Temporal scales and patterns of invertebrate biodiversity dynamics in boreal lakes recovering from acidification

Despite international policy implementation to reduce atmospheric acid deposition and restore natural resources from cultural acidification, evidence of ecological recovery is equivocal. Failure to meet recovery goals means that acidification still threatens biodiversity in many areas of the world. Managers thus need information to manage biodiversity, especially its components that are sensitive to stress (acid-sensitive taxa). We analyzed 20-year time series (1988-2007) of water quality and littoral invertebrates in acidified and circum-neutral lakes across Sweden to evaluate regional biodiversity dynamics and the extent to which changes in water quality affect these dynamics. We used multivariate time series modeling to (1) test how individual species groups within invertebrate communities track changes in the abiotic environment and (2) reveal congruencies of taxon contributions to species group change across lakes. Chemical recovery in the lakes was equivocal, and increases of pH and alkalinity were observed in subsets of acidified and circum-neutral lakes. Time series analyses revealed two different patterns of species groups for invertebrate communities across lakes; the first species group showed monotonic change over time, while the second group showed fluctuating temporal patterns. These independent species groups correlated distinctly with different sets of environmental variables. Recovery of pH and alkalinity status was associated with species group patterns only in a few lakes, highlighting an overall weak recovery of invertebrate species. The sets of species, including acid-sensitive taxa, composing these species groups differed markedly across lakes, highlighting context-specific responses of invertebrates to environmental variation. These results are encouraging because disparate local-scale dynamics maintain the diversity of sensitive invertebrate species on a regional scale, despite persisting acidification problems. Our study can inform and help refine current acidification-related policy focused on sensitive biodiversity elements.     

Seasonal variation in lipid class and fatty acid composition of two small copepods in Balsfjorden,northern Norway

Zooplankton were collected at Svartnes, northern Norway between 1985 and 1986. The lipid class and fatty acid composition of a subarctic population ofPseudocalanus acuspes (Giesbrecht, 1881) andAcartia longiremis Lilljeborg are described for four seasons of the year. The results are discussed in relation to the seasonal variation in abundance and dry weight of the predominant developmental stages. The lipid composition of these small copepod species resembles that of omnivorous or carnivorous species.P. acuspes andA. longiremis overwinter in a state of arrested development, but seem to feed actively throughout the year. This behaviour resembles that of the omnivoreMetridia longa (Lubbock), but is in contrast to that of the herbivoreCalanus finmarchicus (Gunnerus) from the same area, which spends the winter in diapause.     

Size-related trophodynamic changes in three target fish species recovering from intensive trawling

The consequences for food-web structure of protecting marine communities from trawling have been little explored. We investigated the Gulf of Castellammare, northwest Sicily, where a trawl ban initiated in 1989 has led to great increases in the biomass of some target species. Using stable isotopes of carbon and nitrogen, our objectives were to see if mean trophic level and omnivory had increased after the ban in three of the most common fishery-target species, namely, the anglerfish Lophius budegassa, Mediterranean hake Merluccius merluccius, and red mullet Mullus barbatus. We compared size data from before and after the fishery closure, but we also compared recently derived data from outside and inside the closed area. In all three species '¹³C and '¹⁵N were found to differ markedly depending on fish size. '¹³C was found to decrease in L. budegassa and Merluccius merluccius but increase in Mullus barbatus with increasing fish length. '¹⁵N increased in all three species, and this was thought to reflect feeding at increasingly higher trophic levels during the animals' lives. Mean length, and therefore '¹⁵N-derived trophic level, increased after the trawl ban only in the anglerfish L. budegassa. Based on '¹³C and '¹⁵N data, none of the species became more or less omnivorous after the ban. After 9 years of no trawling, increases in numerical abundance were not accompanied by substantial size-related trophodynamic shifts in any of the three species of fish studied.     

Spatial variability in lipid composition of calanoid copepods from Fram Strait,the Arctic

