Indirect Effects Of Climate Change Research Articles

Impact of Climate Change on the Number of Threatened Species: International Evidence

Global warming is the price for economic development. Rapid industrialization produces greenhouse gases that trap the heat and make the earth warmer. The rise in temperature and changes in precipitation resulted in extreme weather conditions. Global climate change affects both physical and biological environments and the impacts on biodiversity is directly and indirectly. The direct effects of climate change includes the increased in temperature and precipitation that affect individual organisms, populations, species distribution and ecosystem compositions and functions. The indirect effects of climate change are through increased salinity and extreme weather events such as floods, cyclones and droughts that will have a profound negative impacts on the forest and biodiversity. The present study investigates the impact of climate change on the number of threatened species as proxy for biodiversity loss using a cross-national data consisting of 98 countries. We have estimated the impact of temperature, precipitation and the number of natural disasters occurrences on the number of threatened species, in particular birds, fishes, mammals, plants and reptiles. As control variables, we have considered government effectiveness (proxy for good governance) and the level of economic development (proxy for wealth). By employing Ordinary Least Square (OLS) with robust standard error and quantile regressions analyses, our results suggest that all three climate change indicators – temperature, precipitation and the number of natural disasters occurrences increase the number of threatened species (biodiversity loss). Higher economic development also affect the number of threatened species positively. On the other hand, good governance such as government effectiveness reduces the number of threatened species. Thus, practicing good governance, promoting conservation of the environment and the control of greenhouse gasses would able to mitigate biodiversity loss.

Ignoring biotic interactions overestimates climate change effects: The potential response of the spotted nutcracker to changes in climate and resource plants

AbstractAimProjecting future distributions of species under climate change remains a particular challenge for species that are trophically interacting. Interaction partners are often assumed to react differently to climate change, causing spatial mismatches in future distributions and increased extinction risks. We compare potential direct effects of climate change with combined direct and indirect effects mediated via food plants on a highly specialized bird species.LocationEurope.TaxonEuropean spotted nutcracker (Nucifraga caryocatactes).MethodsWe used climate‐based species distribution models to project probabilities of occurrence of European spotted nutcrackers and their main food sources, Swiss stone pine (Pinus cembra) and common hazel (Corylus avellana) under climate change. We combined direct climate change effects on the bird and indirect effects via the food plants by calculating the probabilities of plants and nutcrackers occurring together.ResultsWe find considerable projected northward shifts in future occurrences of nutcrackers under climate change and similar effects on hazel. In contrast, projections for Swiss stone pine indicate minor altitudinal upward shifts. Combined projections of direct and indirect effects of climate change indicate less pronounced shifts of nutcrackers’ occurrences, due to relatively small changes in pine's occurrences and to suitable hazel occurrence shifts.Main conclusionsOur study suggests that potential effects of climate change on the future distribution of the nutcracker might be overestimated when ignoring trophically interacting plants in future projections. Models of direct effects of climate change on nutcrackers’ occurrence probabilities project greater range losses than models of combined direct and indirect effects via resource plants. Therefore, considering biotic interactions does not necessarily increase the risks that climate change may impose on species distributions, but could reduce overestimation of potential range losses in rapidly changing environments.

Direct and indirect effects of climate change squeeze the local distribution of a habitat-forming seaweed

