Abiotic Conditions Research Articles

Undesirable woody establishment is driven by herbaceous cover phylogenetics and abiotic conditions

Undesirable woody establishment is driven by herbaceous cover phylogenetics and abiotic conditions

Prickly postglacial pioneers: freshwater plankton community composition influences fatty acid desaturase (FADS2) copy number in southern Greenland threespine sticklebacks

The adaptation of marine fish to freshwater environments includes prodigious examples of rapid evolution.Given the scarcity of ω‐3 long‐chain polyunsaturated fatty acids (LC‐PUFA) in freshwater, we expect selection to be strong on fish transitioning to freshwater habitats and yet the underlying ecological causes of genomic and phenotypic differentiation are poorly understood for traits associated with lipid content and composition. Threespine stickleback Gasterosteus aculeatus have repeatedly colonized, and adapted to, freshwater habitats across the Northern Hemisphere. These freshwater populations often show elevated copy number of the fatty acid desaturase 2 gene (FADS2), which increases the biosynthetic capacity of LC‐PUFA. The starkly lower content of LC‐PUFA in freshwater compared to marine prey, especially docosahexaenoic acid (DHA), likely imposes strong positive selection on freshwater fish for either increased biosynthesis or greater dietary acquisition of LC‐PUFA. The recently colonized and relatively undisturbed threespine stickleback populations in postglacial coastal lakes of southern Greenland offer an exceptional opportunity to study how variation in the copy number of FADS2 is related to abiotic and biotic conditions of lakes and their morphometry. As expected, given its position on the stickleback X chromosome, we found strong sexual dimorphism in FADS2 copy number in all populations (19 freshwater, 1 marine and 1 brackish), and an increased dimorphism in some freshwater populations. We also found that FADS2 copy number was negatively correlated, for both males and females, with the abundance of copepods, which are a DHA‐rich food source in the zooplankton community. Overall, our results suggest that the prey community context of lakes might influence the process of metabolic adaptation of marine fish colonizing freshwater ecosystems.

Genome-Wide Analysis of HECT E3 Ligases Members in Phyllostachys edulis Provides Insights into the Role of PeHECT1 in Plant Abiotic Stress Response

Homology to E6-AP Carboxy Terminus (HECT) E3 ubiquitin ligases play pivotal roles in plant growth, development, and responses to abiotic stresses. However, the function of HECT genes in Phyllostachys edulis (P. edulis) remains largely uninvestigated. In this study, a comprehensive genome-wide analysis of the HECT E3 ubiquitin ligases gene family in P. edulis was conducted, aiming to elucidate its evolutionary relationships and gene expansion. Analysis of gene structure, conserved motifs and domains, and synteny genome regions were performed. Furthermore, cis-elements in HECT gene promoters that respond to plant hormones and environmental stresses were identified and corroborated by expression data from diverse abiotic stress conditions and hormone treatments. Based on the co-expression network of PeHECTs under cold and dehydration stresses, PeHECT1 was identified as a key candidate gene associated with abiotic stress tolerance. Overexpression of PeHECT1 in tobacco leaves significantly upregulated genes related to reactive oxygen species (ROS) detoxification and polyamine biosynthesis. Yeast one-hybrid (Y1H), electrophoretic mobility shift assay (EMSA), and dual-luciferase (dual-LUC) assays suggested that the transcription factor ETHYLENE RESPONSE FACTOR 3 (PeERF3) bound to the dehydration-responsive element (DRE) of the promoter of PeHECT1 and activated its transcription activity. Phylogenetic analysis indicated that PeHECT1 in P. edulis exhibited a close association with the diploid herbaceous bamboo Olyra latifolia, followed by the divergence of rice and bamboo. In summary, this study enhances our comprehensive understanding of the HECT E3 ubiquitin ligases gene family in P. edulis and highlights the potential role of PeHECT1 in plant abiotic stress response.

