Assessing consequences of marine pollution by hydrocarbons using sponges as model organisms

Soaking up the oil: Biological impacts of dispersants and crude oil on the sponge Halichondria panicea

Used during an oil spill to minimise the formation of an oil slick, dispersants have negative biological effects on marine model organisms. However, no study has investigated the impacts of dispersants on adult sponge individuals. Here, we examine the effects of water accommodated oil fraction (WAF - oil in seawater), chemically enhanced WAF (CEWAF - oil and dispersant in seawater) and Benzo[A]Pyrene on sponge Halichondria panicea at physiological and molecular levels. Sponge clearance rate decreased sharply when exposed to WAF and CEWAF but the oil loading at which the clearance rate was reduced by 50% (ED50) was 39-fold lower in CEWAF than in WAF. Transcriptomic analysis revealed a homogenous molecular response with the greatest number of differentially expressed genes identified in CEWAF samples (1,461 genes). Specifically, genes involved in stress responses were up-regulated. This study presents evidence that the use of dispersants should be considered carefully in areas where sponges are present.

Temporal changes in gene expression and genotype frequency of the ornithine decarboxylase gene in native silverside Basilichthys microlepidotus: Impact of wastewater reduction due to implementation of public policies

Human activity has caused a deterioration in the health and population size of riverine species; thus, public policies have been implemented to mitigate the anthropogenic impacts of water use, watercourse transformation, and pollution. We studied the Maipo River Basin, one of the most polluted with untreated wastewater in Chile, for a period of 12 years (2007-2019). Since the implementation of new public policies, including the operation of a wastewater collector (2012), the Maipo River Basin is currently much less polluted by untreated water than before. To analyze the impact of wastewater reduction in this river basin, we studied the native silverside (Basilichthys microlepidotus), which inhabits both polluted and unpolluted areas of the river basin. Previous studies reported the overexpression of the ornithine decarboxylase (odc) gene, heterozygote deficit, and high frequency of a homozygote odc genotype in silverside populations that inhabit wastewater-polluted sites, suggesting a phenotypic change and genotypic selection in response to pollution. Here, a population affected and another population unaffected by wastewater were studied before and after implementing the wastewater collector. The physicochemical data of water samples, changes in odc expression and microsatellite variability, and odc genotype frequencies were analyzed. The results showed physicochemical changes in the affected site before and after the operation of the wastewater collector. The microsatellite loci showed no changes in either population. The odc expression in the affected site was higher before the operation of the wastewater collector. Significant changes in the genotype frequencies of the odc gene before and after the wastewater collector operation were detected only at the affected site, wherein the homozygous dominant genotype decreased from >59% to <25%. Our results suggest that public policies aimed at mitigating aquatic pollution can indirectly affect both gene expression and genotype frequencies of important functional genes.

Potential Impacts of Offshore Oil and Gas Activities on Deep-Sea Sponges and the Habitats They Form

Sponges form an important component of benthic ecosystems from shallow littoral to hadal depths. In the deep ocean, beyond the continental shelf, sponges can form high-density fields, constituting important habitats supporting rich benthic communities. Yet these habitats remain relatively unexplored. The oil and gas industry has played an important role in advancing our knowledge of deep-sea environments. Since its inception in the 1960s, offshore oil and gas industry has moved into deeper waters. However, the impacts of these activities on deep-sea sponges and other ecosystems are only starting to become the subject of active research. Throughout the development, operation and closure of an oil or gas field many activities take place, ranging from the seismic exploration of subseafloor geological features to the installation of infrastructure at the seabed to the drilling process itself. These routine activities and accidental releases of hydrocarbons during spills can significantly impact the local marine environment. Each phase of a field development or an accidental oil spill will therefore have different impacts on sponges at community, individual and cellular levels. Legacy issues regarding the future decommissioning of infrastructure and the abandonment of wells are also important environmental management considerations. This chapter reviews our understanding of impacts from hydrocarbon exploration and exploitation activities on deep-sea sponges and the habitats they form. These impacts include those (1) at community level, decreasing the diversity and density of benthic communities associated with deep-sea sponges owing to physical disturbance of the seabed; (2) at individual level, interrupting filtration owing to exposure to increased sedimentation; and (3) at cellular level, decreasing cellular membrane stability owing to exposure to drill muds. However, many potential effects not yet tested in deep-sea sponges but observed in shallow-water sponges or other model organisms should also be taken into account. Furthermore, to the best of our knowledge, no studies have shown impact of oil or dispersed oil on deep-sea sponges. To highlight these significant knowledge gaps, a summary table of potential and known impacts of hydrocarbon extraction and production activities combined with a simple "traffic light" scheme is also provided.

