Evaluation and further development of the activated sludge respiration inhibition test

The activated sludge respiration inhibition test is an important bacterial test system for the determination of bacterial toxicity of chemical compounds. The exposure period recommended by OECD 209 and ISO 8192 protocols is 30 and 180 min. A modified version of the test was developed which allowed a prolonged incubation period of 27 h to enhance the possibilities of the test system. The test system with the prolonged incubation time was evaluated by the recommended reference compound 3.5-dichlorophenol and showed an EC50 of 6.3 mgl(-1) with a coefficient of variation of 12.7%. Furthermore, the use of an open test system was evaluated showing a comparable toxicity but a higher coefficient of variation than the closed test system. A storage of activated sludge for several days accompanied by a daily feed with OECD nutrient solution should be avoided, for it can cause a decreased sensitivity of the inoculum. Different statistical fit procedures were tested indicating that Weibull fit procedures were superior for extended data sets covering a wide range of concentrations whereas Gamma and Probit fits were appropriate for smaller data sets mainly restricted to the linear part of the dose response curve.     

Olive mill solid residues as heavy metal sorbent material: a preliminary study

Biosorption of heavy metals is an innovative and alternative technology to remove these pollutants from aqueous solutions using inactive and dead biomasses such as agricultural and industrial wastes, algae and bacteria. In this study olive mill solid residue was used as heavy metal adsorbent material for its wide availability as agricultural waste and also for its cellulosic matrix, rich of potential metal binding active sites. Preliminary studies concerned with the removal of different heavy metals (Hg, Pb, Cu, Zn and Cd), the effect of pre-treatments by water and n-hexane and the regeneration possibility. Olive mill solid residue resulted able to remove heavy metals from aqueous solutions with an affinity series reflecting the hydrolytic properties of the metallic ions, but also a particular affinity for copper. It can be supposed that biosorption phenomenon occur by a general ion exchange mechanism combined with a specific complexation reaction for copper ions. Water pre-treatment is sufficient to reduce COD release in the effluent according to the law limit, while n-hexane pre-treatment strongly reduces also the adsorption properties of this material. Experimental isotherms obtained under different operating conditions were fitted using a non linear regression method for the estimation of the Langmuir parameters. Moreover a simple Scatchard plot analysis was performed for a preliminary investigation of the active sites, showing the presence of two different site affinities depending on the metal concentration, according to the previous hypothesis of two kinds of uptake mechanisms for copper biosorption. Regeneration tests gave good results in terms of yield of regeneration and also concentration ratios.     

Meiofauna densities and gastrotrich community composition in a Mediterranean sea cave

During the past 5 decades, the large-sized biota inhabiting dark marine caves has attracted the attention of many marine biologists; in contrast, studies concerning the meiofaunal organisms of these peculiar biotopes remain scanty and mostly with a taxonomic aim. In this study, the nature and abundance of meiofaunal taxa living in a Mediterranean, semi-submerged sea cave was surveyed in relation to distance from the entrance and over two different seasonal periods. Particular attention was paid to the Gastrotricha taxocene. Research was carried out in a cave along the Ionian coast of Apulia (southern Italy), the “Grotta Piccola del Ciolo” which opens for approximately 120 m on the north-eastern side of a shallow fjord and has a bottom blanketed by fine to very fine sand, occasionally rich in detritus. Quantitative samples in four replicates were collected by SCUBA diving, in November 2000 and June 2001, coring the sediment with a hand-held piston corer in three light-free sites (stations 1–3) located at increasing distances from the entrance. At each site, two additional 500-ml sediment samples were collected for an in vivo study of the Gastrotricha. Faunistic analysis found a fairly high meiobenthic diversity, identifying representatives of more than 12 major groups, with total abundances ranging from 656 ind./10 cm² (10 cm²) in November to 1,069 ind./10 cm² in June. Station 1, the closest to the entrance invariably hosted the most abundant meiofaunal community (851 ind./10 cm² in November and 1932 ind./10 cm² in June), followed by station 2 or 3 depending on the season. While nematodes and harpacticoids appear as the most abundant taxa when the cave is considered as a whole, other taxa may prevail numerically in selected stations, e.g. priapulids, which are the second most abundant taxon at station 1 (30 ind./10 cm² in November and 83 ind./10 cm² in June). Although the density of total meiofauna and that of the single groups may not be very high, the cave is interesting by virtue of the peculiarity of the hosted fauna, e.g., species and genera new to science or new to the Mediterranean Sea. Regarding the Gastrotricha, we found 16 species, accounting for 1.3–2.6% of the total meiobenthos (density = 8.4 ind./10 cm² in November and 27.4 ind./10 cm² in June). Analysis of the gastrotrich community found, particularly in June, an assemblage of taxa quite different from those found in open habitats, even at the family level; differences that are probably due to the exploitation of different food resources by animals populating the two environments, i.e. algae in the open sea versus bacteria in the caves. Results indicate that for meiofauna, as happens for macrofauna, the marine caves may represent hotspots of biodiversity and endemism; the driving forces at the base of the trophic depletion hypothesis seem to be responsible for structuring the meiofauna community inside the cave.     

