Pyrosequencing reveals specific associations of bacterial clades Roseobacter and Flavobacterium with the harmful dinoflagellate Cochlodinium polykrikoides growing in culture

Harmful algal blooms of the dinoflagellate Cochlodinium polykrikoides are of worldwide environmental concern. Previous field studies have demonstrated the association of such algal blooms with free‐living bacteria (FLB) and particle‐associated bacteria (PAB). In the present study, we report evidence for bacterial association with C. polykrikoides in laboratory culture. Sampling was performed at different growth stages (lag, exponential and stationary) and pyrosequencing was used to identify taxa. As a result, the community structures of FLB and PAB were elucidated and significant differences between FLB and PAB were identified by hierarchical cluster analysis and the similarity profiles test (p = .05). The relative abundances of bacterial operational taxonomic units distinctly changed in response to the different phases of C. polykrikoides growth. The Roseobacter genus Marivita and the Flavobacterium genus Winogradskyella were dominant in the FLB and PAB associated with C. polykrikoides, respectively. The Roseobacter clade, which has also exhibited associations with C. polykrikoides blooms in field samples, may influence host cell growth through the provision of vitamins.     

Sea-surface microlayer toxicity off the Florida Keys

A survey of sea-surface microlayer (SSML) toxicity was initiated off the Florida Keys in early 1993. Ex situ toxicity tests, based on the development of the sea urchin, Lytechinus variegatus, demonstrated that 59.2% of SSML samples taken from visibly slicked areas (n=27) were toxic compared to collected subsurface water. A random subset of samples tested a second time using a fish early life-stage test with embryos from the spotted seatrout, Cynoscion nebulosus, confirmed the presence of the toxicant. Results from a partial toxicity identification evaluation (TIE) procedure indicated that an organic compound(s) containing a non-polar functional group was the primary determinant of toxicity in all of the SSML samples tested. While subsequent GC-MS analyses failed to identify a specific compound, they did tend to rule out common xenobiotics, such as organochlorine pesticides as potential toxicants. Preliminary tests, done by an outside laboratory, indicated that two of the most toxic SSML samples contained a brevetoxin, a biotoxin produced by Gymnodinium breve. This is the first report of natural toxins concentrating in the SSML; however, without a completed TIE, including a Phase III—toxicity confirmation procedure, the identification of any toxic agent remains speculative.     

Assessment of the consecutive harmful dinoflagellate blooms during 2015 in the Izmit Bay (the Marmara Sea)

A series of red tides were observed during 2015 in the Izmit Bay(the Marmara Sea) which is located in the most industrialized and populated region of Turkey. Six samplings were carried out in this area following the red tides.Nitrite-N, nitrate-N, ammonia, silica and orthophosphate concentrations were analyzed spectrophotometrically.Physicochemical conditions were measured by CTD probe. Plankton quantification was performed using counting chambers under microscopes. Prorocentrum micans was the most abundant species, except on May 14,2015, when Noctiluca scintillans was dominant. The abundance of P. micans reached average 18×10~6 ind./L on May 3, 2015 in the Karamürsel station, simultaneously with elevated levels of NH_3 and o-PO_4~(3–). The sample was also abundant in dead amphipods((72±12) ind./L) that had been covered by mucilage aggregates produced by P.micans. The highest biomass(calculated by carbon) was recorded as(268±26.0) mg/L on May 14 in the Hereke station. Beside the anthropogenic wastewater discharges, unknown sources and resuspensions caused increases in nutrient levels. After long term northeaster gusts(35 km/h for 5 d) an upwelling occurred on November 6, 2015 after wind-induced sediment resuspension. Although nutrient discharges remarkably decreased over 30 years through established wastewater treatment plants, harmful phytoplankton blooms still occur. Comparing the present results with other studies in nearby Mediterranean seas reveals that the most intense harmful dinoflagellate bloom in recent years occurred in the Izmit Bay. Therefore, additional protection measures necessary for a cleaner Izmit Bay. These incidents also demonstrate that contaminants, accumulated in sediment,may have long-lasting effects on enclosed marine ecosystems.     

