Characteristics Of Assemblages Research Articles

DASYCLADALES (GREEN ALGAE) AND SOME BENTHIC FORAMINIFERA FROM THE UPPER CRETACEOUS ILAM FORMATION (LATE CONIACIAN–SATONIAN), SW IRAN (ONSHORE AND OFFSHORE)

New data (onshore, offshore) on the Upper Cretaceous Ilam Formation of southwestern Iran are provided concerning the common presence of dasycladalean green algae (families Triploporellaceae, Polyphysaceae) that have so far been treated mostly in open nomenclature. The assemblage consists of the five taxa Salpingoporella ubaiydhi Radoičić, 1979, Dissocladella ondulata (Raineri, 1922), Trinocladus tripolitanus Raineri, 1922, Clypeina cf. dusanbrstinai Radoičić, 1997, and gen. et sp. indet. The taxa typically prevail in wackestones-packstones but exhibit different distributional patterns. While S. ubaiydhi and T. tripolitanus, rarely associated with D. ondulata, form a characteristic assemblage in a distal infralittoral facies (more diverse assemblage; zone no. 31 of Wynd, 1965), C. cf. dusanbrstinai occurs in a proximal infralittoral facies associated with miliolids among also complex forms (rhapydioninids) (assemblage zone no. 30 of Wynd, 1965). It is concluded that the two assemblage zones refer to different palaeoenvironments, instead of different ages (‘lower’ and ‘upper’). Based on benthic foraminifera, the main part of the Ilam Formation can be ascribed to the Santonian. For the lower part, a late Coniacian age is suggested implied indirectly by the comparably long vertical range of the rotaliid Orbitokathina vonderschmitti Hottinger, 1966 of the studied core. This would be in conformity with the K 150 Arabian Plate K 150 sequence boundary referring to a late Turonian?–early Coniacian hiatus. From a palaeobiogeographic perspective, T. tripolitanus is a cosmopolitan species, S. ubaiydhi is restricted to the area of the former Arabian Plate (subsurface Iraq, Saudi Arabia and Egypt), while C. dusanbrstinai has been recorded only from Serbia (type-locality). In addition to the algae, the stratigraphic discussion includes the occurrence of the benthic foraminifera Reticulinella? kaeveri Cherchi, Radoičić & Schroeder, 1989 and Orbitoides mid-orientalis (Eames & Smout, 1956) in the Ilam Formation.

Lithofacies identification of deep coalbed methane reservoir based on high-resolution seismic inversion

During the exploration and development of deep coalbed methane (CBM), delineating the thickness of coal seam and lithofacies of the roof and floor is one of the major challenging tasks. In past attempts, the prediction methods of these parameters have been limited to the conventional inversion. However, the effect of coal shielding on adjacent reflecting layers restricts the identification of underlying sand effectively by conventional inversion. Also, the depth at which the deep CBM zone is located (1,500–2000 m) produces a significant overlap of P-wave impedance and Vp/Vs of sands and shale which increases classification uncertainty between these two lithofacies. We proposed a new workflow for high-precision quantitative seismic interpretation of deep CBM reservoir. Not only P-wave impedance but also GR is selected as the optimized attributes for lithofacies classification. To reduce the effect of strong reflection of coal seam and identifying thin coal layers, the seismic waveform indication inversion method is used to obtain high-resolution results of P-wave impedance and GR. It uses horizontal changes in seismic waveforms to reflect lithological assemblage characteristics for facies-controlled constraints. Then, Bayesian classification theory is used to achieve three-dimensional lithofacies classification with multi-source data. To improve the continuity and accuracy of the interpreted results, a Markov chain is applied in the Bayesian rule as the spatial prior constraint. A well-associated synthetic test and field data application in Ordos Basin demonstrates the accuracy of the proposed workflow. Compared with conventional inversion, the results of proposed workflow showed higher resolution and accuracy. By providing a new solution for the identification of roof and floor lithofacies of deep CBM reservoir, this workflow aims to contribute to the better exploration and development of deep CBM.

