ResearchPad - Aquatic Science https://www.researchpad.co Default RSS Feed en-us © 2020 Newgen KnowledgeWorks <![CDATA[Ecophysiological and morphological comparison of two populations of Chlainomonas sp. (Chlorophyta) causing red snow on ice-covered lakes in the High Tatras and Austrian Alps]]> https://www.researchpad.co/product?articleinfo=5b59797b463d7e5ce270da2f

Based on analyses of multiple molecular markers (18S rDNA, ITS1, ITS2 rDNA, rbcL), an alga that causes red snow on the melting ice cover of a high-alpine lake in the High Tatras (Slovakia) was shown to be identical with Chlainomonas sp. growing in a similar habitat in the Tyrolean Alps (Austria). Both populations consisted mostly of smooth-walled quadriflagellates. They occurred in slush, and shared similar photosynthetic performances (photoinhibition above 1300 µmol photons m–2 s–1), very high levels of polyunsaturated fatty acids (PUFA, 64% and 74% respectively) and abundant astaxanthin accumulation, comparable to the red spores of Chlamydomonas nivalis (Bauer) Wille. Physiological differences between the Slovak and Austrian populations included higher levels of α-tocopherol and a 13Z-isomer of astaxanthin in the former. High accumulation of secondary pigments in the Slovak population probably reflected harsher environmental conditions, since the collection was made later in the growing season when cells were exposed to higher irradiance at the surface. Using a polyphasic approach, we compared Chlainomonas sp. with Chlamydomonas nivalis. The latter causes ‘conventional’ red snow, and shows high photophysiological plasticity, with high efficiency under low irradiance and no photoinhibition up to 2000 µmol photons m–2 s–1. Its PUFA content was significantly lower (50%). An annual cycle of lake-to-snow colonization by Chlainomonas sp. from slush layers deeper in the ice cover is proposed. Our results point to an ecologically highly specialized cryoflora species, whose global distribution is likely to be more widespread than previously assumed.

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<![CDATA[In vivo cranial bone strain and bite force in the agamid lizard Uromastyx geyri]]> https://www.researchpad.co/product?articleinfo=5bbf08e740307c38ebdd5d99

In vivo bone strain data are the most direct evidence of deformation and strain regimes in the vertebrate cranium during feeding and can provide important insights into skull morphology. Strain data have been collected during feeding across a wide range of mammals; in contrast, in vivo cranial bone strain data have been collected from few sauropsid taxa. Here we present bone strain data recorded from the jugal of the herbivorous agamid lizard Uromastyx geyri along with simultaneously recorded bite force. Principal and shear strain magnitudes in Uromastyx geyri were lower than cranial bone strains recorded in Alligator mississippiensis, but higher than those reported from herbivorous mammals. Our results suggest that variations in principal strain orientations in the facial skeleton are largely due to differences in feeding behavior and bite location, whereas food type has little impact on strain orientations. Furthermore, mean principal strain orientations differ between male and female Uromastyx during feeding, potentially because of sexual dimorphism in skull morphology.

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<![CDATA[Sources of mycosporine-like amino acids in planktonic Chlorella-bearing ciliates (Ciliophora)]]> https://www.researchpad.co/product?articleinfo=5b7ce669463d7e2752211fe0

  1. Mycosporine-like amino acids (MAAs) are a family of secondary metabolites known to protect organisms exposed to solar UV radiation. We tested their distribution among several planktonic ciliates bearing Chlorella isolated from an oligo-mesotrophic lake in Tyrol, Austria. In order to test the origin of these compounds, the MAAs were assessed by high performance liquid chromatography in both the ciliates and their symbiotic algae.

  2. Considering all Chlorella-bearing ciliates, we found: (i) seven different MAAs (mycosporine-glycine, palythine, asterina-330, shinorine, porphyra-334, usujirene, palythene); (ii) one to several MAAs per species and (iii) qualitative and quantitative seasonal changes in the MAAs (e.g. in Pelagodileptus trachelioides). In all species tested, concentrations of MAAs were always <1% of ciliate dry weight.

