Comparison of episodic acidification in Canada, Europe and the United States

Episodic acidification is practically a ubiquitous process in streams and drainage lakes in Canada, Europe and the United States. Depressions of pH are often smaller in systems with low pre-episode pH levels. Studies on European surface waters have reported episodes most frequently with minimum pH levels below 4.5. In Canada and the United States, studies have also reported a number of systems that have had minimum pH levels below 4.5. In all areas, change in water flowpath during hydrological events is a major determinant of episode characteristics. Episodic acidification is also controlled by a combination of other natural and anthropogenic factors. Base cation decreases are an important contributor to episodes in circumneutral streams and lakes. Sulphate pulses are generally important contributors to episodic acidification in Europe and Canada. Nitrate pulses are generally more important to episodic acidification in the Northeast United States. Increases in organic acids contribute to episodes in some streams in all areas. The sea-salt effect is important in near-coastal streams and lakes. In Canada, Europe and the United States, acidic deposition has increased the severity (minimum pH reached) of episodes in some streams and lakes.     

Identifying the land use and land cover change drivers: methods and case studies of two forest reserves in Northern Benin

Environment, Development and Sustainability - Land use and land cover change (LULCC) is one of the problems that the world has been facing for the last few decades despite political attention....     

Ecosystem engineering by leaf-rolling mites enhances arthropod diversity

Bombardier beetles (Coleoptera, Carabidae, Brachininae) possess a remarkable defense mechanism where a hot chemical spray is released from the tip of their abdomen, with an audible explosive sound. To date, the repellent properties of these chemicals have been tested against a limited number of taxa, such as amphibians and insects. To investigate the impact of bombardier beetle defenses on avian predators, feeding trials were conducted using the bombardier beetle (Pheropsophus jessoensis) and the Japanese quail (Coturnix japonica), a sympatric and generalist predator. All naïve, hand-reared quail attacked live beetles, indicating the absence of an innate aversion to them. However, most of the quail rejected consuming the beetles whether or not the beetles sprayed them with chemicals. Naïve quail also rejected dead P. jessoensis individuals. These results support the recent hypothesis that it is not essential for P. jessoensis to spray noxious chemicals to deter predators. We also found that some of the quail exposed to live P. jessoensis remembered to avoid them for up to 5 weeks. Our results provide the first evidence of the repelling effects of bombardier beetle defense mechanisms on avian predators.

     

Incorporation and utilization of bacterial lipids in theSolemya velum symbiosis

We undertook a detailed analysis of the lipid composition ofSolemya velum (Say), a bivalve containing endosymbiotic chemoautotrophic bacteria, in order to determine the presence of lipid biomarkers of endosymbiont activity. The symbiont-free clamMya arenaria (L.) and the sulfur-oxidizing bacteriumThiomicrospira crunogena (Jannasch et al.) were analyzed for comparative purposes. The ¹³C ratios of the fatty acids and sterols were also measured to elucidate potential carbon sources for the lipids of each bivalve species. Both fatty acid and sterol composition differed markedly between the two bivalves. The lipids ofS. velum were characterized by large amounts of 18: 17 (cis-vaccenic acid), 16:0, and 16 : 17 fatty acids, and low concentrations of the highly unsaturated plant-derived fatty acids characteristic of most marine bivalves. Cholest-5-en-3-ol (cholesterol) accounted for greater than 95% of the sterols inS. velum. In contrast,M. arenaria had fatty acid and sterol compositions similar to typical marine bivalves and was characterized by large amounts of the highly unsaturated fatty acids 20 : 53 and 22 : 63 and a variety of plant-derived sterols. The fatty acids ofT. crunogena were similar to those ofS. velum and were dominated by 18:17, 16:0 and 16:17 fatty acids. Thecis-vaccenic acid found inS. velum is almost certainly symbiontderived and serves as a potential biomarker for symbiontlipid incorporation by the host. The high concentrations ofcis-vaccenic acid (up to 35% of the total fatty acid content) in both symbiont-containing and symbiont-free tissues ofS. velum demonstrate the importance of the endosymbionts in the lipid metabolism of this bivalve. The presence ofcis-vaccenic acid in all the major lipid classes ofS. velum demonstrates both incorporation and utilization of this compound. The ¹³C ratios of the fatty acids and sterols ofS. velum were significantly lighter (–38.4 to –45.3) than those ofM. arenaria (–23.8 to – 24.2) and were similar to the values found for the fatty acids ofT. crunogena (–45); this suggests that the lipids ofS. velum are either derived directly from the endosymbionts or are synthesized using endosymbiontderived carbon.Woods Hole Oceanographic Institution Contribution No. 7356Please address all correspondence and reprint requests to Dr Conway at her present address: Department of Biological Sciences, University of Pittsburgh, Pennsylvania 15260, USA     

