Distribution and morphological variation of low-shore algal turfs

The distribution of three functional groups of algae (filamentous, corticated terete and calcareous articulated) was investigated in low-shore, turf-forming assemblages from rocky shores in the western Mediterranean Sea (Italy). Algae were sampled along shores from three different stations. Shores were either exposed to wave action or sheltered and were characterised by various inclinations of the rocky substratum (horizontal, sloping and vertical). The hypotheses tested were: that the relative abundance of the three functional groups of algae (1) varies between sheltered and exposed shores, (2) is influenced by substratum inclination and (3) that these distributions are consistent across stations. There was no clear relationship between the morphology of turf-forming algae and shore characteristics. Covers of filamentous, corticated terete and calcareous articulated algae differed among shores and stations, but patterns were not consistent across shores with similar exposure to waves and substratum inclination. Turfs often comprised algae with different morphologies, in a combination of anchor and epiphytic species. It is suggested that functional groups of algae, as currently identified, are not effective in describing changes in distribution of algae between sheltered and exposed shores, when turf morphologies are considered. Future research on relationships between morphology and ecology of algae should consider the potential importance of positive interactions among associated species, which could override responses of individual functional groups.     

Toxic effect caused on microflora of soil by pesticide picloram application

The toxic effect of the herbicide picloram on the microbial population of a typical Brazilian red Latosol soil was studied in a series of microcalorimetric experiments. The activity of the soil was stimulated by the addition of 6.0 mg of glucose and 6.0 mg of ammonium sulfate, under 34.8% controlled moisture, to a 1.50 mg soil sample, at 298.15 +/- 0.02 K. The net thermal effect due to the addition of the picloram to the soil was determined by interpreting the power-time curves, which were recorded on the microcalorimeter. The total thermal effect evolved by the microorganisms was affected by the increasing doses of herbicide, and varied from 0 to 10.00 micrograms g-1. An increase in picloram exposure caused a decrease of the original thermal effect, reaching a null value above 20.89 micrograms of herbicide per gram of soil. The decreases of the thermal effect evolved by microorganisms and the increase of the lag phase period are associated with the death of the microbial population. The effects caused by picloram application in this typical Brazilian soil resulted in a strong effect on the soil microbial communities.     

New thiol adsorbent grafted on silica gel: synthesis,characterization and employment for heavy metal adsorptions

Silica gel surface has been modified in two reaction steps: (i) the silylating agent 3-mercaptopropyltrimetoxysilane was firstly immobilized to give a surface Sil-SH and (ii) this precursor incorporated an ethylene sulfide molecule to obtain the surface denoted Sil-SSH. This material was characterized by elemental analysis, IR spectroscopy, thermogravimetry, solid state 13C and 29Si NMR, and surface area measurement. These materials were employed as adsorbents for divalent heavy cations from aqueous solutions at room temperature and the isotherms were adjusted to a modified Langmuir equation. The maxima number of moles adsorbed were 1.0, 1.5, 1.6, 2.2, 2.4 and 3.3 mmol g(-1) for Co, Cu, Ni, Cd, Pb, and Hg, respectively.     

Positive effects of the introduced green alga, Codium fragile ssp. tomentosoides, on recruitment and survival of mussels

The green macroalga, Codium fragile ssp. tomentosoides, is an important component of sheltered low-shore assemblages on breakwaters along sandy shores in the northern Adriatic Sea. Macroscopic thalli of C. fragile are not perennial, but develop from propagules and/or undifferentiated forms in early spring, when the dominant native space-occupier, the mussel Mytilus galloprovincialis, recruits. By mid-summer, rapid growth of C. fragile leads to the formation of a dense canopy. We investigated the effects of juvenile and adult thalli of C. fragile on recruitment, survival and growth of mussels. Two experiments tested the hypotheses: (1) that recruitment of mussels is greater within patches of juvenile thalli (primordia) of C. fragile than on adjacent bare surfaces; (2) that the presence of a canopy of C. fragile affects the survival and growth of mussel recruits. The number of recruits of mussels was significantly larger within clumps of primordia of C. fragile than on bare surfaces. The removal of the canopy of C. fragile affected negatively the density of mussels after 2 months from the start of the experiment, but there were no effects on the mean size of individuals, nor on the size–frequency distribution. The same trend persisted after 4 months from the start of the experiment. These results show that re-colonisation of space by mussels is enhanced by C. fragile. Given that mussels, in turn, have the potential to reduce recruitment rates of C. fragile, quick recovery of mussel beds after disturbances could be crucial for controlling the abundance of this alga on breakwaters. Results also suggest that the effects of introduced species on native assemblages can be explained only through studies encompassing different life-stages of interacting organisms.     

