The feeding relationship between copepods and phytoplankton has immense ecological significance. This study investigated the feeding behavior of copepods by studying the feeding selectivity of ...Paracalanus parvus, a key small copepod species, using a high-speed camera. The feeding behavior of P. parvus separately fed on three algae, Prorocentrum minimum, Alexandrium minutum, and Thalassiosira weissflogii, was studied at five different concentrations. The factors characterizing feeding behavior, including the beating frequency (BF), beating time (BT), and rejection behavior, were analyzed. The average BT and BF of P. parvus fed on toxic algae were significantly lower than those of copepods fed on nontoxic algae, indicating that the toxic algae negatively affected their feeding behavior. There were no significant differences in feed rejection among the three algae during the short period of experimentation, indicating that the rejection behavior was insignificant in the early period (within 20 min) of feeding on toxic algae. The feeding behavior was inhibited when the concentration reached 250 cells/mL. The BT was initially affected at increasing concentrations followed by the BF, and P. minimum and A. minutum reduced the BF at concentrations of 250 and 1000 cells/mL, respectively. Analysis of the average BFs revealed that P. parvus was more significantly affected by P. minimum containing diarrheal shellfish poison than by A. minutum containing paralytic shellfish poison. The BF of copepods fed on P. minimum was significantly lower than that of copepods fed on A. minutum at 250–500 cells/mL but was not significantly different from that at 1000 cells/mL. This indicated that the inhibitory effect of P. minimum on the feeding behavior was more significant at concentrations observed at the onset of red tide blooms (0.25–0.5 × 102 cells/mL), but insignificant at concentrations reaching those in advanced red tides (>103 cells/mL). This study demonstrates that toxic dinoflagellates alter the feeding behavior of copepods and describes the variations in their feeding response to different algal species and concentrations. The findings provide crucial insights for further studies on the feeding relationship between copepods and phytoplankton and on functional assessment of plankton ecosystems.
Display omitted
•The REY-rich sediments in the CIOB consist of phillipsite-bearing pelagic clay.•The REY in these sediments were captured by bioapatite and micronodule from seawater.•Driven by weak ...early diagenesis, the REY released to porewater from the micronodules.•The REY in porewater were also captured by the bioapatite.
Rare earth element and ytterbium (REY)-rich deep-sea sediments are recently discovered potential undersea rare earth element (REE) resources. Here, we present the results of the mineralogical and geochemical characterization of REY-rich sediments collected from the Central Indian Ocean Basin (CIOB). These data were used to provide a jigsaw puzzle for the investigation of REY transfer during early diagenesis and to discuss the formation mechanism of REY-rich sediments. The research results show that the REY-rich sediments distributed in the CIOB mainly consist of phillipsite-bearing pelagic clay and pelagic clay, and are characterized by enrichments in middle REEs (MREEs) and heavy REEs (HREEs), negative Ce anomalies and positive Y anomalies. The REY in these sediments are mainly captured dirtcely from overlying seawater by bioapatite and micronodules at the water-sediment interface. After burial, driven by the redox reaction between organic matter and an oxidizer (free O2 and Mn and Fe oxides), the REY-rich sediments experienced weak early diagenesis, and the REY released from hydrogenetic micronodules were captured by the bioapatite.
Lytic and lysogenic infections are the main strategies used by viruses to interact with microbial hosts. The genetic information of prophages provides insights into the nature of phages and their ...potential influences on hosts. Here, the siphovirus vB_MoxS-R1 was induced from a
strain isolated from an estuarine
culture. vB_MoxS-R1 has a high replication capability, with an estimated burst size of 2000 virions per cell. vB_MoxS-R1 represents a novel phage genus-based genomic analysis. Six transcriptional regulator (TR) genes were predicted in the vB_MoxS-R1 genome. Four of these TR genes are involved in stress responses, virulence and amino acid transportation in bacteria, suggesting that they may play roles in regulating the host cell metabolism in response to external environmental changes. A glycerophosphodiester phosphodiesterase gene related to phosphorus acquisition was also identified in the vB_MoxS-R1 genome. The presence of six TR genes and the phosphorus-acquisition gene suggests that prophage vB_MoxS-R1 has the potential to influence survival and adaptation of its host during lysogeny. Possession of four endonuclease genes in the prophage genome suggests that vB_MoxS-R1 is likely involved in DNA recombination or gene conversion and further influences host evolution.
