An indoor mesocosm system to study the effect of climate change on the late winter and spring succession of Baltic Sea phyto- and zooplankton

An indoor mesocosm system was set up to study the response of phytoplankton and zooplankton spring succession to winter and spring warming of sea surface temperatures. The experimental temperature regimes consisted of the decadal average of the Kiel Bight, Baltic Sea, and three elevated regimes with 2°C, 4°C, and 6°C temperature difference from that at baseline. While the peak of the phytoplankton spring bloom was accelerated only weakly by increasing temperatures (1.4 days per degree Celsius), the subsequent biomass minimum of phytoplankton was accelerated more strongly (4.25 days per degree Celsius). Phytoplankton size structure showed a pronounced response to warming, with large phytoplankton being more dominant in the cooler mesocosms. The first seasonal ciliate peak was accelerated by 2.1 days per degree Celsius and the second one by 2.0 days per degree Celsius. The over-wintering copepod populations declined faster in the warmer mesocosm, and the appearance of nauplii was strongly accelerated by temperature (9.2 days per degree Celsius). The strong difference between the acceleration of the phytoplankton peak and the acceleration of the nauplii could be one of the “Achilles heels” of pelagic systems subject to climate change, because nauplii are the most starvation-sensitive life cycle stage of copepods and the most important food item of first-feeding fish larvae. Priority programme of the German Research Foundation—contribution 3.     

An indicator highlights seasonal variation in the response of Lepidoptera communities to warming

The impacts of climate change on species and ecosystems are increasingly evident. While these tend to be clearest with respect to changes in phenology and distribution ranges, there are also important consequences for population sizes and community structure. There is an urgent need to develop ecological indicators that can be used to detect climate-driven changes in ecological communities, and identify how those impacts may vary spatially. Here we describe the development of a new community-based seasonal climate change indicator that uses national population and weather indices. We test this indicator using Lepidopteran and co-located weather data collected across a range of UK Environmental Change Network (ECN) sites. We compare our butterfly indicator with estimates derived from an alternative, previously published metric, the Community Temperature Index (CTI).First, we quantified the effect of temperature on population growth rates of moths and butterflies (Species Temperature Response, STR) by modelling annual variation in national population indices as a function of nationally averaged seasonal variation in temperature, using species and weather data independent of the ECN data. Then, we calculated average STRs for annually summarised species data from each ECN site, weighted by species’ abundance, to produce the Community Temperature Response (CTR). Finally, we tested the extent to which CTR correlated with spatial variation in temperature between sites and the extent to which temporal variation in CTR tracked both annual and seasonal warming trends.Mean site CTR was positively correlated with mean site temperature for moths but not butterflies. However, spatial variation in moth communities was well explained by mean site summer temperature and butterfly communities by winter temperature, respectively accounting for 74% and 63% of variation. Temporal variation in moth and butterfly CTR within sites did not vary with the mean annual temperature but responded to variation in the mean temperature of specific seasons. There were positive correlations between moth seasonal CTRs and seasonal temperatures in winter, spring and summer; and butterfly seasonal CTRs and seasonal temperatures in winter and summer. Butterfly CTR and CTI both correlated spatially and temporally with winter temperature.Our results highlight the need for seasonality to be considered when examining the impact of climate change on communities. Seasonal CTRs may be used to track the impact of changing temperatures on biodiversity and help identify potential mechanisms by which climate change is affecting communities. In the case of Lepidoptera, our results suggest that future warming may reassemble Lepidoptera communities.     

Effects of temperature on spring bloom dynamics of epilithic diatom communities in the Gulf of Bothnia

