Seasonal Variation In Abundance Research Articles

New insights into the long-term dynamics and deposition-suspension distribution of atmospheric microplastics in an urban area

Atmospheric microplastics (AMPs) transmitted through the atmosphere are critical to global microplastic pollution. However, little is known about the long-term dynamics and distribution patterns of deposited (DAMPs) and suspended (SAMPs) AMPs. In this study, simultaneous sampling was conducted over one year to examine the deposition-suspension distribution of AMPs. Monthly and seasonal variations in abundance were evident, with an annual average of 302.31 ± 107.40 items/m2/day for DAMPs and 1.31 ± 0.62 items/m3 for SAMPs. The dynamics of DAMP and SAMP abundance demonstrated the dynamic distribution of AMPs between deposition and suspension. Both meteorological factors and particle features were found to influence the AMP distribution, manifesting as morphological differences and abundance variations. AMPs were most likely derived from traffic, industry, construction, and synthetic textiles, with diverse source areas up to 1750 km away. The estimated deposition flux of 7.28 × 1014 items per year and inhalation exposure of up to 12,777 items per year highlight the potential ecological and health risks of AMPs.

Seasonal distribution of microplastics in the surface waters of the Yellow Sea, China

Different studies are filling the gaps in the distribution map of global marine microplastics. However, the data on the seasonal variation is relatively limited, which may lead to overestimation or underestimation of the distribution level of microplastics. To understand baseline data and seasonal variations of the microplastics in the surface seawater of the Yellow Sea, a survey over four seasons was conducted during 2017–2018. Microplastics were collected using a 330 μm manta net. It was found that the abundance of microplastics was 0.63 ± 0.57 particles/m3. The seasonal abundance variation was spring > summer ≈ winter > autumn. The main categories were foam, line, and fragments, accounting for 32 %, 19 %, and 19 % of the total amount, respectively, and the dominant components were polypropylene, polyethylene, and polyethylene terephthalate, accounting for 38 %, 22 %, and 22 % of particles, respectively. The factors affecting the variation included wind-induced mixing, river input, and environmental topography.

Northward movement of the tropical dinoflagellate Ornithocercus and Triposolenia genera in Korean coastal waters is strongly associated with the inflow of the Jeju Warm Current

Rising seawater temperatures are causing geographic shifts in the composition and abundance of the marine plankton that make up the microbial food web. Over the past few years, the water temperature around the Korea Strait has been increasing rapidly. Twelve cruise surveys were conducted in the Jeju Strait between 2017 and 2019 to monitor the presence of the tropical dinoflagellate genera Ornithocercus and Triposolenia, which are brought in by the Jeju Warm Current. Additionally, passive tracer experiments were performed using the Regional Ocean Modeling System to understand how the warm currents impact the Jeju Strait. The results of these simulations were then compared against the distribution ranges and abundance of Ornithocercus and Triposolenia. The study found that there were significant seasonal variations in abundance and spatial distribution of the tropical dinoflagellates during the sampling period, particularly during September and November when they were highly abundant and widely distributed. These patterns were closely related to the intensity and path of the Jeju Warm Current, particularly from southeastern offshore (EKB02; Eastern Kuroshio Branch02) rather than from southwestern offshore (EKB01; Eastern Kuroshio Branch01) of Jeju Island. The study also found no tropical dinoflagellates at any of the stations near the south coast of Korea during the sampling period. These findings suggest that the Ornithocercus and Triposolenia tropical dinoflagellate genera may serve as useful biological indicators to monitor the advection of warm currents into the Jeju Strait, Korea.

ForamEcoGEnIE 2.0: incorporating symbiosis and spine traits into a trait-based global planktic foraminiferal model

