Typical Freshwater Research Articles

Divergence in Alewife Alosa pseudoharengus (Actinopterygii, Clupeidae), life history alters parasite communities

The Alewife, Alosa pseudoharengus, presently has two distinct life history variants, the anadromous ancestral type, and a derived landlocked freshwater type. In accordance with their variation in life history, landlocked Alewives have evolved dissimilar morphologies and ecological traits relative to the anadromous type, and as a result, their functional roles within ecosystems have changed. This study tests the prediction that hosts with an altered life history and ecosystem residency, like the landlocked Alewives would have lower rates of parasitism, which would result in a lower diversity and abundance of macroparasites compared to the anadromous variant. We compared parasite species richness and abundance between landlocked (collected from a lake in New Jersey) and anadromous Alewives (collected from river and ocean environments). The landlocked Alewives were infected with only 2 parasite species and overall parasite abundance was low in this population, while the anadromous Alewives harbored 7 parasite species, which formed distinct communities depending on host stage. Overall, this study suggests there was a loss of native parasites within landlocked Alewives and supports the idea that these populations of Alewives experience lower parasite pressure than their anadromous conspecifics.

Cultivation of native fish in Mexico: cases of success

AbstractAquaculture practice in Mexico is commonly carried out with some freshwater species, which are introduced in the region for its production, with technology developed in other countries. The growth of this activity has been slow, sometimes leading to loss of investments due to difficulties in the implementation of foreign technological packages, poor selection and inadequate management of the species, or farming sites, and even confusing legal procedures. Mexico stands out for the development of crops of exotic species more than native species, of which most are freshwater type. There are thirty‐four recorded species of freshwater fish, six of them are native and twenty‐eight are introduced species. The success of cultivating native species lies mainly in the process of selecting species with potential and certain characteristics. Mariculture is relatively new in Mexico; it has been intensibly developed, mostly in the north‐west of the country. It has a great potential due to the high commercial value of its species, excellent quality and demand in the market. Ornamental aquaculture is the most developed in Mexico; the main producer is the state of Morelos, with total technological expertise in production of introduced and native species. It should be noted that this success has been achieved, in some cases, with the support of projects from government institutions, universities, research centres, associations and private companies. Pointing out that the common factor for a successful aquaculture practice is an ecosystemic and sustainable approach, continuously improving practices and fish farming management, while complying with regulatory standards.

Transcriptome analysis of the typical freshwater rhodophytes Sheathia arcuata grown under different light intensities.

The Rhodophyta Sheathia arcuata is exclusively distributed in freshwater, constituting an important component in freshwater flora. This study presents the first transcriptome profiling of freshwater Rhodophyta taxa. A total of 161,483 assembled transcripts were identified, annotated and classified into different biological categories and pathways based on BLAST against diverse databases. Different gene expression patterns were caused principally by different irradiances considering the similar water conditions of the sampling site when the specimens were collected. Comparison results of gene expression levels under different irradiances revealed that photosynthesis-related pathways significantly up-regulated under the weak light. Molecular responses for improved photosynthetic activity include the transcripts corresponding to antenna proteins (LHCA1 and LHCA4), photosynthetic apparatus proteins (PSBU, PETB, PETC, PETH and beta and gamma subunits of ATPase) and metabolic enzymes in the carbon fixation. Along with photosynthesis, other metabolic activities were also regulated to optimize the growing and development of S. arcuata under appropriate sunlight. Protein-protein interactive networks revealed the most responsive up-expressed transcripts were ribosomal proteins. The de-novo transcriptome assembly of S. arcuata provides a foundation for further investigation on the molecular mechanism of photosynthesis and environmental adaption for freshwater Rhodophyta.

