Disturbances In Fish Research Articles

Addition of tea tree oil (Melaleuca alternifolia) in diet minimize biochemical disturbances in silver catfish Rhamdia quelen exposed to the antiparasitic amitraz

In the present study, we evaluated diets supplemented with Melaleuca alternifolia essential oil (tea tree oil - TTO) as a growth promoter and its possible hepatoprotective effects in Rhamdia quelen exposed to the insecticide amitraz. Six groups (8 per group, in triplicate) were tested: control A (basal diet), B (basal diet + TTO 1.0 mL/kg), C (basal diet +0.84 mL/kg amitraz), D (basal diet +1.19 mL/kg amitraz), E (basal diet +1.0 mL/kg TTO + 0.84 mL/kg amitraz) and F (basal diet + TTO 1.0 mL/kg + 1.19 mL/kg amitraz). Initially R. quelen received diets according to each group. After 14 days, four groups were exposed to two levels of amitraz for a period of 7 days, and were later transferred to amitraz-free water for recovery. We measured levels of reactive oxygen species (ROS) and lipoperoxidation (LOOH) in liver tissue, and activities of enzymes involved in energy metabolism, adenylate kinase (AK) and pyruvate kinase (PK), in addition to zootechnical indices such as length, weight body and fish weight gain. ROS and LOOH levels increased significantly (p < 0.05) in fish exposed to amitraz concentrations, especially in groups of fish not supplemented with TTO. By contrast, AK and PK enzyme activities were significantly lower (p < 0.05) for the groups exposed to amitraz compared to the unexposed group. Finally, fish supplemented with TTO showed better (p < 0.05) zootechnical performance. Addition of TTO minimizes biochemical disturbances in fish exposed to amitraz and serves as a natural additive to improve fish production.

Carp Edema Virus Infection Is Associated With Severe Metabolic Disturbance in Fish.

Significant mortalities associated with emerging viral diseases are challenging the economy of common carp aquaculture. As such, there is an increased need to disentangle how infected fish cope with progressive disease pathology and lose the ability for homeostatic maintenance of key physiological parameters. A natural carp edema virus (CEV) infection outbreak at a carp fish farm provided an opportunity to examine diseased and healthy carp in the same storage pond, thereby contributing to our better understanding of CEV disease pathophysiology. The disease status of fish was determined using PCR-based virus identification combined with analysis of gill pathology. Compared with healthy control carp, the blood chemistry profile of CEV-infected fish revealed major disruptions in electrolyte and acid-base balance (i.e., hyponatraemia, hypochloraemia, hyperphosphatemia, elevated pH, base excess, and anion gap and decreased partial dissolved carbon dioxide). In addition, we recorded hyperproteinaemia, hyperalbuminaemia, hypotonic dehydration, endogenous hyperammonaemia, and decreased lactate along with increased creatinine, alkaline phosphatase, alanine aminotransferase, and aspartate aminotransferase. Red blood cell associated hematology variables were also elevated. The multivariate pattern of responses for blood chemistry variables (driven by sodium, pH, partial dissolved carbon dioxide, ammonia, and albumin in the principal component analysis) clearly discriminated between CEV-infected and control carp. To conclude, we show that CEV infection in carp exerts complex adverse effects and results in severe metabolic disturbance due to the impaired gill respiratory and excretory functioning.

Effect of juvenile omni-benthivorous fish (Carassius carassius) disturbance on the efficiency of lanthanum-modified bentonite (LMB) for eutrophication control: a mesocosm study.