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 626:43-52 (2019) - DOI: https://doi.org/10.3354/meps13080 Direct and indirect effects of climate change squeeze the local distribution of a habitat-forming seaweed Gustavo M. Martins1,2,*, Christopher D. G. Harley3,4, João Faria1, Maria Vale1,5,6, Stephen J. Hawkins6,7, Ana I. Neto1, Francisco Arenas8 1cE3c-Centre for Ecology, Evolution and Environmental Changes/Azorean Biodiversity Group & University of the Azores, 9501-801 Ponta Delgada, Açores, Portugal 2AQUAZOR - Aquicultura e Biotecnologias Marinhas dos Açores, Rua da Pranchinha 92, 9500-331 Ponta Delgada, Açores, Portugal 3Department of Zoology, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada 4Institute for the Oceans and Fisheries, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada 5Regional Fund for Science and Technology (FRCT), 9500-336 Ponta Delgada, Açores, Portugal 6Ocean and Earth Science, National Oceanography Centre Southampton, Waterfront Campus, University of Southampton, European Way, Southampton SO14 3ZH, UK 7Marine Biological Association of UK, The Laboratory, Citadel Hill, Plymouth PL1 2PB, UK 8Group of Aquatic Ecology and Evolution, Interdisciplinary Centre of Marine and Environmental Research (CIIMAR/CIMAR), University of Porto, 4450-208 Matosinhos, Portugal *Corresponding author: martinsgm@gmail.com ABSTRACT: Predictions concerning biological responses to climate change are based primarily on environmental tolerances of individual species. However, biological interactions and the way these may be altered by changes in climate can also be important drivers of ecological change. A combination of observational and experimental studies was conducted to test the factors controlling the vertical distribution of the canopy-forming alga Fucus guiryi, a cold-water seaweed and ecological engineer. We found that F. guiryi transplanted to areas just above its upper limit of distribution died rapidly, whereas survivorship was high in unmanipulated controls and individuals translocated to areas within the species’ vertical range. Towards the lower limit of its vertical range, unprotected F. guiryi were heavily grazed by a warm-water fish, Sarpa salpa, and percent cover, frond length, and number of reproductive structures were all reduced compared to experimentally protected individuals. Observations over a period of 2 yr suggest that grazing is stronger towards the lower limit of distribution, especially during the warmer seasons of the year. Commercial landing records indicate that the abundance of S. salpa was positively related to warmer sea surface temperatures. Our results highlight the interplay between abiotic and biotic factors in determining the vertical distribution of F. guiryi and suggest that predicted increases in temperature during this century may lead to local extinctions of this ecosystem engineer through the combination of increased physiological stress at its upper limit of distribution and grazing at its lower limit, which, together, act to squeeze its vertical distribution in the rocky intertidal. KEY WORDS: Biotic interactions · Distribution · Fucus guiryi · Physical stress · Rocky intertidal · Grazing Full text in pdf format Supplementary material PreviousNextCite this article as: Martins GM, Harley CDG, Faria J, Vale M, Hawkins SJ, Neto AI, Arenas F (2019) Direct and indirect effects of climate change squeeze the local distribution of a habitat-forming seaweed. Mar Ecol Prog Ser 626:43-52. https://doi.org/10.3354/meps13080 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 626. Online publication date: September 12, 2019 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2019 Inter-Research.

Flexibility in a changing arctic food web: Can rough-legged buzzards cope with changing small rodent communities?

Indirect effects of climate change are often mediated by trophic interactions and consequences for individual species depend on how they are tied into the local food web. Here we show how the response of demographic rates of an arctic bird of prey to fluctuations in small rodent abundance changed when small rodent community composition and dynamics changed, possibly under the effect of climate warming. We observed the breeding biology of rough-legged buzzards (Buteo lagopus) at the Erkuta Tundra Monitoring Site in southern Yamal, low arctic Russia, for 19years (1999-2017). At the same time, data on small rodent abundance were collected and information on buzzard diet was obtained from pellet dissection. The small rodent community experienced a shift from high-amplitude cycles to dampened fluctuations paralleled with a change in species composition toward less lemmings and more voles. Buzzards clearly preferred lemmings as prey. Breeding density of buzzards was positively related to small rodent abundance, but the shift in small rodent community lead to lower numbers relative to small rodent abundance. At the same time, after the change in small rodent community, the average number of fledglings was higher relative to small rodent abundance than earlier. These results suggest that the buzzard population adapted to a certain degree to the changes in the major resource, although at the same time density declined. The documented flexibility in the short-term response of demographic rates to changes in structure and dynamics of key food web components make it difficult to predict how complex food webs will be transformed in a warmer Arctic. The degree of plasticity of functional responses is indeed likely to vary between species and between regions, depending also on the local food web context.

Contrasting consequences of climate change for migratory geese: Predation, density dependence and carryover effects offset benefits of high-arctic warming.

