in Prydz Bay are endemic to the Antarcticbut have not been recorded in the ancient record.</p>

Distribution of Marine Palynomorphs in Surface Sediments, Prydz Bay, Antarctica

<p><b>Prydz Bay Antarctica is an embayment situated at the ocean-ward end of the LambertGlacier/Amery Ice Shelf complex East Antarctica. This study aims to document thepalynological assemblages of 58 surface sediment samples from Prydz Bay, and tocompare these assemblages with ancient palynomorph assemblages recovered fromstrata sampled by drilling projects in and around the bay.</b></p> <p>Since the early Oligocene, terrestrial and marine sediments from the Lambert Grabenand the inner shelf areas in Prydz Bay have been the target of significant glacialerosion. Repeated ice shelf advances towards the edge of the continental shelfredistributed these sediments, reworking them into the outer shelf and Prydz ChannelFan. These areas consist mostly of reworked sediments, and grain size analysisshows that finer sediments are found in the deeper parts of the inner shelf and thedeepest areas on the Prydz Channel Fan. Circulation within Prydz Bay is dominatedby a clockwise rotating gyre which, together with coastal currents and ice bergploughing modifies the sediments of the bay, resulting in the winnowing out of thefiner component of the sediment.</p> <p>Glacial erosion and reworking of sediments has created four differing environments(Prydz Channel Fan, North Shelf, Mid Shelf and Coastal areas) in Prydz Bay whichis reflected in the palynomorph distribution. Assemblages consist of Holocenepalynomorphs recovered mostly from the Mid Shelf and Coastal areas and reworkedpalynomorphs recovered mostly from the North Shelf and Prydz Channel Fan. Thepercentage of gravel to marine palynomorph and pollen counts show a relationshipwhich may reflect a similar source from glacially derived debris but the percentageof mud to marine palynomorph and pollen counts has no relationship.</p> <p>Reworked palynomorphs consist of Permian to Eocene spores and pollen and Eocenedinocysts which are part of the Transantarctic Flora. Holocene components are avaried assemblage of acritarchs, dinoflagellate cysts (dinocysts), prasinophyte algae,red algae and large numbers of Zooplankton sp. and foraminifera linings. In situdinocysts are dominated by the heterotroph form Selenopemphix antarctica and none of the Holocene dinocyst species found in Prydz Bay have been recorded in theArctic. In contrast acritarchs, prasinophytes and red algae are all found in the Arcticand reflect a low salinity and glacial meltwater environment. Comparison withmodern surface samples from the Arctic and Southern Ocean show there is a strongcorrelation to reduction in the autotroph:heterotroph dinocyst ratio with increasinglatitude.</p> <p>Todays assemblage of marine palynomorphs are more complex than those recordedin ancient assemblages and there is a lower level of reworked material. Acritarchs(Leiosphaeridia spp. Sigmopollis sp.) and prasinophytes (Cymatiosphaera spp.</p> <p>Pterospermella spp. Tasmanites spp.) are recorded in the ancient record in Antarcticaas well as surface sediments in Prydz Bay, but there are very low numbers ofLeiosphaeridia spp. and Sigmopollis spp. present today in comparison to the ancientrecord. Dinocysts in situ and recovered in Prydz Bay are endemic to the Antarcticbut have not been recorded in the ancient record.</p>