Spatial Distribution Abundance Research Articles

The Gaia-ESO survey: Mapping the shape and evolution of the radial abundance gradients with open clusters

Context. The spatial distribution of elemental abundances and their time evolution are among the major constraints to disentangling the scenarios of formation and evolution of the Galaxy. Aims. In this paper we used the sample of open clusters available in the final release of the Gaia-ESO survey to trace the Galactic radial abundance and abundance-to-iron ratio gradients, and their time evolution. Methods. We selected member stars in 62 open clusters, with ages from 0.1 to about 7 Gyr, located in the Galactic thin disc at galactocentric radii (RGC) from about 6 to 21 kpc. We analysed the shape of the resulting [Fe/H] gradient, the average gradients [El/H] and [El/Fe] combining elements belonging to four different nucleosynthesis channels, and their individual abundance and abundance ratio gradients. We also investigated the time evolution of the gradients dividing open clusters in three age bins. Results. The [Fe/H] gradient has a slope of −0.054 dex kpc−1. It can be better approximated with a two-slope shape, steeper for RGC ≤ 11.2 kpc and flatter in the outer regions. We saw different behaviours for elements belonging to different channels. For the time evolution of the gradient, we found that the youngest clusters (age < 1 Gyr) in the inner disc have lower metallicity than their older counterparts and that they outline a flatter gradient. We considered some possible explanations, including the effects of gas inflow and migration. We suggest that the most likely one may be related to a bias introduced by the standard spectroscopic analysis producing lower metallicities in the analysis of low-gravity stars. Conclusions. To delineate the shape of the ‘true’ gradient, we should most likely limit our analysis to stars with low surface gravity log g > 2.5 and microturbulent parameter ξ < 1.8 km s−1. Based on this reduced sample, we can conclude that the gradient has minimally evolved over the time-frame outlined by the open clusters, indicating a slow and stationary formation of the thin disc over the last 3 Gyr. We found a secondary role of cluster migration in shaping the gradient, with a more prominent role of migration for the oldest clusters.

What is the role of disturbance in catalyzing spatial shifts in forest composition and tree species biomass under climate change?

Mounting evidence suggests that climate change will cause shifts of tree species range and abundance (biomass). Abundance changes under climate change are likely to occur prior to a detectable range shift. Disturbances are expected to directly affect tree species abundance and composition, and could profoundly influence tree species spatial distribution within a geographical region. However, how multiple disturbance regimes will interact with changing climate to alter the spatial distribution of species abundance remains unclear. We simulated such forest demographic processes using a forest landscape succession and disturbance model (LANDIS-II) parameterized with forest inventory data in the northeastern United States. Our study incorporated climate change under a high-emission future and disturbance regimes varying with gradients of intensities and spatial extents. The results suggest that disturbances catalyze changes in tree species abundance and composition under a changing climate, but the effects of disturbances differ by intensity and extent. Moderate disturbances and large extent disturbances have limited effects, while high-intensity disturbances accelerate changes by removing cohorts of mid- and late-successional species, creating opportunities for early-successional species. High-intensity disturbances result in the northern movement of early-successional species and the southern movement of late-successional species abundances. Our study is among the first to systematically investigate how disturbance extent and intensity interact to determine the spatial distribution of changes in species abundance and forest composition.

Intra-Decadal (2012-2021) Dynamics of Spatial Ichthyoplankton Distribution in Sevastopol Bay (Black Sea) Affected by Hydrometeorological Factors.

