Evidence for Palaeozoic orthoconic cephalopods with bimineralic shells

Based on the aragonite composition of extant and exceptionally preserved fossil cephalopods going back to the early Palaeozoic, it is commonly assumed that all externally shelled cephalopods had an aragonitic shell wall. We demonstrate herein that at least two taxa of Siluro‐Devonian orthoconic nautiloids (Dawsonoceras, Spyroceras) had an original bimineralic shell, which developed convergently with gastropods and bivalves.     

盐碱胁迫下星星草种子萌发过程中有机物,呼吸作用及其几种酶活性的变化

对NaCO3胁迫下星星草种子萌发过程中淀粉酶活性、淀粉酶同工酶、可溶性糖含量、呼吸作用的变化进行了研究。结果表明无盐胁迫下,种于萌发过程中淀粉酶活性、可溶性糖含量、呼吸强度与对照相比均下降,并与Na2CO3胁迫浓度的负相关关系极其显著。Na2CO3胁迫下,水解酶活性降低、储藏物质不能动员、呼吸代谢受抑制是盐胁迫下星星草种子萌发受抑制的原因之一。     

Nutrient couplings between on-site sewage disposal systems, groundwaters, and nearshore surface waters of the Florida Keys

We performed a one-year study to determine the effects of on-site sewage disposal systems (OSDS, septic tanks) on the nutrient relations of limestone groundwaters and nearshore surface waters of the Florida Keys. Monitor wells were installed on canal residences with OSDS and a control site in the Key Deer National Wildlife Refuge on Big Pine Key. Groundwater and surface water samples were collected monthly during 1987 and analyzed for concentrations of dissolved inorganic nitrogen (DIN = NO_f3/sup- + NO_f2/sup- + NH_4/su+), soluble reactive phosphate (SRP), temperature and salinity. Significant nutrient enrichment (up to 5000-fold) occurred in groundwaters contiguous to OSDS; DIN was enriched an average of 400-fold and SRP some 70-fold compared to control groundwaters. Ammonium was the dominant nitrogenous species and its concentration ranged from a low of 0.77 μM in control wells to 2.75 mM in OSDS-enriched groundwaters. Concentrations of nitrate plus nitrite were also highly enriched and ranged from 0.05 μM in control wells to 2.89 mM in enriched groundwaters. Relative to DIN, concentrations of SRP were low and ranged from 30 nM in control wells to 107 μM in enriched groundwaters. N : P ratios of enriched groundwaters were consistently > 100 and increased with increasing distance from the OSDS, suggesting significant, but incomplete, adsorption of SRP by subsurface flow through carbonate substrata. Nutrient concentrations of groundwaters also varied seasonally and were approximately two-fold higher during the winter (DIN = 1035 μM; SRP = 10.3 μM) compared to summer (DIN = 470 μM; SRP = 4.0 μM). In contrast, surface water nutrient concentrations were two-fold higher during the summer (DIN = 5.0 μM; SRP = 0.50 μM) compared to winter (DIN = 2.5 μM; SRP = 0.15 μM). Direct measurement of subsurface groundwater flow rate indicated that tides and increased groundwater recharge enhanced flow some two-fold and six-fold, respectively. Accordingly, the observed seasonal coupling of OSDS-derived nutrients from groundwaters to surface waters is maximum during summer because of seasonally maximum tides and increased hydraulic head during the summer wet season. The yearly average benthic flux of anthropogenic DIN into contiguous canal surface waters is 55 mmol m^-2 day^-1, a value some five-fold greater than the highest rate of benthic N-fixation measured in carbonate-rich tropical marine waters.     