Immunotoxicity of washing soda in a freshwater sponge of India

The natural habitat of sponge, Eunapius carteri faces an ecotoxicological threat of contamination by washing soda, a common household cleaning agent of India. Washing soda is chemically known as sodium carbonate and is reported to be toxic to aquatic organisms. Domestic effluent, drain water and various human activities in ponds and lakes have been identified as the major routes of washing soda contamination of water. Phagocytosis and generation of cytotoxic molecules are important immunological responses offered by the cells of sponges against environmental toxins and pathogens. Present study involves estimation of phagocytic response and generation of cytotoxic molecules like superoxide anion, nitric oxide and phenoloxidase in E. carteri under the environmentally realistic concentrations of washing soda. Sodium carbonate exposure resulted in a significant decrease in the phagocytic response of sponge cells under 4, 8, 16 mg/l of the toxin for 96h and all experimental concentrations of the toxin for 192h. Washing soda exposure yielded an initial increase in the generation of the superoxide anion and nitric oxide followed by a significant decrease in generation of these cytotoxic agents. Sponge cell generated a high degree of phenoloxidase activity under the experimental exposure of 2, 4, 8, 16 mg/l of sodium carbonate for 96 and 192 h. Washing soda induced alteration of phagocytic and cytotoxic responses of E. carteri was indicative to an undesirable shift in their immune status leading to the possible crises of survival and propagation of sponges in their natural habitat.

Marine sponges as bioindicators of oil and combustion derived PAH in coastal waters

The present study evaluates the potential of Hymeniacidon heliophila as bioindicator of PAH contamination. For this, concentration of 33 PAH was determined in organisms from sites with different contamination level including the heavily polluted Guanabara Bay, Rio de Janeiro, and less impacted coastal areas. PAH concentration and typology were determined in sponges collected from different depths and in two different seasons. The brown mussel broadly studied as bioindicator was also sampled from the same sites for comparison. Both species provided similar information on total PAH concentration which is related to site contamination level. Sponges, however, revealed slight tendency to accumulation of combustion-derived PAH in relation to petrogenic compounds. Differences in PAH typology between species may derive from the interspecific variation in particle size ingestion. Different hydrocarbon typologies were observed in sponges from dry and wet season and PAH concentration varied with depth. H. heliophila may be used as an alternative approach to investigate the presence and sources of PAH in estuarine areas.

Tubulin posttranslational modifications induced by cadmium in the sponge Clathrina clathrus

As sessile filter feeders, sponges are exposed to environmental stress due to pollutants of both anthropogenic and natural origins and are able to accumulate harmful substances. Thus, sponges are considered a good tool for the biomonitoring of coastal areas. In this study, we used biochemical and immunocytochemical analyses to provide new data on the cadmium-related changes in sponge cells. In particular, we analyzed the effects of different concentrations of cadmium on the microtubule network in the calcisponge Clathrina clathrus. Quantitative densitometry of the immunoblots showed that, while the levels of α- and β-tubulin remained relatively constant in C. clathrus when exposed to 1 and 5 μM CdCl2, there were progressive shifts in the levels of some tubulin isoforms. Exposure for 24h to sublethal concentrations of cadmium reduced the level of tyrosinated α-tubulin and enhanced the levels of acetylated and detyrosinated α-tubulin relative to the levels in controls. Confocal microscopy analysis of immunolabeled tissue sections showed that the inhibitory effect of cadmium was associated with a decrease in the labeling of the cells with a monoclonal antibody that recognizes tyrosinated α-tubulin. By contrast, the reactivity with a monoclonal antibody that recognizes acetylated α-tubulin and with a polyclonal antibody specific for detyrosinated α-tubulin was enhanced at the same time points. Because the acetylation and detyrosination of α-tubulin occur on stable microtubules, the marked enhancement of α-tubulin acetylation and detyrosination in Cd(2+)-treated cells indicates that divalent Cd ions stabilize microtubules. The possibility that Cd(2+) may increase the stability of cytoplasmic microtubules was tested by exposing Cd(2+)-treated cells to a cold temperature (0°C). As shown, the microtubule bundles induced by Cd(2+), which were labeled by the monoclonal antibodies against acetylated and detyrosinated α-tubulin, were resistant to cold.

