Benthic Fish Research Articles

Ecological impacts of management practices in agricultural drain networks: a literature synthesis

Drain networks are essential for connecting farming landscapes to waterways to help mitigate floods and convey water downstream. Unfortunately, drains also convey nutrients and sediments from surface or tile drain run-off, which can impact critical habitats for benthic macroinvertebrates and fish communities, including many species at risk of extinction. To bridge discussions around drainage and ecological values associated with sustainable management of water resources in drainage systems, we conducted a comprehensive literature synthesis on the ecological impacts of drain management practices (DMPs) and best management practices (BMPs). To inform drain management at a regional scale, we extracted key findings from 111 peer-reviewed studies with similar physical attributes and management contexts representative of southwestern Ontario’s agricultural landscapes. Across studies, impacts of management practices were assessed over relatively short time periods (1 month − 2 years), limiting understanding of the long-term impacts and ecological or management trade-offs. Frequently measured water quality indicators included carbon, nitrogen, and phosphorus concentrations. Fish biodiversity and abundance were the most commonly measured biodiversity indicators. Recent studies suggest that biodiversity in drain systems is highly resilient and consists of common species that can cope with management activities. Despite literature gaps, findings suggest that while both practices maintain critical drain functions, trade-offs between flood mitigation, biodiversity and water quality remain underexplored. BMPs have the potential to offer multiple co-benefits and greater uptake across the region and across agricultural landscapes in Canada yet place-based evidence is lacking. Cross-sector partnerships can help bolster efforts to critically assess and implement local solutions.

Abundance and Characteristics of Fibrous Microplastics and Microfibers Isolated in Mullus barbatus from the Adriatic Sea—Preliminary Investigation

Despite the wide distribution of textile microfibers in the marine environment, there is still limited knowledge on microfiber ingestion in fish species intended for human consumption, mostly due to analytical issues. The present study aims to assess the occurrence of microfibers in red mullet (Mullus barbatus) samples collected from the Italian waters of the central Adriatic Sea. M. barbatus is a bottom fish that lives in contact with sediment and therefore was proposed as a sentinel species for the monitoring plastic pollution. A visual approach based on the evaluation of specific microfiber surface morphology was applied for the identification of particles of different origins. The preliminary findings showed the presence of microfibers in 80% of red mullet samples with a mean of 5.95 microfibers/individual. The majority (>80%) of the isolated microfibers were of natural/artificial origin, while the dominant colors were blue and black. The obtained results confirmed that benthic fish species are susceptible to microfiber ingestion and indicate the high availability of these particles in the Adriatic basin. Considering the spectroscopic drawbacks in microfiber analyses and the need to improve the current knowledge on the rate of contamination of fishery products, the visual approach could be a feasible, easy, and accessible method in the study of microfiber pollution, and the assessment of consumer health risks.

Feeding ecology of Antarctic toothfish, Dissostichus mawsoni in the subarea 88.3 (Bellingshausen Sea and eastern Amundsen Sea) of the Southern Ocean

Understanding feeding ecology is essential for ecosystem-based management. As dietary data can show differences depending on the spatiotemporal and ontogenetic aspects of the sample, the results should be derived based on various size classes and samples over a wide spatiotemporal range. Morphological analysis of the stomach contents of Dissostichus mawsoni, a piscivore, collected at depths of 603–2,113 m in subarea 88.3 during the Antarctic summer fishing seasons from 2016 to 2020 was used to assess the dietary composition according to the research block, fishing season, depth, and size. Here, we used 1,639 D. mawsoni specimens with a total length range of 44.5–189.0 cm. The dietary composition of D. mawsoni did not show significant differences by fishing season but differed with research block, depth, and size. Macrouridae dominated research blocks 88.3_1 and 88.3_3; Nototheniidae dominated research blocks 88.3_2 and 88.3_6; and Channichthyidae dominated research blocks 88.3_4 and 88.3_5. The proportion of Nototheniidae decreased as depth increased, whereas the consumption of Channichthyidae increased gradually with depth in research blocks 88.3_3 and 88.3_4. The proportion of Channichthyidae decreased as body size increased, whereas the consumption of Macrouridae increased gradually with body size in both blocks 88.3_3 and 88.3_4. During the study period, the dietary composition of D. mawsoni in both blocks 88.3_3 and 88.3_4 did not show significant temporal differences, suggesting that these data could be used as a baseline for identifying future environmental changes in the region. This study provides information on the relationships between various species and benthic fish fauna, which are essential for ecosystem-based management.

