Chemotaxonomic investigation of phytoplankton in the shelf ecosystem of the KwaZulu-Natal Bight,South Africa

Phytoplankton community structure was elucidated during summer and winter in the KwaZulu-Natal Bight using pigment and CHEMTAX analyses. The surface pattern in January 2010 indicated that diatoms, haptophytes and prasinophytes tended to be the most prominent groups inshore and in the southern sector of the bight, whereas Prochlorococcus and Synechococcus were more dominant in the north and towards the offshore region. At the deep chlorophyll maximum (DCM), diatoms were dominant in the inner bight and in the south, with prasinophytes being the prominent flagellates, but this changed to Prochlorococcus and pelagophytes being the important groups in the northern sector and outer part of the bight. A different pattern was observed at the surface in July 2010, where diatoms, haptophytes, prasinophytes and cryptophytes in varying proportions comprised most of the community in the inner half of the bight, whereas Synechococcus and haptophytes were the main groups in the outer sector. A similar pattern occurred at the DCM, except that Synechococcus was less prominent and pelagophytes were distributed across the bight in both the inshore and offshore zones. Observations and relationships between phytoplankton groups and environmental parameters indicated that the groups were most closely related to temperature, accounting for 24–64% of the deviance. The influence of nutrients on phytoplankton was less clear but nitrate and silicate seemed to account for some of the patchy distribution patterns.     

Antibiotic resistance in coliform and faecal coliform bacteria from natural waters and effluents

Coliform and faecal coliform bacteria isolated from potable water supplies (springs and wells), streams, seawater, and effluents were examined for the incidence of antibiotic resistance. More than 40% of the coliform and faecal coliform bacteria isolated from drinking water supplies were resistant to one or more antibiotics. In stream and seawater samples, the incidence was increased to more than 60%, and to more than 70% among faecal coliforms isolated from effluents. Approximately 40% of the isolates resistant to streptomycin or tetra‐cycline were able to transfer their resistance determinants to an antibiotic‐sensitive strain of Escherichia coli within 2 h.

Although the widespread use of antibiotics is perhaps the major selective force favouring the increased incidence of antibiotic‐resistant bacteria, antibiotic‐resistant faecal coliforms may also have a selective advantage in natural waters.     

Involvement of anti-oxidative enzymes, photosynthetic pigments and flavonoid metabolism in the adaptation of Reaumuria soongorica to salt stress

Reaumuria soongorica is a short woody shrub widely found in semi-arid areas of China. It can survive severe environ- mental stress including high salinity in its natural habitat. Thus, we investigated the involvement of anti-oxidative enzymes, photosynthetic pigments and flavonoid metabolism in the adaptation of R. soongorica to saline environments. R. soon- gorica was treated with 0, 100, 200 and 400 mM NaC1 solutions for 14 days. Soil salt content increased significantly by watering with high content of NaC1 solution, and no variation between 8 and 14 days during treatment. The levels ofpe- roxidation of lipid membranes （measured by malondialdehyde content） and the activities of three antioxidant enzymes （superoxide dismutase （SOD）, peroxidase （POD） and ascorbate peroxidase （APX）） increased under salt stress. Chlorophyll and carotenoid content decreased with increasing salt content. The ratio of Chl a/Chl b and carotenoid/Chl exhibited sig- nificant increase under 400 mM NaC1. However, total flavonoid and anthocyanin contents and key enzyme activities in the flavonoid pathway including phenylalanine ammonialyase （PAL） and Chalcone isomerase （CHI） decreased under salt stress. These findings possibly suggest that R. soongorica has an adaptation protection mechanism against salt-induced oxidative damage by inducin~ the activity of antioxidant enzymes and maintaining a steady level of carotenoid/Chl.     

Lacustrine organic matter and the Holocene paleoenvironmental record of Lake Albano (central Italy)

A combined bulk and detailed geochemical study of the sedimentary organic matter in Lake Albano, central Italy, provides critical data to track the response of this aquatic system to the environmental changes of variable amplitude that occurred during the Holocene. RockEval pyrolysis of this predominantly laminated, organic carbonrich sedimentary sequence shows changes in hydrogen and oxygen indices that are related to variations in the dominance of the primary producers. These variations are further confirmed by the pigments and the carbon isotopic composition of bulk organic matter showing that cyanobacteria dominated the lake waters during the early and late Holocene whereas diatoms have been the main producers during the middle Holocene. Sharp decreases in productivity, 2–3 centuries long, are identified at ca. 8.2, 6.4 and 3.8 ka. B.P. Changes in temperature and/or effective moisture are suggested as the most probable causes, although human impact cannot be ruled out for the latest part of the Holocene.     