Copper complexation by fulvic acid affects copper toxicity to the larvae of the polychaete Hydroides elegans

Copper toxicity is influenced by a variety of environmental factors including dissolved organic matter (DOM). We examined the complexation of copper by fulvic acid (FA), one of the major components of DOM, by measuring the decline in labile copper by anodic stripping voltammetrically (ASV). The data were described using a one-site ligand binding model, with a ligand concentration of 0.19micromol site mg(-1) C, and a logK' of 6.2. The model was used to predict labile copper concentration in a bioassay designed to quantify the extent to which Cu-FA complexation affected copper toxicity to the larvae of marine polychaete Hydroides elegans. The toxicity data, when expressed as labile copper concentration causing abnormal development, were independent of FA concentration and could be modeled as a logistic function, with a 48-h EC(50) of 58.9microgl(-1). However, when the data were expressed as a function of total copper concentration, the toxicity was dependent on FA concentration, with a 48-h EC(50) ranging from 55.6microgl(-1) in the no-FA control to 137.4microgl(-1) in the 20mgl(-1) FA treatment. Thus, FA was protective against copper toxicity to the larvae, and such an effect was caused by the reduction in labile copper due to Cu-FA complexation. Our results demonstrate the potential of ASV as a useful tool for predicting metal toxicity to the larvae in coastal environment where DOM plays an important role in complexing metal ions.     

Distinctiveness of the mesopelagic fish fauna in the Gulf of Mexico

We quantify the similarity of the Gulf of Mexico mesopelagic fish fauna to that in adjacent oceanic regions, the Venezuelan and Colombian Basins of the Caribbean Sea and the North and South Sargasso Seas. The South Sargasso and Colombian are the least similar of the areas in terms of their faunal composition, and the Venezuelan and Colombian Basins are the most similar. The Gulf fauna lies somewhere in between, and is a composite of that in the Sargasso and Caribbean Seas. The Gulf of Mexico displays the greatest abundance, biomass and richness (S=140 species), and is an intermediate in evenness (J=0.66) and percent endemism (7.1%). Our findings support the view that the centrally located Gulf is an oceanic ecotone between the Atlantic Tropical and Subtropical faunal regions.     

The expansion,limit and decline of the global marine fish catch

Catch of marine fish grew from after WW II–1989, at which point it stabilized. In 1996 it began to decline. It continues to decline now, at a time when earth's population is expected to reach 10 billion by 2050. Since the factors driving the increase are primarily the growth in income, population, technology of catching fish and ever increasing fishing effort, it is to be expected that the aggregate marine catch will continue to decline. This decline has important implications for marine ecosystems but primarily its importance relates to the human use of other global resources such as food, water and world's climate.     

Numerical simulation of the effects of fish behavior on flow dynamics around net cage

The computational fluid dynamics study is performed to analyze the impact of the cultured fish on the flow field through net cage and the deformation of net cage. The shear stress turbulent k-omega model is applied to simulate the flow field through the net cage, and the large deformation nonlinear structure model is adopted to conduct the structural analysis of the flexible net cage. To validate the net-fluid interaction model of the net cage in current, a series of physical model tests are conducted, which indicate that the numerical model can accurately simulate the flow field around the net cage and the deformation of the net cage. A fish model is used to simulate the effect of fish behavior on the flow pattern around the net cage and the deformation of the net cage. In addition, the flow fields around the net cage in current are investigated considering different fish group structures, fish swimming speeds, fish distributions and fish stocking densities. The results indicate that the circular movement of fish in the still water leads to a low pressure zone at the center of net cage, which causes a strong vertical flow along the center line of the net cage. The drag force on the net cage is significantly decreased with the increasing fish stocking density, but the most severe deformation of net cage occurred in the case of medium fish stocking density.     

Institutional and substantial uncertainty—Explaining the lack of adaptability in fish stocking policy

Adaptive management implies a system in which policy and practice are constantly revised in a continuous circular process to accommodate new ecological knowledge. In the case of current fish stocking practices, there is an evident gap between science and practice indicating a lack of adaptability. While fish stocking is perceived as a solution to many problems of modern fishery management, scientific researchers warn that current practices, including introducing alien populations, seriously threaten the sustainability of fish stocks. The aim of this study was to address, explain the existence of and, finally, discuss the prospect of narrowing this gap. For this purpose, the characteristics of the policy subsystem were analyzed. The empirical findings highlight the wickedness of the policy problem. The substantial and institutional uncertainties surrounding the issue are proposed as the main reasons for the deficits in adaptability. Fish stocking decisions are made within a complex policy subsystem that involves multiple actors and policy-making institutions, conflicting goals and competing notions of the problem. Cross-coalition learning—learning between coalitions of actors with different problem definitions, forming a joint view—is a necessary and, in the case of fish stocking, lacking variable in the adaptive management process.     