Abstract. In order to forecast consequences of climatic changes for littoral algae in coastal ecosystems, the effects of temperature increase on spring bloom dynamics of epilithic diatom communities were studied in two ways: (1) Communities were compared from sites receiving different amounts of cooling water discharge from a nuclear power plant. (2) Communities from the exceptionally warm spring of 1989 were compared with those from the same sites in the preceding normal years. The studies were carried out in and around the Forsmark Biotest Basin, an artificial waterbody that receives brackish cooling water from the Forsmark nuclear power plant on the Swedish east coast. Species composition and biomass data from 200 epilithic diatom samples taken in the period January-May from 1983 to 1989 were analysed. Multiple regression analysis was used to show the responses of diatom cover, community diversity and abundances of individual taxa to water temperature and other environmental factors. Constrained ordination (CCA) was used to display the relationship of overall community composition to environment. Increased water temperature resulted in higher biomass through a chain of ecological effects. Strong reduction of ice cover was crucial in this chain, resulting in reduced loss of diatom cells by reduced abrading and higher primary production by higher availability of light, nutrients and substrate. The conclusion is that large blooms of fast-growing epilithic diatoms in large colonies can occupy the niche that emerges when the ice-free season is prolonged in the northern Baltic Sea and areas similar in salinity and climatic conditions. Dramatic species shifts may only be expected if the winter ice cover is totally absent.     

Integrating spatial data and shorebird nesting locations to predict the potential future impact of global warming on coastal habitats: A case study on Farasan Islands,Saudi Arabia

One of the expected effects of the global warming is changing coastal habitats by accelerating the rate of sea level rise. Coastal habitats support large number of marine and wetland species including shorebirds (plovers, sandpipers and allies). In this study, we investigate how coastal habitats may be impacted by sea level rise in the Farasan Islands, Kingdom of Saudi Arabia. We use Kentish plover Charadrius alexandrinus – a common coastal breeding shorebird – as an ecological model species to predict the influence of sea level rise. We found that any rise of sea level is likely to inundate 11% of Kentish plover nests. In addition, 5% of the coastal areas of Farasan Islands, which support 26% of Kentish plover nests, will be flooded, if sea level rises by one metre. Our results are constrained by the availability of data on both elevation and bird populations. Therefore, we recommend follow-up studies to model the impacts of sea level rise using different elevation scenarios, and the establishment of a monitoring programme for breeding shorebirds and seabirds in Farasan Islands to assess the impact of climate change on their populations.     

Temperature-related mortality in France, a comparison between regions with different climates from the perspective of global warming

This paper aims to explain the results of an observational population study that was carried out between 1991 and 1995 in six regions (departments) in France. The study was to assess the relationship between temperature and mortality in a few areas of France that offer widely varying climatic conditions and lifestyles, to determine their thermal optimum, defined as a 3 degrees C temperature band with the lowest mortality rate in each area, and then to compare the mortality rates from this baseline band with temperatures above and below the baseline. The study period was selected because it did not include extreme cold or hot events such as a heatwave. Data on daily deaths from each department were first used to examine the entire population and then to examine men, women, various age groups and various causes of death (respiratory disease, stroke, ischaemic heart disease, other disease of the circulatory system, and all other causes excluding violent deaths). Mean temperatures were provided by the National Weather Service. The results depicted an asymmetrical V- or U-shaped relationship between mortality and temperature, with a thermal optimum lower for the elderly, and generally lower for women than for men except in Paris. The relationship was also different depending on the cause of death. In all cases, more evidence was collected showing that cold weather was more deadly than hot weather, and it would now be interesting to enlarge the study to include years with cold spells and heatwaves. Furthermore, the results obtained could be of great use in estimating weather-related mortality as a consequence of future climate-change scenarios.     

气候变暖对长白山主要树种的潜在影响

应用LINKAGES模型对长白山自然保护区内主要树种在各斑块类型中对气候变化的潜在响应进行了模拟,模拟时选择了目前和未来变暖2种气候条件,对于目前气候状态,模型使用目前气象参数;而对于未来变暖气候,则按温度增加5℃,降水无明显变化作为模拟假设,温度的增加假定各月都相同,即各月均增加5度,模拟结果表明,对于高山岳桦林,气温变暖后岳桦依然扮演重要角色,但落叶松,云极,冷杉等目前这一林带的伴生树种,在气温上升后,其生物量均有较大辐度的增加,部分占据目前岳桦的位置,即目前下部的云冷杉林带有上移的趋势;对于亚高山云冷杉林,其优势种云杉和冷杉在气温变暖后,生物量有较大幅度的增加,落叶松虽有增加的趋势但幅度较小,即云杉和冷杉在未来气温变暖后依然是这一林带的优势种,但生长会加快,阔叶红松林的主要建群种在气温升高后,其生物量只有较小的增加,其它主要伴生种的生物量随气温上升的增加趋势非常相似,表明阔叶红松林在未来气候变暖情况下仍将维持目前的结构状态。     

