Detecting sediment recovery below an offshore longline mussel farm: A macrobenthic Biological Trait Analysis (BTA)

Expansion of bivalve aquaculture offshore reports lower environmental impacts compared to inshore farms. Taking a Before-After Control-Impact approach, this study presents the first functional diversity analysis and long-term Biological Trait Analysis (BTA) of infauna functional traits following the development of the United Kingdom's first large-scale, offshore longline mussel farm. Located in an area historically impacted by mobile fishing gear, farm sites had the greatest number of taxa and abundance compared to control sites. Functional diversity varied significantly across treatments (farm, near control, far control); while Functional Diversity, Richness, Divergence and Dispersion increased over time within the farm, Functional Evenness and Redundancy decreased. Bioturbation, body size, diet, feeding mode, life span, motility, sediment position, sensitivity and substrate type were chosen for Community-level Weighted Mean analysis, depicting the most frequently affected biological traits by shellfish farming. Farm sites developed a wider range of traits enhancing ecosystem function and habitat recovery after years of seabed damage. Outcomes support the use of functional diversity and BTA analysis to perform ecosystem assessment, supporting decision-makers implement policy and management.

Demographic trade-offs and functional shifts in a hurricane-impacted tropical forest

BACKGROUND AND AIMS

Understanding shifts in the demographic and functional composition of forests after major natural disturbances has become increasingly relevant given the accelerating rates of climate change and elevated frequency of natural disturbances. Although plant demographic strategies are often described across a slow-fast continuum, severe and frequent disturbance events influencing demographic processes may alter the demographic trade-offs and the functional composition of forests. We examined demographic trade-offs and the shifts in functional traits in a hurricane-disturbed forest using long-term data from the Luquillo Forest Dynamics Plot (LFPD) in Puerto Rico.

METHODS

We analysed information on growth, survival, seed rain and seedling recruitment for 30 woody species in the LFDP. In addition, we compiled data on leaf, seed and wood functional traits that capture the main ecological strategies for plants. We used this information to identify the main axes of demographic variation for this forest community and evaluate shifts in community-weighted means for traits from 2000 to 2016.

KEY RESULTS

The previously identified growth-survival trade-off was not observed. Instead, we identified a fecundity-growth trade-off and an axis representing seedling-to-adult survival. Both axes formed dimensions independent of resprouting ability. Also, changes in tree species composition during the post-hurricane period reflected a directional shift from seedling and tree communities dominated by acquisitive towards conservative leaf economics traits and large seed mass. Wood specific gravity, however, did not show significant directional changes over time.

CONCLUSIONS

Our study demonstrates that tree demographic strategies coping with frequent storms and hurricane disturbances deviate from strategies typically observed in undisturbed forests, yet the shifts in functional composition still conform to the expected changes from acquisitive to conservative resource-uptake strategies expected over succession. In the face of increased rates of natural and anthropogenic disturbance in tropical regions, our results anticipate shifts in species demographic trade-offs and different functional dimensions.

Linking ecotoxicological effects on biodiversity and ecosystem functions to impairment of ecosystem services is a challenge: an illustration with the case of plant protection products

There is growing interest in using the ecosystem services framework for environmental risk assessments of chemicals, including plant protection products (PPPs). Although this topic is increasingly discussed in the recent scientific literature, there is still a substantial gap between most ecotoxicological studies and a solid evaluation of potential ecotoxicological consequences on ecosystem services. This was recently highlighted by a collective scientific assessment (CSA) performed by 46 scientific experts who analyzed the international science on the impacts of PPPs on biodiversity, ecosystem functions, and ecosystem services. Here, we first point out the main obstacles to better linking knowledge on the ecotoxicological effects of PPPs on biodiversity and ecological processes with ecosystem functions and services. Then, we go on to propose and discuss possible pathways for related improvements. We describe the main processes governing the relationships between biodiversity, ecological processes, and ecosystem functions in response to effects of PPP, and we define categories of ecosystem functions that could be directly linked with the ecological processes used as functional endpoints in investigations on the ecotoxicology of PPPs. We then explore perceptions on the possible links between these categories of ecosystem functions and ecosystem services among a sub-panel of the scientific experts from various fields of environmental science. We find that these direct and indirect linkages still need clarification. This paper, which reflects the difficulties faced by the multidisciplinary group of researchers involved in the CSA, suggests that the current gap between most ecotoxicological studies and a solid potential evaluation of ecotoxicological consequences on ecosystem services could be partially addressed if concepts and definitions related to ecological processes, ecosystem functions, and ecosystem services were more widely accepted and shared within the ecotoxicology community. Narrowing this gap would help harmonize and extend the science that informs decision-making and policy-making, and ultimately help to better address the trade-off between social benefits and environmental losses caused by the use of PPPs.