Particle size distribution mathematical models and properties of suspended solids in a typical freshwater pond

Many countries, such as China, today are facing the scarcity and pollution issues of freshwater resources. Suspended solids, as wastewater contaminants, may contain components such as nitrogen, phosphorus, heavy metals and pathogens that are harmful to the environment and human health, it is essential to know the size distribution regularity of the solids with a view to guiding the management of freshwater resources for sustainability. Particle size distribution (PSD) mathematical models and properties of suspended solids in a typical freshwater pond were investigated in this study. Particle size was measured using a laser particle size analyzer (measurement range: 0.01–3500 μm). The power law model and the variable-β model were tested for their ability to fit the numeric distribution of suspended solids; Gaussian (i.e., normal) distribution and log-normal distribution models were used to evaluate the volumetric distribution of suspended solids. The results showed that: by number, about 80% of the particles contributed to only 10% of total particle volume, while the remaining 20% contributed about 90% of the total volume. For numeric distribution, the variable–β model (R2 = 0.975 ± 0.011) was better than the power law model (R2 = 0.899 ± 0.033); for the volumetric distribution, the log-normal distribution model (R2 = 0.968 ± 0.020) clearly outperformed the Gaussian distribution model (R2 = 0.655 ± 0.093). Overall, the variable–β model and log-normal distribution were shown to accurately describe the numerical and volumetric distribution of pond water suspended solids, respectively. PSD model parameters can be related to some compositions in the wastewater and can provide guidance for suspended solids further treatment, be it physical, biological, chemical or synthetic methods.

Comparison of pathogen-derived ‘total risk’ with indicator-based correlations for recreational (swimming) exposure

Typical recreational water risk to swimmers is assessed using epidemiologically derived correlations by means of fecal indicator bacteria (FIB). It has been documented that concentrations of FIB do not necessarily correlate well with protozoa and viral pathogens, which pose an actual threat of illness and thus sometimes may not adequately assess the overall microbial risks from water resources. Many of the known pathogens have dose-response relationships; however, measuring water quality for all possible pathogens is impossible. In consideration of a typical freshwater receiving secondarily treated effluent, we investigated the level of consistency between the indicator-derived correlations and the sum of risks from six reference pathogens using a quantitative microbial risk assessment (QMRA) approach. Enterococci and E. coli were selected as the benchmark FIBs, and norovirus, human adenovirus (HAdV), Campylobacter jejuni, Salmonella enterica, Cryptosporidium spp., and Giardia spp. were selected as the reference pathogens. Microbial decay rates in freshwater and uncertainties in exposure relationships were considered in developing our analysis. Based on our exploratory assessment, the total risk was found within the range of risk estimated by the indicator organisms, with viral pathogens as dominant risk agents, followed by protozoan and bacterial pathogens. The risk evaluated in this study captured the likelihood of gastrointestinal illnesses only, and did not address the overall health risk potential of recreational waters with respect to other disease endpoints. Since other highly infectious pathogens like hepatitis A and Legionella spp. were not included in our analysis, these estimates should be interpreted with caution.

Spatial analysis of groundwater quality using self-organizing maps

Hydrochemical data of groundwater samples collected from thirty-five wells in alluvial aquifer of El Milia were examined using Self-Organizing Map (SOM) approach. Based on visualization of SOM-analysis and hydrochemical characteristics, groundwater samples were clustered into three clusters, which revealed three basic representative water types: freshwater (cluster 1), moderate salinity (cluster 2), and high salinity (cluster 3). Based on ionic ratio, the source of soluble ions in the groundwater of the freshwater types was found to be the carbonate rock dissolution, while evaporation and evapotranspiration were found to be the main factors affecting the chemistry of the groundwater characterized by the moderate and high salinity types, respectively. This study shows that the SOM approach can be successfully used to classify and characterize the groundwater in terms of quality.