Surface soil phytolith assemblages across an altitudinal transect in the Qilian Mountains of Northwestern China, and their implications for palaeoecologic analysis in arid alpine regions

Reconstructing changes in altitudinal vegetation belts is crucial for comprehending vegetation response to past environmental changes in arid alpine regions, however, proxy data are limited. In this study, we report 51 surface soil phytolith samples from various vegetation types across an altitudinal transect in the arid alpine region of the Qilian Mountains, to elucidate the relationships between vegetation types and phytolith assemblages. Our results show that phytolith morphotypes in surface soil samples could be categorized into 16 classes, with Gobbet, Crenate, Rondel, Elongate entire, and Acutebulbosus being the predominant classes. The characteristics of surface soil phytolith assemblages vary across an altitudinal transect, reflecting differences in local vegetation. Discriminant analysis identifies Cubic, Elongate entire, Crenate, Gobbet, and Rondel as discriminant variables that correlated with five vegetation types (desert vegetation, mountain steppe vegetation, mountain coniferous forest vegetation, subalpine shrub meadow vegetation, and alpine meadow vegetation). We establish five discriminant functions based on the relationships between vegetation types and phytolith assemblages, demonstrating a high accuracy of our method for distinguishing between different vegetation types. These discriminant functions are applicable for distinguishing between diverse vegetation types in the mountains of arid inland regions of Asia. They are also effective in identifying coniferous forest vegetation in mid-latitude mountains. Therefore, these discriminant functions hold significant potential for reconstructing changes in altitudinal vegetation belts in mountainous regions and determining the vegetative types recorded by terminal lakes in arid regions. Our study introduces a new perspective on palaeoecologic analysis in arid alpine regions, advancing our understanding of ecosystem dynamics in response to environmental fluctuations.

Differential characteristics of lithological assemblages and gas-bearing of the Permian Longtan Formation mudstone in well L3, southeastern Sichuan Basin

As the main reservoir of coalbed gas in southeastern Sichuan, the mudstone of the Permian Longtan Formation has been drilled to obtain industrial gas, but the level of exploration and development is low. The researches on the types of lithological assemblages, reservoir characteristics, and gas-bearing properties are poor, which limits the evaluation and selection of the sweet point area for the marine-continental transitional shale gas. In this paper, by comparing the differential of different lithological distribution in the well L3, multiple discriminant functions and logging interpretation models for different lithology are established to determine the classification criteria of lithological assemblage types of shale formations. Based on the experimental results of high-temperature and high-pressure isothermal adsorption, the reservoir space distribution and gas-bearing characteristics of mudstone in different lithological assemblages are compared and analyzed. It is indicated that the four lithological assemblage types are found in the Permian Longtan Formation, including thick mudstone with the interlayer of coalbed (Type I), rich mudstone with the interlayer of sandstone and thin coalbed (Type II), sandstone interbedded with mudstone with the interlayer of coalbed (Type III), and limestone interbedded with sandstone with the interlayer of mudstone (Type IV), which are superimposed with each other. The different pore structure characteristics of mudstone in different lithological assemblages is the main influencing factor of differential gas-bearing property. The dominant lithological assemblages are Type I and Type II. Coalbed and carbonaceous mudstone are the source rock and primary storage space of adsorbed gas. Moreover, with low porosity and permeability, high breakthrough pressure and the strong sealing capacity of regional mudstone, it is easy to form the “microtrap” to store the natural gas. The sealing capacity of mudstone provides a favorable condition for gas preserve. Under the dynamic condition of hydrocarbon generation, the pressure storage box is formed, accompanied with the fine reservoir spaces and gas-bearing contents.

