Coastal upwelling drives ecosystem temporal variability from the surface to the abyssal seafloor.

Long-term biological time series that monitor ecosystems across the ocean's full water column are extremely rare. As a result, classic paradigms are yet to be tested. One such paradigm is that variations in coastal upwelling drive changes in marine ecosystems throughout the water column. We examine this hypothesis by using data from three multidecadal time series spanning surface (0 m), midwater (200 to 1,000 m), and benthic (~4,000 m) habitats in the central California Current Upwelling System. Data include microscopic counts of surface plankton, video quantification of midwater animals, and imaging of benthic seafloor invertebrates. Taxon-specific plankton biomass and midwater and benthic animal densities were separately analyzed with principal component analysis. Within each community, the first mode of variability corresponds to most taxa increasing and decreasing over time, capturing seasonal surface blooms and lower-frequency midwater and benthic variability. When compared to local wind-driven upwelling variability, each community correlates to changes in upwelling damped over distinct timescales. This suggests that periods of high upwelling favor increase in organism biomass or density from the surface ocean through the midwater down to the abyssal seafloor. These connections most likely occur directly via changes in primary production and vertical carbon flux, and to a lesser extent indirectly via other oceanic changes. The timescales over which species respond to upwelling are taxon-specific and are likely linked to the longevity of phytoplankton blooms (surface) and of animal life (midwater and benthos), which dictate how long upwelling-driven changes persist within each community.

Abyssal deposit-feeding rates consistent with the metabolic theory of ecology.

The Metabolic Theory of Ecology (MTE) posits that metabolic rate controls ecological processes, such as the rate of resource uptake, from the individual- to the ecosystem-scale. Metabolic rate has been found empirically to be an exponential function of whole organism body mass. We test a fundamental assumption of MTE, whether resource uptake scales to metabolism, by examining detritivores accessing a single common resource pool, an ideal study case. We used an existing empirical model of ingestion for aquatic deposit feeders adjusted for temperature to test whether ingestion by abyssal deposit feeders conforms to MTE-predicted feeding rates. We estimated the sediment deposit-feeding rates of large invertebrates from two abyssal study sites using time-lapse photography, and related those rates to body mass, environmental temperature, and sediment organic matter content using this framework. Ingestion was significantly related to individual wet mass, with a mass-scaling coefficient of 0.81, with 95% confidence intervals that encompass the MTE-predicted value of 0.75, and the same pattern determined in other aquatic systems. Our results also provide insight into the potential mechanism through which this fundamental assumption operates. After temperature correction, both deep- and shallow-water taxa might be summarized into a single mass-scaled ingestion rate.

Episodic organic carbon fluxes from surface ocean to abyssal depths during long-term monitoring in NE Pacific.

Growing evidence suggests substantial quantities of particulate organic carbon (POC) produced in surface waters reach abyssal depths within days during episodic flux events. A 29-year record of in situ observations was used to examine episodic peaks in POC fluxes and sediment community oxygen consumption (SCOC) at Station M (NE Pacific, 4,000-m depth). From 1989 to 2017, 19% of POC flux at 3,400 m arrived during high-magnitude episodic events (≥mean + 2 σ), and 43% from 2011 to 2017. From 2011 to 2017, when high-resolution SCOC data were available, time lags between changes in satellite-estimated export flux (EF), POC flux, and SCOC on the sea floor varied between six flux events from 0 to 70 days, suggesting variable remineralization rates and/or particle sinking speeds. Half of POC flux pulse events correlated with prior increases in EF and/or subsequent SCOC increases. Peaks in EF overlying Station M frequently translated to changes in POC flux at abyssal depths. A power-law model (Martin curve) was used to estimate abyssal fluxes from EF and midwater temperature variation. While the background POC flux at 3,400-m depth was described well by the model, the episodic events were significantly underestimated by ∼80% and total flux by almost 50%. Quantifying episodic pulses of organic carbon into the deep sea is critical in modeling the depth and intensity of POC sequestration and understanding the global carbon cycle.

Links between deep-sea respiration and community dynamics.

