Benthic algal populations respond to aluminum,acid, and aluminum-acid mixtures in artificial streams

Elevated aluminum (Al) concentrations are often associated with acid-stressed aquatic ecosystems, so it has been unclear whether acidic water or elevated Al is more responsible in changing community composition. Experiments were done to investigate effects of acidification and increased Al on the abundance of benthic algae in artificial streams supplied with natural water and nominal treatments of (a) pH 4.8, (b) 500 µg l^-1 Al, or (c) the mixture of pH 4.8 and 500 µg l^-1 Al compared to a control without added Al or acid. These treatments are referred to as Acid, Al-only, Acid + Al, and the control, respectively. In the Acid treatment the abundance of two diatoms, two green algae, dry weight biomass, and chlorophyll a decreased; one diatom and one filamentous blue-green alga increased. In the Al-only treatment, densities of two diatoms, one green alga, one blue-green alga, dry weight biomass, and chlorophyll a increased. In the Acid + Al treatment, abundances of one green alga, two blue-green algae, and concentrations of chlorophyll a decreased below the levels observed in the Acid treatment. Acid and Al concentrations were altered by each other and by chemical and biological processes in the stream system. Species of diatoms, green algae, and blue-green algae responded individually to treatments and mixtures of acid and Al. Shifts in the abundance of species may change food web relationships for higher-level consumers, and algae may be useful biomonitors of ecological stress.     

Facile synthesis of 2′-substituted lactoses

Isopropylidenation of lactose with 2,2-dimethoxypropane in the presence ofp-toluenesulfonic acid gave two products, which were identified by¹H- and¹³C-NMR as 2,35,63,4-tri-O-isopropylidenelactose dimethyl acetal (1) and its 6-O-(2-methoxy)-isopropyl derivative (2). These products were used for the synthesis of 2-O-methyllactose (7), 2,6-di-O-methyllactose (9) and 2-O-benzyllactose (13).     

Anaerobic biosynthesis of unsaturated fatty acids in the cyanobacterium,Oscillatoria limnetica

The mechanism for synthesis of monounsaturated fatty acids under aerobic and anaerobic conditions was studied in the facultative anaerobic cyanobacterium, Oscillatoria limnetica. The hexadecenoic acid (C161) of aerobically grown O. limnetica was shown to contain both the 7 (79%) and 9 (21%) isomers, while the octadecenoic (C181) acid was entirely the 9 acid. Incorporation of [2-¹⁴C] acetate into the fatty acids under aerobic conditions resulted in synthesis of the 7 and 9 C161 and the 9 C181. Synthesis of unsaturated fatty acids in the presence of DCMU required sulfide. Anaerobic incubations in the presence of DCMU and sulfide (less than 0.003% atmospheric oxygen) resulted in a two-fold increase in monounsaturated fatty acids of both 7 and 9 C161 and 9 and 11 C181. The synthesis of these isomers is characteristic of a bacterialtype, anaerobic pathway.Abbreviations DCMU 3(3,4-dichlorophenyl)-1,1-dimethylurea - MFA monounsaturated fatty acid     

Water uptake and transport in lianas and co-occurring trees of a seasonally dry tropical forest

Water uptake and transport were studied in eight liana species in a seasonally dry tropical forest on Barro Colorado Island, Panama. Stable hydrogen isotope composition (D) of xylem and soil water, soil volumetric water content (_v), and basal sap flow were measured during the 1997 and 1998 dry seasons. Sap flow of several neighboring trees was measured to assess differences between lianas and trees in magnitudes and patterns of daily sap flow. Little seasonal change in _v was observed at 90–120 cm depth in both years. Mean soil water D during the dry season was –19 at 0–30 cm, –34 at 30–60 cm, and –50 at 90–120 cm. Average values of xylem D among the liana species ranged from –28 to –44 during the middle of the dry season, suggesting that water uptake was restricted to intermediate soil layers (30–60 cm). By the end of the dry season, all species exhibited more negative xylem D values (–41 to –62), suggesting that they shifted to deeper water sources. Maximum sap flux density in co-occurring lianas and trees were comparable at similar stem diameter (DBH). Furthermore, lianas and trees conformed to the same linear relationship between daily sap flow and DBH. Our observations that lianas tap shallow sources of soil water at the beginning of the dry season and that sap flow is similar in lianas and trees of equivalent stem diameter do not support the common assumptions that lianas rely primarily on deep soil water and that they have higher rates of sap flow than co-occurring trees of similar stem size.     