Dispersal patterns of the eggs and larvae of spring-spawning fish in the Irish Sea, UK

Many marine species produce pelagic propagules which, because of their life-history characteristics and the local hydrodynamics, can disperse considerable distances from the point of release. Distances travelled are affected by factors such as: release time and location, egg and larval stage duration, local environmental conditions and active swimming and settlement behaviours. Understanding such dispersal patterns is important for the design of effective ecosystem-conservation strategies. We used a regional scale, coupled physical-biological model for the Irish Sea to simulate the possible dispersal of eggs and larvae of five species of fish with contrasting early life histories (cod Gadus morhua, plaice Pleuronectes platessa, witch Glyptocephalus cynoglossus, sprat Sprattus sprattus and pogge Agonus cataphractus). The hydrodynamic model was forced with meteorological data for 1995, a year when extensive plankton surveys were conducted in the Irish Sea. A particle tracking method featuring particle release (spawning) and species-dependent particle development and behaviour was then run based on flow and temperature fields from the hydrodynamical model. Modelled larval distributions and settlement areas corresponded favourably with observations from field sampling. The settlement destinations (or onset of shoaling for sprat) were affected both by their initial spawning location and by the species-specific development rates and behaviours coded into the model. Eggs and larvae typically remained within 160 km of their spawning origin, although a minority travelled up to 300 km. Even in a relatively enclosed sea such as the Irish Sea, fish eggs and larvae can be dispersed over 100s of km. This provides a major challenge for the design of effective spatial management strategies if it is necessary to protect a species across its life-history stages. Further progress in the design of effective conservation measures for species or communities will need an integrated approach taking account of key aspects of early life history and behaviour.     

Spatial variability of the surf zone fish and macroinvertebrate community within dissipative sandy beaches in Oregon,USA

Habitat heterogeneity can influence biological communities by providing a diversity of areas that can be occupied by different species. Sandy beach surf zones are often considered homogenous environments; however, sand bars moved by currents and waves can produce trench‐like shapes or troughs that provide heterogeneity. The influence of habitat heterogeneity produced by sand movement is unclear despite the fact that surf zones are an important habitat for larval and juvenile fish and macrocrustaceans. To determine if, and how, the fish and macroinvertebrate communities present in trough and non‐trough or flat areas of Oregon surf zones differ, we compared species assemblages in both areas at three beaches adjacent to estuary mouths over 2 years. Troughs had different communities compared with flat areas, with higher total catch (mean ± SD = 123.2 ± 122.1 versus 43.6 ± 44.5 individuals × 100 m^?2) and taxon richness (6.7 ± 2.7 versus 4.0 ± 2.3 taxa); these differences were potentially due to water movement, prey availability and sediment size. The fish and macroinvertebrate communities did not vary between years but there were significant differences among beaches, with the most distinct community present at the only beach adjacent to an estuary without a jetty at its mouth, which was possibly due to higher species movement between the surf zones and estuary. Fish and macrocrustacean surf zone communities varied spatially within and among beaches in relation to habitat heterogeneity provided by sand movement and, potentially, the influence of adjacent habitats.     

