Influence of capture stress, salinity and reproductive status on zinc associated with metallothionein-like proteins in the livers of three marine teleost species

The influence of capture stress, salinity and reproductive status on zinc associated with the metallothionein-like (MT-like) proteins in the livers of three marine teleost species was investigated. In striped mullet, Mugil cephalus L., the zinc associated with the MT-like protein, as determined by gel-permeation HPLC, increased significantly from approximately 102 to 1162 nmol zinc bound/g wet wt 7 days following capture in the field, handling, transportation to the laboratory and transfer to holding tanks. Significant increases were also observed following exposure to reduced salinity for 7 days. Smaller increases were observed in cultured red drum, Sciaenops ocellatus, livers following exposure to reduced salinity and physical trauma for 7 days. Finally, there was approximately a 2·5-fold increase in the zinc associated with the MT-like protein in livers of female spotted seatrout, Cynoscion nebulosus, collected during the reproductive season compared to regressed animals. These findings emphasize the need for establishing the natural fluctuations in MT levels as well as the response to common physical environmental variables before measurement of MT can be used reliably as a biochemical indicator of environmental contamination.     

Hydrothermal Vent Geology and Biology at Earth’s Fastest Spreading Rates

Earth’s fastest present seafloor spreading occurs along the East Pacific Rise near 31°–32° S. Two of the major hydrothermal plume areas discovered during a 1998 multidisciplinary geophysical/hydrothermal investigation of these mid-ocean ridge axes were explored during a 1999 Alvin expedition. Both occur in recently eruptive areas where shallow collapse structures mark the neovolcanic axis. The 31° S vent area occurs in a broad linear zone of collapses and fractures coalescing into an axial summit trough. The 32° S vent area has been volcanically repaved by a more recent eruption, with non-linear collapses that have not yet coalesced. Both sites occur in highly inflated areas, near local inflation peaks, which is the best segment-scale predictor of hydrothermal activity at these superfast spreading rates (150 mm/yr).     

Estimating Deep Seafloor Interface and Volume Roughness Parameters Using the Multibeam-Hydrosweep System

Utilizing a hull-mounted, multinarrow beam echosounder onboard RV Polarstern, we measured variation of acoustic backscatter with incidence angles at two different sites in the Southern Oceans (Agulhas Plateau and the Riiser Larsen Sea). We modeled the data, using a composite roughness model, including water-sediment interface roughness and sediment volume roughness parameters. The model effectively uses the near normal incidence angle backscatter to determine the seafloor interface roughness parameters employing Helmholtz-Kirchhoff theory. Beyond 20° incidence angles, an application of Rayleigh-Rice theory is made by using a necessary splicing technique (combining both of the theories at 20° incidence angle). The estimated interface and volume roughness parameters are found to be in accordance with the known area geology.     

Lysosomal injury and MFO activity in the liver of flounder (Platichthys flesus L.) in relation to histopathology of hepatic degeneration and carcinogenesis

Flounder (Platichthys flesus L.), 18–48 cm total length were sampled in the mouth of the Elbe River during a 3-year interdisciplinary project ‘Fish Diseases in the Wadden Sea’. Lysosomal changes (lysosomal membrane stability) and the activity of biotransforming enzymes (MFOs/EROD) were measured parallel to investigations of ultrastructural changes in liver cells, tissue pathologies and macroscopically visible changes. The aim of the study was to investigate if these cyto- and biochemical parameters were able to reflect contaminant induced biological effects. Interlinking of the results of the MFO activity to the pathological alterations observed at the electron- and light-microscopic levels as well as during macroscopic inspection of identical individuals evidenced that the activity of the biotransformation enzymes (EROD) was not induced in healthy livers, increased considerably with the onset of liver changes and dropped again in those livers with degenerative, preneoplastic and neoplastic lesions. In contrast, concurrent studies of lysosomal membrane stability measured in parallel showed a decrease with the onset and progression of liver lesions from reversible to irreversible, neoplastic change.     

Phytoplankton biomass and size fractions in surface waters of the Australian sector of the southern ocean

We collected surface water along the 142nd E meridian from Tasmania to Antarctica in December 1999. We measured temperature, salinity and total chlorophyll a; additionally, we collected suspended particle size fractions and used fluorometric analysis to determine the quantity of chlorophyll a in each of four cell size classes: picoplankton (<3 μm), two nanoplankton fractions (3–10 μm and 10–20 μm) and microplankton (> 20 μm). Changes in temperature and salinity show that we crossed 6 water masses separated by 5 fronts. We found low abundance (<0.2 mg m⁻³) of chlorophyll in all size classes, with the exception of higher values near the continent (0.2 to 0.4 mg m⁻³). Lowest chlorophyll values (<0.1 mg m⁻³) were found in the Polar Frontal Zone (51° to 54°S). Microplankton made up the largest portion of total chlorophyll throughout most of the region. We conclude that biomass of all phytoplankton fractions, especially pico-and nanoplankton, was constrained by limiting factors, most probably iron, throughout the region and that ecosystem dynamics within a zone are not circumpolar but are regionalized within sectors.     

Current-influenced depositional provinces, continental margin off Cape Hatteras, identified by petrologic method

Analyses of DSRV “Alvin” core samples on the Cape Hatteras margin indicate major textural and compositional changes at depths of about 1000 and well below 2500 m. The distribution patterns of petrologic parameters correlate well with water mass flow and suspended-sediment plumes measured on this margin by other workers. Our study also shows: (a) vigorous erosion and sediment transport at depths of less than 400 m resulting from the NE-trending Gulf Stream flow; (b) deposition, largely planktonic-rich sediment released from the Gulf Stream, on the upper- to mid-slope, to depths of about 800–1200 m; (c) winnowing, resuspension and deposition induced by periodically intensified slope currents on the mid-slope to uppermost rise, between about 1000 and 2500 m; and (d) prevailing deposition on the upper rise proper (below 2500 m), from transport by the SW-trending Western Boundary Undercurrent. Sediments moved by bottom currents have altered the composition and distribution patterns of material transported downslope by offshelf spillover; this mixing of gravity-emplaced and bottom-current-transported sediment obscures depositional boundaries. Moreover, reworking of the seafloor by benthic organisms alters physical properties and changes erodability of surficial sediments by bottom currents. Measurement of current flow above the seafloor and direct observation of the bottom are insufficient to delineate surficial sediment boundaries. Detailed petrologic analyses are needed to recognize the long-term signature of processes and define depositional provinces.