Global investigation of lake habitat coupling by fishes

Habitat coupling, where consumers acquire resources from different habitats, plays an important role in ecosystem functioning. In this study, we provide a global investigation of lake habitat coupling by freshwater fishes between littoral (nearshore) and pelagic (open water) zones and elucidate the extent to which magnitude of coupling varies according to environmental context and consumer traits. We consider the influence of lake factors (surface area, depth, shoreline complexity, and annual temperature), relative trophic position of consumers, fish community species richness, and fish morphological traits on habitat coupling by fishes. Using a worldwide dataset consisting of fish stable isotope values (δ¹³C and δ¹⁵N), we developed an index of habitat coupling, and used Bayesian hierarchical and non-hierarchical beta regressions to estimate the effects of environmental lake context and morphological traits on habitat coupling by fishes. Our results show high rates of habitat coupling among fishes globally with marked taxonomic differences in the magnitude and variation. Habitat coupling was higher in lower elevation lakes and in regions characterized by relatively colder climates, whereas other environmental context factors had little or no effects on habitat coupling. Furthermore, habitat coupling was associated with several locomotion and feeding traits, but independent from species maximum body length. Overall, we highlight the prevalence of multiple resources supporting fish populations and suggest future research identify implications to ecosystem functioning that may result from alterations to habitat coupling by fishes.

Functional diversity in an Andean subpáramo affected by wildfire in Colombia

Recently, the Andean subpáramo in Colombia has experienced severe wildfires, but little is known about the functional composition of recovering or not after a wildfire. Therefore, we examined the functional community composition subpáramo affected by fire in 2016. We documented how functional traits changed 31 months after the disturbance and compared them with an unburned site. We sampled from one to two years after the fire every four months, then registered all recruits in 16 5 × 5m plots. New individuals were classified into strategy functional groups based on the traits of persistence and dispersal. The first group was stem type and regeneration mechanism (seedling and resprout), and the second was fruit type and dispersal mode. We investigated the degree to which functional diversity changes plant communities over time (woody and non-woody), and we compared it with an unburned site. The most relevant results showed that resprouts and seed regenerated increased post-fire time and significant differences between sampling periods. The anemochory is the most relevant dispersal mode that indicates the community capacity to colonize the new gaps opened by the fire rapidly. We discuss how wildfire appears to be a triggering factor for persistence and dispersal strategy groups in subpáramo burned given their characteristics of tolerance to stress. For this reason, a greater functional divergence between the ecosystems studied post-fire recovery has been related to higher levels of biodiversity at the landscape scale due to the high degree of endemism and significant differences in species composition between páramos.

Legume effects in a native community invaded by alien Asteraceae in a multi-species comparison

Facilitation has been a long-neglected type of interaction but received more attention recently. Legumes are commonly involved in facilitative interactions due to their nitrogen fixation. Facilitative interactions are so far underappreciated yet potentially important for biological invasions, especially given increasing numbers of alien species. In a common garden experiment using 30 annual Asteraceae species (neophytes, archaeophytes, plus some natives), grown in communities with or without legume presence, we measured functional traits and fitness in focal Asteraceae, as well as nitrogen characteristics of Asteraceae and two native community phytometer species. We investigated how legume presence affects relationships between trait and nitrogen concentration and Asteraceae fitness; and whether mechanisms of facilitation in legume presence and its effects on aboveground performance differ among native phytometer, neophyte, and archaeophyte Asteraceae using the δ¹⁵N natural abundance method. Lower specific leaf area was associated with higher aboveground biomass and seed production, with a stronger effect in legume absence. Nitrogen concentration had a positive relationship with biomass, but did not generally increase seed production. Our results hint at N facilitation for the native grass phytometer Festuca rupicola when growing in legume presence, whereas the forb Potentilla argentea and 27 alien Asteraceae species did not indicate facilitative effects. Intriguingly, direct legume facilitation in native phytometer species was only detected when growing with archaeophytes neighbors, not with neophytes. This hints at varied mechanisms of competition for nitrogen between natives and alien species of different residence time and deepens the understanding of altered facilitative leguminous effects in alien species presence.