Climate change is most rapid in the Arctic, posing both benefits and challenges for migratory herbivores. However, population-dynamic responses to climate change are generally difficult to predict, due to concurrent changes in other trophic levels. Migratory species are also exposed to contrasting climate trends and density regimes over the annual cycle. Thus, determining how climate change impacts their population dynamics requires an understanding of how weather directly or indirectly (through trophic interactions and carryover effects) affects reproduction and survival across migratory stages, while accounting for density dependence. Here, we analyse the overall implications of climate change for a local non-hunted population of high-arctic Svalbard barnacle geese, Branta leucopsis, using 28years of individual-based data. By identifying the main drivers of reproductive stages (egg production, hatching and fledging) and age-specific survival rates, we quantify their impact on population growth. Recent climate change in Svalbard enhanced egg production and hatching success through positive effects of advanced spring onset (snow melt) and warmer summers (i.e. earlier vegetation green-up) respectively. Contrastingly, there was a strong temporal decline in fledging probability due to increased local abundance of the Arctic fox, the main predator. While weather during the non-breeding season influenced geese through a positive effect of temperature (UK wintering grounds) on adult survival and a positive carryover effect of rainfall (spring stopover site in Norway) on egg production, these covariates showed no temporal trends. However, density-dependent effects occurred throughout the annual cycle, and the steadily increasing total flyway population size caused negative trends in overwinter survival and carryover effects on egg production. The combination of density-dependent processes and direct and indirect climate change effects across life history stages appeared to stabilize local population size. Our study emphasizes the need for holistic approaches when studying population-dynamic responses to global change in migratory species.

Interspecific plant competition mediates the metabolic and ecological signature of a plant–herbivore interaction under warming and elevated CO2

Abstract Biotic interactions shape community evolution, but we lack mechanistic insights on how metabolic and ecological processes under climate change are altered by biotic interactions. We used a two‐trophic model community consisting of the aphid Dysaphis plantaginea feeding on the forb Plantago lanceolata, and a grass competitor Lolium perenne that does not experience herbivory by the aphid. Monocultures and mixtures were exposed to the herbivory treatment and to three relevant simulated environmental changes as prevalent under current climate change (increased temperature, CO2, and increased temperature and CO2) Elevated CO2 reduced the nitrogen content of P. lanceolata, while simultaneous increases of CO2 and temperature modified the plant metabolic component and the magnitude of these responses in different directions. Elevated CO2 enhanced defence systems in P. lanceolata, but these effects were not altered by warming. Interspecific plant competition did, however, neutralize these responses. There were no indirect effects of climate change on aphid population growth despite changes in plant defence, nutritional quality and biomass induced by our environmental change scenarios. We thus demonstrate interactions between abiotic and biotic processes on plant metabolite profiles, but more importantly, that climate change effects on a selection of the metabolic pathways are altered by herbivory and competition. Our experiment under semi‐natural conditions thus demonstrates the non‐additive and often neutralizing effects of biotic interactions on plant metabolism and species performance under climate‐associated environmental change. A free Plain Language Summary can be found within the Supporting Information of this article.

Community regulation models as a framework for direct and indirect effects of climate change on species distributions

AbstractExisting projections of climate change impacts focus primarily on direct abiotic impacts on individuals and populations. However, these models often ignore species interactions, which are vital for determining community composition and structure. To evaluate both direct and indirect effects of climate change on species distributions, we applied the Menge–Sutherland model, which describes the relative role of predation and environmental stress in regulating community structure. Using a space‐for‐time approach, we tested the predictions that (1) predators are more strongly impacted by increasing environmental stress than prey (as described in the Menge–Sutherland model) and (2) incorporating indirect (predator) effects increases our ability to predict impacts of increased temperature on prey distributions. We surveyed vertical distributions of predators (sea stars) and a foundational prey species (mussels) at 20 intertidal sites spanning a thermal gradient along the West Coast of the United States. Using generalized linear models and structural equation models, we found that as temperature increased, the upper limits of foundational prey species decreased (a direct effect), while prey lower limits also shifted downward, due to an indirect effect of temperature on predator distributions. Under future climate change, mussel ranges may undergo vertical shifts toward subtidal habitats, allowing for localized persistence of mussels and associated species. Our model comparisons indicate that this framework—incorporating both direct and indirect environmental stress effects within a classic community regulation model—can improve prediction of responses to warming. Community regulation models could be expanded to inform management and conservation efforts during unprecedented climate and ecological change.

