Common Goby Pomatoschistus Microps Research Articles

Polymerase chain reaction as a promising tool for DNA-based diet studies of crustaceans

Studying the diet of crustaceans based on the direct visual inspection of the gut contents can be difficult because they can ingest only a portion of the prey and further crush it into very small pieces, making a very few food items identifiable. Here, the usefulness of molecular methods to identify the species present in the gut contents of two crustaceans, the shore crab Carcinus maenas and the brown shrimp Crangon crangon, was tested. Stomach contents were removed, and their total genomic DNA extracted followed by amplification (PCR) with four specific prey mtDNA primers. Since both crustaceans are opportunistic predators, preying upon around 40 different species, the study was restricted to common potential preys in the sampled area, the Minho Estuary (Portugal): the common goby Pomatoschistus microps, the ragworm Hediste diversicolor, the flounder Platichthys flesus and the peppery furrow shell Scrobicularia plana. After testing the most appropriate methodology for DNA extraction and PCR amplification to detect the presence of each potential prey with positive control samples, the same methodology was applied to the stomach content samples. The molecular methods allowed for detection of the presence of P. microps, P. flesus and H. diversicolor in the stomachs of both crustaceans. Therefore, once potential prey and their availability in the system are known, PCR technique can be an alternative tool to overcome some of the limitations of traditional methods in the study of the crustaceans’ diet, even when stomach contents include a great part of ‘detritus’. This study reflects also the need to develop more tools (primers) to improve the assessment of predator–prey interactions in aquatic ecosytems.

Biomarker and behavioural responses of an estuarine fish following acute exposure to fluoxetine

Antidepressants such as fluoxetine are frequently detected in estuaries and can have profound effects on non-target organisms by interfering with the neural system and affecting essential physiological processes and behaviours. In this context, short-term effects of fluoxetine exposure were analysed in the common goby Pomatoschistus microps, an estuarine resident fish species. Two experiments were conducted with fish exposed to: i) fluoxetine concentrations within the μg/L range for 96 h (0.1, 0.5, 10 and 100 μg/L) and ii) fluoxetine concentrations within the mg/L range for 1 h (1, 5 and 10 mg/L). Acute toxicity was assessed via multiple biomarker responses, namely: activity levels of antioxidant (superoxide dismutase and catalase) and detoxification enzymes (ethoxyresorufin O-deethylase and glutathione S-transferase); and biomarkers of effects (lipid peroxidation and DNA damage) and of neurotoxicity (acetylcholinesterase inhibition). Furthermore, behavioural responses concerning activity (active time, movement delay and number of active individuals) and feeding (number of feeding individuals) were also recorded and analysed. Acute fluoxetine exposure for 96 h (in the μg/L range) reduced antioxidant CAT activity with increasing concentrations but had no significant effect on SOD activity. Biotransformation enzymes showed bell-shaped response curves, suggesting efficient fluoxetine metabolism at concentrations up to 10 μg/L. No significant damage (LPO and DNAd) was observed at both concentration ranges (μg/L and mg/L), yet 1 h exposure to higher fluoxetine concentrations (mg/L range) inhibited acetylcholinesterase activity (up to 37%). Fluoxetine (at mg/L) also decreased the number of both feeding and active individuals (by 67%), decreased fish active time (up to 93%) and increased movement delay almost 3-fold (274%). Overall, acutely exposed P. microps were able to cope with fluoxetine toxicity at the μg/L range but higher concentrations (mg/L) affected fish cholinergic system and behavioural responses.

Polymerase chain reaction as a promising tool for DNA-based diet studies of crustaceans

Abstract Studying the diet of crustaceans based on the direct visual inspection of the gut contents can be difficult because they can ingest only a portion of the prey and further crush it into very small pieces, making a very few food items identifiable. Here, the usefulness of molecular methods to identify the species present in the gut contents of two crustaceans, the shore crab Carcinus maenas and the brown shrimp Crangon crangon, was tested. Stomach contents were removed, and their total genomic DNA extracted followed by amplification (PCR) with four specific prey mtDNA primers. Since both crustaceans are opportunistic predators, preying upon around 40 different species, the study was restricted to common potential preys in the sampled area, the Minho Estuary (Portugal): the common goby Pomatoschistus microps, the ragworm Hediste diversicolor, the flounder Platichthys flesus and the peppery furrow shell Scrobicularia plana. After testing the most appropriate methodology for DNA extraction and PCR amplification to detect the presence of each potential prey with positive control samples, the same methodology was applied to the stomach content samples. The molecular methods allowed for detection of the presence of P. microps, P. flesus and H. diversicolor in the stomachs of both crustaceans. Therefore, once potential prey and their availability in the system are known, PCR technique can be an alternative tool to overcome some of the limitations of traditional methods in the study of the crustaceans’ diet, even when stomach contents include a great part of ‘detritus’. This study reflects also the need to develop more tools (primers) to improve the assessment of predator–prey interactions in aquatic ecosytems.