High mortality of fish in the early stages of ontogenesis requires the detection of factors affecting it and is an extremely important problem. For this reason, we tried to consider the influence of some hydrometeorological factors on the intra-decadal dynamics and spatial distribution of ichthyoplankton abundance in Sevastopol Bay. To this end, we analyzed ichthyoplankton samples collected in 2012−2021 in Sevastopol Bay, and the four districts were identified. The ichthyoplankton distribution by areas was associated with the peculiarities of the pollution distribution. The maximum numbers in eggs (34.7 ± 7.5 ind. m−2) and larvae (10.0 ± 2.4 ind. m−2) were recorded in July−August. For the first time, a positive effect of temperature and repeatability of north and northeast winds on the ichthyoplankton number during the summer spawning in all identified areas of Sevastopol Bay using principal component analysis (PCA) was reported. In the southern region, positive influence of temperature and northerly winds on the ichthyoplankton abundance was confirmed by ANOVA (p = 0.02), and Pearson’s correlation analysis revealed significant correlations between these parameters on inter-annual scale (r > 0.5). In the eastern area, the discharge of rivers is an additional factor affecting the abundance of ichthyoplankton, while in the western and central areas, these factors were the wind characteristics caused by the orography peculiarities. The pollution spread in Sevastopol Bay is also largely due to the wind regime. The importance of comprehensive monitoring studies using intra-decadal data on ichthyoplankton is emphasized.

Risk of eutrophication in the seawater of the coastal Red River aquaculture zone (Thai Binh province, Vietnam)

Coastal aquaculture represents an important economic activity in many countries. Nutrient (N, P and Si) concentrations and phytoplankton diversity and abundance in the coastal aquaculture zone, Tien Hai district, Thai Binh province (North Vietnam) were investigated during 2019–2020. Nutrient concentrations in five types of wastewater were also determined. The mean Eutrophication Index value of surface seawater at the 9 studied sites varied from 0.27 to 0.52, ranking as oligotrophic to mesotrophic. Five phytoplankton groups were observed (Bacillariophyceae (62% relative abundance), Dinophyceae (16%), Chlorophyceae (11%), Cyanobacteria (7%), and Euglenophyceae (4%)). The temporal and spatial distribution of phytoplankton diversity and abundance was governed by water temperature, pH, TSS, and TP and reflected the strong interactions between seawater and riverine water in the area. The presence of certain potentially toxic algal species combined with increasing inorganic nitrogen concentrations and N:P ratios further underlined the risk for harmful algal blooms. The investigation of different nutrient sources in this area revealed that while nitrate and total phosphorus concentrations are related to diffuse sources, point sources may be important in providing ammonium and dissolved phosphate concentrations to coastal seawater in this aquaculture zone. These results provide a scientific basis upon which better management strategies can be constructed in order to assure the sustainable development of aquaculture in the Red River coastal area, in particular, and in the coast of Vietnam, in general.

The coastal waters of the south-east Bay of Biscay a dead-end for neustonic plastics

Numerical models point to the south-east Bay of Biscay as a convergence area for floating particles, including plastics. The few existing studies on plastic abundance in the area mainly focus on open waters and yet information on the coastal area is limited. To fill this gap, neustonic samples were taken along the coastal waters of the south-east Bay of Biscay (2017–2020) to define the spatial distribution of plastic abundances and composition. Results show an average plastic abundance of 739,395 ± 2,625,271 items/km2 (998 ± 4338 g/km2). French waters were more affected, with five times higher plastic abundances than Spanish coasts. Microplastics represented 93 % of the total abundance of plastic items (28 % in weight), mesoplastics 7 % (26 %) and macroplastics 1 % (46 %). This study demonstrates that this area is a hotspot for plastic with levels in coastal waters similar to those in the Mediterranean Sea or other litter aggregation areas.

Diversity and longitudinal dynamics of benthic macro-invertebrate populations in the shallow zone of the Chari River at Sarh (Chad, Central Africa)