  3. Several MAAs were also identified in the Chlorella isolated from the ciliates, thus providing initial evidence for their symbiotic origin. In Uroleptus sp., however, we found evidence for a dietary source of MAAs.

  4. Our results suggest that accumulation of MAAs in Chlorella-bearing ciliates represents an additional benefit of this symbiosis and an adaptation for survival in sunlit, UV-exposed waters.

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<![CDATA[Characterization of Promoter Activities of Four Different Japanese Flounder Promoters in Transgenic Zebrafish]]> https://www.researchpad.co/product?articleinfo=5b7af55e463d7e5e66b93aca

An important consideration in transgenic research is the choice of promoter for regulating the expression of a foreign gene. In this study several tissue-specific and inducible promoters derived from Japanese flounder Paralichthys olivaceus were identified, and their promoter activity was examined in transgenic zebrafish. The 5′ flanking regions of the Japanese flounder complement component C3, gelatinase B, keratin, and tumor necrosis factor (TNF) genes were linked to green fluorescence protein (GFP) as a reporter gene. The promoter regulatory constructs were introduced into fertilized zebrafish eggs. As a result we obtained several stable transgenic zebrafish that displayed green fluorescence in different tissues. Complement component C3 promoter regulated GFP expression in liver, and gelatinase B promoter regulated it in the pectoral fin and gills. Keratin promoter regulated GFP expression in skin and liver. TNF gene promoter regulated GFP expression in the pharynx and heart. TNF promoter had lipoplysaccharide-inducible activity, such that when transgenic embryos were immersed lipopolysaccharide, GFP expression increased in the epithelial tissues. These 4 promoters regulated the expression of GFP in different patterns in transgenic zebrafish.

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<![CDATA[Performance of National Maps of Watershed Integrity at Watershed Scales]]> https://www.researchpad.co/product?articleinfo=5b6db344463d7e5199b309cb

Watershed integrity, the capacity of a watershed to support and maintain ecological processes essential to the sustainability of services provided to society, can be influenced by a range of landscape and in-stream factors. Ecological response data from four intensively monitored case study watersheds exhibiting a range of environmental conditions and landscape characteristics across the United States were used to evaluate the performance of a national level Index of Watershed Integrity (IWI) at regional and local watershed scales. Using Pearson’s correlation coefficient (r), and Spearman’s rank correlation coefficient (rs), response variables displayed highly significant relationships and were significantly correlated with IWI and ICI (Index of Catchment Integrity) values at all watersheds. Nitrogen concentration and flux-related watershed response metrics exhibited significantly strong negative correlations across case study watersheds, with absolute correlations (|r|) ranging from 0.48 to 0.97 for IWI values, and 0.31 to 0.96 for ICI values. Nitrogen-stable isotope ratios measured in chironomids and periphyton from streams and benthic organic matter from lake sediments also demonstrated strong negative correlations with IWI values, with |r| ranging from 0.47 to 0.92, and 0.35 to 0.89 for correlations with ICI values. This evaluation of the performance of national watershed and catchment integrity metrics and their strong relationship with site level responses provides weight-of-evidence support for their use in state, local and regionally focused applications.

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<![CDATA[Best Practices for the Development, Scale-up, and Post-approval Change Control of IR and MR Dosage Forms in the Current Quality-by-Design Paradigm]]> https://www.researchpad.co/product?articleinfo=5ad516c1463d7e406f9d7540

In this whitepaper, the Manufacturing Technical Committee of the Product Quality Research Institute provides information on the common, best practices in use today in the development of high-quality chemistry, manufacturing and controls documentation. Important topics reviewed include International Conference on Harmonization, in vitroin vivo correlation considerations, quality-by-design approaches, process analytical technologies and current scale-up, and process control and validation practices. It is the hope and intent that this whitepaper will engender expanded dialog on this important subject by the pharmaceutical industry and its regulatory bodies.

