Reached Peak Abundance Research Articles

Estimation of bacterio‐, picophyto‐ and nanophytoplankton abundance in the Middle Caspian Sea by flow cytometry

Aim. For the first time, flow cytometry has been used to study the structure and functional characteristics of bacterio‐, pico‐ and nano‐ phytoplankton in the Middle Caspian during the bloom period in early September 2022.Water samples were taken at different horizons (from the surface to the bottom layer) at a series of stations along the western coast of the Caspian Sea on the border between its northern and central parts to quantitatively assess heterotrophic bacterioplankton, picophyto‐ and nanophy‐ toplankton. Sampling was undertaken in early September 2022 under summer hydrological conditions with water surface temperatures ranging from 24.7°C to 26.7°C. Sample analysis was performed using flow cytometry.Extremely high concentrations of picophytoplankton (up to 1.8×105 cells/mL), probably of Synechococcus picocyanobacteria, were detected off the northwestern coast of the Middle Caspian. Very high values of nanophytoplankton abundance (up to 1.6×105 cells/mL), dominated by small flagellates, were also found. A clear spatial uncoupling of pico‐ and nanophytoplankton was revealed. Maximum levels of nanophytoplankton were confined to the area of intensive phytoplankton blooming with high concentrations of chlorophyll a, while picophytoplankton reached peak abundance further south, outside this area. The influence of the thermocline on the vertical structure of microbial communities was detected. The concentrations of picophytoplankton and the proportion of physiologically active HNA‐bacteria decreased sharply under the thermocline.The results obtained indicate the leading role of the smallest phototrophs in the Caspian pelagial and emphasise the need for further comprehensive studies of Caspian microbial communities using modern methods.

Apparent niche differences between native and exotic lady beetles

Generalist predators can enhance biological control by filling unique niches and complementing other natural enemies, or disrupt it by preying upon other predators and parasitoids, complicating their net value for biological control. We searched for evidence of complementarity and/or interference between native (primarily Eriopis chilensis and E. eschscholtzi) and exotic (primarily Hippodamia variegata and Harmonia axyridis) lady beetles attacking aphids in alfalfa (Medicago sativa) fields near Santiago, Chile. Across 60 fields and three growing seasons, exotic lady beetle adults and larvae reached peak abundance relatively earlier in the growing season than the natives. Furthermore, exotic lady beetle peaks aligned more closely with aphid peak abundance than did native lady beetle peaks. Abundances of native lady beetle adults and larvae were weakly positively correlated with those of exotics, and peak aphid densities were generally lowest in fields where native and non-native lady beetle adults were similarly abundant. Therefore, we did not see evidence of strong interference between exotics and natives. Natural-agricultural habitat edges reduced native, but not exotic, larval lady beetle lag behind aphid peaks and was associated with greater lady beetle and lower aphid densities. Moreover, farms embedded in landscapes with greater natural habitat cover supported more exotic, but not native, lady beetles, and increased the lag between larval lady beetles and aphids for natives but not exotics. These findings support the idea that farms embedded within mosaics of natural and agricultural habitats may provide greater interaction potential between native lady beetles and aphid pests on farms as they move across the landscape, leading to greater top-down control. In contrast, exotic lady beetle lags were unaffected by landscape composition or configuration, but their greater densities in farms surrounded by more natural habitats might reflect a 'concentration effect' whereby exotic lady beetle abundance becomes concentrated in the agricultural habitats that they prefer. Our findings suggest that some lady beetles introduced for biocontrol may be better adapted to intensively managed habitats than natives, possibly leading to spatiotemporal complementarity between native and exotic lady beetles.