Food web structure in the high Arctic Canada Basin: evidence from δ13C and δ15N analysis

The food-web structure of the Arctic deep Canada Basin was investigated in summer 2002 using carbon and nitrogen stable isotope tracers. Overall food-web length of the range of organisms sampled occupied four trophic levels, based on 3.8 trophic level enrichment (¹⁵N range: 5.3–17.7). It was, thus, 0.5–1 trophic levels longer than food webs in both Arctic shelf and temperate deep-sea systems. The food sources, pelagic particulate organic matter (POM) (¹³C=–25.8, ¹⁵N=5.3) and ice POM (¹³C=–26.9, ¹⁵N=4.1), were not significantly different. Organisms of all habitats, ice-associated, pelagic and benthic, covered a large range of ¹⁵N values. In general, ice-associated crustaceans (¹⁵N range 4.6–12.4, mean 6.9) and pelagic species (¹⁵N range 5.9–16.5, mean 11.5) were depleted relative to benthic invertebrates (¹⁵N range 4.6–17.7, mean 13.2). The predominantly herbivorous and predatory sympagic and pelagic species constitute a shorter food chain that is based on fresh material produced in the water column. Many benthic invertebrates were deposit feeders, relying on largely refractory material. However, sufficient fresh phytodetritus appeared to arrive at the seafloor to support some benthic suspension and surface deposit feeders on a low trophic level (e.g., crinoids, cumaceans). The enriched signatures of benthic deposit feeders and predators may be a consequence of low primary production in the high Arctic and the subsequent high degree of reworking of organic material.     

Sensitivity of Bloom's syndrome lymphocytes to ethyl methanesulfonate

Summary Ethyl methanesulfonate induced several times as many sister chromatid exchanges (SCEs) in lymphocytes from individuals affected with Bloom's syndrome as in lymphocytes from controls or heterozygotes. In cultures of cells from an individual with Bloom's syndrome who had two populations of lymphocytes circulating in his blood—low cells having normal spontaneous frequencies of SCEs and high cells having elevated frequencies—only the high cells showed the increased sensitivity to ethyl methanesulfonate.To whom offprint requests should be sent     

Habitat heterogeneity and niche structure of trees in two tropical rain forests

Dispersal-assembly theories of species coexistence posit that environmental factors play no role in explaining community diversity and structure. Dispersal-assembly theories shed light on some aspects of community structure such as species-area and species-abundance relationships. However, species environmental associations also affect these measures of community structure. Measurements of species niche breadth and overlap address this influence. Using a new continuous measure of niche and a dispersal-assembly null model that maintains species niche breadth and aggregation, we tested two hypotheses assessing the effects of habitat heterogeneity on the ability of dispersal-assembly theories to explain community niche structure. We found that in both homogenous and heterogeneous environments dispersal-assembly theories cannot fully explain observed niche structure. The performance of the dispersal-assembly null models was particularly poor in heterogeneous environments. These results indicate that non-dispersal based mechanisms are in part responsible for observed community structure and measures of community structure which include species environmental associations should be used to test theories of species diversity.     

Cellular redox state and activating protein-1 are involved in ascorbate effect on calcitriol-induced differentiation