Larval fish abundance and physical forcing in the Gulf of Alaska, 1981–2003

The present study investigates ecological patterns and relationships to environmental variables among a time-series of larval fish species abundance from late spring surveys (1981–2003) in the northwest Gulf of Alaska (GOA). Links between interannual variation in species abundance and the physical environment were explored using generalized additive modeling (GAM). Trends in larval abundance and connections with physical variables displayed patterns that indicate unique and complex responses among species to environmental forcing during the larval period. In particular, the observed patterns suggest that ontogenetic-specific responses, representing sub-intervals of early life, are important. In addition, a notable degree of synchrony in larval abundance trends, and similarity in links with physical variables, were observed among species with common early life history patterns. The deepwater spawners, northern lampfish, arrowtooth flounder, and Pacific halibut, were most abundant in the study area during the 1990s, in association with enhanced wind-driven onshore and alongshore transport. Years of high abundance for Pacific cod, walleye pollock, and northern rock sole were associated with cooler winters and enhanced alongshore winds during spring. High larval abundance for spring–summer spawning rockfish species and southern rock sole seemed to be favored by warmer spring temperatures later in the time-series. This apparent exposure–response coupling seems to be connected to both local-scale and basin-scale environmental signals, to varying degrees depending on specific early life history characteristics. Understanding such ecological connections contributes to the evaluation of vulnerability and resilience among GOA species’ early life history patterns to fluctuating climate and oceanographic conditions. This investigation also provides crucial information for the identification of “environmental indicators” that may have a broad-spectrum effect on multiple species early life history stages, as well as those that may be more species-specific in exerting control on early life history survival. Of particular interest was the emergence of the EP–NP (East Pacific–North Pacific) teleconnection index as the top-ranked variable in the GAM models exploring the connections between late spring larval abundance and the physical environment. The EP–NP index represents an important and often primary mode of spring–summer atmospheric variability in the northeast Pacific, with a strong expression in the GOA, and its connection with species in this study implies that it may be a climate mode of significant ecological importance.     

Genomic cloning and expression of vitellogenin gene from the self-fertilizing fish Rivulus marmoratus (Cyprinodontiformes, Rivulidae)

We cloned the vitellogenin gene from the self-fertilizing fish Rivulus marmoratus, and sequenced 12,326 bp. The number of exons of R. marmoratus and rainbow trout vitellogenin genes were different, and also the splicing junctions are different throughout most of the exons and introns but the amino acid similarity of R. marmoratus vitellogenin gene to other species was rather high. In promoter region of R. marmoratus vitellogenin gene, there were several E2 binding sites and the estrogen response element (ERE). We discuss here the gene structure and expression of R. marmoratus vitellogenin gene.     

LM神经网络在鱼类胚胎保存抗冻剂毒性试验设计中的应用

采用LM算法神经网络对鱼类胚胎冷冻保存抗冻剂毒性试验数据进行了分析,研究了孵化率和抗冻剂种类、浓度以及平衡时间等因素之间的对应关系,为鱼类胚胎冷冻保存的研究提供了新的分析手段,研究结果表明这一方法行之有效。     

Flow cytometry and pigment analyses as tools to investigate the toxicity of herbicides to natural phytoplankton communities

Characterisation of natural phytoplanktonic communities is currently being advanced through flow cytometry and high resolution pigment analyses. To date, toxicological methods to assess impacts of herbicides on natural phytoplankton populations are lacking. Here, we report the novel use of these techniques in combination to study changes in phytoplankton populations exposed to 2-methylthio-4-tertiary-butylamino-6-cyclopropylamino-s-triazine (Irgarol 1051), a herbicide used in antifouling paints. Flow cytometry results revealed that following a 72-h exposure to approximately 100 ngL(-1), eukaryote abundance was less than half that in the controls. High performance liquid chromatographic analyses of pigments demonstrated that 19'-hexanoyloxyfucoxanthin was selectively lost relative to the control. This carotenoid is specific to the prymnesiophytes which are key constituents of phytoplanktonic communities within temperate marine waters. Values of EC(50) (72 h) as low as 70 ngL(-1) were calculated from the selective reduction in this compound. Concentrations substantially exceeding this level have been reported in UK and other European coastal waters.     

Differential herbivory of invasive algae by native fish in the Mediterranean Sea

The potential role of generalist herbivores to serve as a source of biotic resistance against algal invasion in marine ecosystems has been poorly examined. The present study investigates the capacity of Mediterranean herbivorous fishes to consume three of the most invasive seaweeds of the Western Mediterranean (Caulerpa racemosa, Lophocladia lallemandii and Womersleyella setacea) and examines vertical and temporal variations of such consumption. Our results show that although fish feed throughout the depth gradient examined (5–35 m), they concentrate in shallow waters, and can consume high amounts of C. racemosa. Such high ingestion of C. racemosa does not appear to be random, since this alga is consistently chosen when offered in pairs with several native species. Conversely, L. lallemandii and W. setacea are barely eaten by fish even though they can be very abundant in the field throughout the year. Our results suggest that fish could be an important controlling agent that has been overlooked in temperate marine invasions, and they may be able to provide certain resistance to C. racemosa invasion. In contrast, they are unlikely to exert any important control effects on L. lallemandii or W. setacea.