The biology of Chadian freshwater aquatic environments is little known and works on benthic macroinvertebrates dates back to at least the 1980s thanks to the work of the office for scientific and technical research overseas (ORSTOM). This study was carried out in the Chari River, Bahr Kôh Department (Moyen Chari) over a distance of 52 km on the edge of the town of Sarh in order to assess the family diversity of macroinvertebrates. Sampling was carried out in shallow environments with a weak current. A haze net constituted of a 1 m long sleeve and a collector with a circular opening of 30 cm diameter and a mesh size of 500 µm was used following the multi-habitat approach according to the Barbourt method adapted by Stark. Sampling was carried out on a monthly basis during the flood period from August to November 2020, which corresponds to the period of maximum lateral expansion of the Chari, and during the low-water period from February to May 2021, which corresponds to the period when the water level of the Chari reached its lowest point. The fauna surveyed is composed of 10464 individuals belonging to 98 families, 17 orders and 7 classes. Insects are the most represented and constitute 76.53% of the total richness of the macrofauna collected, followed by molluscs composed of 13.26%, including 9.18% of gastropods. Annelids, Crustacea and Chelicerata were the groups with the lowest number of individuals (of the population). Chironomidae and Dytiscidae had the highest total family richness, while Thiaridae was the most abundant family. The Kruskal-wallis test was applied to explain the good spatiotemporal diversity of the stands. Depending on the season, low diversity was observed at the end of low water and during high water. The high taxonomic richness of the entomofauna, dominated by pollutants, at stations where human activities are taking place indicates a state of disturbance linked to pollution. While the spatial distribution of total abundance was dominated by Molluscs (Thiaridae, Corbiculidae) in the downstream stations is explained by the mineralisation and enrichment in organic matter of these stations.

Effects of Pollution Control of Xiaoqing River on Environment Factors and Phytoplankton Community in the Laizhou Bay

The spatial distribution of environmental factors, chlorophyll a (Chla), phytoplankton abundance, and community structure in the Laizhou Bay were investigated in August 2018 (wet season after pollution control) to clarify the effects of the pollution control of the Xiaoqing River, which is a major source of pollution, on environmental factors and phytoplankton community structure in this area. The results showed that the environmental factors changed significantly after pollution control of the Xiaoqing River. The concentrations of dissolved inorganic nitrogen (DIN), dissolved inorganic silicon (DSi), NO3-, and NO2- decreased significantly, with values only 40.1% to 60.4% of those from the same period of in 2017 (the nearest year before the pollution control), whereas dissolved inorganic phosphorus (DIP) and NH4 increased by 2.5 and 1.4 times that of their concentrations in 2017. The spatial distribution of environmental factors changed significantly, with the nutrient concentrations around the Xiaoqing River estuary noticeably decreasing. The abundance of phytoplankton cells was 21.5×106 cell·m-3, which was close to the results of a previous study, whereas the ρ(Chla) was 2.43 μg·L-1, which decreased obviously. Both microscopic analysis and pigment taxonomy suggested that phytoplankton community structure in the Laizhou Bay changed clearly, with the dominant community shifting from diatoms alone to the co-dominance of diatoms and cyanobacteria. Chaetoceros curvisetus, Skeletonema costatum, and Cerataulina pelagica, which were commonly observed in the Laizhou Bay before pollution control of the Xiaoqing River, decreased in 2018, whereas the abundance of common dominant freshwater species (e.g., Merismopedia sp. and Synedra spp.) increased significantly. Redundancy analysis (RDA) showed that the phytoplankton community was significantly related to nitrogen, phosphate (negative correlation), and salinity (negative correlation) after pollution control of the Xiaoqing River, indicating that the variation in nutrient concentration and the structure of river runoff input may be the main factors affecting phytoplankton community and dominant species structure.

Imaging Mass Spectrometry Reveals Alterations in N-Linked Glycosylation That Are Associated With Histopathological Changes in Nonalcoholic Steatohepatitis in Mouse and Human