Experimental evidence of gradual size‐dependent shifts in body size and growth of fish in response to warming

A challenge facing ecologists trying to predict responses to climate change is the few recent analogous conditions to use for comparison. For example, negative relationships between ectotherm body size and temperature are common both across natural thermal gradients and in small‐scale experiments. However, it is unknown if short‐term body size responses are representative of long‐term responses. Moreover, to understand population responses to warming, we must recognize that individual responses to temperature may vary over ontogeny. To enable predictions of how climate warming may affect natural populations, we therefore ask how body size and growth may shift in response to increased temperature over life history, and whether short‐ and long‐term growth responses differ. We addressed these questions using a unique setup with multidecadal artificial heating of an enclosed coastal bay in the Baltic Sea and an adjacent reference area (both with unexploited populations), using before‐after control‐impact paired time‐series analyses. We assembled individual growth trajectories of ~13,000 unique individuals of Eurasian perch and found that body growth increased substantially after warming, but the extent depended on body size: Only among small‐bodied perch did growth increase with temperature. Moreover, the strength of this response gradually increased over the 24 year warming period. Our study offers a unique example of how warming can affect fish populations over multiple generations, resulting in gradual changes in body growth, varying as organisms develop. Although increased juvenile growth rates are in line with predictions of the temperature–size rule, the fact that a larger body size at age was maintained over life history contrasts to that same rule. Because the artificially heated area is a contemporary system mimicking a warmer sea, our findings can aid predictions of fish responses to further warming, taking into account that growth responses may vary both over an individual's life history and over time.     

Growth and reproduction of Antarctic vascular plants in response to warming and UV radiation reductions in the field

Along the west coast of the Antarctic Peninsula springtime ozone depletion events can lead to a two-fold increase in biologically effective UV-B radiation (UV-B_BE) and summer air temperatures have risen ≈1.5°C during the past 50 years. We manipulated levels of UV radiation and temperature around Colobanthus quitensis (a cushion-forming plant, Caryophyllaceae) and Deschampsia antarctica (a tussock grass) along the Peninsula near Palmer Station for two field seasons. Ambient levels of UV were manipulated by placing filters that either transmitted UV (filter control), absorbed UV-B (reducing diurnal levels of UV-B_BE by about 82%), or absorbed both UV-B and UV-A (reducing UV-B_BE and UV-A_BE by about 88 and 78%, respectively) on frames over naturally growing plants from November to March. Half the filters of each material completely surrounded the frames and raised diurnal and diel air temperatures around plants by an average of 2.3°C and 1.3°C, respectively. Reducing UV or warming had no effect on leaf concentrations of soluble UV-B absorbing compounds, UV-B absorbing surface waxes or chlorophylls. Warming had few effects on growth of either species over the first season. However, over the second field season warming improved growth of C. quitensis, leading to a 50% increase in leaf production (P < 0.10), a 26% increase in shoot production, and a 6% increase in foliar cover. In contrast, warming reduced growth of D. antarctica, leading to a 20% decline in leaf length, a 17% decline in leaf production (P < 0.10), and a 5% decline in foliar cover. Warming improved sexual reproduction in both species, primarily through faster development of reproductive structures and greater production of heavier seeds. Over the second field season, the percentage of reproductive structures that had reached the most developed (seed) stage in C. quitensis and D. antarctica was 20% and 15% higher, respectively, under warming. Capsules of C. quitensis produced 45% more seeds under warming and these seeds were 11% heavier. Growth of D. antarctica was improved when UV was reduced and these effects appeared to be cumulative over field seasons. Over the second season, tillers produced 55% more leaves and these leaves were 32% longer when UV-B was reduced. Tillers produced 137% more leaves that were 67% longer when both UV-B and UV-A were reduced. The effects of UV reduction were not as pronounced on C. quitensis, although over the second season cushions tended to be 17% larger and produce 21% more branches when UV-B was reduced, and tended to be 27% larger and produce 38% more branches when both UV-B and UV-A were reduced (P < 0.10). Few interactions were found between UV reduction and warming, although in the absence of warming, reducing UV led to slower development of reproductive structures in both species. The effects of warming and UV reduction were species specific and were often cumulative over the two field seasons, emphasizing the importance of long-term field manipulations in predicting the impacts of climate change. Received: 4 August 1998 / Accepted: 1 December 1998     