Habitat and trophic niche overlap among juvenile black sea bass, tautog, and cunner: interspecific interactions amid a species geographic range expansion

Juvenile black sea bass Centropristis striata populations are increasing in southern New England estuaries of the northeastern USA with possible trophodynamic effects on labrid species: tautog Tautoga onitis and cunner Tautogolabrus adspersus. In this study, we examined the abundance, size-structure, and feeding ecology of juvenile sea bass and labrids in Narragansett Bay (Rhode Island, USA) from June to October in 2018 and 2019 and evaluated potential interspecific competition using habitat, diet, and isotopic niche overlap indices. Juveniles (age-0+) of each fish species spatiotemporally co-occurred in shallow, polyhaline habitats throughout the estuary. Age-0 cohorts were numerically dominant across species and initially recruited to the study area in July (minimum total length, TL = 15-20 mm), reached peak abundances in mid- to late summer (maximum abundances = 12-140 fish 100 m-2), and emigrated from field sites in October (maximum TL = 85-96 mm). Stomach content and stable isotope (δ15N and δ13C) analyses determined that focal fishes were generalist carnivores that foraged in bentho-pelagic food webs. Fishes also overlapped in their respective ambit and core isotopic niche space, but interspecific dietary overlap was size-dependent. Dietary overlap was most pronounced between sea bass ≤49 mm TL and labrids ≤59 mm TL due to their mutual reliance on gammarid and caprellid amphipods. Ontogenetic dietary shifts then resulted in food niche segregation, such that sea bass 50-139 mm TL consumed decapod crustaceans and fish, whereas labrids 60-181 mm TL mainly fed on amphipods, worms, bivalves, and turf-associated biota, i.e. bryozoans, hydroids, and seaweeds. Habitat and trophic niche overlap between early juvenile sea bass and labrids purportedly have not caused opposite population trajectories or food resource limitation in Narragansett Bay, indicating an absence of exploitative competition. Alternatively, realized competition between species may be too spatiotemporally restricted to alter their population dynamics. Continuous monitoring of the sea bass’s bio-ecological effects in southern New England estuaries is warranted, however, given their recent range expansion and increasing abundances at northern latitudes.

Environmental and Circadian Regulation Combine to Shape the Rhythmic Selenoproteome.

The circadian clock orchestrates an organism’s endogenous processes with environmental 24 h cycles. Redox homeostasis and the circadian clock regulate one another to negate the potential effects of our planet’s light/dark cycle on the generation of reactive oxygen species (ROS) and attain homeostasis. Selenoproteins are an important class of redox-related enzymes that have a selenocysteine residue in the active site. This study reports functional understanding of how environmental and endogenous circadian rhythms integrate to shape the selenoproteome in a model eukaryotic cell. We mined quantitative proteomic data for the 24 selenoproteins of the picoeukaryote Ostreococcus tauri across time series, under environmentally rhythmic entrained conditions of light/dark (LD) cycles, compared to constant circadian conditions of constant light (LL). We found an overrepresentation of selenoproteins among rhythmic proteins under LL, but an underrepresentation under LD conditions. Rhythmic selenoproteins under LL that reach peak abundance later in the day showed a greater relative amplitude of oscillations than those that peak early in the day. Under LD, amplitude did not correlate with peak phase; however, we identified high-amplitude selenium uptake rhythms under LD but not LL conditions. Selenium deprivation induced strong qualitative defects in clock gene expression under LD but not LL conditions. Overall, the clear conclusion is that the circadian and environmental cycles exert differential effects on the selenoproteome, and that the combination of the two enables homeostasis. Selenoproteins may therefore play an important role in the cellular response to reactive oxygen species that form as a consequence of the transitions between light and dark.