Searching for predictors of the variability of impacts caused by non-native trees on regulating ecosystem services worldwide

Humans have introduced non-native trees (NNT) all over the world to take advantage of the plethora of benefits they provide. However, depending on the context, NNT may present a diverse range of effects on ecosystem services (ES), from benefits to drawbacks, which may hinder the development of policies for these species. Unfortunately, the attempts so far to understand the impacts of NNT on ES only explained a low proportion of their variation. Here we analyze the variation in impacts of NNT on regulating ecosystem services (RES) by using a global database, which covers the effect size of multiple NNT species on six RES (climate regulation, soil erosion regulation, soil fertility, soil formation, hydrological cycle regulation, and fire protection). We used a wide range of predictors to account for the context-dependency of impacts distributed in five groups: the RES type, functional traits of both the NNT and the dominant NT of the recipient ecosystem, phylogenetic and functional distances between NNT and NT, climatic context, and human population characteristics. Using boosted regression trees and regression trees, we found that the most influential predictors of NNT impacts on RES were annual mean temperatures and precipitation seasonality, followed by the type of RES, human population density, and NNT height. In regions with warm temperatures and low seasonality, NNT tended to increase RES. NNT impacts were greater in densely populated regions. Smaller NNT exerted greater positive impacts on climate regulation and soil erosion regulation in tropical regions than in other climates. We highlight that benign climates and high population density exacerbate the effects of NNT on RES, and that soil fertility is the most consistently affected RES. Knowledge of the factors that modulate NNT impacts can help to predict their potential effects on RES in different parts of the world and at various environmental settings.

Nitrogen addition and drought affect nitrogen uptake patterns and biomass production of four urban greening tree species in North China

Nitrogen (N) is an essential nutrient element limiting plant growth and production, and plant N uptake capacity varies with environmental change. Recently, global climate changes such as N deposition and drought have important impacts on the terrestrial ecosystems, especially for urban greening trees. However, it's still unclear how N deposition and drought affect plant N uptake and biomass production and the underlying relationship between them. Therefore, we conducted a ¹⁵N isotope labeling experiment on four common tree species of urban green spaces in North China, including Pinus tabulaeformnis, Fraxinus chinensis, Juniperus chinensis, and Rhus typhina in pots. Three N addition treatments (0, 3.5, and 10.5 gN m^-2 year^-1; "no", "low", and "high" N treatments, respectively) and two water addition treatments (300 and 600 mm year^-1; "drought" and "normal water", respectively) were set up in a greenhouse. Our results showed that N and drought significantly affected tree biomass production and N uptake rates, and the relationship between them depended on the species specificity. Trees could transform their N uptake preference to adapt to the changing environment, from ammonium to nitrate or vice versa, which was also reflected in total biomass. Furthermore, the variation of N uptake patterns was also related to distinct functional traits, including aboveground (specific leaf area and leaf dry matter content) or belowground (specific root length, specific root area, and root tissue density) traits. There was a transformation of plant resource acquisitive strategy in a high N and drought environment. In general, there were tight connections among N uptake rates, functional traits, and biomass production of each target species. This finding comes up with a new strategy that tree species can modify their functional traits and plasticity of the N uptake forms for survival and growth in the context of high N deposition and drought.

Long-interval effects of wildfires on the functional diversity of land snails

In fire-prone regions, fire is a major natural disturbance which shapes ecosystem function and community composition. Fire has a direct and dramatic effect on soil fauna and, especially, on non-mobile species such as land snails. The factors that make the Mediterranean Basin a fire-prone region may also lead to the appearance after fires of certain functional traits related to ecological and physiological characteristics. Knowledge of how community structure and function change along the post-fire succession will be useful for understanding the processes that drive biodiversity patterns in burnt areas and for implementing appropriate biodiversity management strategies. Here, we examine long-interval taxonomic and functional changes occurred in a snail community four and 18 years after a fire in the Sant Llorenç del Munt i l'Obac Natural Park (NE Spain). Our field-based study demonstrates that the land snail assemblage responds both taxonomically and functionally to fire and that there was a clear replacement of dominant species from the first to the second sampling period. Variation in community composition between different post-fire ages can be attributed to snail species traits and successional changes in post-fire habitat conditions. At taxonomic level, there was great variation in snail species turnover between both periods, being the development of the understorey vegetation structure the main driver of this variation. The replacement of functional traits between times since fire suggests that xerophilic and mesophilic preferences play an important role after fire and are largely determined by the complexity of post-fire microhabitats. Our analysis indicates that immediately after a fire there is a time-window of opportunity that attracts species specializing in early successional habitats, which thereafter are replaced due to the changing conditions resulting from succession. Consequently, knowing the functional traits of species is important for determining the impacts of disturbances on the taxonomic and functional communities.