Vertebral Anomalies in Common goby Pomatoschistus microps (Gobiidae) Collected from Localities Around the British Isles

Several incidences of skeletal deformities, ranging from 0.83 to 11.18%, were observed in specimens of common goby Pomatoschistus microps collected from 11 shore localities around the British Isles during the period November 1975–July 1977. There is a large variation in the percentage of vertebral abnormalities among the individuals of P. microps across the localities. It is important to document the vertebral anomalies in P. microps from the British Isles, because no such report has been published, although the observations date back 40 years. The possible role of pollution in the localities studied is discussed.

Assessing the effects of temperature and salinity oscillations on a key mesopredator fish from European coastal systems

A population dynamics model was developed to assess the short and long-term effects of temperature and salinity variations in the common goby Pomatoschistus microps in a Portuguese estuary (Minho estuary, NW Portugal). The population was divided into juveniles, females and males, which constituted the model's state variables. Linear regressions between the observed and the predicted density of juveniles, females and the total population were significant. Parameter's sensitivity and uncertainty analysis were estimated. The model was able to satisfactory describe the P. microps population dynamics, and thus was used to simulate the effects of climatic changes on the fish population. Simulations indicated that the common goby population is sensitive to both temperature and salinity changes. Overall, scenarios of more than 3 °C increase caused significant population decreases. Similarly, increased salinities led to a population shrinkage, whereas scenarios of salinity decrease generated an opposite variation on the population. According to the IPCC predictions for climatic tendencies, the population of the common goby will tend to decrease in the near future, experiencing marked oscillations (decrease or increase) during climatic extremes, namely droughts and floods, respectively. These results may be a useful for future planning and management of estuarine systems given that the common goby is an important species of estuarine food webs in many temperate ecosystems.

Female mating competition alters female mating preferences in common gobies.

Mating decisions can be affected by intrasexual competition and sensitive to operational sex-ratio (OSR) changes in the population. Conceptually, it is assumed that both male and female mate-competition may interfere with female reproductive decisions. Experimentally, however, the focus has been on the effect of male competition on mate choice. In many species with paternal care as in the common goby Pomatoschistus microps, the OSR is often female-biased and female mate-competition for access to available nesting males occurs. Using the same protocol for 3 experiments testing the effect of a perceived risk of female mate-competition, I studied female preferences for nest-holding males differing in its nest size (large/small), body size (large/small), and nest status (with/without eggs already in nest) and measured mating decisions, spawning latencies, and clutch size. Regardless of the social context, females preferred males with larger nests. A preference for large males was only expressed in presence of additional females. For nest status, there was a tendency for females to prefer mating with males with an empty nest. Here, female–female competition increased the propensity to mate. The results of this study show that females are sensitive to a female competitive social environment and suggest that in choice situations, females respond to the social context mainly by mating decisions per se rather than by adjusting the clutch size or spawning latency. Females base their mating decisions not only on a male’s nest size but also on male size as an additional cue of mate quality in the presence of additional females.

Integrated multivariate approach of ecological and ecotoxicological parameters in coastal environmental monitoring studies

