Future Environmental Change Research Articles

Persistent Clones and Local Seed Recruitment Contribute to the Resilience of Enhalus acoroides Populations Under Disturbance

Human-induced land use in coastal areas is one of the main threats for seagrass meadows globally causing eutrophication and sedimentation. These environmental stressors induce sudden ecosystem shifts toward new alternative stable states defined by lower seagrass richness and abundance. Enhalus acoroides, a large-sized tropical seagrass species, appears to be more resistant toward environmental change compared to coexisting seagrass species. We hypothesize that reproductive strategy and the extent of seedling recruitment of E. acoroides are altered under disturbance and contribute to the persistence and resilience of E. acoroides meadows. In this research, we studied eight populations of E. acoroides in four lagoons along the South Central Coast of Vietnam using 11 polymorphic microsatellite loci. We classified land use in 6 classes based on Sentinel-2 L2A images and determined the effect of human-induced land use at different spatial scales on clonal richness and structure, fine-scale genetic structure and genetic diversity. No evidence of population size reductions due to disturbance was found, however, lagoons were strongly differentiated and may act as barriers to gene flow. The proportion and size of clones were significantly higher in populations of surrounding catchments with larger areas of agriculture, urbanization and aquaculture. We postulate that large resistant genets contribute to the resilience of E. acoroides meadows under high levels of disturbance. Although the importance of clonal growth increases with disturbance, sexual reproduction and the subsequent recruitment of seedlings remains an essential strategy for the persistence of populations of E. acoroides and should be prioritized in conservation measures to ensure broad-scale and long-term resilience toward future environmental change.

Determinants of trophic cascade strength in freshwater ecosystems: a global analysis.

Top-down cascade effects are among the most important mechanisms underlying community structure and abundance dynamics in aquatic and terrestrial ecosystems worldwide. A current challenge is understanding the factors controlling trophic cascade strength under global environmental changes. Here, we synthesized 161 global sites to analyze how multiple factors influence consumer-resource interactions with fish in freshwater ecosystems. Fish have a profound negative effect on zooplankton and water clarity but positive effects on primary producers and water nutrients. Furthermore, fish trophic levels can modify the strength of trophic cascades, but an even number of food chain length does not have a negative effect on primary producers in real ecosystems. Eutrophication, warming, and predator abundance strengthen the trophic cascade effects on phytoplankton, suggesting that top-down control will be increasingly important under future global environmental changes. We found no influence or even an increasing trophic cascade strength (e.g., phytoplankton) with increasing latitude, which does not support the widespread view that the trophic cascade strength increases closer to the equator. With increasing temporal and spatial scales, the experimental duration has an accumulative effect, whereas the experimental size is not associated with the trophic cascade strength. Taken together, eutrophication, warming, temporal scale, and predator trophic level and abundance are pivotal to understanding the impacts of multiple environmental factors on the trophic cascade strength. Future studies should stress the possible synergistic effect of multiple factors on the food web structure and dynamics.

Marine mammal biodiversity and rare narwhal (Monodon monoceros) observations near northern Ellesmere Island, Canada

AbstractA climate‐driven decline of sea ice has increased international interest in understanding the ecology of seldom studied high‐Arctic regions projected to retain the last remnants of summer sea ice. Arctic marine mammals are vulnerable to future environmental change due to their high dependence on sea ice. We completed aerial surveys in August 2019 to document the occurrence and location of marine mammals within the recently designated Tuvaijuittuq Marine Protected Area which acts as a last refuge for ice‐associated species. We present photographic evidence of narwhals (Monodon monoceros), Atlantic walruses (Odobenus rosmarus), bearded seals (Erignathus barbatus), and ringed seals (Pusa hispida) in Archer Fjord, northern Ellesmere Island, Nunavut, Canada (81°14′–81°49′ N). We discuss these observations in the context of historical records and more recent opportunistic sightings from the region to support the hypothesis of an expansion north of the currently accepted range of narwhal. The diversity and number of observations of marine mammals in Archer Fjord is a striking contrast to the relative scarcity of the rest of the surveyed region, with very few observations of ringed seals throughout the more northerly study area. Our observations highlight opportunities to further explore high‐latitude areas that may host unique marine mammal biodiversity in the region, including narwhal.

