Differences In Organic Content Research Articles

Gelatinous and soft-bodied zooplankton in the Northeast Pacific Ocean: organic, elemental, and energy contents

Gelatinous and soft-bodied zooplankton (GZ) have long been considered to have low energetic value (‘trophic dead end hypothesis’) and be insufficient to sustain higher trophic levels. However, the nutritional composition and energy content of GZ are often poorly known for entire groups, ignoring species-, size-, and stage-specific differences. In this study, organic matter and elemental composition (carbon and nitrogen) were measured for >1000 specimens from 34 GZ species collected from neritic and oceanic waters of the Northeast Pacific between 2014 and 2020. Species included 3 gastropods, 16 hydrozoans, 2 nude ctenophores, 6 scyphozoans, 3 tentaculate ctenophores, and 4 thaliaceans. Organic content and elemental composition were used to estimate energy content using published conversion factors and differed between and within taxonomic classes. Size-dependent variability was shown for several species. Differences in organic content and elemental composition by development stage were observed in a salp and scyphomedusa species, highlighting the need to consider life cycle stages separately. The relative energy values of GZ were generally low and highly variable, although some taxa were comparable to crustaceans. The findings of the present study emphasise the need for a more detailed consideration of GZ in marine food web models and time series analyses, to take into account their inter- and intraspecific variability.

Hummocks in alpine tundra, northern British Columbia, Canada: distribution, morphology and organic carbon composition

Hummocks develop by cryoturbation in fine-grained frost-susceptible soils and their stage of maturity may affect the translocation of organics in Cryosols. This study examines the distribution and morphology of hummocks in the Chuck Creek Trail Valley (northern British Columbia) and determines the quantity, distribution, and composition of organic matter in their soils. Hummocks occupy about 5%–20% of the valley and their morphology is largely affected by their silt content. Cryoturbated intrusions, radiocarbon dated to 2814 and 1648 cal year B.P., suggest that hummock development was initiated during the cooler late Holocene. Hummocks have an average soil organic carbon density of 16.3 kg m−2 in the uppermost 1 m, with 62% stored in the top 25 cm. Organics are mainly present as particulate organic matter in the O-horizon (25%–80%), characterized by degradable alkyl C and O/N-alkyl groups, but occur as mineral-associated organic matter (96%–98%) composed of recalcitrant aromatic and aliphatic C groups in the underlying B and C horizons. Minor differences in organic content and composition occur between hummock tops and troughs, and between hummocks showing different stages of maturity. In the absence of an observed frost table, contemporary hummock activity is attributed to seasonal freezing and thawing.

Retention of organic matter by cellulose acetate membranes cleaned with hypochlorite

Cleaning of ultrafiltration (UF) membranes is usually performed with addition of powerful oxidizing agents such as aqueous chlorine. The results of cleaning are assessed by flux levels, and complete restoration of initial flux indicates that the membrane is usable for further operation. The cleaning is performed in short time periods using high concentrations of cleaning agent, and that operation often results in partial loss of membrane integrity. Pristine and chlorine-cleaned 20 kDa cellulose acetate membranes were compared to find how the cleaning influences the retention of organic matter. The experiments were performed on secondary effluents of Ashkelon municipal wastewater treatment plant (Southern Israel) with average total organic carbon level of 14 mg/L. The effluents were pretreated by 130 mg/L FeCl 3·6H 2O and 0.6 g/L powdered activated carbon. The results of current study indicate that despite partial disintegration, flux drop and loss of mechanical strength, proper pretreatment is effective for retention of organic matter by UF membranes. Minor difference in organic content of permeates of pristine and chlorine-treated membranes were observed. The possible pathways of gradual degradation of cellulose surface, with formation of carboxyl, aldehyde and ketone end groups were described. Enlargement of membrane’s pore size was followed with streaming potential measurements.