The calanoid copepods Calanus hyperboreus and C. finmarchicus were investigated in view of their lipid and wax ester content and their fatty acid and alcohol composition. Analyses were performed in females and copepodid stages V and IV from the Fram Strait region between Greenland and Spitsbergen in 1984. This region offers different food conditions like diatom blooms in the North East Water Polynya, food shortage in areas with very close ice cover, high phytoplankton biomass in the marginal ice zone and lower biomass in the open Atlantic water. Lipids contained generally more than 70% wax esters. Highest levels were found in C. hyperboreus with more than 90%. This percentage was not very variable, in spite of large differences in dry weight and lipid content. Copepods with particularly high weight and lipid content were found in the North East Water Polynya. The lightest individuals were found under the pack ice. Lipid proportions per unit dry weight were higher in C. hyperboreus than in C. finmarchicus, whose lowest values were found in the open Atlantic water. Spatial variability in fatty acid composition was much higher than in alcohol composition. The principle alcohols, 20:1 and 22:1, generally accounting for more than 80% of total alcohols. In the North East Water Polynya, the predominant monounsaturated fatty acid was 16:1, while under the ice 20:1 and 22:1 dominated. In the marginal ice zone and in the open water, the 18:4 acid reached percentages up to 30% of total fatty acids. These changes were related to the different food conditions. C. hyperboreus appears to be best adapted to the cold water and unfavourable conditions of polar regions because of its high lipid and wax ester store with long-chain wax esters of high calorific value.     

Distribution and mortality of diapause eggs from calanoid copepods in relation to sedimentation regimes

Distribution, abundance and age of diapause eggs from three species of calanoid copepods (in particular from Acartia spp. most likely Acartia tonsa, and Centropages hamatus and less numerous from Temora longicornis) were recorded in sediment profiles by enumerating hatched nauplii from incubated sediment samples. Phytoplankton pigments and ²¹⁰Pb and ¹³⁷Cs analyses indicated that the sedimentation regimes were different between two southern and two northern stations of the island Funen, Denmark. Significant variations in vertical distribution, abundance and mortality of diapause eggs were found between the stations. Dating of the sediment cores suggested a ~70-year maximum age of viable eggs on the northernmost stations, and ~28 year at the southernmost stations. The eggs exhibited a significantly higher mortality rate at the southernmost stations compared with the northernmost, 0.35–0.53 year⁻¹ vs. 0.07–0.08 year⁻¹ with no systematic pattern among species. The differences in abundance, mortality and age of the diapause eggs are suggested to be due to the sediment characteristics in which they are buried.     

Biosynthesis of trimethylamine oxide in calanoid copepods. seasonal changes in trimethylamine monooxygenase activity

Live copepods, Calanus finmarchicus (Gunnerus) and C. hyperboreus (Krøyer), exposed to dissolved ¹⁴C-labeled trimethylamine (TMA) in seawater, oxidized TMA to trimethylamine oxide (TMAO), which accumulated in the organisms. The amount of TMAO synthesized was dependent on the time of exposure to TMA and the concentration of TMA in the seawater. It was inferred that copepods can produce TMAO by oxidation of TMA found in their plant food. Choline and methionine did not appear to be of importance as precursors of TMAO. There were large seasonal changes in TMA monooxygenase activity of both copepods. The activity was high in spring, and decreased through summer and autumn to a winter low in October to March. The changes in TMAO content of C. finmarchicus were, in comparison, small (this aspect was not tested for C. hyperboreus).     

Phytoplankton pigments in the gut concents of planktonic copepods from coastal waters off southern California

Phytoplankton xanthophylls in the gut contents of the copepods Calanus pacificus, Corycaeus anglicus, and Paracalanus parvus, collected from 5 stations off San Onofre, California, in June 1982, were measured by reverse phase, high-performance liquid chromatography (HPLC). The dinoflagellate pigment, peridinin, was usually the most abundant xanthophyll in the guts of all three species of copepods. Evidently, feeding was principally on dinoflagellates (which dominated the phytoplankton biomass). The level of feeding activity, rather than the class of phytoplankton ingested, seemed to differentiate the behaviors of the copepods. Xanthophyll content per unit copepod wet weight was higher in Corycaeus anglicus and Paracalanus parvus than in Calanus pacificus. Chlorophyll a fluorescence of the copepod gut contents was measured in conjunction with the analysis of gut xanthophylls. The xanthophyll content of the gut varied directly with the concentration of chlorophyll a in the gut. Xanthophyll content was not related to the concentration of pheopigments in the gut. Apparently, the xanthophylls that were detected were due to the presence of recently ingested phytoplankton biomass.     