Bacteria associated with sabellids (Polychaeta: Annelida) as a novel source of surface active compounds

A total of 69 bacteria were isolated from crude oil enrichments of the polychaetes Megalomma claparedei, Sabella spallanzanii and Branchiomma luctuosum, and screened for biosurfactant (BS) production by conventional methods. Potential BS-producers (30 isolates) were primarily selected due to the production of both interesting spots on thin layer chromatography (TLC) plates and highly stable emulsions (E₂₄ ≥ 50%). Only few strains grew on cetyltrimethylammonium bromide and blood agar plates, indicating the probable production of anionic surfactants. The 16S rRNA gene sequencing revealed that selected isolates mainly belonged to the CFB group of Bacteroidetes, followed by Gammaproteobacteria and Alphaproteobacteria. A number of BS-producers belonged to genera (i.e., Cellulophaga, Cobetia, Cohaesibacter, Idiomarina, Pseudovibrio and Thalassospira) that have been never reported as able to produce BSs, even if they have been previously detected in hydrocarbon-enriched samples. Our results suggest that filter-feeding Polychaetes could represent a novel and yet unexplored source of biosurfactant-producing bacteria.

The porifera Hymeniacidon perlevis (Montagu, 1818) as a bioindicator for water quality monitoring

Because sponges are promising bioindicators, we present here a multispecies comparison of the bioconcentration capacity for copper, zinc and the hydrocarbon fluoranthene. The spatial distribution of sponge populations was studied in 17 areas in intertidal zones on the Lower Normandy coast (France) to determine the most common species with the highest bioaccumulation capacity. Results are compared with published data on blue mussels Mytilus edulis from the Réseau d'Observation de la Contamination Chimique biomonitoring network. A total of 720 sponge samples were collected to assess species richness. Samples were analysed for metal concentrations by flame-mode atomic absorption spectrometry. Analyses of polycyclic aromatic hydrocarbon were sub-contracted. Species richness varies according to the water mass concerned. The most common species in the study area showing the highest bioconcentration in its soft tissues is Hymeniacidon perlevis, which contains about 20 times the zinc, 44 times the copper and 16 times the fluoranthene levels found in mussels. The variability of contaminant concentrations in H. perlevis is also systematically higher than those in mussels. The results obtained for this sponge closely reflect the heterogeneous distribution of contaminants. This study demonstrates that H. perlevis has a much higher capacity to accumulate in situ contaminants than the blue mussel M. edulis. H. perlevis meets all the requirements of a good bioindicator suitable for use in an integrated monitoring programme. In the near future, controlled cultivation of H. perlevis will allow us to produce sufficient quantities of this species to carry out ecotoxicological tests and in situ biomonitoring by caging.

MAP kinase cell signaling pathway as biomarker of environmental pollution in the sponge Suberites domuncula

In the present study, we analyzed the effects of two major pollutants of the environment, tributyltin (TBT) and water-accommodated fraction (WAF) of diesel oil, on MAP kinase activation, apoptosis induction and DNA damage, in the marine sponge Suberites domuncula. Our results clearly demonstrated a differential activation of the MAPKs depending on the chemicals tested. TBT induced the activation of p38 and JNK while diesel oil enhanced activation of both ERK and p38. The activation of MAPKs was observed after 1 h exposure and 6 and 24 h of recovery in seawater. In addition, DNA fragmentation, assessed by two techniques, the Fast micromethod(®) and the TUNEL assay, was detected after sponges were treated with both chemicals. Moreover, the study of caspase 3/7 activity showed that apoptosis was induced and triggered with all concentrations of TBT but only at high diesel oil concentrations. After TBT exposure, a correlation was observed between JNK activation, caspase 3 activity and DNA damage while p38 activation followed the two latter parameters at high concentrations of diesel oil, suggesting that sponges enhanced a specific apoptotic pathway depending on the xenobiotic tested. This study demonstrated a high signal response by the sponge Suberites domuncula to the tested chemicals. Cell signaling pathway studies may thus be of use in water quality biomonitoring programs.

