Variations in the Properties of Extractable “Humic Matter” and Associated Kerogen in Sediments through Geologic Time: Their Significance for Precambrian Biological Evolution and Paleoecology

Chemical properties and δ¹³C values of benzene/methanol-extractable “humic matter” and associated kerogen in a large, diverse collection of Precambrian and Phanerozoic sediments from different parts of the world showed complex systematic variations through geologic time, reflecting major developments in the history of Precambrian life, and different kinds of sediment yielded similar patterns of variation. Moreover, certain data differentiate clearly between glacial and nonglacial detrital sediments, or between lacustrine and marine sediments, and some data suggest the occurrence of Precambrian land life. The abundance of aromatic groups and the proportion of aliphatic to aromatic groups in the extracts showed little variation from the early Archean (ca. 3.3 Ga) to the mid-Proterozoic (ca. 1.6-1.3 or 1.3-1.1 Ga), whereupon they increased sharply, peaked ca. 1.1-0.900 Ga, and then plunged to a minimum in the late Proterozoic (ca. 0.800 Ga) or early Phanerozoic. This is interpreted as indicating that cyanobacteria were the dominant photoautotrophs until the mid-Proterozoic, when algae evolved, proliferating until the late Proterozoic, whereupon their populations were depleted by herbivorous metazoans. Nitrogenous aromatic material increased to a maximum ca. 3.4–3.3 Ga and then decreased steadily to ca. 1.3 Ga, suggesting that early Precambrian cyanobacteria were enriched in photoprotective as well as photosynthetic tetrapyrrole pigments owing to the lack of ultraviolet radiation-shielding atmospheric O₂ and O₃. The concentration increased again starting ca. 1.3–0.800 Ga, reflecting the rise of algae, peaked ca. 0.680 Ga, and dropped catastrophically to a much lower value in the Cambrian (ca. 0.510 Ga), suggesting mass mortality at the Precambrian-Cambrian boundary.     

Metabarcoding reveals high diversity of benthic foraminifera linked to water masses circulation at coastal Svalbard

Arctic marine biodiversity is undergoing rapid changes due to global warming and modifications of oceanic water masses circulation. These changes have been demonstrated in the case of mega- and macrofauna, but much less is known about their impact on the biodiversity of smaller size organisms, such as foraminifera that represent a main component of meiofauna in the Arctic. Several studies analyzed the distribution and diversity of Arctic foraminifera. However, all these studies are based exclusively on the morphological identification of specimens sorted from sediment samples. Here, we present the first assessment of Arctic foraminifera diversity based on metabarcoding of sediment DNA samples collected in fjords and open sea areas in the Svalbard Archipelago. We obtained a total of 5,968,786 reads that represented 1384 amplicon sequence variants (ASVs). More than half of the ASVs (51.7%) could not be assigned to any group in the reference database suggesting a high genetic novelty of Svalbard foraminifera. The sieved and unsieved samples resolved comparable communities, sharing 1023 ASVs, comprising over 97% of reads. Our analyses show that the foraminiferal assemblage differs between the localities, with communities distinctly separated between fjord and open sea stations. Each locality was characterized by a specific assemblage, with only a small overlap in the case of open sea areas. Our study demonstrates a clear pattern of the influence of water masses on the structure of foraminiferal communities. The stations situated on the western coast of Svalbard that are strongly influenced by warm and salty Atlantic water (AW) are characterized by much higher diversity than stations in the northern and eastern part, where the impact of AW is less pronounced. This high diversity and specificity of Svalbard foraminifera associated with water mass distribution indicate that the foraminiferal metabarcoding data can be very useful for inferring present and past environmental conditions in the Arctic.     

Morphology and microanatomy of harbor porpoise (Phocoena phocoena) dorsal fin tubercles

The unique pattern of small tubercles on the leading edge of the dorsal fins of harbor porpoises (Phocoena phocoena) has been widely noted in the literature, though their structure or function has never been conclusively identified. We examined external morphology and microanatomy of the tubercles for further understanding of the nature of the tubercles. Measurements were taken of height and peak‐to‐peak distance of the tubercles using scaled photographs. Mean tubercle height was standardized as a percentage of the dorsal fin height and ranged from 0.63 to 0.87%. Mean peak‐to‐peak distance ranged from 4.2 ± 2.0 to 5.6 ± 2.0 mm. The microstructure analysis of the dorsal fin leading edge, trailing edge and tubercles revealed an epidermal thickness of 0.7–2.7 mm with the thickest epidermis at the tubercular apex. The epidermis contained three distinct strata (=layers), including the stratum corneum, spinosum, and basale. The stratum corneum was significantly thickened in tubercles, over four times thicker than in the leading or trailing edge of the fin. The stratum spinosum, composed of lipokeratinocytes and lamellar oil bodies, was significantly thinner in the trailing edge than in the other two sites. There was no significant difference in the stratum basale among the three sites. Volume fraction of lipokeratinocytes was significantly higher at the sides of the leading edge and the apex of the tubercles, while volume fraction of lamellar oil bodies was significantly lower at the apex of the tubercles. Though the function of the tubercles is unknown, their position, hardened structure and increased epidermal stratum corneum suggest that they may have hydrodynamic importance. J. Morphol., 2011. © 2010 Wiley‐Liss, Inc.     