Genesis of the sediment-hosted Qukuleke Au deposit in the East Kunlun Orogenic Belt, NW China: Constraints from geology, apatite U–Pb age, and C–O–S–Pb isotopes

Genetic classification of sediment-hosted Au deposits is often disputed in many orogenic belts around the world. The marine sediment-hosted Qukuleke Au deposit (>5 t Au) is an example of this, which has been attributed to orogenic or intrusion-related type. This paper addresses its metallogeny through detailed geologic and petrographic studies, together with apatite U–Pb dating and C–O–S–Pb isotopes.The hydrothermal paragenesis at Qukuleke is divided into three stages (I to III): Stage I (pre-ore) sheeted quartz veins; Stage II (main ore) pervasive sericite ± carbonate ± apatite ± pyrite ± arsenopyrite alteration associated with quartz–calcite ± stibnite veins; Stage III (post-ore) barren calcite veins. LA-ICP–MS hydrothermal apatite U–Pb dating on Stage II disseminated Au ore yielded 208.1 ± 6.5 Ma, coeval with the Late Triassic post-collisional intrusions from the periphery of Qukuleke deposit. Carbon–oxygen isotopes of Au–Sb ore-related hydrothermal calcite show that the hydrothermal fluids were derived from the marine carbonate ore host with considerable magmatic input. Lead–sulfur isotopes of the Au–Sb ore-related are consistent with those of coeval intrusions around the deposit, but different from those of the local sedimentary strata. Our age and geochemical data suggest the presence of a magma source that supplied the hydrothermal fluids, sulfur and metals for the mineralization. Combining the low sulfide content and the Au–As–W–Sb–Mo assemblage characteristics, the Qukuleke is best classified as a sediment-hosted intrusion-related Au deposit. Considering also the discovery of the large coeval Qukukekedong Au deposit nearby, we propose that Late Triassic intrusion-related Au system is a high-potential exploration target in the western EKOB.

Characteristics of phytoplankton assemblages and their relationship with environmental factors in the Qiongzhou Strait, China

The characteristics and influencing factors of phytoplankton assemblages were analyzed in July (rainy season) and November (dry season) 2022 in the Qiongzhou Strait, China. A total of 68 species of phytoplankton belonging to 33 genera and 3 phyla were recorded. Diatom was the most dominant group. The broad-temperature widespread species were the most abundant. The dominant species in the rainy season were Skeletonema costatum, S. tropicum, Chaetoceros preseudocurvisetus and Thalassionema nitzschioides while those in the dry season were T. frauenfeldii, T. nitzschioides and Coscinodiscus granii. Phytoplankton cell abundance was significantly positively correlated with nitrite and total nitrogen concentrations, and negatively correlated with temperature and pH. Red tide algae occurred with high frequency. All sites were at eutrophic level except for 3 sites in the rainy season, which were at mesotrophic level. Therefore, there is a potential risk of red tides in the Qiongzhou Strait, which requires long-term monitoring and precautions.

Explaining variation in stream fish productivity with biotic and abiotic variables across wadeable rivers in eastern North America

Abstract Biomass production is a key ecosystem process that provides insight into ecological processes such as growth, reproduction, mortality, and energy distribution. Previous studies have considered various fish response measures such as species richness, abundance, and/or biomass as response variables for river ecosystems or the productivity of particular species. However, few studies have investigated how total fish productivity of riverine systems is affected by environmental variables. Here, we identified important abiotic and biotic predictors of fish productivity in wadeable, temperate riverine systems. We investigated the relationships between total stream fish productivity and multiple abiotic and biotic variables in wadeable stream reaches across Ontario, Canada. Variance partitioning was used to evaluate the relative importance of the biotic, landscape, climatic, and geologic variables on total stream fish productivity. A modified bootstrap approach was used for the model‐selection process and to parameterise an empirical fish productivity model. We found that biotic predictors explained more variation in productivity relative to the abiotic variables. The best empirical model included day‐of‐year, growing degree days, latitude, salmonid presence/absence, species richness, and upstream catchment area. Our findings indicate that a combination of both biotic and abiotic variables can provide valuable insight into how ecological processes, such as fish productivity, differ across ecosystems. Species richness and differences in assemblage characteristics may be key determinants of the overall fish productivity in stream systems. Our model can estimate productivity from salmonid presence/absence data and total species richness, instead of fish abundance data, which require larger sampling efforts.