Lanthanum-modified bentonite (LMB) is widely used for eutrophication control and has demonstrated good efficiency in some eutrophic lakes. However, the efficiency of LMB on eutrophication control in some eutrophic lakes, where the structure of food webs is mainly dominated by omni-benthivorous fish, remains ambiguous. Omni-benthivorous fish usually disturbs sediment and promotes the release of internal nutrients, the effect of which on the efficacy of LMB remains to be studied. Thus, a 30-day mesocosm experiment was conducted to determine whether omni-benthivorous fish disturbance and LMB would cause antagonistic responses. LMB significantly reduced dissolved P concentration in overlying water, converting mobile P to bound P in the surface layer of sediment in the absence of crucian carp (Carassius carassius). However, there were significantly negative interaction effects between LMB and crucian carp. Although LMB still effectively reduced the total dissolved phosphorus (TDP) and soluble reactive phosphorus (SRP) concentrations of overlying water in the presence of crucian carp, it had limited efficacy on inhibiting the increased concentrations of suspended solids, particulate nutrients, and chlorophyll a (Chl a) due to crucian carp disturbance. Furthermore, the crucian carp disturbance also increased the risk of mobile P releasing from surface sediment, whether with or without LMB application. The results indicated that the efficacy of LMB was insufficient to offset the negative effect of omni-benthivorous fish disturbance on eutrophication control. Hence, the omni-benthivorous fish also need to be considered for eutrophication control in shallow eutrophic lakes. Some measures need to be taken to control the biomass of omni-benthivorous fish.

The influence of natural and anthropogenic factors on demersal fauna in the western English Channel and Celtic Sea

Displacement of fisheries through management has the potential to re-distribute the anthropogenic pressures associated with fishing practices. These anthropogenic pressures occur concurrently with naturally occurring environmental processes, and their combined influences can alter the structure of species assemblages across a region. Spatial variability in the demersal assemblages in the Celtic Sea and western English Channel were examined in relation to the influence of abrasion (relating to trawling pressure from bottom-towed fishing gears) and natural hydrodynamic processes (using kinetic energy as a measure of bed shear stress) using canonical correspondence analysis. Kinetic energy graduated from low levels in the western part of the study area to higher levels in the east, whilst trawling pressure varied at smaller spatial scales largely focussed on fishing grounds. Species assemblages were correlated with kinetic energy, with some species of commercial value being more strongly associated with areas subject to increased trawling pressure. However, the species assemblages at similar stages along this gradient of kinetic energy differed between ICES Divisions within the study area. Due to these regional differences, any management measures that may result in the re-distribution of fishing pressure should consider the potential impact on those assemblages (and associated species) that may then be subject to increased fishing disturbance.

Water column nutrient concentrations are related to excretion by benthic invertebrates in Lake Taihu, China

Internal release of nutrients is an important contributor to the nutrient dynamics in shallow eutrophic lakes. Zoobenthic organisms may contribute to this release by excreting nutrients to the overlaying water. Based on experiments and using results from previous experimental studies as well as field monitoring density data from 2007 to 2017, we calculated the annual and seasonal nutrient excretions of the two most common macroinvertebrates (Corbicula fluminea and Limnodrilus hoffmeisteri) in Lake Taihu, China. We compared these rates with the concentrations of NH4–N, total nitrogen (TN), PO4–P and total phosphorus (TP) in the lake water as well as with previous results of release rates from undisturbed sediments collected in the lake. The spatial distribution of nutrient excretion by the two invertebrate species varied markedly among sites and years. Regression analyses revealed significant relationships between total nutrient excretions by these two species and the concentrations of NH4–N, TN, PO4–P and TP in the lake, but with seasonal differences. The relationship was overall strongest in winter, followed by spring, and weakest in summer and autumn. The flux of NH4–N and PO4–P released by the two macroinvertebrate species were equivalent to as much as 50% and 66%, respectively, of the sediment release recorded in lab experiments under undisturbed conditions; however, the percentages would be somewhat lower under field conditions where the sediment is subjected to frequent wind-induced resuspension and fish disturbance, enhancing the release rates. The release declined during the study period due to a reduction in the density of macroinvertebrates, perhaps indicating increasing stocking of fish since 2007. Our results indicate that benthic invertebrates are important contributor to the internal loading in shallow eutrophic lakes.