The use of marine sponge, Haliclona tenuiramosa as bioindicator to monitor heavy metal pollution in the coasts of Gulf of Mannar, India

The results of the present research study indicate that the heavy metal accumulation in the marine sponges provide evidence as an excellent bioindicators for monitoring heavy metal pollution between near and offshore environments of Mandapam coast of "Gulf of Mannar (GoM), India". The heavy metal concentrations in sea water and accumulation in the tissues of Haliclona tenuiramosa were analyzed by ICP-MS (inductively coupled plasma-mass spectrometry). The concentrations of metals in the coastal waters of nearshore (< 0.5 km from shore) were always higher than those in the offshore waters (2-5 km away from shore). Likewise, sponges living in the nearshore accumulated greater concentrations of heavy metals (As, Cd, Co, Cu, Fe, Mn and Ni) ranging from 2 to 17 times higher concentration than the sponges located away from the shore. A positive correlation between concentration levels in water and bioaccumulation in tissues was observed. The bioaccumulation of heavy metals in sponge tissue were in order of Fe > Mn > Ni > Cu > As > Co > Cd in both the near and offshore stations. The present results justified that a more comprehensive monitoring of presence of heavy metals in H. tenuiramosa of surrounding GoM, is necessary to help a better mitigation of the problem.

Sponge-associated marine bacteria as indicators of heavy metal pollution

Sponges invariably filter a large volume of seawater and potentially accumulate heavy metals and other contaminants from the environment. Sponges, being sessile marine invertebrates and modular in body organization, can live many years in the same location and therefore have the capability to accumulate anthropogenic pollutants such as metals over a long period. Almost all marine sponges harbor large number of microorganisms within their tissues where they reside in the extra- and intra-cellular spaces. Bacteria in seawater have already been established as biological indicators of contamination. The present study was intended to find out the heavy metal resistance pattern of sponge-associated bacteria so as to develop suitable biological indicators. The bacteria associated with a marine sponge Fasciospongia cavernosa were evaluated as potential indicator organisms. The associated bacteria including Streptomyces sp. (MSI01), Salinobacter sp. (MSI06), Roseobacter sp. (MSI09), Pseudomonas sp. (MSI016), Vibrio sp. (MSI23), Micromonospora sp. (MSI28), Saccharomonospora sp. (MSI36) and Alteromonas sp. (MSI42) showed resistance against tested heavy metals. Based on the present findings, Cd and Hg emerged as the highly resistant heavy metal pollutants in the Gulf of Mannar biosphere reserve. Plasmids in varied numbers and molecular weights were found in all the isolates. Particularly the isolates MSI01 and MSI36 harbored as many as three plasmids each. The results envisaged that the plasmids might have carried the resistance factor. No correlation was observed in number of plasmids and level of resistance. The literature evidenced that the sponge-associated bacteria were seldom exploited for pollution monitoring though they have been extensively used for bioprospecting. In this background, the present findings come up with a new insight into the development of indicator models.

Square-wave anodic-stripping voltammetric determination of Cd, Pb, and Cu in a hydrofluoric acid solution of siliceous spicules of marine sponges (from the Ligurian Sea, Italy, and the Ross Sea, Antarctica)

Square-wave anodic-stripping voltammetry (SWASV) was set up and optimized for simultaneous determination of cadmium, lead, and copper in siliceous spicules of marine sponges, directly in the hydrofluoric acid solution (approximately 0.55 mol L(-1) HF, pH approximately 1.9). A thin mercury-film electrode (TMFE) plated on to an HF-resistant epoxy-impregnated graphite rotating-disc support was used. The optimum experimental conditions, evaluated also in terms of the signal-to-noise ratio, were as follows: deposition potential -1100 mV vs. Ag/AgCl, KCl 3 mol L(-1), deposition time 3-10 min, electrode rotation 3000 rpm, SW scan from -1100 mV to +100 mV, SW pulse amplitude 25 mV, frequency 100 Hz, DeltaE(step) 8 mV, t(step) 100 ms, t(wait) 60 ms, t(delay) 2 ms, t(meas) 3 ms. Under these conditions the metal peak potentials were Cd -654 +/- 1 mV, Pb -458 +/- 1 mV, Cu -198 +/- 1 mV. The electrochemical behaviour was reversible for Pb, quasi-reversible for Cd, and kinetically controlled (possibly following chemical reaction) for Cu. The linearity of the response with concentration was verified up to approximately 4 microg L(-1) for Cd and Pb and approximately 20 microg L(-1) for Cu. The detection limits were 5.8 ng L(-1), 3.6 ng L(-1), and 4.3 ng L(-1) for Cd, Pb, and Cu, respectively, with t(d) = 5 min. The method was applied for determination of the metals in spicules of two specimens of marine sponges (Demosponges) from the Portofino natural reserve (Ligurian Sea, Italy, Petrosia ficiformis) and Terra Nova Bay (Ross Sea, Antarctica, Sphaerotylus antarcticus). The metal contents varied from tens of ng g(-1) to approximately 1 microg g(-1), depending on the metal considered and with significant differences between the two sponge species.

