Bioavailability: the organism as sensor

The use of a system of continuous culture of phytoplankton at constant population density, the ‘cage-culture’ turbidostat, as a monitor of the bioavailability of pollutant materials, is illustrated. In the case of proposed dredge spoils from two polluted areas, it is shown that bulk analyses for scheduled materials cannot be equated with bioavailability. Monitoring for the effect of the whole pollutant mixture on a properly chosen test population could obviate the necessity for chemical analyses for each component.     

Joint Soviet-Turkish expedition in the Black Sea

The hydrological and hydrochemical structures of the upper 300 m water column of the Black Sea in autumn 1988 have been studied. Regularities in the distribution of the physico-chemical characteristics in the zone of interaction between aerobic and anaerobic waters as well as the topography of the H₂S zone boundary and its connection with a certain density gradient have been found.Translated by Mikhail M. Trufanov.     

Grain-size distribution of quartz and feldspar extracts and implications for flocculation processes

Quartz and feldspar extracts, obtained by chemical dissolution of the clay minerals, provide insight into the inorganic flocculation and mineralogical influences upon the texture of fine-grained glaciomarine deposits. Glacial comminution in higher latitudes explains the relatively high contents of quartz and feldspars. Quartz and feldspar are better sorted and were apparently less influenced by flocculation than were phyllosilicates, except for particles less than approximately 16 μm, which are poorly sorted due to their inclusion in flocs. The 16-μm boundary is suggested to be useful for approximately separating fines that are usually involved in flocculation and coarse silt and larger grains that are less influenced.     

Native aluminium (spherules and particles) in the Central Indian Basin sediments: Implications on the occurrence of hydrothermal events

We have sampled particles of native aluminium (Al°) in two sediment cores from the Central Indian Basin (CIB). The cores are geographically separated but are located at the base of two seamounts. The native Al° particles occurring as grains and spherules, have an average Al content of  95% and are associated with volcanogenic–hydrothermal material. Morphologically and compositionally, the specimens are similar to those reported from the East Pacific Rise. After ruling out several processes for the presence of the native Al°, we hypothesize that during progressive melting of magma, a basaltic magma is produced which has high contents of reductants such as methane and hydrogen, and a low oxygen fugacity. During the upward migration of such magma, reduction to metallic aluminium and the formation of native Al° particles takes place.     

The Pechora Sea: Past,recent, and future

The main stages in the development of the Pechora Sea are discussed. It is established that, during the high sea level stand corresponding to the warmest epoch of the Mikulino Interglacial, the Pechora Sea represented a more spacious, as compared with its present-day size, basin owing to the flooded valleys of river lower reaches. No sea in its present-day configuration existed during the last (Valdai) glaciation. At that time, the sea could have occupied only a narrow area along the southern coast of Novaya Zemlya, where marine sedimentation was in progress during the Late Pleistocene and Holocene. During the glaciation and postglacial time, the dried bottom of the former Pechora Sea accumulated large volumes of sand that are now concentrated largely in the accretion structures along its southern coast. In the current century, changes will occur mainly in the coastal zone of the Russkii Zavorot Peninsula, Pesyakov Island, the Varandei Settlement area, and the Medynskii Zavorot Peninsula, where a shoreline retreat for a distance of 0.5 km is expected.     

Physiological and behavioral responses of Bathynerita naticoidea (Gastropoda: Neritidae) and Methanoaricia dendrobranchiata (Polychaeta: Orbiniidae) to hypersaline conditions at a brine pool cold seep

Bathynerita naticoidea (Gastropoda: Neritidae) and Methanoaricia dendrobranchiata (Polychaeta: Orbiniidae) are two of the most abundant invertebrates associated with cold‐seep mussel beds in the Gulf of Mexico. At the methane seep known as Brine Pool NR‐1 (27 °43.415 N, 91 °16.756 W; 650 m depth), which is surrounded by a broad band of mussels (Bathymodiolus childressi), these species have distinctly different patterns of abundance, with the gastropod being found mostly at the outer edge of the mussel bed (average density in November 2003: 817 individuals·m⁻² in outer zone, 20·m⁻² in inner zone) and the polychaete being found almost exclusively near the inner edge (average density in November 2003: 3155 individuals·m⁻² in inner zone, 0·m⁻² in outer zone), adjacent to the brine pool itself. The salinity of the brine pool exceeds 120, so we hypothesized that M. dendrobranchiata should be more tolerant of high salinities than B. naticoidea. The opposite proved to be true. The gastropods were capable of withstanding salinities at least as high as 85, whereas the polychaetes died at salinities higher than 75. Both species were osmoconformers over the range of salinities (35–75) tested. Behavioral responses of B. naticoidea to salinities of 50, 60, and 70 were investigated in inverted vertical haloclines. Gastropods generally did not enter water of salinity greater than 60, but tolerated short periods at 60. Behavioral avoidance of brine should limit the vertical distribution of B. naticoidea in the inner zone to the top 2.5–5 cm of the mussel bed. Behavior is also a likely (though unproven) mechanism for controlling horizontal distribution of this species across the mussel bed. Methanoaricia dendrobranchiata can tolerate short excursions into the brine, but probably avoids hypersaline conditions by aggregating on the tops of the mussels.     