Summary Ascorbate has been related to the differentiation of several mesenchymal cells including haematopoietic cells. We have previously demonstrated that ascorbate enhances the activity of 1,25-dihydroxyvitamin D₃ (1,25(OH)₂D₃) on monocytic differentiation of HL-60 cells. Here, we show that ascorbate-mediated modification of cellular redox state and AP-1 (activating protein-1) DNA binding during early phases are related to the enhancing effect of ascorbate on differentiation. Ascorbate, but not its fully oxidized form, dehydroascorbate, or an ascorbate analogue with a low rate of oxidation, ascorbate-2-phosphate, enhanced the differentiation induced by 1,25(OH)₂D₃, modified cytosolic reactive oxygen species levels and mitochondrial redox potential (_m), and modulated AP-1 DNA binding in HL-60 cells. Ascorbate itself increased AP-1 binding to DNA in noninduced cells, whereas it inhibited AP-1 binding in 1,25(OH)₂D₃-induced cells. However, ascorbate increased the mRNA levels ofc-jun, junB. andc-fos in 1,25(OH)₂D₃-induced cells. Taken together, these results suggest that the enhancing effect of ascorbate on HL-60 differentiation induced by 1,25(OH)₂D₃ is related to its effect on the cellular redox state and the modulation of AP-1 activity.Abbreviations 1,25-(OH)₂D₃ 1,25-dihydroxyvitamin D₃ - _m mitochondrial transmembrane potential - AP-1 activating protein-1 - Asc-2-P ascorbate-2-phosphate - DHA dehydroascorbate - DiOC₆(3) 3,3-dihexyloxacarboxyanine iodide - EMSA electromobility shift assay - NBT nitroblue tetrazolium - ROS reactive oxygen species     

The listing and de-listing of invertebrate species for conservation in Australia

Formal listing of species for protection is a responsible action in conferring conservation priority, and must be undertaken as objectively as possible, and redundant entries that distract from priority need be removed. Diverse groups, such as invertebrates, pose problems for listing because criteria of rarity and threat are often confounded. Species de-listed as a result of recovery action are a special category, in which conservation investment has been made; the principle of recognising these as rehabilitated species with a formal duty of aftercare is discussed. Although the paper focuses on invertebrates in Australia, the principles have wider relevance in species-level conservation focus.     

Effects of an exotic bivalve mollusc on benthic invertebrates and food quality in the Ohio River

Effects of zebra mussels (Dreissena polymorpha) on populations of amphipods (Gammarus fasciatus) and prosobranch snails (Lithasia obovata) and on nutritional quality of benthic organic matter were examined in 20 artificial streams receiving Ohio River water and containing either mussels or small gravel. Twenty individually-marked snails were placed in each trough, and streams were allowed to colonize with other benthic species for 28 days.Dreissenids positively affected other benthic invertebrates in our stream channels. Compared to gravel channels, Gammarus biomass was significantly higher (P<0.01) in mussel channels, amphipod densities increased 300%, and snail growth rates were 50% greater. Food quality of fine benthic organic matter (FBOM) was greater in mussel channels (i.e. lower C:N), and FBOM was carbon depleted (lower ¹³C) but nitrogen enriched (higher ¹⁵N). Isotope data suggest that detrital FBOM was not the sole food source for snails and amphipods in our channels and that they were assimilating a higher quality portion of this BOM. The overall influence of dreissenids on particular benthic invertebrates may depend on the response and/or susceptibility of those species to biofouling, increased habitat heterogeneity, and changes in the quality and quantity of nutrients.     

Interrelation between plankton and benthos in the littoral algal community of Lake Yunoko,Central Japan

To ascertain the floristic interaction between phytoplankton and benthos in the littoral, the composition of each community was investigated and the effect of the substrata on the benthic communities was also examined.The main component of the benthic algal population wasFragilaria pinnata followed byF. pinnata var.lancettula. Although the dominant species of the plankton in the upper layers were similar to those in the limnetic, and those immediately above the bottom contained species of benthic origin, the similarity index of C implied high similarity between these two plankton layers. This index was developed by Morishita (1959) to measure the degree of overlap of component species between two communities. The value of C distributes from 0 to 1. The closer the value approaches 1, the more the communities are similar.For the dominant species, a significant difference was observed between the phytoplankton and benthic communities and in addition, C values indicated low overall similarity in the composition of the communities. These results suggest that there is little interrelation between phytoplankton and benthos even in the shallow littoral zone.     