Where do the fish come from, and where do they go? Seasonal observations of pelagic fishes from echosounder moorings in the Chukchi sea

Recent summer surveys of the Chukchi Sea determined that pelagic fishes were dominated by large numbers of age-0 Arctic cod and walleye pollock, while adult fishes are comparatively scarce. Modeling based on regional currents indicates that these age-0 fishes are likely advected to the north in fall; however, the source and fate of these fishes remains unclear as this region is seasonally ice-covered. To determine the movement and variability of this age-0 gadid population, bottom-moored multifrequency echosounders were deployed at three locations in the northeastern Chukchi Sea from 2017-2019. These observations indicate that the abundance and composition of the pelagic community on the Chukchi Sea shelf is highly variable over seasonal time scales. Fish abundance was very low in winter, increased in May, and reached peak abundance in late summer. Target strength and diel vertical migration of fishes increased in summer, indicating that this is a key period for growth. Age-0 gadids were displaced to the northeast, consistent with the dominant advection on the shelf. Fish speeds and headings were strongly correlated with local currents, providing evidence that these small age-0 fishes are primarily being passively transported and behavior plays a limited role in population distribution.

Predictability of Invasive Argentine Ant Distribution Across Mediterranean Ecoregions of Southern California

The invasiveness of nonnative taxa can vary across a landscape due to environmental gradients, suggesting that location-dependent management strategies may be more effective at reducing spread compared to a “one size fits all” approach across the entire introduced range. Using bait stations placed along linear transects within habitat preserves, we tested for effects of ecoregion, vegetation, soil moisture, habitat edge type (i.e., moisture source), and distance from edges on the presence of the invasive Argentine ant Linepithema humile in San Diego County, California, a region with high indigenous biodiversity and numerous rare and protected species. Our results showed an inverse relationship between the presence of native ant species and the presence of the Argentine ant across ecoregions, with the latter reaching peak abundance in the coastal terrace. Argentine ant presence was negatively associated with distance from all edge types regardless of location, but the magnitude of this effect varied among ecoregions. In the xeric foothill and inland valleys, the probability of occurrence was nearly 0 at distances of 200 m and 750 m from moisture edges, respectively, whereas in the coastal terrace, the probability remained above 0.80 at distances up to 1.25 km. When compared to previous studies at different spatial scales, these findings provide an alternative perspective on the invasiveness of the Argentine ant at the landscape level. Our results further suggest that efforts to control spread in regions with a Mediterranean climate may be more successful in inland areas, where the ant is likely to have lower environmental tolerance and native ant species may be better able to generate biotic resistance. In contrast, different tactics and expectations may be necessary for coastal areas, where the same constraints are diminished or absent.

Initial Population Growth of Melanaphis sacchari (Hemiptera: Aphididae) in Relation to Sorghum Hybrids and Growing Seasons in Northeastern Mexico