Effects of microplastic type on growth and physiology of soil crops: Implications for farmland yield and food quality

Microplastic residues pose one of the most serious environmental problems in areas where plastic mulch is used extensively. Microplastic pollution has potentially serious consequences for ecosystems and human health. Several studies have analyzed microplastics in greenhouses or laboratory climate-controlled chambers; however, field studies evaluating the effects of different microplastics on different crops in extensive farming are limited. Therefore, we selected three major crops, Zea mays (ZM, monocotyledon), Glycine max (GM, dicotyledon, aboveground-bearing), and Arachis hypogaea (AH, dicotyledon, belowground-bearing) and investigated the effect of adding polyester microplastics (PES-MPs) and polypropylene microplastics (PP-MPs). Our results demonstrate that PP-MPs and PES-MPs decreased the soil bulk density of ZM, GM, and AH. Regarding soil pH, PES-MPs increased the soil pH of AH and ZM, whereas PP-MPs decreased the soil pH of ZM, GM, and AH compared to controls. Intriguingly, different coordinated trait responses to PP-MPs and PES-MPs were observed in all crops. In general, commonly measured parameters of AH, such as plant height, culm diameter, total biomass, root biomass, PSII maximum photochemical quantum yield (Fv/Fm), hundred-gain weight, and soluble sugar tended to decrease under PP-MPs exposure; however, some indicators of ZM and GM increased under PP-MPs exposure. PES-MPs had no obviously adverse influence on the three crops, except for the biomass of GM, and even significantly increased the chlorophyll content of AH, specific leaf area, and soluble sugar of GM. Compared with PES-MPs, PP-MPs have serious negative effects on crop growth and quality, especially AH. The findings of the present study provides evidence for evaluating the impact of soil microplastic pollution on crop yield and quality in farmland and lay a foundation for future investigations on the exploration of MP toxicity mechanisms and adaptability of different crops to microplastics.

Marine macroinvertebrate ecosystem services under changing conditions of seagrasses and mangroves

This study aimed to investigate the impact of changing environmental conditions on MMI ES in seagrasses and mangroves. We used data from satellite and biodiversity platforms combined with field data to explore the links between ecosystem pressures (habitat conversion, overexploitation, climate change), conditions (environmental quality, ecosystem attributes), and MMI ES (provisioning, regulation, cultural). Both seagrass and mangrove extents increased significantly since 2016. While sea surface temperature showed no significant annual variation, sea surface partial pressure CO2, height above sea level and pH presented significant changes. Among the environmental quality variables only silicate, PO4 and phytoplankton showed significant annual varying trends. The MMI food provisioning increased significantly, indicating overexploitation that needs urgent attention. MMI regulation and cultural ES did not show significant trends overtime. Our results show that MMI ES are affected by multiple factors and their interactions can be complex and non-linear. We identified key research gaps and suggested future directions for research. We also provided relevant data that can support future ES assessments.

Invasive Cirsium arvense displays different resource-use strategies along local habitat heterogeneity in the trans-Himalayan region of Ladakh

Climate change and anthropogenic pressures have resulted in a significant shift in the invasion susceptibility and frequency of non-native species in mountain ecosystems. Cirsium arvense (L.) Scop. (Family: Asteraceae) is an invasive species that spreads quickly in mountains, especially in the trans-Himalayan region of Ladakh. The current study used a trait-based approach to evaluate the impact of local habitat heterogeneity (soil physico-chemical properties) on C. arvense. Thirteen plant functional traits (root, shoot, leaf, and reproductive traits) of C. arvense were studied in three different habitat types (agricultural, marshy, and roadside). Functional trait variability in C. arvense was higher between, than within habitats (between different populations). All the functional traits interacted with habitat change, except for leaf count and seed mass. Soil properties strongly affect C. arvense's resource-use strategies across habitats. The plant adapted to a resource-poor environment (roadside habitat) by conserving resources and to a resource-rich environment (agricultural and marshy land habitat) by acquiring them. The ability of C. arvense to use resources differently reflects its persistence in introduced habitats. In summary, our study shows that C. arvense invades different habitats in introduced regions through trait adaptations and resource-use strategies in the trans-Himalayan region.

