Narrow Niche Research Articles

A habitat is not enough - increasing the chances of success for species reintroduction in riverscapes by habitat modeling and connectivity analysis

Alpine rivers are among the most heavily modified ecosystems in Europe. Following massive interventions in the 18th and 19th centuries, many plant species specialized in these challenging environments declined and are now endangered or even locally extinct. Today, attempts are being made to reintroduce these species as part of restoration measures, but only a few are successful. The selection of potential sites for reintroduction is commonly intuitive and based on practical considerations, while a prior scientific assessment of habitat availability and habitat connectivity is lacking. To increase the success of future reintroductions, we employ a habitat suitability model and subsequent habitat connectivity analysis to identify promising regions and patches for reintroduction within a riverscape. We demonstrate this approach using the Alpine river specialists Chondrilla chondrilloides and Myricaria germanica in three differently degraded and one restored section of the large Alpine river Isar. All river sections provide habitats for both species, but with increasing degradation, habitats become fewer and less connected. For the species with a narrower habitat niche and lower dispersal ability, suitable and connected patches that support a self-sustained metapopulation are only found in the near-natural sections. Despite an improvement in the habitat situation, the patch size in the restored section is too small, and the patches are too scattered to support a successful reintroduction of the species. We show that this evidence-based approach outperforms an intuitive selection of out-planting sites. The results further underline the importance of using scientific habitat analysis to increase the success of reintroduction measures.

Feeding habits of the longfin goatfish Upeneus supravittatus Uiblein and Heemstra, 2010, along Chennai coast, south India

Recognising the need to understand the feeding habits of marine fishes, a study was undertaken on the longfin goatfish Upeneus supravittatus Uiblein and Heemstra, 2010, which contributed to trawl fisheries along Chennai coast (south-east coast of India). Dataon trophic attributes such as mouth gape area, gill raker counts, stomach and intestine lengths and gut condition and contents were collected and analysed to determine condition index, index of relative importance (IRI), niche breadth and trophic level (TrL) with reference to two variables, namely, body size (small, medium and large) and season (post north-east monsoon (PNE); summer (SUM); south-west monsoon (SW); north-east monsoon (NE). The mouth gape area of U. supravittatus was 129.3 mm2. The maximum body depth-total length ratio was 1:5.0; gill rakers in lower arch was 29 and the relative intestine length was 0.48. Empty stomach contributed 56.1% of the samples. U. supravittatus fed on prey belonging to 25 Orders and >40 Genera. Decapods such as shrimps and crablets were the main prey followed by fishes. The IRI of decapods was 6474 and that of fishes was only 193. The maximum prey size predated by the fish was 33.5 and 9.8% in terms of the predator’s length and weight, respectively. Higher prey diversity was noticed in small size group and during south-west monsoon season. The narrow niche breadth of 0.20 showed the selective nature of the fish to feed on decapods. The fish is a benthic carnivore with a mean trophic level of 3.58. The trophic level decreased with body size. Diet similarity was evident between north-east and post north-east monsoon and between summer and south-west monsoon seasons. Diversity indices showed marginal variation in prey diversity among size groups and among seasons. This study paves way for estimating production efficiency of U. supravittatus. Keywords: Diet composition, Index of relative importance, Trophic level, Trophic morphology, U. supravittatus

The small and inconspicuous majority: Revealing the megadiversity and historical biogeography of the Pristimantis unistrigatus species group (Anura, Strabomantidae)

With more than 600 recognized species, the genus Pristimantis is already the most diverse among vertebrates, but described species only represent a fraction of the actual diversity in this clade. This genus is widely distributed throughout the Neotropics and represents an interesting model for biogeographic studies because Pristimantis spp. are direct developing and generally have narrow ecological niches and low dispersal abilities. The P. unistrigatus species group is one of the most important components in the genus (ca. 200 recognized species) and has been supported by morphological but not by molecular evidence. We assessed the species boundaries and distribution in the P. unistrigatus species group and infer spatiotemporal patterns of diversification related to historical landscape changes in the Neotropics. We gathered three mitochondrial, and two nuclear DNA loci from 416 specimens throughout the range of the group, and including 68 nominal species. We redefine the group based on the obtained phylogeny and found 151 candidate species that composes it, with 83 of these remaining undescribed. We recovered 11 major clades within the group that diverged before 13 Ma. The diversification of the group started during the early Miocene most likely in northwestern South America, currently corresponding to western Amazonia and northern Andes. The other neotropical areas subsequently acted as sinks, receiving lineages mostly during the last 10 Ma, after the demise of the Pebas System and the setup of the modern Amazonian hydrographic system.