Effects of benthivorous fish disturbance and snail herbivory on water quality and two submersed macrophytes

Benthivorous fish disturbance and snail herbivory are two important factors that determine the community structure of submersed macrophytes. We conducted an outdoor mesocosm experiment to examine the separate and combined effects of these two factors on water quality and the growth of two mixed-cultivation submersed macrophytes, Vallisneria natans and Hydrilla verticillata, with different growth forms. The experiment involved two levels of fish (Misgurnus anguillicaudatus) disturbance crossed with two levels of snail (Radix swinhoei) intensity. The results revealed that fish activity rather than snail activity significantly increased the overlying water concentrations of total suspended solids (TSS), total nitrogen (TN), ammonia nitrogen (N-NH4), total phosphorus (TP) and phosphate phosphorus (P-PO4). However, no differences among treatments were observed for chlorophyll a (chl a) concentrations. Fish disturbance or snail herbivory alone did not affect the relative growth rate (RGR) of H. verticillata, but their combined effects significantly decreased the RGR of H. verticillata. Although snail herbivory alone did not affect the RGR of V. natans, fish disturbance alone and the combined effects of these factors drastically reduced its RGR. Both species exhibited increased free amino acid (FAA) contents and decreased ramet numbers, soluble carbohydrate (SC) contents and starch contents in the presence of the fish. Moreover, compared to H. verticillata, V. natans showed exceedingly low ramet numbers and starch contents in the presence of the fish. H. verticillata had a higher RGR and summed dominance ratio (SDR2) than V. natans in all treatments; H. verticillata also displayed a larger competitive advantage in the presence of fish disturbance. The present study suggests that (1) fish disturbance rather than snail activity increases water nutrient concentrations, (2) low snail density may be harmful to submersed macrophyte growth when the plants are under other abiotic stress conditions and (3) the competitive advantage of H. verticillata over V. natans is more preponderant in a turbid environment.

Effects of benthivorous fish disturbance on chlorophyll a contents in water and the growth of two submersed macrophytes with different growth forms under two light regimes

Low underwater light availability and benthivorous fish-mediated disturbance are two important factors that influence the growth of submersed macrophytes. However, the combined effects of these factors remain unclear. To determine the combined effects of low light and fish-mediated disturbance on the growth of two submersed macrophytes with contrasting growth forms, i.e., Vallisneria natans and Hydrilla verticillata, we conducted an outdoor mesocosm experiment with a two-by-two factorial design. The experiment involved two fish-mediated disturbance levels (0 and 1 Misgurnus anguillicaudatus) crossed with two levels of light intensity (ambient light and a low-light environment created by culturing the macrophytes under a shelter). The results showed that the chlorophyll a (chl a) concentration in the overlying water showed no difference among treatments for each macrophyte species. The fish-mediated disturbance significantly decreased the relative growth rate (RGR) of both species in the low-light environment but showed no effects in the ambient light environment. Low light availability and/or fish-mediated disturbance led to increased plant heights of both species compared with the heights under the ambient light regime. Low light availability combined with fish-mediated disturbance significantly reduced the ramet number and soluble carbohydrate (SC) content of both species; however, the free amino acid (FAA) content was not affected. Compared to V. natans, H. verticillata exhibited a high RGR and high ramet numbers in a low-light environment combined with fish-mediated disturbance. Our results indicated that the adaptability of H. verticillata is better than that of V. natans in turbid, shallow and hydrostatic water. Fish-mediated disturbance can negatively influence submersed macrophyte recovery in lakes when light is not abundant.

Osmoregulatory disturbance in Neotropical fish exposed to the crude extracts of the cyanobacterium, Radiocystis fernandoi