Seasonality, niche management and vertical migration in landscapes of relief

Landscapes of vertical relief, such as mountains and continental slopes, intensify ecological and climatological variation within narrow spatial windows. Seasonal vertical migrants exploit this variation during their residence in, and movements between, vertically stratified seasonal ranges. Animals in terrestrial, marine and even human‐ecological systems undergo similar patterns of seasonal vertical movements. The diversity of arenas in which vertical migration evolved lends insight to the factors promoting seasonal use of landscapes of relief. Because animals must contend with both endogenous circannual rhythms and exogenous environmental seasonality, vertical migrants may be sensitive to inconsistent change across stratified seasonal ranges under climate change. To better understand how ongoing and future climatic and environmental changes are likely to impact vertical migrants, we examine vertical migration in the context of niche tracking and niche switching. Whereas niche trackers minimize variation in realized environmental conditions throughout their seasonal movements, niche switchers undergo seasonal transitions in realized niche space. These strategies mediate the relationship between migrants and their changing environment, and can be used to forecast impacts of future change and effectively conserve systems of vertical migration. Niche tracking may be hindered by inconsistent or unpredictable environmental change along a single niche axis across strata, while niche switching may be sensitive to incongruous spatiotemporal change across factors. We suggest that climate change will affect seasonal patterns in vertical environments discontinuously across time, space and strata, and that vertical migrants are likely to face additional anthropogenic threats that interact with environmental seasonality. Conservation of vertical migrants should prioritize the availability of, and facilitate movement between, stratified seasonal ranges.

Conservation genomics of a critically endangered brown seaweed.

Seaweeds provide valuable ecosystem services, but many are undergoing global decline due to climate and anthropogenic stressors. The brown macroalga, Nereia lophocladia (hereafter called Nereia), is among only a handful of seaweeds globally to be listed as critically endangered and is only described from two known locations, but there exists little knowledge about this species. Here, we combine field surveys to verify the distribution of Nereia, with cutting-edge genomics to determine genetic diversity and population structure, and inform ongoing conservation actions. We expand Nereia's known distribution from one to seven locations along a 70-km long coastal stretch in New South Wales but reveal small population sizes at some sites (as few as 8 individuals despite extensive searching). A total of 1,261 genome-wide SNPs were retained from 70 individuals after filtering, and 304 outlier loci under putative selection were detected by one of three methods. Populations showed low genetic diversity (mean expected heterozygosity HE =0.055±0.014) and high levels of inbreeding within populations (mean FIS =0.721±0.085), along with high genetic differentiation among sites (mean FST =0.276), which may increase susceptibility to future environmental change and decrease the species' ability to recover after loss. Given these findings, we recommend the consideration of both insitu and ex situ conservation measures for Nereia, as well as further research into the species' ecology and biology. Nereia remains of conservation concern and its listing as critically endangered is justified until further investigation elucidates the full distribution and adaptive capacity of the species.

Marginal populations show physiological adaptations and resilience to future climatic changes across a North Atlantic distribution

Rising levels of anthropogenic carbon dioxide (CO2) in the atmosphere over the past several decades has resulted in a changing climate and is projected to further fuel global climate change in future centuries. Key components of climate change in the ocean are ocean acidification (decreasing pH and carbonate ion concentration [CO32-]) and rising sea surface temperatures. While several studies have investigated the effect of these climatic changes on a single population, very few studies have addressed effects on populations living at the margins of their species distribution and the full distributional range. This gap in knowledge impedes the determination of detailed predictions for most species’ futures. Over the course of four months, we investigated physiological changes (primary production, respiration, calcification and growth rates) of 6 populations of the intertidal ecosystem engineer and articulated coralline alga Corallina officinalis to future climatic conditions (low pH (∼7.8); T+3 °C; as well as the combination of low pH and T+3 °C). The populations (n = 2 per geographical location) represent the northern (Iceland) and southern (Spain) margins, as well as the centre (England) of the species distribution in the NE Atlantic. Here, we show that southern and central populations are already living closer to their thermal and stress limits, while Northern populations appear to be the most resilient to environmental changes. We present data confirming light calcification to be the most valuable physiological process which is prioritized in populations throughout the geographical gradient in the NE Atlantic. We found elevated temperature to have a greater effect on populations than pCO2. Investigating and monitoring organism physiology and structure under these extreme environmental conditions provides important information to predict their acclimatisation and resilience to future environmental conditions and potential changes in their distribution.