Late Pleistocene polar bear genomes reveal the timing of allele fixation in key genes associated with Arctic adaptation

The polar bear (Ursus maritimus) occupies a relatively narrow ecological niche, with many traits adapted for cold temperatures, movement across snow, ice and open water, and for consuming highly lipid-dense prey species. The divergence of polar bears from brown bears (Ursus arctos) and their adaptation to their Arctic lifestyle is a well-known example of rapid evolution. Previous research investigating whole genomes uncovered twelve key genes that are highly differentiated between polar and brown bears, show signatures of selection in the polar bear lineage, and are associated with polar bear adaptation to the Arctic environment. Further research suggested fixed derived alleles in these genes arose from selection on both standing variation and de novo mutations in the evolution of polar bears. Here, we reevaluate these findings based on a larger and geographically more representative dataset of 119 polar bears and 135 brown bears, and assess the timing of derived allele fixation in polar bears by incorporating the genomes of two Late Pleistocene individuals (aged 130–100,000 years old and 100–70,000 years old). In contrast with previous results, we found no evidence of derived alleles fixed in present-day polar bears within the key genes arising from de novo mutation. Most derived alleles fixed in present-day polar bears were also fixed in the Late Pleistocene polar bears, suggesting selection occurred prior to 70,000 years ago. However, some derived alleles fixed in present-day polar bears were not fixed in the two Late Pleistocene polar bears, including at sites within APOB, LYST, and TTN. These three genes are associated with cardiovascular function, metabolism, and pigmentation, suggesting selection may have acted on different loci at different times.

Trophic guilds and niche segregation among marine megafauna in the Bay of Biscay

The structure and functioning of ecosystems are largely determined by the interactions between species within a biological community. Among these interactions, species exhibiting similar vertical and spatial prey preferences can be identified, thereby belonging to the same trophic guild. Our study explored some trophic characteristics of a diverse megafaunal community (cetaceans, tunas, seabirds) in the Bay of Biscay (BoB). Using stable isotope analysis (SIA), we explored the dietary habits and niche overlap among predators. The degree of isotopic niche overlap was generally low, but with certain species exhibiting large and narrow isotopic niche areas (long-finned pilot whales and Balearic shearwaters, respectively). Our results revealed a diversity of dietary preferences leading to the identification of three distinct trophic guilds based on prey functional groups and spatial preferences: cephalopod feeders (e.g. long-finned pilot whales, Cuvier's beaked whales, striped dolphins), crustacean feeders (e.g. fin whales, albacores), and piscivores (e.g. common dolphins, harbour porpoises, bottlenose dolphins, Atlantic bluefin tunas, Balearic shearwaters). Our findings showed resource partitioning and niche differentiation among the megafaunal community, highlighting the complexity of BoB's marine ecosystem. The insights derived from this study hold important implications for ecosystem management and the implementation of conservation initiatives.

Individual isotopic niche variation of herbivores and palaeoenvironmental reconstruction of the Mid-Pleistocene Site of Kathu Pan 1 (South Africa)

Individual niche variation occurs when individuals within a population adopt unique behavioural or ecological traits, giving the population a distinct niche structure. Although widespread amongst natural populations, most of niche theory and its applications in ecological and palaeoenvironmental contexts remains focused on species level patterns, treating variation within the population as noise. Using serial stable isotope profiles sampled along teeth of herbivore fossils recovered from the Mid-Pleistocene site of Kathu Pan 1, Northern Cape (South Africa), enabling partitioning of isotopic niche variation into between- and within-individual components. Stable carbon isotope data revealed significant dietary differences between-individuals within most of the taxa sampled, but no dietary differences between taxa. By contrast, stable oxygen isotope compositions were more consistent amongst individuals, but varied across taxa. In both isotope systems, as well as in bivariate space, most taxa comprised individuals with both narrow and broad isotope niches, indicating flexibility in dietary strategies. These results indicate sufficient opportunity for individual level specialization within the Kathu palaeocommunity, afforded by a palaeoenvironment that provided a consistent supply of resources year-round. Given the herbivore sample is strongly associated with fossil hominin activities, our results imply that hominins in these landscapes would have profited from year-round accessibility to resources, accounting for the record of occupancy of Kathu Pan I during the Mid-Pleistocene.