Aphids are important pests of many agricultural crops worldwide, and an understanding of their population dynamics is a prerequisite for implementing integrated pest management strategies to avoid crop losses. Aphid populations commonly increase exponentially, and scouting during the initial phase is vital to avoid density levels surpassing economic thresholds. The sugarcane aphid, Melanaphis sacchari (Zehntner), has become the most important insect pest of sorghum, Sorghum bicolor (L.) Moench, in Mexico after its invasion in 2013 (Rodríguez-del-Bosque and Terán 2015, Southwest. Entomol. 40: 433–434). Initial population growth of M. sacchari is generally free of natural enemies, as they arrive when aphids reach peak abundance later in the season (Rodríguez-del-Bosque et al. 2018, Southwest. Entomol. 43: 277–280). The objective of this investigation was to determine the impact of two grain sorghum hybrids (susceptible and resistant) and growing seasons (spring and fall) on the initial population growth of M. sacchari in northeastern Mexico.This study was conducted in two contiguous 0.25-ha plots of ‘DK-54′ (susceptible) and ‘Mezquite’ (resistant) sorghum hybrids at Campo Experimental Río Bravo of the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, near Río Bravo, northern Tamaulipas, Mexico (N25°57′, W98°01′), during the spring and fall growing seasons of 2014–2017. Plantings were during February and July during the spring and fall seasons, respectively. When M. sacchari was first detected, normally at the boot growth stage, a middle leaf of 20 randomly selected plants was excised to count all aphids (adults+nymphs) on both hybrids. Sampling continued every 3–5 d for the next 20 d, when plants reached the flowering stage. Linear regression analyses were conducted to test the relationship between aphid density (y) and days after first detected (x), and regression slope coefficients (b) were compared by t test (P < 0.05) by hybrids, growing seasons, and years (SAS Institute 2012, SAS release 9.3 ed., Cary, NC).Aphid density data were pooled by hybrids (DK-54 and Mezquite) and growing seasons (spring and fall) because no significant differences (P < 0.05) in slopes (b) were found among years. Significant differences (P < 0.05) in slopes were found between hybrids and growing seasons. During spring, M. sacchari population growth averaged 9.3 and 0.16 aphids/leaf/d in DK-54 and Mezquite, respectively (Fig. 1), demonstrating that aphids reached the economic threshold of 50 aphids/leaf (Bowling et al. 2016, J. Integr. Pest Manag. 7: 1–13) on DK-54 during the first 5 d after first detection. In contrast, the economic threshold in Mezquite was never reached during the first 20 d. Population growth of M. sacchari increased during the fall growing season, with an average of 65.5 aphids/leaf/d on DK-54 and 7.7 aphids/leaf/d on Mezquite (Fig. 2). Based on these data, the economic threshold on DK-54 was reached the day after first detection, while the economic threshold on Mezquite was reached 6 d after first detection.Daily M. sacchari population growth on DK-54 was 58 and 9 times greater than on Mezquite during the spring and fall, respectively. The time to doubling of population density on DK-54 was 5 d and 8–17 d on Mezquite, which is similar to a study comparing M. sacchari population growth on susceptible and resistant sorghum hybrids in Texas and Louisiana (Brewer et al. 2017, J. Econ. Entomol. 110: 2109–2118). Under optimal laboratory conditions, M. sacchari doubling time was 1.7 d (Souza and Davis 2020, Fla. Entomol. 103: 116–123). In summary, sorghum hybrids and growing season affected initial population growth of M. sacchari in northeastern Mexico, demonstrating both factors should be considered when scouting to avoid surpassing the economic threshold.

Fire and Mechanical Forest Management Treatments Support Different Portions of the Bird Community in Fire-Suppressed Forests

Silvicultural treatments, fire, and insect outbreaks are the primary disturbance events currently affecting forests in the Sierra Nevada Mountains of California, a region where plants and wildlife are highly adapted to a frequent-fire disturbance regime that has been suppressed for decades. Although the effects of both fire and silviculture on wildlife have been studied by many, there are few studies that directly compare their long-term effects on wildlife communities. We conducted avian point counts from 2010 to 2019 at 1987 in situ field survey locations across eight national forests and collected fire and silvicultural treatment data from 1987 to 2016, resulting in a 20-year post-disturbance chronosequence. We evaluated two categories of fire severity in comparison to silvicultural management (largely pre-commercial and commercial thinning treatments) as well as undisturbed locations to model their influences on abundances of 71 breeding bird species. More species (48% of the community) reached peak abundance at moderate-high-severity-fire locations than at low-severity fire (8%), silvicultural management (16%), or undisturbed (13%) locations. Total community abundance was highest in undisturbed dense forests as well as in the first few years after silvicultural management and lowest in the first few years after moderate-high-severity fire, then abundance in all types of disturbed habitats was similar by 10 years after disturbance. Even though the total community abundance was relatively low in moderate-high-severity-fire habitats, species diversity was the highest. Moderate-high-severity fire supported a unique portion of the avian community, while low-severity fire and silvicultural management were relatively similar. We conclude that a significant portion of the bird community in the Sierra Nevada region is dependent on moderate-high-severity fire and thus recommend that a prescribed and managed wildfire program that incorporates a variety of fire effects will best maintain biodiversity in this region.