Mercury (Hg), Lead (Pb) and its stable isotopes and polycyclic aromatic hydrocarbons (PAHs) were analyzed in a sediment box core obtained from the central Bohai Sea (BS) of northern China to trace ...anthropogenic input for the past century. The records of Hg, PAHs and Pb isotopic ratios revealed that the BS was clearly impacted by human activities from the early 1930s to the middle 1940s, possibly related to the acceleration of heavy industrialization in northeast China. Under rapid development and significant increase in fossil fuel consumption, pressure on the BS environment had obviously increased, as revealed by increasing concentrations of Hg, Pb, and PAHs from the early 1960s to late 1990s, with a synchronous decrease of 206Pb/207Pb isotopic ratios. The evolving trends in 206Pb/207Pb ratio, Hg, and PAHs were found to be decoupled since the early 2000s, possibly because of the significant improvement in environmental protection. Depositional records of Pb isotopic ratios with PAH compositions indicate a high-resolution sediment footprint of anthropogenic energy-consumption-based impacts around the BS over the past century, especially with the transformed emission sources from the leaded gasoline and combustion of coal before the 2000s to coal combustion and nonferrous metal smelting thereafter. The decreased records of sedimentary Pb have been widely found by around the world (e.g. North America, Southeast Asia and West Europe) after the ban on the leaded gasoline. However, this trend in China is reverse by the phasing out of leaded gasoline since the 2000s, possibly due to the recent accelerating development of nonferrous metal smelting and the continued increase in coal-dominated energy consumption.
•High-resolution sediment records of recent anthropogenic impacts in Bohai were obtained.•Impact of heavy industry in Northeast China during 1930s was firstly recorded in Bohai sediment.•Transformation of Pb emission sources from leaded gasoline to coal and metal smelting was recorded at the 2000s.•Coupled deposition records of Pb and PAHs could serve as a coastal sediment footprint of human impact.
Display omitted
•Fe-Mn (oxyhydr)oxides prefer to release LREE + MREE during initial stage of early diagenesis.•Biogenic apatite can inherit features of REY released from Fe-Mn ...(oxyhydr)oxides.•Gradual variations of element contents were found within the enameloid of fish tooth.•Substitution dominates the migration from Fe-Mn phases to biogenic apatites.
Biogenic apatite (fish teeth/bones) is considered the primary host mineral of rare earth elements and Y (REY) in deep-sea REY-rich sediments. Meanwhile, Fe-Mn (oxyhydr)oxides in the form of ferromanganese nodules and micronodules are also enriched in REY. Although studies have suggested that micronodules might release REY to pore water, eventually migrating into biogenic apatites during early diagenesis, robust evidence and mechanism for such migration remain elusive. Here, we present findings from a ferromanganese nodule with a fossil tooth nucleus discovered in surface sediments from the northwestern Pacific. Detailed geochemical characteristics of different parts of the ferromanganese nodule are provided, along with new analysis of modern shark teeth from the study area. The Fe-Mn (oxyhydr)oxides from the outer crust of the nodule are typically hydrogenetic, with lower Mn/Fe ratios (mean = 1.35, n = 33), in contrast to those filled in the tooth nucleus (mean Mn/Fe = 3.83, n = 20). Combined with compiled data on (micro)nodules and biogenic apatites in deep-sea sediments, we have identified the initial stage (Mn/Fe = 2.5 – 5) of early diagenesis of Fe-Mn (oxyhydr)oxides characterized by preferential release of light and middle rare earth elements (except Ce) compared to Fe-Mn (oxyhydr)oxides (micronodules) with higher degree of diagenesis. We demonstrated that biogenic apatites can inherit distinct fractionations of REY released from Fe-Mn (oxyhydr)oxides during different stages of diagenesis. Additionally, gradual elemental variations and substitutions of Sr2+ and Zn2+ by Na+ and REY3+ are observed in the enameloid of the fossil tooth, and substitution dominates the REY migration from Fe-Mn (oxyhydr)oxides to biogenic apatites. Thus, the studied nodule with directly contacting Fe-Mn (oxyhydr)oxides and biogenic apatite (enameloid), provides substantial evidence for potential element migration between Fe-Mn (oxyhydr)oxide and biogenic apatite and gives new insights into the mechanism for REY-enrichment in biogenic apatite.