Blooms of cyanobacteria, a common event in eutrophic environments, result in the release of potentially toxic substances into the water. The cyanobacterium Radiocystis fernandoi produces microcystin (MC) and other peptides that may disturb homeostasis. This study evaluated the effect of intraperitoneal injections containing the crude extract (CE) of R. fernandoi strain R28 on the gills and kidneys of neotropical fish, Piaractus mesopotamicus, 3, 6 and 24 h post-injection. CE contained MC-RR, MC-YR and minor other oligopeptides. Plasma ions and the activities of the enzymes PP1 and PP2A, Na+/K+-ATPase (NKA), H+-ATPase (HA) and carbonic anhydrase (CA) were determined and morphological changes in both the gills and kidneys were characterized. Compared to controls, the concentration of Na+ within the plasma of P. mesopotamicus decreased after treatment with CE 3 h post treatment and increased after 24 h; the concentration of K+ decreased after 6 h. The activity of the endogenous PP1 and PP2A was unchanged in the gills and was inhibited in the kidneys 6 h after i.p. injection. In the gills, NKA activity increased after 3 h and decreased 6 h post i.p. exposure. Further, NKA activity did not differ from the controls 24-h post injection. In the kidneys, NKA, HA and CA activities were unaffected by treatment. The mitochondria-rich cell (MRC) density in the gills decreased after 3 h in the filament and 3 and 6 h in the lamellae and was restored to the control levels 24 h post-exposure. Filament epithelial hyperplasia and hypertrophy, lamellar atrophy and rupture of the lamellar epithelium were the most common effects of treatment in the gills. No histopathological changes occurred in the kidneys. This study demonstrates that a single dose of toxic CE from R. fernandoi can cause a transitory ion imbalance in P. mesopotamicus which is related to the changes in MRC levels and NKA activity. Ionic balance was recovered 24 h post i.p. injection, however, morphological changes that occurred in the gills took a longer amount of time to return to normal. To conclude, the effects of components contained within the CE of R. fernandoi may be harmful to P. mesopotamicus. In particular, the recovery of ionic regulation depends on MRC responses and histopathological changes produced by CE may affect gas exchange and other gill functions.

Comparative thyroid disruption by o,p’-DDT and p,p’-DDE in zebrafish embryos/larvae

1,1-Trichloro-2-(p-chlorophenyl)-2-(o-chlorophenyl) ethane (o,p'-DDT) and 1,1-dichloro-2,2-bis (p-chlorophenyl)-ethylene (p,p′-DDE) cause thyroid disruption, but the underlying mechanisms of these disturbances in fish remain unclear. To explore the potential mechanisms of thyroid dysfunction caused by o,p'-DDT and p,p′-DDE, thyroid hormone and gene expression levels in the hypothalamic-pituitary-thyroid (HPT) axis were measured, and the developmental toxicity were recorded in zebrafish larvae. Zebrafish embryos/larvae were exposed to o,p'-DDT (0, 0.28, 2.8, and 28 nM; or 0, 0.1, 1, and 10 μg/L) and p,p′-DDE (0, 1.57, 15.7, and 157 nM; or 0, 0.5, 5, and 50 μg/L) for 7 days. The genes related to thyroid hormone synthesis (crh, tshβ, tg, nis and tpo) and thyroid development (nkx2.1 and pax8) were up-regulated in both the o,p'-DDT and p,p′-DDE exposure groups. Zebrafish embryos/larvae exposed to o,p'-DDT showed significantly increased total whole-body T4 and T3 levels, with the expression of ugt1ab and dio3 being significantly down-regulated. However, the p,p′-DDE exposure groups showed significantly lowered whole-body total T4 and T3 levels, which were associated with up-regulation and down-regulation expression of the expression of dio2 and ugt1ab, respectively. Interestingly, the ratio of T3 to T4 was significantly decreased in the o,p'-DDT (28 nM) and p,p′-DDE (157 nM) exposure groups, suggesting an impairment of thyroid function. In addition, reduced survival rates and body lengths and increased malformation rates were recorded after treatment with either o,p'-DDT or p,p′-DDE. In summary, our study indicates that the disruption of thyroid states was different in response to o,p'-DDT and p,p′-DDE exposure in zebrafish larvae.

EFFECT OF ADDITIONAL ACUTE IRRADIATION ON CYTOMORPHOLOGICAL ABNORMALITIES OF ERYTHROCYTES OF THE PRUSSIAN CARP (CARASSIUS GIBELIO BLOCH) FROM WATER BODY CONTAMINATED WITH RADIONUCLIDES.