Patterns of abundance across geographical ranges as a predictor for responses to climate change: Evidence from UK rocky shores

AbstractAimUnderstanding patterns in the abundance of species across thermal ranges can give useful insights into the potential impacts of climate change. The abundant‐centre hypothesis suggests that species will reach peak abundance at the centre of their thermal range where conditions are optimal, but evidence in support of this hypothesis is mixed and limited in geographical and taxonomic scope. We tested the applicability of the abundant‐centre hypothesis across a range of intertidal organisms using a large, citizen science‐generated data set.LocationUK.MethodsSpecies' abundance records were matched with their location within their thermal range. Patterns in abundance distribution for individual species, and across aggregated species abundances, were analysed using Kruskal–Wallis tests and quantile general additive models.ResultsIndividually, invertebrate species showed increasing abundances in the cooler half of the thermal range and decreasing abundances in the warmer half of the thermal range. The overall shape for aggregated invertebrate species abundances reflected a broad peak, with a cool‐skewed maximum abundance. Algal species showed little evidence for an abundant‐centre distribution individually, but overall the aggregated species abundances suggested a hump‐backed abundance distribution.Main ConclusionsOur study follows others in showing mixed support for the abundant‐centre hypothesis at an individual species level, but demonstrates an increased predictability in species responses when an aggregated overall response is considered.

Radiation-Induced Immunity in Kidney Cancer Patients: Seq-ing Commonality Between Peripheral and Intratumoral T cell Repertoires

Abstract Radiation has long been part of the standard of care for cancer treatment. Clinical studies combining immunotherapy with radiation have shown promising response rates implicating radiotherapy as an inducer of tumor immunity. Due to the scarcity of human samples treated in situ with radiation, exploration of this phenomenon has been largely limited to murine models. While these data draw connections between intratumoral immune responses and wider effects in peripheral blood, advances in patient care are restricted by inherent differences between murine models and human disease. Therefore, to identify commonality between local intratumoral and systemic responses to radiation, we analyzed clinical trial samples from renal cell carcinoma (RCC) patients treated with stereotactic body radiation therapy (SBRT) at the primary tumor. With access to patient tumors and peripheral blood, we hypothesized that SBRT initiates local and systemic anti-tumor immunity. Pathway analysis from tumor RNAseq data showed SBRT-specific immune processes: TCR activation, increased costimulation, and chemokine signaling. Deeper examination through single cell RNA sequencing identified the sources of these signals. In parallel, analysis by T cell receptor sequencing (TCRseq) showed increased tumor T cell clonality with SBRT treatment. TCRseq of serial blood samples revealed tumor-enriched T cell clonotypes reaching peak abundance 2 weeks post-SBRT. This expansion was not sustained and contracted towards baseline levels 4 weeks after SBRT. Collectively, these results indicate a critical interval following radiation, wherein tumor-enriched T cell clones are expanded in circulation, that could be utilized to bolster responses to immunotherapy.

7700-year persistence of an isolated, free-living coral assemblage in the Galápagos Islands: a model for coral refugia?

In an eastern-Pacific coral assemblage at Devil’s Crown, Galapagos Islands, Ecuador, two coral species, Psammocora stellata and Cycloseris (Diaseris) distorta, form dense populations of unattached colonies on sand and rubble substrata. In the Galapagos, living C. (D.) distorta is found only at this single site, whereas populations of P. stellata are found throughout the Archipelago. Six cores dating to ~ 7700 yBP showed P. stellata to be dominant throughout the history of this isolated community, but C. (D.) distorta increased in abundance from ~ 2200 yBP and reached peak abundance between 1471 yBP and the present. The relative frequency of the two coral species may be linked to millennial-scale climatic variability, and this site may represent a refuge for C. (D.) distorta from unfavorable climatic fluctuations on millennial timescales. Our results demonstrate that some corals can persist in isolated populations for millennia.

Assessment of combined tools and strategies for Aedes aegypti control with low environmental impact.