It has been challenging to establish the mechanisms that link ecosystem functioning to environmental and resource variation, as well as community structure, composition, and compensatory dynamics. A compelling hypothesis of compensatory dynamics, known as "zero-sum" dynamics, is framed in terms of energy resource and demand units, where there is an inverse link between the number of individuals in a community and the mean individual metabolic rate. However, body size energy distributions that are nonuniform suggest a niche advantage at a particular size class, which suggests a limit to which metabolism can explain community structuring. Since 1989, the composition and structure of abyssal seafloor communities in the northeast Pacific and northeast Atlantic have varied interannually with links to climate and resource variation. Here, for the first time, class and mass-specific individual respiration rates were examined along with resource supply and time series of density and biomass data of the dominant abyssal megafauna, echinoderms. Both sites had inverse relationships between density and mean individual metabolic rate. We found fourfold variation in echinoderm respiration over interannual timescales at both sites, which were linked to shifts in species composition and structure. In the northeastern Pacific, the respiration of mobile surface deposit feeding echinoderms was positively linked to climate-driven particulate organic carbon fluxes with a temporal lag of about one year, respiring - 1-6% of the annual particulate organic carbon flux.

Feeding preferences of abyssal macrofauna inferred from in situ pulse chase experiments.

Climatic fluctuations may significantly alter the taxonomic and biochemical composition of phytoplankton blooms and subsequently phytodetritus, the food source for the majority of deep-sea communities. To examine the response of abyssal benthic communities to different food resources we simulated a food sedimentation event containing diatoms and coccolithophorids at Station M in the NE Pacific. In one set of experiments we measured incorporation of diatomC and coccoN into the macrofauna using isotopically enriched (13)C-diatoms and (15)N-coccolithophores. In a second experiment we measured incorporation of C and N from dual-labelled ((13)C and (15)N) diatoms. The second experiment was repeated 2 months later to assess the effect of seasonality. The simulated food pulses represented additions of 650 - 800 mg C m(-2) and 120 mg N m(-2) to the seafloor. In all cases rapid incorporation of tracer was observed within 4 days, with between 20% and 52% of the macrofauna displaying evidence of enrichment. However, incorporation levels of both diatomC and coccoN were low (<0.05% and 0.005% of the added C and N). Incorporation of labelled diatoms was similar during both June and September suggesting that the community was not food limited during either period. We found no evidence for selective ingestion of the different food types in the metazoan fauna suggesting that macrofauna do not have strong preferences for diatom vs. coccolithophore dominated phytodetrital pulses. C∶N ratios from both experiments suggest that the metazoan macrofauna community appear to have higher C demands and/or assimilation efficiencies compared to N. Concomitantly, the foraminifera preferentially selected for diatomN over coccoN, and we suggest that this may be related to foraminiferal requirements for intracellular nitrate. These experiments provide evidence that abyssal faunal feeding strategies are in part driven by an organism's internal stoichiometric budgets and biochemical requirements.

Deep ocean communities impacted by changing climate over 24 y in the abyssal northeast Pacific Ocean.

The deep ocean, covering a vast expanse of the globe, relies almost exclusively on a food supply originating from primary production in surface waters. With well-documented warming of oceanic surface waters and conflicting reports of increasing and decreasing primary production trends, questions persist about how such changes impact deep ocean communities. A 24-y time-series study of sinking particulate organic carbon (food) supply and its utilization by the benthic community was conducted in the abyssal northeast Pacific (~4,000-m depth). Here we show that previous findings of food deficits are now punctuated by large episodic surpluses of particulate organic carbon reaching the sea floor, which meet utilization. Changing surface ocean conditions are translated to the deep ocean, where decadal peaks in supply, remineralization, and sequestration of organic carbon have broad implications for global carbon budget projections.

Bathydorus laniger and Docosaccus maculatus (Lyssacinosida; Hexactinellida): Two new species of glass sponge from the abyssal eastern North Pacific Ocean.