Effects of ghost shrimp on zinc and cadmium in sediments from Tampa Bay, FL

This study investigated the effects that ghost shrimp have on the distribution of metals in sediment. We measured levels of HNO 3-extractable zinc and cadmium in surface sediment, in ghost shrimp burrow walls and in sediment ejected by the ghost shrimp from their burrows, at five sandy intertidal sites in Tampa Bay. Ghost shrimp densities and their rate of sediment ejection were also quantified, as were sediment organic content and silt + clay content. Densities of ghost shrimp ( Sergio trilobata and Lepidophthalmus louisianensis) averaged 33/m 2 at our sites, and they ejected sediment at an average rate of 28 g/burrow/day. Levels of both Zn and Cd were significantly higher in burrow walls than in surface sediments. Sediment ejected by the shrimp from their burrows had elevated levels of Zn (relative to surface sediments) at one of the sites. Sediment organic content and silt + clay content were higher in burrow-wall sediments than in ejected sediment, which in turn tended to have values above those of surface sediments. Differences in levels of HNO 3-extractable Zn and Cd among sediment types may be a consequence of these sediments differing in other physiochemical characteristics, though the differences in metal levels remained statistically significant for some sites after correcting for differences in organic content and silt + clay content. We conclude that the presence of ghost shrimp burrows contributes to spatial heterogeneity of sedimentary metal levels, while the ghost shrimp bioturbation results in a significant flux of metals to the sediment surface and is expected to decrease heterogeneity of metal levels in sedimentary depth profiles.

Lowered nutritional quality supplements nudibranch chemical defense.

Reduced palatability through lowered nutritional content is a common defense for modular or gelatinous organisms, but commonly thought unavailable for active, mobile animals. However, nudibranchs - a group of brightly colored, shell-less snails - may supplement their chemical defenses via increased water and ash content. Among 33 gastropod species, nudibranchs differed from prosobranch snails by containing approximately half the digestible organic material per unit wet weight, indicating their caloric value per unit volume will likewise be less than that of shelled snails. Nudibranchs also allocated proportionally less organic material to exterior body regions than to the viscera. Because exterior regions are more easily regenerated and often contain nematocysts or high concentrations of chemical defense, the areas of slug bodies most vulnerable to attack are the best defended, the least valuable to potential predators, and the least costly for nudibranchs to replace. To test how these differences in organic content affect palatability to predators, I offered to Cancer productus, a common molluscivorous crab, pellets differing in organic content (12% or 22% of wet weight) and secondary chemistry (presence or absence of Archidoris montereyensis extract). In no-choice bioassays, chemical extracts reduced feeding by approximately 50%, while lowered organic content reduced feeding by approximately 19%. The effects of organic content did not significantly interact with those caused by chemical extracts, suggesting that, in some contexts, reduced nutritional quality offers a somewhat independent form of antipredator deterrence. Although the nutritional context of defenses is often considered in studies of plants and other organisms suffering partial predation, this study shows that such a multi-factor approach should be more commonly extended to mobile animals.

Hydrothermal sedimentation characteristics of the Dajiangping superlarge pyrite deposit, Yunfu, Guangdong

The Dajiangping pyrite deposit is hosted in a carbonate-clastic rock series which is characterized by a bioreef-chert suite in its middle part. Conformable lenses of various sizes constitute the orebodies which often branch transitionally into the surroundings. Syngenetic deformation fabrics can be observed in orebody No. 3. Orebody No. 4 is composed almost entirely of massive pyrite, with conspicuous hydrothermal sedimentation and bacterium-alga features. The hydrothermal sedimentation origin is also reflected by simple chemistry of the ore (predominated by quartz and pyrite), the presence of U and Th, and the REE compositions of pyrite and ankerite. The ores are rich in organic matter and the difference in organic content between the banded ores and the massive ores is mainly owing to the difference in the clastic components they contain rather than to the subsequent processes of reworking. Go/Ni ratios in the ore may reflect the temperature pattern during hydrothermal sedimentation.