Ulva prolifera Stress in the Yellow Sea of China: Suppressed Antioxidant Capacity and Induced Inflammatory Response of the Japanese Flounder (Paralichthys olivaceus).

As the largest green macroalgal bloom in the Yellow Sea of China, the overgrowth and degradation of Ulva prolifera (U. prolifera) have a harmful effect on marine organisms and the aquaculture industry. However, the regulation mechanism of U. prolifera stress on the antioxidant capacity and inflammatory response of marine fish is still not completely understood. A 15-day exposure experiment was conducted to evaluate the effects of U. prolifera stress on the antioxidant capacity and inflammatory response of the Japanese flounder (Paralichthys olivaceus) (283.11 ± 6.45 g). The results showed that U. prolifera stress significantly decreased their survival rate. Serum total antioxidant capacity (T-AOC) and non-specific immune-related enzyme activities were significantly impacted under U. prolifera conditions. Moreover, U. prolifera stress significantly decreased T-AOC, superoxide dismutase (SOD) activity, and catalase (CAT) activities in the liver, while malondialdehyde (MDA) contents were significantly increased. Similarly, antioxidant-related gene (cat, nrf2, and keap1) expressions were synchronously downregulated in the liver under U. prolifera stress. Furthermore, U. prolifera stress significantly upregulated pro-inflammatory gene (tnf-α, il-1β, ifn-γ, and p65) expressions and the phosphorylation levels of the p38 and JNK MAPK pathways in the head kidney. In addition, endoplasmic reticulum (ER) stress-related gene and protein expressions were also upregulated in the head kidney. Overall, these results revealed that U. prolifera stress suppressed the antioxidant capacity and induced an inflammatory response in the Japanese flounder. This study could advance the understanding of the adverse effects of U. prolifera stress on marine benthic fish and promote the sustainable development of aquaculture.

Differences in the Synergic Accumulation of Toxic Elements in Pelagic and Benthic Fish from Glacier-Fed Rivers of the Dzungarian Alatau

Abstract The determination of potentially toxic element concentrations in fish is an important topic from the point of view of both nature conservation and human consumption. The aim of this study was to assess the concentrations of S, K, Ca, Cr, Mn, Fe, Zn, Rb, Sr, Mo, and P in benthic and pelagic fish species in the Karatal river, which is fed by melting glaciers from the Dzungarian Alatau in Kazakhstan. In September 2022, 48 fish samples were collected. It has been demonstrated that the accumulation of chemical elements in fish species can be explained by both the physiological parameters of the fish species and the influence of glaciers that feed river habitats. The data presented in this study provide a synergistic view of pollutants affecting fish populations. Benthic fish contained more manganese and strontium than pelagic species, while the mutual accumulation of potassium, chromium, rubidium, and molybdenum was higher in pelagic fish. The synergistic concentration of calcium and phosphorus in pelagic fish was higher than that in benthic species, while the amount of zinc and sulfur was higher in benthic animals. Relatively elevated levels of mercury in fish were found. The study contributes to the discussion about the role of glacial environments in loading pollutants to aquatic systems.

Effects of light regimes and benthic fish disturbance on the foraging behavior of Vallisneria natans in heterogeneous sediments.