Responses of Legumes to Rhizobia and Arbuscular Mycorrhizal Fungi Under Abiotic Stresses: A Global Meta-Analysis

Arbuscular mycorrhizal fungi (AMF) and rhizobia play a pivotal role in enhancing crop productivity, shaping microbial community structure, and improving soil quality, making them key components for sustainable ecosystem development. The symbiotic relationship between AMF and rhizobia is crucial for facilitating efficient biological nitrogen fixation and nutrient absorption, thereby reducing the dependence on chemical fertilizers and promoting sustainable agricultural practices. The findings of various studies, however, indicate that soil environment can impede the symbiotic relationship between AMF and rhizobia. We conducted a comprehensive meta-analysis of 158 articles from 1980 to 2022 to explore the synergistic interactions in legume–AMF–rhizobium systems and the potential mechanisms underlying this synergism. Our findings revealed that the inoculation with AMF and/or rhizobia significantly (p < 0.001) increased legume plant nitrogen content, phosphorus content, shoot biomass, yield, AMF colonization rate, and the number and weight of nodules compared to uninoculated controls (effect size d > 0). Moreover, there was a substantial synergistic effect between AMF and rhizobia (p < 0.001). Nevertheless, soil salinity stress, drought stress, and pH stress could hinder the positive effects of inoculation treatments, possibly due to the plant trade-off strategies under abiotic stress conditions. This research may potentially lead to new solutions for sustainable agricultural systems amidst the challenges posed by global climate change.

Adaptation to different temperatures results in wing size divergence of the invading species Drosophila nasuta (Diptera: Drosophilidae) in Brazil.

Invasive species threaten biodiversity on a global scale. The success of invasions depends on the species' adaptation to the different environmental conditions of new territories. Studies show that invasive insects present evolutionary changes in wing morphology in areas they are introduced to in response to abiotic conditions. In the last decade, the Asian Drosophila nasuta fly invaded and spread widely throughout Brazil. This insect has preferences for conserved environments and is related to the likely reduction in the abundance of native drosophilids in the Atlantic Forest. Ecological niche modelling analyses showed that rainfall and temperature are the main factors which delimit the geographic distribution of this species. Herein, we verified the existence of significant differences in the wing sizes of D. nasuta in Brazil and evaluated the influence of abiotic factors (rainfall and temperature) on the observed patterns. We conducted 11 measurements on the right-side wings of 240 D. nasuta males collected in the Amazon Forest, Caatinga, Cerrado and Atlantic Forest. Statistical analyses revealed the existence of two groups: one with larger wings, which brought together samples from locations with the lowest temperatures; and one with smaller wings, which corresponded to places with a hotter climate. One explanation for this result is the fact that large wings favour greater heat capture by flies in colder climates, increasing their survival chances in these environments. These rapid evolutionary changes in D. nasuta in this first decade of invasion in Brazil reveal the enormous adaptive potential of this species in this megadiverse country.

Uranium and arsenic bioremediation potential of plastic associated multi-metal tolerant Bacillus sp. EIKU23

Plastic waste accumulation is a significant environmental concern as it promotes microbial growth and acts as a carrier for heavy metals. This study focuses on a Bacillus sp. strain isolated from the surface of a used plastic bottle, tolerant to various potential toxic elements (PTEs) such as chromium, nickel, cobalt, copper, zinc, arsenite [As(III)], but sensitive to uranium (U) and arsenate [As(V)] toxicity. The strain demonstrates growth under different abiotic stress conditions, with the optimal pH range of 5.0-8.0 and a temperature of 30 °C. It shows remarkable removal capabilities, removing >23.3% of U, >38% of As(III)), and >22.6% of As(V) from an initial dose of 100mgL−1 in an aqueous solution. The biosorption capacity for U, As(III), and As(V) is 3.12, 3.1, and 1.8mgg−1 of biomass, respectively. Kinetic modelling suggests that the biosorption of U and As(V) follows a pseudo-second-order mechanism, while As(III) biosorption follows a pseudo-first-order mechanism. Moreover, the strain has the ability to precipitate >38.1% and ~67% of U using bacterially released phosphate from inorganic and organic sources, respectively. These findings highlight the strain's potential for bioremediation of PTE-contaminated environments, providing valuable insights for optimizing metal removal and immobilization processes in future research.