Utilization of a fumigated sediment by two benthic deposit-feeders:Abra alba (Mollusca: Bivalvia) andEupolymnia nebulosa (Annelida: Polychaeta)

The present study tested the utilization of dead microbial biomass by two benthic deposit-feeders:Abra alba (Wood) (Mollusca: Bivalvia) andEupolymnia nebulosa (Montagu) (Annelida: Polychaeta). Clams were collected in the Canet lagoon during spring 1989. Worms were collected in the Port-Vendres harbour during spring 1989. The¹⁴C-labelled (glutamic acid, 24 h) sediment used during the study was sterilized with 1% chloroform, washed with sterile seawater, and dried (60°C; 48 h). This sterilisation procedure, called fumigation is the least harmful to the sediment (Novitsky 1986). Both clams and worms were incubated in the presence of the fumigated sediment for 5, 10, 20, and 50 h. At the end of each experiment we recorded the radioactivity in four compartments: (1) sediment, (2) dissolved organic matter (DOM), (3) CO₂, and (4) animals. The radioactivity of the sediment was subdivided into five fractions: (i) soluble in 2N HCl, (ii) soluble in hot 5% trichloroacetic acid (TCA), (iii) soluble in 1N NaOH, (iv) soluble in hot 6N HCl, (v) residual (after combustion in a Leco carbon analyser). In the first set of experiments, after 20 h of incubation, 5.4 and 4.7% of the total radioactivity was taken up by clams and worms, respectively. However, a model revealed that this uptake could have been correlated with the release of radiolabelled DOM (33% of total radioactivity during the first 5 h). In order to test this assumption, we used the same protocol with three additional washes of the fumigated sediment. This resulted in a significantly lower uptake by the clams (1.9% of the total radioactivity byt = 50 h), whereas the worms exhibited an uptake similar to that in the initial experiment (5.1% of total radioactivity byt = 50 h). These results underline the importance of considering interactions with DOM when applying radiotracer techniques to the study of benthic food chains. The average ingestion rates of fumigated sediment byA. alba andE. nebulosa were 5.2 10^–2 mg sediment dry wt mg^–1 clam h^–1 and 3.5 10^–2 mg sediment dry wt mg^–1 worm h^–1, respectively, which is comparable to previous data reported for other deposit-feeding bivalves and polychaetes feeding on natural sediment or detritus. The low radioactivity recorded for CO₂ together with the similarity of the changes in the partitioning of the radioactivity within the sediment between control experiments and experiments carried out in the presence of clams or worms suggest low assimilation efficiencies. Therefore, the present study supports the fact that dead microbial biomass does not constitute an important food source for benthic deposit-feeders.     

Yield and grain quality of spring wheat (Triticum aestivum L., cv. Drabant) exposed to different concentrations of ozone in open-top chambers

Spring wheat (Triticum aestivum L., cv. Drabant) was exposed to different concentrations of ozone in open-top chambers for two growing seasons, 1987 and 1988, at a site located in south-west Sweden. The chambers were placed in a field of commercially grown spring wheat. The treatments were charcoal-filtered air (CF), non-filtered air (NF) and non-filtered air plus extra ozone (NF(+)). In 1988, one additional ozone concentration (NF(++)) was used. Grain yield was affected by the ozone concentration of the air. Air filtration resulted in an increase in grain yield of about 7% in both years, compared to NF. The addition of ozone (NF(+), NF(++)) reduced grain yield and increased the content of crude protein of the grain in both years. Filtration of the air had no significant effect on the content of crude protein, compared to NF. The results showed a strong positive chamber effect on grain yield in the cold and wet summer of 1987. In 1988, there was no net chamber effect on grain yield. The relative differences between the CF, NF and NF(+) treatments with respect to grain yield were of the same magnitude in the two years, despite the very different weather conditions.     