Impacts of warming and fertilization on nitrogen-fixing microbial communities in the Canadian High Arctic

The impacts of simulated climate change (warming and fertilization treatments) on diazotroph community structure and activity were investigated at Alexandra Fiord, Ellesmere Island, Canada. Open Top Chambers, which increased growing season temperatures by 1-3 degrees C, were randomly placed in a dwarf-shrub and cushion-plant dominated mesic tundra site in 1995. In 2000 and 2001 20N:20P2O5:20K2O fertilizer was applied at a rate of 5 gm(-2) year(-1). Estimates of nitrogen fixation rates were made in the field by acetylene reduction assays (ARA). Higher rates of N fixation were observed 19-35 days post-fertilization but were otherwise unaffected by treatments. However, moss cover was significantly positively associated with ARA rate. NifH gene variants were amplified from bulk soil DNA and analyzed by terminal restriction fragment length polymorphism analysis. Non-metric multidimensional scaling was used to ordinate treatment plots in nifH genotype space. NifH gene communities were more strongly structured by the warming treatment late in the growing season, suggesting that an annual succession in diazotroph community composition occurs.     

Culturable root endophyte communities are shaped by both warming and plant host identity in the Rocky Mountains,USA

Understanding the biogeographic patterns of root-associated fungi and their sensitivity to temperature may improve predictions of future changes in terrestrial biodiversity and associated ecosystem processes, but data are currently limited. Anticipating change will require combining observational data, which predict how climatic factors limit current species distributions, with direct manipulations of climate, which can isolate responses to specific climate variables. Root endophytes are common symbionts of plants, particularly in arctic and alpine environments, yet their responses to climate warming are not resolved. Here, we directly cultured endophytic fungi from roots collected along altitudinal gradients in replicated mountain watersheds and from a 27 y field warming experiment in the Rocky Mountains, USA, to improve understanding of climate impacts on fungal root endophytes. Fungal taxa that were common at high elevations declined most under climate warming, whereas low elevation dominants responded neutrally or increased with experimental warming. Altitudinal gradients in fungal communities were strongly specific to the plant host species. Specifically, Poa species had 25–60% greater fungal isolate abundance and 25–38% greater fungal diversity at high elevations than at low elevation sites. In contrast, Festuca thurberi had 64% lower fungal diversity on roots at high elevation than at low elevation. Our results help to improve understanding of the potential for climate change to alter plant-fungal interactions in mountain ecosystems.     

Change and stasis in marine hybrid zones in response to climate warming

Aim We test the prediction that hybrid zones between warm‐ and cold‐adapted species will move towards the territory formerly occupied by the cold‐adapted species in response to a warming climate. We use multiple tests of this prediction to distinguish amongst potential mechanistic hypotheses of responses to climate change. Location We sampled 97 locations on the Atlantic coast of Spain and France and the English Channel that span three hybrid zones formed between two species of marine mussels (Mytilus galloprovincialis and M. edulis). Methods Mussels were sampled in 2005–07 and analysed at a nuclear gene (Glu‐5′) that is diagnostically differentiated between the subject species. Results were compared to those of studies made in the same region over the past two decades. Historical change in sea surface temperature (SST) was analysed using National Oceanic and Atmospheric Administration (NOAA) Optimum Interpolation Daily SST. Species distribution models (random forest and maximum entropy) of the current distribution of mussels were constructed and validated by hindcasting the historical distributions of these species. Validated models were used in combination with forecasts of SST to predict changes in mussel distribution to 2050 and 2100. Results We show that over the past two decades two of the hybrid zones in France have not changed in either position or shape. The third hybrid zone, however, has shifted in the predicted direction, c. 100 km eastward into the warming English Channel. Species distribution modelling strongly implicates changes in winter cold SST as driving this change in the position of one of the hybrid zones. Forecasts of future SST indicate that rapid changes in distribution will occur over the next century. Main conclusions Hybrid zones can be used to conduct repeated tests of ecological responses to climate change and can be valuable in sorting among prospective mechanistic hypotheses that underlie that change. Winter temperatures, but not seasonal high temperature, appear to control the distribution of both species. Species distribution modelling indicates that the collapse of these hybrid zones is imminent, with the rapid expansion of the subtropical species in response to continuing SST warming.     