Forest understory vegetation is more related to soil than to climate towards the cold distribution margin of European beech

AbstractQuestionIt is debated whether forest understory communities will be sensitive to projected climate change or inert due to the regulating effect of local site conditions and soil parameters. A distinction between the relative importance of climate or soil is often hardly possible because both factors usually change at different spatial scales in forests. Here, we compare the relative influence of climate and soil on the forest understory vegetation in lowland beech forest ecosystems (Fagus sylvatica), which were selected for their ecological homogeneity.LocationNine sites along a strong temperature gradient (ΔT = 4 K from east to west in winter, south to north in summer) between Rostock (Germany) and Gdańsk (Poland) in a Baltic Quaternary ground moraine landscape.MethodsWe conducted a vegetation survey in 55 vegetation plots (80 m2 each) across nine forest sites mono‐dominated by European beech and analysed how much variation in understory plant composition is explained by climate and soil parameters.ResultsSoil explained 32% of the compositional variation of understory vegetation across sites, climate 22%, and their interaction 14%. Topsoil pH, subsoil organic matter content, and subsoil C/N ratio were the most important soil variables; growing season temperature and annual water availability were the most important climatic variables.ConclusionThe strong dependence on soil properties could moderate the response of the forest understory vegetation to projected climate change. Forest soil properties, however, also depend on the dominant tree species and the macroclimate. To predict climate change impacts on forest understory vegetation, climate change assessments should consider indirect climate change effects as well as interactions between climate and soil.

Potential impacts of climate change on groundwater resources: A multi-regional modelling assessment

The complexity of understanding the groundwater resources in relation to climate change is caused by direct and indirect effects of climate change on hydrological processes. The study herein aims at implementing a physically based groundwater model to investigate the effects of climate change on groundwater system under 15 general circulation models (GCMs) in a semi-arid region from 2020 to 2044. A non-parametric probability density function estimator was used to quantify the level of uncertainties in the simulations. The method was applied to an area of 2073 km\(^{2}\) in southwest Iran, consisting of five plains: western Dez, eastern Dez, Sabili, Deymche and Lor. The results indicate that there is a decline in the recharge in April, May, June and October. The range of changes in the recharge was determined to be between \(-10\%\) and \(+13\%\) in the Sabili plain, \(-6\%\) and \(+10\%\) in the Deymche plain, \(-4\%\) and \(+10\%\) in the western-Dez plain, \(-6\%\) and \(+26\%\) in the eastern-Dez plain, and \(-40\%\) and \(+100\%\) in the Lor plain. The most significant decline in the groundwater level occurred in the Sabili plain in September. The largest uncertainty in the simulation of recharge under GCM scenarios was determined to be in August, September and December. This study highlights that climate change can have a significant effect on groundwater resources in the region that reinforces the need for groundwater management plans and a long-term perspective.

Groundwater Extraction in Floodplain Forests Reduces Radial Growth and Increases Summer Drought Sensitivity of Pedunculate Oak Trees (Quercus robur L.)

In future, groundwater dependent ecosystems are likely to face increasing stress from direct and indirect effects of climate change. European floodplain forests already experience lower groundwater tables caused by river regulations and water extraction. Yet, the effects of more frequent and prolonged dry and hot periods in combination with groundwater extraction on floodplain forests are not well understood. Here, we conducted a dendroecological study in floodplain forests dominated by pedunculate oak (Quercus robur), a widespread forest type in Europe. Since drought-related precipitation deficits are increasingly less compensated by available groundwater, we hypothesized that groundwater extraction would increase climate sensitivity of growth. Moreover, we expected that younger trees that established under the condition of lowered groundwater tables would be less sensitive to droughts in contrast to older trees that might not be able to adapt to abrupt changes in groundwater levels. In three regions in the Upper Rhine Valley of Germany, we analysed retrospectively tree-ring growth in Q. robur stands where (a) water extraction had dramatically lowered groundwater levels and trees presumably lost direct access to it, or (b) trees have not been affected by water extraction. In addition, (c) nearby sessile oak (Q. petraea) stands at upland sites were analysed to isolate the climate signal for each study region from a groundwater signal. In total, we analysed ring-width chronologies from 18 forest stands and investigated their relationship with climate. Radial growth of oak trees was strongly correlated with summer drought (SPEI, Standardized Precipitation Evapotranspiration Index). Their sensitivity to summer drought increased significantly following the onset of groundwater extraction (88-49 years ago). However, sensitivity of oaks to summer drought at sites with groundwater contact remained relatively stable over time. Oaks at sites without water extraction took advantage of favourable growing conditions. Our results show that access to groundwater can buffer negative effects of summer drought on tree growth. Therefore, in the face of the ongoing climate change and more frequent occurrence of extreme drought events, we recommend that groundwater extraction from floodplain forests should be reduced rather than increased to maintain tree vitality in the long term.