The coastal ecosystems are recognized worldwide by their ecological an economic importance. In these ecosystems, aquatic life is governed by the abiotic variations, therefore, the interactions between natural stressors and anthropogenic pollution (multiple stressors) may represent an additional threat. Thus, considering these combined effects with the climate change scenarios, it is urgent to develop cost-effective tools to assess the impact of pollution on sensitive and important ecosystems, such as estuaries and coastal lagoons, and implement mitigation plans to prevent the environmental and human health degradation. In order to contribute to this crucial issue, the central objective of this study was to validate and propose an integrated methodology, including ecological and ecotoxicological parameters, to evaluate the effects of natural stressors and pollution on key estuarine fish in real scenarios, using the common goby Pomatoschistus microps (Krøyer, 1838), an important estuarine intermediary predator, as a bioindicator and a North Atlantic coastal lagoon (the Aveiro lagoon; NW coast of Portugal) as a case study area. The methodology included fourteen water quality variables, sediment characteristics, the concentrations of nine metals in sediments and in the fish body, fish condition indexes, eight biomarkers and multivariate statistics (Redundancy (RDA) and Principal Response Curves analysis (PRC)) to integrate the information provided by different parameters. The study was conducted over one year with seasonal sampling (winter, spring, summer and autumn) at four sampling sites with different contamination histories. The integrated approach suggested significant differences between the reference site and the remaining ones, both in biological and environmental descriptors. Bioaccumulation factors suggested that fish bioaccumulated some metals, especially Zn. The overall integration of all selected parameters and methods discriminated locations with different contaminated levels and associated health status of the selected species with multiple stressors. The present work represented a case-study, highlighting the use of biomarkers as early warning indicators of ecosystems health and stressing the importance of using an integration approach through multivariate analysis in biomonitoring studies, providing an important baseline and integrated information that may be used as scientific support for conservation and management and ecological models of estuarine and coastal lagoon systems.

Ecological variation along the salinity gradient in the Baltic Sea Area and its consequences for reproduction in the common goby.

Although it has become clear that sexual selection may shape mating systems and drive speciation, the potential constraints of environmental factors on processes and outcomes of sexual selection are largely unexplored. Here, we investigate the geographic variation of such environmental factors, more precisely the quality and quantity of nest resources (bivalve shells) along a salinity gradient in the Baltic Sea Area (Baltic Sea, Sounds and Belts, and Kattegat). We further test whether we find any salinity-associated morphological differences in body size between populations of common gobies Pomatoschistus microps, a small marine fish with a resource-based mating system. In a geographically expansive field study, we sampled 5 populations of P. microps occurring along the salinity gradient (decreasing from West to East) in the Baltic Sea Area over 3 consecutive years. Nest resource quantity and quality decreased from West to East, and a correlation between mussel size and male body size was detected. Population density, sex ratios, mating- and reproductive success as well as brood characteristics also differed between populations but with a less clear relation to salinity. With this field study we shed light on geographic variation of distinct environmental parameters possibly acting on population differentiation. We provide insights on relevant ecological variation, and draw attention to its importance in the framework of context-dependent plasticity of sexual selection.

Genetic analysis reveals the diversity of larval Gobiidae in a temperate estuary

Using molecular tools to examine Gobiidae, the second most abundant taxon in ichthyoplankton samples in the Gulf of Riga (Baltic Sea), the sand goby Pomatoschistus minutus was the most abundant taxon (82% of all individuals analysed), the common goby Pomatoschistus microps constituted 12% and the black goby Gobius niger 6%. The spatiotemporal distribution of P. microps and G. niger indicated a preference for habitats closer to the river inlet and their abundances increased slightly towards the end of the sampling period in summer. The species composition was interpreted in the context of the prevailing habitat conditions, characterized by extremely low water transparency, low salinity, limited spread of vegetated area and dominance of sandy-muddy substrata.

Use of stable isotope ratios of fish larvae as indicators to assess diets and patterns of anthropogenic nitrogen pollution in estuarine ecosystems

A stable isotope study was carried out to investigate the feeding ecology of the common goby Pomatoschistus microps larvae (Krøyer, 1838), and to assess differences in the response of planktonic food web to nutrient enrichment, in two ecosystems from the Southern European coast with different levels of historical pollution (estuaries of the Minho and Lima Rivers). At each estuary and time (July 2012, November 2012, February 2013, and June 2013), the fish larvae of two size classes (class 0: 0–10mm; class 1: 10–15mm), particulate organic matter (POM), and pelagic zooplankton were collected. The stable isotope mixing model SIAR revealed that, despite temporal differences in the relative proportion of prey items ingested, in both estuaries P. microps larvae feed on both planktonic-hyperbenthic food sources, predating mainly on copepods (from 34% to 60%), Mysidacea (from 16% to 28%), and brachyuran zoea (from 14% to 29%). Fish larvae size classes did not differ significantly for δ15N, and exhibited a very narrow range of the δ13C signature. Enriched δ15N values of all biota in the Lima estuary throughout the study period, with a marked nitrogen enrichment in colder months, are indicative of higher anthropogenic inputs of nitrogen (e.g. sewage and industrial discharges, agriculture) into this system. The δ15N values of fish larvae and other planktonic groups can be a sensitive bioindicator, because they are highly correlated with the nitrogen content of water (ammonium), indicating that this element has transferred through the planktonic food web. Enriched carbon isotope ratios were observed in warmer months, in both estuaries, and the heavier δ13C values in Lima are best explained by differences in the degree of marine influence. This research emphasises the utility of stable isotopes in trophic interactions studies, highlighting the relevance of the stable nitrogen isotope of zooplanktonic communities as a reliable bioindicator to detect patterns of anthropogenic nitrogen contamination in estuarine ecosystems.