In shallow eutrophic lakes, submersed macrophytes are significantly influenced by two main factors: light availability and benthic fish disturbance. Plant foraging is one of the most crucial aspects of plant behavior. The present study was carried out to effects of light regimes and fish disturbance on the foraging behavior of Vallisneria natans in heterogeneous sediments. V. natans was cultivated in heterogeneous sediments with four treatments: high-light regime (H), high-light regime with benthic fish (HF), low-light regime (L), and low-light regime with benthic fish (LF). We use plant trait network analysis to evaluate the relationships between traits in heterogeneous sediments. We found the plant foraging intensity was positively correlated with trait network modularity. The biomass of stem, maternal plant biomass ratio, and ramet number were the hub traits of plant growing in heterogeneous habitats. Although the plant relative growth rate (RGR) was positively correlated with foraging intensity, the hub traits had closer links with plant RGR than foraging intensity. Light regime and benthic fish indirectly affected the plant foraging intensity by changing the chlorophyll a content and pH of overlying water. Overall, our analysis provides valuable insights into plant foraging behavior in response to environmental changes.

Intraspecific and Interspecific Variations in Habitat Usage by Hemimyzon formosanus and Sinogastromyzon nantaiensis in Riffle Areas of a Mountain Stream

In this study, we explored the structure of two migratory fish species and their variations along the longitudinal gradient of a stream by examining abiotic factors such as spatial scale elements and environmental factors, and biotic factors such as competition. The studied fish species, i.e., Hemimyzon formosanus and Sinogastromyzon nantaiensis, were sampled from the middle and upper reaches of the Nanzihsian Stream using the electrofishing technique, and data were collected on the physical environment covered by the electric grid. Statistical analyses confirmed that the interspecific and the intraspecific hydraulic habitat environments of the two species were different, i.e., H. formosanus was distributed relatively upstream and S. nantaiensis was distributed relatively downstream. Therefore, the habitat use of the two benthic fish species was different. The Nanzihsian Stream experienced an extreme flood event in 2009. The densities of adult and juvenile H. formosanus and S. nantaiensis are significantly higher than those before the extreme flood event in 2021, so we suggest that the H. formosanus and S. nantaiensis populations have recovered to those of the stages before the extreme flood event. We provide an integrated approach for applying engineering and biology to the context of future projects involving river dredging after extreme floods.

Anisakid Presence in the European Conger, Conger conger, from Spanish Mediterranean Waters.

The European conger, Conger conger, is a benthic marine fish species with a geographical distribution extending through the northeastern Atlantic and the Mediterranean. Despite being extensively distributed and widely appreciated by Spanish consumers, studies regarding parasite presence in this fish are scarce. In the present work, a hundred and eight specimens from the Mediterranean coast of northeastern Spain (Catalan waters) were surveyed for the presence of nematode parasites. Several species were morphologically identified: third-stage larvae of Anisakis type I (sensu Berland, 1961) (n = 131), third-stage larvae of Anisakis type II (sensu Berland, 1961) (n = 18), third- and fourth-stage larvae and adults of Hysterothylacium spp. (n = 48), adults of Cucullanus sp. (n = 391), and adults of Cristitectus congeri (n = 69). Moreover, some fish and decapode species were also observed as part of the host's diet, with the most detected preys being Micromesistius poutassou, Sardina pilchardus, Macropipus sp., and Goneplax rhomboides. This represents the first survey of nematode parasites infecting C. conger from the northeastern Spanish Mediterranean waters. Among the parasite species detected, the presence of Anisakis species should be highlighted as the ingestion of C. conger parasitized with these larvae could potentially lead to anisakiasis in consumers.

Heavy Metal Bioaccumulation in Highly Consumed Pelagic and Benthic Fish and Associated Health Risk.

