Assessment of microcystins in lake water and the omnivorous fish (Carassius gibelio, Bloch) in Lake Pamvotis (Greece) containing dense cyanobacterial bloom

Toxin-producing cyanobacteria in lakes and reservoirs form a threat to humans as well as various forms of aquatic life. This study examined the occurrence and distribution of Microcystins (MCYST) in the shallow eutrophic lake Pamvotis (Greece). MCYST concentrations in the tissues (liver, kidneys, intestine, gonads, brain and muscle) of the fish species Carassius gibelio were also examined. Tests were performed with an enzyme-linked immunosorbent assay (ELISA). MCYST concentration in water and in the scum of Lake Pamvotis were highest during the warm period (April–October, 2005). Phytoplankton samples were dominated by the genera Microcystis and Anabaena during the same period. MCYST values were always below the WHO Guide level for recreational waters but much higher than the WHO Guide level for drinking water. It was found that MCYST can accumulate in the fish tissues of C. gibelio. Even though the target organ for MCYST is the liver, in our study MCYST were found also in the rest of C. gibelio tissues in the following order: intestine> kidney> > brain>gonads> muscle. Muscle tissue contained concentrations of microcystins that correspond to 0.096 μg/kg/day well above the recommended limit for human consumption (0.04 μg/Kg/day).     

Detection of microcystins in Pamvotis lake water and assessment of cyanobacterial bloom toxicity

Lake Pamvotis is a shallow, eutrophic Mediterranean lake with ecological significance. This paper deals with the evaluation of cyanobacterial toxicity in Lake Pamvotis. ELISA and HPLC revealed the presence of significant amounts of MCYST-LR. Danio rerio bioassay confirmed the toxic nature of the bloom. Cyanobacterial extracts had adverse toxic effects on development of D. rerio. Also, it was shown that cyanobacterial extracts containing environmentally detected concentrations of MCYST can cause reduced survival rate of fish species. The results clearly indicate that cyanobacterial blooms in Lake Pamvotis may be regarded as human and fish health hazard. Continuous monitoring of the lake is suggested, in order to prevent future possible intoxications.     

Assessment of hydraulic redistribution on desert riparian forests in an extremely arid area

The roots of Populus euphratica, a plant that grows in the lower reaches of the Tarim River, Northwest China, exhibit a significant level of hydraulic redistribution; however, quantitative assessments of the water-sharing process and its ecological effects are limited. This study was designed to obtain such data using an assessment model based on field observation parameters, including soil water content (soil water potential), root distribution, and stable isotope δ¹⁸O values of soil and plant samples during the entire growing season. The results showed that hydraulic redistribution in P. euphratica can be detected in 0–120 cm soil layers, with the amount of hydraulically redistributed water (HRW) in the soil found at different depths as follows: 60–80?>?40–60?>?20–40?>?0–20?>?80–100?>?100–120 cm. The variations in HRW in soil layers can be partly attributed to the vertical distribution of roots. The denser roots found at greater depths positively influenced the amount of redistributed water in lower soil layers. During the growing season, the amount of HRW reached a daily average of 0.27 mm, which allowed increased transpiration and provided an adequate water supply to herbs. Based on the stable isotope (δ¹⁸O) data, the amount of HRW provided by the roots of P. euphratica could meet 22–41 % of its water demand.     

Natural and anthropogenic controls on sediment composition of an arid coastal environment: Sharm Obhur,Red Sea,Saudi Arabia

The present study investigated the natural and anthropogenic processes that control the composition of the bottom sediments of Sharm Obhur, Red Sea. Mineralogical analysis using XRD indicated that the sediments consist of carbonate and non-carbonate minerals. Elemental interrelationships allowed differentiating two groups of elements of different sources and origin. Elements that are in the same group are positively correlated, while they correlate negatively with elements of the other group. The first group includes silicon, Al, Fe, Mn, Mg, vanadium (V), chromium (Cr), Co, Ni, Cu, and Zn, whereas the other group includes Ca, Sr, and CaCO₃. The highest concentration levels of the first group and the highest content of non-carbonate minerals were obtained from the sediments near the head of the sharm (zone A), whereas the sediments near the mouth of the sharm (zone B) yielded high concentrations of second group and carbonate minerals. Metal enrichment and contamination factors and pollution load index were calculated. The values of these indices differentiate two groups of metals: lithogenic and non-lithogenic. Except for lead (Pb) at one sampling site, metals in zone A sediments are of lithogenic source, supplied to the sharm either naturally by aeolian transportation and through Wadi Al-Kuraa'a during rare but major floods or by human activities such as dumping and shore protection. Non-lithogenic Cr, Pb, V, and Mn were documented from some sampling sites in zone B, and their occurrences are related to waste disposal and fossil fuel combustion.     