Community composition influences the population growth and ecological impact of invasive species in response to climate change.

Predicting long-term impacts of introduced species is challenging, since stressors related to global change can influence species-community interactions by affecting both demographic rates of invasive species and the structure of the invaded ecosystems. Invasive species can alter ecosystem structure over time, further complicating interactions between invasive species and invaded communities in response to additional stressors. Few studies have considered how cumulative impacts of species invasion and global change on the structure of invaded ecosystems may influence persistence and population growth of introduced species. Here, we present an empirically based population model for an invasive epiphytic bryozoan that can dramatically alter the structure of its invaded kelp bed ecosystems. We use this model to predict the response of invasive species to climate change and associated changes in the invaded community. Population growth of the bryozoan increased under near-future projections of increasing ocean temperature; however, the magnitude of population growth depended on the community composition of invaded kelp beds. Our results suggest that, in some cases, indirect effects of climate change mediated through changes to the structure of the invaded habitat can modulate direct effects of climate change on invasive species, with consequences for their long-term ecological impact. Our findings have important implications for management of invasive species, as modifying invaded habitats at local to regional scales may be more logistically feasible than addressing stressors related to global climate change.

Direct and indirect effects of climate change on Cymodocea nodosa in the Canary Islands

Direct and indirect effects of climate change on Cymodocea nodosa in the Canary Islands

Impact of climate change on national vulnerability

The issue of climate change is a topic of close concern to both domestic and foreign society, and it is also an important issue affecting the sustainable development of all mankind. This article explains the impact of climate change on the country in two representative countries: Chad and Afghanistan. To measure a country’s vulnerability index and how it is affected by climate change, we identified four main indicators of climate change: temperature, precipitation, forest area, and agricultural land area to analyse the country’s vulnerability index. The indirect effects of climate change are measured using the Spearman coefficient matrix.

A risk assessment of Europe's black truffle sector under predicted climate change

The black truffle (Tuber melanosporum) is a highly revered culinary icon species that grows symbiotically with its host trees across several parts of southern Europe. Where harvested under natural or cultivated conditions, truffles can have a significant socioeconomic impact and may even form a key component of cultural identity. Although some aspects of truffle biology and ecology have been elucidated recently, the role of abiotic, environmental and climatic factors in the production and maturation of their fruitbodies is still largely unknown. Based on 36-year-long, continuous records of Mediterranean truffle yield, we demonstrate that decreased summer precipitation together with increased summer temperatures significantly reduce the fungus' subsequent winter harvest. Using state-of-the-art climate model projections, we predict that a significant decline of 78–100% in southern European truffle production is likely to occur between 2071 and 2100. The additional threats of forecasted heatwaves, forest fires, pest and disease outbreaks are discussed along with socioeconomic and ecological consequences of a warmer and dryer future climate. Our results emphasize the need for unravelling the direct and indirect effects of climate change on Europe's truffle sector and underline the importance of conservation initiatives at local to international scales.

Transplants, Open Top Chambers (OTCs) and Gradient Studies Ask Different Questions in Climate Change Effects Studies.