Effects of nitrogen addition on rhizospheric soil microbial communities of poplar plantations at different ages

The continuous increase of nitrogen (N) deposition has had strong impacts on the structure and health of forest ecosystems globally. An elucidation of the shifts in rhizospheric microbial communities and their interactions with environmental factors under N-addition will assist us with better understanding the responses of forest ecosystems to future environmental changes. In this study, we employed high-throughput sequencing to investigate the responses of rhizosphere soil bacterial and fungal communities to seven-years of N-addition in young (9-year) and mature (14-year) poplar plantations in coastal Eastern China. The experiment included three N-addition levels: 0 (N0), 100 (N1), and 300 (N2) kg N ha−1 yr−1. The results revealed that soil fungal, but not bacterial, alpha-diversity significantly declined under the seven-year N-addition in mature poplars. Moreover, both bacterial and fungal community structures were significantly altered. The total C and NO3− contents controlled the patterns of soil bacteria community structures in mature poplar plantations, while soil pH, NO3−, total N, and C/N were the main factors that shaped the patterns of soil fungi communities in both poplar plantations. However, the relative abundance of plant pathogenic genera Mycoleptodiscus and Plectosphaerella increased strongly with N-addition. The soil microbial communities of mature poplar plantations were sensitive to N-addition. Our findings suggested that long-term simulated N deposition reduced fungal alpha-diversity, altered the composition of bacterial and fungal communities, while boosting the abundance of pathogenic communities, which may induce disease and otherwise damage forest ecosystems.

Wildfire severity and vegetation recovery drive post‐fire evapotranspiration in a southwestern pine‐oak forest, Arizona, USA

AbstractPost‐fire stand water balance is a critical factor influencing tree regeneration and survival, which are often modulated by fire severity. We examined influences of the post‐fire vegetation matrix and fire severity on diurnal, seasonal, and multi‐year variation in evapotranspiration (ET) by analyzing the relationship between post‐fire vegetation and ECOsystem Spaceborne Thermal Radiometer Experiment on the International Space Station (ECOSTRESS) ET data using multivariate and linear mixed effects modeling. Unlike many high‐severity fire sites where ET drops after burning, post‐fire ET was high at shrubland sites that burned at high fire severity in southern Arizona, USA. In this study, post‐fire ET was driven by plant species composition and tree canopy cover. ET was significantly higher in the morning and midday in densely vegetated post‐fire shrublands than pine‐dominated forests that remained 5–7 years after wildfire. Our results demonstrate that plant functional traits such as resprouting and desiccation tolerance drive post‐fire ET patterns, and they are likely to continue to play critical roles in shaping post‐fire plant communities and forest water cycling under future environmental change.

The Latent Dirichlet Allocation model with covariates (LDAcov): A case study on the effect of fire on species composition in Amazonian forests.

Understanding and predicting the effect of global change phenomena on biodiversity is challenging given that biodiversity data are highly multivariate, containing information from tens to hundreds of species in any given location and time. The Latent Dirichlet Allocation (LDA) model has been recently proposed to decompose biodiversity data into latent communities. While LDA is a very useful exploratory tool and overcomes several limitations of earlier methods, it has limited inferential and predictive skill given that covariates cannot be included in the model. We introduce a modified LDA model (called LDAcov) which allows the incorporation of covariates, enabling inference on the drivers of change of latent communities, spatial interpolation of results, and prediction based on future environmental change scenarios. We show with simulated data that our approach to fitting LDAcov is able to estimate well the number of groups and all model parameters. We illustrate LDAcov using data from two experimental studies on the long‐term effects of fire on southeastern Amazonian forests in Brazil. Our results reveal that repeated fires can have a strong impact on plant assemblages, particularly if fuel is allowed to build up between consecutive fires. The effect of fire is exacerbated as distance to the edge of the forest decreases, with small‐sized species and species with thin bark being impacted the most. These results highlight the compounding impacts of multiple fire events and fragmentation, a scenario commonly found across the southern edge of Amazon. We believe that LDAcov will be of wide interest to scientists studying the effect of global change phenomena on biodiversity using high‐dimensional datasets. Thus, we developed the R package LDAcov to enable the straightforward use of this model.