Why phylogenetic signal of traits is important in ecosystems: uniformity of a plant trait increases soil fauna, but only in a phylogenetically uniform vegetation

Phylogenetically closely related plant species often share similar trait states (phylogenetic signal), but local assembly may favor dissimilar relatives and thereby decouple the diversity of a trait from the diversity of phylogenetic lineages. Associated fauna might either benefit from plant trait diversity, because it provides them complementary resources, or suffer from it due to dilution of preferred resources. We hence hypothesize that decoupling of trait and phylogenetic diversity weakens the relationship between the plant-trait diversity and the abundance and diversity of associated fauna. Studying permanent meadows, we tested for combined effects of plant phylogenetic diversity and diversity of two functional traits (specific leaf area, leaf dry matter content) on major groups of soil fauna (earthworms, mites, springtails, nematodes). We found that only in phylogenetically uniform plant communities, was uniformity in the functional traits associated with (i) high abundance in springtails, and (ii) high abundance of the sub-group that feeds more directly on plant material (in springtails and mites) or those that are more prone to disturbance (in nematodes), and (iii) high diversity in all three groups tested (springtails, earthworms, nematodes). Our results suggest that soil fauna profits from the resource concentration in local plant communities that are uniform in both functional traits and phylogenetic lineages. Soil fauna would hence benefit from co-occurrence of closely related plants that have conserved the same trait values, rather than of distantly related plants that have converged in traits. This might result in faster decomposition and a positive feedback between trait conservatism and ecosystem functioning.

Within leaf nitrogen allocation regulates the photosynthetic behavior of xerophytes in response to increased soil rock fragment content

There is limited information on how plant functional traits vary with soil rock fragment content (RFC), especially for xerophytes growing in stony soils. We examined leaf functional traits of three xerophytes (Sophora davidii; Cotinus szechuanensi; and Artemisia vestita) grown under an RFC gradient in a heavy loamy soil. Our results show that photosynthetic capacity increased linearly with RFC in S. davidii, whereas unimodal patterns were observed for the other two species. The RFC that maximized photosynthetic capacity (A_sat) and photosynthetic N use efficiency (PNUE) were achieved by allocating more N to photosynthetic apparatus at the expense of cell walls. For C. szechuanensis, the increased fraction of photosynthetic N allocated to carboxylation (P_C) bioenergetics (P_B), and thylakoid light-harvesting components (P_L) together contributed to the higher A_sat and PNUE values. As for S. davidii, both P_C and P_B mainly contributed to higher A_sat and PNUE, whereas for A. vestita only P_B was the main contributor. Our results suggest that increased non-capillary porosity of high RFC soil conditions through promoting the root growth of S. davidii and C. szechuanensis ensures sufficient water and N supply for photosynthetic capacity. In shallow-rooted species A. vestita, low RFC soil maintained higher nitrate N in the topsoil, enhancing leaf photosynthetic capacity. We conclude that rock fragments promoted leaf photosynthetic capacity in the studied loamy soil system, but the promoting effect was species-specific. The results highlight the relevance of consideration of soil rock fraction in evaluation of photosynthetic behavior of xerophytes in heterogeneous rocky soils.

Environmental heterogeneity of a tropical river-to-sea continuum and its relationship with structure and phytoplankton dynamics - Lençóis Maranhenses National Park

β-diversity and functional traits of phytoplankton indicators associated with environmental heterogeneity were investigated as environmental quality descriptors in coastal (CS), estuarine (ES), and limnetic (LS) sectors in a tropical river-to-sea ecosystem. Results showed that environmental heterogeneity was marked by spatial differences, contributing to biological heterogeneity. Sporadic and recurrent blooms were associated with environmental spatiotemporal variations and reflected a reduction in ES α-diversity. Salinity acted as an environmental filter that governed the structure and dynamics of the community. The spatial heterogeneity and high turnover of phytoplankton resulted in reliable bioindicators selection. Colonial, bloom-forming and harmful species were associated with highly suspended particulate matter (SPM) because these species are better adapted to these conditions. Species small in size were associated with high concentrations of silicate and chlorophyll-a in the ES because of the occurrence of diatom recurrent blooms. Most flagellates indicators genera have bloom-forming potential. Integrating morphofunctional with taxonomic approaches enabled detailed observations of environmental filters, supporting the selection of priority species and areas for introducing biodiversity monitoring programs and conservation in tropical ecosystems.

Bioassessment of environmental quality based on taxonomic and functional traits of marine nematodes in the Bohai Sea, China

Free-living marine nematodes are valuable biological indicators for different environmental disturbances. Their taxonomic composition and functional traits often respond to environmental changes. In this study, marine nematodes, collected from the Bohai sea on the northeastern coast of China in 2014, were investigated in terms of their taxonomic composition and functional traits. Furthermore, the environmental quality of the investigated area was assessed based on nematode metrics. The studied nematode community showed spatial variation in taxonomic and functional composition, in response to changes in environmental variables such as sediment chlorophyll-a, phaeophytin-a, organic matter content, silt-clay content etc. Overall, high percentage of tolerant marine nematodes species or colonizers predominated, suggesting a disturbed environmental condition of the study area. Further results from the environmental quality assessment based on nematode metrics indicated a moderate quality status at the most investigated stations.

