Acute and sub-chronic toxicity bioassays of Olive Mill Wastewater on the Eastern mosquitofish Gambusia holbrooki.

Olive oil production generates large volumes of wastewaters mostly in peri-Mediterranean countries with adverse impacts on the biota of the receiving aquatic systems. Few studies have however documented its toxicity on aquatic species, with an almost total lack of relative studies on fish. We assessed the acute and sub-chronic OMW toxicity, as well as the acute and sub-chronic behavioural, morphological and biochemical effects of OMW exposure on the mosquitofish Gambusia holbrooki. LC50 values of the acute bioassays ranged from 7.31% (24 h) to 6.38% (96 h). Behavioural symptoms of toxicity included hypoactivity and a shift away from the water surface, coupled with a range of morphological alterations, such as skin damage, excessive mucus secretion, hemorrhages, fin rot and exophhalmia, with indications also of gill swelling and anemia. Biochemical assays showed that OMW toxicity resulted in induction of catalase (CAT) and inhibition of acetylcholinesterase (AChE) activities. The implications of our results at the level of environmental policy for the sustainable management of the olive mill industry, i.e. the effective restriction of untreated OMW disposal of in adjacent waterways, as well as the implementation of new technologies that reduce their impact (detoxification and/or revalorization of its residues) are discussed.

Water quality and benthic fauna biodiversity in a unique small wetland at Messinia, Greece.

The wetland of Aghios Floros is located in the Prefecture of Messinia (S. W. Peloponnese, Greece) and occupies a small area, covered permanentlywith water. Flooding of the surrounding area is defended by an artificial channel that discharge large quantity of water into Pamisos River in whose river basin the Aghios Floros station belongs. At the sampling site various physico-chemical and conventional pollution parameters as well as hydrochemical variables were measured during the wet and the dry period of 2011. The hydromorphological and multihabitat approach of RIVPACS method was applied in situ, which gives an overall image of the landscape. The site was classified as 'Good' according to the Greek River Nutrient Classification System (GR.NCS) and the benthic macroinvertebrate fauna assemblages that dominated the area pointed out a 'Good' biological status as well. The biotic and abiotic sample processing, carried out in compliance with the demands of the Water Framework Directive, in general revealed high ecological status of the station. Specifically, a rich diversity and abundance of some macroinvertebrate families was recorded and regarding the aquatic flora the area is dominated by the water lilies species of Nymphaea alba which are unique in the area of Peloponnese.

Effects of olive mill wastewater discharge on benthic biota in Mediterranean streams.

Olive mill wastewaters (OMW) discharging in river ecosystems cause significant adverse effects on their water chemistry and biological communities. We here examined the effects of OMW loads in four streams of a Mediterranean basin characterized by changing flow. The diatom and macroinvertebrate community structures were compared between upstream (control) and downstream (impacted) sites receiving OMW discharge. We also tested if effects occurred at the organism level, i.e. the occurrence of deformities in diatom valves, and the sediment toxicity on the midge Chironomus riparius. We evaluated these effects through a two-year analysis, at various levels of chemical pollution and dilution capacity. The impacted sites had high phenol concentrations and organic carbon loads during and after olive mill (OM) operation, and were characterized by higher abundances of pollution-tolerant diatom and macroinvertebrate taxa. Diatom valve deformities occurred more frequently at the impacted sites. The development of C. riparius was affected by phenolic compounds and organic carbon concentrations in the sediments. The similarity in the diatom and macroinvertebrate assemblages between control and impacted sites decreased at lower flows. Diatoms were more sensitive in detecting deterioration in the biological status of OMW receiving waterways than macroinvertebrates. Our results indicate that the negative effects of OMW extended to the whole benthic community, at both assemblage and organism level.