Long-term monitoring, space-for-time substitutions along gradients, and in situ temperature manipulations are common approaches to understand effects of climate change on alpine and arctic plant communities. Although general patterns emerge from studies using different approaches, there are also some inconsistencies. To provide better estimates of plant community responses to future warming across a range of environments, there have been repeated calls for integrating different approaches within single studies. Thus, to examine how different methods in climate change effect studies may ask different questions, we combined three climate warming approaches in a single study in the Hengduan Mountains of southwestern China. We monitored plant communities along an elevation gradient using the space-for-time approach, and conducted warming experiments using open top chambers (OTCs) and plant community transplantation toward warmer climates along the same gradient. Plant species richness and abundances were monitored over 5 years addressing two questions: (1) how do plant communities respond to the different climate warming approaches? (2) how can the combined approaches improve predictions of plant community responses to climate change? The general trend across all three approaches was decreased species richness with climate warming at low elevations. This suggests increased competition from immigrating lowland species, and/or from the species already growing inside the plots, as indicated by increased biomass, vegetation height or proportion of graminoids. At the coldest sites, species richness decreased in OTCs and along the gradient, but increased in the transplants, suggesting that plant communities in colder climates are more open to invasion from lowland species, with slow species loss. This was only detected in the transplants, showing that different approaches, may yield different results. Whereas OTCs may constrain immigration of new species, transplanted communities are rapidly exposed to new neighbors that can easily colonize the small plots. Thus, different approaches ask slightly different questions, in particular regarding indirect climate change effects, such as biotic interactions. To better understand both direct and indirect effects of climate change on plant communities, we need to combine approaches in future studies, and if novel interactions are of particular interest, transplants may be a better approach than OTCs.

The compounding consequences of wildfire and climate change for a high‐elevation wildflower (Saxifraga austromontana)

AbstractAimHigh‐elevation plants are disproportionally affected by climate change. As temperatures rise, the amount of available alpine habitat in the Rocky Mountains will decrease resulting in potential local extinctions of plant species. In addition to the direct effects of climate‐driven habitat loss, alpine plants must also respond to indirect effects, such as changes in disturbance regimes. One notable shift is the increase of wildfire frequency in regions where fire was previously rare or absent, including the alpine. We hypothesized that direct climatic changes compounded with increased wildfire frequency will reduce the future suitable habitat of high‐elevation plants more than if climate was considered alone.LocationRocky Mountain Floristic Region, western North America.TaxonSaxifraga austromontana (Saxifragaceae), a wildflower endemic to high elevations of the Rocky Mountain Floristic Region.MethodsOur approach integrated historical herbarium records, field surveys, remote sensing, species distribution models, historic wildfire data, and predictive models.ResultsOur results indicate wildfire has significantly reduced the abundance and increased the likelihood of extirpation for S. austromontana. Increased fire frequency compounded with direct climatic changes will likely reduce the range of the species by approximately 43% by 2050 compared to 38% due to climate alone, under a moderate CO2 emissions scenario. The influence of wildfire varies regionally. For instance, the Middle Rockies will likely lose 74% of its suitable habitat of which 16% may be lost due to fire, while other regions, such as the northern range, will be less negatively affected by direct and indirect effects.Main ConclusionsOur evidence that increased wildfire frequency will compound the impacts of climate change on alpine taxa in North America led to the development of a new, general hypothesis on the fundamental interaction between direct and indirect effects of climate change on species range reductions.

Indirect effects of climate change altered the cannibalistic behaviour of shell-drilling gastropods in Antarctica during the Eocene.

The fossil record from Seymour Island, Antarctic Peninsula, provides a record of biotic response to the onset of global climatic cooling during the Eocene. Using drilling traces—small, round holes preserved on prey shells—we examined the effect of a cooling pulse 41 Ma on the cannibalistic behaviour of predatory naticid gastropods. We predicted that cannibalistic attacks would decline in response to the cooling climate, reflecting reduced activity levels, energy requirements and constraints on the chemically aided drilling process of the naticids. Surprisingly, however, cannibalism frequencies did not change. This counterintuitive result is best explained by a sharp reduction in durophagous (shell-crushing) predation in shallow-benthic communities in Antarctica that also occurred as the climate cooled. Reduced durophagous predation may have created a less-risky environment for foraging naticids, stimulating cannibalistic behaviour. The change in the top-down control exerted by shell-crushing predators on naticids may have counteracted the direct, negative effects of declining temperatures on the predatory performance of naticids. Our results suggest that the long-term consequences of climate change cannot be predicted solely from its direct effects on predation, because the temperature can have large indirect effects on consumer–resource interactions, especially where risk-effects dominate.