Energy contents and organic constituents in Antarctic and south Chilean marine brown algae

The content of proteins, lipids and carbohydrates and the calorific contents in six Antarctic and three south Chilean brown algae were determined. These constitute the first reports of chemical composition in the endemic Antarctic species Cystosphaera jacquinotii, Phaeurus antarcticus and Desmarestia antarctica. There were no marked differences in total energy levels between Antarctic and cold-temperate species (values between 10.6 and 13 kJ g−1 dry weight). However, species such as Adenocystis utricularis showed significantly higher ash-free energy (26.3 kJ), which is explained in terms of morpho-functional differentiation. Ascoseira mirabilis and Phaeurus antarcticus showed high total lipids (2.1–2.2% dry weight) and soluble carbohydrates (5.9 and 3.4% dry weight). In general, algae from Chile had similar energy levels and no obvious differences in organic content could be found.

Formation of DNA adducts in rat lung following chronic inhalation of diesel emissions, carbon black and titanium dioxide particles.

Exposure of rats to diesel emissions results in the development of lung tumors. The objective of this study was to determine whether the polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs or other polycyclic organic matter adsorbed to diesel particles induces the formation of DNA adducts in the lung when compared to particles with little or no adsorbed organic matter. Rats were exposed to diesel emissions containing particles with over 30% solvent-extractable adsorbed organic matter and to particles with < 0.1% adsorbed organic matter (carbon black particles and TiO2). Wistar rats were exposed to diesel emissions (7.5 mg/m3) for 2 months, 6 months and 2 years and for 2 years to carbon black (11.3 mg/m3) and TiO2 particles (10.4 mg/m3) to compare tumorigenic response and DNA adduct formation in the lung. Two versions of the 32P-postlabeling assay for the detection of DNA adducts were used to tentatively identify nitrated-amine or arylamine adducts formed relative to other nitro PAH based on the demonstrated sensitivity of these adducts to nuclease P1 treatment. Total adduct levels were determined for peripheral lung tissue DNA as detected in a diagonal radioactive zone. One major adduct which migrated outside this region (adduct 1) and a nuclease P1-sensitive adduct (adduct 2) were quantitated separately. Adduct 1 increased significantly over time in the filtered air exposed animals but decreased markedly at the 2 year time points regardless of particle type, presumably as a result of adduct dilution through de novo cell synthesis or cell proliferation invoked in response to particle loading and/or effect on the endogenous synthesis or degradation of DNA reactive moieties. The nuclease sensitive adduct (adduct 2), possibly resulting from exposure to nitro-PAHs, was detected in diesel-exposed rats but was not detected in the rats exposed to TiO2 and carbon black. No significant elevation in PAH-derived adducts, relative to the filtered air controls, was observed in the rodents exposed to diesel emission. Our data suggest that long-term contact with these particles may result in a cell proliferative response, enhanced degradation of I-compounds not related to cell proliferation, and/or synthesis of I-compounds, irrespective of the differences in organic content associated with the three particle types. This response may be an important factor in explaining the reported similarity in tumorigenic response in rodents exposed to diesel emissions, carbon black and TiO2 particles.

Total cadmium concentrations in the water and littoral sediments of Central Ontario Lakes

Lakes within 20 km of Sudbury, Ontario, have significantly higher Cd concentrations in surface waters (geometric mean 122 ng L−1; n = 7) than lakes elsewhere in central Ontario (10.8 ng L−1; n = 57). Cadmium concentrations in water from lakes beyond the Sudbury halo were negatively correlated (r = 0.797; p < 0.001) with pH. A weak correlation between fluoride and Cd concentrations leads to speculation that some Cd may be mobilized from watersheds with Al. Cadmium concentrations in littoral sediments are not elevated near Sudbury. The geometric mean Cd concentration of littoral sediments in central Ontario lakes is 0.08 mg Cd kg−1 dry mass (n = 75). Cadmium concentrations in littoral sediments are strongly correlated with sediment loss on ignition (r = 0.860; p < 0.001). After correction for differences in organic content, littoral sediments are less enriched with Cd than profundal sediments, as reported in the literature. The difference between littoral and profundal sediments, and the sensitivity of Cd concentrations in water to pH, may be due to the importance of Cd binding by Fe/Mn hydrous oxides in the profundal zone, while organic matter binds Cd in the littoral zone. The lack of sensitivity of Cd concentrations in littoral sediments to acidification may be due to the incorporation of much of the Cd in those sediments into organic particulates.