Use of Biotic Community Structure as a Measure of Ecological Degradation

The benthic macroinvertebrate communities of two lotic aquatic habitats,namely,the Churni River(C-R)and the Jalangi River(J-R)were compared in this study.One lotic aquatic system(C-R)was polluted by organic pollutants due to discharge of unprocessed sewage water,while the other(J-R)was not affected by such pollution.Evaluations of various physico-chemical properties of water,sediment and different macroinvertebrate communities of the two tropical lotic systems were done in a period from January,2002 to December,2003.A long term temporal change in the macroinvertebrate communities was recorded due to increase in sediment rH value.Sediment redox potential affected by the anthropogenic activities was found to be an important factor for alteration of macroinvertebrate communities in these aquatic ecosystems.A positive correlation has been established between rH and Margalef index in this study.Potassium and the total count of coliform bacteria in water showed significantly higher values for the polluted Churni River than those for the Jalangi River.Fig 3,Tab 4,Ref 34     

Effect of low salinity on the activity,feeding, growth and absorption efficiency of Luidia clathrata (Echinodermata: Asteroidea)

Exposure of Luidia clathrata (Say) to low salinity (17 S) results in a decrease in activity and rate of feeding, but has little effect on the absorption efficiency. Growth, as indicated by changes in body size and energy content of the body wall and pyloric caeca, is reduced in low salinity due to a decrease in feeding rate (energy consumption) and to a decrease in efficiency of utilization of material and energy absorbed. The low efficiency indicates that either additional energy is required for maintenance or energy is used inefficiently in low salinity. Thus, L. clathrata is limited energetically in low salinities, although it lives and reproduces there.     

DCMU-enhanced fluorescence as an index of photosynthetic activity in phytoplankton

Tests have been carried out, both on phytoplankton cultures and in the field, on the relation between the ratio of 3-(3,4-dichlorophenyl)-1,1-dimethyl urea (DCMU)-enhanced to normal fluorescence (F _D /F _N ) and the specific photosynthetic rate (P/B). In all cases observed, significant linear correlations were found between these two values. Differences in this relation were observed according to species and physiological conditions. Nutrient stress that occurs in batch cultures decreases both F _D /F _N and P/B, while lowered light intensity has a different effect on both, increasing F _D /F _N and decreasing P/B. This is interpreted as indicating that F _D /F _N is an index of photosynthetic efficiency at different light levels and an indicator of the specific photosynthetic rate (P/B) when physiological conditions vary at a given light intensity. The practical use of DCMU-enhanced fluorometry to estimate instantaneous P/B values in the field is discussed, stressing the frequent calibrations needed, as in all in situ fluorometry studies.     

Numbers,biomass, and caloric content of the echinoderm fauna of the rocky shores of Barbados

The high-energy windward coasts with narrow rocky intertidal regions (Oistens, River Bay) at Barbados, West Indies, had abundant macroscopic algae (mainly Sargassum sp.) and populations of Holothuria glaberrima Selenka and Echinometra lucunter (Linnaeus), while protected ones with a wide rocky intertidal had sparse macroscopic algae and populations of E. lucunter only. The low-energy leeward coasts with wide rocky intertidal regions (Six Men's Bay, Payne's Bay) had no macroscopic algae in the surf zone and populations of E. lucunter only. Numerical densities of E. lucunter were high in all localities; the highest level of 144 m^-2 was found at Six Men's Bay; numerical densities of H. glaberrima were high at both Oistens and River Bay, the highest level of 36 m^-2 being recorded at River Bay. The caloric density of H. glaberrima at River Bay was 412 kcal m^-2. The highest combined density of H. glaberrima and E. lucunter was at Oistens (632 kcal m^-2, with 254 kcal m^-2 being due to E. lucunter). The highest caloric density of E. lucunter at Six Men's Bay was 482 kcal m^-2. Dependence on suspended food probably restricts H. glaberrima to high-energy environments while E. lucunter has an additional food source through its ability to scrape the rock substratum. E. lucunter may be more efficient in catching drift food. Mortality is suggested to be the basis of the failure of E. lucunter to displace H. glaberrima from the high-energy location.     

Tiger shark (Galeocerdo cuvier) abundance and growth in a subtropical embayment: evidence from 7 years of standardized fishing effort

The tiger shark (Galeocerdo cuvier Peron and Lesueur 1822) is a widely distributed predator with a broad diet and the potential to affect marine community structure, yet information on local patterns of abundance for this species is lacking. Tiger shark catch data were gathered over 7 years of tag and release research fishing (1991–2000, 2002–2004) in Shark Bay, Western Australia (25°45′S, 113°44′E). Sharks were caught using drumlines deployed in six permanent zones (~3 km² in area). Fishing effort was standardized across days and months, and catch rates on hooks were expressed as the number of sharks caught h⁻¹. A total of 449 individual tiger sharks was captured; 29 were recaptured. Tiger shark catch rate showed seasonal periodicity, being higher during the warm season (Sep–May) than during the cold season (Jun–Aug), and was marked by inter-annual variability. The most striking feature of the catch data was a consistent pattern of slow, continuous variation within each year from a peak during the height of the warm season (February) to a trough in the cold season (July). Annual growth rates of recaptured individuals were generally consistent with estimates from other regions, but exceeded those for populations elsewhere for sharks >275 cm fork length (FL), perhaps because mature sharks in the study area rely heavily on large prey. The data suggest that (1) the threat of predation faced by animals consumed by tiger sharks fluctuates dramatically within and between years, and (2) efforts to monitor large shark abundance should be extensive enough to detect inter-annual variation and sufficiently intensive to account for intra-annual trends.     