The control of the mosquito vector Aedes aegypti L. (Diptera: Culicidae) is the main action against dengue, chikungunya, and Zika. The excessive use of conventional insecticides has promoted the development of other control methods and strategies with lower environmental impact. We evaluated the effectiveness of applying triflumuron 1ppm and emptying water-filled containers in a field trial in temperate Argentina. Both control methods were implemented either individually or combined and regularly from the beginning of the mosquito reproductive season or once it reached peak abundance. The impact on a non-target midge of the genus Chironomus was also tested. The highest reductions of Ae. aegypti were achieved in treatments which included triflumuron. This effect was stronger when applied from the beginning of the reproductive season, with < 1.3% of positive containers throughout the entire season. No enhancing effects were obtained when combining both control methods. Treatments with triflumuron were not completely innocuous for the non-target species, with Chironomus sp. more susceptible to treatments including triflumuron applied from the beginning of the reproductive season than all others. Sharp reductions of mosquito populations in urban environments with high density of water-filled containers are possible with minimum container management efforts, by applying triflumuron 1ppm every 6weeks. In temperate urban settings, better results can be obtained when applications begin early in the reproductive season of the mosquito vector Aedes aegypti.

Dormant-Season Fire Inhibits Sixweeks Fescue and Enhances Forage Production in Shortgrass Steppe

Semiarid rangelands experience substantial interannual variability in precipitation, which can determine the relative abundance of species in any given year and influence the way that fire affects plant community composition and productivity. Long-term studies are needed to examine potential interactions between fluctuating community composition and the role of fire in these ecosystems. Here, we report on an 11-year (2006 to 2016) study of annual and triennial dormant-season prescribed fires in the semiarid shortgrass steppe of Colorado, USA. Productivity of the dominant C4 shortgrasses was not reduced by dormant-season burns in any year. The C3 annual grass, six-weeks fescue (Vulpia octoflora [Walter] Rydb.) was rare during the first 7 years (2006 to 2012) but, following drought in 2012, increased dramatically in unburned plots (2013 to 2016). Both spring and autumn annual burns reduced fescue biomass during 2014 to 2016 by an average of 87%. Autumn triennial burns prior to the 2013 and 2016 growing seasons similarly reduced fescue (86%), while spring triennial burns implemented prior to the 2012 and 2015 growing seasons did not. Results indicate that burning during fescue establishment can prevent proliferation, but burning two years later when fescue had reached peak abundance was ineffective. All three burn treatments that suppressed fescue subsequently enhanced C4 grass production. We suggest that rangeland managers be aware of the potential for sixweeks fescue germination and establishment during warm, wet winters that follow drought years, and consider the use of dormant-season prescribed fire to adaptively reduce negative impacts on forage production.

Creation of forest edges has a global impact on forest vertebrates.

SummaryForest edges influence more than half the world’s forests and contribute to worldwide declines in biodiversity and ecosystem functions. However, predicting these declines is challenging in heterogeneous fragmented landscapes. We assembled an unmatched global dataset on species responses to fragmentation and developed a new statistical approach for quantifying edge impacts in heterogeneous landscapes to quantify edge-determined changes in abundance of 1673 vertebrate species. We show that 85% of species’ abundances are affected, either positively or negatively, by forest edges. Forest core species, which were more likely to be listed as threatened by the IUCN, only reached peak abundances at sites farther than 200-400 m from sharp high-contrast forest edges. Smaller-bodied amphibians, larger reptiles and medium-sized non-volant mammals experienced a larger reduction in suitable habitat than other forest core species. Our results highlight the pervasive ability of forest edges to restructure ecological communities on a global scale.

Population dynamics of the non-indigenous hydrozoan Clytia hummelincki (Hydrozoa: Campanulariidae) in two contrasting Mediterranean habitats

