A comparison of PCB bioaccumulation factors between an arctic and a temperate marine food web

To test how environmental conditions in the Arctic and the resulting ecological adaptations affect accumulation of persistent organic pollutants (POPs) in the marine food web, bioaccumulation of four polychlorinated biphenyls (PCBs) in an arctic (Barents Sea 77 °N-82 °N) and a temperate marine (Baltic Sea 54 °N-62 °N) food web were compared. Three different trophic levels were studied (zooplankton, fish, and seal), representing the span from first-level consumer to top predator. Previously published high-quality data on PCB water concentrations in the two areas were used for calculation of bioaccumulation factors (BAF). BAF was calculated as the ratio of the PCB concentration in the organism ([PCB]_org; pg/kg lipid) to the dissolved water concentration (C_w; pg/L). The BAF_Arctic:BAF_Temperate ratios were above 1 for all four PCB congeners in zooplankton (6.4-13.8) and planktivorous fish (2.9-5.0)), whereas the ratios were below 1 in seal. The mean ratio between arctic and temperate BAFs for all trophic levels and congeners (BAF_Arcti:BAF_Temperate) was 4.8. When the data were corrected for the seawater temperature difference between the two ecosystems, the ratio was 2.0. We conclude that bioaccumulation differences caused by ecological or physiological adaptations of organisms between the two ecosystems were well within a water concentration variability of 50%. Further, our data support the hypothesis that lower seawater temperature lead to a thermodynamically favoured passive partitioning to organic matrices and thus elevated ambient BAFs in the Arctic compared to the Baltic Sea. This would imply that bioaccumulation in the Arctic may be described in the same way as bioaccumulation in temperate regions, e.g. by the use of mechanistic models parameterised for the Arctic.     

Harmful effects of un-ionised ammonia on the zooplankton community in a deep waste treatment pond

The harmful effects of NH(3) on the zooplankton community in a deep waste treatment pond were evaluated under natural conditions. The pond, supplied with secondary effluent from a conventional urban wastewater treatment plant, was designed to improve water quality for agricultural reuse.The aim of the study was to verify the hypothesis suggested in Arauzo et al. (Water Environ. Res. 34(14), 3666) that during phytoplankton blooms in the stratification periods high un-ionised ammonia content values, due to an intense photosynthetic activity and high related pH, lead to a decrease in zooplankton biomass and, thus, to a collapse of the treatment process efficiency.Empirical models were developed to determine relationships between phytoplankton biomass, pH and NH(3) levels. They provided an easy and quick method of detecting when the system was liable to collapse due to the NH(3) effect on the zooplankton community and offered the possibility of adopting measures to guarantee water quality at the effluent. A significant decrease in zooplankton community biomass was observed at un-ionised ammonia levels over 2.5 mgL(-1).     

Fall Composition of Storage Lipids is Associated with the Overwintering Strategy of <Emphasis Type="Italic">Daphnia</Emphasis>

Diapause, which occurs through the production of dormant eggs, is a strategy used by some zooplankton to avoid winter months of persistent low temperatures and low food availability. However, reports of active zooplankton under the ice indicate that other strategies also exist. This study was aimed at evaluating whether the composition of storage lipids in the fall differs between diapausing and active overwintering Daphnia. We assessed the quantity of storage lipids and fatty acid (FA) composition of Daphnia species, along with FA content of seston, in six boreal, alpine and subarctic lakes at the onset of winter, and evaluated the association between storage lipids and Daphnia overwintering strategy. We found that active overwintering Daphnia had >55% body fat and the highest FA concentrations. Polyunsaturated FA, especially stearidonic acid (18:4n-3; SDA) and high ratios of n-3:n-6, were preferentially retained to a greater extent in active overwintering Daphnia than in those that entered diapause. Daphnia FA composition was independent of that of the seston diet, indicating that Daphnia adjusted their storage lipids according to the physiological requirements of a given overwintering strategy. The occurrence of an active overwintering strategy has consequences for zooplankton community structure, and can have important implications for the transfer of high-quality energy at higher trophic levels.     

基于eDNA 和形态学的九江市城市湖泊浮游动物分析

利用环境DNA 监测并量化水体中生物多样性是近年水生生态学中关键的技术进步之一,该技术不仅提供快速准确的群落鉴定结果和物种多样性信息,还可以用于物种的相对丰度评估。浮游动物在水生食物链中起着能量和物质传递的作用,且能快速及时反映生态环境状况。基于八里湖、赛城湖浮游动物的eDNA 和形态学鉴定方法,对浮游动物种类组成、生物多样性、相对丰度和群落结构特征等进行探究分析。结果表明：eDNA 鉴定方法能比形态学鉴别出更多的类群,其具备鉴定深度更高的优势,但也存在误检假阳性风险;在生物多样性的表征上,两种方法结果存在部分显著差异。     

Interference in determination of rubidium and cesium in fish and zooplankton by graphite furnace atomic absorption spectrometry

Interference in the determination of rubidium and cesium in fish and Zooplankton was examined by graphite furnace atomic absorption spectrometry using synthetic matrices of these organisms at known concentrations and dilutions. Absorbance signals were depressed at dilution factors of less than 100, which confirms that the method is not free of interference for determination of rubidium and cesium in fish and Zooplankton.     