Petrosia testudinaria as a biomarker for metal contamination at Gulf of Mannar, southeast coast of India

Coastal marine ecosystems in many parts of the world are under unrelenting stress caused by urban development, pollutants and other ecological impacts such as building of infrastructure, land reclamation for port and industrial development, habitat modification, tourism and recreational activities. The present work is a first extensive field study using the marine sponge, Petrosia testudinaria as a biomarker to detect heavy metal pollution between near and off shore environment of 'Gulf of Mannar', India. Sponges were collected from near shore (0.5-1 km) and offshore (5-7 km), locations and their metal concentrations were determined by inductively coupled plasma-mass spectrometry (ICPMS). Our results show that the near shore sponge accumulated greater concentrations of heavy metals (Al, Fe, Mn, As, Ni, Co, Cu, Se) ranging from 0.13 to 64 times higher concentration than the sponges located away from the shore. The results indicate that the accumulated metals alter the macromolecule composition (sugars, proteins and lipids) in near shore sponges. Frequent monitoring is necessary to assess the eco-health of the marine environment by choosing bioindicator species like sponges, which provide accurate, reliable measurement of environmental quality.

Effects of 12 years' operation of a sewage treatment plant on trace metal occurrence within a Mediterranean commercial sponge (Spongia officinalis, Demospongiae)

The present field study uses Spongia officinalis for assessing trace metals occurrence in time and space within Mediterranean rocky communities. Nine sites were selected in the Marseille area for studying spatial trends in 12 metal concentrations. Long term changes in 8 metal concentrations were assessed at sites that had been sampled before and 12 years after the opening of a treatment plant. Spongia officinalis highly concentrated all the trace metal surveyed excepted Hg and Cd. The overall contamination level registered provided a classification of the study sites which is congruent with that given by other studies on pollutant accumulation in neighbouring sandy-bottoms or benthic assemblages. Among the metals studied, Fe, Pb, Cr are those that best highlighted a pollution gradient. In the present study, only Cd concentration did not vary in space. Except for Ni, all pollutant concentrations clearly decreased between 1984 and 1999. This very impressive decrease in heavy metal concentrations within the Marseille area represents an indisputable evidence of the improvement of the seawater quality resulting from 12 years' operation of the Marseille sewage plant. Moreover, the significant decrease also recorded in the reference population at Port-Cros might reflect an overall improvement in the seawater quality of the NW Mediterranean.

The random amplified polymorphic DNA (RAPD) assay to determine DNA alterations, repair and transgenerational effects in B(a)P exposed Daphnia magna

The random amplified polymorphic DNA (RAPD) is a useful assay for the detection of genotoxin-induced DNA damage and mutations. In this study, we have further evaluated the potential of this assay to measure benzo(a)pyrene [B(a)P]-induced DNA changes, and repair (in kinetic experiments) as well as transgenerational effects in the water fleas, Daphnia magna. The organisms, which reproduce parthenogenetically, were exposed to 50 microg L(-1) B(a)P for 3 or 6 days and were allowed to recover in clean medium for 12 or 9 days, respectively. Qualitative and quantitative changes were observed in RAPD profiles generated not only from the B(a)P exposed Daphnia but also from previously treated organisms during the recovery experiments. The fact that some of the RAPD changes disappeared at the end of both recovery experiments suggested that the DNA effects were fully repaired or reversed. In addition, some of the B(a)P-induced RAPD alterations detected in parental D. magna were also observed in the offspring patterns. This suggested that DNA alterations that occurred in germ cells were probably transmitted to the next cohorts. The present study shows that the RAPD method can be useful to qualitatively assess the kinetics of DNA changes, repair and transgenerational effects and such effects could potentially be linked to survival and reproductive success at higher levels of biological organisation. In addition, the water fleas have efficient capabilities to repair or reverse B(a)P-induced DNA effects. Finally, unrepaired or misrepaired genetic damage induced by genotoxins such as B(a)P could be transmitted to next generations in these parthenogenetically reproducing organisms.