Redescription and phylogenetic position of Myxobolus aeglefini and Myxobolus platessae n. comb. (Myxosporea), parasites in the cartilage of some North Atlantic marine fishes, with notes on the phylogeny and classification of the Platysporina

Myxobolus ‘aeglefini’ Auerbach, 1906 was originally described from cranial cartilage of North sea haddock (Melanogrammus aeglefinus), but has subsequently been recorded from cartilaginous tissues of a range of other gadoid hosts, from pleuronectids and from lumpsucker (Cyclopterus lumpus) in the North Atlantic and from a zoarcid fish in the Japan Sea (Pacific).We obtained partial small-subunit rDNA sequences of Myxobolus ‘aeglefini’ from gadoids and pleuronectids from Norway and Iceland. The sequences from gadoids and pleuronectids represented two different genotypes, showing 98.2% identity. Morphometric studies on the spores from selected gadids and pleuronectids revealed slight but statistically significant differences in spore dimensions associated with the genotypes, the spores from pleuronectids were thicker and with larger polar capsules. We identify the morpho- and genotype from gadoids with Myxobolus ‘aeglefini’ sensu Auerbach, and the one from pleuronectids with Sphaerospora platessae Woodcock, 1904 as Myxobolus platessae n. comb. The latter species was originally described from Irish Sea plaice (Pleuronectes platessa). Myxobolus albi Picon et al., 2009 described from the common goby Pomatoschistus microps in Scotland is a synonym of M. ‘aeglefini’. The Pacific Myxobolus ‘aeglefini’ represents a separate species, showing only 97.4–97.6% identity to the Atlantic species. In phylogenetic analyses based on SSU rDNA sequences, these and some related marine chondrotropic Myxobolus spp. form a distinct well supported group. This clusters with freshwater and marine myxobolids and Triangula and Cardimyxobolus species, in a basal clade in the phylogeny of the Platysporina. Members of family Myxobilatidae, Ortholinea spp. (currently Ortholineidae) and sequences of some other urinary system infecting myxosporeans form a well supported clade among members of the suborder Platysporina. Based on phylogenetic analyses, we propose the following changes to the classification of Myxosporea: i) Ortholineidae is dismantled and Ortholinea spp. transferred to Myxobilatidae, and ii) Myxobilatidae is transferred from suborder Variisporina to Platysporina.

Age at maturity of Mediterranean marine fishes

In this review we collected data on the age at maturity (tm) and maximum reported age (tmax) for 235 stocks of Mediterranean marine fishes, belonging to 82 species, 37 families, 12 orders and 2 classes (Actinopterygii and Elasmobranchii). Among Actinopterygii (mean tm ± SD = 2.20 ± 1.43 y, n = 215), tm ranged from 0.3 y, for the common goby Pomatoschistus microps, to 12 y, for dusky grouper Epinephelus marginatus, while among Elasmobranchii (mean tm ± SD = 5.94 ± 2.47 y, n = 20), tm ranged between 2.7 y, for brown ray Raja miraletus, and 12 y for picked dogfish Squalus acanthias. Overall, the tmax ranged between 1 y, for transparent goby Aphia minuta, and 70 y, for wreckfish Polyprion americanus. The mean tmax of Actinopterygii (tmax ± SD = 10.14 ± 9.42 y) was lower than that of Elasmobranchii (tmax ± SD = 14.05 ± 8.47 y). The tm exhibited a strong positive linear relation with tmax for both Actinopterygii (logtm = 0.58 ´ logtmax – 0.25, r2 = 0.51, P < 0.001) and Elasmobranchii (logtm = 0.67 ´ logtmax – 0.006, r2 = 0.51, P = 0.007). The mean tm/tmax did not differ significantly with sex within Actinopterygii (ANOVA: F = 0.27, P = 0.60, n = 90; females: mean ± SD = 0.276 ± 0.143; males: mean ± SD = 0.265 ± 0.138) and Elasmobranchii (ANOVA: F = 1.44, P = 0.25, n = 10; females: mean ± SD = 0.499 ± 0.166; males: mean ± SD = 0.418 ± 0.133). Finally, the dimensionless ratio tm/tmax was significantly lower (ANOVA: F = 31.04, P < 0.001) for Actinopterygii (mean ± SD = 0.270 ± 0.135, n = 180) than for Elasmobranchii, (mean ± SD = 0.458 ± 0.152, n = 20), when stocks with combined sexes were excluded from the analysis.