Nonalcoholic steatohepatitis (NASH) is the progressive form of nonalcoholic fatty liver disease (NAFLD) and is characterized by inflammation, hepatocyte injury, and fibrosis. Further, NASH is a risk factor for cirrhosis and hepatocellular carcinoma. Previous research demonstrated that serum N-glycan profiles can be altered in NASH patients. Here, we hypothesized that these N-glycan modifications may be associated with specific liver damage in NAFLD and NASH. To investigate the N-glycome profile in tissue, imaging mass spectrometry was used for a qualitative and quantitative in situ N-linked glycan analysis of mouse and human NAFLD/NASH tissue. A murine model was used to induce NAFLD and NASH through ad libitum feeding with either a high-fat diet or a Western diet, respectively. Mice fed a high-fat diet or Western diet developed inflammation, steatosis, and fibrosis, consistent with NAFLD/NASH phenotypes. Induction of NAFLD/NASH for 18 months using high caloric diets resulted in increased expression of mannose, complex/fucosylated, and hybrid N-glycan structures compared to control mouse livers. To validate the animal results, liver biopsy specimens from 51 human NAFLD/NASH patients representing the full range of NASH Clinical Research Network fibrosis stages were analyzed. Importantly, the same glycan alterations observed in mouse models were observed in human NASH biopsies and correlated with the degree of fibrosis. In addition, spatial glycan alterations were localized specifically to histopathological changes in tissue like fibrotic and fatty areas. We demonstrate that the use of standard staining’s combined with imaging mass spectrometry provide a full profile of the origin of N-glycan modifications within the tissue. These results indicate that the spatial distribution of abundances of released N-glycans correlate with regions of tissue steatosis associated with NAFLD/NASH.

Statistical methods for predicting the spatial abundance of reef fish species

Understanding the spatial distribution of organism abundance is fundamental to assessing and managing ecological populations. Marine species can be difficult and logistically challenging and expensive to observe. This often results in spatial data containing low detection rates when sampling underwater, biasing spatial predictions from many modeling approaches. We propose a multistage statistical workflow that can use zero inflated sampling data to develop non-linear predictive spatial distributions of reef fish abundance. The workflow includes: (1) an individual-based discrete event simulation which generates simulated survey data under different abundance settings; (2) empirical maximum likelihood analysis to establish the relationship between survey data and abundance from the simulation; (3) a two-step random smoothing method to estimate reliable block spatial abundance around each survey station; (4) an ensemble of different machine learning models which use the estimated abundance from step three as input to compute a stable non-linear prediction of abundance across the entire study area (Gulf of Mexico). Applying our workflow greatly improved the ability to forecast abundance at small spatial scales. The ability to forecast at fine spatial scales is critical when working with species that are patchily distributed. This workflow can apply to many ecological populations to develop abundance maps even if sample data is not well distributed across the study area or is zero inflated.

Seasonal and interannual variations of the abundance of the dinoflagellate Noctiluca scintillans in the northern Black Sea

ABSTRACT Noctiluca scintillans (Macartney) Kofoid and Swezy, 1921 contributes ∼ 85% of the total biomass of heterotrophic plankton in Crimean coastal waters. Data for the retrospective analysis come from a 20-year sampling (in 2000s) across the Crimean shelf and in adjacent open sea waters. Samples were collected onboard research vessels, in the upper 150 m layer, by Juday nets (vertical hauls) fitted with 145 µm mesh. These data were compared to field surveys of the 1960s. Seasonal blooms of Noctiluca were pronounced during summer time, with the peak of abundance in June. The mesoscale spatial distribution of Noctiluca abundance was most heterogeneous in June as well. The annual concentration of cells in coastal waters exceeded that of the open sea by four times. The coefficient of Noctiluca seasonal abundance variation in coastal waters was 1.5 times higher than that of the open sea. The Principal Component Analysis implied that the seasonal variation of the Noctiluca abundance offshore was modulated by coupling of the atmospheric precipitation, sea surface temperature, photosynthetically active radiation, euphotic depth, chlorophyll-a concentration, Noctiluca abundance in coastal waters, mesoscale eddies and wind stress. A general decline of Noctiluca abundance and biomass was observed in coastal waters, from the 1960s to the present.

Coastal Mesozooplankton Assemblages during Spring Bloom in the Eastern Barents Sea.