Abstract. Planktic foraminifera are major marine calcifiers in the modern ocean, regulating the marine inorganic carbon pump, and generating marine fossil archives of past climate change. The foraminifera contain ecogroups with and without spines and algal symbionts, creating functional trait diversity which expands their ecological niches. Here, we incorporate symbiosis and spine traits into the symbiont-barren non-spinose foraminifer functional type in EcoGEnIE to represent all the extant foraminifera species. We calibrated the modelled new traits using Latin hypercube sampling (LHS) and identified the optimal model parameters from an ensemble of 1200 runs compared with global observations from core-top sediment samples, sediment traps, and plankton nets. The model successfully describes the global distribution and seasonal abundance variation of the four major foraminiferal functional groups. The model reproduces the dominance of the symbiont-obligate group in subtropical gyres and of the symbiont-barren types in the productive subpolar oceans. Global annual mean biomass and foraminifer-derived carbon export rate are correctly predicted compared to data, with biomass ranging from 0.001 to 0.010 mmol C m−3 and organic carbon export 0.002–0.031 mmol C m−2 d−1. The model captures the seasonal peak time of biomass and organic carbon export but struggles to reproduce the amplitude of both in productive areas. The sparseness and uneven distribution of observations and the model's limitation in upwelling regions likely contribute to this discrepancy. Our model overcomes the lack of major groups in the previous ForamEcoGEnIE 1.0 version and offers the potential to explore foraminiferal ecology dynamics and its impact on biogeochemistry in modern, future, and paleogeographic environments.

Seasonal variation in abundance and blood meal sources of primary and secondary malaria vectors within Kilombero Valley, Southern Tanzania

BackgroundExisting control tools have significantly reduced malaria over the past two decades. However, progress has been stalled due to increased resistance in primary vectors and the increasing role of secondary vectors. This study aimed to investigate the impact of seasonal change on primary and secondary vector abundance and host preference. Understanding the impact of seasonal dynamics of primary and secondary vectors on disease transmission will inform effective strategies for vector management and control.MethodsVector abundance was measured through longitudinal collection of mosquitoes, conducted monthly during the wet and dry seasons, in Sagamaganga, a village in the Kilombero Valley, Tanzania. Mosquitoes were collected indoors using CDC light traps and backpack aspirators, and outdoors using resting buckets baited with cattle urine. In addition, a direct measure of host preference was taken monthly using human- and cattle-baited mosquito electrocuting traps. A host census was conducted to provide an indirect measure of host preference together with monthly blood meal source analysis. All collected mosquitoes were assayed for Plasmodium sporozoites.ResultsA total of 2828 anophelines were collected, of which 78.5% and 21.4%, were primary and secondary vectors, respectively. The abundance of the primary vectors, Anopheles arabiensis and Anopheles funestus, and of the secondary vectors varied seasonally. Indirect measures of host preference indicated that all vectors varied blood meal choice seasonally, with the direct measure confirming this for An. arabiensis. All anopheline mosquitoes tested negative for sporozoites.ConclusionsAt the study location, the abundance of both primary and secondary vectors changed seasonally. Indirect and direct measures of host preference demonstrated that An. arabiensis varied from being zoophilic to being more opportunistic during the wet and dry seasons. A similar trend was observed for the other vectors.Graphical

Phenology of two scale insects, Coccus hesperidum and Icerya purchasi (Hemiptera: Coccomorpha) on Citrus in Mostaganem, Algeria

In Mazagran, Mostaganem Province, Algeria, the seasonal variation in abundance of the scale insects (Hemiptera: Coccomorpha) Coccus hesperidum LINNAEUS, 1758 (Coccidae) and Icerya purchasi MASKELL, 1879 (Monophlebidae) was studied in an orchard on two host plant species, orange ( Citrus sinensis) and lemon ( C. limon) between December 2018 and November 2019. Every ten days, samples of leaves were collected for monitoring insect numbers. In C. hesperidum on orange and lemon trees respectively, there were three or four population peaks annually (P<0.0001). In I. purchasi, there were three generations annually (P<0.0001). In both scale insect species their abundance was correlated with temperature (P<0.0001 for C. hesperidum, and P=0.010 for I. purchasi) but not with relative humidity levels. Lemon trees had the higher scale insect abundance on 50% of days sampled, for both C. hesperidum and I. purchasi (P<0.005), whereas orange had lower numbers of both scale species. C. hesperidum and I. purchasi occurred on all three sample plots; numbers of both species (particularly C. hesperidum) showed a positive relationship with wind speed (P<0.0001 and P=0.002, respectively), as strong winds probably picked up and carried crawlers into the sample plots situated downwind.