Influence of the invasive Asian clam Corbicula fluminea (Bivalvia: Corbiculidae) on estuarine epibenthic assemblages

One of the most widespread invasive alien species (IAS) in aquatic ecosystems is the Asian clam Corbicula fluminea. Several studies have shown that C. fluminea can cause large-scale changes in macrozoobenthic assemblages; however, very few attempted to investigate the effects of this IAS on mobile epibenthic species, such as fishes and crustaceans. In this context, the influence of C. fluminea on epibenthic species was investigated during one year by comparing the associated epibenthic fauna in three nearby sites of the Minho estuary (NW of the Iberian Peninsula), wherein the abiotic conditions are similar but the density of the Asian clam is highly different. From a total of 13 species, six were significantly influenced by C. fluminea; five responded positively, namely the brown shrimp Crangon crangon, the European eel Anguilla anguilla, the common goby Pomatoschistus microps, the brown trout Salmo trutta fario and the great pipefish Syngnathus acus, whereas the shore crab Carcinus maenas was negatively influenced. However, stomach contents analysis revealed that fish and crustacean species do not feed on C. fluminea, suggesting that this IAS is still not a large component of the diet of higher trophic levels in this estuarine ecosystem. Our results suggest that the structure provided by C. fluminea shells is likely to be one of the main factors responsible for the differences observed. C. fluminea physical structure seems to influence the epibenthic associated fauna, when found in densities higher than 1000 ind./m2, with sedentary small-bodied crustaceans and fishes being mainly attracted by the increasing in habitat complexity and consequent enhancement of heterogeneity and shelter availability.

Are Estuarine Fish Opportunistic Feeders? The Case of a Low Anthropized Nursery Ground (the Canche Estuary, France)

Stomach contents of the main fish species (i.e. sprat Sprattus sprattus, sea-bass Dicentrarchus labrax, common goby Pomatoschistus microps and flounder Platichthys flesus) in the Canche nursery ground (France) were examined from May 2006 to March 2007 according to food availability (i.e. macrozoobenthos and zooplankton) to analyse diet composition, trophic competition and prey selection. Overall, 44 prey fish species were identified from the 684 stomach contents examined. Fish diet was characterized by a wide diversity of prey, a relatively high feeding activity (vacuity index ranged between 16.9 and 29.0 % according to species) and spatiotemporal changes, except for D. labrax which did not vary between periods or estuarine zones. Copepods Temora longicornis and Euterpina acutifrons were the most important items in the diet of S. sprattus; for D. labrax, the dominant prey was the amphipod Gammarus sp., while Platichthys flesus and Pomatoschistus microps showed a more similar trophic niche (similarity percentage = 39 %) with diets consisting of nematodes and amphipods. Spatiotemporal sharing of trophic resources by fish and high food resources in the Canche estuary was examined, and very limited diet overlap was observed, indicating that competition for food resources was limited. Differences between the available preys and fish diets demonstrated that fish do not select the most abundant food resources. S. sprattus showed a selection for Tachidius sp. and cladocerans; D. labrax for Gammarus sp., Hediste diversicolor and to a lesser extent nematodes and Corophium sp.; Pomatoschistus microps for nematodes and Gammarus sp.; and Platichthys flesus for nematodes, Gammarus sp., H. diversicolor and Corophium sp. It was concluded that the studied fish exhibit a specialist rather than opportunistic feeding strategy.

