Influence des conditions hivernales sur les productions phyto-et zooplanctoniques en Méditerranée Nord-Occidentale. III. Caractérisation des eaux de surface au moyen de cultures d'algues

Bioassays were performed on surface-water samples, collected during the Médiprod I cruise of the R.V. “Jean Charcot” in the northern part of the Mediterranean Sea. Physiological responses of axenic algal cultures were measured in order to characterize the different water masses. The responses obtained are specific to each algal strain: Phaeodactylum tricornutum grows in all waters sampled during the first part of the cruise, while Chaetoceros lauderi does not develop because of its different nutritional requirements; Chlamydomonas magnusii does not grow in any of the tested samples. No clear relationship exists between the results obtained in vitro and those obtained in situ but, on the whole, the waters collected during the second part of the cruise allow a higher growth of the test algae in vitro. This higher fertility is probably related to the algal bloom which occurred between the first and the second part of the cruise. In the authors' opinion the great difference in uptake rates observed between the high-turbulence area (low production) and the adjacent area (high production), may be related more to biological conditioning than to any physical process. However, physical mixing seems to be responsible for inhibition of primary productivity at the two stations where mixing attains maximum values.     

Variations de quelques facteurs estimatifs de la biomasse,et en particulier de l'ATP,chez plusieurs algues marines planctoniques

ATP, carbon, and nitrogen content, and cell volume have been measured in 7 marine algae in culture. Intraspecific differences are negligible during the phase of exponential growth; interspecific differences in ATP and carbon content are slight during this phase compared with those observed in the same cultures between the exponential and senescent phases. As the interspecific differences agree well with those reported for algae in situ, this leads the authors to believe that the greater part of the biomass in situ is always in a state of physiological youth. ATP content is higher in diatoms, and seems linked with silica shell synthesis. In non-silicified species, there is a significant correlation between the ATP: plasma ratio and the division rate, although the cellular volumes are quite different. In the author's opinion, ATP content allows a good estimation of biomass to be made, as well as, under controlled conditions, a suitable estimation of primary productivity; however, because of their high silica content, diatoms should be considered separately from other phytoplankters.     

Écologie d'un milieu eutrophique: traitement mathématique des données

Numerous data on physical, chemical and biological parameters in the dilution layer of the Rhône mouth have been studied by multivariate techniques: principal-component analysis, part correlation. A new technique of cluster analysis is also proposed. By these means, a very euryhaline group of zooplankton species has been isolated and the extremely low sensibility of phytoplankton towards salinity has been shown. However, temperature seems to be the most important ecological factor. Instability and eutrophy of this area do not appear to disturb the phytoplankton cycle, which occurs with its usual succession. Chlorophyll a and organic matter do not seem of value for estimation of the biomass in the area studied.     

Concentration Requirement of glycine as nitrogen source for supporting effective growth of certain marine microplanktonic algae

Eighteen species of marine phytoplankton from 9 algal classes were tested under axenic-culture conditions for their capacity to improve phototrophic-growth performance on glycine with increasing concentration of this amino-acid serving as sole nitrogen source. Whereas all these species showed poor-to-no growth on 0.5 mM glycine, 14 species manifested considerable gain in growth-rate and yield at higher concentration levels. The highest level tested (25 mM) was generally not inhibitory and produced the best yields in these cases. Some species (notably Skeletonema costatum) showed marked reduction in the adaptation-lag period with increased glycine concentration, but Chlamydomonas palla required a very long adaptation period, which was little affected by concentration. Dunaliella tertiolecta, Emiliania huxleyi and Chroomonas salina showed sharp (albeit elevated) concentration thresholds for efficient glycine utilization. Rhodomonas lens and two cyanophycean strains, Agmenellum quadruplicatum and Anacystis marina, appeared incapable of successful growth on glycine at all concentrations tested, while the rhodophyte Porphyridium marinum displayed marginal growth. The results were insufficient to draw taxonomically general conclusions on algal-class potential for glycine utilization, but they showed unequivocally that more than 83% of phytoplankton species from 9 algal classes can utilize glycine for growth if the appropriate substrate concentration is provided.     

Catalytic and electrocatalytic hydrogenolysis of brominated diphenyl ethers

Polybrominated diphenyl ethers (PBDEs) are ubiquitous environmental contaminants due to their use as additive flame-retardants. Conventional catalytic hydrogenolysis in methanol solution and electrocatalytic hydrogenolysis in aqueous methanol were examined as methods for debrominating mono- and di-bromodiphenyl ethers, as well as a commercial penta-PBDE mixture, in each case using palladium on alumina as the catalyst. Electrocatalytic hydrogenolysis employed a divided flow-through batch cell, with reticulated vitreous carbon cathodes and IrO2/Ti dimensionally stable anodes. Both methods gave efficient sequential debromination, with essentially complete removal of bromine from the PBDEs, but the electrocatalytic method was limited by the poor solubility of PBDEs in aqueous methanol.     