Adaptive differentiation and rapid evolution of a soil bacterium along a climate gradient.

Microbial community responses to environmental change are largely associated with ecological processes; however, the potential for microbes to rapidly evolve and adapt remains relatively unexplored in natural environments. To assess how ecological and evolutionary processes simultaneously alter the genetic diversity of a microbiome, we conducted two concurrent experiments in the leaf litter layer of soil over 18 mo across a climate gradient in Southern California. In the first experiment, we reciprocally transplanted microbial communities from five sites to test whether ecological shifts in ecotypes of the abundant bacterium, Curtobacterium, corresponded to past adaptive differentiation. In the transplanted communities, ecotypes converged toward that of the native communities growing on a common litter substrate. Moreover, these shifts were correlated with community-weighted mean trait values of the Curtobacterium ecotypes, indicating that some of the trait variation among ecotypes could be explained by local adaptation to climate conditions. In the second experiment, we transplanted an isogenic Curtobacterium strain and tracked genomic mutations associated with the sites across the same climate gradient. Using a combination of genomic and metagenomic approaches, we identified a variety of nonrandom, parallel mutations associated with transplantation, including mutations in genes related to nutrient acquisition, stress response, and exopolysaccharide production. Together, the field experiments demonstrate how both demographic shifts of previously adapted ecotypes and contemporary evolution can alter the diversity of a soil microbiome on the same timescale.

Quantifying the effects of land use and model scale on water partitioning and water ages using tracer-aided ecohydrological models

Abstract. Quantifying how vegetation mediates water partitioning at different spatial and temporal scales in complex, managed catchments is fundamental for long-term sustainable land and water management. Estimations from ecohydrological models conceptualising how vegetation regulates the interrelationships between evapotranspiration losses, catchment water storage dynamics, and recharge and runoff fluxes are needed to assess water availability for a range of ecosystem services and evaluate how these might change under increasing extreme events, such as droughts. Currently, the feedback mechanisms between water and mosaics of different vegetation and land cover are not well understood across spatial scales, and the effects of different scales on the skill of ecohydrological models needs to be clarified. We used the tracer-aided ecohydrological model EcH2O-iso in an intensively monitored 66 km2 mixed land use catchment in northeastern Germany to quantify water flux–storage–age interactions at four model grid resolutions (250, 500, 750, and 1000 m). This used a fusion of field (including precipitation, soil water, groundwater, and stream isotopes) and remote sensing data in the calibration. Multicriteria calibration across the catchment at each resolution revealed some differences in the estimation of fluxes, storages, and water ages. In general, model sensitivity decreased and uncertainty increased with coarser model resolutions. Larger grids were unable to replicate observed streamflow and distributed isotope dynamics in the way smaller pixels could. However, using isotope data in the calibration still helped constrain the estimation of fluxes, storage, and water ages at coarser resolutions. Despite using the same data and parameterisation for calibration at different grid resolutions, the modelled proportion of fluxes differed slightly at each resolution, with coarse models simulating higher evapotranspiration, lower relative transpiration, increased overland flow, and slower groundwater movement. Although the coarser resolutions also revealed higher uncertainty and lower overall model performance, the overall results were broadly similar. The study shows that tracers provide effective calibration constraints on larger resolution ecohydrological modelling and help us understand the influence of grid resolution on the simulation of vegetation–soil interactions. This is essential in interpreting associated uncertainty in estimating land use influence on large-scale “blue” (ground and surface water) and “green” (vegetation and evaporated water) fluxes, particularly for future environmental change.

Towards an Arctic Sustainability Monitoring Framework

It is becoming more evident that in the twenty-first century we are living in the new era of Anthropocene, where humans attained the ability to alter planetary processes, bringing new urgency to the systematic understanding of current and future social and environmental changes [...]