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<![CDATA[Production of Homozygous Transgenic Rainbow Trout with Enhanced Disease Resistance]]> https://www.researchpad.co/product?articleinfo=5ad41325463d7e2e02d6221d

Previous studies conducted in our laboratory showed that transgenic medaka expressing cecropin B transgenes exhibited resistant characteristic to fish bacterial pathogens, Pseudomonas fluorescens and Vibrio anguillarum. To confirm whether antimicrobial peptide gene will also exhibit anti-bacterial and anti-viral characteristics in aquaculture important fish species, we produced transgenic rainbow trout expressing cecropin P1 or a synthetic cecropin B analog, CF-17, transgene by sperm-mediated gene transfer method. About 30 % of fish recovered from electroporation were shown to carry the transgene as determined by polymerase chain reaction (PCR) amplification assay. Positive P1 transgenic fish were crossed to non-transgenic fish to establish F1 transgenic founder families, and subsequently generating F2, and F3 progeny. Expression of cecropin P1 and CF-17 transgenes was detected in transgenic fish by reverse transcription (RT)-PCR analysis. The distribution of body sizes among F1 transgenic fish were not significantly different from those of non-transgenic fish. Results of challenge studies revealed that many families of F2 and F3 transgenic fish exhibited resistance to infection by Aeromonas salmonicida and infectious hematopoietic necrosis virus (IHNV). All-male homozygous cecropin P1 transgenic families were produced by androgenesis from sperm of F3 heterozygous transgenic fish in one generation. The resistant characteristic to A. salmonicida was confirmed in progeny derived from the outcross of all-male fish to non-transgenic females. Results of our current studies confirmed the possibility of producing disease-resistant homozygous rainbow trout strains by transgenesis of cecropin P1 or CF-17 gene and followed by androgenesis.

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<![CDATA[Effect on supplementation of Spirulina maxima enriched with Cu on production performance, metabolical and physiological parameters in fattening pigs]]> https://www.researchpad.co/product?articleinfo=5acd974e463d7e2fdb453f84

In this paper, the effect of addition of the biomass of Spirulina maxima enriched with copper (Sm-Cu) to the animal feed is discussed. The biomass was cultivated in the photobioreactor with the capacity of 10 m3. After the biosorption process, the enriched biomass was investigated as the source of valuable nutrients. The feeding experiment was conducted for 87 days. The study was performed in individual rearing pens, with controlled microclimate, feed and water were available semi-ad libitum. Piglets (24) were divided into two groups (control and experimental). The experimental group was fed with addition of the biomass of Sm-Cu instead of inorganic salts. There were no statistically significant differences between the average daily and periodic weight gain, daily and periodic feed collection, as well as feed conversion ratio. There were no statistically significant differences between the amount of N excreted in faeces and urine, when considering the retention of N, both in relation to the consumed N, and relative N digested which was at a similar level. In the experimental group in comparison to the control group, the lower low-density lipoprotein cholesterol by 17.05 % (P < 0.05) and total cholesterol by 9.43 % (P < 0.05) were observed. Additionally, the increase of parameter a* of 13 % (P < 0.05) and the reduction of the natural leakage by 34 % (P < 0.05) were found.

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<![CDATA[Heterologous ectoine production in Escherichia coli: By-passing the metabolic bottle-neck]]> https://www.researchpad.co/product?articleinfo=5989db3aab0ee8fa60bd494d

Transcription of the ectoine biosynthesis genes ectA, ectB and ectC from Marinococcus halophilus in recombinant Escherichia coli DH5α is probably initiated from three individual σ70A-dependent promoter sequences, upstream of each gene. Consequently, mRNA-fragments containing the single genes and combinations of the genes ectA and ectB or ectB and ectC, respectively, could be detected by Northern blot analysis. Under the control of its own regulatory promoter region (ectUp) a seemingly osmoregulated ectoine production was observed. In addition, aspartate kinases were identified as the main limiting factor for ectoine production in recombinant E. coli DH5α. Co-expression of the ectoine biosynthesis genes and of the gene of the feedback-resistant aspartate kinase from Corynebacterium glutamicum MH20-22B (lysC) led to markedly increased production of ectoine in E. coli DH5α, resulting in cytoplasmic ectoine concentrations comparable to those reached via ectoine accumulation from the medium.