Water exchange unevenness alters the species dominance and community composition of submerged macrophytes in Erhai Lake and the potential mechanisms revealed by laboratory experiment

Water exchange unevenness (WEU) is defined as the coefficient of variation in water exchange intensity over time. Although its influence on aquatic plant characteristics has been recently investigated, there is limited understanding regarding the effects of this hydrodynamic change on submerged vegetation. This study investigated the impacts of WEU on the species dominance and community composition of submerged macrophytes in three bays with different WEU conditions in Erhai Lake, China. Subsequently, a laboratory experiment was conducted to elucidate the mechanisms underlying these effects. The field investigation showed that the dominance values of submerged macrophytes were influenced by WEU. As WEU decreased, the average dominance value decreased for Vallisneria natans (by 34.54 %), Myriophyllum spicatum (16.82 %), and Hydrilla verticillata (12.84 %); showed no significant change for Potamogeton lucens; and increased for Potamogeton maackianus (14.22 %) and Ceratophyllum demersum (17.52 %). The laboratory experiment showed that lower WEU markedly inhibited the growth of V. natans, slightly inhibited that of M. spicatum, and stimulated that of P. maackianus, consistent with the field observations. The inhibitory effect was attributed to a reduced concentration of carbon dioxide in the water; adaptive strategies, i.e., plant height, biomass allocation, and root traits, were more effective for M. spicatum than for V. natans. The stimulated growth of P. maackianus was attributed to increased dissolved oxygen concentration, which promoted root growth and nutrient uptake. Our results indicate that WEU has significant effects on the growth and community characteristics of submerged macrophytes.

Macroecotoxicological approaches to emerging patterns of microplastic bioaccumulation in crabs from estuarine and marine environments

Despite the increasing plastic discharge into the environment, few articles have dealt with the macroecological implications of microplastics (MPs) bioaccumulation on organisms. We performed a meta-analysis of MPs accumulation in true crabs and pseudocrabs worldwide and made use of macroecotoxicological approaches to know if: I) functional traits influence the bioaccumulation of MPs in the tissues of crabs; II) there is a latitudinal pattern of MPs bioaccumulation; III) there are tissues that can accumulate more MPs; IV) crabs can sort particles according to size, color, shape and type. Our results showed that functional traits influence the accumulation of MPs. Smaller crabs in size and weight and with shorter lifespans tended to exhibit more plastic particles. According to the environment, estuarine crabs from the intertidal and muddy substrates held more MPs. Also, burrowers exhibited significantly more particles in the tissues than omnivorous crabs. Besides, we recorded that crabs from low latitudes tended to exhibit more plastic particles, probably because of the mangroves' location that acts as traps for MPs. Non-human-consumed crabs accumulated significantly more MPs than human-consumed ones. Considering the tissues, gills were prone to accumulate more debris than the digestive tract, but without significant differences. Finally, colorless fibers of 1-5 mm of PA, PP and PET were the predominant characteristics of MPs, suggesting that crabs accumulated denser types but did not sort plastic according to color. These results indicate that functional traits might influence the accumulation of MPs and that there are coastal regions and geographical areas where crabs tend to accumulate more MPs. Analyzing MPs accumulation patterns with macroecological tools can generate information to identify the most affected species and define priorities for monitoring and implementing actions toward reducing plastic use globally.

Biology, farming and applications of economically important red seaweed Gracilaria edulis (S. G. Gmelin) P. C. Silva: A concise review

Gracilaria edulis is one of the most studied agarophytes, especially in tropical regions like India because of its natural abundance. Apart from the Indian peninsula, it is widely distributed in tropical and subtropical regions. The taxonomy of G. edulis is evolving; currently G. edulis is the taxonomically accepted name, however several phylogenetic and morphological investigations supported its inclusion in the genus Hydropuntia. In addition to the conventional farming methods like the tube net and raft methods which use clonally propagated seed material, spore-based planting materials like carpospores have been employed to cultivate G. edulis. Co-cultivation with shrimp farm wastewater has also been practised to make the cultivation economically viable and environmentally sustainable as the seaweed could provide an efficient ecosystem service by up taking nitrogen from the shrimp waste. Like other seaweed cultivation systems, farming of G. edulis is also infested by various epiphytes like Ulva, Cladophora, Ceramium, Centroceras, Hypnea and Padina as well as grazed by fishes like Monodactylus, Pelates and Pteroscirtes which decrease the growth and ultimately result in low yield of agar, seaweed sap and other value added products. Food grade agar produced by this seaweed is an important resource and the current review focusses on the latest extraction technologies. Further, there also is evidence based application of plant bio-stimulant derived from G. edulis feedstock which has proven to be highly effective in enhancing the yield by 10-33% in field trials of nine cash crops.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10811-023-02955-8.