Quantifying production rates and size fractions of parrotfish‐derived sediment: A key functional role on Maldivian coral reefs

Coral reef fish perform numerous important functional roles on coral reefs. Of these, carbonate sediment production, as a by‐product of parrotfish feeding, is especially important for contributing to reef framework construction and reef‐associated landform development. However, only limited data exist on: (i) how production rates vary among reef habitats as a function of parrotfish assemblages, (ii) the relative importance of sediment produced from eroded, reworked, and endogenous sources, or (iii) the size fractions of sediment generated by different parrotfish species and size classes. These parameters influence not only overall reef‐derived sediment supply, but also influence the transport potential and depositional fate of this sedimentary material. Here, we show that parrotfish sediment production varies significantly between reef‐platform habitats on an atoll‐margin Maldivian reef. Highest rates of production (over 0.8 kg m⁻² year⁻¹) were calculated in three of the eight platform habitats; a rubble‐dominated zone, an Acropora spp. dominated zone, and a patch reef zone. Habitat spatial extent and differences in associated parrotfish assemblages strongly influenced the total quantities of sediment generated within each habitat. Nearly half of total parrotfish sediment production occurred in the rubble habitat, which comprised only 8% of the total platform area. Over 90% of this sedimentary material originated from eroded reef framework as opposed to being reworked existing or endogenously produced sediment, and comprised predominantly coral sands (predominantly 125–1000 µm in diameter). This is comparable to the dominant sand types and size fractions found on Maldivian reef islands. By contrast, nearly half of the sediment egested by parrotfish in the Acropora spp. dominated and patch reef habitats resulted from reworked existing sediments. These differences between habitats are a result of the different parrotfish assemblages supported. Endogenous carbonate production was found to be insignificant compared to the quantity of eroded and reworked material. Our findings have important implications for identifying key habitats and species which act as major sources of sediment for reef‐island systems.     

Siliciclastic‐carbonate ramp,a hostile world for carbonate shelf fauna? The example of the Givetian Ardenne Platform

The Givetian platform of the Ardennes Massif records several alternations between a siliciclastic‐carbonate ramp and a carbonate shelf. Usually these depositional contexts are considered as a major disruption implying a perturbation of many ecological parameters. We established the impact of these variations on the biodiversity structure through the study of the trophic organisation. Thanks to a previous microfacies analysis, 550 levels of the Mont d'Haurs section in Givet and ten associated environments were precisely defined. Seven palaeotrophic levels are recognized from micropalaeontological data, including benthic, planktonic, heterotroph and autotroph organisms. The spatial and temporal distributions of these levels have been analysed through means of multivariate analyses. The statistic results show that the distribution of the palaeotrophic levels during periods characterized by a mixed ramp is not significantly different than during carbonate shelf influences. These environmental modifications do not affect the community‐type. These results support recent studies performed on different benthic communities occurring in the Givetian of the Ardennes Massif. Indeed, trilobite and ostracod faunas of this period appear more affected by global environmental changes as the Ka?ák (uppermost Eifelian) and Taghanic (late middle Givetian) events. Moreover, along the proximal‐distal transect on the platform, the reef constitutes the most singular environment. However, contrary with the Frasnian reefs of the Ardennes Massif, which consist of carbonate mud mounds laying on a deep mixed ramp, there is no trilobite community that appears restricted to Givetian reefs. Thus global bioevents during the Middle Devonian have a more important control on the biodiversity than the platform morphology. These results support the view that at wide scales (spatial and temporal), the biodiversity responds more positively to ecological disturbances.     

Spatial distribution of calcite and amorphous calcium carbonate in the cuticle of the terrestrial crustaceans Porcellio scaber and Armadillidium vulgare

The crustacean cuticle is an interesting model to study the properties of mineralized bio-composites. The cuticle consists of an organic matrix composed of chitin–protein fibres associated with various amounts of crystalline and amorphous calcium carbonate. It is thought that in isopods the relative amounts of these mineral polymorphs depend on its function and the habitat of the animal. In addition to the composition, the distribution of the various components should affect the properties of the cuticle. However, the spatial distribution of calcium carbonate polymorphs within the crustacean cuticle is unknown. Therefore, we analyzed the mineralized cuticles of the terrestrial isopods Armadillidium vulgare and Porcellio scaber using scanning electron-microscopy, electron probe microanalysis and confocal μ-Raman spectroscopic imaging. We show for the first time that the mineral phases are arranged in distinct layers. Calcite is restricted to the outer layer of the cuticle that corresponds to the exocuticle. Amorphous calcium carbonate is located within the endocuticle that lies below the exocuticle. Within both layers mineral is arranged in rows of granules with diameters of about 20 nm. The results suggest functional implications of mineral distribution that accord to the moulting and escape behaviour of the animals.     

