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Biomedical subjects

S W Fowler

Publications and source records attributed to S W Fowler.

12 recordsLinked to original sources
PubMed1991

Reproductive cycle and heavy metals in the organs of red mullet, Mullus barbatus (L.), from the northwestern Mediterranean.

Concentrations of the heavy metals Cd, Cu, Fe Mn, V and Zn have been measured in the principal tissues of the red mullet, Mullus barbatus (L.), during a complete sexual cycle. By comparison of metal levels during the reproductive and non-reproductive periods, it was found that concentrations as well as total amounts of Cu, Mn and Zn in liver and gonads of male and female mullets were dependent upon the stage of the sexual cycle. No relationship with the sexual cycle was noted for these metals measured in muscle, kidney, spleen or pyloric caecum. Because of the observed variation in liver and gonad metal concentrations, these tissues appear to be poor indicators of ambient levels of metals in the surrounding waters. However, muscle may prove useful as an indicator tissue owing to its apparent independence of effects of the sexual cycle.

Animals↗
PubMed1986

Vertical flux of hexachlorobenzene in coastal waters of the north-west Mediterranean Sea.

In a study on the biogeochemistry of chlorinated hydrocarbons in the Mediterranean Sea, hexachlorobenzene (HCB) has been analysed in particulate matter collected in sediment traps moored 2 km off the coast of Monaco. HCB concentrations in this material, which was composed largely of biogenic debris, ranged from non-detectable to 7.3 ng/g dry weight. Time-series measurements (n = 18) made between March-September 1981 demonstrated that the vertical flux of HCB through 100 m averaged 59 (range, non-detectable to 153) pg/cm2 per year. There was no clear relationship between the HCB flux and the time of year. Nor were there any correlations between either HCB concentrations in fast-settling particles or the HCB flux and that of organic carbon. The similarity in concentration of HCB in sediment-trap particulates and freshly excreted zooplankton faecal pellets suggests that faecal pellet deposition acts to remove this contaminant from surface waters. Comparison of the observed average HCB flux through 100 m with estimates of the flux to sediments at 250 m depth (7.3 pg/cm2 per year, based on HCB concentrations in surface sediments and independently derived average sediment-deposition rates) indicates that as much as 87% of the particulate-associated HCB is dissolved or degraded before burial into sediments. These results demonstrate that HCB is removed from the euphotic zone by sedimentation processes less rapidly than polychlorinated biphenyls but on the same time-scale as the pesticide lindane. An upper limit on the residence time in surface waters was calculated to be 135 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Chlorobenzenes↗
PubMed1985

Mercury in the open Mediterranean: evidence of contamination?

In relation to the previously observed higher Hg concentrations in the tissues of certain Mediterranean fish (e.g. mackerel and tuna) compared with the same species in the Atlantic, the evidence for anomolously high Hg contamination of the Mediterranean has been examined. Four aspects have been addressed: the reliability of analytical measurements; the paucity of data on Hg in the Mediterranean and other oceanic areas; the actual levels of Hg in truly open-ocean waters; and ecological factors which may play a role in the enrichment of Hg in Mediterranean fish. Recent evidence suggests that former measurements of Hg in sea water are inadequate, and overestimate the concentrations of Hg in oceanic waters. Even today, intercalibration studies suggest that there are serious problems in the determination of Hg at the levels present in open oceans. A comparison of the most recent reliable data indicates that Mediterranean open-ocean waters are not enriched in Hg relative to the North Atlantic or other open-ocean areas. Similarly, no evidence exists for Hg anomalies in deep-ocean sediments in the Mediterranean, although it is apparent that localised coastal anomalies do occur as a result of natural and anthropogenic Hg sources. Generally, there is a severe lack of data on total Hg concentrations in truly open-ocean environments, and virtually no data on alkyl forms of Hg. Geographic comparisons of Hg in plankton and small pelagic fish do not indicate the presence of higher Hg concentrations in the Mediterranean Sea compared with oceanic regimes. Since these lower trophic species serve as a source of food for larger predaceous fish, e.g. tuna, the origin of the high Hg content in top-level predators is difficult to explain by evoking solely food chain relationships. In trying to resolve the question of why high Hg concentrations are found in certain Mediterranean fish, future studies should include an examination of the alkyl as well as inorganic forms of Hg, and ecological factors such as growth rates and feeding regime.

Animals↗
PubMedDate not supplied

Rapid removal of Chernobyl fallout from Mediterranean surface waters by biological activity.

The sinking of particulate organic matter from the euphotic zone is an important pathway for the vertical transport of many elements and organic compounds in the sea. Many natural and artificial radionuclides in surface waters are readily adsorbed onto suspended particles and are presumably scavenged and removed to depth on time scales commensurate with both particle sinking rate and retention time of the radionuclide on the particle. Previously, abyssal benthic organisms from the northeast Pacific were found to contain short-lived fission products which entered the sea surface as fallout from nuclear testing. The presence of these radionuclides at great depth could not be explained by Stokesian settling of small fallout particles and it was hypothesized that zooplankton grazing in the surface layers packaged these particle-reactive radionuclides into large, relatively dense faecal pellets which rapidly sank to depth. We report here data from a time-series sediment trap experiment and concomitant zooplankton collections which show conclusively that Chernobyl radioactivity, in particular the rare earth nuclides 141Ce and 144Ce, entering the Mediterranean as a single pulse, was rapidly removed from surface waters and transported to 200 m in a few days primarily by zooplankton grazing.

Accidents↗