Water stratification alters phytoplankton assemblages in scallop farming waters of the North Yellow Sea in China

As evaluation indicators of the primary productivity, the phytoplankton biomass and community structure are of great significance to the fishery industry, which can be driven by ocean currents, nutrients and water stratification. In the present study, the characteristics of phytoplankton assemblages in different water layers of a typical Yesso scallop farming area in Zhangzi Island, the North Yellow Sea were investigated from March 2021 to January 2022. According to the vertical distribution of temperature, water stratification was observed from June to August (stratification period), and disappeared in March, October and the following January with vertical homogeneity (mixing period). 18S rRNA gene sequencing results revealed that Pyrrophyta was the most dominant phylum during the sampling period, with high gene proportions in the stratification (63.36%) and mixing periods (77.35%). The gene proportion of Bacillariophyta in the stratification period was 5.44%, which was significantly lower than that in the mixing period of 8.93% (p < 0.05). Moreover, Pseudo-nitzschia, a toxin-producing taxon affiliated with Bacillariophyta, exhibited a significantly higher proportion in the stratification period than in the mixing period. During the stratification period, a number of toxin-producing taxa such as Pseudo-nitzschia and Karlodinium were enriched in the bottom layer, which was 1.29-fold and 1.37-fold of that in the surface layer, respectively. Redundancy analysis showed that phosphate and water temperature were major environmental factors driving the vertical distribution of phytoplankton assemblages. The phosphate (0.11 μM) and silicate (2.09 μM) concentrations in the surface layer approached the minimum threshold for phytoplankton growth, and the stoichiometric limitation of phosphate was detected in the surface and middle layers. Collectively, these results indicated that the decreased proportion ratio of Bacillariophyta to Pyrrophyta and unfavorable community composition of Bacillariophyta for scallops were observed during summer, which might result from the phosphate limitation driven by water stratification. The results will further our understanding of the dynamics of phytoplankton communities under the background of intensifying ocean stratification and provide ecological guidance for mollusc mariculture.

Fine characterization of interbedding sand-mudstone based on waveform indication inversion

Abstract Owing to the increasing challenges associated with coal mine exploration and development, extremely precise surveys with high-resolution images are required to support production. Conventional inversion methods cannot provide sufficiently precise images of the complex lithologies in coal measure strata. Accordingly, this study performed research in Qiyuan mining area, Shanxi Province, China, and predicted the complex lithology on the basis of facies control using waveform indication inversion and waveform indication simulation. Horizontal changes in seismic waveforms were used to reflect lithologic assemblage characteristics for facies-controlled constraints, and the vertical mapping the connection between seismic waveform and logging curves was shown. Moreover, high-resolution inversions of wave impedance and natural gamma parameters were conducted. Combined with lithologic shielding and accurate time–depth conversion, the inversions enabled the precise characterization of the lithological assemblage distribution in the study area. Our results showed that waveform indication inversion could distinguish between coal seams and limestone, whereas waveform indication simulation based on natural gamma could effectively distinguish between sandstone and mudstone. Furthermore, the horizontal resolution was improved and the vertical resolution extended to a thickness of 2–3 m. In addition, the inversion results were highly consistent with drilling results, with an error &amp;lt;0.1 m. Therefore, waveform indication inversion and simulation could be applied to coal mines for safe and efficient production.

Habitat and morphological characteristics affect juvenile mortality in five coral reef damselfishes