Characterization of the Ecological Niche and Interspecific Connectivity of Plankton in Baiyangdian Lake by Combining Ecological Networks

To understand the structure of the plankton community and the ecological niche characteristics of their dominant species, sampling surveys of plankton were conducted in Baiyangdian Lake in the spring （March）, summer （July）, and autumn （September） of 2022. The changes in the plankton community during the three seasons were analyzed by constructing ecological network diagrams, non-metric multidimensional scaling analysis （NMDS）, and the ecological niche width. The niche overlap of zooplankton dominant species was evaluated by the improved Levins' formula and Petraitis' index. The interspecific connectivity of dominant species was judged using the chi-square test and interspecies connectivity coefficients. The results showed that the niche width of plankton in the whole area was low. Zooplankton was dominated by rotifers, and phytoplankton was dominated by diatoms, cyanobacteria, and green algae. There were significant seasonal changes in the community structures of plankton. Compared with that in summer and autumn, there were fewer species of plankton in spring and lower interspecies connectivity. The overlap of dominant species of zooplankton was high in summer, and the interspecific competition was intensified, whereas the interspecific overlap of phytoplankton was at a low level in all three seasons. There was a significant positive correlation （W > χ20.05） between phytoplankton in summer and autumn, and the community structure was stable. The interdomain ecological network of zooplankton and phytoplankton showed a high negative correlation ratio in autumn, especially between copepods and cladoceras of zooplankton and chlorophyta and cyanophyta of phytoplankton. The plankton species in Baiyangdian Lake were abundant, with obvious seasonal differences. The dominant species were mainly a narrow ecological niche. The plankton community was generally in a stable state, and there was a strong predation relationship between copepods and cladoceras and green algae and cyanobacteria.

Damming of streams due to the construction of a highway in the Amazon rainforest favors individual trophic specialization in the fish (Bryconops giacopinii).

In Amazonian streams, damming caused by road construction changes the system's hydrological dynamics and biological communities. We tested whether the degree of specialization in fish (Bryconops giacopinii) individuals is higher in pristine stream environments with intact ecological conditions than in streams dammed due to the construction of a highway in the Amazon rainforest. To achieve this, stomach content data and stable isotopes (δ13C and δ15N) in tissues with varying isotopic incorporation rates (liver, muscle, and caudal fin) were used to assess the variation in consumption of different prey over time. The indices within-individual component (WIC)/total niche width (TNW) and individual specialization were employed to compare the degree of individual specialization between pristine and dammed streams. The condition factor and stomach repletion of sampled individuals were used to infer the intensity of intraspecific competition in the investigated streams. The species B. giacopinii, typically considered a trophic generalist, has been shown to be, in fact, a heterogeneous collection of specialist and generalist individuals. Contrary to our expectations, a higher degree of individual specialization was detected in streams dammed by the highway. In dammed streams, where intraspecific competition was more intense, individuals with narrower niches exhibited poorer body conditions than those with broader niches. This suggests that individuals adopting more restricted diets may have lower fitness, indicating that individual specialization may not necessarily be beneficial for individuals. Our results support the notion that intraspecific competition is an important mechanism underlying individual specialization in natural populations. Our results suggest that environmental characteristics (e.g., resource breadth and predictability) and competition for food resources interact in complex ways to determine the degree of individual specialization in natural populations.