Indicating assemblage vulnerability and resilience in the face of climate change by means of adult ground beetle length–weight allometry over elevation strata in Tenerife (Canary Islands)

Adaptive trade-offs in length–weight allometry might reduce vulnerability under climate change of adult ground beetle (Col., Carabidae) assemblages in their original elevation stratum on Tenerife. In particular this study shows that the predictive values for simple log-linear regression parameters were high in all strata and also the F-tests were statistically significant (p < 0.0001). Ground beetle assemblage on upper stratum had smaller coefficients and higher intercepts than did lower ones, indicating that the ground-beetle assemblages may be trading off higher powers for higher resilience via water and thermal efficiency in the face of environmental warming, in opposition to strategies adopted in cool and wet climates. Adults of ground beetle assemblages from warm and dry lower strata might have to be heftier, with encapsulation of bodies and heavily sclerotized exoskeleton, than those from cloudy, cool and wet strata; the latter group, freed from this constraint, would thus be characterized by more elongated, thinner and softer-bodied species. The outlined methodology could become a useful tool for the vulnerability and resilience assessment of natural assemblages, and could theoretically be applied to any latitudinal and altitudinal assemblage.     

Characteristics and use of sleeping sites in Aotus (Cebidae: Primates) in the Amazon lowlands of Peru

In the Amazon lowlands of Peru, Aotus nancymai and A. vociferans were observed to use four different types of sleeping sites: (1) holes in the trunks and branches of dry or senescent trees; (2) concavities in polyaxial branching nodes of trees protected by dense entanglements of creepers, climbing plants, vines, and masses of diverse epiphytes; (3) complex sites among masses of epiphytes, climbers, and vines; and (4) simple sites among thickets and dense foliage. Each type is described. There was competition and sharing of sleeping holes between Aotus and other nocturnal arboreal mammals.     

Facies dependence of spore assemblages and new data on sedimentary influence on spore taphonomy

Palynological studies have been undertaken on Lower Carboniferous (Mississippian) rocks encountered in boreholes from the North Sea to the Baltic Sea (Rügen) in Northern Germany and from an outcrop at the northern border of the Rhenish Slate Mountains in western central Germany. The studied sections belong to different facies realms within the neritic shelf facies. They begin with very near shore coastal clastic facies in the North Sea and onshore Northern Germany, ranging into carbonate platform facies at Rügen, and then into platform slope facies at the northern margin of the Rhenish Slate Mountains. The focus of this study is the analysis of the relationship between sedimentary facies and spore assemblages; therefore, spores were considered only as sedimentary particles. Thus, it was necessary to create a new spore classification scheme based only on relevant sedimentary features. The new scheme distinguishes three classes of miospore based on shape, with each class subdivided into three subclasses based on features of ornament. The diversity of the spore assemblages and the total palynofacies have also been studied. Correlating palynological results from sections representing different sedimentary facies has led to a better understanding of the influence of sedimentary facies on spore assemblages. Correlations have been made at two stratigraphical levels. Regional correlation is undertaken on the Upper Viséan from the coastal clastic facies (North Sea, Northern Germany), the carbonate platform facies (Rügen) and the marginal platform slope facies (Velbert). Local correlation within the carbonate platform facies has been attempted using samples of Mid-Viséan TS zone from four boreholes on Rügen. Certain important differences have been observed. The local correlation at Rügen shows a decrease in spore frequency and spore assemblage diversity related to increasing resedimentation within subsided blocks of the platform. The composition of spore assemblages, strongly dominated by round-shaped spores, is nearly the same in all sections. The regional correlation shows clear proximal–distal trends for the total number of spores and also the diversity and composition of spore assemblages. A strong decrease in triangular and transitional spores from proximal to distal facies was observed. In conclusion, spore assemblages seem to be strongly influenced by sedimentary facies as well as by different sedimentary processes within the facies. Facies dependence of spore assemblages is shown to be an important factor for stratigraphical use of spores and for establishing vegetational and climatic trends.     