Assessment of the effect of additional acute irradiation (AAI) in sub-lethal range on the peculiarities of formation of qualitative composition of red blood and adaptive possibilities of the hematopoietic system of fish in reservoirs within the Chernobyl Exclusion Zone (CEZ), contaminated with radionuclides. We studied the Prussian carp Carassius gibelio Bloch (2-3 years old) from Vershyna Lake (impacted reservoir in the CEZ) and Dibrova Lake (reference reservoir), where the average absorbed dose rate (ADR) was, respectively, 110.80 and 0.07 μGy/h. The fish were exposed by a single X-ray dose at the unit RUM-17 (ADR - 0.89 Gy/min) at dose of 2.5, 5.0 and 10.0 Gy. Morphological and cytogenetic studies of red blood cells were per- formed dynamically for the 1st, 7th and 30th day after irradiation. The blood was taken from the tail vein and stained by Pappenheim's method. Cytomorphological abnormalities of erythrocytes were analyzed for 3000 cells (‰). In blood of fish from the impacted reservoir (Vershyna Lake) on the 1st day after AAI, the average number of all types of deformations of erythrocytes cells increased in 2.1 times, and in fish of the reference reservoir (Dibrova Lake) - in 5.2 times. General spectrum of erythrocyte disturbances in fish of Vershyna Lake has increased from 4 to 6 types (in 1.5 times), and Dibrova Lake - from 2 to 5 types (in 2.5 times). However, further observations of the dynamics of morphological disorders of fish's blood cells from Vershyna Lake on the 7th and the 30th day after AAI showed a significant increase in pathological processes in comparison with the reference reservoir, namely - an increase in the number of gross damage of DNA molecules - amitosis (on average in 14.8 times), erythrocytes with septum in the nucleus (in 1.9 times), as well as structural disorders in the cells - protuberances (in 10.5 times), cells with vacuolate cytoplasm (in 8.6 times). The red blood cells of the fish of the impacted reservoir show a greater vulnerability to AAI, which manifests itself in an increase in the number of erythrocytes with pathology of mitosis and may indicate a violation of the genetic structures of cells due to long-term radiation exposure.

Propagation of Endangered Moapa Dace

We report successful captive spawning and rearing of the highly endangered Moapa Dace, Moapa coriacea (approximately 650 individual fish in existence at time of this study). We simulated conditions under which this stream-dwelling southern Nevada cyprinid and similar species spawned and reared in the wild by varying temperature, photoperiod, flow, and substrate in 14 different spawning and rearing treatments in a propagation facility. Successful spawning occurred in artificial streams with the following characteristics: water flow directed both across the bottom gravel substrate into a cobble bed and across the upper water column; 12–14 fish/stream (0.016–0.026 fish/L depending on water level); static water temperature of 30–32°C; photoperiod of 12 h light and 12 h dark; gradual replacement of water from their natal stream with on-site well water; a combination of pelleted, frozen and live food; and minimal disturbance of fish. Nevada Department of Wildlife now uses these techniques successfully to produce fish in a culture setting. Identification of the effective combination of factors to trigger spawning in exceptionally rare fishes can be difficult and time consuming, and limiting factors can be subtle. Sufficient numbers of available test fish, close study and replication of wild spawning conditions, careful documentation, and patience to identify subtle limiting factors are often required to effectively rear and spawn fishes not previously propagated.

Biogeochemistry of Cadmium: Anthropogenic Dispersion, Bioaccumulation, and Ecotoxicity

The article considers biogeochemical features of cadmium as one of the most dangerous elements. Data on its concentrations in waters of small lakes in the European Russia (from the tundra to deserts) and large river systems (Volga, Severnaya Dvina, Pechora) are given. It is shown that, despite the relatively low concentrations of the element in waters, its enrichment factor is hundreds and thousands of units, especially in the northern regions and regions subjected to the influence of non-ferrous metallurgy. Data are presented on the bioaccumulation of cadmium within fish body systems, which is determined by the concentration of the element in waters, as well as by the water pH and the calcium content. It is proved that the highest Cd concentrations are accumulated in kidneys and liver of whitefish and salmon, causing pathological disturbances. Data are reported on the accumulation of cadmium in kidneys and liver of human population of the industrially developed Northern region under impacts of copper–nickel smelters. The similarity in tendencies of the Cd accumulation and pathological disturbances in fish and the population consuming water from contaminated sources makes it possible to recommend fish as a bioindicator of the environmental pollution by cadmium.