Sex-specific biotransformation and detoxification after xenobiotic exposure of primary cultured hepatocytes of European flounder (Platichthys flesus L.)

Sex-specific effects of sublethal concentrations of known effective pro-oxidants such as 100,200 and 400 microM benzo[a]pyrene (B[a]p), 50 microM nitrofurantoin (NF) and 100 microM hydrogen peroxide (H2O2) on biotransformation pathways were studied in isolated hepatocytes of immature female and male European flounder (Platichthys flesus L.). Cell responses were assessed at the level of: (1) stress induction as measured by formation of reactive oxygen species (ROS), mainly superoxide radicals, and induction of cytochrome P450 (CYP450) biotransformation activity; (2) cellular antioxidant defences, both non-enzymatic (reduced glutathione) and enzymatic (DT-diaphorase (DTD) or quinone oxidoreductase, EC 1.6.99.2); (3) detoxification (aldehyde dehydrogenase (ALDH), EC 1.2.1.3); and (4) cellular damage as measured by reduced lysosomal membrane stability and cell death. As there is increasing evidence that 17-beta-estradiol interferes with certain pathways of xenobiotic biotransformation, we additionally tested the effects of different concentrations of 17-beta-estradiol (0.2-10 microM) alone and 17-beta-estradiol (1 microM) in combination with 100 microM B[a]p. Parameters were monitored after 1 and 9 days of exposure by quantitative image analysis of chromogenic or fluorogenic reaction products. Our study revealed sex-dependent differences in cellular stress responses. In hepatocytes of female flounder, biotransformation was slower and the capacity of non-enzymatic antioxidant defences and detoxification of toxic aldehydes was lower than in males. Additional administration of 17-beta-estradiol enlarged these differences between the sexes with respect to biotransformation activity and antioxidant defence in xenobiotic-induced injury. These findings may explain the higher susceptibility of female flounder to toxic and carcinogenic compounds in the marine environment.

Glucose-6-phosphate dehydrogenase: the key to sex-related xenobiotic toxicity in hepatocytes of European flounder (Platichthys flesus L.)?

The role of glucose-6-phosphate dehydrogenase (G6PDH) in oxidative stress responses was investigated in isolated intact living hepatocytes of immature female and male European flounder (Platichthys flesus L.) because it is the major provider of NADPH needed as reducing power for various detoxification pathways. Hepatocytes were exposed to sublethal concentrations of effective prooxidants such as 100 microM hydrogen peroxide (H(2)O(2)), 100, 200 and 400 microM benzo[a]pyrene (B[a]p) and 50 microM nitrofurantoin (NF) during culture. Since there is evidence that 17-beta-estradiol inhibits certain pathways of xenobiotic biotransformation, we tested also the effects of different concentrations of 17-beta-estradiol (0.2, 1 and 2 microM) alone and 1 microM in combination with 100 microM B[a]p on G6PDH activity. After short-term (1 day) and long-term (9 days) exposure, G6PDH activity was quantified in intact living hepatocytes by a tetrazolium salt method using tetranitroblue tetrazolium salt (TNBT). Hepatocytes obtained from male fish generally showed higher G6PDH activity than those of females. We observed significant inhibition of G6PDH activity by all oxidative stressors and 17-beta-estradiol in both sexes of fish independently of culture conditions, but inhibition was stronger in cells of females than in cells of males. A cumulative effect of the steroid and B[a]p was not found. Our results indicate a sex-dependent inhibitory effect of all stressors and 17-beta-estradiol on G6PDH activity in flounder hepatocytes independent of prooxidant activity of the specific compound. Consequently, NADPH supply for xenobiotic detoxification and other cellular antioxidative defence mechanisms may be different in livers of female and male flounder. The strongly decreased supply of NADPH in hepatocytes of females may explain the reduced and/or delayed NADPH-dependent activity of xenobiotic biotransformation systems such as cytochrome P450 (CYP450) and a lower capacity of non-enzymatic defence systems such as reduced glutathione that is particularly observed in female flounder. Moreover, the strong inhibition of G6PDH in livers of female flounder may explain higher susceptibility for xenobiotic toxicity and, therefore, potentially a higher risk to develop liver cancer.