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<![CDATA[Transcriptional responses to biologically relevant doses of UV-B radiation in the model archaeon, Halobacterium sp. NRC-1]]> https://www.researchpad.co/product?articleinfo=5989dac8ab0ee8fa60bb3557

Background

Most studies of the transcriptional response to UV radiation in living cells have used UV doses that are much higher than those encountered in the natural environment, and most focus on short-wave UV (UV-C) at 254 nm, a wavelength that never reaches the Earth's surface. We have studied the transcriptional response of the sunlight-tolerant model archaeon, Halobacterium sp. NRC-1, to low doses of mid-wave UV (UV-B) to assess its response to UV radiation that is likely to be more biologically relevant.

Results

Halobacterium NRC-1 cells were irradiated with UV-B at doses equivalent to 30 J/m2 and 5 J/m2 of UV-C. Transcriptional profiling showed that only 11 genes were up-regulated 1.5-fold or more by both UV-B doses. The most strongly up-regulated gene was radA1 (vng2473), the archaeal homologue of RAD51/recA recombinase. The others included arj1 (vng779) (recJ-like exonuclease), top6A (vng884) and top6B (vng885) (coding for Topoisomerase VI subunits), and nrdJ (vng1644) (which encodes a subunit of ribonucleotide reductase). We have found that four of the consistently UV-B up-regulated genes, radA1 (vng2473), vng17, top6B (vng885) and vng280, share a common 11-base pair motif in their promoter region, TTTCACTTTCA. Similar sequences were found in radA promoters in other halophilic archaea, as well as in the radA promoter of Methanospirillum hungatei. We analysed the transcriptional response of a repair-deficient ΔuvrA (vng2636) ΔuvrC (vng2381) double-deletion mutant and found common themes between it and the response in repair proficient cells.

Conclusion

Our results show a core set of genes is consistently up-regulated after exposure to UV-B light at low, biologically relevant doses. Eleven genes were up-regulated, in wild-type cells, after two UV-B doses (comparable to UV-C doses of 30 J/m2 and 5 J/m2), and only four genes were up-regulated by all doses of UV-B and UV-C that we have used in this work and previously. These results suggest that high doses of UV-C radiation do not necessarily provide a good model for the natural response to environmental UV. We have found an 11-base pair motif upstream of the TATA box in four of the UV-B up-regulated genes and suggest that this motif is the binding site for a transcriptional regulator involved in their response to UV damage in this model archaeon.

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<![CDATA[Acidophilic haloarchaeal strains are isolated from various solar salts]]> https://www.researchpad.co/product?articleinfo=5989d9e4ab0ee8fa60b6a876

Haloarchaeal strains require high concentrations of NaCl for their growth, with optimum concentrations of 10–30%. They display a wide variety of morphology and physiology including pH range for growth. Many strains grow at neutral to slightly alkaline pH, and some only at alkaline pH. However, no strain has been reported to grow only in acidic pH conditions within the family Halobacteriaceae.

In this study, we isolated many halophiles capable of growth in a 20% NaCl medium adjusted to pH 4.5 from 28 commercially available salts. They showed growth at pH 4.0 to 6.5, depending slightly on the magnesium content. The most acidophilic strain MH1-52-1 isolated from an imported solar salt (pH of saturated solution was 9.0) was non-pigmented and extremely halophilic. It was only capable of growing at pH 4.2–4.8 with an optimum at pH 4.4 in a medium with 0.1% magnesium chloride, and at pH 4.0–6.0 (optimum at pH 4.0) in a medium with 5.0% magnesium. The 16S rRNA and DNA-dependent RNA polymerase subunit B' gene sequences demonstrated clearly that the strain MH1-52-1 represents a new genus in the family Halobacteriaceae.