Transchem project – Part I: Impact of long-term exposure to pendimethalin on the health status of rainbow trout (Oncorhynchus mykiss L.) genitors

Pendimethalin is a herbicide active substance commonly used in terrestrial agricultural systems and is thus detected at high concentrations in the surface water of several European countries. Previous studies reported several histopathological changes, enzymatic antioxidant modulation and immunity disturbance in fish exposed to this pesticide. The objective of this work was to investigate the direct effects of long-term exposure to environmental concentrations of pendimethalin over a period of 18 months in rainbow trout (Oncorhynchus mykiss) genitors. To do so, an experimental system consisting of eight similar 400 L tanks with a flow-through of fresh river water was used to perform daily chemical contamination. Fish were exposed to 850 ng/L for one hour and the pendimethalin concentration was then gradually diluted during the day to maintain optimal conditions for the fish throughout the experiment and to achieve a mean theoretical exposure level of around 100 ng L−1 per day. Every November, males and females were stripped to collect eggs and sperm and two new first generations of offspring were obtained. Kinetic sampling revealed differences in immune system parameters and antioxidative defences in the contaminated trout compared to the controls, due to pesticide exposure combined with seasonal changes related to gamete maturation. Moreover, reproductive capacity was significantly affected by exposure to the herbicide; a time lag of more than five weeks was observed for egg maturation in contaminated females and high bioconcentrations of pendimethalin were measured in eggs and sperm. Chemical transfer from genitors to offspring via gametes may affect embryo development and negatively impact the early stages of development.

Tissue Metabolism, Hematotoxicity, and Hepatotoxicity of Trichlorfon in Carassius auratus gibelio After a Single Oral Administration.

Trichlorfon is a most widely used organophosphate insecticide in aquaculture, many successful results have been reported for bath treatments of trichlorfon to control parasites. However, immersion treatments of large stocks with trichlorfon has caused serious environmental pollution. In contrast, oral administration treatment has advantages on reducing environmental pollution and having little effect in non-targeted species. The aim of this study was to investigate the effect of trichlorfon on Carassius auratus gibelio physiology after a single oral administration. In this study, Carassius auratus gibelio was subjected to oral gavage with various concentrations of trichlorfon (0.5 g/kg, 1 g/kg, and 2 g/kg). The trichlorfon concentration in the plasma and liver tissue was quantified using liquid chromatography-tandem mass spectrometry at different time points. At the beginning of oral exposure, the uptake of trichlorfon in the plasma and liver tissue was fast, and trichlorfon was rapidly eliminated to a low level within 24 h. In addition, acetylcholinesterase, superoxide dismutase, catalase, and glutathione-S-transferase activities in the plasma and liver tissue changed significantly after trichlorfon exposure. Additionally, vacuolar degeneration, necrosis, and congestion of the central vein were observed in the liver after trichlorfon exposure, as assessed by hematoxylin and eosin staining. Our results suggested that trichlorfon could accumulate and induce hematotoxicity and hepatotoxicity in the plasma and liver tissue, the toxicity induced by trichlorfon might result in physiological disturbances in fish.

Spatial data analysis for the marine fisheries and habitat management of Sri Lanka