The abundance and distribution of demersal fishes rely on larvae successfully settling from the pelagic environment to a benthic habitat and their subsequent survival. With high mortality rates during this life stage, settling to a habitat that maximizes survival is critical. However, relationships between settlement choices and subsequent survival are poorly understood and may vary among species with different habitat preferences. To test this, we focused on five congeneric (Pomacentrus) damselfish species that are known to differ in their habitat choices and explored whether habitat associations at settlement influenced survival. Newly settled individuals were tagged and monitored daily for two weeks to estimate natural mortality rates. Morphological attributes of fish and characteristics of settlement habitats, including depth, rugosity, benthic substrata, and local fish assemblages, were used to predict mortality. We found that some species displayed stronger associations with specific benthic substrata at settlement, but contrary to expectations, these selected habitat characteristics were relatively weak predictors of survivorship. Our survival analysis revealed that the best predictors of survivorship were rugosity (P. adelus and P. amboinensis) and two morphological traits, body depth and ocellus size (P. chrysurus and P. adelus). Interestingly, we found that P. moluccensis that settled in areas of high coverage of mounding coral experienced increased mortality. Of the remaining substrata, analysis showed that instead of associating with habitat characteristics enhancing survivorship, individuals tended not to associate with habitats characteristics that increased mortality (e.g., Turbinaria and sand). This study highlights the species-specific drivers of early post-settlement mortality in coral reef fishes.

The Late Palaeolithic and Mesolithic Settlement of Northern Italy: Problems and Perspectives

This paper considers some problems of the Late Palaeolithic and the Mesolithic periods in Northern Italy. More precisely, it deals with chronology, settlement pattern, techno-typological characteristics of knapped stone assemblages, and climatic changes that have taken place in the region from the discovery of the first sites in the 1960s and the excavations that soon followed to the present state of research. The Italian Alps, the Piedmont, and the valleys that descend from the high massifs have yielded important traces of Late Palaeolithic (Final Epigravettian) and Mesolithic (Sauveterrian and Castelnovian) sites and findspots, some of which are rock shelters that were settled throughout several millennia. This paper describes and discusses the evidence available mainly from two regions of the western and eastern Alpine arc, which are characterised by very different landscapes and yielded a great variety of archaeological features.

Ecological importance of low-order streams to macroinvertebrate community composition in Afromontane headwater streams

Low-order streams contribute to the abiotic and biotic character of large rivers and are renowned for harboring unique forms of aquatic flora and fauna. However, most studies on headwater streams mainly focus on the mainstems and overlook the contribution of the tributary systems. Moreover, low-order streams are generally overlooked in legislation and bioassessment programs, and consequently not protected in many countries. To contribute to the recognition of the ecological importance of low-orders streams, this study focused on determining whether river network characteristics and associated physico-chemical parameters can be used to effectively predict the variabilities in macroinvertebrate assemblage characteristics between first-order and second-order streams in the headwaters of the Nzoia River Basin, Kenya. The study quantified the structural and functional community composition, diversity, similarity, and richness of macroinvertebrate communities between the two river systems. Dissolved oxygen, coarse particulate organic matter, conductivity, stream width, depth, discharge and flow velocity were the main predictors of the diversity and distribution of macroinvertebrates in the first order and second-order streams. The first order streams recorded higher abundance of macroinvertebrates than the second-order streams. Taxa from families Ephydridae, Elmidae, Gomphidae, and genera Euthraulus, Neoperla, Orthothrichia and Prosopistoma were limited to the second-order stream sites while families Ceratopogonidae, Pisuliidae, Dytiscidae and genus Trichosetodes occurred exclusively in the first-order stream sites. Collector-filterers and collector-gatherers were the most abundant functional feeding groups (FFGs) in the two river systems. Scrapers were abundant in the second-order stream while shredders were abundant in the first order streams. The distinctness in the structural and functional composition of macroinvertebrates between the two river systems suggests that linkages among streams in a network as exemplified in the Nzoia River Basin, support and foster biodiversity.