Constraints on the source of reactive phases in sediment from a major Arctic river using neodymium isotopes

Riverine suspended particulate matter (SPM) is essential for the delivery of micronutrients such as iron (Fe) to the oceans. SPM is known to consist of multiple phases with differing reactivity, but their role in the delivery of elements to the oceans is poorly constrained. Here we provide new constraints on the source and composition of reactive phases in SPM from the Mackenzie River, the largest sediment source to the Arctic Ocean. Sequential leaching of SPM shows that river sediments contain labile Fe phases. We estimate the labile Fe flux is substantial (0.21(+0.06,−0.05) Tg/yr) by quantifying Fe concentrations in weak leaches of the SPM. The labile Fe phase hosts a considerable amount of rare earth elements (REE), including neodymium (Nd). We demonstrate that the labile Fe phase and dissolved load have radiogenic Nd isotope ratios that are identical within uncertainty, but up to 8 epsilon units distinct from the silicate phase. We interpret this as evidence for dynamic cycling between Fe-oxide phases in SPM and the river water, demonstrating the high reactivity of the labile Fe phase. Nd isotope and elemental molar ratios suggest that a significant amount of labile Fe- and Nd-bearing phases are derived from Fe-oxides within the sedimentary source rock rather than silicate mineral dissolution. Thus, sedimentary rock erosion and weathering provides an important source of labile Fe, manganese (Mn) and by extension potentially other trace metals. Our results imply that both past and future environmental change in the Arctic, such as permafrost thaw, may trigger changes to the supply of reactive trace metals. These results demonstrate that a re-evaluation of sediment reactivity within rivers is required where uplifted sedimentary rocks are present.

Influence of Hydrological Variables on Macrophytes in a Black Water River Ecosystem

This study assessed the influence of hydrological variables on macrophytes in a Black Water River ecosystem of Enyong River in Itu and Ibiono Local Government Areas of Akwa Ibom and Cross Rivers States, Nigeria. Four vegetation plots were chosen and in each of the plots, four belt transect were laid. In each transect, macrophyte were systematically sampled in four 10 m × 10 m quadrat at regular intervals. Macrophytes were identified to species level and their frequency and density determined. Water samples were obtained in each quadrat where the macrophytes were sampled and analyzed for their physicochemical properties using standardized methods. Altogether, 10 macrophyte species were encountered. Vossia cuspidata had the highest density (100.00±8.00 st/ha) and frequency values (100 %). Sacciolepis africana had the least density of 7.10±0.45 st/ha while Ludwigia octovalvis, Persicaria senegalensis, andSacciolepis africana had the least frequency of 25 %, respectively. The pH of the water was strongly acidic (5.54±0.03), electrical conductivity was low (20.00±5.77 µs/cm), temperature (29.00±1.10 ºC), Dissolved Oxygen (DO) (9.20±0.12 mg/l) and turbidity (7.10±0.06 NTU) values were high while Biological Oxygen Demand (BOD) (2.00±0.29 mg/l) Total Dissolved Solids (TDS) (10.00±0.29 mg/l) and Total Suspended Solids (TSS) were low (5.00±1.15 mg/l). Water Nutrients followed this decreasing order; chloride (3.55±0.02 mg/l) > nitrate (2.45±0.03 mg/l) > sulphate (2.02±0.06 mg/l) > phosphate (0.08±0.01 mg/l) and sulphide (0.03±0.02 mg/l). Heavy metals also followed this descending order; Pb (0.50±0.03 mg/l) > Zn (0.07±0.02 mg/l) > Cu (0.03±0.02 mg/l). Canonical Correspondence Analysis delineated 11 hydrological variables (temperature, pH, sulphate, turbidity, phosphate, BOD, nitrate, DO, TDS, sulphide and TSS) which exerted great influence on macrophyte distribution. V. cuspidata had affinity to pH and temperature, Sacciolepis africana had affinity to turbidity and BOD, Ludwigia octovalvis and Nymphaea lotus had affinity to sulphate and chloride, respectively, while Ipomoea aquatica and Alternanthera sessils had affinity to phosphate. On the other hand, Persicaria senegalensis, Salvinia molesta, Azolla pinnata and Ceratophyllum demersum had affinities to sulphide, DO, TSS and TDS, respectively. Since hydrological variables regulate macrophyte diversity and distribution, this study calls for consistent, monitoring and management of this ecosystem against future environmental changes. 
 Keywords: Aquatic plants, Black water, Canonical Correspondence Analysis, Ordination

The microbiota of intertidal macroalgae Fucus distichus is site-specific and resistant to change following transplant.