Simple SummaryArctic coastal waters have been strongly influenced by climatic fluctuations during the past decades. Recent studies reported clear warming processes in the Barents Sea and adjacent waters. Plankton assemblages are good indicators of environmental changes, and their composition and production affect all components of pelagic ecosystems. Most of data on the zooplankton in Arctic seas were obtained during summer seasons, and little is known about zooplankton communities in other seasons. Spring is one of the crucial periods in the Arctic marine environment, as primary production may reach the annual maximum. To investigate a spring pattern of Arctic mesozooplankton, we performed a study in the eastern Barents Sea. This research is the first report on the spring coastal zooplankton near the Novaya Zemlya Archipelago. We revealed high diversity and abundance of zooplankton taxa. Environmental variability had a significant impact on the mesozooplankton assemblages, with geographical location and phytoplankton density being the most important. Our data may be useful for future investigations dealing with Arctic plankton communities during the era of global climatic changes.Mesozooplankton play an important role in Arctic shelf ecosystems as a trophic link and a key food source for many larval fish species. The distribution of mesozooplankton in the eastern Barents Sea was studied along a 500 nautical mile-long transect in May 2016 during the spring bloom. Mesozooplankton were sampled using a Juday net hauled from the surface to the bottom at 12 stations. We found good correspondence between the distribution of water masses and mesozooplankton assemblages. Mesozooplankton abundance (mean 73·103 individuals m−2) in Novaya Zemlya coastal water was dominated by Copepoda ova and nauplii, Thyssanoessa spp. nauplii and Oithona similis. Parasagitta elegans and Calanus finmarchicus comprised most of the total mesozooplankton biomass (mean 0.9 g dry mass m−2) in that water mass. A second assemblage (mean abundance 171·103 individuals m−2) was associated with the colder Barents Sea water, with Oithona similis, Copepoda nauplii, Fritillaria borealis and Cirripedia nauplii being the most numerous. In that water mass, C. finmarchicus, Metridia longa, Cirripedia nauplii and Calanus glacialis contributed most to the total biomass (mean 3 g dry mass m−2). The dominance of young stages of Copepoda and a high proportion of meroplankton were typical of spring mesozooplankton assemblages. The spatial distribution of mesozooplankton abundance and biomass was strongly correlated with latitude, longitude and chlorophyll a concentration, which together explained 10% of the total variance in mesozooplankton density. The present investigation is a baseline study for the assessment of the spring mesozooplankton assemblage in the eastern Barents Sea, and for an evaluation of the possible impact of future environmental changes on the Arctic shelf marine ecosystem.

Quantitative paleoecology of Cambrian (Series 2–Miaolingian) communities from central Sonora, Mexico

This work presents a paleoecological approach to study benthic communities preserved in Cambrian strata exposed at the Sahuaral locality in central Sonora, northwestern Mexico. Based on species richness and abundance, this work analyzed 627 individuals corresponding to 33 species from five distinctive Cambrian formations: the lowermost Proveedora Formation characterized by bioturbation horizons that record the occurrence of a benthic-infaunal biota from coastal shallow seas, followed by the Buelna Formation which contains reef deposits dominated by autotrophic epibenthic communities. The Cerro Prieto Formation was deposited in a high-energy shallow marine environment, dominated by primary consumers-epifaunal and suspensions feeders. The uppermost unit, the El Gavilán Formation, is an intercalation of shale and fossiliferous limestone characterized by the fossil remains of suspension feeders, detritus feeders and nektobenthic organisms of low energy deep water environments. The paleobiota consist of ichnofossils, microbial oncolites, chancellorids, brachiopods, hyolithids, and trilobites in a sequence of increasing diversity and complexity. Paleoecological indices (Simpson Dominance, Shannon-Weaver Index, Evenness Index, and Total Richness) were determined and compared in the study area. In addition, the effective number of species and the true diversities were obtained, which are similar between each station distributed in each formation. However, it is possible that the high degree of dominance is a factor to indicate an inequality between the true diversity and the species richness identified. These results provide new analytical and paleoecological criteria for better understanding depositional environments and fossil associations where the spatial distribution of benthic organisms, richness and abundance provide a valued window to Cambrian biotas. The structure of the marine community of the El Sahuaral area has a great affinity with other Cambrian communities, such as those from the Stephen Formation (Burgess Shale, British Columbia) and the Chengjiang biota of the Yangtze Shelf deposits in South China.