Two new species of glass sponge were discovered from the abyssal plain 200 km west of the coast of California (Station M). The sponges have similar gross morphology--an unusual plate-like form with basalia stilling the body above soft abyssal sediments. Bathydorus laniger sp. n. differs from its congeners by the presence of dermal and atrial stauractins; it is also supported by smooth hypodermal pentactins and hypoatrial hexactins. Microscleres include oxyhexasters and oxyhemihexasters. Docosaccus maculatus sp. n. contains large hexactins (>1 cm), characteristic of the genus. Megascleres include dermal hexactins, atrial pentactins, and choanosomal hexactins and diactins. Microscleres include oxytipped hemihexasters and floricomes. Several features serve to differentiate this species from its only known congener.

The role of carrion supply in the abundance of deep-water fish off California.

Few time series of deep-sea systems exist from which the factors affecting abyssal fish populations can be evaluated. Previous analysis showed an increase in grenadier abundance, in the eastern North Pacific, which lagged epibenthic megafaunal abundance, mostly echinoderms, by 9-20 months. Subsequent diet studies suggested that carrion is the grenadier's most important food. Our goal was to evaluate if changes in carrion supply might drive the temporal changes in grenadier abundance. We analyzed a unique 17 year time series of abyssal grenadier abundance and size, collected at Station M (4100 m, 220 km offshore of Pt. Conception, California), and reaffirmed the increase in abundance and also showed an increase in mean size resulting in a ∼6 fold change in grenadier biomass. We compared this data with abundance estimates for surface living nekton (pacific hake and jack mackerel) eaten by the grenadiers as carrion. A significant positive correlation between Pacific hake (but not jack mackerel) and grenadiers was found. Hake seasonally migrate to the waters offshore of California to spawn. They are the most abundant nekton species in the region and the target of the largest commercial fishery off the west coast. The correlation to grenadier abundance was strongest when using hake abundance metrics from the area within 100 nmi of Station M. No significant correlation between grenadier abundance and hake biomass for the entire California current region was found. Given the results and grenadier longevity, migration is likely responsible for the results and the location of hake spawning probably is more important than the size of the spawning stock in understanding the dynamics of abyssal grenadier populations. Our results suggest that some abyssal fishes' population dynamics are controlled by the flux of large particles of carrion. Climate and fishing pressures affecting epipelagic fish stocks could readily modulate deep-sea fish dynamics.

Phylogenetic diversity of sediment bacteria from the deep Northeastern Pacific Ocean: a comparison with the deep Eastern Mediterranean Sea.

The variability of bacterial community composition and diversity was studied by comparative analysis of five 16S rRNA gene clone libraries from deep-sea sediments (water column depth: 4000 m) of the Northeastern Pacific Ocean and Eastern Mediterranean Sea. This is the first comparison of the bacterial communities living in these deep-sea ecosystems. The estimated chlorophyll a, organic carbon, and C/N ratio provided evidence of significant differences in the trophic state of the sediments between the Northeastern Pacific Ocean and the much warmer Eastern Mediterranean Sea. A diverse range of 16S rRNA gene phylotypes was found in the sediments of both regions. These were represented by 11 different taxonomic groups, with Gammaproteobacteria predominating in the Northeastern Pacific Ocean sediments and Acidobacteria in the Eastern Mediterranean microbial community. In addition, several 16S rRNA gene phylotypes only distantly related to any of the previously identified sequences (non-affiliated rRNA genes) represented a significant fraction of the total sequences. The potential diversity at the two sites differs but remains largely unexplored and remains of continuing scientific interest.

2-Amino-5-(3,4-dimethoxybenzylidene)-1-methylimidazol-4(5H)-one N,N-dimethylformamide monosolvate.

The crystal structure of the title compound, C(13)H(15)N(3)O(3) x C(3)H(7)NO, was determined as part of a larger project focusing on creatinine derivatives as potential pharmaceuticals. The molecule is essentially planar, in part because of intramolecular hydrogen bonding. Inversion-related pairs of molecules result from intermolecular hydrogen bonding. The pi systems of 2-amino-5-(3,4-dimethoxybenzylidene)-1-methylimidazol-4(5H)-one and an inversion-related molecule overlap slightly, indicating a small amount of pi-pi stacking. Bond lengths, angles and torsion angles are consistent with similar structures, except in the imidazolone ring near the doubly bonded C atom, where significant differences occur.

