Deep chlorophyll maximum distribution in the central Tyrrhenian Sea described by a towed undulating vehicle

The towed undulating vehicle (TUV), named SARAGO, was used for two fine-scale surveys between the Italian and the Sardinian coasts during the Astraea 2 cruise (6-7 and 26-27 September 1995), studying the deep chlorophyll maximum distribution. SARAGO sections identify a sub-surface doming with higher chlorophyll a and primary production concentrations in the upwelling area of a cyclonic gyre region, detected by sea-surface temperature images. In the first section, the cyclone presents a double doming, in density and salinity, with shallower and concentrated patches of chlorophyll a for about 2 miles. Twenty days later, the second section shows that the gyre changes shape and extension, showing a single doming with higher primary production and chlorophyll a concentrations, distributed over a large area of about 40 nautical miles. SARAGO allows analysis of this high-variability phenomenon (cyclonic gyre) and allows concentrated patches (2 nm) to be identified, thus proving the importance of TUVs in the study of mesoscale processes.     

Loss of genetic diversity in Harpacticoida near offshore platforms

Offshore oil and gas production platforms can be a source of chronic stress that could lead to sublethal impacts on resident benthic organisms. In June 1993 and January 1994, genetic diversity of Harpacticoida (Copepoda) living proximal to operating, offshore platforms in the Gulf of Mexico was estimated to test if platforms are associated with strong selective pressures. Because harpacticoids have short generation times and direct benthic development, they are suitable organisms for examining population responses. Genetic diversity was estimated by comparing restriction fragment length polymorphisms generated from mitochondrial DNA amplified by the polymerase chain reaction on individuals of five species (Cletodes sp., Enhydrosoma pericoense, Normanella sp., Robertsonia sp., and Tachidiella sp.). Populations living at Near regions (stations<50 m from a platform) had significantly less haplotype diversity than populations of the same species living at Far regions (stations>3 km from a platform). The levels of haplotype diversity exhibited by the Far populations were similar at three different platforms located hundreds of kilometers apart. The differences in haplotype diversity between Near and Far regions were the result of a higher proportion of dominant haplotypes, and a loss of less common haplotypes. Haplotypic diversity was inversely correlated with a multivariate measurement of levels of sediment contaminants. The pattern of haplotype diversity on the Gulf of Mexico continental shelf seems to consist of a uniform level of haplotype diversity, punctuated by islands of lower diversity around oil and gas platforms. The selective pressures that lead to a loss of genetic diversity may be the result of contaminants, other differences in the physico-chemical environment, or disturbance in general.     

Coping with riverbank erosion hazard and displacement in bangladesh: survival strategies and adjustments

As a deltaic plain, Bangladesh annually experiences riverbank erosion hazard due to sudden and rapid channel shifting, particularly in the major floodplain areas of the country. Consequently, valuable cultivable land is lost; also village settlements, markets and towns are destroyed, displacing tens of thousands of people. This paper examines the magnitude of river channel migration and encroachment on land, and the nature of human adjustment systems in the Brahmaputra–Jamuna floodplain, by investigating aspects of the social and cultural dynamics of resettlement of the displaced people. Some policy measures are recommended to improve the ability of the people in the floodplain to cope with these hazards.     

The role of socio-economic data in food needs assessment and monitoring

This paper reviews six case studies examined as part of a project to review targetting methodologies employed by non-government organisations in Africa during the 1984-6 food crisis. Most agencies have not yet fully evaluated the role of data in informing policy decisions during their respective emergency programmes. The case studies presented reflect a wide variety of approaches to targetting emergency food aid that are based largely on the use of 'socio-economic' data. The recent emergency relief operations in Africa seem to indicate a change in relief agencies' approaches to the assessment and monitoring of needs of the affected populations. Earlier dependance on nutritional data has given way to an increasing reliance on the use of socio-economic indicators. There was a wide variation in the case studies of the type of indicators collected and utilised in needs assessment and monitoring. There were those who relied almost exclusively on nutritional data to target resources during the 1984-86 African crisis, and others whose experiences during that period lead them to attach more weight to socio-economic data. Other agencies appear to have recognised the problems of relying solely on nutritional data to target food aid during their 1984–86 emergency programmes, and thus more or less abandoned classical anthropometric surveys in their needs assessment and monitoring methodologies during this period. Thus nutritional data has a less significant role in the decision making process than previously had been the case.     