Dissolved organic matter signatures vary between naturally acidic, circumneutral and groundwater-fed freshwaters in Australia

Dissolved organic matter (DOM) plays important roles in both abiotic and biotic processes within aquatic ecosystems, and these in turn depend on the quality of the DOM. We collected and characterized chromophoric DOM (CDOM) from different Australian freshwater types (circumneutral, naturally acidic and groundwater-fed waterways), climatic regions and seasons. CDOM quality was characterized using absorbance and fluorescence spectroscopy. Excitation emission scans followed by parallel factor (PARAFAC) analysis showed that CDOM was characterized by three main components: protein-like, fulvic-like and humic-like components commonly associated with various waters globally in the Openfluor database. Principal component analysis showed that CDOM quality varied between naturally acidic, circumneutral and groundwater-fed waters, with unique CDOM quality signatures shown for each freshwater type. CDOM quality also differed significantly within some sites between seasons. Clear differences in dominant CDOM components were shown between freshwater types. Naturally acidic waters were dominated by highly aromatic (as indicated by the specific absorbance co-efficient (SAC340) and the specific UV absorbance (SUVA254) values which ranged between 31 and 50 cm2 mg−1 and 3.9–5.7 mg C−1 m−1 respectively), humic-like CDOM of high molecular weight (as indicated by abs254/365 which ranged from 3.8 to 4.3). In contrast, circumneutral waters were dominated by fulvic-like CDOM of lower aromaticity (SAC340: 7–21 cm2 mg−1 and SUVA254: 1.5–3.0 mg C−1 m−1) and lower molecular weight (abs254/365 5.1–9.3). The groundwater-fed site had a higher abundance of protein-like CDOM, which was the least aromatic (SAC340: 2–5 cm2 mg−1 and SUVA254: 0.58–1.1 mg C−1 m−1). CDOM was generally less aromatic, of a lower molecular weight and more autochthonous in nature during the summer/autumn sampling compared to winter/spring. Significant relationships were shown between various CDOM quality parameters and pH. This is the first study to show that different freshwater types (circumneutral, naturally acidic and groundwater-fed) contain distinct CDOM quality signatures in Australia, a continent with unique flora and geology.

Ecostructuring of marine nematode communities by submarine groundwater discharge

Inputs of submarine groundwater discharge (SGD) to the coastal ocean may alter local and regional-scale biology. Here, we report on nematode assemblages along the north shore of Long Island, NY. We test if nematode communities differed between sites impacted by mixed fresh-saline SGD and where SGD is exclusively saline. Diversity of nematodes was low at sites impacted by fresh SGD and communities were dominated by a few opportunistic genera. Moreover, a set of typical freshwater nematode genera restricted to impacted sites was observed. Their presence in the marine coastal zone is exceptional and underlines the structuring role that fresh SGD plays in the local ecosystem. Saline SGD structured nematode assemblages differently compared to sites impacted by fresh SGD. The number of nematode genera was markedly higher at saline SGD sites, with a different community structure. This study highlights the importance to which inputs of fresh SGD may have on local ecosystem diversity in marine coastal environments.

Benthic fauna and communities of the lagoon water bodies of the White Sea by the example of Lake Kislo-Sladkoe

In the present research the investigation of the lake Kislo-Sladkoe, a small brackish lagoon on the coast of Kandalakshsky Gulf of the White Sea, was conducted. In total 21 species of macrobenthic invertebrates identified and seven types of macrobenthic communities, derived from marine, estuarial and freshwater types, descried. Also, six meiobenthic species of the order Harpacticoida were found. The ecological peculiarities of the macro and meiobenthic taxa and the comparison with the biota of other brackish waters of the White Sea coast are described.

Strong impact of anthropogenic contamination on the co-occurrence patterns of a riverine microbial community.