Linked seasonality between a phoretic mite and its moth fly host (Parasitiformes: Mesostigmata and Diptera: Psychodidae)

Phoresy is a widespread phenomenon in mites. It allows mesostigmatid mites that are associated with ephemeral habitats such as mammal dung to travel fast on larger animals that can detect a proper habitat from a greater distance. To address the gap in knowledge on phoresy in these mites, we examined host specificity in phoretic Mesostigmata associated with psychodid species and studied temporal dynamics to see if phoretic life cycles are synchronized with the host life cycle. Using a field collection of more than 2500 moth flies (Psychodidae) from eight localities in Norway, we found three out of 29 species carrying phoretic mites of two species: deutonymphs of Trachygamasus ambulacralis were phoretic on female Psychoda phalaenoides and both sexes of Psychoda grisescens, and adults of Iphidozercon gibbus were phoretic on females of Psychoda satchelli. All flies were species with larval development in vertebrate dung. Abundances of P. phalaenoides and T. ambulacralis were highly correlated, probably due to the two species exhibiting similar seasonal variations in abundance; both were significantly seasonal with a peak in August and September. Thus, T. ambulacralis infestation levels on P. phalaenoides appeared similar throughout the season. We discuss the implications for the life histories of the mites in question. Trachygamasus ambulacralis is first time recorded from Norway.

한국 서해안 곰소만에서 곰소옆새우 Sinocorophium homoceratum (Yu, 1938)의 계절별 현존량 변동 및 염분 내성

The physiochemical factors and seasonal variation in abundance of Sinocorophium homoceratum were examined at the intertidal flat in Gomso Bay, west coast of Korea, for one year. The salt tolerance of S. homoceratum was also investigated in the laboratory. S. homoceratum showed relatively high density in spring and summer, which were relatively high temperature (12 - 28°C) and low salinity (20.0 - 22.0 psu), and the lowest density in winter, which was low temperature (5°C or less) and high salinity (30-32 psu). Although immature individuals appeared throughout the year and juveniles did in all seasons except winter, ovigerous females were only collected from April to June. Relative growth of the head length and head width against the body length was best described by the primary regression equation. In experiments on salt tolerance in S. homoceratum, all individuals died after 24 hours at 0 psu. Six days after the start of the experiment, its survival rates (20.0 - 22.2%) at 28 - 35 psu were significantly lower than those (80.0 -82.3%) at 7 - 21 psu. The results of this study suggest that S. homoceratum is a species well adapted to estuarine mudflat by digging burrows in a silt mudflat and maintaining a relatively high density in all seasons except winter.

Seasonal mesozooplankton patterns and timing of life history events in high-arctic fjord environments

Seasonal patterns in mesozooplankton composition, vertical distribution, and timing of reproduction are challenging to study in the open sea due to ocean currents and mix of populations of different origins. Sill fjords, on the other hand, with restricted water exchange, are ideal locations for studying taxa- and community-specific adaptations to the prevailing environment. Here, we present re-occurring patterns in the mesozooplankton community structure in Billefjorden, Svalbard, a high Arctic sill fjord with extensive seasonal ice cover, based on monthly sampling from 2011 to 2013. The zooplankton community composition confirmed the Arctic character of this fjord. Predominantly herbivorous taxa, such as Calanus glacialis and Pseudocalanus spp., showed strong seasonal variation in abundance and depth distribution, with population minima in spring being compensated by a rapid population recovery during summer. Omnivorous taxa, such as Microcalanus spp. and copepods of the family Aetideidae, largely remained at depth throughout the year and had an extended or year-round reproductive period. Deep-dwelling omnivorous/carnivorous species peaked in abundance in winter–spring when herbivorous populations were severely depleted. Taxa with seasonally limited occurrences, i.e., meroplankton, peaked in spring and summer at the surface, but were largely absent for the rest of the year. The different life histories, with contrasting feeding modes, depth preferences, and timing of reproduction lead to reduced interspecies competition and allow for a rather high and stable abundance of mesozooplankton year-round despite the short primary production window at high latitudes.

Antibiotic resistance genes and their links with bacteria and environmental factors in three predominant freshwater aquaculture modes