A multi-proxy analysis of climate impacts on the recent development of subarctic Lake Saanajärvi in Finnish Lapland

Responses to recent climatic changes in the sediment of subarctic Lake Saanajärvi in northwestern Finnish Lapland are studied by comparison of various biological and sedimentological proxies with the 200-year long climate record, specifically reconstructed for the site using a data-set of European-wide meteorological data. The multi-proxy evidence of simultaneously changing diatom, Cladocera, and chrysophyte assemblages along with the increased rates of organic matter accumulation and pigment concentrations suggest that the lake has undergone a distinct typological change starting from the turn of the 20th century. This change, indicating an increase in lake productivity, parallels a pronounced rise in the meteorologically reconstructed mean annual and summer temperatures in the region between ca. 1850 and 1930's. We postulate that, during the Little Ice Age, the lake was not, or was only weakly, thermally stratified during summer, whereas the subsequent increase in air and hence epilimnetic water temperatures resulted in the development of the present summer stratification. The increased thermal stability of the lake created more suitable conditions for the growth of phyto- and zooplankton and changed the overall primary production from benthos to plankton. Mineral magnetic and carbonaceous particle records suggest long-distance pollution, particularly since the 1920's, yet the observed changes in lake biota and productivity can hardly be explained by this very minor background pollution; the 20th century species configurations are typical of neutral waters and do not indicate any response to pollution.     

High-resolution analyses of recent sediments from a Norwegian mountain lake and comparison with instrumental records of climate

The purpose of the palaeolimnological research project carried out at Øvre Neådalsvatn was to apply a number of physical and biological proxy-climate analyses to recent sediments and to compare the results of these analyses with instrumental records of climate. Using a radiometric chronology to match the sediment core with the calendar ages of the reconstructed instrumental record, and by time-averaging the instrumental record, the statistical significance of the relationships between each of the sediment-climate proxies and the reconstructed instrumental-climate measurements were evaluated.Acid deposition at Øvre Neådalsvatn has been low and its impact limited. Whilst there has been an overall rise in mean annual temperature of about 1 °C since 1900, the physical and biological sediment records studied appear to be insensitive to climate warming of this magnitude. On the one hand, this may be a result of the loss in temporal resolution caused by time-averaging the instrumental data; on the other hand, the lake may be insensitive to the impact of this climate change.     

Photosynthetic pigments accumulation and some growth indices of cowpea, maize and tomato in response to interspecific and intraspecific competition stress

This study aimed at investigating the photosynthetic pigment accumulation and some growth indices of cowpea, maize and tomato in response to interspecific and intraspecific competition stress. The study was carried out under a screen-house to minimize extraneous factors such as pests and rodents using a randomized complete block design(RCBD). Seeds of cowpea, maize and tomato were collected from the Department of Crop Production and Protection, Faculty of Agriculture,Obafemi Awolowo University, Ile Ife, Osun state, Nigeria. These seeds were planted at a depth of about 3 mm below the soil. The seeds were sown at the rate of six seeds per pot in the monoculture, while in the pots designed for the mixed culture of maize and cowpea, maize and tomato, cowpea and tomato, three seeds of each plant were sown. Two seeds of each plant were sown in the pots with the three crops. The treatments were then supplied with 500 m L of tap water in the morning and in the evening respectively until the seedlings become fully established. The photosynthetic pigments were determined spectrophotometrically with three replicates. Plant growth indices were determined according to Hunts(1978) using leaf area and dry matter data collected at four and six weeks after planting. Statistical analysis was performed using statistical analytical software SAS version 9.2. The results indicated that photosynthetic pigments accumulation(Chlorophyll a, b and carotenoid) in maize(15.98, 23.92 and 44.72 μM), Chlorophyll b and carotenoid in tomato plants(12.48 and 1,178.7μM) in the sole stands were more than the mixed culture of maize with cowpea and tomato(7.195, 14.74 and 0.00 μM).Also, total Chlorophyll in maize(1,127.8 μM), Chlorophyll a and total Chlorophyll in tomato(3.95 and 1,317.5 μM) in the mixed culture were more than in the sole culture of maize(1,030.9 μM) and tomato plants(-9.40 and 546.3 μM). The different photosynthetic pigments accumulated in cowpea were greatly enhanced in the mixed culture than in the sole culture.All the photosynthetic pigments of maize, cowpea and tomato in all the treatments analysed in this study were significantly different at P0.05. Plant growth indices such as net assimilation rate, relative growth rate, crop growth rate and tissue water contents of these plants had higher value in the intercropped than the check crop(sole). These plant growth indices were significantly different to one another at P0.05. This study concluded that competition for shared resources in the mixed culture of tomato, maize and cowpea enhanced growth and accumulation of photosynthetic pigments.     