Planktonic bioluminescence in the pack ice and the marginal ice zone of the Beaufort Sea

An icebreaker cruise into the Beaufort Sea in the fall of 1986 provided a unique opportunity for studying planktonic bioluminescence in ice fields and in the marginal ice zone. Bathyphotometer casts (bioluminescence intensity, seawater temperature, beam attenuation coefficient, and salinity) and biological collections were made to a depth of 100 m. A light budget, which describes the planktonic species responsible for the measured bioluminescence, and a dinoflagellate species budget were constructed from the mean light output from luminescent plankton and plankton counts. The vertical distribution of bioluminescence among the ice stations was similar. The maximum intensities were 2 to 8×10⁶ photons s^-1 cm^-3 in the upper 50 m of the sea-ice interface. The marginal ice zone station (MIZ) exhibited a maximum intensity of 2 to 3×10⁸ photons s^-1 cm^-3 between 5 and 30 m depth. At Ice Station 2, Metridia longa and their nauplii contributed approximately 80% of stimulable bioluminescence in the upper 10 m but, overall, Protoperidinium spp. dinoflagellates contributed most of the light to a depth of 100 m. In the MIZ, Protoperidinium spp. dinoflagellates contributed 90% of the light within the upper 10 m, decreasing to 43% of the contributed light at a depth of 40 m. Below 40 m, dinoflagellate bioluminescence decreased to a few percent of the total to a depth of 90 m. Metridia spp. copepods contributed more than 50% of the light at depths from 40 to 90 m. Ostracods, larvaceans, and euphausiid furcilia contributed <1% of all bioluminescence at all depths sampled. Correlation analyses between measured bioluminescence (photons s^-1 cm^-3), the number of bioluminescent dinoflagellates and the light budget for the MIZ indicated highly significant associations: r=0.919, p=0.001, and r=0.912, p<0.001, respectively (Student's two-tailed t-tests). Bioluminescence was negatively correlated with seawater salinity at all stations (p=0.001). Maximum bioluminescence was measured in the less saline surface waters at all stations.     

Laboratory observations on spawning,fecundity and early development of a mesopelagic ostracod,Conchoecia pseudodiscophora,from the Japan Sea

The fate of the polycyclic aromatic hydrocarbon [³H]benzo[a]pyrene (BaP) was examined in two species of scleractinian corals, Favia fragum (Esper) and Montastrea annularis (Ellis and Solander), which were collected in the patch reefs surrounding Alina's Reef (25°23.25N; 80°09.8W) in Biscayne National Park, Florida, USA, in July, 1990. Corals were exposed to initial concentrations of 5 g/l in a simple static system for 25 h. BaP uptake was estimated from the disappearance of BaP from the water. Uptake rates were 6.5±0.7 and 10.8±0.2 g BaP cm^-2h^-1 for F. fragum and M. annularis, respectively, at initial BaP concentrations and were directly proportional to the concentration of BaP in the water. The separation of zooxanthellae from coral tissue revealed that zooxanthellae can accumulate up to 53 and 64% of the total BaP-derived radioactivity present in F. fragum and M. annularis, respectively. Both corals metabolized BaP slowly, as most of the accumulated radioactivity was present as the unmetabolized chemical. However, aqueous and organic-soluble metabolites were found in both the animal and zooxanthellae fractions. Analysis by high-performance liquid chromatography (HPLC) revealed that both species of corals metabolized BaP to various tetrols, triols, dihydrodiols, quinones and phenols, although the pattern of metabolites differed between species. Zooxanthellae contained some of the same Phase I metabolites found in the animal tissue; however, tetrols and triols were absent in extracts from the zooxanthellae. The elimination of BAP from corals was also slow; approximately 38 and 65% of the accumulated radioactivity was still present in F. fragum and M. annularis, respectively, 144 h following the transfer of exposed corals to an uncontaminated flow-through seawater system.     