The present study investigated the levels of Manganese (Mn), Cadmium (Cd), Copper (Cu), Zinc (Zn), Lead (Pb) and Iron (Fe) in the tissues of a benthic fish (Clarias gariepinus) and a pelagic fish (Oreochromis niloticus), which are highly consumed in Ghana. The fish were collected from the Weija reservoir, which is an important source of fishery and potable water in Accra, Ghana. The results indicate heavy metal accumulation in all the tissues (gills, liver and muscles) analyzed. The bioaccumulation of all the metals was lowest in the muscles compared to the liver and gills in both species. The bioaccumulation of the metals was generally higher in the tissues of the catfish, except for Fe and Zn. Fe was higher in the gills and liver of the tilapia, and Zn was higher in the liver of the tilapia. The analysis of relationships between metal levels in the different tissues and the size of the fish showed a few significant correlations. The results also showed that all metals showed no potential health risk to consumers, as THQs and TTHQs in tilapia and catfish were less than one, and the metal levels in both species were all below the FAO/WHO maximum permissible limits.

Chemical warfare agents and their risk assessment in Daphnia magna and fish in the Baltic Sea – 15 years of measurements

The Baltic Sea is one of the world's largest brackish waters, it is drained through the Danish Straits into the Kattegat, and almost enclosed by nine countries. The Baltic Sea is one of the world's most polluted water bodies thus facing a wide range of environmental threats towards its water resources, such as fish stocks, and coastal environments and economics. Chemical warfare agents (CWAs) that were dumped following the Second World War are known to occur in intact or degraded states in sediments and are documented to affect benthic fauna and fish as well as having injured fishermen having accidentally caught lumps of CWAs in their nets. However, a thorough mapping of remaining CWAs and degradation products and an understanding of the environmental risks does not exist although more than 75 years have passed. This study compiles and analyzes published/peer-reviewed data, generated since 2005 in five selected comprehensive studies, on sediment measurements of known dumped CWAs and degradation products in the Baltic Sea. As a worst-case approach, sediment concentrations are transformed to concentrations in near-bottom water, which represents Predicted Environmental Concentrations (PECs) to marine biota. To investigate the accuracy and representativeness of toxicological values, which are fundamental in risk assessments, two cases are considered: Case 1 (specificity) uses toxicological data (EC50 or NOEC) for Daphnia magna and fish with applied assessment factors (AF) to derive Predicted No-Effect Concentrations (PNECs) for organoarsenical and non-arsenical CWAs; Case 2 (robustness) uses partly Danish Environmental Quality Standards (DK EQS) for arsenicals, and partly a Water Quality Criterion (WQC) for arsenicals, representing the marine environment. From 872 data points risk quotients (RQs=PEC/PNEC) are calculated. In Case 1 exceedances of risk for the sum of chemicals (sumRQ>1) occur 24 and 1 times for Daphnia magna and fish, respectively, without applying AFs. 263 and 120 exceedances are found for Daphnia magna and fish, respectively, when applying AFs. Case 2 shows 0 (WQC) and 25 (DK EQS) exceedances for arsenicals when using more robust toxicological values, however, at the expense of specificity of chemicals and target species. The results underline the importance of obtaining more representative and accurate toxicological data (lowering AFs) in order to increase the accuracy of the risk estimates. This quantitative state of risk towards representative marine species indicates that there are indeed potential risks, and it qualifies the understanding and debate on the challenges and future actions regarding dumped chemical munitions in the Baltic Sea.

Fluctuations of Galapagos mid-water and benthic reef fish populations during the 2015–16 ENSO