The environmental history of a mountain lake (Lago Paione Superiore, Central Alps, Italy) for the last c. 100 years: a multidisciplinary, palaeolimnological study

A palaeoecological study of an oligotrophic alpine lake, Paione Superiore (Italy), provided a record of historical changes in water quality. Historical trends in lake acidification were reconstructed by means of calibration and regression equations from diatoms, chrysophycean scales and pigment ratios. The historical pH was inferred by using two different diatom calibration data sets, one specific to the alpine region. These pH trends, together with the record of sedimentary carbonaceous particles and chironomid remains, indicate a recent acidification of this low alkalinity lake.Concentration of total organic matter, organic carbon, nitrogen, biogenic silica (BSiO₂), chlorophyll derivatives (CD), fucoxanthin, diatom cell concentration and number of chironomid head capsules increased during the last 2–3 decades. When expressed as accumulation rates, most of these parameters tended to decrease from the past century to c. 1950, then all except P increased to the present day. A marked increase in sedimentary nitrogen may be related to atmospheric pollution and to the general increases in output of N in Europe. High C/N ratios indicate a prevailing allochthonous source of organic matter.Finally, the increase in measured air temperature from the mid-1800's appeared to be related to lake water pH before industrialization: cold periods generally led to lower pH and vice-versa. The more recent phenomenon of anthropogenic acidification has apparently decoupled this climatic-water chemistry relationship.     

有机锡对海洋微藻的生理效应 Ⅰ.三苯基锡和三丁基锡对光合色素含量的影响

于1991年4月－1992年五月，以金藻和扁藻为材料，用室内一次培养法研究三苯基锡（TPTC）和三丁基锡（TBTC）化合物对光合色素含量的影响。结果表明，两种有机锡对两种藻均有影响，在0．2—0．4μg／L的浓度时有轻微毒性；浓度大于0．5μg／L时，能使光合色素明显减少。对于两种藻叶绿素a72hEC50影响结果：TBTC和TPTC对金藻的均为0．59μg／L；对扁藻的，TBTC是0．87μg／L，而TPTC本出现半效应浓度。对于两种藻的类胡萝卜素72hEC50影响结果：金藻，TPTC是0．57μg／L，TBTC是0．49μg／L；扁藻，TBTC是0．89μg／L，TPTC也未出现半效应浓度。认为，两种有机锡对光合色素有明显的破坏作用。     

厦门港海水光合色素特征

应用反相高效液相色谱（RP-HPLC）方法分析测定了冬季厦门鼓浪屿水文观测站两周内不同潮位海水中的光合色素的组成与含量，包括多甲藻素、19‘-已酰基氧化岩藻黄素、硅甲藻黄素、硅藻黄素、玉米黄素、叶绿素a、脱镁叶绿素a、β-胡萝卜素等。同时还实测了小于藻、金藻、盐藻、甲藻、角毛藻、螺旋藻等多个实验室培养藻种的色素组成。数据表明，不同种类的藻类具有不同的色素组成特征，从海水中光合色素的分析数据可推测其浮游植物主要种类组成情况。潮汐的水动力情况在色素组成变化上有所反映，表明港内外的乳游植物组成分布有梯度存在，且在特征上有所不同。