Studies on the effects of some organic pollutants on the heavy metal transport in an Indian soil

The translocation of some heavy metals, such as Hg, Cd, Cu, Co, Ni and Zn, as affected by organic pollutants, i.e. methanol, ethanol, propanol, formaldehyde, acetaldehyde, benzaldehyde, acetone, ethyl methyl ketone and cyclo-hexanone, was studied in an Indian red soil using soil thin layer chromatography. It was observed that an increase in the concentration of organic compounds in developer enhances the heavy metal mobility, except in the case of Cu and Hg which show a decreasing trend. The results are discussed in relation to the physico-chemical characteristics of the soil and adsorption/desorption phenomena.     

Digestive mechanics and gluttonous feeding in the feather starOligometra serripinna (Echinodermata: Crinoidea)

The movement and digestion of food in the gut ofOligometra serripinna (Carpenter) were studied at Lizard Island (14°3842S; 145°2710E) in the austral winter of 1986. Feather stars in the laboratory were fed a brief, small meal of brine shrimp nauplii and killed at increasing time intervals thereafter. Histological reconstructions showed that the ingested nauplii progressed along the digestive tract surprisingly quickly. Some nauplii were found in the mid and hind intestine in only 30 min, and all of the nauplii had reached the hind intestine and rectum in 1 h. Digestion of the nauplii had started at 1 h, and only a few fragments of naupliar exoskeleton remained in the hind intestine and rectum 5 h after the start of feeding. Videotape analysis showed that no fecal pellets were released during this experiment. In the natural environment ofO. serripinna, ingested particles may similarly be transported quickly to the hind part of the gut and digested there — when feather stars were fixed in the field, most of the gut contents were found in the hind intestine and rectum.O. serripinna, which efficiently rejects inert particles before they are ingested, usually defecates infrequently (probably not more than once over a span of many hours) and differs from some other feather stars that ingest numerous inert particles and defecate much more frequently. When specimens ofO. serripinna were fed continuously on brine shrimp nauplii,Artemia sp. (San Francisco strain), in the laboratory, the feather stars fed gluttonously, packing their guts with several hundred nauplii in 1 to 2 h. Thereafter, superfluous feeding began (i.e., further ingestions appeared to force undigested nauplii, some of them still living, out of the anus). These observations suggest thatO. serripinna usually feeds at relatively modest rates in its natural habitat, but can feed gluttonously to take advantage of infrequent patches of highly concentrated, nutritious particles (e.g. copepod swarms, migrating demersal zooplankton, and invertebrate gametes from mass spawnings). It is likely that such patches of nutritious particles are usually small enough to drift out of reach of the feather stars before gluttonous feeding proceeds to superfluous feeding. Opportunities for superfluous feeding in nature are probably very infrequent (e.g. ingestion of coral gametes and embryos after a mass spawning), and the feather stars evidently have no behavior that stops further ingestions after the gut becomes filled to capacity.     

The effect of chronic toxicity of copper on the activity of Balbiani rings and nucleolar organizing region in the salivary gland chromosomes of Chironomus ninevah larvae

The effect of copper on the activity of Balbiani rings (BR1 and BR2) and nucleolar organizing region (NOR) in chromosome IV of the salivary gland of the 4th instar larvae of Chironomus ninevah has been investigated. Sublethal concentrations, i.e. 0.02, 0.1, 0.15 and 0.2 mg litre(-1) suppress the activity of BR1, and are statistically significant. The same concentrations reduced the activity of BR2 and NOR, but without significant differences, except 0.1 mg litre(-1) which was significant. The purpose of this work was to evaluate the effect of chronic toxicity of Cu(2+) on the expression of gene activity of midge salivary gland chromosomes Although there may be many more aquatic organisms that are more sensitive to copper, this midge was selected as a biological indicator species because of its association with benthic sediments.