The colonization of periphytic diatom species on artificial substrates in the Ashar canal, Basrah, Iraq

Studies have been conducted between March 1993 and March 1994 in the Ashar canal, a backwater of the Shatt al-Arab River, Iraq. Using artificial substrates, the colonization and development of seventy-five diatom species belonging to twenty genera could be revealed. Taxa apportionment varied seasonally as well as within each season. A few species have been found during all experiments. These are Amphora ovalis, Bacillaria paradoxa, Cocconeis placentula var. euglypta, Cyclotella meneghiniana, Cymbella ventricosa, Navicula tripunctata var. schizonemoides, Rhoicosphenia curvata, and Synedra ulna. The occurrence of B. paradoxa in Experiment 1 (March-April 1993) and Experiment 4 (end of January to beginning of March 1994) was higher than 50%. Similarity of species increased towards the end of each season, and the communities from experiments 1 and 4 were more similar than others. The experiments also suggest that week 4 represents the equilibrium phase while week 6 reflects the increase in biological interactions. The results could also indicate the sequence of primary colonizers and the community development towards the equilibrium.     

Southern Oscillation simulation in the OSU coupled upper ocean-atmosphere GCM

The Southern Oscillation is a major component in the interannual variations of global climate. The Oregon State University global climate model, with a dynamically interactive upper ocean, reproduces in qualitatively correct fashion some of the major characteristics of the Southern Oscillation. This model simulates the observed anti-correlation of annually averaged sea-level pressure (SLP) between the eastern Pacific and the Indonesian region, the primary atmospheric signal of the Southern Oscillation. In the composite of the simulated warm events positive sea-surface temperature (SST) anomalies expand eastward towards South America from the tropical western Pacific during the first half of the calendar year. The SST anomalies develop in conjunction with eastward mixed layer current anomalies in the tropical Pacific. In the late summer and early fall anomalously warm water near South America develops and moves westward to merge with the central Pacific anomalies. This lagged development in the eastern Pacific is analogous to the evolution of the 1982/83 and 1986/87 El Ninos. The temperature of the thermocline layer also increases, with the slope of the equatorial Pacific thermocline decreasing in response to the relaxation of the surface forcing. Enhanced precipitation occurs in the mid-Pacific while in the Indian and Australian monsoon regions a deficit occurs. The peak of the warm phase occurs in late northern fall/early winter, somewhat earlier than during observed El Ninos. The cold phase of the Southern Oscillation, enhancement of the zonal circulation, evolves in a fashion similar to the warm phase with the signs of the anomalies reversed, similar to observations. Occurrence of Southern Oscillation in this coarse resolution GCM indicates that high resolution ocean waves do not play a crucial role in the generation of this phenomenon as suggested by Pacific basin models. These results also show that ocean-atmosphere global climate models are useful tools for investigation of time dependent changes on the interannual timescale in addition to their hitherto accepted use for studying equilibrium properties of climate.     

Cultural characteristics of chromium resistant unicellular cyanobacteria isolated from local environment in Pakistan

Many unicellular cyanobacteria were isolated from different places： fields, ponds, polluted water, and soils from Muredkey and Kasur tannery areas, near Lahore, Pakistan. Different media like BG 11 medium, Bold Basal medium, Chu＇s # 10 medium and Gotham＇s medium, in standard forms and with slight variations of ingredients, and different pH, temperature and light regimes were checked for the optimum growth of the isolates. The isolation pro- cedure was repeated with different concentrations of chromium to select the resistant strains. These selected strains grew on chromium of the range 100-200 μg/ml in BG 11 medium. Cyanobacteria were maintained in solid and liquid media with/without shaking. Cyanobacterial strains were collected from natural habitats that were accompanied by a diversified group of organisms including bacteria, protozoan, and rotifers etc. In order to eliminate these agents termed as contaminants, we used several methods including phenol treatment, use of antibiotic and careful manual picking of unicellular cyanobacteria. Resistance of these strains against different heavy metals （ZnSO4, MnSO4, NiSO4, COCl2, Pb（NO3）3, CuSO4, HgCl2, AgNO3 and CdCl2） and antibiotics （erythromycin, streptomycin, kanamycin, chloramphenicol, neomycin） was evaluated. Optimum temperature was 30℃ with variable pH for the reduction of Cr^6＋ in to Cr^3＋ in majority of strains.     

Petrology and geochemistry of Jura granite and granite gneiss in the Neelum Valley,Lesser Himalayas (Kashmir,Pakistan)

Late Proterozoic rocks of Tanol Formation in the Lesser Himalayas of Neelum Valley area are largely green schist to amphibolite facies rocks intruded by early Cambrian Jura granite gneiss and Jura granite representing Pan-African orogeny event in the area. These rocks are further intruded by pegmatites of acidic composition, aplites, and dolerite dykes. Based on field observations, texture, and petrographic character, three different categories of granite gneiss (i.e., highly porphyritic, coarse-grained two micas granite gneiss, medium-grained two micas granite gneiss, and leucocratic tourmaline-bearing muscovite granite gneiss), and granites (i.e., highly porphyritic coarse-grained two micas granite, medium-grained two micas granite, and leucocratic tourmaline-bearing coarse-grained muscovite granite) were classified. Thin section studies show that granite gneiss and granite are formed due to fractional crystallization, as revealed by zoning in plagioclase. The Al saturation index indicates that granite gneiss and granite are strongly peraluminous and S-type. Geochemical analysis shows that all granite gneisses are magnesian except one which is ferroan whereas all granites are ferroan except one which is magnesian. The CaO/Na₂O ratio (>0.3) indicates that granitic melt of Jura granite gneiss and granite is pelite-psammite derived peraluminous granitic melt formed due to partial melting of Tanol Formation. The rare earth element (REE) patterns of the Jura granite and Jura granite gneiss indicate that granitic magma of Jura granite and Jura granite gneiss is formed due to partial melting of rocks that are similar in composition to that of upper continental crust.     