Gene flow from weedy red rice (Oryza sativa L.) to cultivated rice and fitness of hybrids.

BACKGROUND: Gene transfer from weeds to crops could produce weedy individuals that might impact upon the evolutionary dynamics of weedy populations, the persistence of escaped genes in agroecosystems and approaches to weed management and containment of transgenic crops. The present aim was to quantify the gene flowrate from weedy red rice to cultivated rice, and evaluate the morphology, phenology and fecundity of resulting hybrids. Field experiments were conducted at Stuttgart and Rohwer, Arkansas, USA. Twelve red rice accessions and an imazethapyr-resistant rice (Imi-R; Clearfield) were used. RESULTS: Hybrids between Imi-R rice x red rice were 138-150 cm tall and flowered 1-5 days later than the rice parent, regardless of the red rice parent. Hybrids produced 20-50% more seed than the rice parent, but had equivalent seed production to the majority of red rice parents. Seeds of all hybrids were red, pubescent and dehisced at maturity. For the majority of hybrids, seed germination was higher than that of the red rice parent. The gene flowrate from red rice to rice was 0.01-0.2% and differed by red rice biotype. The hybrids had higher fecundity and potential competitive ability than the rice parent, and in some cases also the red rice parent. CONCLUSIONS: Red rice plants are vectors of gene flow back to cultivated rice and other weedy populations. The progeny of red rice hybrids from cultivated rice mother plants have higher chances of persistence than those from red rice mother plants. Gene flow mitigation strategies should consider this scenario.

Connections between climate, food limitation, and carbon cycling in abyssal sediment communities.

Diverse faunal groups inhabit deep-sea sediments over much of Earth's surface, but our understanding of how interannual-scale climate variation alters sediment community components and biogeochemical processes remains limited. The vast majority of deep-sea communities depend on a particulate organic carbon food supply that sinks from photosynthetically active surface waters. Variations in food supply depend, in part, on surface climate conditions. Proposed ocean iron fertilization efforts are also intended to alter surface production and carbon export from surface waters. Understanding the ecology of the abyssal sediment community and constituent metazoan macrofauna is important because they influence carbon and nutrient cycle processes at the seafloor through remineralization, bioturbation, and burial of the sunken material. Results from a 10-year study in the abyssal NE Pacific found that climate-driven variations in food availability were linked to total metazoan macrofauna abundance, phyla composition, rank-abundance distributions, and remineralization over seasonal and interannual scales. The long-term analysis suggests that broad biogeographic patterns in deep-sea macrofauna community structure can change over contemporary timescales with changes in surface ocean conditions and provides significant evidence that sediment community parameters can be estimated from atmospheric and upper-ocean conditions. These apparent links between climate, the upper ocean, and deep-sea biogeochemistry need to be considered in determining the long-term carbon storage capacity of the ocean.

Free-drifting icebergs: hot spots of chemical and biological enrichment in the Weddell Sea.

The proliferation of icebergs from Antarctica over the past decade has raised questions about their potential impact on the surrounding pelagic ecosystem. Two free-drifting icebergs, 0.1 and 30.8 square kilometers in aerial surface area, and the surrounding waters were sampled in the northwest Weddell Sea during austral spring 2005. There was substantial enrichment of terrigenous material, and there were high concentrations of chlorophyll, krill, and seabirds surrounding each iceberg, extending out to a radial distance of approximately 3.7 kilometers. Extrapolating these results to all icebergs in the same size range, with the use of iceberg population estimates from satellite surveys, indicates that they similarly affect 39% of the surface ocean in this region. These results suggest that free-drifting icebergs can substantially affect the pelagic ecosystem of the Southern Ocean and can serve as areas of enhanced production and sequestration of organic carbon to the deep sea.

Synthesis of thiazolone-based sulfonamides as inhibitors of HCV NS5B polymerase.