El Niño Southern Oscillation (ENSO) events have impacted the marine environment of the Galapagos, causing massive die-offs of corals and megafauna, and benthic habitat shifts. With ENSO events predicted to intensify under climate change scenarios it is important for managers to have an evidence-based understanding of how these events may affect fish assemblages in the Galapagos. We assess the abundance and size fluctuations of benthic and mid-water shore fishes during the 2015–16 “Godzilla” ENSO using data from baited remote underwater stereo-video surveys collected on four occasions over 2015–16. We found significant differences in the assemblage structure between the pre-El Niño, El Niño onset, El Niño receding, and La Niña onset sampling periods. Mackerels (i.e. Trachurus murphyi and Decapterus spp.) had a ∼480% greater relative biomass, 229% greater relative abundance, and 20.6% greater size during La Niña onset compared to El Niño. With the onset of La Niña we observed a severalfold increase in the abundance of mid-water species including large Carangids, medium-size Scombrids, elasmobranchs (i.e. Sphyrna lewini, Carcharhinus galapagensis) and several other bentho-pelagic taxa. We also found evidence of seasonal abundance fluctuations across years, independent of seasonal effects, in Scarids, Haemulids, Labrids, Chaetodontids, and Carangids. Although the 2015–16 ENSO appears to have had a lesser impact on the Tropical Eastern Pacific than past El Niño events, it was linked to changes in the abundance of several species of key ecological and economic importance. This information furthers our understanding of the influence of large-scale climatic events on fish populations and improves our ability to predict how these populations may change under future climate scenarios.

Ecological variation in invasive brown trout (Salmo trutta) within a remote coastal river catchment in northern Patagonia complicates estimates of invasion impact.

Salmonids were first introduced into the Chilean fresh waters in the 1880s, and c. 140 years later, they are ubiquitous across Chilean rivers, especially in the southern pristine fresh waters. This study examined the brown trout (Salmo trutta) and native taxa ecology in two adjacent but contrasting rivers of Chilean Patagonia. During spring 2016 and spring-fall 2017 we examined the variation in benthic macroinvertebrate and fish community composition and characterized fish size structure, stomach contents, and stable isotopes (δ13 C and δ15 N) to understand population structure, fish diet, and trophic interactions between S. trutta and native taxa. The native Galaxias maculatus (puye) dominated the fish community (74% of abundance). S. trutta was less abundant (16% of survey catch) but dominated the fish community (over 53%) in terms of biomass. S. trutta showed distinct diets (stomach content analysis) in the two rivers, and individuals from the larger river were notably more piscivorous, consuming native fish with a relatively small body size (<100-mm total length). Native fishes were isotopically distinct from S. trutta, which showed a wider isotopic niche in the smaller river, indicating that their trophic role was more variable than in the larger river (piscivorous). This study provides data from the unstudied pristine coastal rivers in Patagonia and reveals that interactions between native and introduced species can vary at very local spatial scales.

Performance of European oysters (Ostrea edulis L.) in the Dutch North Sea, across five restoration pilots

IntroductionThe European flat oyster (Ostrea edulis) is a biogenic reef former, internationally recognised as threatened and declining in the NE Atlantic by OSPAR and one of the focal species in nature inclusive designs in offshore windfarms in The Netherlands. Oyster reefs offer habitat to many other benthic hard substrate and fish species and provide ecosystem functions such as shelter and feeding grounds. European flat oyster reefs have disappeared from the Dutch North Sea in the early 1900s due to overfishing and diseases but are now subject of nature restoration under the Dutch Marine Strategy.MethodSince 2018, pilot projects have started in the Dutch North Sea to restore European flat oysters at suitable locations, such as offshore windfarms or natural reefs, which are protected from bottom trawling. We compared European flat oyster performance in five pilot projects, using translocated adult oysters sourced from Ireland, Norway, and the Netherlands. The aim of this research was to assess the performance of translocated oysters between pilots, to assess the installation and monitoring techniques, and to come forward with recommendations for future pilot projects.ResultsWe found that translocation of both foreign sourced flat oyster populations (Ireland and Norway in nearshore and offshore areas) and local oysters (in nearshore areas) result in good oyster performance. Oysters were able to grow (max 3.67 mm/month) and reproduce (larvae present) in their new environment. We found that growth rate was explained by origin and average water temperature, to a lesser extent by number of months, location and salinity and not to other environmental factors such as pH and O2. Correlations between growth and environmental conditions need to be considered with caution, since not all pilots were sampled just before and after the growing season. Oysters were Bonamia-negative at the start and end of the pilots, indicating that the offshore Dutch North Sea is still Bonamia-free.Discussion, conclusions, recommendationsBy the year 2050 more than ten new offshore farms will be constructed in the Dutch North Sea and some sites will be suitable for oyster restoration. We conclude that local and foreign sourced oysters performed well at all locations. Based on the success and failure of the different outplacement and monitoring techniques, we provide recommendations on good practice for the future, including developing standardized monitoring protocols. This will enable better inter-site comparisons in upcoming oyster restoration pilots.