Taphofacies of coastal lakes based on mollusk death assemblages: a case study of Mirim Lake

Mirim Lake is the second-largest lacustrine body in Brazil, stretching for some 185 km and covering about 375 thousand hectares of water surface. This lake is part of the Patos-Mirim System, one of the world’s largest complexes of coastal lagoons, which is the result of the rise and fall of sea level over transgressive-regressive cycles triggered by glacio-eustasy during the Late Pleistocene and Holocene. Its characteristics and dynamics give it singular importance for studies on the genesis of shell accumulation in lagoons. This study aims to improve the knowledge of how the taphonomic signatures reflect the environmental characteristics and dynamics of Mirim Lake. Categorization of the arrangement and packing of death assemblages, as well as the orientation of shells, supported the biostratinomical approach. The taphonomic signatures included disarticulation, fragmentation, and corrosion of shells. Corrosion is the primary damage observed in the bioclasts, varying from a single loss of color to complete degradation. Differences in the characteristics of death assemblages observed in the dune fields and the lacustrine plain led to the recognition of two taphofacies. A more significant number of whole shells was observed in the dune field taphofacies, while sharp fragments and open-articulated bivalves in hydrodynamic unstable positions characterize the lacustrine plain taphofacies. The genesis of death assemblages and the taphonomic signatures of bioclasts were linked to three sedimentary dynamics attributed to the environment of Mirim Lake. Keywords: biostratinomy, taphonomic signatures, shell deposits, dune field, lacustrine plain.

Survey of the fish fauna of the water bodies of the city of Kharkiv

The study of the biodiversity of urbanized landscapes, in the context of their permanent expansion, is becoming increasingly important as part of environmental management. The proposed review considers the history of the study and the results of modern research on the ichthyofauna of water bodies in and around the city of Kharkiv. The study includes data obtained during archeological excavations. The existing water fund is estimated as a habitat for fish in the city. We compiled a modern systematic list of the fish fauna, determined its place in the general zoogeographical zonation of the Palearctic, and analyzed the ecological and faunistic characteristics of the fish assemblages, which created a basis for a general assessment of the current state and prospects for changes in the fish community within the city. The state of recreational fishing in the waters of Kharkiv as the main type of utilization of fish resources on its territory is analyzed. The current fish fauna of the water bodies of Kharkiv and its environs consists of 32 species belonging to 31 genera, 11 families, 7 orders, and 4 superorders of bony fish, as well as one hybrid form of silver and bighead carps, whose abundance is maintained only by artificial introduction into water bodies outside Kharkiv with subsequent occasional migration to the city, and two diploid-polyploid hybridogenic complexes of fish of the genera Carassius and Cobitis, whose reproductive characteristics require further study. Five species have disappeared from the local fish fauna, i.e. four species of bony fish (common crucian carp Carassius carassius, Black Sea roach Rutilus frisii, asp Leuciscus aspius, Danilevsky's dace Leuciscus danilewskii) and the Ukrainian lamprey Eudontomyzon mariae, which used to live in the city or water bodies and watercourses of the adjacent territories. Thirteen fish species (41% of the total species composition) have a conservation status and require special measures for their protection according to national and international regulations. The share of non-native species in the ichthyofauna of Kharkiv is quite significant – eight species (22% of the total number of registered species and forms). The fish fauna of the city is dominated by freshwater fishes, limnophilic or indifferent to the current speed, with phytophilic or psammolithophilic portion spring and summer spawning, not belonging to any particular habitat.

Northward expansion of Cenozoic Asian humid climate recorded by sporopollen

The distribution pattern of arid–humid climate in the modern northwest–southeast confrontation in Asia evolved from the zonal distribution pattern of the Paleogene. However, this evolutionary process remains poorly constrained by geological evidence. In this paper, we analyze the characteristics of sporopollen assemblages recorded in Late Eocene strata of the Jianchuan Basin in southwest China. We show that vegetation patterns exhibited a remarkable shift from tropical–subtropical sparse forest to subtropical–temperate mixed broad-leaved–coniferous forest at ∼40.6 Ma; this shift is further indicated by the rapid decrease in drought-tolerant plants, mostly Ephedra and Chenopodiaceae, evidence that the previous hot–dry climate was replaced by a warm–humid climate at this time. This evidence suggests that the Asian monsoon began to affect the study area at ∼40.6 Ma. We then comprehensively integrated sporopollen results from several basins across East Asia, revealing that the frontal edge of the humid monsoon climate moved intermittently to the northwest after the Late Eocene, and may have advanced to the Lunpola–Lanzhou line by the early Late Oligocene, this being similar to the position of the leading edge of the modern monsoon. Moreover, the frontal edge of the humid monsoon climate may have extended as far as the Qaidam Basin during the Middle Miocene, but then gradually retreated to the position of the modern monsoon front. The uplift of the Tibetan Plateau and global climate change may have played dominant roles in this evolution.