A non-specific Ca2+ (or Mg2+)-stimulated ATPase in rat heart sarcoplasmic reticulum

ATPase activity in rat heart sarcoplasmic reticulum was stimulated in a concentration-dependent manner by both Ca²⁺ and Mg²⁺ in the complete absence of the other cation. Increasing concentrations of Mg²⁺ produced an apparent inhibition of the Ca²⁺-dependent ATP hydrolysis. CDTA (trans-1,2-diaminocyclohexane-N,N,N,N-tetraacetate) had no effect on these responses. The results indicate the presence of a low affinity non-specific divalent cation-stimulated ATPase in rat heart sarcoplasmic reticulum. However, sarcoplasmic reticulum vesicles transported Ca²⁺ with a high affinity (K_0.5 Ca²⁺ = 0.41 M) suggesting the presence of a high affinity Ca²⁺-transporting ATPase. Calmodulin did not stimulate rat heart sarcoplasmic reticulum ATPase activity over a range of Ca²⁺ and Mg²⁺ concentrations and failed to stimulate membrane phosphorylation and Ca²⁺ transport into sarcoplasmic reticulum vesicles. Calmodulin antagonists trifluoperazine and compound 48180 did not affect the ATPase activity. Catalytic subunit of cAMP-dependent protein kinase was also ineffective in stimulating the ATPase activity. These results suggest the presence of an ATPase activity in rat heart sarcoplasmic reticulum with different properties from the high affinity Ca²⁺-pumping ATPase previously characterized in dog heart and other species.Abbreviations cAMP adenosine 3,5-monophosphate - CaM calmodulin - CDTA trans-1,2-diaminocyclohexane-N,N,N,N-tetraacetate - EDTA ethylene-diaminetetraacetate - EGTA ethylene glycol bis(-aminoethyl ether)-N,N,N,N-tetraacetate - PLB phospholamban - SR sarcoplasmic reticulum - TFP trifluoperazine     

Analysis of primary food sources and trophic relationships of aquatic animals in a mangrove-fringed estuary,Khung Krabaen Bay (Thailand) using dual stable isotope techniques

Stable carbon (¹³C) and nitrogen (¹⁵N) isotopes were used to elucidate primary food sources and trophic relationships of organisms in Khung Krabaen Bay and adjacent offshore waters. The three separate sampling sites were mangroves, inner bay and offshore. The ¹³C values of mangrove leaves were –28.2 to –29.4, seagrass –10.5, macroalgae –14.9 to –18.2, plankton –20.0 to –21.8, benthic detritus –15.1 to –26.3, invertebrates –16.5 to –26.0, and fishes –13.4 to –26.3. The ¹⁵N values of mangrove leaves were 4.3 to 5.7, seagrass 4.3, macroalgae 2.2 to 4.4, plankton 5.7 to 6.4 , benthic detritus 5.1 to 5.3, invertebrates 7.2 to 12.2 , and fishes 6.3 to 15.9. The primary producers had distinct ¹³C values. The ¹³C values of animals collected from mangroves were more negative than those of animals collected far from shore. The primary carbon sources that support food webs clearly depended on location. The contribution of mangroves to food webs was confined only to mangroves, but a mixture of macroalgae and plankton was a major carbon source for organisms in the inner bay area. Offshore organisms clearly derived their carbon through the planktonic food web. The ¹⁵N values of consumers were enriched by 3–4 relative to their diets. The ¹⁵N data suggests that some of aquatic animals had capacity to change their feeding habits according to places and availability of foods and as a result, individuals of the same species could be assigned to different trophic levels at different places.     