Fighting behavior in hermit crabs: the combined effect of resource-holding potential and resource value in Pagurus longicarpus

A study was conducted to determine whether asymmetries in both resource-holding potential (RHP) and resource value (RV) influence dominance and fighting behavior in the hermit crab Pagurus longicarpus. A total of 120 groups of three crabs were observed for 10 min in four experiments that tested all diverse combinations of equal/different RHP (i.e. ‘body size’) and equal/different RV (i.e. ‘shell size’ and ‘shell quality’). In a fifth experiment, dominant and subordinate individuals of the same size category (26 groups) were forced to enter shells of opposite quality than those previously occupied, and then the behavior of the reconstituted original groups was observed for additional 10 min. As expected, crabs in lower quality shells were more willing to initiate and to escalate fights. However, their attacks were directed to any crab of the group, independently of the defender's shell quality, and the fight duration did not vary with the different value of the resources at stake. This may indicate that P. longicarpus is unable to assess the quality of the shells available in its social environment but bases its tactical decisions during fights solely on its own resource. This suggestion was confirmed by the change in the fighting behavior of crabs whose shell quality was experimentally altered. This manipulation induced an overall increase in the intensity of aggression, drastic modification of crab behavior, and inversion of the hierarchy even though these crabs have had previous experiences of wins/losses and were familiar to the other members of the group. In this species, large crab size and/or the occupancy of adequate (and oversized) shells appeared to be the most likely determinant of contest resolution. Individuals seemed to retain a memory of the previously held resource and behaved accordingly.     

Nonylphenols in freshwaters of the hydrologic system of an Italian district: association with human activities and evaluation of human exposure

A sampling campaign for the determination of concentrations of nonylphenol isomers (NPs) in freshwaters and sediments of the hydrologic system of the Rieti district (central Italy) was conducted from 2002 to 2003. Eighteen sampling points, selected on the basis of the different human activities in the vicinity, were monitored; six series of water samples (from June 2002 to February 2003) and one of sediment samples (summer 2002) were analyzed by GC/MS.

There was a direct relationship between concentrations of NPs and the presence of urban or industrial activities near the sampling point. However, concentrations of NPs in water were in the range of <0.1–1.4 μg l⁻¹, and their presence limited to short distances from the sources of contamination. Accumulation factors in sediment samples ranged from 10² to 5 × 10³.     

mtDNA control region and D-HPLC analysis: a method to evaluate the mating system in Syngnathidae (Teleostei)

Mitochondrial DNA (mtDNA) has been used extensively in animals for phylogenetic and population studies but it has been applied only occasionally to mating systems analysis, where nuclear markers are usually preferred. We used denaturing-high performance liquid chromatography (D-HPLC) to detect mitochondrial DNA polymorphisms to assess the genetic mating system in Syngnathus abaster. Our study of ten pregnant males, revealed polygyny in 30% of the males, who carried embryos originating from multiple females. In addition, 30% of the pregnant males carried embryos with the same mitochondrial haplotype. This is not sufficient to demonstrate polyandry but allows a rapid selection and a reduced sample size for further studies. In conclusion, the proposed technique is time- and cost-effective, allows the certain identification of polygyny and provides useful information to study polyandry.     

Eutrophication and trophic structure in response to the presence of the eelgrass <Emphasis Type="Italic">Zostera noltii</Emphasis>

In estuaries, eelgrass meadows contribute to fundamental ecosystem functions of estuaries, providing food to several predators and buffering the negative effects of eutrophication. We asked whether the presence of the eelgrass Zostera noltii decreased the nitrogen concentration in the overlying water, affected the sources of nitrogen sequestrated by primary producers and changed the benthic and pelagic food web structures. We also studied the importance of these food webs in providing food to fish. We compared bare sediment to sediment covered by a Z. noltii meadow, and examined nutrient concentrations in the water column and δ¹⁵N in primary producers as indicators of anthropogenic inputs of nutrients. We then measured both δ¹³C and δ¹⁵N in the tissues of plants and consumers to establish food web structures. There were no differences in the concentrations and sources of nitrogen between sites. Rather, δ¹⁵N values indicated anthropogenic inputs of N (e.g. sewage discharges, agriculture) in both sites. There were no major differences in the structure of the planktonic food web, which was in part sustained by particulate organic matter and supported most predator fish, and in the structure of the benthic food web. Nonetheless, there were differences in the sources of food for omnivore consumers and for the detritivore Scrobicularia plana. Overall, the benthic food web did not use food derived from the eelgrass or macroalgae deposited on the substratum. Suspension feeders used particulate and sediment organic matter, whereas the δ¹³C and δ¹⁵N values of the other consumers indicated a likely contribution of benthic microalgae. Furthermore, in both habitats we found large variability in the isotope signatures of benthic macrofauna consumers, which did not allow distinguishing clearly different trophic groups and indicated a high level of omnivory and a mixed diet opportunistically making use of the availability of food in the surroundings.     

Populus alba dioctyl phthalate uptake from contaminated water

Environmental Science and Pollution Research - Phthalates are micro-pollutants of great concern due to their negative effects on ecosystem functioning and human health. Thanks to its capability in...