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<![CDATA[Effect of benthic boundary layer transport on the productivity of Mono Lake, California]]> https://www.researchpad.co/product?articleinfo=5989dacdab0ee8fa60bb4d94

The significance of the transport of nutrient-rich hypolimnetic water via the benthic boundary layer (BBL) to the productivity of Mono Lake was studied using a coupled hydrodynamic and ecological model validated against field data. The coupled model enabled us to differentiate between the role of biotic components and hydrodynamic forcing on the internal recycling of nutrients necessary to sustain primary productivity. A 4-year period (1991–1994) was simulated in which recycled nutrients from zooplankton excretion and bacterially-mediated mineralization exceeded sediment fluxes as the dominant source for primary productivity. Model outputs indicated that BBL transport was responsible for a 53% increase in the flux of hypolimnetic ammonium to the photic zone during stratification with an increase in primary production of 6% and secondary production of 5%. Although the estimated impact of BBL transport on the productivity of Mono Lake was not large, significant nutrient fluxes were simulated during periods when BBL transport was most active.

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<![CDATA[Unravelling the adaptation responses to osmotic and temperature stress in Chromohalobacter salexigens, a bacterium with broad salinity tolerance]]> https://www.researchpad.co/product?articleinfo=5989da02ab0ee8fa60b746cb

Chromohalobacter salexigens, a Gammaproteobacterium belonging to the family Halomonadaceae, shows a broad salinity range for growth. Osmoprotection is achieved by the accumulation of compatible solutes either by transport (betaine, choline) or synthesis (mainly ectoine and hydroxyectoine). Ectoines can play additional roles as nutrients and, in the case of hydroxyectoine, in thermotolerance. A supplementary solute, trehalose, not present in cells grown at 37°C, is accumulated at higher temperatures, suggesting its involvement in the response to heat stress. Trehalose is also accumulated at 37°C in ectoine-deficient mutants, indicating that ectoines suppress trehalose synthesis in the wild-type strain. The genes for ectoine (ectABC) and hydroxyectoine (ectD, ectE) production are arranged in three different clusters within the C. salexigens chromosome. In order to cope with changing environment, C. salexigens regulates its cytoplasmic pool of ectoines by a number of mechanisms that we have started to elucidate. This is a highly complex process because (i) hydroxyectoine can be synthesized by other enzymes different to EctD (ii) ectoines can be catabolized to serve as nutrients, (iii) the involvement of several transcriptional regulators (σS, σ32, Fur, EctR) and hence different signal transduction pathways, and (iv) the existence of post-trancriptional control mechanisms. In this review we summarize our present knowledge on the physiology and genetics of the processes allowing C. salexigens to cope with osmotic stress and high temperature, with emphasis on the transcriptional regulation.

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<![CDATA[Distribution, abundance and diversity of the extremely halophilic bacterium Salinibacter ruber]]> https://www.researchpad.co/product?articleinfo=5989dacdab0ee8fa60bb4d8a

Since its discovery in 1998, representatives of the extremely halophilic bacterium Salinibacter ruber have been found in many hypersaline environments across the world, including coastal and solar salterns and solar lakes. Here, we review the available information about the distribution, abundance and diversity of this member of the Bacteroidetes.

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<![CDATA[Diversity of picoeukaryotes at an oligotrophic site off the Northeastern Red Sea Coast]]> https://www.researchpad.co/product?articleinfo=5989da29ab0ee8fa60b81f74

Background

Picoeukaryotes are protists ≤ 3 μm composed of a wide diversity of taxonomic groups. They are an important constituent of the ocean’s microbiota and perform essential ecological roles in marine nutrient and carbon cycles. Despite their importance, the true extent of their diversity has only recently been uncovered by molecular surveys that resulted in the discovery of a substantial number of previously unknown groups. No study on picoeukaryote diversity has been conducted so far in the main Red Sea basin-a unique marine environment characterized by oligotrophic conditions, high levels of irradiance, high salinity and increased water temperature.