The effect of nitrogen deficiency,methionine and inhibitors of methionine metabolism on the DMSP contents of Tetraselmis subcordiformis (Stein)

The unicellular alga Tetraselmis (Platymonas) subcordiformis (Prasinophyceae) displayed a two-phase increase in DMSP (dimethylsulfoniopropionate) contents in response to nitrogen deficiency. In the first phase, DMSP pools increased by 75% within 24 h. The second increase in DMSP was observed after 14 d and was accompanied by cyst formation. Methionine metabolism was involved in DMSP accumulation. A 2.6-fold increase of the DMSP pool could be induced by supplementing a complete ASP (artifical seawater Provasoli) medium with 100 M L-methionine. Inhibition of methionine utilization by T. subcordiformis caused by the addition of S-adenosylhomocystein, a competitive inhibitor of S-adenosylmethionine-dependent transmethylases, resulted in a 24% increase of DMSP contents after 7 h. DMSP accumulation after hyperosmotic shock was significantly delayed when methionine liberation from proteins was inhibited by a set of protease inhibitors. A model for the mechanism of DMSP accumulation is presented on the basis of these data and additional information from the literature. It is proposed that methionine availability in T. subcordiformis determines the rate of DMSP synthesis.     

Loch fleet: liming to restore a brown trout fishery

This project has been successful in meeting its objectives in terms of demonstrating that catchment liming techniques can restore acidified waters to conditions suitable for fish populations for relatively long periods. This improvement in conditions has extended to the inlet stream, which provides vital fish spawning and nursery areas, which are difficult to treat effectively be other means in remote locations. The project has also provided an assessment of the effectiveness of differing rates and modes of lime application, which suggest that only quite restricted parts of a catchment require treatment. This not only maximizes the cost-effectiveness of the treatments, but also helps to minimize any side-effects on, for example, moorland vegetation. The biological monitoring programme at Loch Fleet has also provided an assessment of the overall ecological consequences of adding limestone to naturally acidic and calcium-deficient ecosystems.     

Measurement of dry deposition of ammonia on a forest

Ammonia concentration gradients above a Douglas fir canopy were measured from 16 August to 31 December 1989 by two automated high-precision thermodenuders at the location Speulderbos in The Netherlands. Concentration gradients were used to calculate the dry deposition flux of ammonia via flux-gradient theory. Meteorological data were obtained from a nearby tower. Ammonia concentrations were highly variable with highest values during the night. Concentration gradients were very small during daytime and quite large at night. Median values of the calculated deposition flux and deposition velocity were 0.1 microg m(-2) s(-1) and 3.2 cm s(-1) respectively (N=1624).     

Ozone in the urban southeastern United States

Ozone measurements (daily maximum values) from the Aerometric Information Retrieval System database are analyzed for selected sites, during 1980 to 1988, in southeastern USA. Frequency distributions, for most sites during most years, show a typical bell-shaped curve with the higher frequency around the yearly daily maximum ozone mean of about 100 to about 110 microg m(-3) (50-55 ppbv). Abnormal years in ozone concentration may skew the distribution as the mean shifts. A correlation of daily maximum ozone concentrations above 140 microg m(-3) (70 ppbv) between sites shows a division between the sites in the northern protion of the region and those in the southern portion of the region. Variations in ozone levels are well correlated over distances of several hundred kilometers, suggesting that high values are associated with synoptic scale episodes. An ozone exposure analysis also shows higher ozone exposures (250-300 ppm days) in the northerly sites as compared to the southerly sites (150-170 ppm days).