Developmental reaction norms vary among families of lizards in response to multivariate nest environments

Developmental plasticity is the capacity of a single genotype to express multiple phenotypes in response to different early‐life environments. Such responses are defined by reaction norms, which may vary among individuals or populations. Variation in developmental reaction norms allows natural selection to operate on plasticity and is rarely examined in vertebrates. We quantified variation in embryonic developmental plasticity within and between populations using the brown anole lizard. We captured lizards from two islands in the Matanzas River (Florida, USA) and incubated their eggs under one of two multivariate treatments that mimicked the temperature, moisture and substrates of nest sites in either a shaded or open habitat. We measured hatchling morphology, performance, and physiology to quantify variation in family‐level reaction norms. We observed evidence of family‐level variation in reaction norms for morphology but not for performance or physiology, indicating an opportunity for natural selection to shape plasticity in hatchling body size. Overall, the results indicate that multiple abiotic conditions in natural nests combine to increase or reduce phenotypic variation, and that family‐level variation in reaction norms provides a potential for natural selection to shape plasticity.

Potential Use of Algae and Seaweed Extracts as Protection Against Peach Leaf Curl

Abstract Plant pathogenic fungi are a major cause of plant diseases, contributing significantly to the global decline in food production. Their proliferation results in substantial crop losses, fruit and vegetable deterioration, reduced food accessibility, and billions of dollars in economic losses annually. While synthetic chemical fungicides are commonly used to combat fungal diseases, their environmental impact is concerning. Marine algae provide a sustainable alternative, offering diverse compounds with industrial applications and presenting an eco-friendly solution. Taphrina deformans is responsible for peach leaf curl, a widespread disease in peach trees that can severely impact crop productivity and tree lifespan. Seaweeds and algae, encountering various biological interactions and extreme abiotic conditions, have evolved defense mechanisms, including the production of biologically active substances. In our study, we investigated the efficacy of water extracts from six algae (Nannochloropsis sp., Tetraselmis chuii, Chaetoceros muelleri, Thalassiosira weissflogii, Tisochrysis lutea, Chlorella vulgaris), four seaweeds (Palmaria palmata, Chondrus crispus, Ascophyllum nodosum), and one cyanobacterium (Arthrospira platensis) at two different concentrations (1% and 3%) in suppressing the outbreak of peach leaf curl disease in vivo on peach trees. The spray was applied twice in spring just before budbreak. Algae and seaweed extracts showed significant suppression of peach leaf curl outbreaks on peach trees compared to controls. Following the application of water extract of Chlorella vulgaris at both concentrations, the lowest incidences of symptomatic disease expression were observed (1.00 ±0.00% and 0.25 ±0.50%). Algae and seaweed extracts demonstrate potential in controlling leaf curl disease in peach trees.

Defaunation impacts on the carbon balance of tropical forests.

The urgent need to mitigate and adapt to climate change necessitates a comprehensive understanding of carbon cycling dynamics. Traditionally, global carbon cycle models have focused on vegetation, but recent research suggests that animals can play a significant role in carbon dynamics under some circumstances, potentially enhancing the effectiveness of nature-based solutions to mitigate climate change. However, links between animals, plants, and carbon remain unclear. We explored the complex interactions between defaunation and ecosystem carbon in Earth's most biodiverse and carbon-rich biome, tropical rainforests. Defaunation can change patterns of seed dispersal, granivory, and herbivory in ways that alter tree species composition and, therefore, forest carbon above- and belowground. Most studies we reviewed show that defaunation reduces carbon storage 0-26% in the Neo- and Afrotropics, primarily via population declines in large-seeded, animal-dispersed trees. However, Asian forests are not predicted to experience changes because their high-carbon trees are wind dispersed. Extrapolating these local effects to entire ecosystems implies losses of ∼1.6 Pg CO2 equivalent across the Brazilian Atlantic Forest and 4-9.2 Pg across the Amazon over 100 years and of ∼14.7-26.3 Pg across the Congo basin over 250 years. In addition to being hard to quantify with precision, the effects of defaunation on ecosystem carbon are highly context dependent; outcomes varied based on the balance between antagonist and mutualist species interactions, abiotic conditions, human pressure, and numerous other factors. A combination of experiments, large-scale comparative studies, and mechanistic models could help disentangle the effects of defaunation from other anthropogenic forces in the face of the incredible complexity of tropical forest systems. Overall, our synthesis emphasizes the importance of-and inconsistent results when-integrating animal dynamics into carbon cycle models, which is crucial for developing climate change mitigation strategies and effective policies.