Display omitted
•Viral lysis was stimulated by the sinking of particulate organic carbon.•Substantial transformation of microbial biomass into dissolved organic matter through viral ...lysis.•Heterogeneous viral impact on the production and utilization of dissolved organic matter.•Viral activity contributes to pools of labile and recalcitrant dissolved organic matter in aquatic environments.
Viruses saturate environments throughout the world and play key roles in microbial food webs, yet how viral activities affect dissolved organic matter (DOM) processing in natural environments remains elusive. We established a large-scale long-term macrocosm experiment to explore viral dynamics and their potential impacts on microbial mortality and DOM quantity and quality in starved and stratified ecosystems. High viral infection dynamics and the virus-induced cell lysis (6.23–64.68% d−1) was found in the starved seawater macrocosm, which contributed to a significant transformation of microbial biomass into DOM (0.72–5.32 μg L−1 d−1). In the stratified macrocosm, a substantial amount of viral lysate DOM (2.43–17.87 μg L−1 d−1) was released into the upper riverine water, and viral lysis and DOM release (0.35–5.75 μg L−1 d−1) were reduced in the mixed water layer between riverine water and seawater. Viral lysis was stimulated at the bottom of stratified macrocosm, potentially fueled by the sinking of particulate organic carbon. Significant positive and negative associations between lytic viral production and different fluorescent DOM components were found in the starved and stratified macrocosm, indicating the potentially complex viral impacts on the production and utilization of DOM. Results also revealed the significant viral contribution to pools of both relatively higher molecular weight labile DOM and lower molecular weight recalcitrant DOM. Our study suggests that viruses have heterogeneous impact on the cycling and fate of DOM in aquatic environments.
Cyanate is a nitrogen and energy source for diverse marine microorganisms, playing important roles in the nitrogen cycle. Despite the extensive research on cyanate utilization, the sources of this ...nitrogen compound remain largely enigmatic. To unravel the sources of cyanate, distributions and production of cyanate during photochemical degradation of natural dissolved organic matter (DOM) were investigated across various environments, including freshwater, estuarine, coastal areas in Florida, and the continental and slope regions of the North American mid-Atlantic Ocean (NATL). Cyanate production was also examined during the photochemical degradation of exudates from a typical strain of
Synechococcus
, an important phytoplankton component. To deepen our understanding of the sources and production mechanisms of cyanate, its production was assessed during the photochemical degradation of a natural seawater DOM supplemented with five nitrogen–containing compounds with distinguishing structures and functional groups. Generally, cyanate exhibited higher concentrations in the Florida coastal, estuarine, and freshwater environments than the NATL. However, cyanate distribution did not consistently align with its production rates. Despite significantly low concentrations in the NATL, DOM from this region exhibited cyanate production rates comparable to estuarine and Florida coastal environments. Although relatively high cyanate concentrations were observed in the freshwaters, DOM in this environment exhibited very low cyanate production rates. A highly significant correlation was observed between cyanate and chlorophyll
a
(Chl
a
) concentrations in these areas. Moreover, in most estuarine and NATL stations, cyanate concentration and production rate in the Chl
a
maximum layer were significantly higher than in other layers. Cyanate was produced during the photochemical degradation of the
Synechococcus
exudates. The cyanate production was significantly enhanced when the natural seawater DOM was supplemented with GlycylGlycine, 4-(methylamino) benzoic acid, 4-ethyl(methyl)amino benzaldehyde or methyl 2-aminobenzoate. Our study implies that photochemical degradation of marine DOM, especially phytoplankton-derived DOM, is a substantial source of cyanate in the ocean. Additionally, cyanate may form during the degradation of peptides and small aromatic compounds in DOM, providing novel insights into the nitrogen cycle.
Chronic kidney disease (CKD) is increasingly recognized as a stroke risk factor, but its exact relationship with cerebrovascular disease is not well-understood. We investigated the development of ...cerebral small vessel disease using in vivo and in vitro models of CKD.
CKD was produced in aged C57BL/6J mice using an adenine-induced tubulointerstitial nephritis model. We analyzed brain histology using Prussian blue staining to examine formation of cerebral microhemorrhage (CMH), the hemorrhagic component of small vessel disease and the neuropathological substrate of MRI-demonstrable cerebral microbleeds. In cell culture studies, we examined effects of serum from healthy or CKD patients and gut-derived uremic toxins on brain microvascular endothelial barrier.