Toxic effects of endocrine disrupters on freshwater sponges: common developmental abnormalities

Endocrine disrupters are of substantial concern, in large part because effects of these compounds on the growth and development of many aquatic organisms are unknown. We examined toxic effects of three substances (ethylbenzene, nonylphenol, and bisphenol A), that are known to be hormonally active in many animals, on growth and development of two species of freshwater sponge. A common developmental abnormality was observed when sponges were treated with each of these compounds. The three compounds also caused significant reductions in growth rates. Lower concentrations resulted in malformed water vascular systems in several replicates. The utility of freshwater sponge bioassays is discussed as it relates to understanding possible mechanisms of action of endocrine disrupters on aquatic invertebrates.

Sex-related responses to oxidative stress in primary cultured hepatocytes of European flounder (Platichthys flesus L.)

Effects of oxidative stress induced by xenobiotic compounds were studied in primary cultures of isolated hepatocytes of immature European flounder (Platichthys flesus L.) of both sexes caught in a relatively unpolluted area of the German Bight (North Sea). Cells were exposed to oxidative stressors such as 100 microM hydrogen peroxide (H2O2), 100 microM benzo[a]pyrene (B[a]p) and 50 microM nitrofurantoin (N-(5-nitro-2-furfurylidene)-1-aminohydantoin; NF) for 2 and 24 h. Cell mortality was determined with the use of the fluorescent ethidium homodimer-1 and calcein. Oxidative stress response was assessed by quantitative analysis of (1) intracellular reactive oxygen species (ROS) formation with dihydrorhodamine 123, (2) lipid peroxidation on the basis of concentrations of lipid hydroperoxides and the lipid peroxidation products malondialdehyde (MDA) and 4-hydroxynonenal (4-HNE) and (3) cellular total oxidant-scavenging capacity (TOSC) using the TOSC assay (Winston et al., 1998). An increase in ROS formation was detected as early as 2 h after exposure to H2O2, B[a]p and NF. After 24 h, stress responses were lower, except following exposure to NF. The pattern of responses differed with the different oxidative stressors. Lipid peroxidation and the capacity to scavenge ROS were increased significantly in both sexes only after exposure to H2O2, whereas B[a]p and NF provoked sex-dependent responses. B[a]p-induced lipid peroxidation and increase in scavenging capacity were observed only in hepatocytes of females, whereas NF initiated these responses only in cells of males. Sex differences in oxidative stress response only after exposure to pro-oxidants that require enzymatic activation infer the importance of biotransformation pathways in stress responses. Because of their sensitivity to oxidative stress, flounder hepatocytes provide a useful model for early risk assessment of xenobiotics.

Genotoxic, carcinogenic, and teratogenic hazards in the marine environment, with special reference to the Mediterranean Sea

Genotoxic, carcinogenic, and teratogenic hazards arising out of pollution in the marine environment are discussed in this article, with special reference to the situation in the Mediterranean area. A number of chemical compounds or complex mixtures relevant to marine pollution, either natural or of anthropogenic origin, are tentatively listed, along with protective factors which may play a counteracting role in the same environment. Harmful substances tend to undergo interactions and transformations in seawater, sediments, and marine biota, due to physical, chemical, microbial, or light-mediated mechanisms. Bioaccumulation phenomena in marine organisms may result from food-chain biomagnification processes or from concentration of pollutants by filter feeders. A variety of sources can account for marine pollution by genotoxic, carcinogenic, and teratogenic compounds, but there is a relative paucity of analytical data concerning the Mediterranean. Metabolic transformations of xenobiotics occur in all marine organisms, the biochemical mechanisms in fish being comparable to those which have been extensively investigated in mammals. Induction of metabolic pathways, and especially of the mixed-function oxygenase system, represents the earliest warning signal of exposure to pollutants. Occurrence of neoplastic diseases is documented by experimental and field studies in marine vertebrates as well as in invertebrates. The association with local pollution phenomena has been recognized in several studies, but other etiopathogenetic factors may be also involved, and in some cases tumors have been reported to be unrelated to chemical pollution. Genotoxic agents have been detected by means of suitable techniques in seawater, sediments, and marine organisms. Several studies have investigated the presence of carcinogen-DNA adducts, DNA damage and repair processes, and cytogenetic alterations, such as chromosomal aberrations, sister-chromatid exchanges, and micronuclei, in tissues of marine organisms. However, monitoring of these end-points under field conditions encounters some limitations and problems. Even more fragmentary is the information on teratogenic effects in marine organisms, although interesting test systems have been set up. On the whole, a quite extensive database on all these toxicological issues is already available in the literature, but further studies are warranted for an adequate assessment of genotoxic, carcinogenic, and teratogenic hazards, and possibly counteracting factors in the marine environment, and specifically in the Mediterranean Sea.

