Influence of Chronic Exposure to Treated Sewage Effluent on the Distribution of White Blood Cell Populations in Rainbow Trout (Oncorhynchus mykiss) Spleen

Impairment of immune function in aquatic animals has been proposed as a possible consequence of low-level contamination of surface waters with anthropogenic substances such as through the discharge of wastewater into rivers, lakes, and oceans. The study at hand investigated the effects of chronic (32 weeks) exposure to sewage treatment plant (STP) effluent on the prevalence and distribution of different leucocyte populations in spleen samples of rainbow trout (Oncorhynchus mykiss). To simulate an infection, fish were injected intraperitoneally (ip) with inactivated Aeromonas salmonicida salmonicida, 6 weeks prior to the termination of the experiment. Immunohistological analysis revealed a marked decrease in thrombocyte numbers, an increase of monocytes, altered distribution of B-cells, and higher surface immunoglobulin expression, as well as activation of MHC class II expression in the spleen after exposure to 15% (v/v) effluent. The most prominent finding of the present study, however, was the occurrence of intraplasmatic deposits or inclusions with strong autofluorescence in spleen sections from effluent-exposed trout. In addition to effluent effects, injection of trout with A. salmonicida stimulated infiltration of monocytes, increased staining intensity on thrombocytes, and enhanced MHC class I expression in larger leucocytes surrounding melanomacrophage centres. In general, the current study demonstrates a marked, potentially adverse effect of STP effluent on spleen leucocytes and on the integrity of spleen tissue. The observed response suggests a constant unspecific stimulation of different leucocyte populations and is reminiscent of chronic inflammatio

Bioaccumulation and Ecotoxicity of Synthetic Musks in the Aquatic Environment

Due to the fact that both nitro and polycyclic musk fragrances and their metabolites are not readily biodegradable in most sewage treatment plants and thus appear in the aquatic environment, the emphasis in this chapter is laid on understanding and evaluating their potential for bioaccumulation and hence their possible adverse impact (acute and chronic toxicity) on aquatic ecosystems. The bioaccumulation of these fragrances in aquatic organisms is principally governed by their inherent structure (parent compounds as well metabolites produced by microbial degradation in sewage treatment plants) and hence by their bioavailability, lipophilicity and the species specific capability of aquatic organisms to metabolize these compounds to readily excretable forms. Consequently, all potential adverse effects, whether acute, subchronic or chronic must be seen primarily as the result of the latter compound specific characteristics. Generally speaking nitro musk fragrances, due to their high bioaccumulation potential and higher resilience toward metabolic conversion appear to have potentially a greater environmental influence than their polycyclic counterparts. However, all presently available data, although primarily based on mammalian studies and limited aquatic toxicological assessments and despite their restriction in breadth and depth of detailed mechanistic understanding, suggest that neither of the musk fragrance classes pose an immediate or long-term hazard to the aquatic ecosystem despite their presence in environmental samples. However, prudence dictates that their accumulation in various organisms of several trophic levels in the aquatic ecosystems is unacceptable and that this situation should be ameliorated

Occurrence and elimination of cyanobacterial toxins in drinking water treatment plants

Toxin-producing cyanobacteria (blue-green algae) are abundant in surface waters used as drinking water resources. The toxicity of one group of these toxins, the microcystins, and their presence in surface waters used for drinking water production has prompted the World Health Organization (WHO) to publish a provisional guideline value of 1.0 μg microcystin (MC)-LR/l drinking water. To verify the efficiency of two different water treatment systems with respect to reduction of cyanobacterial toxins, the concentrations of MC in water samples from surface waters and their associated water treatment plants in Switzerland and Germany were investigated. Toxin concentrations in samples from drinking water treatment plants ranged from below 1.0 μg MC-LR equiv./l to more than 8.0 μg/l in raw water and were distinctly below 1.0 μg/l after treatment. In addition, data to the worldwide occurrence of cyanobacteria in raw and final water of water works and the corresponding guidelines for cyanobacterial toxins in drinking water worldwide are summarized

Presence of Planktothrix sp. and cyanobacterial toxins in Lake Ammersee, Germany and their impact on whitefish (Coregonus lavaretus L.)