Trait-mediated leaf retention of atmospheric particulate matter in fourteen tree species in southern China

Particulate air pollution is a serious threat to human health, especially in urban areas, and trees can act as biological filters and improve air quality. However, studies on greening tree species selection are rare. We measured three particular matter adsorption metrics (PM_2.5, PM_2.5-10, and PM_>10 captured per leaf area) and six functional traits for each of fourteen species and estimated their minimum light requirements based on field surveys. We found that shade-tolerant species captured more coarse particles (PM_2.5-10) than light-demanding species. For traits, a strong negative correlation was found between photosynthetic capacity and adsorption capacity for all three PM size fractions, indicating that in comparison to acquisitive species, conservative species captured larger amounts of particles. Moreover, denser wood species and smaller leaves were more efficient in capturing large particles (PM_>10), while species with "expensive" leaves (high leaf N or P) were more efficient in capturing fine particles (PM_2.5), indicating that capturing large and fine particles was related to mechanical stability traits and leaf surface traits, respectively. Our results demonstrated that the metabolism (e.g., photosynthetic capacity) and chemistry (e.g., leaf N and leaf P) of leaves help explain species capacity to capture PM. We encourage future studies to investigate the ecosystem functions and stress tolerance of tree species with the same framework and trait-based methods.

Fauna access outweighs litter mixture effect during leaf litter decomposition

Decomposition rates of litter mixtures reflect the combined effects of litter species diversity, litter quality, decomposers, their interactions with each other and with the environment. The outcomes of those interactions remain ambiguous and past studies have reported conflicting results (e.g., litter mixture richness effects). To date, how litter diversity and soil fauna interactions shape litter mixture decomposition remains poorly understood. Through a sixteen month long common garden litter decomposition experiment, we tested these interaction effects using litterbags of three mesh sizes (micromesh, mesomesh, and macromesh) to disentangle the contributions of different fauna groups categorized by their size at Wuhan botanical garden (subtropical climate). We examined the decomposition of five single commonly available species litters and their full 26 mixtures combination spanning from 2 to 5 species. In total, 2325 litterbags were incubated at the setup of the experiment and partly harvested after 1, 3, 6, 9, and 16 months after exposure to evaluate the mass loss and the combined effects of soil fauna and litter diversity. We predicted that litter mixture effects should increase with increased litter quality dissimilarity, and soil fauna should enhance litter (both single species litter and litter mixtures) decomposition rate. Litter mass loss ranged from 26.9 % to 87.3 %. Soil fauna access to litterbags accelerated mass loss by 29.8 % on average. The contribution of soil mesofauna did not differ from that of soil meso- and macrofauna. Incubation duration and its interactions with litter quality dissimilarities together with soil fauna determined the litter mixture effect. Furthermore, the litter mixture effect weakened as the decomposition progresses. Faunal contribution was broadly additive to the positive mixture effect irrespective of litter species richness or litter dissimilarity. This implies that combining the dissimilarity of mixture species and contributions of different soil fauna provides a more comprehensive understanding of mixed litter decomposition.

Drought- and soil substrate-induced variations in root nonstructural carbohydrates result from fine root morphological and anatomical traits of Juglans mandshurica seedlings

BACKGROUND

Nonstructural carbohydrates (NSCs) reflect the carbon supply status and affect the construction and development of plants. Previous studies have focused on the dynamics of NSCs among plant organs, however, few studies have paid attention to the synergistic variations between fine root traits and NSCs under drought based on the perspective of branch order roots. This study aims to explore the responses of fine root traits and NSCs among root orders of Juglans mandshurica seedlings under different drought intensities and soil substrates. The 2-year-old J. mandshurica potted seedlings were planted in three different soil substrates (humus, loam and sandy-loam soil) and subjected to four drought intensities (CK, mild drought T1, moderate drought T2 and severe drought T3) for 60 days.

RESULTS

The root biomass of seedlings in sandy-loam soil under the same drought intensity was higher than that of seedlings in humus soil. With an increase in drought, the root biomass, average diameter, root tissue density and cortex thickness decreased significantly, and the specific root length, stele diameter and conduit density increased. The root NSC contents in humus soil were higher than those in sandy-loam soil. The fine root soluble sugar content in all soil substrates decreased with increasing drought intensity, while the root starch and total NSC contents varied among the different soil substrates. Compared with transportive roots, the morphological and anatomical traits jointly explained the higher variation in NSC contents of the absorptive roots. The anatomical traits explained the higher variation in the NSC content of first five order roots.