Results

We sampled surface waters off the coast of the northeastern Red Sea and analyzed the picoeukaryotic diversity using Sanger-based clone libraries of the 18S rRNA gene in order to produce high quality, nearly full-length sequences. The community captured by our approach was dominated by three main phyla, the alveolates, stramenopiles and chlorophytes; members of Radiolaria, Cercozoa and Haptophyta were also found, albeit in low abundances. Photosynthetic organisms were especially diverse and abundant in the sample, confirming the importance of picophytoplankton for primary production in the basin as well as indicating the existence of numerous ecological micro-niches for this trophic level in the upper euphotic zone. Heterotrophic organisms were mostly composed of the presumably parasitic Marine Alveolates (MALV) and the presumably bacterivorous Marine Stramenopiles (MAST) groups. A small number of sequences that did not cluster closely with known clades were also found, especially in the MALV-II group, some of which could potentially belong to novel clades.

Conclusions

This study provides the first snapshot of the picoeukaryotic diversity present in surface waters of the Red Sea, hence setting the stage for large-scale surveying and characterization of the eukaryotic diversity in the entire basin. Our results indicate that the picoeukaryotic community in the northern Red Sea, despite its unique physiochemical conditions (i.e. increased temperatures, increased salinity, and high UV irradiance) does not differ vastly from its counterparts in other oligotrophic marine habitats.

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<![CDATA[A commentary on the XIIIth International Rotifer Symposium (Shillong, 2012)]]> https://www.researchpad.co/product?articleinfo=5989db0fab0ee8fa60bcb86f

Rotifers have attracted the attention of biologists for well over 200 years. Interest in these exquisite animals rests in their diverse morphology, short generation time resulting in high growth rates, ability to withstand desiccation, and wide distribution, coupled with evidence of cryptic speciation. Moreover, three modes of reproduction are present in the phylum: obligatory sexuality, cyclical parthenogenesis, and obligatory ameiotic parthenogenesis. Thus, this phylum offers a rich field of study. Recognizing the need to share advances in knowledge, a triennial meeting, the International Rotifer Symposium (IRS), was begun in 1976. The most recent symposium (13th IRS) was held at Shillong (India) from 18–24, November 2012. In this commentary we considered the development of rotifer research as viewed through the lens of more than 35 years of IRS. Initially papers presented at the IRS focused on ecology, morphology, and pure taxonomic problems, with little applied work being reported. However, after more than three decades, the emphasis has swung to a balance of both basic (e.g., aging, ecology, genetics, and taxonomy) and applied (aquaculture and ecotoxicology) research.

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<![CDATA[Use of vital wheat gluten in aquaculture feeds]]> https://www.researchpad.co/product?articleinfo=5989d9daab0ee8fa60b67283

Summary

In aquaculture, when alternative protein sources of Fish Meal (FM) in diets are investigated, Plant Proteins (PP) can be used. Among them, Vital Wheat Gluten (VWG) is a proteinaceous material obtained from wheat after starch extraction. “It is mainly composed of two types of proteins, gliadins and glutenins, which confer specific visco-elasticity that’s to say ability to form a network providing suitable binding. This will lead to specific technological properties that are notably relevant to extruded feeds”. Besides these properties, VWG is a high-protein ingredient with an interesting amino-acid profile. Whereas it is rather low in lysine, it contains more sulfur amino acids than other PP sources and it is high in glutamine, which is known to improve gut health and modulate immunity. VWG is a protein source with one of the highest nitrogen digestibility due to a lack of protease inhibitor activity and to the lenient process used to make the product. By this way, addition of VWG in diet does not adversely affect growth performance in many fish species, even at a high level, and may secure high PP level diets that can induce health damages.

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<![CDATA[Identification of bacteria in enrichment cultures of sulfate reducers in the Cariaco Basin water column employing Denaturing Gradient Gel Electrophoresis of 16S ribosomal RNA gene fragments]]> https://www.researchpad.co/product?articleinfo=5989db09ab0ee8fa60bc9742

Background

The Cariaco Basin is characterized by pronounced and predictable vertical layering of microbial communities dominated by reduced sulfur species at and below the redox transition zone. Marine water samples were collected in May, 2005 and 2006, at the sampling stations A (10°30′ N, 64°40′ W), B (10°40′ N, 64°45′ W) and D (10°43’N, 64°32’W) from different depths, including surface, redox interface, and anoxic zones. In order to enrich for sulfate reducing bacteria (SRB), water samples were inoculated into anaerobic media amended with lactate or acetate as carbon source. To analyze the composition of enrichment cultures, we performed DNA extraction, PCR-DGGE, and sequencing of selected bands.