Reclamation of abandoned cropland switches fungal community assembly from deterministic to stochastic processes

Soil microbial communities are major drivers of cycling of soil nutrients that sustain plant growth and productivity. Yet, a holistic understanding of the impact of abandoned agricultural land reclamation on the soil microbe is still poorly understood, especially for the microbial community assembly mechanisms. Here, we investigated the influence of reclamation on the relative importance of stochastic and deterministic processes in shaping microbial community assembly. After reclaiming abandoned cropland for corn and soybean cultivation, the fungal community assembly was shifted to stochastic processes, while bacterial communities remained predominantly influenced by stochastic processes. Our study revealed that reclamation did not significantly affect bacterial diversity, community niche breadth, and community similarity. In contrast, fungal communities exhibited lower alpha diversity, narrower niche breadths, greater niche overlap and higher community similarity in corn and soybean cultivation treatment in response to reclamation. Moreover, soil pH and soil available phosphorus were the most important environmental factors influencing fungal richness, niche breadths, community assembly processes, and community similarity. Together, the reclamation of abandoned cropland promoted the transformation of the fungal community assembly from deterministic process to a stochastic process, leading to decreased fungal diversity and broader ecological niche width, ultimately resulting in greater similarity among fungal communities. This finding provides insight into the varied responses of microbial diversity and ecological process to abandoned cropland reclamation, offering valuable guidance for the conservation and sustainable management of abandoned cropland in future land-use practices.

Interspecific competition shapes bird species' distributions along tropical precipitation gradients.

The hypothesis that species' ranges are limited by interspecific competition has motivated decades of debate, but a general answer remains elusive. Here we test this hypothesis for lowland tropical birds by examining species' precipitation niche breadths. We focus on precipitation because it-not temperature-is the dominant climate variable that shapes the biota of the lowland tropics. We used 3.6 million fine-scale citizen science records from eBird to measure species' precipitation niche breadths in 19 different regions across the globe. Consistent with the predictions of the interspecific competition hypothesis, multiple lines of evidence show that species have narrower precipitation niches in regions with more species. This means species inhabit more specialized precipitation niches in species-rich regions. We predict this niche specialization should make tropical species in high diversity regions disproportionately vulnerable to changes in precipitation regimes; preliminary empirical evidence is consistent with this prediction.

Aridity shapes distinct biogeographic and assembly patterns of forest soil bacterial and fungal communities at the regional scale

Climate change is exacerbating drought in arid and semi-arid forest ecosystems worldwide. Soil microorganisms play a key role in supporting forest ecosystem services, yet their response to changes in aridity remains poorly understood. We present results from a study of 84 forests at four south-to-north Loess Plateau sites to assess how increases in aridity level (1- precipitation/evapotranspiration) shapes soil bacterial and fungal diversity and community stability by influencing community assembly. We showed that soil bacterial diversity underwent a significant downward trend at aridity levels >0.39, while fungal diversity decreased significantly at aridity levels >0.62. In addition, the relative abundance of Actinobacteria and Ascomycota increased with higher aridity level, while the relative abundance of Acidobacteria and Basidiomycota showed the opposite trend. Bacterial communities also exhibited higher similarity-distance decay rates across geographic and environmental gradients than did fungal communities. Phylogenetic bin-based community assembly analysis revealed homogeneous selection and dispersal limitation as the two dominant processes in bacterial and fungal assembly. Dispersal limitation of bacterial communities monotonically increased with aridity levels, whereas homogeneous selection of fungal communities monotonically decreased. Importantly, aridity also increased the sensitivity of microbial communities to environmental disturbance and potentially decreased community stability, as evidenced by greater community similarity-environmental distance decay rates, narrower habitat niche breadth, and lower microbial network stability. Our study provides new insights into soil microbial drought response, with implications on the sustainability of ecosystems under environmental stress.

Feeding Habits and Prey Composition of Six Mesopelagic Fish Species from an Isolated Central Mediterranean Basin

Mesopelagic fishes hold an important position in marine food webs, serving as a link between lower trophic levels and top predators and transferring energy from their deep mesopelagic habitat to shallower oceanic layers. Despite their ecological importance, research on mesopelagic fishes’ diet and feeding habits in the Mediterranean Sea is far from thorough. The present work attempts to assess the preying patterns and diet composition of four myctophid (Benthosema glaciale, Ceratoscopelus maderensis, Myctophum punctatum, Notoscopelus elongatus) and two sternoptychid (Argyropelecus hemigymnus, Maurolicus muelleri) species from the Corinthian Gulf (Ionian Sea, Greece), sampled during pelagic trawl surveys in 2018 and 2019. Stomach vacuity was high for myctophids caught during daytime, a pattern which sternoptychids did not follow. Estimated trophic indices revealed high dietary diversity (Shannon’s H’ index) for most investigated species, but a narrow trophic niche breadth (Levins’ normalized Bn index). Copepods and various marine crustaceans were dominant in all diets, classifying them under the zooplanktivorous trophic guild, while A. hemigymnus exhibited high concentrations of particulate organic matter in their stomachs and N. elongatus exhibited consumption of fish. Diet overlap was significant among most studied mesopelagic species, as indicated by Shoener’s S index and confirmed by both the multidimensional scaling ordination and a hierarchical cluster analysis. Information on mesopelagic fishes’ diet composition in this poorly studied part of the Mediterranean is useful in further assessing and parameterizing marine food webs and midwater trophic interactions, as well as in quantifying the ensued energy transfer to top predators of commercial interest or conservation concerns.