Multiple resiliency metrics reveal complementary drivers of ecosystem persistence: An application to kelp forest systems.

Human-caused global change produces biotic and abiotic conditions that increase the uncertainty and risk of failure of restoration efforts. A focus of managing for resiliency, that is, the ability of the system to respond to disturbance, has the potential to reduce this uncertainty and risk. However, identifying what drives resiliency might depend on how one measures it. An example of a system where identifying how the drivers of different aspects of resiliency can inform restoration under climate change is the northern coast of California, where kelp experienced a decline in coverage of over 95% due to the combination of an intense marine heat wave and the functional extinction of the primary predator of the kelp-grazing purple sea urchin, the sunflower sea star. Although restoration efforts focused on urchin removal and kelp reintroduction in this system are ongoing, the question of how to increase the resiliency of this system to future marine heat waves remains open. In this paper, we introduce a dynamical model that describes a tritrophic food chain of kelp, purple urchins, and a purple urchin predator such as the sunflower sea star. We run a global sensitivity analysis of three different resiliency metrics (recovery likelihood, recovery rate, and resistance to disturbance) of the kelp forest to identify their ecological drivers. We find that each metric depends the most on a unique set of drivers: Recovery likelihood depends the most on live and drift kelp production, recovery rate depends the most on urchin production and feedbacks that determine urchin grazing on live kelp, and resistance depends the most on feedbacks that determine predator consumption of urchins. Therefore, an understanding of the potential role of predator reintroduction or recovery in kelp systems relies on a comprehensive approach to measuring resiliency.

Genetic loci associated with sorghum drought tolerance in multiple environments and their sensitivity to environmental covariables.

Climate change can limit yields of naturally resilient crops, like sorghum, challenging global food security. Agriculture under an erratic climate requires tapping into a reservoir of flexible adaptive loci that can lead to lasting yield stability under multiple abiotic stress conditions. Domesticated in the hot and dry regions of Africa, sorghum is considered a harsh crop, which is adapted to important stress factors closely related to climate change. To investigate the genetic basis of drought stress adaptation in sorghum, we used a multi-environment multi-locus genome-wide association study (MEML-GWAS) in a subset of a diverse sorghum association panel (SAP) phenotyped for performance both under well-watered and water stress conditions. We selected environments in Brazil that foreshadow agriculture where both drought and temperature stresses coincide as in many tropical agricultural frontiers. Drought reduced average grain yield (Gy) by up to 50% and also affected flowering time (Ft) and plant height (Ph). We found 15 markers associated with Gy on all sorghum chromosomes except for chromosomes 7 and 9, in addition to loci associated with phenology traits. Loci associated with Gy strongly interacted with the environment in a complex way, while loci associated with phenology traits were less affected by G × E. Studying environmental covariables potentially underpinning G × E, increases in relative humidity and evapotranspiration favored and disfavored grain yield, respectively. High temperatures influenced G × E and reduced sorghum yields, with a ~ 100kgha-1 average decrease in grain yield for each unit increase in maximum temperature between 29 and 38°C. Extreme G × E for sorghum stress resilience poses an additional challenge to breed crops for moving, erratic weather conditions.

Multi-omics approaches for abiotic stress tolerance in rice (Oryza sativa L.)

Rice, one of the world's staple crops, faces significant challenges due to abiotic stresses such as drought, salinity and extreme temperatures, which threaten global food security. Traditional breeding methods have limitations in developing stress-tolerant rice varieties within a short time frame. Thus, there is a growing interest in employing multi-omics approaches, integrating genomics, transcriptomics, proteomics, metabolomics and epigenomics, to unravel the complex molecular mechanisms underlying abiotic stress tolerance in rice. In contrast to a single-omics method, this combination of multi-dimensional approaches provides an extensive understanding of cellular dynamics under abiotic stress conditions. This review discusses recent advances in multi-omics technologies and their applications in dissecting the molecular responses of rice to abiotic stresses. It highlights the integration of multi-omics data to identify critical genes, pathways and regulatory networks involved in stress responses and tolerance mechanisms.Furthermore, it explores the potential of multi-omics-assisted breeding strategies for developing stress-tolerant rice varieties with improved agronomic traits. The challenges and future perspectives in utilizing multi-omics approaches to enhance rice's abiotic stress tolerance are also discussed. Overall, multi-omics approaches offer a comprehensive platform to understand the molecular basis of stress tolerance in rice and accelerate the development of resilient varieties to ensure global food security.