Growth,condition and specific dynamic action in the mussel Mytilus edulis recovering from starvation

Juvenile Mytilus edulis were grown individually in plastic racks in a tidal salt marsh for 72 d in 1984, starved in the laboratory for 130 d, and then fed the alga Isochrysis galbana daily for 64 d. Oxygen consumption was measured at various times during the course of starvation and recovery. The effects of both size (tissue dry weight) and condition (tissue size relative to shell size) on the rate of oxygen consumption during the course of starvation and recovery were analyzed by multiple regression. Weight-specific preprandial rate was inversely correlated with both size and condition. Weight-specific active rate (measured shortly after feeding) was correlated with size but not condition. Relative Scope for Activity was inversely correlated with size and positively correlated with condition. Relative Specific Dynamic Action (RSDA; the integrated physiological and mechanical response to a meal) was initially correlated negatively with size and subsequently positively with condition. Glycogen content was shown to be positively correlated with condition in mussels before starvation and during recovery. During recovery, experimental mussels returned to 90% of their estimated dry weight prior to starvation, and from 53% after starvation. At weekly intervals during recovery, oxygen consumption was measured following a meal until it returned to the preprandial rate. Both pre- and postprandial volumes (l at STP) of oxygen consumed per hour ( O _2pre and O _2post , respectively) increased significantly during recovery. The postprandial rise in oxygen consumption increased significantly from 15% to 23% of O _2pre . At the end of the recovery period, RSDA [( O _2post – O _2pre )/ O _2pre ] was independent of final dry weight, but was significantly correlated with percent dry weight recovered (r ²=0.44; df=10; P<0.02). The increase in RSDA may reflect increased utilization of food and its conversion to soma during recovery from starvation, as distinct from mechanical energy expenditure (feeding activity) following a meal.     

Levels of selected heavy metals in commercial fish from five freshwater lakes,Pakistan

The levels of As, Cd, Cr, Cu, Fe, Mn, Ni, Pb, Zn and Hg are estimated by atomic absorption in the muscle of six commercial species of fish belonging to five freshwater lakes of Pakistan. The species included Mastacembelus armatus, Tor putitura, Mystus seenghala, Wallago attu, Catla catla and Labeo rohita. The fish were procured in comparable weight ranges so that a viable comparison of trace metal content could be effected. As, Fe, Pb, Zn and Hg showed elevated levels of 0.006–6.967, 0.933–6.133, 0.060–4.108, 0.978–5.363 and 0.030–3.211 μg/g, wet weight. The relevant statistical parameters, such as standard deviation, standard error, skewness and its t‐value are also reported for establishing the randomness of the distribution in relation to the corresponding data of freshwater lakes of the world and examined in view of species‐specificity and origin.     

Grazing rates of the copepods Calanus glacialis and C. finmarchicus in arctic waters of the Barents Sea

Natural feeding rates of Copepodite Stages IV and V, and adult female Calanus glacialis (Jaschnov) and Copepodite Stage V and adult female C. finmarchicus (Gunnerus) were estimated using fluorescence analysis of gut contents. Measurements were made on copepods sampled from arctic waters east of Svalbard (Barents Sea) during the spring phytoplankton increase, in the period from 27 May to 13 June, 1983. Observations on Copepodite Stages IV and V and adult female C. glacialis suggest that the gastric evacuation rate is independent of developmental stage, whereas C. finmarchicus Copepodite Stage V showed a lower gastric evacuation rate than adult females. Gut fullness displayed a low correlation with the ambient chlorophyll concentrations. Ingestion rates calculated for C. glacialis were 0.3, 2.3, and 11.0 g C h^-1 for Copepodite Stages IV and V and adult females, respectively. Copepodite Stage V and adult female C. finmarchicus ingested 0.9 and 1.1 g C h^-1 at a temperature of ca.-1.0°C. The maximum ingestion rate in terms of percent body carbon d^-1 was higher for adult female C. glacialis and C. finmarchicus than for the respective Copepodite Stage V's. The results are discussed both in relation to the physiological state of the species and to the environmental conditions.     

Zooplankton of the Bristol Channel and Severn Estuary. The distribution of four copepods in relation to salinity

The seasonal variations in distribution and abundance of the common zooplankton species in the Bristol Channel and Severn Estuary were related to the salinity regimes observed over the period November 1973 to February 1975. The dominant constituents in all regions were the calanoid copepods, which reached maximum densities in July: approximately 100 times their winter levels. Four zooplankton assemblages were recognised using an objective classification program which computed similarity coefficients and used group-average sorting. The assemblages existed along the salinity gradient observed from the Severn Estuary to the Celtic Sea. The assemblages were classified as true estuarine, estuarine and marine, euryhaline marine and stenohaline marine and were characterized by the copepods Eurytemora affinis (Poppe) (<30S), Acartia bifilosa var. inermis (rose) (27 to 33.5S), Centropages hamatus (Lilljeborg) (31 to 35S) and Calanus helgolandicus (Claus) (>33S), respectively.     