Satellite Remote Sensing (RS) can be effectively used for the fisheries applications, including stock assessment, management of marine resources and fish harvesting. Further, there is an extensive range of fisheries related applications of RS data, including identifying marine managed areas, detection of harmful algal blooms, bycatch reduction, long term monitoring of fisheries related habitat changes and control of illegal fishing. Applications on RS related to marine fisheries sector in Sri Lanka, seem to be meager. Limited studies have been conducted on the fisheries related ecosystem damage assessment using RS after December 2004 Tsunami disaster. To fulfill the gaps of research on coastal fisheries identified, the author conducted some research on habitat changes such as monitoring of land use changes and water quality at economically important estuarine environments around Sri Lanka using multi temporal satellite imageries. In these studies, several environmental issues have been addressed such as localized eutrophication, disturbance of water circulations and sudden fish kills etc. Furthermore, since satellite RS is a useful tool that could be applied for planning marine fisheries development in Sri Lanka, the National Aquatic Resources Research and Development Agency (NARA) is currently conducting forecasting of fishing ground using satellite data for off-shore/ high seas fishery, providing accurate information on large pelagic fishing grounds considering sea surface temperature and chlorophyll distribution. As illegal, Unreported and Unregulated (IUU) fishing is a serious threat to the long-term economic and environmental sustainability of Sri Lankan oceans, RS techniques exhibit great potential for supporting to develop fisheries monitoring system around Sri Lankan waters which is timely important for control IUU fishing. VIIRS Boat Detection system of NOAA and Global Fishing Watch were discussed as the possible systems that can support the future monitoring and management of Sri Lankan marine fisheries sector. This paper summarizes the present RS related applications to the marine fishery sector of Sri Lanka. Further, it also provides guidelines for sustainable management of the sector that can result from RS, and identify existing applications which can effectively support the marine fishery management of the country.

Mediation of nitrogen by post-disturbance shelf communities experiencing organic matter enrichment

Microbes and benthic macro-invertebrates interact in sediments to play a major role in the biogeochemical cycling of organic matter, but the extent to which their contributions are modified following natural and anthropogenic changes has received little attention. Here, we investigate how nitrogen transformations, ascertained from changes in archaeal and bacterial N-cycling microbes and water macronutrient concentrations ([NH4–N], [NO2–N], [NO3–N]), in sand and sandy mud sediments differ when macrofaunal communities that have previously experienced contrasting levels of chronic fishing disturbance are exposed to organic matter enrichment. We find that differences in macrofaunal community structure related to differences in fishing activity affect the capacity of the macrofauna to mediate microbial nitrogen cycling in sand, but not in sandy mud environments. Whilst we found no evidence for a change in ammonia oxidiser community structure, we did find an increase in archaeal and bacterial denitrifier (AnirKa, nirS) and anammox (hzo) transcripts in macrofaunal communities characterized by higher ratios of suspension to deposit feeders, and a lower density but higher biomass of sediment-reworking fauna. Our findings suggest that nitrogen transformation in shelf sandy sediments is dependent on the stimulation of specific nitrogen cycling pathways that are associated with differences in the composition and context-dependent expression of the functional traits that belong to the resident bioturbating macrofauna community.

Bioconcentration, metabolism, and biomarker responses in marine medaka (Oryzias melastigma) exposed to sulfamethazine

The antibiotic sulfamethazine (SM2) is commonly used in agriculture and livestock for its broad-spectrum antibacterial properties. Due to its widespread application, SM2 is frequently detected in surface water and sediments. The objective of this study was to investigate the bioconcentration, distribution and biomarker responses of SM2 and its main metabolite, acetylated sulfamethazine (N-SM2) in medaka (Oryzias melastigma). Two treated groups of medaka were exposed to concentrations of 40μg/L and 200μg/L of SM2 for 24h to simulate the habitual use of those antibiotics in aquiculture activities. SM2 and its main metabolite, N-SM2, were measured in several tissues during the 24h uptake period by UPLC/MS/MS. The bile exhibited the highest SM2 concentration followed by the liver, gonad, gills, and muscle and the bioconcenration factor (BCF) was 10.69–42.95 in female fish and 2.78–145.36 in male fish. N-SM2 showed a different distribution pattern from the parent compound, accumulating mainly in the gonad, and its BCF was much higher in the male group. Gender-related differences were also observed in the bioconcentration, transform rate and biomarkers of SM2. Biomarkers (SOD, CAT) in the liver changed significantly after 2, 12, and 24h of exposure (P<0.05), and presented a double-peak phenomenon. These results indicated that SM2 can be absorbed and metabolized through multiple routes by fish in a short time. Interactions between biological systems and SM2 or its metabolites may induce biochemical disturbances in fish.

