Age,growth and population structure of <Emphasis Type="Italic">Modiolus barbatus</Emphasis> from the Adriatic

Age, growth and population structure of Modiolus barbatus from Mali Ston Bay, Croatia were determined using modal size (age) classes in length frequency distributions, annual pallial line scars on the inner shell surface, internal annual growth lines in shell sections of the middle nacreous layer and Calcein marked and transplanted mussels. The length frequency distributions indicated that M. barbatus attain a length of ∼40 mm in 5–6 years indicating that a large proportion of the population in Mali Ston Bay is <5 years old. Some mussels of ∼60 mm were predicted to be 14 years old using the Von Bertalanffy growth (VBG) equation. Up to the first 6 pallial line scars were visible in young (<6 years) mussels but in older shells the first scars became obscured by nacre deposition as the mussel increased in length and age. The age of the older shells (>6 years) was determined from the middle nacreous lines in shell section, which formed annually in winter between February and March; the wider dark increments forming during summer (June to September). The oldest mussel, determined from the middle nacreous lines, was >12 years, with the majority of mussels aged between 3 and 6 years of age. The ages of mussels ascertained using the growth lines were not dissimilar to the ages predicted from the length frequency distributions. Age at length curves produced using modal size class data were not different from the data obtained using the pallial scar rings and internal growth lines. Taken together these data suggest that M. barbatus attains a length of 40 and 50 mm within 5 and 8 years, respectively. Eighty one percent of individual M. barbatus injected with a Calcein seawater solution (300 mg Calcein l⁻¹), into their mantle cavity successfully deposited a fluorescent line, which was visible in suitably prepared shell sections under ultra violet light. Incorporation of Calcein into the mussel shells was seasonally variable with the lowest frequency of incorporation in mussels marked in February and recovered in May. Seasonal shell growth was observed with significantly higher growth rates in mussels marked in May and removed in August (ANCOVA, F _3,149 = 23.11, P < 0.001). Mussels (∼18 to 22 mm) marked in May and recovered in August displayed maximal growth rates of >2.5 mm month⁻¹ compared with a mean mussel growth rate of 1.2 ± 0.6 mm month⁻¹. At other times of the year mussel shell growth ranged from immeasurable to 1.48 mm month⁻¹.     

Some biophysical parameters of the skin of the electric fishTorpedo marmorata

The transverse electrical resistance and DC potentials of the electric fishTorpedo marmorata have been measured. The resistance is lower in the skin covering the electric organ than in skin taken from other parts of the body. The external skin surface is electropositive relative to the internal one. On the basis of the results obtained it is probable that electrical discharges are channelled from the body through low resistant pathways; the skin covering the electric organ does not seem to play any specific role in ionic transport occurring in connection with, or as a consequence of, electrical discharges of the fish.     

Interaction between Fe-cyanide complex and humic acids

The fate of cyanides in soil is strongly influenced by the formation of Fe cyanides, which can interact with organic and inorganic colloids and precipitate as stable compounds. Scarce information is available on the capacity of humic acids to interact with cyano-complexes and thus affect the leaching and prevent the risk of contamination of watertable. Here we show that interaction between humic acids (HAs) and ferricyanide complex led to a formation of ferricyanide-humo micelles, and that the interaction did not imply changes in the original structure of ferricyanide complex.     

What drives visitors to tourist sites to choose “green” accommodation facilities?

Environment, Development and Sustainability - Our aim is to determine the factors influencing a visitor’s decision to stay in a green accommodation facility. Visitors from six tourist sites...     

An approach to cleaner production: from hair burning to hair saving using a lime-free unhairing system

One of the methods to decrease the pollution of tanneries' wastewater is hair saving unhairing of hides. An investigation of proteolytic activity of enzymatic preparation (EP) has shown that some EPs have high stability in strong alkaline solutions and can be used for the hair saving process.Based on this investigation, a new hair saving unhairing method using a system containing EP, sodium hydroxide, sodium sulphide, and disodium hydrophosphate was developed. The method results in a high quality pelt suitable for leather manufacturing, decreases the pollution caused by sodium sulphide and the other products of hair degradation and avoids the pollution caused by calcium compounds.     

Chromium in soil layers and plants on closed landfill site after landfill leachate application

Landfill leachate (LL) usually contains low concentrations of heavy metals due to the anaerobic conditions in the methanogenic landfill body after degradation of easily degradable organic matter and the neutral pH of LL, which prevents mobilization and leaching of metals. Low average concentrations of metals were also confirmed in our extensive study on the rehabilitation of an old landfill site with vegetative landfill cover and LL recirculation after its treatment in constructed wetland. The only exception was chromium (Cr). Its concentrations in LL ranged between 0.10 and 2.75 mg/L, and were higher than the concentrations usually found in the literature. The objectives of the study were: (1) to understand why Cr is high in LL and (2) to understand the fate and transport of Cr in soil and vegetation of landfill cover due to known Cr toxicity to plants. The total concentration of Cr in LL, total and exchangeable concentrations of Cr in landfill soil cover and Cr content in the plant material were extensively monitored from May 2004 to September 2006. By obtained data on Cr concentration in different landfill constituents, supported with the data on the amount of loaded leachate, amount of precipitation and potential evapotranspiration (ETP) during the performance of the research, a detailed picture of time distribution and co-dependency of Cr is provided in this research. A highly positive correlation was found between concentrations of Cr and dissolved organic carbon (r = 0.875) in LL, which indicates the co-transport of Cr and dissolved organic carbon through the system. Monitoring results showed that the substrate used in the experiment did not contribute to Cr accumulation in the landfill soil cover, resulting in percolation of a high proportion of Cr back into the waste layers and its circulation in the system. No negative effects on plant growth appeared during the monitoring period. Due to low uptake of Cr by plants (0.10–0.15 mg/kg in leaves and 0.05–0.07 mg/kg in stems of Salix purpurea), the estimated Cr offtake from LL by plants represented only a small proportion of the LL Cr mass load during the observation period, resulting in no dispersion of Cr into the environment through leaf drop.     

Influence of parasitism on the use of small terrestrial rodents in environmental pollution monitoring

Bioaccumulation of cadmium, chromium, copper, manganese, nickel, lead and zinc in small terrestrial rodents – voles and their cestode parasite Paranoplocephala dentata was studied. Contents of Pb, Mn, Ni and Zn in the parasite were found to be higher than in the kidney and liver of the parasitized animals. Lead level in the cestode was 37 fold higher than in the liver of the infected rodents. Bioaccumulation factors of zinc, nickel and manganese in the cestode are mostly in the range from 2 to 4.5. Considering the different contents of manganese and zinc in livers of non-parasitized and parasitized rodents, kidney tissue was found to be more reliable than liver as an indicator of environmental pollution by manganese and zinc; the kidneys of parasitized animals showed no significant change in the concentrations of those elements that are accumulated in the cestode.