It is unclear how host-associated microbial communities will be affected by future environmental change. Characterizing how microbiota differ across sites with varying environmental conditions and assessing the stability of the microbiota in response to abiotic variation are critical steps towards predicting outcomes of environmental change. Intertidal organisms are valuable study systems because they experience extreme variation in environmental conditions on tractable timescales such as tide cycles and across small spatial gradients in the intertidal zone. Here we show a widespread intertidal macroalgae, Fucus distichus, hosts site-specific microbiota over small (meters to kilometres) spatial scales. We demonstrate stability of site-specific microbial associations by manipulating the host environment and microbial species pool with common garden and reciprocal transplant experiments. We hypothesized that F. distichus microbiota would readily shift to reflect the contemporary environment due to selective filtering by abiotic conditions and/or colonization by microbes from the new environment or nearby hosts. Instead, F. distichus microbiota was stable for days after transplantation in both the laboratory and field. Our findings expand the current understanding of microbiota dynamics on an intertidal foundation species. These results may also point to adaptations for withstanding short-term environmental variation, in hosts and/or microbes, facilitating stable host-microbial associations.

Looking for diversity in all the right places? Genetic diversity is highest in peripheral populations of the reef-building polychaete Sabellaria alveolata

Species distributions have been profoundly affected by past climate change, and are expected to change considerably in response to future environmental change. To better apprehend how future climate change is likely to affect genetic diversity in marine populations, it is essential to first evaluate the processes that have shaped the current distribution of genetic diversity in the sea. The honeycomb worm is a reef-building polychaete that hosts high biodiversity. Here we show that the genetic diversity in populations of S. alveolata is highest towards the edges of the current species range and lowest at its center. Pleistocene glacial cycles likely led to extirpations of S. alveolata from central populations in the Bay of Biscay, with coalescent-based estimates of post-glacial colonization dating to the beginning of the Holocene interglacial, from 10,000 to 14,000 years ago. Meanwhile, populations in the Irish Sea and English Channel likely persisted in glacial refugia since the Eemian interglacial, 120,000 years ago. Northern populations host at least two sets of divergent haplotypes, indicating that two refugia possibly existed in the north, with Ireland being a likely second refugium. Within biogeographic regions, populations were overall well-connected, but strong genetic differentiation suggests that little exchange occurs between regions. These two unexpected reservoirs of genetic diversity at the range edges deserve greater attention as warming temperatures threaten trailing edge populations, while greater climatic variability threatens leading edge populations.

The Case for Studying Highly Modified Agricultural Streams: Farming for Biogeochemical Insights

AbstractA significant fraction of Earth's land surface is used for agriculture, which has led to extensive modification and degradation of streams and rivers. Although highly modified, agricultural streams offer important opportunities for advancing our understanding of agroecosystems and applying the principles of translational ecology. Using examples from the upper midwestern U.S., we discuss how highly modified agricultural streams can be used to gain insights into ecological and biogeochemical processes, though often this involves adjusting the paradigms and approaches used to study streams in less disturbed landscapes. We argue that highly modified agricultural streams could serve as a model for how less disturbed systems might respond to ongoing and future environmental change. Last, these streams often are targets for restoration, which opens the door to engaging with diverse stakeholders, including policymakers and nontraditional funding sources such as philanthropic foundations and industry groups.

Sexual reproduction in the soft coral Lobophytum schoedei in Bolinao‐Anda Reef Complex, Pangasinan, northwestern Philippines

AbstractThe characterization of early life‐history strategies of soft corals is important in understanding population maintenance, replenishment, and recovery in disturbed coral reefs. This study examined the sexual reproduction of the soft coral Lobophytum schoedei in the Bolinao‐Anda Reef Complex (BARC), a degraded reef in northwestern Philippines. Reproductive strategies such as sexuality, sex ratio, fecundity, and reproductive timing were examined. Random colonies of L. schoedei were sampled a few weeks before the predicted time of spawning to assess fecundity (n = 73 colonies), and sexuality and sex ratio (n = 221 colonies). Monthly sampling of tagged colonies of L. schoedei (n = 20) was done over 13 months to determine the reproductive timing through polyp dissection. Peak of annual spawning was inferred based on the presence of large gametes and their absence in the next sampling period. Results showed that L. schoedei is a gonochoric broadcast spawner with 1:1.1 sex ratio. Although oogenesis and spermatogenesis exhibited overlapping cycles, both gametes matured and spawned in April, coinciding with increasing sea surface temperature. Prior to spawning, oocytes and spermaries ranged 300–633 µm and 150–337 µm in diameter, respectively. Mean female fecundity was 6.7 ± 3.9 oocytes per polyp and male fecundity was 39.2 ± 22.5 (±SD) spermaries per polyp. Some of these results, including the low number of oocytes produced by female polyps, may be caused by sexual reproduction in a degraded reef environment. Understanding these reproductive traits may be useful for predicting the resiliency of populations of L. schoedei in response to ongoing and future environmental change.