Gyrfalcon Disease Ecology: A Survey Across Western Alaska

ABSTRACT The Gyrfalcon (Falco rusticolus) is a top avian predator, an Arctic specialist, and among the bird species most vulnerable to climate change. This vulnerability is driven by their narrow ecological niche, limited or lack of southward migration, and circumpolar distribution where the most rapid climatic changes are occurring. Climatic and habitat changes may alter Gyrfalcon disease ecology due to changes in vector distributions, host ranges, and pathogen life cycles. Warmer Arctic temperatures and accompanying landscape changes may also alter the Gyrfalcon’s prey base, and dietary habits can influence transmission of pathogens. To better understand disease ecology in Gyrfalcons, we compared pathogen prevalence across varying time periods at three study sites in Alaska—the Seward Peninsula (2014–2022), the Alaska Peninsula (2021–2022), and the Yukon–Kuskokwim Delta (2008–2013). We collected Gyrfalcon whole blood, thin blood films, cloacal swabs, and fecal samples for serology, haemoparasite assays, microbiological cultures, and fecal tests for parasites. An aliquot of whole blood preserved on filter paper or in Longmire solution was kept for molecular diagnosis of haemoparasites. Serology revealed high exposure to Salmonella (77%), low seroprevalence of avian influenza antibodies (1.5%), exposure to falcon adenovirus type 1 in hatch-year Gyrfalcons (1.3%), and the first report of a Leucocytozoon spp. blood parasite in a Gyrfalcon. We found no antibodies indicative of prior exposure to avian paramyxovirus, West Nile virus, or Chlamydia. One nestling and one hatch-year bird sampled (2 of 12) on the Seward Peninsula exhibited oral plaques from capillarids (Eucoelus spp.) in contrast to those trapped in the Izembek National Wildlife Refuge on the Alaska Peninsula (0 of 6).

Інноваційні стратегії сталого розвитку підприємств в умовах мінливого ринку

The article analyzes various approaches to innovation development for enterprises operating in volatile markets. It explores critical innovation strategies, including proactive, reactive, imitative, niche, mergers and acquisitions (M&A), open innovation, incremental, and radical strategies. The proposed utilization of these strategies aims to ensure sustainable development for enterprises, considering their specific activities and market conditions. Proactive Strategies are characterized by their focus on anticipating and shaping market trends—proactive strategies position companies as market leaders by developing new products and services ahead of market demand. Analyzing technological trends and innovations is highlighted, enabling enterprises to maintain a competitive edge by staying ahead of competitors. Reactive strategies, however, adapt to changes in market and consumer demand. This approach involves responding swiftly to market shifts and competitive innovations. Imitative Strategies involve replicating or adapting innovations introduced by other companies. Niche Strategies concentrate on serving narrow market segments or specific technological niches. Companies utilizing niche strategies aim to become specialists in their chosen fields, offering unique solutions tailored to specific customer needs. This approach requires deep understanding, specialization, and expertise, allowing enterprises to command premium prices due to the distinctiveness of their products or services. This approach accelerates innovation processes by integrating external capabilities while reducing competitive pressures. However, successful implementation of M&A strategies demands meticulous planning and effective management to achieve synergy between organizations. In conclusion, the article offers a comprehensive framework for selecting and implementing innovative strategies tailored to enterprises’ specific needs and conditions in dynamic market environments. By strategically applying these approaches, enterprises can enhance their innovation capabilities, adapt to market changes effectively, and achieve sustainable development in the long term. Keywords: innovation strategies, sustainable development, dynamic market, proactive strategies, reactive strategies, imitative strategies, niche strategies, mergers and acquisitions, open innovation, incremental strategies, radical strategies, university partnerships, R&D, competitive advantage, market stability.