Ecosystem respiration responses to experimental manipulations of winter and summer precipitation in a Mixedgrass Prairie,WY, USA

Changes in timing or amount of precipitation may be of great consequence for carbon cycling in the Mixedgrass Prairie of N. America, because CO₂ fixation and efflux are tightly coupled to soil water properties. The objective of our project was to quantify how ecosystem respiration (R_e) responds to experimental changes in winter and summer precipitation in a Mixedgrass Prairie using in situ field manipulations of snow depth and summer rain. Our study was conducted at the USDA-ARS High Plains Grasslands Research Station, west of Cheyenne, Wyoming. We installed three replicated 50 m snow fences to increase winter snow on the leeward side of the snow fence and experimentally manipulated summer precipitation by either increasing (+50%) or decreasing (−50%) precipitation amounts. We also measured ambient conditions. R_e rates in May were around 2 g C m⁻² d⁻¹ for all treatments and increased to their greatest values in June, up to 10 g C m⁻² d⁻¹, with the ambient treatment having the largest flux rates. There were no treatment effects during the early summer, but by midsummer, R_e rates were least in the reduced rainfall plots and greatest in the snow plots. Soil moisture and gross photosynthesis had strong influence on the daily R_e rates, but soil temperature had little correlation with daily R_e rates. In summary, the R_e rates in this Mixedgrass Prairie are strongly influenced by changes in precipitation, especially winter snow accumulation. Thus, carbon cycle estimates under future climate change scenarios need to include not only the affects of changes in summer rain, but also, the consequences of deep snow in winter and itsȁ9 affect on carbon cycling processes in winter and subsequent summers.     

Effects of constant and fluctuating incubation temperatures on hatching success and hatchling traits in the diamondback terrapin (Malaclemys terrapin) in the context of the warming climate

As global temperatures continue to rise, so too will the nest temperatures of many species of turtles. Yet for most turtle species, including the estuarine diamondback terrapin (Malaclemys terrapin), there is limited information on embryonic sensitivity to elevated temperature. We incubated eggs of M. terrapin at three, mean temperatures (31, 34, 37 °C) under two thermal exposure regimes (constant or semi-naturally fluctuating temperature) and measured hatching success, developmental rate, and hatchling size. Hatching success was 100% at 31 °C and 67% at 34 °C, respectively; at 37 °C, all eggs failed early in the incubation period. These values were unaffected by exposure regime. The modeled LT₅₀ (temperature that was lethal to 50% of the test population) was 34.0 °C in the constant and 34.2 °C in the fluctuating thermal regime, reflecting a steep decline in survival between 33 and 35 °C. Hatchlings having been incubated at a constant 34 °C hatched sooner than those incubated at 31 °C under either constant or fluctuating temperature. Hatchlings were smaller in straight carapace length (CL) and width after having been incubated at 34 °C compared to 31 °C. Larger (CL) hatchlings resulted from fluctuating temperature conditions relative to constant temperature conditions, regardless of mean temperature. Based upon recent temperatures in natural nests, the M. terrapin population studied here appears to possess resiliency to several degrees of elevated mean nest temperatures, beyond which, embryonic mortality will likely sharply increase. When considered within the mosaic of challenges that Maryland's M. terrapin face as the climate warms, including ongoing habitat losses due to sea level rise and impending thermal impacts on bioenergetics and offspring sex ratios, a future increase in embryonic mortality could be a critical factor for a population already experiencing ecological and physiological challenges due to climate change.     

Contrasting effects of summer and winter warming on body mass explain population dynamics in a food‐limited Arctic herbivore