Single and combined effects of microplastics and pyrene on juveniles (0+ group) of the common goby Pomatoschistus microps (Teleostei, Gobiidae)

Microplastic particles have increasingly been detected in aquatic biota, from zooplankton to fish, raising concern for potential effects on aquatic organisms. In addition, they may potentially influence the toxicity of other contaminants in the marine environment. The aim of this study was to clarify whether polyethylene microspheres (1–5μm) modulate short-term toxicity of the polycyclic aromatic hydrocarbon pyrene to juveniles (0+ group) of the common goby (Pomatoschistus microps). Fish were exposed for 96h to pyrene (20 and 200μgL−1) in the absence and presence of microplastics (0, 18.4 and 184μgL−1). Mortality, bile pyrene metabolites, and biomarkers involved in neurotransmission, aerobic energy production, biotransformation and oxidative stress were quantified. Microplastics delayed pyrene-induced fish mortality and increased the concentration of bile pyrene metabolites. Microplastics, alone or in combination with pyrene, significantly reduced acetylcholinesterase (AChE) activity, an effect also observed for pyrene alone. The mixture also decreased isocitrate dehydrogenase (IDH) activity. No significant effects were found for glutathione S-transferase activity or lipid peroxidation. Overall, results show that: (i) microplastics modulate either the bioavailability or biotransformation of pyrene; (ii) simultaneous exposure to microplastics and pyrene decrease the energy available through the aerobic pathway of energy production; and (iii) microplastics inhibit AChE activity. The mechanism for AChE inhibition appeared to be different for pyrene and microplastics, since simultaneous exposure to both did not increase significantly the inhibitory effect. The observed neurotoxic effects of microplastics per se and the effects on IDH activity of the two stressors combined are of concern because they may increase mortality in natural fish populations. More studies need to be carried out on possible combined effects of microplastics and polycyclic aromatic hydrocarbons on fish, particularly juveniles.

Effects of aniline on marine organisms: Comparison of biomarkers responses in the common goby (Pomatoschistus microps) and the common prawn (Palaemon serratus)

Effects of aniline on marine organisms: Comparison of biomarkers responses in the common goby (Pomatoschistus microps) and the common prawn (Palaemon serratus)

Acute toxic effects of pyrene on Pomatoschistus microps (Teleostei, Gobiidae): Mortality, biomarkers and swimming performance

Pyrene has been reported as one of the most important polycyclic aromatic hydrocarbons (PAHs) found as environmental contaminant in estuaries and coastal areas. Therefore, in the present study, the acute effects (96h) of pyrene on the common goby Pomatoschistus microps, a key species in several European estuaries and lagoons, were assessed through individual exposure of juveniles to 0.125, 0.25, 0.5 or 1mgL−1 of pyrene. Mortality, swimming performance and several biomarkers were used as effect criteria. The 96h median lethal concentration (LC50) was 0.871mgL−1 and the swimming performance of fish was significantly decreased at all the pyrene concentrations tested. A significant increase of bile metabolites was found at increasing concentrations of pyrene (LOEC=0.125mgL−1) indicating the production of metabolites during the biotransformation of the toxicant. Pyrene significantly inhibited the activity of head acetylcholinesterase at 0.5mgL−1 and muscle cholinesterases at 1mgL−1. A bell-shape pattern response in the activity of muscle lactate dehydrogenase and isocitrate dehydrogenase (IDH) was found, with a significant increase of IDH at 0.25mgL−1, suggesting changes in the pathways of energy production. A bell-shape response for the antioxidant enzyme glutathione peroxidase and a less evident bell-shape response of glutathione S-transferase and glutathione reductase were also found. Lipid peroxidative damage was found in liver (0.25mgL−1) and gills (0.50mgL−1). It should be noted that although the concentrations of pyrene tested in the present study are higher than those that have been found in estuarine water and sediments, the occurrence of pyrene as single environmental contaminant is rare; in fact, the most common situation is the contamination by several PAHs, a considerable part of them sharing toxicological properties with pyrene and thus with a high probability of inducing additive or synergistic effects in simultaneous exposures. The findings of the present study are ecologically relevant and should be taken into consideration in the management of estuaries contaminated by petrochemical products. Moreover, effects of pyrene in this species should be further investigated.