Comparisons of Twelve Freshwater Mussel Bed Assemblages Quantitatively Sampled at a 15-year Interval in the Buffalo National River, Arkansas, USA

Historically, 23 freshwater mussel species have been documented from the Buffalo National River (BNR), a 246 km, free-flowing river in northern Arkansas. The potential threats to BNR include land use/land cover changes, eutrophication, recreation, physical habitat changes, and various climate change-related effects. Twelve quantitative mussel bed sites were established and then sampled using a stratified random sampling protocol to evaluate the long-term changes between 2006 and 2020–2021 in population and assemblage characteristics. We compared (1) overall mussel bed persistence, sampling confidence levels and study-wide relative abundances, and compared species’ size and size-frequency distributions; (2) 10 overall site assemblage variables using paired t-tests; (3) site-level mean density, richness, and diversity indices using pair-wise Mann–Whitney U statistics; and (4) assemblage composition using Non-Metric Multidimensional Scaling. The major findings included the following: (1) sampling efforts based on a targeted 80% confidence level appears relatively robust, (2) BNR mussel assemblage composition and structure were relatively stable (however, small mussel bed persistence is a concern), (3) 7 of 23 sites were outliers based on freshwater mussel composition and habitat characteristics, and (4) assemblage composition changed with three species declining (Actinonaias ligamentina, Lasmigona costata, and Ptychobranchus occidentalis) and four species increasing (Cambarunio hesperus, Cyclonaias tuberculata, Eurynia dilatata, and Venustaconcha pleasii) between monitoring events.

Foraminifera associated with macroalgae on tropical coastal sandstone reefs

While they are extremely abundant and ecologically important, the epiphytic foraminifera of tropical reefs are still poorly known. The present study describes the foraminiferal assemblages associated with macroalgae on tropical reefs of the Brazilian coast. Samples of four species of macroalgae, two foliose (Padina antillarum and Ulva lactuca) and two corticated (Palisada perforata and Gelidiella acerosa), were collected from intertidal sandstone reefs at Pina, Enseada dos Corais, and Toquinho (Northeastern Brazil). Overall, only 13.3% of the 708,754 foraminifera specimens were alive, belonging to 37 species, with dominance of Rosalina anglica. Most tests were hyaline-perforate and conical in shape, and most species were permanently or temporarily sessile. The majority of living foraminifera were attached to the surface of Palisada and Gelidiella, and no attached specimens were found in either Padina or Ulva. The species richness and abundance of the living foraminifera varied significantly among the macroalgae, occurring the high values in P. perforata. The assemblages varied significantly between the two species of corticated macroalgae, and between the corticated and foliose species, but not between the two foliose algae. Some of the specimens of Glabratella and Rosalina were reproducing, and had juveniles attached to the parental test. This is the first study to focus on the ecological interactions of the epiphytic foraminifera of the tropical southern Atlantic Ocean, and its results indicate that the characteristics of the epiphytic assemblages can be used as a proxy for the understanding of the structure and function of microbenthic communities on tropical reefs.

Characteristics of spider assemblages of subtropical rice paddy fields in the Yaeyama Islands, Japan