Due to the increasing oligotrophy of Lake Ammersee, southern Germany, metalimnic Planktothrix have become one of the dominant planktonic species causing regular blooms. Whitefish (Coregonus lavaretus) is the dominant local fish species with great importance for the fishing industry. Recently, whole age groups of this fish species have disappeared and since 1991, average body-weight has decreased. The causes for this remain unclear. Planktothrix species produce the cyclic peptide toxin desmethyl microcystin-RR, which inhibits glycogen metabolism and has detrimental effects on the development of aquatic organisms. During blooms, gut contents of whitefish displayed a blue discoloration, possibly representing phycobiliproteins typical for cyanobacteria. This study aimed to elucidate the impact of Planktothrix blooms on fish population dynamics. Planktothrix cell counts, performed by epifluorescence microscopy, showed blooms to contain up to 80,000 cells/ml. Microcystin levels of 1-5g/mg dry weight in Planktothrix extracts and 0.08g/l in water samples, were determined via HPLC and protein-phosphatase inhibition assay. Planktothrix filaments were detected in gut contents of whitefish. In addition, microcystins could be detected in gut contents via ELISA. Similarly, immunoprobing with microcystin-antibodies demonstrated microcystin-protein adducts in liver homogenates of whitefish caught during Planktothrix blooms. Furthermore, Planktothrix extracts proved cytotoxic to trout hepatocytes as determined by MTT reduction. Whitefish eggs and larvae, obtained during blooms in winter 1998 and 2000 in a Lake Ammersee hatchery, were studied for developmental progress. Malformations typical for cyanobacterial toxin exposure were observed

Cyanobacterial toxins : removal during drinking water treatment, and human risk assessment

Cyanobacteria (blue-green algae) produce toxins that may present a hazard for drinking water safety. These toxins (microcystins, nodularins, saxitoxins, anatoxin-a, anatoxin-a(s) , cylindrospermopsin) are structurally diverse and their effects range from liver damage, including liver cancer, to neurotoxicity. The occurrence of cyanobacteria and their toxins in water bodies used for the production of drinking water poses a technical challenge for water utility managers. With respect to their removal in water treatment procedures, of the more than 60 microcystin congeners, microcystin-LR (L, l-leucine ; R, l-arginine) is the best studied cyanobacterial toxin, whereas information for the other toxins is largely lacking. In response to the growing concern about nonlethal acute and chronic effects of microcystins, the World Health Organization has recently set a new provisional guideline value for microcystin-LR of 1.0 µg/L drinking water. This will lead to further efforts by water suppliers to develop effective treatment procedures to remove these toxins. Of the water treatment procedures discussed in this review, chlorination, possibly micro-/ultrafiltration, but especially ozonation are the most effective in destroying cyanobacteria and in removing microcystins. However, these treatments may not be sufficient during bloom situations or when a high organic load is present, and toxin levels should therefore be monitored during the water treatment process. In order to perform an adequate human risk assessment of microcystin exposure via drinking water, the issue of water treatment byproducts will have to be addressed in the future

Water-borne diclofenac affects kidney and gill integrity and selected immune parameters in brown trout (Salmo trutta f. fario)

The detection of residues of various pharmaceuticals in surface waters during the last two decades has prompted concerns about possible adverse effects of this kind of pollution on aquatic organisms. The objective of the present study was to investigate effects of the non-steroidal anti-inflammatory drug diclofenac, one of the pharmaceuticals most prevalent in surface waters, on brown trout (Salmo trutta f. fario), a salmonid species native to German rivers. Brown trout were exposed to 0.5, 5 and 50 μg/L diclofenac for 7, 14 and 21 days, whereby the lowest exposure concentration is comparable with concentrations commonly found in the aquatic environment. Fish exposed to diclofenac displayed significantly reduced haematocrit levels after 7 and 14 days of exposure. After 21 days, trout were examined for histopathological alterations, whereby diclofenac exposure resulted in increased monocyte infiltration in the liver, telangiectasis in gills, and the occurrence of interstitial hyaline droplets, interstitial proteinaceous fluid and mild tubular necrosis in trunk kidney. Concurrent immunohistological analysis revealed an increase of granulocyte numbers in primary gill filaments, as well as granulocyte accumulation and increased major histocompatibility complex (MHC) II expression in kidney, suggestive of an inflammatory process in these organs. Moreover, the ability of diclofenac to hinder the stimulation of prostaglandin E2 synthesis was shown in head kidney macrophages of brown trout in vitro. These findings support the hypothesis that environmental exposure of fish to diclofenac provokes the same mechanism of action in these non-target organisms as previously described for mammalian species and can thus lead to similar (possibly adverse) effects. In general, the present study suggests that exposure of brown trout to diclofenac in concentration ranges commonly found in the environment can result in adverse effects in various organs and possibly compromise the health of affected fish populations