Although the health of rivers is threatened by multiple anthropogenic stressors with increasing frequency, it remains an open question how riverine microbial communities respond to emerging micropollutants. Here, by using 16S rDNA amplicon sequencing of 60 water samples collected during different hydrological seasons, we investigated the spatio-temporal variation and the co-occurrence patterns of microbial communities in the anthropogenically impacted Jiulong River in China. The results indicated that the riverine microbial co-occurrence network had a nonrandom, modular structure, which was mainly shaped by the taxonomic relatedness of co-occurring species. Fecal indicator bacteria may survive for prolonged periods of time in river water, but they formed an independent module which had fewer interactions with typical freshwater bacteria. Multivariate analysis demonstrated that nutrients and micropollutants [i.e., pharmaceuticals and personal care products (PPCPs)] exerted combined effects in shaping α- and β-diversity of riverine microbial communities. Remarkably, we showed that a hitherto unrecognized disruptive effect of PPCPs on the abundance variations of central species and module communities was stronger than the influence of physicochemical factors, suggesting the key role played by micropollutants for the microbial co-occurrence relationships in lotic ecosystems. Overall, our findings provide novel insights into community assembly in aquatic environments experiencing anthropogenic stresses.

Seasonal variations in bacterioplankton community structures in two small rivers in the Himi region of central Japan and their relationships with environmental factors.

The aim of this study was to improve our understanding of seasonal variations and the effects of physicochemical conditions on the bacterioplankton communities in two small rivers, the Moo and Nakayachi Rivers in the Himi region of central Japan. These rivers are inhabited by unionid freshwater mussels, which are used for oviposition by the endangered Itasenpara bitterling (Acheilognathus longipinnis). Water samples were collected every month between March 2011 and February 2012. Changes in bacterioplankton community structures were analysed using an approach that did not require cultivating the bacteria and involved PCR and denaturing gradient gel electrophoresis. The bacterioplankton community structures in the two rivers were similar in all seasons except winter. The bacterial sequences identified were dominated by typical freshwater Actinobacteria, Bacteroidetes, Cyanobacteria, α-Proteobacteria, and β-Proteobacteria bacterioplankton. Many β-Proteobacteria species were detected in all seasons, but Bacteroidetes species were dominant in the winter. The bacterioplankton community structures were affected by biochemical oxygen demand, chemical oxygen demand, chlorophyll-a concentration, water depth, and water temperature. These results provide a foundation for a more detailed understanding of the conditions that provide a suitable unionid habitat.

Co-existence of freshwater and marine T4-like myoviruses in a typical subtropical estuary.

Viruses are the most abundant biological entities on Earth and play an important role in microbial community dynamics and biogeochemical cycling, yet their ecological characteristics in estuarine ecosystems are unclear. Here, virioplankton communities in a typical subtropical estuary, the Jiulong River estuary (JRE) in China, were investigated. The abundance of virioplankton ranged from 1.01 ± 0.05 × 107 to 1.62 ± 0.09 × 107 particles mL-1 in JRE, and the population size of viruses was correlated with temperature and nutrient levels. Three tailed viral morphotypes (myovirus, siphovirus and podovirus) were observed. Phylogenetic analysis showed that most of the g23 sequences in the JRE fell into three previously established groups (Marine, Paddy and Lake Groups) and two potential Estuary Groups. This demonstrates the co-existence of typical freshwater and marine T4-like myoviruses in the estuarine ecosystem, suggesting the movement of viruses and their hosts among biomes. Additionally, the spatial variation of g23 sequences suggests a geographic distribution pattern of T4-like myoviruses in the JRE, which might be shaped by the environmental gradient and/or their host distribution. These results provide valuable insights into the abundance, diversity and distribution patterns of virioplankton, as well as the factors influencing them, in subtropical estuarine ecosystems.

Rhodopsin gene copies in Japanese eel originated in a teleost-specific genome duplication