Results

DGGE results indicate that many bacterial genera were present that are associated with the sulfur cycle, including Desulfovibrio spp., as well as heterotrophs belonging to Vibrio, Enterobacter, Shewanella, Fusobacterium, Marinifilum, Mariniliabilia, and Spirochaeta. These bacterial populations are related to sulfur coupling and carbon cycles in an environment of variable redox conditions and oxygen availability.

Conclusions

In our studies, we found an association of SRB-like Desulfovibrio with Vibrio species and other genera that have a previously defined relevant role in sulfur transformation and coupling of carbon and sulfur cycles in an environment where there are variable redox conditions and oxygen availability. This study provides new information about microbial species that were culturable on media for SRB at anaerobic conditions at several locations and water depths in the Cariaco Basin.

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<![CDATA[Indo-Pacific bottlenose dolphin (Tursiops aduncus) habitat preference in a heterogeneous, urban, coastal environment]]> https://www.researchpad.co/product?articleinfo=5989d9f0ab0ee8fa60b6e498

Background

Limited information is available regarding the habitat preference of the Indo-Pacific bottlenose dolphin (Tursiops aduncus) in South Australian estuarine environments. The need to overcome this paucity of information is crucial for management and conservation initiatives. This preliminary study investigates the space-time patterns of habitat preference by the Indo-Pacific bottlenose dolphin in the Port Adelaide River-Barker Inlet estuary, a South Australian, urbanised, coastal environment. More specifically, the study aim was to identify a potential preference between bare sand substrate and seagrass beds, the two habitat types present in this environment, through the resighting frequency of recognisable individual dolphins.

Results

Photo-identification surveys covering the 118 km2 sanctuary area were conducted over 2 survey periods May to August 2006 and from March 2009 to February 2010. Sighting frequency of recognisable individual Indo-Pacific bottlenose dolphins established a significant preference for the bare sand habitat. More specifically, 72 and 18% of the individuals sighted at least on two occasions were observed in the bare sand and seagrass habitats respectively. This trend was consistently observed at both seasonal and annual scales, suggesting a consistency in the distinct use of these two habitats.

Conclusions

It is anticipated that these results will benefit the further development of management and conservation strategies.

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<![CDATA[Effects of flow restoration on mussel growth in a Wild and Scenic North American River]]> https://www.researchpad.co/product?articleinfo=5989dadaab0ee8fa60bb9967

Background

Freshwater mussels remain among the most imperiled species in North America due primarily to habitat loss or degradation. Understanding how mussels respond to habitat changes can improve conservation efforts. Mussels deposit rings in their shell in which age and growth information can be read, and thus used to evaluate how mussels respond to changes in habitat. However, discrepancies between methodological approaches to obtain life history information from growth rings has led to considerable uncertainty regarding the life history characteristics of many mussel species. In this study we compared two processing methods, internal and external ring examination, to obtain age and growth information of two populations of mussels in the St. Croix River, MN, and evaluated how mussel growth responded to changes in the operation of a hydroelectric dam.

Results

External ring counts consistently underestimated internal ring counts by 4 years. Despite this difference, internal and external growth patterns were consistent. In 2000, the hydroelectric dam switched from operating on a peaking schedule to run-of-the-river/partial peaking. Growth patterns between an upstream and downstream site of the dam were similar both before and after the change in operation. At the downstream site, however, older mussels had higher growth rates after the change in operation than the same sized mussels collected before the change.

Conclusions

Because growth patterns between internal and external processing methods were consistent, we suggest that external processing is an effective method to obtain growth information despite providing inaccurate age information. External processing is advantageous over internal processing due to its non-destructive nature. Applying this information to analyze the influence of the operation change in the hydroelectric dam, we suggest that changing to run-of-the-river/partial peaking operation has benefited the growth of older mussels below the dam.

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