Distribution and Dimethylsulfoniopropionate Degradation of Dimethylsulfoniopropionate‐Consuming Bacteria in the Yellow Sea and East China Sea

AbstractThe fate of dimethylsulfoniopropionate (DMSP), the precursor of the climatologically important gas dimethylsulfide (DMS), depends on the structure of marine communities. DMSP degradation by DMSP‐consuming bacteria (DCB) is an important sink of dissolved DMSP (DMSPd) in seawater. DMSP cleavage and demethylation are two DMSPd consumption pathways, and the DMSPd cleavage pathway involves DMSP lyase activity (DLA). Here, we studied the distribution of DMS, DMSP, DCB, and DLA in the seawater of the Yellow Sea and East China Sea in the summer of 2013 and the degradation of DMSPd by DCB. High DCB abundances, as well as DMS and dissolved, particulate, total DMSP (DMSPd,p,t) concentrations were observed near the Hongzhou Bay, which may be due to the high productivity of dinoflagellates. The spatial distribution of DCB abundance was most likely the result of the regional hydrography including upwelling near Hangzhou Bay and the discharge of Yangtze Diluted Water (YDW). The DLA along the YDW decreased from coastal water to open sea. The DMSPd consumption by DCB Bacillus sp. YES023 isolated from the seawater was accompanied by DMS production (≤8.2% of DMSPd consumption). Bacillus sp. YES023 could also grow using glycine betaine, acrylic acid, dimethylsulfoxide, monomethylamine, or dimethylamine as a sole carbon source. Glycine betaine and acrylic acid were the most favorable substrates for overall growth. These results help our understanding of bacterial catabolism and the degradation pathways of methyl sulfur compounds in the ocean.

ATOMIUM: halide molecules around the S-type AGB star W Aquilae

Context. S-type asymptotic giant branch (AGB) stars are thought to be intermediates in the evolution of oxygen- to carbon-rich AGB stars. The chemical compositions of their circumstellar envelopes are also intermediate but have not been studied in as much detail as their carbon- and oxygen-rich counterparts. W Aql is a nearby S-type star, with well-known circumstellar parameters, making it an ideal object for in-depth study of less common molecules. Aims. We aim to determine the abundances of AlCl and AlF from rotational lines, which have been observed for the first time towards an S-type AGB star. In combination with models based on PACS observations, we aim to update our chemical kinetics network based on these results. Methods. We analyse ALMA observations towards W Aql of AlCl in the ground and first two vibrationally excited states and AlF in the ground vibrational state. Using radiative transfer models, we determine the abundances and spatial abundance distributions of Al35Cl, Al37Cl, and AlF. We also model HCl and HF emission and compare these models to PACS spectra to constrain the abundances of these species. Results. AlCl is found in clumps very close to the star, with emission confined within 0′′.1 of the star. AlF emission is more extended, with faint emission extending 0′′.2 to 0′′.6 from the continuum peak. We find peak abundances, relative to H2, of 1.7 × 10−7 for Al35Cl, 7 × 10−8 for Al37Cl, and 1 × 10−7 for AlF. From the PACS spectra, we find abundances of 9.7 × 10−8 and ≤10−8, relative to H2, for HCl and HF, respectively. Conclusions. The AlF abundance exceeds the solar F abundance, indicating that fluorine synthesised in the AGB star has already been dredged up to the surface of the star and ejected into the circumstellar envelope. From our analysis of chemical reactions in the wind, we conclude that AlF may participate in the dust formation process, but we cannot fully explain the rapid depletion of AlCl seen inthe wind.