Mesozoic tectono-sedimentary evolution of Rocca Busambra in western Sicily

The Rocca Busambra ridge in western Sicily is a shallow to pelagic Meso-Cenozoic carbonate structural unit of the Sicilian Chain with a variety of tectono-sedimentary features. Palaeofaults, unconformities (buttress unconformity, onlap, downlap), a network of neptunian dykes with several infilling generations, several large hiatuses, different facies and lateral facies changes, and erosional submarine and subaerial surfaces are observed. Detailed fieldwork and structural analyses have indicated the occurrence of fault planes with different orientations. These data, combined with facies studies and physical-stratigraphy analyses, allow for the distinction of different depositional regions. A lateral change from an open-marine carbonate platform with a stepped fault margin (located in the westernmost sector) to a deeper basinal depositional setting in the east, in the context of an upper slope scalloped margin and base-of-slope systems with talus breccias, is envisaged here. Extensional to transtensional tectonic pulses punctuated the sedimentary evolution during Early Toarcian, Late Jurassic, Early Cretaceous, Late Cretaceous, and Early Miocene times. The collected data show that most fault planes have preserved their original orientations throughout the reactivation processes. The reconstructed Meso-Cenozoic tectono-sedimentary evolution is closely related to the late syn-rift and post-rift tectonic evolution of the Tethyan continental margin.     

Microbial degradation of formaldehyde in white mineral dispersions preserved with formaldehyde-releasing biocides

Two different formaldehyde-degrading microorganisms, Pseudomonas putida and Methylobacterium extorquens, were isolated from calcium carbonate slurry containing the formaldehyde-releasing biocide (ethylenedioxy) dimethanol. Their relative formaldehyde biodegradation and formic acid production kinetics were studied in broth and in calcium carbonate slurry for each microorganism individually, as well as in mixed cultures. Furthermore, the minimal inhibition concentration (MIC) was determined. The results indicated that in slurry, M. extorquens is more tolerant of formaldehyde than P. putida. In slurry, microbial-induced oxidation of formaldehyde caused a temporary accumulation of formic acid, which is presumed to be responsible for pH drop and destabilisation of the calcium carbonate slurry suspension systems. In addition, the residual formaldehyde concentration was observed to drive dominance and recovery of individual formaldehyde-resistant microorganisms in the slurry. Overall, this investigation indicated that biodegradation of formaldehyde in calcium carbonate slurry is brought about by alternating dominance of bacterial genera of mixed formaldehyde-resistant microbial populations.     

Extraction of peroxidase from bitter gourd (Momordica charantia) by three phase partitioning with dimethyl carbonate (DMC) as organic phase

Three phase partitioning (TPP) is most renowned technique used for extraction and purification of natural products. In previous studies of TPP, t-butanol is mainly used as an organic phase. This is the first report that explores ability of dimethyl carbonate (DMC) in the field of TPP as an alternate solvent for t-butanol. In the present study TPP process with t-butanol and DMC as organic phase along with different salts was applied to waste bitter gourd powder to obtained peroxidase enzyme. DMC was found to be compatible with most of salts such as ammonium sulphate and sodium citrate and explored as more efficient solvent than t-butanol. This TPP system provides 4.84 fold purity of peroxidase enzyme at optimum source concentration of 0.15 g/mL, with a system comprising DMC as organic phase, sodium citrate (20%) as salt, agitation speed 120 rpm, pH 7, temperature 30 °C and extraction time of 3 h. Present study has aimed for extraction and separation of peroxidase from bitter gourd waste with TPP technique and ensures the scope of carbonated solvents in extraction and purification of proteins.