Application of an integrated biomarker response index (IBR) to assess temporal variation of environmental quality in two Portuguese aquatic systems

Estuaries are extremely productive systems faced with great anthropogenic pressure, namely from contaminants of both metallic and organic nature which may affect the ecological quality of these systems. Moreover, it is known that contaminants fluctuate seasonally and this could influence the health status of organisms. In order to identify the most affected seasons and areas in two Portuguese aquatic systems with strong anthropogenic influences, a method that combines several biomarker responses into a general “stress index” denominated “integrated biomarker response” (IBR) was applied using the stress responses in the liver of common goby Pomatoschistus microps collected from two sites within both estuaries (Ria de Aveiro and Tagus). Parameters included in the IBR were the biomarkers superoxide dismutase (SOD), catalase (CAT), ethoxyresorufin-O-deethylation (EROD), glutathione s-transferase (GST), metallothioneins (MT), lipid peroxidation (LPO) and condition indices (RNA:DNA ratio and Fulton's condition factor K. Pollutant concentrations in the sediment (metals and PAHs) were also analyzed. Biomarkers in P. microps in Ria de Aveiro lagoon (sites A and B) showed distinct seasonal variation. In site A, IBR highlighted the spring as the season with highest biomarker responses, and RNA:DNA as the most contributing biomarker, while in site B the most impacted season was the summer, associated to the responses of MT and antioxidant enzymes (CAT and SOD), probably as a result of levels of Hg in the sediments. In both sites within the Tagus estuary (C and D) the IBR showed that biomarker responses were higher in autumn, with CAT, EROD, GST and LPO as the most altered biomarkers. In this season the levels of PAHs, Pb and Cr were the highest. Overall, the IBR index provides an integrated approach for assessing the health status of organisms and to identify temporal patterns of contamination.

Seasonal changes in community composition and trophic structure of fish populations of five salt marshes along the Essex coastline, United Kingdom

European intertidal salt marshes are important nursery sites for juvenile fish and crustaceans. Due to the increasing threat of habitat loss, the seasonal changes of salt marsh fish communities need to be understood in order to appreciate the ecological and economic importance of the saltmarsh habitat. This study was the first in Great Britain to investigate the seasonal changes of salt marsh fish communities and the variation in community structure between closely located marsh habitats. Between February 2007 and March 2008, five marshes on three estuaries of the Essex coastline were sampled using flume nets to block off intertidal creeks at high tide. Fourteen fish species were caught. The community overall was dominated by three species that made up 91.6% of the total catch: the common goby Pomatoschistus microps (46.2% of the total catch), juvenile herring Clupea harengus (24.3%), and juvenile and larval sea bass Dicentrarchus labrax (21.2%). Cluster analysis demonstrated clear seasonal patterns, with some community structures unique to specific marshes or estuaries. The marsh fish community shifts from a highly diverse community during spring, to a community dominated by D. labrax and P. microps in autumn, and low diversity during winter months. Gravimetric stomach content analysis of fish community identified three main trophic guilds; macroinvertivores, planktivores and omnivores. The macroinvertivore feeding guild contained D. labrax and P. microps, the two most frequently occurring species. This investigation demonstrates the importance of British salt marshes as nursery habitats for commercial fish species.

Parasitological diversity of the common goby,Pomatoschistus microps(Krøyer, 1838), in estuarine systems along the Portuguese coast

Summary Parasitological diversity of the common goby Pomatoschistus microps along the Portuguese coast was studied based on samples collected using beam trawls in five coastal estuaries (Ria de Aveiro, Tagus, Sado, Mira and Guadiana estuaries) between May and July 2006. The classes Digenea, Cestoda, Nematoda and phylum Mastigophora were found, with Digenea Cryptocotyle sp. and Lecithochirium musculus being the most abundant taxa. Prevalence and mean abundance of Cryptocotyle sp. were highest in Ria de Aveiro (74%) and Mira estuary (28.05), respectively, whereas L. musculus values of both indices were highest in Sado estuary (prevalence = 64%; mean abundance = 11.77). Values varied along the Portuguese coast; the discriminant analysis based on the number of parasites showed some overlap between estuaries, although successfully separating the Sado and Mira estuaries. Overall, variations in estuaries were explained by different environmental pressures, leading to differences on host abundance and life-history of the parasites. Feeding behaviour and habitat selection therefore play a crucial role in shaping the biology, ecology and parasite assemblages of the common goby along the Portuguese coast.