No evidence for niche competition in the extinction of the South American saber-tooth species

The end of South American isolation during the Great American Biotic Interchange (GABI) promoted the contact between South and North American saber-tooth forms that evolved in isolation. This contact may have driven saber-tooth species to a competitive interaction, resulting in the extinction of the South American saber-tooth form. Here, we used paleoclimatic data to compare the climatic niche of the saber-tooth forms Thylacosmilus atrox (from South America), Smilodon fatalis, and Smilodon populator (both originally from North America). We evaluated niche width, overlap, and similarity to infer potential geographic distribution overlap and competition between these North and South American predators. To do so, we obtained the climatic variables from sites where occurrence fossil records were available. Our results suggest that T. atrox had a narrower climatic niche compared to Smilodon species. Although we found a significant climatic niche overlap and similarity between S. fatalis and T. atrox, it seems unlikely that both species have co-occurred. Low niche overlap and similarity between T. atrox and S. populator dismiss competitive interaction between them. Moreover, climatic niche and low tolerance for environmental changes may have been the cause of the South American saber-tooth extinction.

Larval and adult morphology of Photuris elliptica Olivier (Coleoptera, Lampyridae) and a Halloweeny case of cave-dwelling firefly larva feeding on bat guano

The predatory firefly Photuris elliptica is common throughout the Atlantic Forest and has been proposed as a biomonitor due to the species’ narrow niche and elevational range. However, the species is only known from adults, and a more effective monitoring of its populations hinges on the lack of knowledge on their immature stages. Recent sampling in ferruginous caves and inserted in other lithologies, on sites in the Atlantic Forest and Cerrado, have led to the capture of firefly larvae later reared to adults in the lab. Firefly larvae have been reported in South American caves before; however, they have only been identified to family due to the adult-biased taxonomy of Lampyridae. Here, we provide an updated diagnosis of Photuris elliptica, describe its immature stages for the first time, and update the distribution of the species. The larvae of Photuris elliptica were observed to interact with guano of several bat species, including that of vampire bats. These observations are consistent with the less specialized feeding preferences of photurine larvae, unlike most other firefly taxa, which specialize in gastropods and earthworms. It is yet unclear whether P. elliptica are cave specialists. However, since its occurrence outside caves remains unknown, protecting cave environments must be considered in conservation strategies for this important biomonitor species.

Unveiling differential thermal sensitivities in marine phytoplankton within the China Seas

AbstractIn this study, we explored the realized thermal sensitivities of various phytoplankton groups in natural seawater, a crucial aspect for understanding the dynamics of marine ecosystems under climate change. Utilizing a decadal pigment dataset (2002–2015) from China Seas and employing generalized additive mixed models coupled with maximum entropy modeling, we discerned thermal sensitivity differentiations among nine phytoplankton groups, encompassing the full‐size spectrum. Our findings revealed that cryptophytes were exceptionally thermally sensitive, with a strong correlation between temperature changes and biomass variance. Characterized by a preference for cooler waters, cryptophytes had a low mean temperature niche and a narrow niche breadth. Notably, they exhibited the lowest temperature tipping point, highlighting their heightened vulnerability to warming trends. These findings underscored the significance of cryptophytes, an often‐overlooked group, in understanding ecosystem responses to climate shifts, and emphasized their potential role as key indicators in marine ecological studies under global warming.

Predicting suitable habitat for the endangered tree Ormosia microphylla in China

Climate change has significantly influenced the growth and distribution of plant species, particularly those with a narrow ecological niche. Understanding climate change impacts on the distribution and spatial pattern of endangered species can improve conservation strategies. The MaxEnt model is widely applied to predict species distribution and environmental tolerance based on occurrence data. This study investigated the suitable habitats of the endangered Ormosia microphylla in China and evaluated the importance of bioclimatic factors in shaping its distribution. Occurrence data and environmental variables were gleaned to construct the MaxEnt model, and the resulting suitable habitat maps were evaluated for accuracy. The results showed that the MaxEnt model had an excellent simulation quality (AUC = 0.962). The major environmental factors predicting the current distribution of O. microphylla were the mean diurnal range (bio2) and precipitation of the driest month (bio14). The current core potential distribution areas were concentrated in Guangxi, Fujian, Guizhou, Guangdong, and Hunan provinces in south China, demonstrating significant differences in their distribution areas. Our findings contribute to developing effective conservation and management measures for O. microphylla, addressing the critical need for reliable prediction of unfavorable impacts on the potential suitable habitats of the endangered species.