Population dynamics and production of the planktonic copepods in a eutrophic inlet of the Inland Sea of Japan. III.Paracalanus sp.

Population dynamics and production of the calanoid copepodParacalanus sp. were studied from November 1986 to November 1987 in Fukuyama Harbor, a eutrophic inlet of the Inland Sea of Japan. This species was perennial, with a large abundance peak in June/July and small peaks in September/October and November/December. During a year of investigation, 15 generations Gould be detected. For each generation, the mean population egg production rate and the mean daily midstage abundance front NIII to CV were determined to obtain a survival curve from egg to CV. The mortality was extremely high during the early life stages: on average only 7.1% of the eggs produced might survive into NIII. This high mortality might be caused by predation by sympatric omnivorous copepods, in addition to sinking loss of eggs from the waten column. The biomass ofParacalanus sp. showed marked seasonal variations largely in parallel with numerical abundance. The instantaneous growth rate of each developmental stage increased exponentially with temperature up to 20 °C, above which the rate was constant. The annual integrated production rate was 734 mg C m^–3 yr^–1 or 5.5 g C m^–2 yr^–1.     

酸雨胁迫下黑壳楠Lindera megaphylla Hemsl.幼苗在夏季和秋季的生理生态特性

浙江为酸雨危害严重地区之一,而植物在酸雨胁迫下的生长和生理变化情况可以衡量其对酸雨的耐受能力,亦可作为植被引种、经营和管理的参考依据.采用盆栽法,研究了在不同季节不同强度酸雨胁迫下黑壳楠Lindera megaphylla Hemsl.的生理生态特性,设置了3个酸雨处理:重度酸雨处理(pH2.5)、中度酸雨处理(pH4.0)和酸雨对照处理(pH5.6).研究结果表明:①酸雨、季节以及酸雨和季节的交互效应对黑壳楠的株高、地径和叶绿素相对含量没有显著影响.②黑壳楠的最大净光合速率(Amax)、表观量子效率(AQE)、光补偿点(LCP)和暗呼吸速率(Rd)对酸雨胁迫敏感,而季节并未显著影响到植物的光合特性.③酸雨胁迫显著影响黑壳楠的气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE).季节对黑壳楠的蒸腾速率(Tr)和水分利用效率(WUE)影响显著.酸雨和季节的交互效应极显著影响到植物的胞间CO2(Ci)浓度和蒸腾速率(Tr).研究表明夏季黑石楠受酸雨胁迫的影响比秋季严重.重度酸雨胁迫严重影响到黑壳楠的生理生长,在酸雨危害严重地区如浙江不适宜大量种植黑壳楠.     

Conservation implications of physiological carry‐over effects in bats recovering from white‐nose syndrome

Although it is well documented that infectious diseases can pose threats to biodiversity, the potential long‐term consequences of pathogen exposure on individual fitness and its effects on population viability have rarely been studied. We tested the hypothesis that pathogen exposure causes physiological carry‐over effects with a pathogen that is uniquely suited to this question because the infection period is specific and time limited. The fungus Pseudogymnoascus destructans causes white‐nose syndrome (WNS) in hibernating bats, which either die due to the infection while hibernating or recover following emergence from hibernation. The fungus infects all exposed individuals in an overwintering site simultaneously, and bats that survive infection during hibernation clear the pathogen within a few weeks following emergence. We quantified chronic stress during the active season, when bats are not infected, by measuring cortisol in bat claws. Free‐ranging Myotis lucifugus who survived previous exposure to P. destructans had significantly higher levels of claw cortisol than naïve individuals. Thus, cryptic physiological carry‐over effects of pathogen exposure may persist in asymptomatic, recovered individuals. If these effects result in reduced survival or reproductive success, they could also affect population viability and even act as a third stream in the extinction vortex. For example, significant increases in chronic stress, such as those indicated here, are correlated with reduced reproductive success in a number of species. Future research should directly explore the link between pathogen exposure and the viability of apparently recovered populations to improve understanding of the true impacts of infectious diseases on threatened populations.     