Influence of Spatial Scale Selection of Environmental Factors on the Prediction of Distribution of Coilia nasus in Changjiang River Estuary

An estuary region is a complex environment with a transition from fresh to brackish to salt water, and in which some environmental factors change dramatically over small ranges. Therefore, it is important to understand the impact of the selection of spatial scale on the prediction of the distribution of estuarine species. As the largest estuary in China, the Changjiang River estuary is the spawning ground, feeding ground, and migration channel for many species. Based on Coilia nasus, an important economic fish species in the Changjiang River estuary, this study uses the two-stage generalized additive model (GAM) to investigate the potential differences in the response of species’ spatial distribution when environmental factors are assessed at different spatial scales (1′ × 1′, 2′ × 2′, 3′ × 3′, 4′ × 4′, 5′ × 5′). The results showed the following: (1) according to the analysis of the variance inflation factor (VIF), the values of all environmental factors were less than three and we found no correlation among the environmental variables selected. (2) The first stage GAM retained six variables, including year, month, latitude (Lat), water depth (Depth, m), bottom salinity (Sal, mg/L), and chemical oxygen demand (COD, mg/L). The second stage GAM retained four variables, including Year, Lat, pH, and chlorophyll a (Chl-a, μg/L). (3) The mean value of the Chla for the 3′ × 3′ spatial scale was significantly lower than that of the other spatial scales, and the mean value of Sal for the 5′ × 5′ spatial scale was higher than that of the other spatial scales. (4) In terms of the spatial distribution of abundance, the distribution patterns of C. nasus predicted by all scales were not very similar, and the distribution patterns predicted by the 5′ × 5′ scale, in the autumn of 2012, were significantly different from those at other scales. Therefore, the selection of spatiotemporal scales may affect predictions of the spatial distributions of species. We suggest that potential spatiotemporal scale effects should be evaluated in future studies.

Forager Mobility and Lithic Discard Probability Similarly Affect the Distance of Raw Material Discard from Source

The neutral model of stone procurement developed by Brantingham (2003, 2006) provides a formal means to investigate the formation of lithic discard patterning under changing forager mobility conditions. This study modifies Brantingham's (2006) Lévy walk model to examine the influence of discard probability on the spatial distribution of raw material abundance. The model outcome shows that forager movement and tool discard probability have similar effects on the simulated patterns of raw material transport, so it is difficult—if not impossible—to differentiate the respective influence of the two factors from distance to source distributions alone. This finding of equifinality complicates the task of interpretating hominin mobility from archaeological distance to source data, particularly in settings such as the Middle-Upper Paleolithic transition, which is marked by an important reorganization in hominin lithic technology that may have affected stone tool discard probability.

Spatial Distribution of Arctic Bacterioplankton Abundance Is Linked to Distinct Water Masses and Summertime Phytoplankton Bloom Dynamics (Fram Strait, 79°N).

The Arctic is impacted by climate warming faster than any other oceanic region on Earth. Assessing the baseline of microbial communities in this rapidly changing ecosystem is vital for understanding the implications of ocean warming and sea ice retreat on ecosystem functioning. Using CARD-FISH and semi-automated counting, we quantified 14 ecologically relevant taxonomic groups of bacterioplankton (Bacteria and Archaea) from surface (0–30 m) down to deep waters (2,500 m) in summer ice-covered and ice-free regions of the Fram Strait, the main gateway for Atlantic inflow into the Arctic Ocean. Cell abundances of the bacterioplankton communities in surface waters varied from 105 cells mL–1 in ice-covered regions to 106 cells mL–1 in the ice-free regions. Observations suggest that these were overall driven by variations in phytoplankton bloom conditions across the Strait. The bacterial groups Bacteroidetes and Gammaproteobacteria showed several-fold higher cell abundances under late phytoplankton bloom conditions of the ice-free regions. Other taxonomic groups, such as the Rhodobacteraceae, revealed a distinct association of cell abundances with the surface Atlantic waters. With increasing depth (>500 m), the total cell abundances of the bacterioplankton communities decreased by up to two orders of magnitude, while largely unknown taxonomic groups (e.g., SAR324 and SAR202 clades) maintained constant cell abundances throughout the entire water column (ca. 103 cells mL–1). This suggests that these enigmatic groups may occupy a specific ecological niche in the entire water column. Our results provide the first quantitative spatial variations assessment of bacterioplankton in the summer ice-covered and ice-free Arctic water column, and suggest that further shift toward ice-free Arctic summers with longer phytoplankton blooms can lead to major changes in the associated standing stock of the bacterioplankton communities.