Studies on phytotoxic effect of aluminium on growth and some morphological parameters of Vigna radiata L. Wilczek

Aluminium toxicity is a major deterrent for plant growth in acid soils below pH 5.0. This study deals with effect of aluminium toxicity on growth of mungbean (Vigna radiata L. Wilczek) seedlings. Seed germination (in %) declined with increased content of Al2(SO4)3, while promotive effect was observed at very low dosage. Different concentrations of aluminum sulphate salt were applied to mungbean seeds. Measurement of aluminium content in mungbean leaves was done through atomic absorption spectrophotometer. Root length (root and hypocotyl length) and shoot length (shoot and epicotyl length) was measured at seven days old seedling stage. Different concentrations of Al2(SO4)3 were found to have significant effect both on shoot and root length. Leaf area, fresh and dry weight was significantly reduced. Increased stomatal frequency and trichome density with an increase in concentrations of Al2(S04)3 was observed through scanning electron microscope.     

Regression modelling of hourly NOx and NO2 concentrations in urban air in London

Based on hourly measurements of NO_x NO₂ and O₃ and meteorological data, an ordinary least squares (OLS) model and a first-order autocorrelation (AR) model were developed to analyse the regression and prediction of NO_x and NO₂ concentrations in London. Primary emissions and wind speed are the most important factors influencing NO_x concentrations; in addition to these two, reaction of NO with O₃ is also a major factor influencing NO₂ concentrations. The AR model resulted in high correlation coefficients (R > 0.95) for the NO_x and NO₂ regression based on a whole year's data, and is capable of predicting NO₂ (R = 0.83) and NO_x (R = 0.65) concentrations when the explanatory variables were available. The analysis of the structure of regression models by Principal Component Analysis (PCA) indicates that the regression models are stable. The results of the OLS model indicate that there was an exceptional NO₂ source, other than primary emission and reaction of NO with O₃, in the air pollution episode in London in December 1991.     

Nontransmission of deoxynivalenol (vomitoxin) to milk following oral administration to dairy cows

The absorption of deoxynivalenol (DON; vomitoxin), a trichothecene mycotoxin produced by Fusarium species, was studied in the dairy cow. Serum and milk DON levels were quantitated following a single oral dose of 920 mg DON to each of two lactating cows of similar weight. Maximum blood levels for the two animals following DON administration were 200 and 90 ng/ml serum, occurring at times 4.7 and 3.5 hr, respectively. By 24 hr after dosing only trace levels (less than 2 ng/ml) were still detectable. DON in its conjugated form accounted for 24-46% of the total levels present in serum. Free and conjugated DON were also present in cow's milk, but only extremely low amounts (less than 4 ng/ml) were detected. Detection of DON was carried out utilizing Sep-Pak C18 extraction cartridges for isolation, with additional purification of the sample achieved by passing the extract through a short charcoal/alumina column. The extract was then reacted with N-heptafluorobutyrylimidazole prior to quantitation of the resulting DON-tris-heptafluorobutyrate derivative by combined gas chromatography-quadrupole mass spectrometry, using multiple selected ion monitoring. Detection limits were as low as 1 ng/ml (1 ppb).     

Assessment of the potential for soil acidification in North India using the critical load approach and locally derived data for acidic and basic inputs

Major ions (Cl-, NO3(-), SO4(2-), Ca2+, Mg2+, Na+, K+ and NH4(+)) were analysed in wet and dry deposition samples collected for 2 years using a polyethylene bottle and funnel collector at Agra in India. The deposition of ionic components (Ca2+ and Mg2+) derived from natural sources i.e. soil were higher than those of anthropogenic origin. In rainwater samples, non-sea-salt fraction was found to be 60-90%. In both wet and dry deposition Ca2+ was found to be the dominant ion which may be due to its large particle diameter. Results suggest that most of the acidity, which occurs due to NO3(-), SO4(2-) and Cl- is neutralized by alkaline constituents, which originate from airborne local soil and dust transported from the Thar desert. Acid neutralizing capacity of soil has also been quantified and found to be 33 x 10(3) neqg(-1). Using deposition data, the critical load for acidity of soil with respect to Ashoka and Eucalyptus was evaluated. The present level of deposition of S and N was found to be much lower than critical loads calculated for S and N. Critical load of exceedance in terms of deposition acidity was also calculated and found to be negative. This indicates that with respect to these species, the ecosystem is protected at the current level of deposition.