S–O–C isotopic picture of sulphate–methane–carbonate system in freshwater lakes from Poland. A review

Microbial oxidation of organic compounds (including methane), in freshwater sediments, may result in precipitation of carbonates, which may become an important geochemical archive of paleoenvironmental variations. Most probably low δ¹³C value in calcite in eutrophic systems results from an advanced oxidation of organic compounds in turbulent or/and sulphate-rich conditions. Likewise, high δ¹³C value in calcite from organic-rich sediments may evidence low redox potential of the freshwater system. Oxidation of methane and organic matter results in significant isotope effects in sulphates dissolved in water. Therefore, to better understand the origin of carbon isotope signal in carbonates, concentration and stable isotope measurements in dissolved sulphate (water column), bubble methane and calcite (freshwater sediments) have been carried out in 24 lakes, 2 ponds and 4 rivers in Poland. The highest concentration of sulphate has been detected in rivers (85.47 SO₄ ²⁻ mg/l) and an artificial lake (70.30 SO₄ ²⁻ mg/l) located in the extremely SO₄ ²⁻-polluted region called the “Black Triangle”. The lowest concentration of sulphate is found in dystrophic and mountain lakes (from 0.5 SO₄ ²⁻ to about 3 mg/l). The lowest δ³⁴S(SO₄ ²⁻) and δ¹⁸O(SO₄ ²⁻) values occur in unpolluted lakes in eastern Poland (−0.94 and 1.38‰, respectively). The highest S and O isotopic ratios are found in a polluted lake in western Poland (δ¹⁴S(SO₄ ²)=12.95‰) and in a dystrophic lake in eastern Poland (δ¹⁸O(SO₄ ²) = 16.15‰) respectively. It is proposed that δ³⁴SO₄ ²⁻ and (¹⁸O(SO₄ ²⁻) values in lakes represent a good tool to assess and quantify anthropogenic impact by acid precipitation and to monitor variations in the trophic state and redox processes controlled by biodegradation of organic compounds in sediments and water column. In general, increasing depth (up to 12 m) of the water column is associated with decreasing trend the δ¹³C(CH₄) value from about –35 to about –78‰. However, δ¹³C value in sedimentary calcite (δ¹³C vary from –10 to 0.5‰) shows opposite trends as compared to the corresponding methane. This is probably due to redox processes and distribution of heavy isotopes between methane and calcite. Likewise, turbulent water (river) show high δ¹³C value in methane and low δ¹³C value in calcite—this is probably due to an enhanced oxidation of methane producing ¹³C-depleted CO₂. In contrast to clean lakes, it is observed that an increase of the δ¹³C(CH₄) value occurs with increasing depth of the water column in a strongly SO₄ ²⁻-contaminated lake. This is probably due to a loss of biological buffering potential of the lake accompanied by an active oxidation of methane precursors.     

Ontogenetic and seasonal changes in lipid and fatty acid/alcohol compositions of the dominant Antarctic copepods Calanus propinquus,Calanoides acutus and Rhincalanus gigas

Lipid compositions of the dominant Antarctic copepods Calanoides acutus, Rhincalanus gigas and Calanus propinquus from the Weddell Sea have been investigated in great detail. Copepods were collected during summer in 1985 and late spring/early winter in 1986. The analyses revealed specific adaptations in the lipid biochemistry of these species which result in very different lipid components. The various copepodite stages of C. acutus synthesize wax esters with long-chain monounsaturated moieties and especially the alcohols consisted mainly of 20:1(n-9) and 22:1(n-11). R. gigas also generates wax esters, but with moieties of shorter chain length. The fatty alcohols consisted mainly of 14:0 and 16:0 components, while the major fatty acids were 20:5, 18:4 and 22:6, of which 18:4 probably originated from dietary input. In contrast, C. propinquus accumulates triacylglycerols, a very unusual depot lipid in polar calanoid copepods. Major fatty acids in C. propinquus were the long-chain monounsaturates 22:1(n-9) and 22:1(n-11), which may comprise up to 50% of total fatty acids. In C. acutus and C. propinquus there was a clear increase of long-chain fatty acids with increasing developmental stage. In contrast, the fatty acid and alcohol composition of the R. gigas copepodite stages were characterized by the dominance of the polyunsaturated fatty acids as well as high amounts of the monounsaturates 18:1(n-9) and 16:1(n-7). There was a considerable decrease of the dietary fatty acid 18:4(n-3) towards the older stages during summer; in late winter/early spring 18:4 was only detected in very low amounts. This tendency was also found in the other two species, but was less pronounced. In all three species dry weight and lipid content increased exponentially from younger to older stages. The highest portion of wax esters, or of triacylglycerols in C. propinquus, was found in the adults. Dry weight and lipid content were generally higher during summer. In late winter/early spring the variability was more pronounced and lipid-rich specimens showed a selective retention of long-chain monounsaturated fatty acids, whereas in lipid-poor specimens these fatty acids were very much depleted.     

