Utilization of a submersible UV fluorometer for monitoring anthropogenic inputs in the Mediterranean coastal waters

We evaluated the performances of a submersible ultraviolet fluorometer (EnviroFlu-HC, TriOS Optical Sensors) dedicated to the real time measurement of polycyclic aromatic hydrocarbons (PAHs) in the aquatic media. We conducted calibration experiments and in situ measurements in the coastal Mediterranean Sea. We found that the EnviroFlu-HC was not strictly specific to PAHs, even though it exhibited the highest sensitivity for phenanthrene, but could response to tryptophan-like material as well, and in a much less extent, to humic substances. The sensor signal showed great spatial and temporal variations in clean and polluted sites, with likely a high contribution of PAHs in the harbors, and a high contribution of tryptophan-like and humic-like materials in the sewage effluent. We conclude that the EnviroFlu-HC is a good tool for monitoring anthropogenic inputs in the coastal waters, although its utilization should be combined to other fluorescence measurements to improve the information about the nature of the aromatic compounds detected.     

Fluorophores in the Arabian Sea and their relationship to hydrographic conditions

 Water mass distributions, upwelling and filament formation are of complex significance for biological and chemical processes. Temperature and salinity are routinely used to characterize these hydrographic conditions. In situ profiles and sample analyses from the cruise So119 of RV Sonne in May 1997 into the Arabian Sea indicate that optical parameters such as the fluorescence of phytoplankton pigments, gelbstoff and proteins reflect hydrographic processes as well, and are useful to describe and explain biochemical processes. The dependence of bio-optical parameters to DOC and chlorophyll a concentrations is examined. While the relation between extracted chlorophyll and chlorophyll fluorescence is quite reasonable, DOC and gelbstoff fluorescence do not show a functional dependency. This is mainly due to sunlight-induced degradation of fluorophores in the surface layer. Enhanced gelbstoff signals in intermediate and deep waters are related to Persian Gulf Water. The optical data reveal a relation between the depth of the chlorophyll maximum, the depth of 1% surface light and the geographical latitude. In the context of remote sensing of phytoplankton biomass from ocean colour images, the depth of the chlorophyll maximum is a crucial parameter. Thus, the revealed dependency on latitude is useful for the evaluation of primary production with satellite remote sensing. Received: 22 May 2002 / Accepted: 18 February 2003 Responsible Editor: Andreas Oschlies Acknowledgements. This work was supported by a grant from the Federal Minister of Education and Technology, Bonn, within the framework of the JGOFS Arabian Sea program. We are grateful to the captain and the crew of RV Sonne for their support. Special thanks are given to the chief scientist of the cruise, Pr. V. Ittekkot, for helpful discussions. We are indebted to Mr. Rüdiger Heuermann and Mr. Nils Bürckel for their participation in the cruise and their support in the data analysis.     

Vitamin E co-treatment reduces Aroclor 1254-induced impairment of reproductive neuroendocrine function in Atlantic croaker

We have shown previously that exposure of Atlantic croaker to a PCB mixture (Aroclor 1254) results in impaired reproductive neuroendocrine function. In addition, we have identified hypothalamic tryptophan hydroxylase (TPH), the rate-limiting enzyme in serotonin (5-hydroxytryptamine) synthesis, as a target of PCB neuroendocrine toxicity. In order to further elucidate the mechanisms of PCB neurotoxicity, the present study investigated whether PCB-induced decrease in hypothalamic TPH activity resulted from degradation of the enzyme protein. Fish were exposed to Aroclor 1254 in the diet (0.1 mg/100 g body weight (BW)/day) for 30 days. The PCB exposure elicited a significant decrease in hypothalamic TPH protein content, which could be at least partially responsible for the reduced TPH activity. To test whether a similar PCB exposure could cause oxidative damage in croaker hypothalamic tissues, we examined the formation of malondialdehyde (MDA) protein adducts as a marker of lipid peroxidation (LPO). The same dose of PCB increased the MDA-protein adduct formation in the hypothalamus. In a separate experiment, the role of vitamin E, an antioxidant, to prevent or decrease the effect of PCB on hypothalamic TPH activity and gonadal growth was examined. The vitamin E co-treatments (1 and 10 mg/100 g BW/day) with PCB significantly reduced the effects of PCB on TPH activity and gonadal growth. These results suggest possible involvement of oxidative processes in PCB neurotoxicity.