Top of the food chains: an ecological network of the marine Paja Formation biota from the Early Cretaceous of Colombia reveals the highest trophic levels ever estimated

Abstract The Mesozoic Marine Revolution restructured the world’s ocean biodiversity into the complex marine ecosystems of today. This revolution began during the Triassic but the origin of this complexity is poorly understood due to a lack of detailed ecosystem reconstructions throughout time. We present the first site-specific ecological network for a marine Mesozoic fauna based on the Early Cretaceous Paja Formation biota of Colombia that preserves numerous, large-bodied, predatory marine reptiles. The trophic food-web was quantitatively reconstructed based on inferred trophic interactions of marine producers, consumers, and large apex predators. Compared to well-studied Caribbean reef ecosystem networks, the Paja biota network is missing a great proportion of benthic invertebrates and fishes, despite its rich higher trophic levels. We hypothesize that the ammonites from the Paja biota either mirrored the diversity represented by some fishes today or established a novel trophic unit with no living analogue. Recalibrating the Paja biota network to trophic analogues in the Caribbean, such as sea turtles, estimates that the largest Paja marine reptile hyper-apex predators occupied trophic levels a full tier higher than any extant marine apex predator. The Paja biota network is a starting point to tracing the evolution of marine ecosystems across the Mesozoic Marine Revolution.

Carbon nanofibers caused oxidative stress and disrupted anti-predator responses in common spiny loach

Carbon nanofibers, recently recognized pollutants, have been heavily used among the nanomaterials in many industries. Due to the poor suspension-stability, carbon nanofibers tend to sediment at the bottom of waterbodies and hence can be consumed by the bottom-dwellers. The current investigation evaluates the impact of carbon nanofibers at concentrations between 0.1 and 10 mg L−1 on the common bottom dweller spiny loach Lepidocephalichthys thermalis inhabiting Indian rivers. Carbon nanofiber exposure elevated the activities of the hepatic antioxidant enzymes superoxide dismutase, catalase, peroxidase and glutathione S-transferase, as oxidative stress markers. The fish behaviour patterns were examined by testing the effect of carbon nanofibers on predator recognition ability using kairomones, conspecific alarm cues, and dietary cues. The carbon nanofiber-exposed fish showed a loss of predator-recognition abilities. The results collectively demonstrated the carbon nanofiber driven hepatic oxidative damage and impaired predator-recognition ability in L. thermalis. The investigation, first of its kind, highlights the toxic potential of the carbon nanofibers on benthic fishes.

Artificial water-level fluctuation modulates trophic niches of benthic fish assemblages in one of the world's largest reservoirs

The impoundment of the Yangtze River and construction of the Three Gorges Dam and Reservoir created an unnatural flow regime with a 30 m water-level fluctuation and four artificial seasons that differ from the river's natural flow-regime timing. Using stable isotopes, we selected 15 common benthic fish species representing five trophic guilds to analyze seasonal variation in production sources, trophic niche width, and niche overlap. We hypothesized that, similarly to a natural flow regime, artificial hydrological seasons effectively influence fish trophic niches. We found consistency in seasonal shifts in the contribution of aquatic and terrestrial producers to fish biomass. δ13C and δ15N depicted seasonal changes in intra-guild trophic niche width and intra- and inter-guild niche overlap. Considering that the Three Gorges Reservoir's flow regime is artificially regulated, our findings suggest that water-level fluctuation is one of the key mechanisms driving such trophic shifts and allowing multiple species to coexist. Given the increased cascaded large reservoir construction and the concomitant creation of unnatural flow regimes in large rivers worldwide, these findings are timely. Our findings contribute to improving water-level management by optimizing rhythmicity while balancing flood control and fish protection.