BackgroundGene duplication is considered important to increasing the genetic diversity in animals. In fish, visual pigment genes are often independently duplicated, and the evolutionary significance of such duplications has long been of interest. Eels have two rhodopsin genes (rho), one of which (freshwater type, fw-rho) functions in freshwater and the other (deep-sea type, ds-rho) in marine environments. Hence, switching of rho expression in retinal cells is tightly linked with eels’ unique life cycle, in which they migrate from rivers or lakes to the sea. These rho genes are apparently paralogous, but the timing of their duplication is unclear due to the deep-branching phylogeny. The aim of the present study is to elucidate the evolutionary origin of the two rho copies in eels using comparative genomics methods.ResultsIn the present study, we sequenced the genome of Japanese eel Anguilla japonica and reconstructed two regions containing rho by de novo assembly. We found a single corresponding region in a non-teleostean primitive ray-finned fish (spotted gar) and two regions in a primitive teleost (Asian arowana). The order of ds-rho and the neighboring genes was highly conserved among the three species. With respect to fw-rho, which was lost in Asian arowana, the neighboring genes were also syntenic between Japanese eel and Asian arowana. In particular, the pattern of gene losses in ds-rho and fw-rho regions was the same as that in Asian arowana, and no discrepancy was found in any of the teleost genomes examined. Phylogenetic analysis supports mutual monophyly of these two teleostean synteny groups, which correspond to the ds-rho and fw-rho regions.ConclusionsSyntenic and phylogenetic analyses suggest that the duplication of rhodopsin gene in Japanese eel predated the divergence of eel (Elopomorpha) and arowana (Osteoglossomorpha). Thus, based on the principle of parsimony, it is most likely that the rhodopsin paralogs were generated through a whole genome duplication in the ancestor of teleosts, and have remained till the present in eels with distinct functional roles. Our result indicates, for the first time, that teleost-specific genome duplication may have contributed to a gene innovation involved in eel-specific migratory life cycle.

The Limnohabitans Genus Harbors Generalistic and Opportunistic Subtypes: Evidence from Spatiotemporal Succession in a Canyon-Shaped Reservoir.

We studied the diversity of Limnohabitans using reverse line blot hybridization with Limnohabitans lineage-specific probes in the freshwater canyon-shaped Římov reservoir (Czech Republic). To examine the succession of distinct lineages, we performed (i) a study of an intensive spring sampling program at the lacustrine part of the Římov reservoir (from ice melt through a phytoplankton peak to the clear-water phase), and (ii) a seasonal study (April to November) when the occurrence of distinct Limnohabitans lineages was related to the inherent longitudinal heterogeneity of the reservoir. Significant spatiotemporal changes in the compositions of distinct Limnohabitans lineages allowed for the identification of "generalists" that were always present throughout the whole season as well as "specialists" that appeared in the reservoir only for limited periods of time or irregularly. Our results indicate that some phytoplankton groups, such as cryptophytes or cyanobacteria, and zooplankton composition were the major factors modulating the distribution and dynamics of distinct Limnohabitans lineages. The highest Limnohabitans diversity was observed during the spring algal bloom, whereas the lowest was during the summer cyanobacterial bloom. The microdiversity also markedly increased upstream in the reservoir, being highest at the inflow, and thus likely reflecting strong influences of the watershed.IMPORTANCE The genus Limnohabitans is a typical freshwater bacterioplankton and is believed to play a significant role in inland freshwater habitats. This work is unique in detecting and tracing different closely related lineages of this bacterial genus in its natural conditions using the semiquantitative reverse line blot hybridization method and in discovering the factors influencing the microdiversity, subtype alternations, and seasonality.

Biodegradation of triclosan in diatom Navicula sp.: Kinetics, transformation products, toxicity evaluation and the effects of pH and potassium permanganate

Triclosan (TCS) is one of the most widely used pharmaceutically active compounds and frequently detected in treated wastewater and the impacted aquatic environment. However, the fate and toxicity of TCS in aquatic organisms is poorly known, including in particular the potential for the formation of incomplete biological transformation products. In this study, TCS posed high toxic effects (e.g., growth inhibition and damage of photosynthesis) to typical freshwater diatom Navicula sp., with the 24h and 72h EC50 values of 173.3 and 145.6μgL−1, respectively. The bioaccumulation of TCS in diatom cells increased with the increasing exposure to TCS and showed to be time-dependent. The higher intracellular TCS lead to higher toxicity on Navicula sp. The intracellular TCS concentration and the growth inhibition of TCS in Navicula sp. at pH 7.5 was obviously higher than that at pH 8.3, which was likely due to the higher abundance of unionized TCS in the culture. KMnO4 reduced both bioaccumulation and toxicity of TCS in Navicula sp., especially at pH 8.3. A total of seven products were detected by liquid chromatography-tandem mass spectrometry (LC–MS/MS). These findings will provide a reference for the risk assessment of TCS in aquatic environment.