Convergence of trophic state and the lower food web in Lakes Huron,Michigan and Superior

Signs of increasing oligotrophication have been apparent in the open waters of both Lake Huron and Lake Michigan in recent years. Spring total phosphorus (TP) and the relative percentage of particulate phosphorus have declined in both lakes; spring TP concentrations in Lake Huron are now slightly lower than those in Lake Superior, while those in Lake Michigan are higher by only about 1 μg P/L. Furthermore, spring soluble silica concentrations have increased significantly in both lakes, consistent with decreases in productivity. Transparencies in Lakes Huron and Michigan have increased, and in most regions are currently roughly equivalent to those seen in Lake Superior. Seasonality of chlorophyll, as estimated by SeaWiFS satellite imagery, has been dramatically reduced in Lake Huron and Lake Michigan, with the spring bloom largely absent from both lakes and instead a seasonal maximum occurring in autumn, as is the case in Lake Superior. As of 2006, the loss of cladocerans and the increased importance of calanoids, in particular Limnocalanus, have resulted in crustacean zooplankton communities in Lake Huron and Lake Michigan closely resembling that in Lake Superior in size and structure. Decreases in Diporeia in offshore waters have resulted in abundances of non-dreissenid benthos communities in these lakes that approach those of Lake Superior. These changes have resulted in a distinct convergence of the trophic state and lower food web in the three lakes, with Lake Huron more oligotrophic than Lake Superior by some measures.     

Impact of industrial discharges on the zooplankton community in the Messaieed industrial area,Qatar (Persian Gulf)

Zooplankton samples were collected from the Messaieed Marine Area that is subject to industrial and sewage discharge, thermal pollution, as well as oil loading and unloading activities. Copepods formed 74% of the zooplankton community followed by bivalves (7.6%) and Gastropod veligers (5.5%), Ostracods (4.7%) and Cladocera (3.4%). Industrial discharge not only impacted the total number of zooplankton but also species diversity. Diversity indices were higher for inner coastal waters. Pollution levels more than reduction in food source impacted the distribution of main zooplankton groups. The pollution stress changed the structure of zooplankton community rather than impacting the total population. Copepods showed resistance to oil pollution but were reduced in numbers at areas affected by oxygen demanding wastes. Polychaete larvae and Chaetognatha withstand elevated temperature, ammonia and pH levels.     

Short‐term effects of planktonic rotifers and cladocerans on phytoplankton of the River Nile

The responses of River Nile phytoplankton to different zooplankton communities have been analyzed. Different communities have been made up of natural Nile water of rotifers and small cladocerans, rotifers after exclusion of macrozooplankton by size fraction and large cladocerans plus small cladocerans and rotifers. A set of experiments in enclosures were designed to determine the short‐term effects produced by these zooplankton assemblages on phytoplankton structure. The phytoplankton community are made up of Bacillariophyceae, Cyanophyceae and Chlorophyceae, as the main algal groups. It seems that, grazing does not play a leading role in controlling phytoplankton production and its standing stock in the River Nile.     

Differences between Arctic and Atlantic fjord systems on bioaccumulation of persistent organic pollutants in zooplankton from Svalbard

Differences in bioaccumulation of persistent organic pollutants (POPs) between fjords characterized by different water masses were investigated by comparing POP concentrations, patterns and bioaccumulation factors (BAFs) in seven species of zooplankton from Liefdefjorden (Arctic water mass) and Kongsfjorden (Atlantic water mass), Svalbard, Norway. No difference in concentrations and patterns of POPs was observed in seawater and POM; however higher concentrations and BAFs for certain POPs were found in species of zooplankton from Kongsfjorden. The same species were sampled in both fjords and the differences in concentrations of POPs and BAFs were most likely due to fjord specific characteristics, such as ice cover and timing of snow/glacier melt. These confounding factors make it difficult to conclude on water mass (Arctic vs. Atlantic) specific differences and further to extrapolate these results to possible climate change effects on accumulation of POPs in zooplankton. The present study suggests that zooplankton do biomagnify POPs, which is important for understanding contaminant uptake and flux in zooplankton, though consciousness regarding the method of evaluation is important.