Abundance and spatial distribution of marine debris on the beach of Takalar Regency, South Sulawesi

This study aimed to map the spatial distribution of marine debris abundance in the beach area of Takalar Regency, South Sulawesi Province, Indonesia. This research was conducted during the east monsoon in August-September 2019 and July-August 2020. The data were collected from the beach of Takalar at 2 stations; station 1 in Punaga River Estuary and station 2 in Laikang Bay, with 3 replications per station. Sampling was carried out using the transect method, the length of the transect line is 100 meters parallel to the coastline. Samples were collected within the criteria of macro size (> 2.5 cm - 1 m) and meso size (> 5 mm - 2.5 cm). The results showed that the average total abundance of marine debris in the macro size category was 0.036 items/m2 and in the meso size was 0.0012 items/m2; while the average weight abundance of macro and meso marine debris respectively were 0.36 g/m2 and 0.0013 g/m2. The spatial distribution showed that the greatest abundance of macro and meso waste was found at station 2 or around Laikang Bay. The semi-enclosed water in Laikang Bay is linked to the high accumulation of debris in the location.

Predicting spatial patterns of soil bacteria under current and future environmental conditions

Soil bacteria are largely missing from future biodiversity assessments hindering comprehensive forecasts of ecosystem changes. Soil bacterial communities are expected to be more strongly driven by pH and less by other edaphic and climatic factors. Thus, alkalinisation or acidification along with climate change may influence soil bacteria, with subsequent influences for example on nutrient cycling and vegetation. Future forecasts of soil bacteria are therefore needed. We applied species distribution modelling (SDM) to quantify the roles of environmental factors in governing spatial abundance distribution of soil bacterial OTUs and to predict how future changes in these factors may change bacterial communities in a temperate mountain area. Models indicated that factors related to soil (especially pH), climate and/or topography explain and predict part of the abundance distribution of most OTUs. This supports the expectations that microorganisms have specific environmental requirements (i.e., niches/envelopes) and that they should accordingly respond to environmental changes. Our predictions indicate a stronger role of pH over other predictors (e.g. climate) in governing distributions of bacteria, yet the predicted future changes in bacteria communities are smaller than their current variation across space. The extent of bacterial community change predictions varies as a function of elevation, but in general, deviations from neutral soil pH are expected to decrease abundances and diversity of bacteria. Our findings highlight the need to account for edaphic changes, along with climate changes, in future forecasts of soil bacteria.

Population Characteristics of Brachionus calyciflorus and Their Potential Application for Evaluating River Health in the Pearl River Delta, China

Water pollution can be monitored through the use of indicator species, including Brachionus calyciflorus. To do this, it is necessary to understand the species’ population ecology. Four surveys of zooplankton were conducted in May, August, and December 2018 and February 2019 in the Pearl River Delta, China, to examine the population characteristics of B. calyciflorus. The temporal and spatial distribution of abundance, biomass, dominance, and occurrence frequency were compared with those from 2012 to investigate the relationship between changes in the population of B. calyciflorus and environmental factors. The average abundance, dominance, and occurrence of B. calyciflorus in this survey were significantly higher than those of 2012 in all seasons. Principal component analysis showed that environmental factors such as the temperature, transparency, total nitrogen, and total phosphorus of water had a major impact on the abundance of B. calyciflorus. There was a significant positive correlation with transparency, total nitrogen, and total phosphorus of water, and a very significant positive correlation with water temperature. Overall, these results demonstrated that the distribution characteristics of B. calyciflorus can reflect pollution in water bodies and can be used to evaluate water quality. These research results provide a reference for evaluating China’s river health and can help to manage water quality in the Pearl River Delta.