ABSTRACTThe non-indigenous hydrozoan Clytia hummelincki, recorded for the first time in the Mediterranean Sea in 1996, has now become established on barren grounds where conditions of low diversity, high grazing pressure and low levels of competition occur. The mechanisms of persistence of this species, as well as its population dynamics in this habitat and in species-rich, algae-dominated shallow rocky communities were investigated in situ at four sampling sites in the Northern Ionian Sea from October 2012 to September 2014. Multivariate analyses were conducted to assess the differences in population dynamics of this species in both contrasting habitats. Clytia hummelincki reached peak abundance during summer, with numerous reproductive structures observed in August and September. A remarkable regression period was evident in the cold season, when colonies were largely reduced to dormant tissue in the coenosarc of the hydrorhiza and were often covered by encrusting algae. Both regeneration of colonies from resting hydrorhizae and recruitment of new planulae are involved in the maintenance of the populations. Colonies regrew from hydrorhizae less than half of the time. Population dynamics in sea-urchin barren grounds and algae-dominated communities did not differ significantly, suggesting that populations of this hydrozoan are now well established in the central Mediterranean Sea. This species is no longer confined to low diversity, highly grazed, low competition environments.

Drivers of population dynamics in sable antelope: forage, habitat or competition?

Similar to declines in antelope species across African conservation areas, sable (Hippotragus niger) at Kgaswane Mountain Reserve, South Africa, has exhibited a negative trend in abundance since 2000. To investigate the cause of decline, we assessed three hypotheses: seasonal forage abundance, habitat conditions and interspecific competition. We considered the evidence for each hypothesis by analysing reserve survey data, rainfall records and historical burn data with hierarchical models that incorporated potential density-dependent effects and environmental covariates. After accounting for the effects of sable abundance, we found that sable population growth was most strongly related to the interspecific competition covariates and to waterbuck (Kobus ellipsiprymnus) count in particular. Also, the strength of the relationship was shaped by the trend in sable numbers and whether the population was before or after peak abundance: the strongest indication of interspecific competition occurred after sable had reached peak abundance. The interaction between abundance of sable and that of potentially competing species emphasizes the importance of accounting for density-dependent processes, and in particular longer-term phases in abundance, when judging the roles of other factors that affect species abundance.

Frogs in the spotlight: a 16-year survey of native frogs and invasive toads on a floodplain in tropical Australia.

Although widespread declines in anuran populations have attracted considerable concern, the stochastic demographics of these animals make it difficult to detect consistent trends against a background of spatial and temporal variation. To identify long‐term trends, we need datasets gathered over long time periods, especially from tropical areas where anuran biodiversity is highest. We conducted road surveys of four anurans in the Australian wet–dry tropics on 4637 nights over a 16‐year period. Our surveys spanned the arrival of invasive cane toads (Rhinella marina), allowing us to assess the invader's impact on native anuran populations. Our counts demonstrate abrupt and asynchronous shifts in abundance and species composition from one year to the next, not clearly linked to rainfall patterns. Typically, periods of decline in numbers of a species were limited to 1–2 years and were followed by 1‐ to 2‐year periods of increase. No taxa showed consistent declines over time, although trajectories for some species showed significant perturbations coincident with the arrival of toads. None of the four focal frog species was less common at the end of the study than at the beginning, and three of the species reached peak abundances after toad arrival. Survey counts of cane toads increased rapidly during the initial stage of invasion but have subsequently declined and fluctuated. Distinguishing consistent declines versus stochastic fluctuations in anuran populations requires extensive time‐series analysis, coupled with an understanding of the shifts expected under local climatic conditions. This is especially pertinent when assessing impacts of specific perturbations such as invasive species.

Variability of Winter-Spring Bloom Phaeocystis pouchetii Abundance in Massachusetts Bay