An Engineering Application Tool for Visual Assessment of the Equilibrium Beach

An engineering application tool for prediction of the static equilibrium bay(Beach Mod)is established to describe two bay shape formulas by use of the programming software "MATLAB" with a graphic user interface(GUI).The tool is user-friendly for engineering students for the design of beach shapes.This tool was tested through application on three types of beaches in Taiwan and Australia.By implementing the concept of Headland Control,the Beach Mod program allows users to draw a structure and create an artificial headland.The results indicate that Beach Mod can efficiently forecast beach changes as well as MEPBAY,a competing software package,while boasting a better user interface.     

Thorium isotopes as tracers of particles dynamics and deep water circulation in the Indian sector of the Southern Ocean (ANTARES IV)

Dissolved and particulate samples were collected to study the distribution of thorium isotopes (²³⁴Th, ²³²Th and ²³⁰Th) in the water column of the Indian sector of the Southern Ocean (from 42°S to 47°S and from 60°E to 66°E, north of the Polar Front) during Austral summer 1999. Vertical profiles of excess ²³⁰Th (²³⁰Th_xs) increases linearly with depth in surface water (0–100 m) and a model was applied to estimate a residence time relative to the thorium scavenging (τ_scav). Low τ_scav in the Polar Front Zone (PFZ) are found, compared to those estimated in the Subtropical Front Zone (STZ). Changes in particle composition between the PFZ and STZ could influence the ²³⁰Th_xs scavenging efficiency and explain this difference. An innovative coupling between ²³⁴Th and ²³⁰Th_xs was then used to simultaneously constrain the settling velocities of small (0.6–60 μm) and large (above 60 μm) particles. Although the different hydrological and biogeochemical regimes visited during the ANTARES IV cruise did not explain the spatial variation of sinking velocity estimates, our results indicate that less particles may reach the seafloor north (60 ± 2 m d^− 1, station 8) than south of the Agulhas Return Current (119 ± 23 and 130 ± 5 m d^− 1 at stations 3 and 7, respectively). This information is essential for understanding particle transport and by extension, carbon export. In the deep water column, the ²³⁰Th_xs concentrations did not increase linearly with depth, probably due to lateral transport of North Atlantic Deep Water (NADW) from the Atlantic to the Indian sector, which renews the deep waters and decreases the ²³⁰Th_xs concentrations. A specific ²³⁰Th_xs transport model is applied in the deep water column and allows us to assess a “travel time” of NADW ranging from 2 to 15 years.     

Abundance of the introduced seastar, Asterias amurensis, and spatial variability in soft sediment assemblages in SE Tasmania: Clear correlations but complex interpretation

The northern Pacific seastar, Asterias amurensis, was first collected in southeast Tasmania in 1986. Mistaken for the endemic asteroid Uniophora granifera, its true identity was not realised until 1992. It is now a conspicuous predator in soft sediment habitats in this region, and is considered a major threat to native assemblages and commercial species. We examined the structure of soft sediment assemblages at different spatial scales in southeast Tasmania, and correlated spatial variation in community composition with seastar abundances. We found that the structure of soft sediment assemblages is highly variable at a range of spatial scales from metres to tens of kilometres. Clear differences in the composition of assemblages and abundances of major taxa were detected between areas with and without seastars and between areas with low and high seastar densities. However, the nature of these patterns suggests that they are more likely due to differences in sediment characteristics than due to impacts of the seastar. Thus, spatial differences in soft sediment assemblages might have been erroneously attributed to seastars without detailed information on important physical factors such as sediment characteristics. A second survey, using larger sampling units (1 m²) but across a more limited spatial extent, targeted bivalves and heart urchins that were identified as important prey of the seastar in observations of feeding and in experimental studies. Large-scale patterns of abundance and size structure were consistent with seastar effects anticipated from small-scale experimental and feeding studies for some, but not all, species. While the field survey ultimately provided evidence about the presence or absence of seastar impacts at large-scales, the identification of key ecological variables in experimental and feeding studies proved crucial to both the design and interpretation of patterns observed in the large-scale surveys. Overall, this work highlighted the necessity to consider multiple lines of evidence rather than relying on a single ‘inferential’ test, in the absence of pre-impact data.