Rapid development of aquaculture industry and increasing demand of various inputs (especially antibiotics), are suspected to promote the occurrence and spread of ARGs in aquaculture related environments. However, the occurrences of ARGs under different freshwater aquaculture practices are rarely known. Here, we investigated the seasonal profiles of the main ARGs, intI1 and bacteria in waters from three kinds of predominant freshwater aquaculture practices around the Honghu Lake (China), as well as their co-occurrences and interrelationships with antibiotics, heavy metals and general water quality. The results indicate that quinolone resistance genes (qnrB), tetracycline resistance genes (tetB and tetX) and sulfonamide resistance genes (sul1 and sul2) were the top five predominant ARGs with seasonal variations of abundance. Fish ponds were of the highest absolute abundances of tested ARGs than the other two modes. Crayfish ponds and their adjacent ditches shared similar ARGs profile. Different subtypes of ARGs belonging to the same class of resistance were varied in abundances. Some bacteria were predicted to carry different ARGs, which indicating multi-antibiotic resistances. Moreover, the combined environmental factors (antibiotics, heavy metals and water quality) partially shaped the profiles of ARGs and bacteria composition. Overall, this study provides new comprehensive understanding on the characterization of ARGs contamination in different freshwater aquaculture practices from the perspectives of environmental chemistry, microbiology and ecology. The results would benefit the optimization of aquaculture practices toward environmental integrity and sustainability.

Seasonality of benthic microalgal community abundance in shallow shelf waters

Benthic microalgae (BMA) are an abundant and common component of the illuminated surface sediments of shallow continental shelves worldwide. Although phytoplankton biomass, community composition, and productivity are relatively well documented for these habitats, little is known about the community dynamics of BMA in these systems. We determined the community composition and seasonal abundance of BMA in the surface sediments of shallow (ca. 10–13 m) nearshore shelf waters off Charleston, SC. Our primary hypothesis was that BMA exhibit seasonality in abundance and, similarly, abundance is correlated with bottom water temperatures. BMA had a high spatial variability (CV = 20–50%) over m to km scales. BMA biomass in the upper 1 cm of sediments exceeded phytoplankton by a factor of 3 and was composed primarily of diatoms with cyanobacteria and green microalgae (chlorophytes & euglenophytes) as common, but relatively minor components. The BMA community exhibited a seasonal variation in abundance that was positively correlated with bottom water temperature. The highest abundances occurred in the summer months, peaking in August. This study is the first to report the monthly to annual spatiotemporal dynamics of BMA in the nearshore shelf waters of the South Atlantic Bight and offers insights in the potential contribution of BMA to shelf primary productivity.

Spatial and temporal distribution of mesozooplankton in the coastal waters of Cyprus (Eastern Mediterranean)

This study provides elements on the spatial and temporal mesozooplankton variability during a three-year study, encompassing vertical hauls from 50 m deep to the surface from four coastal locations of Cyprus. The total mesozooplankton abundance fluctuated between 190.4 and 882.5 individuals m-3. A total of 90 holoplanktonic and meroplanktonic taxa were recorded. Copepods dominated in the community and accounted for 71.7% of the total mesozooplankton, followed by appendicularians, molluscs, cladocerans, and siphonophores, which contributed 8.04%, 5.48%, 4.60%, and 3.31%, respectively. There were no statistically significant differences among the four sampling sites for any of the mesozooplanktonic taxa, though seasonal and interannual differences were recorded for several of them. The community composition reinforced the evidence for a higher resemblance of the Cyprus mesozooplankton to the offshore communities of the northern and central Levantine Sea and those around Rhodes Island, instead of the northeastern Mediterranean coastal areas. Comparisons of the seasonal abundance variation of the mesozooplankton taxa with other coastal areas of the Levantine Sea are provided. Considering the seasonality of the mesozooplankton, there was a separation of the taxa into distinct groups representing the summer, the winter-spring, and the autumn periods. The temperature was the most important variable that shaped the formation of the distinct seasonal groups of taxa, while chlorophyll-α, dissolved oxygen, and salinity contributed to a lesser extent. Chlorophyll-α concentrations verified the oligotrophic character of the area and seem to be unaffected by inland inputs. The mesozooplankton community showed a spatial consistency, probably as the result of the open sea influence, and seems to be regulated mainly by the properties of the central Levantine pelagic waters and less by terrestrial inputs of inland waters.