The Invertebrates of The Romualdo Formation, Araripe Basin: Analysis of Paleoecological and Paleogeographical Data

Fossil invertebrates are good paleoenvironmental indicators due to their sensitivity to abiotic conditions, which contributes to the understanding of the Aptian-Albian of the Araripe Basin. However, much of the paleoecological and paleobiogeographical information on these organisms is scarce in the literature. The aim of this paper is to compile relevant data on the macroinvertebrates of the Romualdo Formation and to analyze and point out gaps in knowledge. To achieve this, extensive bibliographical research was carried out, using scientific publications based on the families of Spinicaudata, echinoids, gastropods, bivalves, shrimps and crabs of the Romualdo Formation and their distribution in Brazil and globally throughout the Aptian-Albian, using specialized online databases. Paleoecological and paleogeographical data were compiled for 46 invertebrate taxa, highlighting those with better studied routes of origin. Thus, it was possible to highlight the lack of data regarding the way of life of certain mollusc families and systematic problems regarding the identification of the families of several species of shrimp. Finally, the predominance of taxa from marine (34), brackish (7) and lacustrine (5) waters was shown. Of these, 18 taxa have a typical tethyan distribution and another 12 also present occurrences in the Austral, Boreal or both domains. The only typical freshwater group was Spinicaudata, marking environments with little or no marine influence and with rare occurrences during the Aptian-Albian.

CRISPR/Cas9 mediated genome editing for crop improvement against Abiotic stresses: current trends and prospects.

Abiotic stresses associated with climate change, such as heat, cold, salinity, and drought, represent a serious threat to crop health. To mitigate the risks posed by these environmental challenges, both transgenic technology and conventional breeding methods have been extensively utilized. However, these methods have faced numerous limitations. The development of synthetic nucleases as precise genetic tools allows for the targeted alteration of stress-responsive genes in crop improvement. The clustered regularly interspaced short palindromic repeats (CRISPR/Cas) genome-editing technique has transformed gene editing with its broad applicability, accessibility, adaptability, flexibility, and simplicity. Its application shows promise for the development of crop types that are more able to survive abiotic stress conditions. The present study presents recent scenario and application of CRISPR/Cas genome-editing technology in enhancing crop tolerance to a variety of abiotic stresses.

Variability of plant transcriptomic responses under stress acclimation: a review from high throughput studies

Plant transcriptomes are complex entities shaped spatially and temporally by a multitude of stressors. The aim of this review was to summarize the most relevant transcriptomic responses to selected abiotic (UV radiation, chemical compounds, drought, suboptimal temperature) and biotic (bacteria, fungi, viruses, viroids) stress conditions in a variety of plant species, including model species, crops, and medicinal plants. Selected basic and applicative studies employing RNA-seq from various sequencing platforms and single-cell RNA-seq were involved. The transcriptomic responsiveness of various plant species and the diversity of affected gene families were discussed. Under stress acclimation, plant transcriptomes respond particularly dynamically. Stress response involved both distinct, but also similar gene families, depending on the species, tissue, and the quality and dosage of the stressor. We also noted the over-representation of transcriptomic data for some plant organs. Studies on plant transcriptomes allow for a better understanding of response strategies to environmental conditions. Functional analyses reveal the multitude of stress-affected genes as well as acclimatory mechanisms and suggest metabolome diversity, particularly among medicinal species. Extensive characterization of transcriptomic responses to stress would result in the development of new cultivars that would cope with stress more efficiently. These actions would include modern methodological tools, including advanced genetic engineering, as well as gene editing, especially for the expression of selected stress proteins in planta and for metabolic modifications that allow more efficient synthesis of secondary metabolites.