CONCLUSION

Our results suggest that coordinated adaptation of the root traits and NSCs of Manchurian walnut seedlings exposed to water gradients in different soil substrates.

Can functional units of periphytic protozoan communities be used to evaluate the effects of harmful algal blooms on ecological quality in marine ecosystems?

Based on biological traits, the ecological quality status under the pressure of two harmful algal bloom (HAB) species was evaluated using functional units (FUs) of periphytic protozoan communities. Five treatments with different concentrations of Alexandrium tamarense and Gymnodinium catenatum, i.e., 100, 102, 103, 104, and 105 cells ml-1, were used. A total of 20 FUs were identified from 25 test protozoan species. Among these FUs, vagile algivores with large sizes showed a decreasing trend (i.e., in diversity and abundance) with increasing concentrations of algae, while vagile bacterivores and non-selectives with small sizes dominated at concentrations of 104 cells ml-1 of both algal species. Ellipse tests on pair-wise functional distinctness indices revealed a significant departure of test protozoan communities from an expected functional distinctness breadth when algal concentrations exceeded 104 cells ml-1. Based on these findings, it was concluded that FUs of periphytic protozoa may be a useful tool for evaluating the effects of HABs on ecological quality status in marine ecosystems.

Light-acquisition traits link aboveground biomass and environment in inner saline-alkaline herbaceous marshes

A functional response-effect approach could predict how environmental changes affect ecosystem functioning. However, few studies have applied this approach to inner saline-alkaline marsh ecosystems where soil saline-alkaline, flooding/drought and nutrients stresses threat ecological functioning. To disentangle the relationships between environmental conditions and ecosystem functioning, a total of 81 plots were investigated across 22 marsh sites dominated by Phragmites australis and Bolboschoenus planiculmis in Western Songnen Plain wetlands, China. For both plant communities combined, deep flooding supported communities with higher specific leaf area (SLA), plant height and leaf nitrogen (N) content but lower leaf thickness. On the contrary, high soil salt content induced low leaf N and phosphorus (P) content, SLA and plant height. Only light acquisition-related trait, plant height and SLA, was the key traits which determined the relationships between ecosystem functioning (aboveground biomass) and saline-alkaline wetland environment. Yet indirect key traits related nutrient and water acquisition such as leaf thickness, N and P content were also found, and mediated the response of aboveground biomass through the allometric relationships with plant height or SLA. For the individual species community, only plant height was the key trait shared by P. australis and B. planiculmis, indicating the universality of plant height as a key trait for grass and sedge plants to explain how ecosystem functioning responds to abiotic factors. Hence, our findings suggest that saltmarsh plants are more inclined to alter light-acquisition traits to mediate the response of ecosystem functioning to environmental changes and that plant height is a particularly useful trait to predict plant productivity in earth system models under future environmental changes in inner saline-alkaline wetlands.

Complexity vs linearity: relations between functional traits in a heterotrophic protist

BACKGROUND

Functional traits are phenotypic traits that affect an organism's performance and shape ecosystem-level processes. The main challenge when using functional traits to quantify biodiversity is to choose which ones to measure since effort and money are limited. As one way of dealing with this, Hodgson et al. (Oikos 85:282, 1999) introduced the idea of two types of traits, with soft traits that are easy and quick to quantify, and hard traits that are directly linked to ecosystem functioning but difficult to measure. If a link exists between the two types of traits, then one could use soft traits as a proxy for hard traits for a quick but meaningful assessment of biodiversity. However, this framework is based on two assumptions: (1) hard and soft traits must be tightly connected to allow reliable prediction of one using the other; (2) the relationship between traits must be monotonic and linear to be detected by the most common statistical techniques (e.g. linear model, PCA).

RESULTS

Here we addressed those two assumptions by focusing on six functional traits of the protist species Tetrahymena thermophila, which vary both in their measurement difficulty and functional meaningfulness. They were classified as: easy traits (morphological traits), intermediate traits (movement traits) and hard traits (oxygen consumption and population growth rate). We detected a high number (> 60%) of non-linear relations between the traits, which can explain the low number of significant relations found using linear models and PCA analysis. Overall, these analyses did not detect any relationship strong enough to predict one trait using another, but that does not imply there are none.

CONCLUSIONS

Our results highlighted the need to critically assess the relations among the functional traits used as proxies and those functional traits which they aim to reflect. A thorough assessment of whether such relations exist across species and communities is a necessary next step to evaluate whether it is possible to take a shortcut in quantifying functional diversity by collecting the data on easily measurable traits.