DNA barcodes reveal striking arthropod diversity and unveil seasonal patterns of variation in the southern Atlantic Forest

The Atlantic Forest harbors 7% of global biodiversity and possesses high levels of endemism, but many of its component taxa remain unstudied. Due to the importance of tropical forests and the urgency to protect them, there is a compelling need to address this knowledge gap. To provide more information on its arthropod fauna, a Malaise trap was deployed for 12 months in a semi-degraded area of the southern Upper Paraná ecoregion of the Atlantic Forest. All specimens were DNA barcoded and the Barcode Index Number (BIN) system was employed to assign each specimen to a species proxy. DNA barcodes were obtained from 75,500 arthropods that included representatives of 8,651 BINs. Nearly 81% of these BINs were first records, highlighting the high rates of endemism and lack of study of arthropods from the Atlantic Forest. Diptera was the most abundant order, followed by Hemiptera, Lepidoptera and Hymenoptera. Diptera was also the most species-rich order, followed by Hymenoptera, Lepidoptera, and Coleoptera, a result consistent with studies in other biogeographic regions. Insects were most abundant in winter and most diverse in autumn and winter. This pattern, however, was caused mainly by the dynamics of dipteran diversity as other orders differed in their seasonal variation. The BIN composition of the insect community varied sharply through the year and also differed between the two consecutive summers included in the sampling period. The study of the 38 commonest BINs showed that seasonal patterns of abundance were not order-specific. Temperature had the strongest impact on seasonal abundance variation. Our results highlight the striking and understudied arthropod diversity of the highly fragmented Atlantic Forest, the predominance of dipterans, and the fact that abundance and richness in this insect community peak in the coolest months. Standardized studies like this generate fast and reliable biodiversity inventories and unveil ecological patterns, thus providing valuable information for conservation programs.

Equivocal associations between small-scale shoreline restoration and subtidal fishes in an urban estuary.

Restoration of degraded coastal and estuarine habitats owing to human activities is a major global concern. In Puget Sound, Washington, U.S.A., removal of hard armor from beaches and intertidal zones has become a priority for state and local agencies. However, the effectiveness of these shoreline restoration programs for subtidal habitats and fish is unknown. We surveyed six restoration sites in Puget Sound over 2 years to evaluate associations between shoreline restoration and subtidal fish abundance. We measured the abundance of juvenile salmonids and forage fishes along armored, restored, and reference shorelines. Bayesian generalized linear models showed limited support for associations between shoreline restoration and these fishes in the 3-7 years since armor removal. Pacific herring were more abundant at reference shorelines; the shoreline effect for surf smelt varied by survey site. Shoreline restoration was not an important predictor of salmonid abundance; the best models for Chinook and chum salmon included predictors for survey site and eelgrass, respectively. The retention of survey site in several species' top models reveals the influence of the broader landscape context. We also found seasonal variation in abundance for chum salmon and surf smelt. Our results suggest that juvenile forage fish and salmonids in estuaries likely have unique responses to shoreline features, and that the positive effects of armor removal either do not extend into subtidal areas or are not detectable at local scales. To be most effective, coastal restoration programs should consider broader landscape patterns as well as species-specific habitat needs when prioritizing investments.

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.

Seasonal variation in abundance and diversity of zooplankton in Asu River, Ebonyi state, Nigeria

The Physicochemical variables and Zooplankton of Asu River, Ebonyi State, Nigeria were studied monthly between October 2013 and June 2014 which covered the wet and dry seasons. The study was carried out monthly in two selected sites by collecting water samples for physiochemical analysis and zooplankton identification. Shannon-Weiner diversity and Margalef's indices were used to determine the zooplankton composition. Investigation on the physiochemical variables showed that water temperature, dissolved oxygen, total dissolved solids, pH, conductivity and carbon (iv) oxide all recorded maximum values in the dry season. The present result also showed that the river is not seriously polluted. However, only carbon (iv) oxide and nitrate varied significantly between seasons (p < 0.05). Forty two (42) zooplankton species comprising Rotifera (7 families; 23 species), Copepoda (2 families; 8 species) and Cladoceran (6 families; 11 species) were identified. Rotifera spp. were numerically dominant and the most diverse group but the crustacean, Thermocyclops oithonoides dominated the total zooplankton biomass during the study. Species abundance showed inverse relationship with species richness, Shannon-Weiner diversity and Evenness. Zooplankton abundance was at its peak in the dry season while species richness, Shannon- Weiner diversity and evenness increased from dry season to wet season.