Population dynamics and production of the planktonic copepods in a eutrophic inlet of the Inland Sea of Japan. I. Centropages abdominalis

Population dynamics and production of the calanoid copepod Centropages abdominalis were studied from November 1986 to November 1987 in Fukuyama Harbor, in the central part of the Inland Sea of Japan. This species was present in the plankton during a cold-water period from November to June (temperature range: 8.9 to 21.1 °C), with a peak abundance (23 600 ind m^–3) in February. During this period, six generations could be detected, and each generation time agreed well with that predicted from food-satiated laboratory experiments, indicating that the natural population was not food-limited. The population suffered extremely high mortality during the period from egg to naupliar stage (N) II: only 0.02 to 4% of the eggs survived to NII. However, the mortality in stages older than NII was almost negligible. The growth rate of C. abdominalis increased exponentially with increasing temperature. Its biomass and production rate showed marked seasonal variations largely in parallel with numerical abundance. The estimated production between 7 November 1986 and 29 May 1987 was 355 mg C m^–3 or 2.66 g C m^–2, 95% of which occurred during February and March. The daily production rate to biomass ratio increased exponentially with temperature from 0.18 at 8.9°C to 0.37 at 19°C.     

Population dynamics and production of the planktonic copepods in a eutrophic inlet of the Inland Sea of Japan. II. Acartia omorii

Population dynamics and production of the calanoid copepod Acartia omorii Bradford were studied from November 1986 to November 1987 in Fukuyama Harbor, a eutrophic inlet of the Inland Sea of Japan. This species was present in the plankton from October to July (temperature range: 8.9 to 24.3°C), with peaks in February-March and June. During this period, nine generations could be detected, for which the mean population egg production rate and midstage abundance of each life stage older than naupliar Stage (N) II were determined to trace survival. The population suffered extremely high mortality during the early life stages: on average only 2.5% of the eggs produced recruited into NII. This large loss is probably concentrated within the egg stage, due to predation, including cannibalism, by omnivorous copepods, in addition to sinking loss of eggs in the water column. However, the mortality from NII to copepodite Stage (C) V was negligible, indicating low predation pressure by large carnivores. The biomass of A. omorii showed marked seasonal variations in parallel with numerical abundance. The instantaneous growth rate of each stage increased exponentially with increasing temperature. The integrated production rate of A. omorii from 7 November 1986 to 21 July 1987 was 749 mg Cm^-3 or 5.62 g Cm^-2     

Differences in stress tolerance and brood size between a non-indigenous and an indigenous gammarid in the northern Baltic Sea

Differences in stress tolerance and reproductive traits may drive the competitive hierarchy between non-indigenous and indigenous species and turn the former ones into successful invaders. In the northern Baltic Sea, the non-indigenous Gammarus tigrinus is a recent invader of littoral ecosystems and now occupies comparable ecological niches as the indigenous G. zaddachi. In laboratory experiments on specimens collected between June and August 2009 around Tvärminne in southern Finland (59°50′N/23°15′E), the tolerances towards heat stress and hypoxia were determined for the two species using lethal time, LT₅₀, as response variable. The brood size of the two species was also studied and some observations were made on maturation of juveniles. Gammarus tigrinus was more resistant to hypoxia and survived at higher temperatures than G. zaddachi. Brood size was also greater in G. tigrinus than in G. zaddachi and G. tigrinus matured at a smaller size and earlier than G. zaddachi. Hence, there are clear competitive advantages for the non-indigenous G. tigrinus compared to the indigenous G. zaddachi, and these may be further strengthened through ongoing environmental changes related to increased eutrophication and a warming climate in the Baltic Sea region.     

Removal of C.I. acid brown 75 from aqueous solution by kaolinite

The adsorption of acid brown 75 onto kaolinite in aqueous solution was studied with respect to the pH, adsorbent dosage, contact time, initial concentration, and operating temperature. Desorption of dye from dye-saturated kaolinite was observed. Experimental data indicated that the adsorption capacity of kaolinite for the dye was higher in acidic rather than in basic solution. The maximum adsorption capacity of kaolinite towards the dye was found to be 96.5 mg g^?1 (pH 1.0). At the optimal adsorption condition, the dye removal ratio was 95.5%. Dye-saturated kaolinite could desorb at aqueous NaOH, the desorption ratio of dye was 78.8%. The linear Langmuir and Freundlich isotherm models are well fitting to represent the experimental data.