Time scales of change in the San Francisco Bay benthos

Results from multi-year investigations in the San Francisco Bay estuary show that large abundance fluctuations within benthic macroinvertebrate populations reflect both (1) within-year periodicity of reproduction, recruitment, and mortality that is not necessarily coincident with seasonal changes of the environment (e.g., the annual temperature cycle), and (2) aperiodic density changes (often larger than within-year fluctuations) following random perturbations of the environment.Density peaks of the small, short-lived estuarine invertebrates that comprise the vast majority of individuals in the bay's relatively homogeneous benthic community normally occur between spring and autumn depending on the species, in large part a reflection of reproductive periodicity. However, because mild winters permit reproductive activity in some of the common species throughout much of the year, other factors are important to within-year density fluctuations in the community. Seasonally predictable changes in freshwater inflow, wind and tidal mixing, microalgal biomass, and sediment erosion/deposition patterns all contribute to observed seasonal changes in abundance. For example, the commonly observed decline in abundance during winter reflects both short-lived species that die after reproducing and the stress of winter conditions (e.g., inundation by less saline, sediment-laden water and the decline in both planktonic and benthic algal biomass — a direct source of food for the shallow-water benthos). On the other hand, data from several studies suggest that observed recruitment and mortality may in fact be the migration of juveniles and adults to and from study sites. For example, the common amphipod Ampelisca abdita apparently moves from shallow to deep water, or from up-estuary to down-estuary locations, coincident with periods of high river runoff in winter. Growth of individuals within the few studied species populations is also highly seasonal, and appears to be coincident with seasonal increases in the abundance of planktonic and/or benthic microalgae.Two multi-year studies have shown that, in addition to within-year periodicity, major restructuring of the benthic community can occur as a result of anomalous (usually climate-related) perturbations of the benthic habitat. For example, during wet years freshwater-intolerant species disappear from the upper part of the estuary and from shallow areas of the bay. During a two-year drought these same species colonized the extreme upper end of the estuary in large numbers. Other aperiodic perturbations include localized instances of sediment erosion or deposition and algal mat accumulations that greatly depress abundance. Additionally, there is evidence (observations that the clam Macoma balthica establishes large populations only when the amphipod A. abdita is not abundant) that species interactions can contribute greatly to interannual variations. Thus, while community composition may change little over the long term, year-to-year predictability of species abundances is low.     

The effects of mitochondrial energetics inhibitors on the fluorescence of potential-sensitive dyes rhodamine 123 and DiS-C3-(5) in lymphocyte suspensions

The effects of uncouplers (FCCP, DNF), oligomycin, and rotenone on the fluorescence of potential-sensitive dyes, rhodamine 123 and diS-C₃-(5), in lymphocyte suspensions were compared. The fluorescence of these optical probes gradually increased at higher FCCP concentrations. The dependences of fluorescence intensities and FCCP concentrations were similar for both dyes, and only diS-C₃-(5) fluorescence started increasing at lower FCCP concentrations. Rotenone (1 µM) significantly increased rhodamine 123 fluorescence. TMPD-induced and uncoupler-induced diS-C₃-(5) fluorescence changes increased 1.5- to 2-fold if the incubation mixture was supplemented with oligomycin (0.1–0.2 µg/ml). The fluorescence responses of the dyes in the lymphocyte suspension correlate with the effects of mitochondrial energetics inhibitors on _m in isolated mitochondria. The results suggest the possibility of using these dyes for estimating the direction of the _m changes in the lymphocyte suspension.Abbreviations _m difference in electrical potential across the mitochondrial inner membrane - _p difference in electrical potentials across the plasma membrane - TMPD N,N,N,N-tetramethyl-p-phenylenediamine - DNP 2,4-dinitrophenol - FCCP carbonyl cyanidep-trifluoromethoxyphenylhydrazone - diS-C₃-(5) 3,3-dipropylthiodicarbocyanine - MOPS morpholinopropane sulfonic acid     

Freshwater protozoa: biodiversity and ecological function

The purpose of this article is to pull together various elements from current knowledge regarding the natural history of free-living protozoa in fresh waters. We define their functional role, set the likely limits of biodiversity, and explore how the two may be related. Protozoa are unicellular, phagotrophic organisms, and 16 phyla of protists contain free-living freshwater protozoan species. They are the most important grazers of microbes in aquatic environments and the only grazers of any importance in anoxic habitats. In sediments, ciliates are usually the dominant protozoans. Benthic ciliate biomass accounts for slightly less than 10% of total benthic invertebrate biomass, but ciliate production may equal or even exceed invertebrate production. Freshwater protozoan species are probably ubiquitous, although many may persist locally for long periods in a cryptic state – as potential rather than active biodiversity. As protozoa are among the largest and most complex of micro-organisms, it follows that bacteria and all other smaller, more numerous microbes are also ubiquitous. The number of protozoan species recorded in local surveys (232) is about 10% of the estimated global species richness (2390). The 'seedbank of protozoan (and microbial) species ensures that local microbial diversity is never so impoverished that it cannot play its full part in ecosystem functions such as carbon fixation and nutrient cycling.     