Seasonal Variation in Abundance, Distribution and Environmental Impacts of Geomicrobiological Communities in the Lower Calabar River Channel, Calabar, Nigeria

Microbes act as geochemical agents for the degradation of environmental contaminants hence their abundance and distribution influences ecological response to pollution stress in soils, sediments, and rivers systems and in environmental protection. In this paper seasonal variation in geomicrologicl abundance in the river water, sediments and adjoining soils have been assessed. The results indicate a higher microorganism count during the wet season. The presence of E. coli in 100ml of water implies that water is unsuitable for any domestic use without disinfection. The Faecal and Total Coliform counts also indicate that undesirable sources are contaminating the river and posing environmental health risk. However environmental self-remediation and possible absence of sources of the microorganisms was promoted during the wet season than the dry season.

Environmental effects on Calanus finmarchicus abundance and depth distribution in the Barents Sea

Abstract The vertical migrations performed by zooplankton at daily and seasonal scales are important for marine ecosystem dynamics and biogeochemical cycles. We analysed associations between seasonal variation in abundance and depth distribution of the copepod Calanus finmarchicus and temperature and predation pressure from visual (capelin and herring) and non-visual (ctenophores) predators, using data from a &amp;gt; 30-year survey in the southwestern Barents Sea. Calanus finmarchicus abundances were significantly reduced in upper waters with increased capelin biomass, possibly due to a combination of predation mortality and active avoidance of the upper layer. The weighted mean depth of Calanus finmarchicus tended to become shallower, and abundances in deeper layers lower, with a high probability of ctenophore occurrence, possibly due to a predation effect at depth. Temperature influenced the seasonal timing of Calanus finmarchicus, but appeared less important for depth distribution. This study illustrates how climate-driven changes in the physical and biological environment can influence the seasonal and vertical distribution of zooplankton, which has major implications for the flow of energy and nutrients in marine ecosystems.

Partitioning resources through the seasons: abundance and phenology of carrion beetles (Silphidae) in southeastern Ontario, Canada

The coexistence of ecologically similar species is thought to require resource partitioning to minimize competition. Phenological, seasonal differences in activity may provide an important axis for resource partitioning. Here, we test for evidence of seasonal differences in activity within a diverse guild of carrion beetles (Silphidae) in a habitat preserve on the Frontenac Arch, southeastern Ontario, Canada, using a large-scale survey during their active seasons (April to October). We then used generalized additive models to test for differences in seasonal abundance among eight co-occurring carrion beetle species, including five species of burying beetles (Nicrophorinae: Nicrophorus Fabricius, 1775) and three species from the Silphinae subfamily. Consistent with previous work, all species showed seasonal variation in abundance, with peak abundance of most species occurring between June and August. All but one species (Nicrophorus sayi Laporte, 1840) showed positive relationships between abundance and temperature. We find evidence consistent with seasonal partitioning of resources among Nicrophorus habitat generalists that could potentially reduce competition for limited carrion resources. In contrast, we find little evidence for seasonal differences in abundance among Nicrophorus habitat specialists, which instead may partition resources spatially. Overall, our results provide evidence consistent with an important role for seasonal resource partitioning among carrion beetle species that show higher levels of spatial (habitat) overlap within a temperate beetle guild.

Comprehensive analysis of laboratory boron contamination for boron isotope analyses of small carbonate samples

Boron isotopes are widely used as a proxy of marine carbonate in paleoclimatology to reconstruct seawater pH and atmospheric pCO2, and precise and accurate boron isotopic analysis is required for this purpose. Determination of boron isotopic composition is susceptible to contamination, especially for sample analyses with small amounts of boron; however, sources of experimental and laboratory contamination are not clearly evaluated. In this study, boron and boron isotope contamination during the analysis of small carbonate samples were examined in detail during sample cleaning, sample storage, chemical separation, and isotope measurement. Repeated cleaning of foraminifera shells using H2O with ultrasonication effectively minimized boron contamination from clay-rich material; however, an additional cleaning step with methanol and H2O2 is recommended to obtain repeatable precise δ11B, δ18O, and Mg/Ca values. Boron contamination during sample storage in a glass vial was far greater than expected. Glass-derived boron attached to foraminifera shells could not be completely removed by any physical or chemical cleaning process and influenced the δ11B value significantly. Even when a low-boron HEPA, boron-free HEPA, or ULPA filter was used for air-handling in the laboratory, airborne contamination by gaseous boron can still be significant, with seasonal variation in abundance and isotopic composition. Although this affects the procedural blank of boron during chemical separation, an acid-removing chemical filter can reduce the airborne boron flux. An autosampler in the MC-ICPMS analysis might be an additional source of airborne boron contamination.