Three classes of steroids in typical freshwater aquaculture farms: Comparison to marine aquaculture farms

This study provides a comprehensive analysis of the occurrence of androgens, glucocorticoids and progestogens in typical freshwater aquaculture farms in comparison with marine aquaculture farms. The results showed that more steroids were detected in the marine aquaculture farms. For all aquatic products, the total concentrations of steroids in fish muscle were 22–2000ng/g, which were much higher than those detected in crabs, shrimps or mollusks (0.5–8.1ng/g). Based on the hazard index of the selected steroids, most water samples were in the low or medium risks. Some banned steroids were identified in the freshwater shrimps and all marine products, indicating that there may be certain health risks by the consumption of these aquatic products in the studied aquaculture farms. Furthermore, the total contributions of steroids in China were estimated to be 2300kg/y and 1200kg/y from freshwater fish culture and shrimp-crab culture, respectively.

Investigation of Oil Potential in Saline Lacustrine Shale: A Case Study of the Middle Permian Pingdiquan Shale (Lucaogou Equivalent) in the Junggar Basin, Northwest China

The Pingdiquan shale (Lucaogou equivalent) is a typical saline lacustrine deposit in China and is one of the most significant petroleum source strata for the oil and natural gas fields in the Junggar Basin in northwestern China, which is widely acknowledged to have a large shale hydrocarbon potential. This article characterizes the Pingdiquan shale in the eastern Junggar Basin from the geochemical and geological perspectives, describes its oil potential, and compares the results with those from freshwater lacustrine shales. The Pingdiquan shale is highly heterogeneous in its mineral composition, with a big variation in each composition compared to that of freshwater lacustrine shales. The Pingdiquan shale can generally be classified into clastic shale and dolomite shale, where the clastic shale is distributed across the eastern Junggar Basin and thins from north to south, whereas the dolomite shale is developed only in the Jimusaer Sag and at the foot of the Kelameili Mountains. The Pingdiquan shale (both the clastic shale and dolomite shale) has a good petroleum potential and primarily consists of types II and III organic matter with thermal maturity ranging from early to late mature. The oil content (S1) of clastic shale and dolomite shale ranges from 0.01 to 4.96 mg/g and 0.02 to 3.23 mg/g, respectively. The oil content and oil saturation index (OSI) of the Pingdiquan shale reach a maximum value at the early to peak mature zone (Tmax of 445–450 °C). Similar trends can be observed in some typical freshwater lacustrine shales. In the Pingdiquan Formation, the dolomite shale has a higher total organic carbon content and genetic potential (S1 + S2) than the clastic shale; however, its oil content and OSI are lower than those of the clastic shale, as is its production index (PI). The results of one-dimensional basin modeling show that the dolomite shale and clastic shale have had almost the same petroleum transformation ratio values throughout geological history. However, the permeability of dolomite shale is orders of magnitude larger, which allows for more petroleum to be expelled from source rocks. In addition, positive correlations between specific surface areas and OSI and clay content are observed, indicating that high clay content also assists in maintaining the petroleum within the rocks. Therefore, less oil can be retained within dolomite shale than in clastic shale.