Reorganization of aquatic communities from low-nutrient lakes in northwestern New Brunswick, Canada

Sparse monitoring of New Brunswick (Canada) lakes creates challenges for understanding mechanisms of deteriorating water quality, such as recent instances of increased cyanobacterial biomass in low-nutrient systems. To assess long-term environmental change experienced by low-nutrient, dimictic New Brunswick lakes we use sedimentary remains of algal pigments and Cladocera in dated cores from impact (prone to late-summer algal blooms, Lac Unique) and reference (no observed algal blooms, First and States) lakes. Overall, all three lakes now exhibit greater bosminid abundance and fewer daphniids, lower Cladocera richness, and smaller average cladoceran body size, although some lake-specific differences in assemblage response exist that cannot be related solely to top-down or bottom-up forces. Zooplankton trends are most pronounced at Lac Unique and First Lake, where algal production is generally greater. Across all three lakes, the only significant (IndVal: p < 0.05) cladoceran bioindicator of the post-1990 period is the pelagic bosminid group, whereas prior to ~ 1990, Daphnia longispina-complex and several littoral taxa were significant (IndVal: p < 0.05) bioindicators. These temporal shifts suggest that the smaller-bodied bosminid group may now be favored over its larger-bodied pelagic competitor Daphnia sp. in these lakes, irrespective of heterogeneous long-term algal patterns inferred from stable sedimentary pigments. We suggest that the indirect effects of climate change, principally during the spring and summer quarters in New Brunswick, may be associated with marked shifts in limnological structure, as evidenced by changes in dominant zooplankton of the pelagic zone. However, further research is needed to rule out whether or not size-selective predation, and its potential interactions with climate change and other stressors, are key mechanisms favoring increased bosminids in low-nutrient, dimictic lakes.

Increasing temperature and decreasing specific leaf area amplify centipede predation impact on Collembola

Collembola is an abundant group of soil organisms playing a major role on litter decomposition process and nutrient cycling in forest ecosystems. Habitat structure strongly influences Collembola assemblages as plant litter physical characteristics and quantity provide structural niches and determine the outcome of their interactions with predators. Collembola are also extremely sensitive to environmental conditions such as soil temperature that control their demographic parameters and activity. In this context, increasing temperature with the ongoing climate change can have strong impact on Collembola assemblages and their responses to predation either directly by altering their behaviour or indirectly by altering their habitat structure. We therefore examined how the increase of temperature combined to the decrease of specific leaf area (SLA, a major functional plant trait) of the European common oak (Quercus robur L.) and the presence of a centipede predator (Chilopoda: Lithobiidae) will affect the abundance of Folsomia candida (Collembola: Isotomidae) in a 5-week microcosm experiment. Increasing temperature, decreasing SLA and presence of centipede altered F. candida abundance. We observed a significant temperature × predation interaction suggesting differential effects of increasing temperature on F. candida abundance with and without predator. We also observed a significant SLA × predation interaction highlighting that lower SLA decreases F. candida abundance only in predator presence. Finally, our findings evidenced that increasing temperature and decreasing SLA amplify the negative effect of centipede predation on F. candida abundance, suggesting that both direct and indirect effects of climate change would conjointly strengthen the top-down control of predators on preys.

Sensitivity and response of low-nutrient lakes to post twentieth century environmental change in New Brunswick, Canada

A paleolimnological approach was used at 45 mostly remote, low-nutrient lakes in New Brunswick (NB), Canada, to determine bioindicator responses and lake sensitivity to post twentieth century environmental change. From each undated core we assessed zooplankton (Cladocera) change between discrete time periods using related assemblage metrics, including the rise of Bosmina sp., cladoceran richness, and average assemblage body size. Cladocerans from a pre-industrial interval (20–20.5 cm) were compared to those from a present-day interval (0–0.5 cm). Lakes were then classified as either high- or low-sensitivity based on assemblage metrics, and sensitivity group differences in physical–chemical measures were tested for significance. Compared to pre-industrial times, Bosmina sp. relative abundance increased in 33 of 43 lakes (75% of lakes surveyed) by on average 20%. Body size and rarefied species richness of assemblages decreased significantly. These ecological shifts detected at an important intermediate trophic level are attributable to indirect effects of climate change, although we cannot rule out shifts in fish predation and littoral habitat as additional structuring factors. Eighteen lakes were classified as high-sensitivity lakes and showed significant differences in latitude, surface area, elevation, dissolved calcium and magnesium concentrations, and conductivity compared to 25 low-sensitivity lakes. In high-sensitivity lakes, richness decreased on average by 6 species and body size decreased by 0.2 mm. This study presents a historical context for constructing effective conservation and management efforts at a time of substantial environmental change in low-nutrient NB lakes.