Can a sponge fractionate isotopes?

The study has unequivocally demonstrated that siliceous sponges Spirastrella cuspidifera and Prostylyssa foetida from the same microecological niche exhibit a high degree of species specificity, while accumulating a host of heavy metal ions (Ni, Cr, Cd, Sn, Ti, Mo, Zr). S. cuspidifera accumulated, in addition, 60Co and 63Ni, showing discrimination against other radionuclides, 137Cs and 131I, present in the ambient waters receiving controlled low level waste discharges from a B.W.R. nuclear power station. P. foetida, on the other hand, accumulated only 131I and showed discrimination against other radionuclides including 60Co, although the stable iodine concentrations in both the sponges were the same. The specific activity of 60Co (in becquerels per gram of 59Co) in S. cuspidifera and 131I (in becquerels per gram of 127I) in P. foetida were at least two orders of magnitude greater than in the ambient sea water. That of 63Ni (in becquerels per gram of 62Ni) in S. cuspidifera, on the other hand, was lower by two orders of magnitude than in either abiotic matrices from the same environment. Thus, not only did both the species show bioaccumulation of a specific element, but also preferential uptake of isotopes of the same element, though they were equally available for intake. Such differential uptake of isotopes can possibly be explained in terms of two quite different mechanisms operating, each applicable in a particular case. One is that the xenobiotic isotope enters the environment in a physicochemical form or as a complex different from that of its natural counterpart. If equilibration with the latter is slow, so that the organism acquires the xenobiotic in an unfamiliar chemical context, it may treat it as a chemically distinct entity so that its concentration factor differs from that of stable isotope, thus changing the specific activity. Alternatively, if the xenobiotic is present in the same chemical form as the stable isotope, the only way in which specific activities can be modified is by fractionation on the basis of mass of isotope. In view of the remarkable concentration factors observed for stable and radioactive isotopes of the same element and the specific activities reached, it is desirable that species of sponges, especially from the coastal and estuarine environments, be monitored to detect levels of pollution due to anthropogenic substances.

Activity of benzo[a]pyrene monooxygenase in fish from the Sava River, Yugoslavia: correlation with pollution

Benzo[a]pyrene monooxygenase (B[a]PMO) activity in non-migratory fish from a given river segment is highly correlated to the recent pollutional history of that part of the river. The enzyme activity level can serve as a relevant measure for the harmful pollutant potential in aquatic ecosystems. Caged experimental fish exposed for about 10 days in river segments show BaPMO activity changes with the same predictive validity as that of the natural population.

DNA damage by PAH and repair in a marine sponge

The sponge Tethya lyncurium from the Northern Adriatic has been used as an experimental species. A method is outlined for preparation of DNA which yields a highly purified DNA with a double-strand (ds) molecular weight of 25 M-dalton between single-strand (ss) breaks, which when properly damaged can be cut opposite to ss-breaks with nuclease S1. The molecular weights of the resulting ds-DNA pieces and their distribution has been evaluated by electron microscope photographs. Sponges exposed to benzo[a]pyrene (BaP) in the dark only incorporate BaP-derivatives (BaPD) in small amounts, if any. However, in the presence of light, derivatization to BaP derivatives enables effective coupling to occur, as shown previously (R.K. Zahn et al., 1981). Sponges were exposed to radiolabeled BaP in the presence of light. Coupling of BaPD to the DNA as well as the induction of ss-breaks were measured. Light-mediated coupling is concentration dependent from 0.01-20 ppb BaP with a correlation coefficient of r = 0.84. Under conditions of possible repair, ss-breaks completely disappear from sponge DNA in the course of three weeks while a substantial fraction of the BaP derivatives persists. Double label experiments show that substantial DNA synthesis occurs during this time. Pollution causes a decrease of the molecular weight of unnicked DNA, re-incubation in clean water an increase. A DNA species of 24 M-dalton seems to play a critical role. If its percentage in the DNA population drops below a critical level, recovery is not longer possible. DNA damage by PAH and repair in sponges seems to differ from that of most eucaryotes.