Construction of biochar-based organohalide-respiring bacterial agent for remediation of 2,4,6-trichlorophenol contaminated soil

Construction of an efficient bio-reductive dechlorination system remains challenging due to the narrow ecological niche and low-growth rate of organohalide-respiring bacteria during field remediation. In this study, a biochar-based organohalide-respiring bacterial agent was obtained, and its performance and effects on indigenous microbial composition, diversity, and inter-relationship in soil were investigated. A well-performing material, Triton X-100 modified biochar (BC600-TX100), was found to have the superior average pore size, specific surface area and hydrophicity, compared to other materials. Interestingly, Pseudomonas aeruginosa CP-1, which is capable of 2,4,6-TCP dechlorination, showed a 348 times higher colonization cell number on BC600-TX100 than that of BC600 after 7 d. Meanwhile, the dechlorination rate in soil showed the highest (0.732 d−1) in the BC600-TX100 bacterial agent than in the other agents. The long-term performance of the BC600-TX100 OHRB agent was also verified, with a stable dechlorination activity over six cycles. Soil microbial community analysis found the addition of the BC600-TX100 OHRB agent significantly increased the relative abundance of genus Pseudomonas from 1.53 % to 11.2 %, and Pseudomonas formed a close interaction relationship with indigenous microorganisms, creating a micro-ecological environment conducive to reductive dechlorination. This study provides a feasible bacterial agent for the in-situ bioremediation of soil contaminated organohalides. Environmental ImplicationHalogenated organic compounds are a type of toxic, refractory, and bio-accumulative persistent compounds widely existed in environment, widely detected in the air, water, and soil. In this study, we provide a feasible bacterial agent for the in-situ bioremediation of soil contaminated halogenated organic compounds. The application of biochar provides new insights for “Turning waste into treasure”, which meets with the concept of green chemistry.

Increasing duration of heatwaves poses a threat to oyster sustainability in the Gulf of Mexico

The future of the wild oyster fishery in the northern Gulf of Mexico is largely uncertain due to changing environmental conditions and declining abundance of harvestable oysters. Specifically, rising temperatures can directly impact the physiological thresholds of the eastern oyster (Crassostrea virginica) at all life history stages and alter the narrow ecological niche this oyster occupies. The impact of rising temperatures is likely most pronounced during atmospheric heatwaves, defined as three or more days above the 90th percentile of daily maximum air temperatures, which have been shown to be increasing in frequency. Increasing exposure to high temperature extremes may contribute to and exacerbate an already declining oyster fishery. Critical to fishery health is recruitment i.e., the addition of new harvestable biomass, which is a dynamic process strongly driven by temperature. Here, we examine the relationship between heatwave characteristics and the prediction of poor oyster recruitment, measured as the abundance of post-larval oysters (e.g. spat) below the site-specific median density observed in historically productive oyster fisheries over 46-years (1976 – 2020) in Mobile Bay, Alabama and 21-years (1993 – 2014) in Apalachicola Bay, Florida. We acquired daily maximum air temperature measurements measured over 50 years (1970 – 2020) at weather monitoring stations adjacent to the bays to identify site specific annual heatwave events (maximum yearly air temperature, yearly and consecutive heatwave days, and number of annual heatwaves). Then, years with extreme heatwaves that exceeded the 75th percentile for the 50-year measurements were compared to years with non-extreme heatwave events. Years with extreme total heatwave days and extreme consecutive heatwave days were correlated with low post-larval oyster density. Across both bay systems, if consecutive heatwave days exceeded 11 days, then poor recruitment of oysters occurred 83 % of the time. Extreme heatwave duration as an indicator for poor recruitment has the potential to be a powerful tool for fishery managers to forecast recruitment and inform sustainable oyster harvest based on year-to-year variability in heatwave duration and long-term warming trends. Our findings illustrate how extreme temperatures can exacerbate multiple physiological and ecological stressors resulting in the loss of a keystone species for healthy and resilient coastal ecosystems.