Vegetation state changes in the course of shrub encroachment in an African savanna since about 1850 CE and their potential drivers

1. Shrub encroachment has far‐reaching ecological and economic consequences in many ecosystems worldwide. Yet, compositional changes associated with shrub encroachment are often overlooked despite having important effects on ecosystem functioning.
2. We document the compositional change and potential drivers for a northern Namibian Combretum woodland transitioning into a Terminalia shrubland. We use a multiproxy record (pollen, sedimentary ancient DNA, biomarkers, compound‐specific carbon (δ¹³C) and deuterium (δD) isotopes, bulk carbon isotopes (δ¹³Corg), grain size, geochemical properties) from Lake Otjikoto at high taxonomical and temporal resolution.
3. We provide evidence that state changes in semiarid environments may occur on a scale of one century and that transitions between stable states can span around 80 years and are characterized by a unique vegetation composition. We demonstrate that the current grass/woody ratio is exceptional for the last 170 years, as supported by n‐alkane distributions and the δ¹³C and δ¹³Corg records. Comparing vegetation records to environmental proxy data and census data, we infer a complex network of global and local drivers of vegetation change. While our δD record suggests physiological adaptations of woody species to higher atmospheric pCO₂ concentration and drought, our vegetation records reflect the impact of broad‐scale logging for the mining industry, and the macrocharcoal record suggests a decrease in fire activity associated with the intensification of farming. Impact of selective grazing is reflected by changes in abundance and taxonomical composition of grasses and by an increase of nonpalatable and trampling‐resistant taxa. In addition, grain‐size and spore records suggest changes in the erodibility of soils because of reduced grass cover.
4. Synthesis. We conclude that transitions to an encroached savanna state are supported by gradual environmental changes induced by management strategies, which affected the resilience of savanna ecosystems. In addition, feedback mechanisms that reflect the interplay between management legacies and climate change maintain the encroached state.

     

Biomass estimation using satellite remote sensing data—An investigation on possible approaches for natural forest

Vegetation type and its biomass are considered important components affecting biosphere-atmosphere interactions. The measurements of biomass per unit area and productivity have been set as one of the goals for International Geosphere-Biosphere Programme (IGBP). Ground assessment of biomass, however, has been found insufficient to present spatial extent of the biomass. The present study suggests approaches for using satellite remote sensing data for regional biomass mapping in Madhav National Park (MP). The stratified random sampling in the homogeneous vegetation strata mapped using satellite remote sensing has been effectively utilized to extrapolate the sample point biomass observations in the first approach. In the second approach attempt has been to develop empirical models with satellite measured spectral response and biomass. The results indicate that there is significant relationships with spectral responses. These relationships have seasonal dependency in varying phonological conditions. The relationships are strongest in visible bands and middle infrared bands. However, spectral biomass models developed using middle infrared bands would be more reliable as compared to the visible bands as the later spectral regions are less sensitive to atmospheric changes It was observed that brightness and wetness parameters show very strong relationship with the biomass values. Multiple regression equations using brightness and wetness isolates have been used to predict biomass values. The model used has correlation coefficient of 0.77. Per cent error between observed and predicted biomass was 10.5%. The biomass estimated for the entire national park using stratified and spectral response modelling approaches were compared and showed similarity with the difference of only 4.69%. The results indicate that satellite remote sensing data provide capability of biomass estimation     

Sedimentary Losses in the Reservoir Saidenbach: Flux and Sinking Velocities of Dominant Phytoplankton Species

Sedimentation of phytoplankton was studied in the meso/eutrophic reservoir Saidenbach for two years and measured as biovolume in a sedimentation trap near the bottom. It comes to an annual average of 2.76cm³/m² × d (0.4… 10.9) and is statistically significant dependent on the free water concentration measured 14 days before. This allows flux to be reliably calculated without any direct measurement. The bottom is reached above all by diatoms which form 90% of the deposited algae. The sinking velocity of the diatoms is mainly determined by their physiological state: During growth phases low sinking velocities (0.1 … 2m/d) were found, while in decline phases they increased considerably (>6m/d). The highest average sinking velocities found among large diatoms were calculated for Fragilaria crotonensis (3…4m/d), the lowest for Melosira italica (1.5…2m/d). The values for Asterionella formosa, Synedra acus and Diatoma elongatum were between them. Turbulence has no influence on sinking velocity (usually, spring full circulation sees the highest sedimentary losses), but plays an essential part in the survival of the population in free water. Permanent redistribution prevents diatoms from sinking out from the euphotic layer, this “inoculation” making further development possible. On an annual average, phytoplankton forms approximately only one quarter of the whole trap sediment (max. 62%). The flux of the dry weight of seston (2.33g/m² x d on an average) reflects the changes in phytoplankton flux negligibly only and does not reveal any relation to it. so that seston flux is not suitable for determining phytoplankton sedimentation. But it is possible to calculate this at a probability of 65 to 94%, by using the free water concentration measured 14 days before.