Litter Chemistry Is a Main Driver of Inorganic Nitrogen in Disturbed Soils in the Arid Patagonian Monte

ABSTRACTChanges in plant cover and soil characteristics induced by grazing may affect litter quality and nitrogen (N) release under varying abiotic conditions. Our study was focused on the importance of litter chemistry as a main driver of inorganic N (ammonium‐N: NH4+‐N and nitrate‐N: NO3−‐N) release to soil. Both inorganic N forms are important components for N availability to plants and soil processes, and the long‐term conservation of soil‐N fertility. We analyzed the effect of secondary compounds and the C/N ratio in litter under varying soil water, and UV exposure on soil inorganic N (NH4+‐N and NO3−‐N) in Patagonian Monte degraded soils. We hypothesized that secondary compounds and C/N ratio in litter are main drivers of soil inorganic N under varying abiotic conditions. We conducted a microcosm experiment (13 months) using intact upper soil blocks from denuded soil areas. Surface soils were added with shrub (SL), and mixed grass and shrub (GSL) litter with high versus low secondary metabolites concentration and low vs. high C/N ratio, respectively. Microcosms were maintained under ambient and reduced UV exposure, and high and low soil water. We used microcosms without litter as controls. Monthly, we assessed NH4+‐N and NO3−‐N concentrations in upper and sub‐superficial soils. Litter chemistry interacting with abiotic factors did not significantly influence soil NH4+‐N at any soil depth while litter chemistry was a main driver of NO3−‐N in upper soil. SL enhanced NO3−‐N in upper soil compared with GSL independently of abiotic factors. In upper soils without litter and in those with GSL, the highest NO3−‐N concentration occurred mostly under high soil water and exposition to UV. We concluded that litter chemistry was a main driver of soil N fertility in disturbed rangelands. Shrub litter may enhance N fertility (NO3−‐N) in degraded soils.

Phylogenomic analysis of glutamine synthetase gene family in Helianthus annuus L.

Glutamine synthetase is one of the predominant enzymes in nitrogen metabolism. In developing leaves, glutamine is mainly produced in chloroplasts by the activity of the GS2 isoenzyme. It catalyzes glutamine synthesis from glutamate and ammonia in an ATP-dependent reaction. The genes encoding glutamine synthetase play a crucial role in ammonia and glutamate detoxification, acid-base homeostasis, cell signaling, and cell proliferation. The gene family responsible for producing glutamine synthetase has been previously documented in model plants like Arabidopsis. Nevertheless, there has been no exploration into its existence and attributes in oilseed crops like sunflower (Helianthus annuus L.). This study thoroughly analyzes, gene structure, conserved motifs, chromosomal location, phylogenetic relationships, and expression patterns to identify the glutamine synthetase genes in H. annuus. Our findings unveiled 19 genes encoding glutamine synthetase within the H. annuus genome. These genes were distributed across 11 chromosomes of H. annuus. Furthermore, we examined the expression patterns of all the HaGS genes using RNA-seq datasets, specifically focusing on their response to biotic and abiotic stress conditions. Under biotic stress, H. annuus expresses genes for mycorrhizal fungi named Rhizoglomus irregulare at four days post inflorescence (dpi) and 16 dpi. Under abiotic stress, the effect of drought and hormones was investigated. In drought, one gene, HaGS6D, showed the highest expression in the leaf. Meanwhile, in roots, gene HaGS7B showed the highest expression. Under hormonal stress, the effects of auxin, brassinosteroid, and cytokinin were studied on the leaf. For auxin, the gene HaGS7C showed the highest expression. For brassinosteroid, the gene HaGS7D showed the highest expression; for cytokinin, the gene HaGS6E showed the highest expression. Thus, these findings can significantly contribute to our understanding of the arrangement of glutamine synthetase genes in H. annuus and offer valuable insights for developing of drought-resistant cultivars of this species.