Abundance of the prymnesiophyte Phaeocystis pouchetii was quantified via light microscopy at 2-week to monthly intervals in Massachusetts Bay (southern Gulf of Maine, NW Atlantic) during 1992–2012. Variability in the abundance and seasonal cycle of Phaeocystis are described and synoptic hydrographic, nutrient, and meteorological data were analyzed to identify factors that may influence Phaeocystis abundance. The maximum Phaeocystis abundance was 14 × 106 cells L−1 (10 Apr 2008). It was frequently (5 of 8 years) absent prior to year 2000, but not thereafter. Seasonally, it first appeared in February to early March, reached peak abundance in mid-April, and persisted until May or early June for a duration of 0–112 days (mean 34 days). A long-term alternation between Phaeocystis and centric diatom abundance was apparent, suggesting winter-spring selection of either Phaeocystis or centric diatoms. Phytoplankton community analysis suggested that blooms affected the rest of the phytoplankton community. Phaeocystis blooms were manifest as a substantial increase in particulate nutrients above normal levels. Phaeocystis blooms were preceded in February by a slightly elevated concentration of NO3 (9.3 vs. 6.5 μM when absent) and PO4 (0.99 vs. 0.79 μM when absent). Blooms were also preceded by elevated ratios of NO3/PO4, NO3/Si, and PO4/Si, and warmer, saltier waters reflecting reduced river discharge. The correlation with salinity and river discharge suggests that Phaeocystis bloom variability is partially determined by annually varying circulation processes that determine the degree of low nutrient, low salinity coastal water intrusion into Massachusetts Bay.

Sedimentary environments in the south-western Barents Sea during the last deglaciation and the Holocene: a case study outside the Ingøydjupet trough

A lithological and foraminiferal study of newly acquired sediment cores outside the Ingoydjupet (Ingoy Deep) trough has been carried out to improve constraints on the last deglacial history in the south-western Barents Sea. Three lithofacies and three foraminiferal facies were identified. The lowermost lithological unit is a diamicton interpreted as glacial till. It contains a low-abundance, ecologically mixed foraminiferal assemblage, presumably resulting from glacial reworking. Above the diamicton, a layer of ice-rafted debris (IRD), likely associated with intensive iceberg production, marks the initial destabilization of the marine-based ice sheet. At this time, ca. 15.6–15.0 Ky B.P., opportunistic foraminiferal species Nonionellina labradorica and Stainforthia spp. reached peak abundance. During the south-western Barents Sea ice-margin retreat, presumably corresponding to the Bolling interstadial, a sequence of glaciomarine laminations was deposited conformably on the layer of IRD. Sedimentation rates were apparently high (estimated about 0.4 cm per year) and the foraminiferal fauna was dominated by Elphidium spp. and Cassidulina reniforme , species common for glacier-proximal environments. A hiatus at the top of the deglacial unit is likely linked to the high bottom-current activity associated with a strengthened inflow of Atlantic water masses into the Barents Sea. The uppermost lithological unit is represented by the Holocene marine sandy mud. It contains a high-abundance, high-diversity foraminiferal fauna with common cassidulinids, Cibicides spp., Epistominella pusilla and planktic species. Keywords: Deglaciation; Barents Sea ice sheet; sediment cores; lithofacies; biozonation. (Published: 5 May 2016) To access the supplementary material for this article, please see the supplementary file in the column to the right (under Article Tools). Citation: Polar Research 2016, 35 , 23104, http://dx.doi.org/10.3402/polar.v35.23104

Multi-parameter flow cytometric analysis of uterine immune cell fluctuations over the murine estrous cycle

Investigating immune cell populations within various reproductive tissues commonly utilises flow cytometric methods. With advances in fluorophore technology and equipment capabilities, multiple cell types from a single tissue sample can be identified by using different combinations of cell surface markers to distinguish specific cell populations. Here a protocol optimized for mouse uterine tissue was used to show the proportional changes in dendritic cells, monocyte/macrophages, T and B cells, NK and NK T cells, and the granulocytes, neutrophils and eosinophils at each of the four stages of the estrous cycle. Importantly, we demonstrate that use of anti-SiglecF or assessment of FSC/SSC plots could be used to differentiate monocyte/macrophage and eosinophil populations that otherwise cannot be distinguished by use of the common combination of antibodies against F4/80 and CD11b. Our results clearly indicate that within the uterus a dynamic population of immune cells resides, with many cell types reaching peak abundance at estrus and metestrus phases of the cycle, consistent with their importance in the response to paternal antigens and/or pathogens encountered after insemination.