Release of neuropeptides from a neuro-cutaneous co-culture model: A novel in vitro model for studying sensory effects of ciguatoxins

Ciguatoxins are the major toxins responsible for ciguatera fish poisoning, a disease dominated by muco-cutaneous sensory disorders including paresthesiae, cold dysesthesia and pruritus. While the ciguatoxins are well known to target voltage-gated sodium channels (VGSCs), the ensuing molecular mechanisms underlying these sensory disorders remain poorly understood. In this study, we propose a primary sensory neuron-keratinocyte co-culture as an appropriate model to study the neuro-cutaneous effects of ciguatoxins. Using this model, we show for the first time that nanomolar concentrations of Pacific ciguatoxin-2 (P-CTX-2) induced a VGSC-dependent release of substance P (SP) and calcitonin gene-related peptide (CGRP). As these neuropeptides are known mediators of pain and itch sensations, the ciguatoxin-induced sensory disturbances in ciguatera fish poisoning may involve the release of these neuropeptides. We further determined time- and P-CTX-2 concentration-dependence of the release of SP and CGRP from the co-culture model. Moreover, we highlighted the influence of extracellular calcium on the release of neuropeptides elicited by P-CTX-2. These findings underline the usefulness of this novel in vitro model for studying the cellular and molecular mechanisms of the neuro-cutaneous effects of ciguatoxins, which may assist with identifying potential therapeutics for ciguatera fish poisoning.

Assessing functional redundancy in chronically trawled benthic communities

Fishing disturbance on ecosystems leads to changes in community structure and composition, which may have drastic implications for ecosystem functional performance. Functional redundancy, defined as species sharing similar functional roles, is a community property that plays an important role in preventing functional changes in ecosystems under pressure. In this study, we suggest that functional redundancy may be achieved through trait abundance (i.e. large amounts of a trait, hereafter “common traits”), or through trait richness (i.e. large numbers of distinct taxa exhibiting the same trait, hereafter “widespread traits”). We assessed the variability of both measures obtained from epifaunal and infaunal communities in soft-bottom trawling grounds. Sampling sites were located in four Mediterranean areas that were subjected to different levels of trawling effort. Common and widespread traits measures were based on the analysis of biological traits linked to key soft-bottoms functions such as nutrient cycling, bentho-pelagic coupling and habitat provision. The role of rare species in both measures was also assessed and we observed that, in our study sites, rare species generally exhibited the same traits as the most abundant species. Common and widespread traits measures provided complementary information on benthic functional redundancy. Thus, we suggest that a combination of the two measures should be used to appropriately assess benthic functional redundancy in trawling grounds. As redundancy is a component of ecosystem resilience, functional redundancy evaluation is important to assess the overall integrity of ecosystems.

Natural vs. fishing disturbance: drivers of community composition on traditional king scallop, Pecten maximus, fishing grounds

Abstract Scallop dredging is considered to be one of the most damaging forms of fishing to benthic habitats, although these effects vary among different habitats. The present study characterizes the biological communities that occur within the spatial limits of the English Channel king scallop dredge fishery in relation to key environmental drivers [mean seabed temperature; seabed temperature range; interannual temperature variation; bed shear stress (BSS); substrate characteristics; and depth] and across a gradient of scallop dredging intensity derived from vessel monitoring system data. Dredge fishing intensity was not correlated with species richness, species diversity, or species composition. However, increasing tidal BSS had a significant negative correlation with species richness and diversity. This outcome indicates that it is not possible to demonstrate that there is an effect of scallop fishing within the current spatial limits of the king scallop dredge fishery. This may be because historical dredge fishing could have already altered the benthic communities within the area of the scallop fishery to those that are resilient to scallop dredging, or that fishing disturbance has no impact over and above natural physical disturbance within the fishery. An analysis of biological and life history traits revealed that there was no relationship between recent fishing intensity, or BSS, and the functional composition of the communities present. However, even the lowest BSS values in the present study could be considered relatively high compared with areas outside the spatial boundaries of the fishery. Two distinct habitat groups were identified, based on the environmental drivers. These two groups were largely characterized by depth: deep (western) and shallow (eastern) sites. Species with traits that increase resilience to physical disturbance were abundant across all sample sites. Management concerning the environmental impacts of the fishery is discussed in terms of the spatial footprint of the fishery and predicted recovery time-scales for the associated benthic communities.