The dynamics of toxic and nontoxic Microcystis during bloom in the large shallow lake,Lake Taihu,China

Lake Taihu is a large shallow freshwater lake (surface area 2,338 km², mean depth 1.9 m) in China, which has experienced toxic cyanobacterial bloom dominated by Microcystis annually during the last few decades. In the present study, the dynamics of toxic and nontoxic Microcystis in three sampling stations (Meiliang Bay (site N2), Gonghu Bay (site N4), and the lake center area (site S4)) were quantified using quantitative real-time PCR (qPCR) during bloom periods from April to September, 2010. Our data showed that the abundance of toxic Microcystis and the toxic proportion gradually increased from April to August in water samples and reached the peak in August. During the study period, toxic Microcystis genotypes comprised between 26.2 and 64.3, between 4.4 and 22.1, and between 10.4 and 20.6 % of the total Microcystis populations in the three sampling sites, respectively. Correlation analysis suggested that there was a strong positive relationship between total Microcystis, toxic Microcystis and the toxic proportion. Chlorophyll a, total phosphorus, and water temperature were positively correlated with the abundances of total Microcystis and toxic Microcystis. Furthermore, the toxic proportion was positively correlated with total phosphorus (P?<?0.05) and water temperature (P?<?0.01), showing that global warming together with eutrophication could promote more frequent toxic blooms.     

Temporal variations of airborne particle concentration in an arid region

Airborne particle concentration (APC) measurements were carried out at the Sede Boker experimental station located in the northern Negev Desert, about 50 km south of Beer Sheva, during the years 1987--1997. The basic sampling period used in 1987--1993 was 12 h (day and night) and in 1994--1997 the sampling period was 24 h. For the entire study period, the average airborne particle concentration (APC) was 123.8 microg/m3, the highest value was 4204.2 microg/m3; and the lowest, near 5 microg/m3. For the 24 h average, about 90% of the cases were defined as normal situations (APC between 0-200 microg/m3) about, 8.5%, hazy periods (APC between 200-500 microg/m3), 1.4% dusty periods (APC between 500-1000 microg/m3) and about 0.7% were intense dusty periods (APC above 1000 microg/m3). Statistical analysis of the data showed significant seasonal and monthly fluctuations. The seasonal variation of the APC was further examined using different definitions of the seasons (astronomical, meteorological, and synoptic).     

Evaluation of usefulness of Microbial Assay for Risk Assessment (MARA) in the cyanobacterial toxicity estimation

The aim of the study was to elucidate the usefulness of the Microbial Assay for Risk Assessment (MARA) to evaluate toxicity in samples containing cyanobacterial products. Cyanobacterial extracts with different cyanotoxin contents and pure cyanotoxins—microcystin-LR, cylindrospermopsin and anatoxin-a—were tested. On the basis of the microbial reaction, MARA indicated only slight or no toxicity in the studied extracts. Similarly, no or low toxicity of pure toxins was detected at the concentrations used (up to 10 μg/ml). Weak relationships between the reactions of individual organisms exposed to cyanotoxin-containing extracts and to the same pure toxins were observed. On the other hand, inhibition of some organisms, such as Pichia anomalia, whose growth was not impacted by pure cyanotoxins, indicated the presence of other biologically active compounds in the studied extracts. In conclusion, MARA assay is not enough sensitive to be used as a good tool for cyanotoxin screening. It may, however, be applied in searching for antimicrobial/antifungal cyanobacteria-derived compounds.     

Assessment of the impact of the meteorological meso-scale circulation on air quality in arid subtropical region

In this paper, COSMO numerical weather prediction model is used to simulate land-sea breeze circulation in the north coast of Oman and to analyze the variability of the PBL depth. Typical summer day 1st August 2009 and winter day 1st January 2009 were simulated and verified by surface observations. The COSMO model was initialized using the German global model which runs as 40 km resolution and 40 vertical layers. The simulations show differences in the onset, strength, and inland penetration of the sea breeze. The high sea-land thermal contrast in the summer season induces earlier onset and progression of the sea breeze with larger horizontal and vertical extents. The summer and winter inland penetration is simulated around 150 and 65 km, respectively. The PBL depth was defined from the verticals profiles of the turbulence kinetic energy (TKE). The simulated PBL height varied at 1,600 m in summer and 700 m in the winter case. These results are in general in good agreement with the simulations of the National Centers for Environmental Prediction Global Data Assimilation System (NCEP-GDAS) model. The dispersive ability of the atmosphere was tested through the vertical mixing coefficient (VMC) generated by NCEP-GDAS simulations. The VMC during the summer simulated case is approximately four times larger than the respective one during the winter case. Consequently, during the advection of winter sea breeze, a shallow dome less than 100 m is shaped and forms an obstacle to the air-pollutant dispersion.     