Alignment of BrdU-substituted chromatids in satellite association in human metaphase cells

We have studied the orientation of BrdU-substituted chromatids in satellite associations in cells double-stained to reveal both the Ag/As nucleolar organizer regions and, simultaneously, sister chromatid differentiation. In those satellite associations with all four chromatids joined by Ag stain, and with the axes in a virtually straight line, we have observed an excess of concordant configurations. Where an association was considered single, dark chromatids were involved in significantly more associations than light chromatids. Within this group, the observed excess of concordant associations was not greatly different from the numbers observed in the straight, double-chromatid group of configurations. Whether the increased involvement of dark chromatids in satellite associations provides a complete explanation for the observed excess of concordant associations, or whether certain individuals show a specific tendency to form concordant associations, must await further data.     

Molecular identification of powdery mildew resistance genes in common wheat (Triticum aestivum L.)

RFLP markers for the wheat powdery mildew resistance genes Pm1 and Pm2 were tagged by means of near-isogenic lines. The probe Whs178 is located 3 cM from the Pm1 gene. For the powdery mildew resistance gene Pm2, two markers were identified. The linkage between the Pm2 resistance locus and one of these two probes was estimated to be 3 cM with a F₂ population. Both markers can be used to detect the presence of the corresponding resistance gene in commercial cultivars. Bulked segregant analysis was applied to identify linkage disequillibrium between the resistance gene Pm18 and the abovementioned marker, which was linked to this locus at a distance of 4 cM. Furthermore, the RAPD marker OPH-11₁₉₀₀ (5-CTTCCGCAGT-3) was selected with pools created from a population segregating for the resistance of Trigo BR 34. The RAPD marker was mapped about 13 cM from this resistance locus.     

An integrated approach to hydropower impact assessment

The submerged aquatic vegetation of 17 Norwegian lakes is described and related to the environmental impacts that result from hydro-electric power (HEP) use of these lakes. Largely based upon physiognomical features, three main community types are discerned. These are denoted as (a) shallow-water, (b) mid-depth, and (c) deep-water community, respectively. The aquatic macrophytes are classified into a plant strategy framework. This classification suggests that these macrophytes frequently exhibit combined traits of the S (stress-tolerating), R (ruderal), and C (competitive) strategies. A plant-strategy index for the lakes is derived from the species classification and related to their HEP use.Broadly, the response features of hydrolake vegetation are: (1) a decline in species richness; (2) the gradual disappearance of the shallow-water and mid-depth communities; (3) a conspicuous absence of vascular submerged macrophytes in storage hydrolakes when lake levels change more than 7 m annually, and; (4) an increased incidence of species possessing plant strategies of the ruderal (R) type. The implications of these results for an environmental impact assessment of hydropower schemes are discussed.     

Population dynamics and the color of environmental noise: A study on a three-species food chain system

In the present study, the effect of red, white and blue environmental noise on population dynamics in a simple three-species food chain system was analyzed. The colored noise was superimposed on the three-species food chain model first put forth by Rosenzweig in different ways and the resulting power spectra were investigated. We showed that the amplitude of environmental noise, the trophic level at which a population is positioned and whether a population is directly affected by environmental noise, are all important with respect to the way in which a population responds to noise with different colors. For the deterministic case, all population dynamics are red irrespective of the system dynamics. When all species are sensitive to environmental noise, the top predators dynamics always remain red regardless of the color of the noise and its amplitude, whereas the dynamics of the intermediate species turn blue under disturbances of any color with high amplitude, and those of the basal species may become blue only under blue noise. If only one species is sensitive to environmental noise, the dynamics of the insensitive species are always red, irrespective of the color of the noise and its amplitude. Unlike previous results obtained by studying single-species models, our results have almost nothing to do with deterministic system dynamics. In other words, changing the deterministic system dynamics from stable via periodic to chaotic does not qualitatively change the outcome. Our results are of importance in determining how we interpret the ubiquitous red power spectrum of natural ecological time series.