Global warming assessment suggests the endemic Brazilian kelp beds to be an endangered ecosystem

Kelps are canopy-forming brown seaweed sustaining critical ecosystem services in coastal habitats, including shelter, nursery grounds, and providing food resources to a myriad of associated species. This study modeled the fundamental niche of Laminaria abyssalis along the Brazilian continental margin, an endemic species of the South Atlantic, to anticipate potential distributional range shifts under two contrasting scenarios of future environmental changes (RCP2.6 and RCP8.5). The model for fundamental niche predictions considering the “present scenario” has shown a wider potential area than the realized niche (i.e., the area where the species actually occurs) along the Brazilian coast. In both future scenarios, the models have shown niche erosion on the northern portion of the Brazilian coast and niche gains towards the south. In both scenarios, L. abyssalis populations tend to shift to deeper regions of the reef. The restricted range of occurrence (33,000 km2), intense anthropic activities along these beds (e.g., trawling fisheries, oil/gas mining, or removal for agricultural purposes) acting synergically with global warming, may drive this ecosystem to collapse faster than kelp species’ ability to adapt. We propose to classify L. abyssalis as Endangered - (EN) under IUCN criteria, and highlight that long-term monitoring of kelp beds is an urgent need to develop effective conservation initiatives to protect such rare and invaluable ecosystem.

Mind the gaps: Comparison of representative vs opportunistic assessment of tree regeneration in Central European beech forests

Tree regeneration (TR) in canopy gaps is a key process to understand how forest ecosystems might adapt to future environmental changes. Since successful TR is the result of a complex interplay of several stochastic events such as gap formation, seed production, ungulate pressure and diseases, some of the processes have been neglected or strongly reduced for model applications. Most empirical data on TR originate from (national) forest inventories based on statistically optimized designs for timber resource estimations and use geographically fixed permanent plots. Consequently, these representative samples record TR both in gaps as well as under closed canopy conditions. In this study, we compared TR in 63 representative plots of the Swiss National Forest Inventory (‘NFI sampling’), located in beech and silver fir-beech forests along an elevation gradient in the Jura Mts., with an opportunistic ‘gap sampling’ strategy targeting TR-clusters. We analyzed quantitative (e.g., number of individuals) and qualitative (e.g., species diversity, similarity to surrounding canopy) differences between the ‘NFI sampling’ and ‘gap sampling,’ as well as the environmental factors (e.g., gap size, cluster age, elevation) influencing the composition of TR in small canopy gaps. The ‘gap sampling’ recorded higher median TR densities (+62%, stems ha−1) and species richness (4.0 ± 2.1, mean ± sd) than the ‘NFI sampling’. More importantly, the ‘gap sampling’ provided much more consistent results among sites (i.e., 4x lower variance). Consequently, the ‘gap sampling’ revealed not only general but also species-specific patterns across TR size classes and along elevational gradients in contrast to the lack of patterns in the ‘NFI sampling’. Species richness decreased as TR grew taller, and the tallest TR size class (>130 cm) was almost solely comprised of the dominant species in the surrounding canopy (direct ingrowth). The high amount of direct ingrowth in TR indicates that small canopy gaps might offer only limited management potential to alter forests and that extensive disturbances or management at early TR stages (sapling) would be necessary to promote species better suited to the expected future site conditions. We raise the question of whether a forest monitoring that is statistically optimized for timber resource estimation is best suited to detect adaptation effects to quickly changing environments best visible at the regeneration stage, or whether forest inventory tools should be extended by methods that focus on disturbed parts of forests where changes and adaptations take place. We propose the implementation of an opportunistic gap-based monitoring of TR that essentially serves to identify the best forest management strategies (e.g. gap size, intervention intervals) in forests adapting to environmental change.