Sources and biochemical composition of suspended particulate material in a submarine cave with sulphur water springs

Sources, biochemical composition and nutritional value of suspended particulate material were investigated from February 1994 to February 1995 in a submarine cave (Grotta Azzurra, Capo Palinuro, southwestern Italy) with hot sulphur springs and associated mats of chemolithoautotrophic bacteria in its innermost dark part (Snow Hall). Concentrations of total suspended material (TSM), particulate inorganic material (PIM), organic carbon (POC), organic nitrogen (PON), chlorophyll a (Chl a), phaeopigments (Phaeo), carbohydrates (TCH), proteins (TPR) and lipids (TLI) were measured at four stations along an outside–inside transect, in order to address whether the quantity and quality of suspended particles varied over time with increasing distance from the entrance of the cave and estimate the relative contribution of chemosynthesis versus photosynthesis in supplying POC to cave heterotrophs. The abundance and biochemical composition of suspended material available to filter-feeders varied over time, but no significant quantitative or qualitative differences were detected along the outside–inside transect. Concentrations of TSM and of its different compounds (PIM, POC, PON, Phaeo, TCH, TPR, TLI) were homogeneous among the four stations or fluctuated without any consistent trend, with no apparent ageing and degradation of organic material in the innermost dark station. Conversely, concentrations of Chl a significantly decreased from outside to inside the cave at all sampling periods. It is suggested that suspended POC in Grotta Azzurra consists of mixed assemblages of particles coming from advection of photosynthetic material from the open sea and local inputs of carbon by sulphur-oxidizing bacteria. Based on POC/Chl a ratios, the relative contributions of chemosynthesis versus photosynthesis in supplying POC to benthic heterotrophs was estimated to be 31 and 69%, respectively. Received: 9 December 1996 / Accepted: 14 January 1997     

Photochemical behavior of parathion in the presence of humic acids from different origins

This paper reports the effect of ultraviolet radiation on the degradation of pesticide ethyl parathion in the presence of humic acids. Ethyl parathion was completely degraded in 300 min using an artificial lamp of 7.41 x 10(-10) einstein/s. Humic acid from peat did not influence the photochemical rate (k = 8.92 x 10(-3) min). However, in the presence of aquatic humic acid, the photochemical rate was higher (11.5 x 10(-3) min). The analytical determinations show the presence of p-nitrophenol and aminophenol in the reaction medium during the photochemical experiments. The kinetic of degradation in all experiments obeyed a first-order reaction pattern.     

Evaluation of the electrochemical behavior of pentachlorophenol by cyclic voltammetry on carbon paste electrode modified by humic acids.

Humic substances, or natural recalcitrant organic matter, have an important role in the environment for their plant nutritional functions or for their capability to control the mobility of xenobiotic substances, such as pesticides. To verify the electrochemical behavior of pentachlorophenol (PCP), cyclic voltammetry was used because of its versatility. The following two different electrodes were used: carbon paste electrode (CPE) and carbon paste electrode chemically modified with humic acid (HACMCPE). The results demonstrated that PCP was better accumulated at the HACMCPE electrode, as a consequence of a larger current signal than at the CPE electrode. Cyclic voltammograms showed oxidation steps of PCP itself and probable production of quinonelike compounds.