Organic geochemistry and palynology of coals and coal-bearing mangrove sediments of the Neogene Sandakan Formation, Northeast Sabah, Malaysia

The coals and coal-bearing mangrove sediments of Sandakan Formation have been evaluated for their source rock potential, paleoredox conditions and source of organic input, as well as the age and paleovegetation distribution using geochemical and petrographical methods. The studied samples were generally rich in organic carbon, which varied from 0.60 (massive mudstone) to 62.37wt% (coal). The studied samples have vitrinite reflectance (Ro) ranging from 0.31 to 0.49% and Tmax values ranging from 353 to 436°C indicating an immature to very early mature stage for hydrocarbon generation. The sediments were dominated by Type III kerogen, with some Type II/III kerogen, suggesting a significant land plant contribution to the organic matter. The bimodal distribution displayed by gas chromatogram, with a clear odd/even carbon number and skewed to higher molecular weight carbon (nC31), indicating a transitional depositional environment. The variation in pristane/phytane ratio, varied from 0.71 to 2.97, suggesting an alternating anoxic and oxic deposition conditions. The presence of marine dinoflagellate cyst in the mangrove and offshore mudstones were consistent with the relatively higher sulphur content in the studied samples which indicate marine inundations.Palynomorph recovered in this study, with abundant mangrove and freshwater types of pollen, suggesting a biogeographical distribution of ancient mangrove vegetation that expanded landward into the freshwater peat swamp setting and hinterland. The presence of marker species, viz. Florschuetzia levipoli, F. meridionalis and F. semilobata delineated an Early Miocene to Middle Miocene age for the Sandakan sediments.

Origin and evolutionary history of freshwater Rhodophyta: further insights based on phylogenomic evidence

Freshwater representatives of Rhodophyta were sampled and the complete chloroplast and mitochondrial genomes were determined. Characteristics of the chloroplast and mitochondrial genomes were analyzed and phylogenetic relationship of marine and freshwater Rhodophyta were reconstructed based on the organelle genomes. The freshwater member Compsopogon caeruleus was determined for the largest chloroplast genome among multicellular Rhodophyta up to now. Expansion and subsequent reduction of both the genome size and GC content were observed in the Rhodophyta except for the freshwater Compsopogon caeruleus. It was inferred that the freshwater members of Rhodophyta occurred through diverse origins based on evidence of genome size, GC-content, phylogenomic analysis and divergence time estimation. The freshwater species Compsopogon caeruleus and Hildenbrandia rivularis originated and evolved independently at the inland water, whereas the Bangia atropurpurea, Batrachospermum arcuatum and Thorea hispida are derived from the marine relatives. The typical freshwater representatives Thoreales and Batrachospermales are probably derived from the marine relative Palmaria palmata at approximately 415–484 MYA. The origin and evolutionary history of freshwater Rhodophyta needs to be testified with more organelle genome sequences and wider global sampling.

Steroid bioaccumulation profiles in typical freshwater aquaculture environments of South China and their human health risks via fish consumption

More attention was previously paid to adverse effects of steroids on aquatic organisms and their ecological risks to the aquatic environment. So far, little information has been reported on the bioaccumulative characteristics of different classes of steroids in cultured fish tissues. The present study for the first time provided a comprehensive analysis of the occurrence, bioaccumulation, and global consumers’ health risks via fish consumption of androgens, glucocorticoids and progestanges in typical freshwater cultured farms in South China. The numbers and total concentrations of steroids detected in the tissues of five common species of the cultured fish were in the order of plasma > bile > liver > muscle and plasma > bile, muscle > liver, respectively. The field bioaccumulation factors for the detected synthetic steroids ranged from 450 to 97,000 in bile, 450 to 65,000 in plasma, 2900 to 16,000 in liver, and 42 to 2600 in muscle of fish, respectively. This data suggests that steroids are bioaccumulative in fish tissues. Mostly important, 4-androstene-3,17-dione (AED) and cortisone (CRN) were found to be reliable chemical indicators to predict the levels of steroids in plasma and muscle of the inter-species cultured fish, respectively. Furthermore, the maximum hazard quotients (HQs) of testosterone and progesterone were 5.8 × 10−4 and 9.9 × 10−5, suggesting that human health risks were negligible via ingestion of the steroids-contaminated fish.