Systematic evaluation of a spatially explicit ecosystem model to inform area-based management in the deep-sea

The long-term provision of ecosystem goods and services depends on the operationalisation of ecosystem-based management approaches that ensure effective conservation and sustainable use of marine resources. This management challenge is addressed internationally through two United Nations instruments: Sustainable Development Goal (SDG) 14 - Life Below Water, and the Convention on the Law of the Sea (UNCLOS) for the Conservation and Sustainable Use of Marine Biological Diversity in Areas Beyond National Jurisdiction (BBNJ Agreement). To achieve sustainability and conservation goals as described in SDG 14 and the BBNJ Agreement, a combination of management tools, including area-based management tools (ABMTs), is necessary. Spatially explicit ecosystem models can inform policy frameworks by enabling ecosystem-wide assessments of ABMTs with indicators that track their management performance. However, the operational use of these complex models depends on the confidence and uncertainty of their predictions. Here, we present a framework to systematically evaluate the performance of a spatially explicit ecosystem model for deep-sea and open-ocean environments, using the ecosystem model for the EEZ of the Azores (NE Atlantic, Portugal) as a case study. The systematic approach aimed to determine the model's suitability as a tool to inform area-based management in the deep-sea. The framework was applied to Ecospace, the spatial-temporal module of the ecological modelling suite Ecopath with Ecosim. It consisted of a stepwise approach for model development and assessment through key parameterisation steps. The steps served for calibration of model parameter values and formal evaluation of temporal and spatial results against the best available reference data. Overall, this approach proved useful in identifying key model sensitivities and sources of uncertainty that arise when considering spatial variability in trophodynamics in the ecosystem model. Moreover, we concluded the model i) effectively predicted the observed inter-annual variability of benthic fish stocks in response to fisheries, trophic interactions, and environmental factors and ii) showed good and moderate spatial goodness-of-fit in replicating reference spatial distribution patterns of stocks and fishing activities. Despite its strengths, the spatial model has limitations related to uncertainties in model parameterisation and the spatial variability of trophodynamics. The systematic assessments presented in this study provide a framework for future model applications to predict the ecosystem-wide impacts of alternative spatial management measures in the deep-sea.

Stressors affecting the ecological status of temporary rivers in the Mediterranean region

Temporary rivers are widespread in the Mediterranean region and impose a challenge for the implementation of the Water Framework Directive (WFD) and other environmental regulations. Surprisingly, an overarching analysis of their ecological status and the stressors affecting them is yet missing. We compiled data on the ecological status of 1504 temporary rivers in seven European Mediterranean region countries and related their ecological status (1) to publicly available data on pressures from the European WISE-WFD dataset, and (2) to seven more specific stressors modelled on a sub-catchment scale. More than 50 % of the temporary water bodies in the Mediterranean countries reached good or even high ecological status. In general, status classes derived from phytobenthos and macrophyte assessment were higher than those derived from the assessment of benthic invertebrates or fish. Of the more generally defined pressures reported to the WISE-WFD database, the most relevant for temporary rivers were ‘diffuse agricultural’ and ‘point urban waste water’. Of the modelled more specific stressors, agricultural land use best explained overall ecological status, followed by total nitrogen load, and urban land use, while toxic substances, total phosphorus load and hydrological stressors were less relevant. However, stressors differed in relevance, with total nitrogen being most important for macrophytes, and agricultural land use for phytobenthos, benthic invertebrates and fish. For macrophytes, ecological quality increased with stressor intensity. The results underline the overarching effect of land use intensity for the ecological status of temporary water bodies. However, assessment results do not sufficiently reflect hydrological stress, most likely as the biological indicators used to evaluate these systems were designed for perennial water bodies and thus mainly target land use and nutrient impacts. We conclude that biomonitoring systems need to be updated or newly developed to better account for the specific situation of temporary water bodies.