The cumulative effects of climate warming on herbivore vital rates and population dynamics are hard to predict, given that the expected effects differ between seasons. In the Arctic, warmer summers enhance plant growth which should lead to heavier and more fertile individuals in the autumn. Conversely, warm spells in winter with rainfall (rain‐on‐snow) can cause ‘icing’, restricting access to forage, resulting in starvation, lower survival and fecundity. As body condition is a ‘barometer’ of energy demands relative to energy intake, we explored the causes and consequences of variation in body mass of wild female Svalbard reindeer (Rangifer tarandus platyrhynchus) from 1994 to 2015, a period of marked climate warming. Late winter (April) body mass explained 88% of the between‐year variation in population growth rate, because it strongly influenced reproductive loss, and hence subsequent fecundity (92%), as well as survival (94%) and recruitment (93%). Autumn (October) body mass affected ovulation rates but did not affect fecundity. April body mass showed no long‐term trend (coefficient of variation, CV = 8.8%) and was higher following warm autumn (October) weather, reflecting delays in winter onset, but most strongly, and negatively, related to ‘rain‐on‐snow’ events. October body mass (CV = 2.5%) increased over the study due to higher plant productivity in the increasingly warm summers. Density‐dependent mass change suggested competition for resources in both winter and summer but was less pronounced in recent years, despite an increasing population size. While continued climate warming is expected to increase the carrying capacity of the high Arctic tundra, it is also likely to cause more frequent icing events. Our analyses suggest that these contrasting effects may cause larger seasonal fluctuations in body mass and vital rates. Overall our findings provide an important ‘missing’ mechanistic link in the current understanding of the population biology of a keystone species in a rapidly warming Arctic.     

Growth of 19 conifer species is highly sensitive to winter warming,spring frost and summer drought

Background and AimsConifers are key components of many temperate and boreal forests and are important for forestry, but species differences in stem growth responses to climate are still poorly understood and may hinder effective management of these forests in a warmer and drier future.MethodsWe studied 19 Northern Hemisphere conifer species planted in a 50-year-old common garden experiment in the Netherlands to (1) assess the effect of temporal dynamics in climate on stem growth, (2) test for a possible positive relationship between the growth potential and climatic growth sensitivity across species, and (3) evaluate the extent to which stem growth is controlled by phylogeny.Key resultsEighty-nine per cent of the species showed a significant reduction in stem growth to summer drought, 37 % responded negatively to spring frost and 32 % responded positively to higher winter temperatures. Species differed largely in their growth sensitivity to climatic variation and showed, for example, a four-fold difference in growth reduction to summer drought. Remarkably, we did not find a positive relationship between productivity and climatic sensitivity, but instead observed that some species combined a low growth sensitivity to summer drought with high growth potential. Both growth sensitivity to climate and growth potential were partly phylogenetically controlled.ConclusionsA warmer and drier future climate is likely to reduce the productivity of most conifer species. We did not find a relationship between growth potential and growth sensitivity to climate; instead, some species combined high growth potential with low sensitivity to summer drought. This may help forest managers to select productive species that are able to cope with a warmer and drier future.     

Longevity of animals under reactive oxygen species stress and disease susceptibility due to global warming

The world is projected to experience an approximate doubling of atmospheric CO_2 concentration in the next decades. Rise in atmospheric CO_2 level as one of the most important reasons is expected to contribute to raise the mean global temperature 1.4 ℃-5.8 ℃ by that time. A survey from 128 countries speculates that global warming is primarily due to increase in atmospheric CO_2 level that is produced mainly by anthropogenic activities. Exposure of animals to high environmental temperatures is mostly accompanied by unwanted acceleration of certain biochemical pathways in their cells. One of such examples is augmentation in generation of reactive oxygen species(ROS) and subsequent increase in oxidation of lipids, proteins and nucleic acids by ROS. Increase in oxidation of biomolecules leads to a state called as oxidative stress(OS). Finally, the increase in OS condition induces abnormality in physiology of animals under elevated temperature. Exposure of animals to rise in habitat temperature is found to boost the metabolism of animals and a very strong and positive correlation exists between metabolism and levels of ROS and OS. Continuous induction of OS is negatively correlated with survivability and longevity and positively correlated with ageing in animals. Thus, it can be predicted that continuous exposure of animals to acute or gradual rise in habitat temperature due to global warming may induce OS, reduced survivability and longevity in animals in general and poikilotherms in particular. A positive correlation between metabolism and temperature in general and altered O_2 consumption at elevated temperature in particular could also increase the risk of experiencing OS in homeotherms. Effects of global warming on longevity of animals through increased risk of protein misfolding and disease susceptibility due to OS as the cause or effects or both also cannot be ignored. Therefore, understanding the physiological impacts of global warming in relation to longevity of animals will become very crucial challenge to biologists of the present millennium.