High male reproductive success in a low-density Antarctic fur seal (Arctocephalus gazella) breeding colony

Understanding how population density influences mating systems may lead to important insights into the plasticity of breeding behavior, but few natural systems allow for such studies. Antarctic fur seals (Arctocephalus gazella) provide an interesting model system because they breed in colonies of varying densities. Previous studies have largely focused on a high-density site at Bird Island, South Georgia. Here, 13 highly polymorphic microsatellite loci were used to conduct a genetic analysis of a low-density breeding colony of this species at Livingston Island, approximately 1,600 km south of South Georgia. The majority of adults seen ashore (n?=?54) were sampled together with every pup born (n?=?97) over four consecutive years. Paternities were confidently assigned for 34 out of the 97 pups. Two out of 23 sampled males accounted for the paternity of 28 % of all pups sampled during the study and 82 % of the pups with an assigned father. Moreover, a full likelihood pedigree inference method assigned a further eight paternities to a single unsampled male seal that is inferred to have held a territory during the season before the study began. The most successful males in our study easily surpassed the previous record for the total number of pups sired per male seal for the species. Furthermore, we identified two triads of full siblings implying that their parents remated in three consecutive years. These findings suggest that territorial male fur seals may achieve greater success in monopolizing access to breeding females when population density is relatively low.     

Application of an improved method for the analysis of pesticides and their metabolites in the urine of farmer applicators and their families

As the annual use of pesticides in the United States has escalated, public health agencies have become increasingly concerned about chronic pesticide exposure. However, without reliable, accurate analytical methods for biological monitoring, low-level chronic exposures are often difficult to assess. A method for measuring simultaneously the urinary residues of as many as 20 pesticides has been significantly improved. The method uses a sample preparation which includes enzyme digestion, extraction, and chemical derivatization of the analytes. The derivatized analytes are measured by using gas chromatography coupled with isotope-dilution tandem mass spectrometry. The limits of detection of the modified method are in the high pg/L - low μg/L range, and the average coefficient of variation (CV) of the method was below 20% for most analytes, with approximately 100% accuracy in quantification. This method was used to measure the internal doses of pesticides among selected farmer applicators and their families. Definite exposure and elimination patterns (i.e., an increase in urinary analyte levels following application and then a gradual decrease to background levels) were observed among the farmer applicators and many of the family members whose crops were treated with carbaryl, dicamba, and 2,4-D esters and amines. Although the spouses of farm workers sometimes exhibited the same elimination pattern, the levels of the targeted pesticides or metabolites found in their urine were not outside the ranges found in the general U.S. population (reference range). The farmer applicators who applied the pesticides and some of their children appeared to have higher pesticide or metabolite levels in their urine than those found in the general U.S. population, but their levels were generally comparable to or lower than reported levels in other occupationally exposed individuals. These results, however, were obtained from a nonrandom sampling of farm residents specifically targeted to particular exposures who may have altered their practices because they were being observed; therefore, further study is required to determine if these results are representative of pesticide levels among residents on all farms where these pesticides are applied using the same application techniques. Using this method to measure exposure in a small nonrandom farm population allowed differentiation between overt and background exposure. In addition, the important role of reference-range information in distinguishing between various levels of environmental exposure was reaffirmed.     

Biological and ecophysiological reactions of white wall rocket (Diplotaxis erucoides L.) grown on sewage sludge compost

We studied the effects of sewage sludge compost on white wall rocket (Diplotaxis erucoides L.) compared with mineral fertilization and control (without any fertilizer) in a greenhouse experiment. The plants grown on the compost-amended soil showed a different growth dynamic: a significant delay in flowering and a bigger root system. Both the compost and the fertilization treatments increased biomass and seed yield. Heavy metal (Cu, Cd, Zn, Ni) distribution within the plant was in the following order: roots > leaves > stems, except for zinc which was homogeneously distributed. The balance of mineral nutrition was not affected by treatments. Zinc was the trace element which was most taken up. Unlike many species of Brassicaceae, white wall rocket is not a hyperaccumulator. Although sewage sludge compost improved plant growth, delay in flowering shows that it is necessary to take precautions when spreading sewage sludge in natural areas.