Toxicopathic effects of waterborne Cd in sole juveniles, a prospective pollution monitoring sentinel for estuarine ecosystems

IntroductionEstuarine ecosystems are under high anthropogenic pressure and receive a wide Q7 variety of contaminants, including metals. They can remain trapped in estuarine sediments at high concentrations for long periods but eventually they can be released to the overlying water and become toxic for the resident benthic biota. As a consequence, biomonitoring programs surveying the health status of estuaries and coastal areas count with benthic species for the assessment of health disturbances in these specific ecosystems. The present investigation aims at recognizing toxicopathic effects elicited in estuarine life stages of the benthic fish Solea senegalensis on exposure to waterborne Cd, a model compound for metal contamination.MethodsBiological responses to metal exposure were assessed based on the application of a “biomarker + histopathology” approach. Two-year old sole juveniles were exposed to various concentrations of waterborne Cd for 3 and 7 days (Control; Low Cd: 1 µg/l; Mid Cd: 10 µg/l and High Cd: 1000 µg/l). Liver samples were collected for chemical analysis at day 7. Biological samples were collected at days 3 and 7 for biochemical (brain and liver), histochemical (liver) and histopathological analysis (liver, gills and gonad).ResultsBrain acetyl cholinesterase was inhibited after 7 days exposure, indicating neurotoxic effects on exposure to 1000 µg Cd/l. Hepatic catalase and glutathione-Stransferase were induced at day 3 and inhibited at day 7, which suggests a bell-shaped response. A dose-dependent lysosomal membrane destabilization in hepatocytes was recorded at day 7. In parallel, histopathological lesions in gills, liver and gonad were more frequent at day 7 in soles exposed to high Cd concentrations.DiscussionOverall, the “biomarker + histopathology” approach revealed that waterborne Cd causes toxicopathic effects in sole juveniles upon exposure to environmentally relevant concentrations (10 µg Cd/l). The effects were clearly time dependent, and thus it is conceivable that more severe biological effects would be elicited by these low concentrations of Cd at longer exposure periods. Therefore, biomarkers and histopathology in combination provide early-warning indications of altered health status after waterborne Cd exposure in sole juveniles, a prospective sentinel for biological effects assessment of metal contamination in pollution monitoring programs in estuaries and coastal areas.

Analysis of metabolite differences between South Korean and Chinese yellow goosefish (Lophius litulon) using capillary electrophoresis time-of-flight mass spectrometry

The yellow goosefish is a benthic fish that belongs to the family Lophiidae and order Lophiiformes and is distributed in the Yellow and East China Seas. This study aimed to distinguish between yellow goosefish from different geographical origins by analyzing their metabolites. Capillary electrophoresis time-of-flight mass spectrometry was used to analyze metabolite profiles in the muscle tissues of yellow goosefish to distinguish between Korean and Chinese yellow goosefish. In total, 271 putative metabolites were extracted using 50% acetonitrile in water. Principal component analysis and orthogonal partial least squares discriminant analysis (OPLS-DA) were used to distinguish different geographical origins using the metabolite profiles obtained. The R2 and Q2 values of the OPLS-DA model were 0.856 and 0.695, respectively, indicating that the model was well-fitted and had good predictability. The heat map revealed that nucleic acid and amino compounds differed between the Korean and Chinese fish, and the variable importance in the projection scores obtained from OPLS-DA showed that there were geographical differences in the primary metabolites (5′-methylthioadenosine, adenosine, uridine 5-diphosphate, guanosine 5-diphosphate, urea, homocarnosine, O-acetylcarnitine, cycloleucine, cycloleucine S-adenosylmethionine, S-adenosylhomocysteine, ethanolamine, myo-inositol 1-phosphate), which were identified as potential candidate biomarkers.