Spiders are important natural enemies of rice pests in paddy fields. To estimate their roles, it is essential to understand their functional diversity. However, little is known about the spider fauna of paddy fields in subtropical regions. Here, we investigated spider diversity and species composition in paddy fields in the Yaeyama Islands, in subtropical Japan. We collected 1489 individuals of at least 42 species in 13 families and 7 guilds from rice paddies on Ishigaki, Iriomote, and Yonaguni islands by net sweeping during the first and second crops from 2013 to 2015. The Tetragnathidae (39%), Araneidae (35%), and Thomisidae (18%) were the most abundant families, comprising > 90% of total abundance. Orb web weavers (73%) and ambush hunters (19%) were the most abundant guilds. The most common species were Neoscona theisi (Walckenaer, 1841) (Araneidae) (n = 352), Tetragnatha javana (Thorell, 1890) (Tetragnathidae) (n = 294), and Tetragnatha nitens (Audouin, 1826) (Tetragnathidae) (n = 94). The results show that the species composition of spiders in subtropical paddy fields is more similar to that in tropical paddy fields in Asia than to that in temperate paddy fields in mainland Japan. Ordination analysis showed that the composition of spiders on Ishigaki island varies greatly with season and year. This study makes a valuable contribution to knowledge of the comprehensive diversity of subtropical spiders associated with rice paddy fields in Japan.

Modern pollen assemblages from the hinterland of the Tibetan Plateau and their significance for reconstructions of past vegetation

We conducted a detailed field vegetation investigation combined with the collection of surface soil samples for pollen analysis in the alpine meadow and steppe vegetation zones (30 sites in each zone) in the hinterland of the Tibetan Plateau. Our objectives were to determine the source area of exotic pollen, the relationship between pollen percentages and the cover of the major plant taxa, and the characteristics of the pollen assemblages from surface soils and lake sediments and their vegetation significance. Our principal findings are: (i) the two vegetation zones are herbaceous although arboreal pollen types are present in the related pollen assemblages (2 and 16.8% in the alpine meadow and steppe zones, respectively); (ii) arboreal pollen is assumed to be transported mainly by the Indian monsoon from the forests of the southern Himalayan foothills or river valleys – the spatial distribution of the percentages and concentrations of arboreal pollen in the study sites shows that pollen concentrations have the strongest correlation with the Indian monsoon's variations; (iii) there are regional differences in (a) the relationship between pollen percentages and the cover of the main plant taxa and (b) the indicator plant taxa representative of pollen assemblages and vegetation types zones – the regional vegetation of the study region and pollen productivity variations between plant taxa are likely to be the main causes behind these differences; and (iv) the pollen assemblages from surface soils and lake sediments have similar characteristics and correspond well to the regional vegetation of the alpine meadow zone. In the alpine steppe zone, the pollen assemblages from surface soils and lake sediments are quite different, caused mainly by the over‐representation of Artemisia. Our study supplies a detailed description of pollen–vegetation relationships on the hinterland of the Tibetan Plateau and provides scientific references for interpreting stratigraphic pollen assemblages and reconstructing regional vegetation.

Modern pollen assemblages of agricultural land, wasteland, and natural vegetation in China and their significance for reconstructing the intensity of agricultural activity

Knowledge of the modern pollen assemblage characteristics of artificial and disturbed vegetation can help reconstruct changes in the intensity of human activity and land use/land cover (LULC) based on Holocene stratigraphic pollen records. We obtained pollen assemblage data from 217 agricultural land (cultivated cereals) sites, 79 wasteland sites, and 389 natural vegetation sites in different regions in China. The results show that the pollen of cereals Poaceae and the associated agricultural weeds in agricultural land and wasteland vegetation contexts are effective indicators of the intensity of agricultural activity, and that the pollen assemblages of natural vegetation accurately reflect the regional zonal vegetation composition. Although the cereals Poaceae proportion varied greatly among the agricultural sites in different regions, due to factors like cultivation practices, crop types, and terrain, all of them were significant indicators of agricultural activity. The pollen assemblages of wasteland and natural vegetation in different regions were also different, and the indicator taxa exhibit distinct zonal characteristics. There was no consistent linear relationship between cereals Poaceae proportion and the area of agricultural land. The cereals Poaceae proportion did not vary with increasing agricultural area in regions with higher or lower levels of agricultural production; only in Northeast and North China, when the agricultural area was below 60%, did the cereals Poaceae proportion increase with increasing agricultural area. These results provide a modern process basis for the use of stratigraphic pollen data to reconstruct past changes in agricultural activity and LULC.