Prediction of nearshore wave heights using a refraction programme

The Dobson wave refraction programme, modified to incorporate bottom frictional attenuation, is being tested for its universal applicability for prediction of nearshore wave heights. An investigation has been undertaken to test the applicability of this programme for the prediction of wave heights over a gently sloping, wide continental shelf. The study has been carried out in the shelf waters off Alleppey, situated along the southwest coast of India. The measured wave height at a nearshore point and the computed wave height at the same point are compared. The application of Spearman's rank correlation and Wilcoxon's matched-pairs signed-ranks test has indicated that there is a high degree of correlation between the measured and predicted heights. Since similar results have been obtained by Bryant (1979) for steep shelf waters of Australia, it may be concluded that the programme can be used in different coastal waters irrespective of the nature of the shelf gradient, but subject to other limitations of the programme.     

The North Pacific Oscillation: observations compared with simulations in a general circulation model

The study of the sea level pressure and the surface air temperatures in the North Pacific region in a 23-year integration of the Oregon State University coupled ocean-atmosphere general circulation model has shown that there is a signature of the North Pacific Oscillation in the model, comparable to that recorded in observations. In the model, the NPO index was defined in terms of an opposition in sign of mean temperature anomaly between two regions in the North Pacific region, close to those found in observations (viz. Dutch Harbor, Alaska, and Edmonton, Canada). Fluctuations of this index prompted the grouping of some of the 23 model years as those when the temperature at the model equivalent of Dutch Harbor was above normal and that at the model equivalent of Edmonton below normal (analogous to Aleutian above in observations), while other years displayed the opposite scenario (Aleutian below). Composites of sea level pressure, surface air temperatures, precipitation and sea surface temperatures in the Northern Hemisphere were found to be at times strikingly similar to those documented in observations by Rogers.     

Wave height distribution in shallow water

Probability distribution of shallow water wave heights, obtained from a pressure type recorder, are examined. It is tested with the theoretical distributions of (a) Rayleigh, (b) Weibull, (c) Gluhovski, (d) Ibrageemov and (e) Goda. The best fit is shown by the Gluhovski probability density function with a correlation coefficient greater than 0.8. The functions of Weibull, Ibrageemov and Goda fit only half of the tested cases. The role of wave steepness in the wave height distribution is found to be negligible.     

A model investigation of the impact of increases in anthropogenic NO x emissions between 1967 and 1980 on tropospheric ozone

Recent observations suggest that the abundance of ozone between 2 and 8 km in the Northern Hemisphere mid-latitudes has increased by about 12% during the period from 1970 to 1981. Earlier estimates were somewhat more conservative suggesting increases at the rate of 7% per decade since the start of regular observations in 1967. Previous photochemical model studies have indicated that tropospheric ozone concentrations would increase with increases in emissions of CO, CH₄ and NO _x . This paper presents an analysis of tropospheric ozone which suggests that a significant portion of its increase may be attributed to the increase in global anthropogenic NO _x emissions during this period while the contribution of CH₄ to the increase is quite small. Two statistical models are presented for estimating annual global anthropogenic emissions of NO _x and are used to derive the trend in the emissions for the years 1966–1980. These show steady increase in the emissions during this interval except for brief periods of leveling off after 1973 and 1978. The impact of this increase in emissions on ozone is estimated by calculations with a onedimensional (latitudinal) model which includes coupled tropospheric photochemistry and diffusive meridional transport. Steady-state photochemical calculations with prescribed NO _x emissions appropriate for 1966 and 1980 indicate an ozone increase of 8–11% in the Northern Hemisphere, a result which is compatible with the rise in ozone suggested by the observations.     

High-resolution records of the response of coastal wetland systems to long-term and short-term sea-level variability

While it is well known that coastal systems respond to long-term sea-level changes, the importance of short-term sea-level dynamics is often overlooked. Year-to-year variability in annual mean sea level along the North American Atlantic coast is part of a regionally consistent pattern that is coupled to low atmospheric pressure and high wind field anomalies persisting over 100s to 1000s of km. These short-term sea-level dynamics, along with long-term sea-level changes are shown to be closely coupled to a set of high resolution excess ²¹⁰Pb geochronologies from four physiographically distinct salt marsh estuaries surrounding Long Island, NY, USA. However, the degree to which a marsh responds to either forcing depends on its physiographic setting. Accretion and mineral deposition rates in marshes situated in embayments with long fetches and low-tidal ranges are shown to respond most to the short-term dynamically driven changes in sea level. On the other hand, accretion and mineral deposition in a marsh in an embayment with a high-tidal range and reduced fetch best track the long-term changes in mean sea level, presumably because the physiography limited the meteorological drivers of short-term sea-level change. The close coupling between marsh accretion, physiographic setting and indices of sea-level change indicates that these coastal system respond both differently and rapidly (2–5 yr) to climate variability.