Warm-adapted encroachment outpaces cool-adapted retreat in a hotspot of trailing-edge population diversity in the southern Appalachian Mountains, USA

Abstract Many populations near receding low-latitude range: margins are declining in response to climate change, but most studies of trailing-edge populations have focused on single species. Using 10 years (2014–2023) of avian survey data from a high-elevation trailing-edge population hotspot in the Appalachian Mountains, USA, we tested the hypothesis that high-elevation communities would experience turnover through thermophilisation, as warm-adapted species near the center of their geographic ranges expand into regions formerly dominated by peripheral populations of cool-adapted species. Three of the 9 cool-adapted, peripheral populations decreased in abundance whereas 6 species exhibited little change. For warm-adapted populations near the core of their range, 1 of 16 decreased in abundance, 11 increased, and 4 exhibited no change. Within the most abundant species in this community, our results indicate that warm-adapted species are expanding their ranges faster than the rate at which ranges of cool-adapted species are contracting. Avoiding future community turnover may require conservation strategies that maintain microclimates for cool-adapted species facing novel abiotic and biotic conditions at high elevations.

Assessing climatic conditions and biotic interactions shaping the success of Cystoseira foeniculacea early-life stages.

Early-life stages of canopy-forming macroalgae are critical for the maintenance of natural populations and the success of restoration actions. Unfortunately, the abiotic conditions and biotic interactions shaping the success of these stages have received less attention than the interactions shaping the success of adults. Here, we combined field and mesocosm experiments to explore the effects of temperature, herbivory, and canopy presence on the development of early-life stages of the brown seaweed Cystoseira foeniculacea. We assessed these effects by examining changes in recruit density and size. After recruiting zygotes under laboratory conditions, we conducted one laboratory and three field experiments. In the first field experiment, the density of recruits decreased over time in all rockpools and was negatively affected by rising temperatures and turf cover. Additionally, a marine heatwave (MHW; 11 days >25°C) was recorded in the donor pools, producing strong decay in the density of transplanted recruits and a significant reduction of the mature canopy. The second field experiment tested the survival of recruits based on their positioning within the canopy. We observed a higher density of recruits when placed at the edge or outside the canopy compared to recruits placed under the canopy. In the third field experiment, an herbivory-exclusion experiment, we show how density of recruits decreased in less than 48 h in noncaged treatments. In the laboratory, we conducted a thermotolerance experiment under controlled conditions, exposing the recruits to 19, 22, 25, 28, and 31°C for 7 weeks to assess thermal impacts on their survival and growth. Temperatures above the 25°C threshold reduced the density and size of the recruits. This study sheds light on the performance of the early-life stages of a Cystoseira spp. in Macaronesia, showing a low survival ratio against the current pressures even in the context of the potential refuge provided by the intertidal rockpools.

Environmental effects on abundance and size of harvested bivalve populations in intertidal shellfish grounds

Clams, razor clams and cockle are intertidal bivalve species collected on foot in the shellfish grounds of the Rías Altas (NW Spain). Spatio-temporal distribution of these bivalves are typically at the expenses of the environmental conditions of the region; however, the responses to the abiotic conditions are poorly understood. Using data from 6 species (Ruditapes decussatus, Venerupis corrugata, Ruditapes philippinarum, Cerastoderam edule, Donax trunculus and Solen marginatus) sampled in 51 intertidal shellfish grounds during 2007 and 2008, we characterized the influence of the environment (temperature, salinity, nutrient salts, suspended organic matter, or sediment granulometry and composition) on the distribution and size of these species through a comparative statistical analysis. Shellfish grounds were grouped according to their sediment and water characteristics revealing a land-ocean gradient and the influence of the geological imprint that separates bivalve grounds from West to East. Statistical models showed that R. decussatus, V. corrugata and R. philippinarum together with C. edule were more abundant in sites combining a strong marine influence with organic-rich finer sediments. However, each of those species also had different environmental niches mostly related to their particular sediment affinities, the proximity to the river mouth, and their physiological tolerances to temperature and salinity. D. trunculus was only found in outer exposed shellfish grounds, while S. marginatus abundance increased in muddy sediments. River distance was a sound descriptor of individual shell length and length variability with contrasting effects on the different species. Furthermore, slopes of length-weight relationships were steeper in autumn than in spring, and this allometry tended to be more positive in sites located closer to the rivers’ mouth, which had a higher organic matter C/N ratio. Overall, harvested intertidal bivalves had identifiable environmental preferences that influence their spatial distribution in abundance, body size, and allometric growth.