Assessment of groundwater vulnerability using remote sensing,susceptibility index,and WetSpass model in an arid region (Biskra,SE Algeria)

Environmental Monitoring and Assessment - Downstream water pollution resulting from anthropogenic pressures on upstream water can cause conflicts, especially in transboundary rivers basins. This...     

Assessment of toxic heavy metals in urban lake sediments as related to urban stressor and bioavailability

Aquatic pollution pose a serious challenge to the scientific community worldwide, since lakes or reservoirs find multifarious use and most often their water is used for drinking, bathing, irrigation, and aquaculture. Nine metals and several physicochemical parameters, from four sampling sites in a tropical lake receiving the discharges from a thermal power plant, a coal mine, and a chlor-alkali industry, were studied from 2004 to 2005. Pertaining to metal pollution, the site most polluted with heavy metals was Belwadah, i.e., waters and sediments had the highest concentration of all the metals examined. The reference site was characterized by the presence of low concentrations of metals in waters and sediments. Following the water quality monitoring, 2-month field phytoremediation experiments were conducted using large enclosures at the discharge point of different polluted sites of the lake. During field phytoremediation experiments using aquatic macrophytes, marked percentage reduction in metals concentrations were recorded. The percentage decrease for different metals was in the range of 25% to 67.90% at Belwadah (with Eichhornia crassipes and Lemna minor), 25% to 77.14% at Dongia nala (with E. crassipes, L. minor and Azolla pinnata), and 25% to 71.42% at Ash pond site of G.B. Pant Sagar (with L. minor and A. pinnata). Preliminary studies of polluted sites are useful for improved microcosm design and for the systematic extrapolation of information from experimental ecosystems to natural ecosystems.     

Land-cover changes in an urban lake watershed in a mega-city, Central China

Urbanization can exert a profound influence on land covers and landscape characteristics. In this study, we characterize the impact of urbanization on land cover and lacustrine landscape and their consequences in a large urban lake watershed, Donghu Lake watershed (the largest urban lake in China), Central China, by using Landsat TM satellite images of three periods of 1987, 1993 and 1999 and ground-based information. We grouped the land covers into six categories: water body, vegetable land, forested land, shrub-grass land, open area and urban land, and calculated patch-related landscape indices to analyze the effects of urbanization on landscape features. We overlaid the land cover maps of the three periods to track the land cover change processes. The results indicated that urban land continuously expanded from 9.1% of the total watershed area in 1987, to 19.4% in 1993, and to 29.6% in 1999. The vegetable land increased from 7.0% in 1987, 11.9% in 1993, to 13.9% in 1999 to sustain the demands of vegetable for increased urban population. Concurrently, continuous reduction of other land cover types occurred between 1987 and 1999: water body decreased from 30.4% to 23.8%, and forested land from 33.6% to 24.3%. We found that the expansion of urban land has at least in part caused a decrease in relatively wild habitats, such as urban forest and lake water area. These alterations had resulted in significant negative environmental consequences, including decline of lakes, deterioration of water and air quality, and loss of biodiversity.     

Microplankton bloom in a brackish water lagoon of Terengganu

Increased primary plankton productivity was observed in a brackish water lagoon of Terengganu during the study period between January 1988 to December 1988. The lagoon is also the site for the fish cage culture activities of sea bass during the study period. An examination of water quality at the sampling stations during the study period indicated that both the organic and inorganic nutrients were high during the pre-monsoon period. The source of the nutrient in the lagoon was believed to be derived from the agro-based industrial effluents, fertilisers from paddy fields as well as untreated human and animal wastes. This coincided with the peak production of plankton in the surface waters of the brackish water lagoon. During this period both cultured and indigenous fish species were seen to suffer from oxygen asphyxiation (suffocation due to lack of oxygen). The primary productivity values ranged from 9 to 22 g/L/h during the peak period while the microplankton species were composed of diatom, flagellates and dinoflagellates. Reduction in the primary productivity values were obtained with reduction in sallinity, specially during the peak monsoon months (November to March) corresponding to the Northeast monsoon period.     