CKD was induced in aged C57BL/6J mice with significant increases in both serum creatinine and cystatin C levels (p < 0.0001) without elevation of systolic or diastolic blood pressure. CMH was significantly increased and positively correlated with serum creatinine level (Spearman r = 0.37, p < 0.01). Moreover, CKD significantly increased Iba-1-positive immunoreactivity by 51% (p < 0.001), induced a phenotypic switch from resting to activated microglia, and enhanced fibrinogen extravasation across the blood-brain barrier (BBB) by 34% (p < 0.05). On analysis stratified by sex, the increase in CMH number was more pronounced in male mice and this correlated with greater creatinine elevation in male compared with female mice. Microglial depletion with PLX3397 diet significantly decreased CMH formation in CKD mice without affecting serum creatinine levels. Incubation of CKD serum significantly reduced transendothelial electrical resistance (TEER) (p < 0.01) and increased sodium fluorescein permeability (p < 0.05) across the endothelial monolayer. Uremic toxins (i.e., indoxyl sulfate, p-cresyl sulfate, and trimethylamine-N-oxide) in combination with urea and lipopolysaccharide induced a marked drop in TEER compared with the control group (p < 0.0001).
CKD promotes the development of CMH in aged mice independent of blood pressure but directly proportional to the degree of renal impairment. These effects of CKD are likely mediated in part by microglia and are associated with BBB impairment. The latter is likely related to gut-derived bacteria-dependent toxins classically associated with CKD. Overall, these findings demonstrate an important role of CKD in the development of cerebral small vessel disease.
•Particulate nitrogenous compounds increased in the later stage of the incubation.•Nitrifiers abundance was positively coupled to particulate nitrogenous compounds.•Compounds released by nitrifiers ...triggered degradation of refractory organic matter.
Organic carbon produced by nitrifiers plays an important role in maintaining the microbial metabolism in the aphotic ocean layer with carbon and energy scarcity. However, the contribution of nitrifiers to organic carbon processing remains unclear. To explore how nitrification impacts the material cycle in the starved ecosystem, we set up an ultra-large volume, long-term incubation experiment. Seawater collected from the Halifax coastal ocean was pumped into the Aquatron Tower Tank located at Dalhousie University, Canada, and was incubated under dark conditions for 73 days. The results indicated that the relative abundance of nitrifiers increased and nitrification was strengthened in the dark system where energy and organic carbon were scarce. The importance of nitrogenous compounds in particulate materials increased over the course of the incubation. Correlation analysis showed that the relative abundances of nitrifiers and particulate organic compounds containing nitrogen were significantly and positively correlated. Furthermore, network analysis suggested that metabolic processes related to nitrogenous and aromatic compounds are most important to particle associated bacteria. This study suggests that the nitrifiers could produce a series of organic compounds that result in the alteration of organic matter composition by promoting the degradation of recalcitrant aromatic compounds, which has important implications for organic matter processing in the starved dark ecosystem.
A novel Gram-stain-negative, aerobic, yellow-pigmented bacterium was isolated from seawater of Aoshan Bay, and designated as strain ASW18
. Strain ASW18
was a long-rod-shaped bacterium without ...flagellum and lacked gliding ability. Based on 16S rRNA gene phylogeny, strain ASW18
showed the closest relationship to
MCCC 1A06690
, with a sequence similarity of 97.0 %. Strain ASW18
was able to grow at 25-40 °C, at pH 5.5-9.5 and with 0.5-9 % (w/v) NaCl. The genomic DNA G+C content of strain ASW18
was 37.3 %. The predominant cellular fatty acids of strain ASW18
were iso-C
, iso-C
3-OH and iso-C
G. The major polar lipids were phosphatidylethanolamine, phosphatidyldimethylethanolamine, an aminolipid and three unidentified lipids. The respiratory quinone of strain ASW18
was menaquinone with six isoprene units (MK-6). Based on the present polyphasic analysis, strain ASW18
represents a novel species of the genus
, for which the name
sp. nov. is proposed; the type strain is ASW18
(=MCCC 1K04203
=KCTC 72852
). In addition, it is also proposed that
should be reclassified as
comb. nov.; the type strain is CSW06
(=CGMCC 1.15761
=JCM 31455
=KCTC 52375
=MCCC 1K03195
).
PDF