Several thiazolone-based sulfonamides were prepared, utilizing various hetero-aryl sulfonyl chlorides and different aldehydes, as inhibitors of NS5B polymerase, to target HCV. The best compound showed 0.6 microM [corrected] of IC50 inhibitory activity.

Parallel synthesis of 5-cyano-6-aryl-2-thiouracil derivatives as inhibitors for hepatitis C viral NS5B RNA-dependent RNA polymerase.

From random screening of our compound libraries, we identified a hit compound with an IC50 of 27 microM against hepatitis C viral NS5B RNA-dependent RNA polymerase. By using a parallel synthetic strategy, a series of its derivatives were synthesized. From their anti-HCV activity screening, compounds with single digital 3.8 micromolar activity were obtained.

Parallel synthesis of pteridine derivatives as potent inhibitors for hepatitis C virus NS5B RNA-dependent RNA polymerase.

From compound library screening using an HCV NS5B RNA-dependent RNA polymerase enzymatic assay, we identified a pteridine hit compound with an IC(50) of 15 microM. Our SAR studies were focused on the different groups at the 6- and 7-positions, substitutions at the 4-position, and replacement of N(1) or N(3) with carbon in the pteridine ring. We found that NH or OH at 4-position is critical for the inhibitory activity. Furthermore, a hydrophobic substituent at the 4-position may help compounds permeate through the cell membrane.

Shifts in deep-sea community structure linked to climate and food supply.

A major change in the community structure of the dominant epibenthic megafauna was observed at 4100 meters depth in the northeast Pacific and was synchronous to a major El Niño/La Niña event that occurred between 1997 and 1999. Photographic abundance estimates of epibenthic megafauna from 1989 to 2002 show that two taxa decreased in abundance after 1998 by 2 to 3 orders of magnitude, whereas several other species increased in abundance by 1 to 2 orders of magnitude. These faunal changes are correlated to climate fluctuations dominated by El Niño/La Niña. Megafauna even in remote marine areas appear to be affected by contemporary climatic fluctuations. Such faunal changes highlight the importance of an adequate temporal perspective in describing biodiversity, ecology, and anthropogenic impacts in deep-sea communities.

Synthesis of new 2'-beta-C-methyl related triciribine analogues as anti-HCV agents.

Ten new beta-D-ribofuranosyl and 2'-beta-C-methyl-beta-D-ribofuranosyl triciribine derivatives 4-13 with various N4 and 6-N substituents on the tricyclic ring were synthesized from the corresponding toyocamycin and new 2'-beta-C-methyl toyocamycin derivatives. The inhibitory studies of these compounds in the HCV replicon assay reveal that some of them possess interesting anti-HCV properties with low cytotoxicity.

Solid-phase synthesis of bleomycin group antibiotics. Construction of a 108-member deglycobleomycin library.

The bleomycins (BLMs) are structurally related glycopeptide antibiotics isolated from Streptomyces verticillus that mediate the sequence-selective oxidative damage of DNA and RNA. Deglycobleomycin, which lacks the carbohydrate moiety, cleaves DNA analogously to bleomycin itself, albeit less potently, and has been used successfully for analyzing the functional domains of bleomycin. Although structural modifications to bleomycin and deglycobleomycin have been reported, no bleomycin or deglycobleomycin analogue having enhanced DNA cleavage activity has yet been described. The successful synthesis of a deglycobleomycin on a solid support has permitted the facile solid-phase synthesis of 108 unique deglycobleomycin analogues through parallel solid-phase synthesis. Each of the deglycobleomycin analogues was synthesized efficiently; the purity of each crude product was greater than 60%, as determined by HPLC integration. The solid-phase synthesis of the deglycobleomycin library provided near-milligram to milligram quantities of each deglycobleomycin, thereby permitting characterization by (1)H NMR and high-resolution mass spectrometry. Each analogue demonstrated supercoiled plasmid DNA relaxation above background cleavage; the library included two analogues that mediated plasmid relaxation to a greater extent than the parent deglycobleomycin molecule.