Vegetation response to hydrologic and geomorphic factors in an arid region of the Baja California Peninsula

Remotely sensed imageries were used to analyze the response of desert vegetation to physiographic factors and accumulated precipitation in drier and wetter years within a region of >16,500 km² sampled with 5,000 random pixels of 30 m. Vegetation development was indexed by the annual maximum values for greenness (SAVI) and canopy water content (NDII). Precipitation was interpolated from the 0.25° grid of the Tropical Rainfall Measurement Mission satellite-based estimates, showing a regional average of ～55 mm in the wetter year. The vegetation indices were only weakly related to total precipitation, often in a negative sense. Terrain factors that most often affected the vegetation indices, in multiple regression models, were Topographic Wetness Index, elevation, and slope gradient; these often had different signs for SAVI and for NDII. Models for NDII on intrusive igneous rocks gave better results than on extrusive igneous rocks. The strongest patterns in vegetation development were the contrast among Pacific coast, Cordillera, and Gulf coast subregions and the generally stronger results for NDII than SAVI.     

Joint application of an empirical and mechanistic model for regional lake acidification

The empirical direct distribution model for lake acidification is calibrated for use in an integrated assessment model which predicts the regional impact of an acid deposition control strategy. The calibration is based on the mechanistic Model of Acidification of Groundwater in Catchments (MAGIC). The models are applied jointly to a set of 33 statistically-selected lakes in the Adirondack region of New York. Calibration of the direct distribution model is based on a step-function application of acid deposition to MAGIC. Comparative evaluations of the resulting model predictions are made using historic deposition estimates and two alternative future deposition scenarios. The predictions of the direct distribution model match well the shapes and patterns of change of the regional distributions of ANC and pH predicted by MAGIC, the short- and medium-term dynamics of these changes, and the effect of including organic acids. However, small, long-term decreases in the fraction of incoming acid deposition neutralized by lakes and their watersheds predicted by MAGIC are not reproduced.     

Assessment of thermal stratification within stream pools as a mechanism to provide refugia for native trout in hot, arid rangelands

Native trout species, such as the redband trout (Oncorhynchus mykiss), occupy thermally harsh stream habitats in hot, arid rangeland basins of the western United States. Declines in the distribution and abundance of these species has generated interest in understanding how these cold water species survive in these systems, as well as in identifying opportunities to restore these species to their former ranges. The purpose of this study was to assess the potential for thermal stratification to provide thermal refuge for redband trout in stream pools characterized by warm intermittent flow conditions on arid rangelands. We studied vertical thermal stratification in two pools during three summers on Boles Creek located on the Modoc Plateau in extreme northeastern California. Water and air temperature data were collected on a 0.5 h time step from 15-Jun through 15-Sep during 1996, 1997, and 2000 using commercial temperature data-loggers. Water temperature was measured at the top (0.3 m below pool surface) and bottom (0.3 m above pool substrates) of each pool. Vertical thermal stratification occurred within these pools creating conditions as much as 7.6 ˚C cooler and consistently more constant at the bottom of pools compared to pool surface waters. Thermal stratification was dependent upon air temperature with the magnitude of stratification increasing as air temperature increased. The magnitude of thermal stratification varied significantly from year to year, likely reflecting variation in annual weather conditions. The thermal regime in the study pools was often near the upper lethal limit reported for redband trout, but temperatures at the bottom of these pools did offer refuge from lethal temperatures realized near the pool surface. Temperatures at pool bottom were consistently above optimal levels published for redbands.     

Assessment of microcystins in lake water and fish (Mugilidae, <Emphasis Type="Italic">Liza</Emphasis> sp.) in the largest Spanish coastal lake

Cyanobacteria dominance and cyanotoxin production can become major threats to humans and aquatic life, especially in warm shallow lakes, which are often dominated by cyanobacteria. This study investigates the occurrence and distribution of microcystins (MCYST) in water, cell-bound and in the tissues of the commercial mugilid Liza sp. in the largest, coastal, Spanish Mediterranean lake (Albufera of Valencia). This is the first report concerning microcystin accumulation in tissues of mugilid fish species. Considerable amounts of microcystins were found in the water and seston, which correlated with development of Microcystis aeruginosa populations in the lake. The MCYST concentrations found in Lake Albufera (mean 1.7 and 17 μg/L and maximum 16 and 120 μg/L in water and seston, respectively) exceeded by one to two orders of magnitude the guideline levels proposed by the World Health Organization and were higher than that reported in other lakes of the Mediterranean zone. The presence of MCYST was found in all the fishes studied and accumulated differently among tissues of the commercial species Liza sp. Toxin accumulation in fish tissues showed that although the target organ for MCYST was the liver, high concentrations of microcystins were also found in other analysed tissues (liver>intestine>gills>muscle). Human tolerable daily intake for microcystins is assessed relative to the WHO guidelines, and potential toxicological risks for humans, wildlife and related ecosystems of the lake are discussed.