Summer Water Research Articles

Some biological characteristics, habitat requirements and implications for conservation of endemic freshwater fish Capoeta aydinensis (Turan, Küçük, Kaya, Güçlü & Bektaş, 2017) in Tersakan stream (Muğla)

There have been increasing concerns about endemic species in recent years. Endemism is one of the major basic piece of continuing legacy of biodiversity. However, our knowledge on basic bio-ecological features and habitat requirements of many endemic freshwater fish species in Turkish inlands is highly limited. In this context it was conducted a yearlong study on Capoeta aydinensis (Turan, Küçük, Kaya, Güçlü & Bektaş, 2017) population, which occurs in Tersakan Stream in Dalaman (Muğla). The aim of present study is to reveal some bioecological features of C. aydinensis such as growth, reproduction and habitat use. As a result of the analyses, life span of C. aydinensis was found to be 8 years and showed relatively slow growth. It was estimated that female individuals reached maturity at 5th age and 234 mm total length while male individuals were at 4th age and 194 mm total length. As reproduction period, C. aydinensis spawn in spring season and reproductive activity continues during 3 months. It was analyzed that a mature female produced an average of 7833 eggs in total. Shady areas in spring, generally blurry waters in summer, high vegetation cover and blurry waters in autumn and high vegetation cover in winter were the habitat preferences. With this study, some major basic biologic and habitat information for management and conservation of endemic C. aydinensis were obtained and it is considered that this knowledge might be important for the future work.

THORNTHWAITE’S CLIMATE REGIONALIZATION FOR THE STATE OF TOCANTINS, BRAZIL

Tocantins State faces a large-scale agricultural expansion. Thus, climate studies are essential for a better understanding of climate variability supporting agricultural and environmental planning. In this context, this study applies the climatic classification of Thornthwaite and develops a climate regionalization through geostatistical techniques, assessing the performance of the interpolators ordinary kriging (OK) and cokriging (CK). Data from 26 weather stations located in Tocantins State and surroundings were used. The variables of interest to climate regionalization, obtained by the climatic water balance, were mapped by geostatistical techniques. The results of cross-validation showed that ordinary kriging and cokriging performed well. The spherical and exponential semivariogram models obtained the best fit in 40% of the analyzes each, and the gaussian in 20%. The climatic classification of Thornthwaite applied to Tocantins State showed the presence of humid (B1), moist subhumid (C2), and dry subhumid (C1) climates. There were found three climatic regions: B1A’wa’: Humid, megathermal, with moderate winter water deficiency, and a temperature efficiency regime normal to megathermal , occurring in the western region of the state; C2A’wa’: Moist subhumid, megathermal, with moderate winter water deficiency, and a temperature efficiency regime normal to megathermal , occurring in the central region and extending from the north to the south of the state; and C1A’w2a’: Dry subhumid, megathermal, with large summer water surplus, and a temperature efficiency regime normal to megathermal , in the east and northeast of the state.

Seasonal and Scale Effects of Anthropogenic Pressures on Water Quality and Ecological Integrity: A Study in the Sabor River Basin (NE Portugal) Using Partial Least Squares-Path Modeling

Interactions between pollution sources, water contamination, and ecological integrity are complex phenomena and hard to access. To comprehend this subject of study, it is crucial to use advanced statistical tools, which can unveil cause-effect relationships between pressure from surface waters, released contaminants, and damage to the ecological status. In this study, two partial least squares-path models (PLS-PM) were created and analyzed in order to understand how the cause-effect relationships can change over two seasons (summer and winter) and how the used scale (short or long) can affect the results. During the summer of 2016 and winter of 2017 surface water parameters and the North Invertebrate Portuguese Index were measured in strategic sampling sites. For each site, it two sections were delineated: the total upstream drainage area (long scale) and 250 m (short scale). For each section, data of pressures in surface waters including point source, diffuse emissions and landscape metrics were gathered. The methodology was applied to the Sabor River Basin, located in the northeast of Portugal. In this study, it was possible to determine in which season pressures affect ecological integrity and also which scale should be addressed. The models showed the influences of manganese and of potassium concentrations in stream water on the decrease in summer water quality, while arsenic’s harmful effect occurs during winter. Pastures and environmental land use conflicts were considered threats to water quality when analyzed on a long scale, whereas agricultural areas played a role when the short scale was used. The effect of landscape edge density revealed to be independent of scale or season. Effluent discharges in surface water affected the water quality during the summer season, while the effect of discharges in groundwater affected the water quality in winter. It has also been found that, to find the harmful effect of pressures, it is necessary to approach different scales and that the role of landscape metrics can also overlap contaminant sources.

Emergence of Summertime Hypoxia and Concurrent Carbonate Mineral Suppression in the Central Bohai Sea, China

AbstractThe Bohai Sea to the west of the North Yellow Sea in the Northwest Pacific is a semienclosed shallow‐water marginal sea on a critical path of eutrophication and environmental degradation. To better understand the Bohai Sea metabolism‐induced summertime dissolved oxygen (DO) decline and acidification, eight field surveys were conducted between August 2011 and September 2017, investigating seasonal and interannual variations in DO and carbonate system parameters in the central Bohai Sea. The historically lowest Bohai Sea DO was recorded at 66 μmol O2/kg in subsurface waters in early September 2015. By comparing our data set with literature data obtained in the 1980s, 1990s, and 2000s, the emergence history of summertime hypoxia in this marginal sea was shown. Associated with the seasonal DO shortage, the metabolism‐enhanced CO2 accumulation in subsurface waters in summer resulted in critical aragonite saturation states of close to or even less than 1.5, threatening calcifiers with potentially severe consequences for valuable shellfish fisheries. Based on model results combining the aerobic respiration (as indicated by apparent oxygen utilization) and the given wintertime/springtime atmospheric CO2 level of the time, this study suggests that combined stresses of the seasonal DO shortage and CO2 acidification capable of threatening Bohai Sea ecosystems could develop within decades.

Temperature-Dependent Bifurcated Seasonal Shift of Phytoplankton Community Composition in the Coastal Water off Southwestern Korea

Coastal water around the archipelago off southwestern Korea has been bathed in an unprecedented pool of warm water in summer in recent years. Here, we examined phytoplankton community responses to amplified seasonal temperature fluctuation around the archipelago based on chemotaxonomic analysis in association with physicochemical properties in the shallow coastal water from June 2016 to March 2018. Concentrations of dissolved inorganic nutrients were significantly higher during the warm season than during the cold season. Canonical correspondence analysis revealed that water temperature was a main driver controlling the phytoplankton community. Generalized additive models denoted that small phytoplankton groups (cryptophytes, cyanobacteria, and prasinophytes) were more resistant to high temperatures (> 25°C) compared with diatoms. Indeed, dominance of diatoms was significant (80%) during the cold season and sharply declined (to 49%) during the warm season. Small phytoplankton were dominant (62%) as the water temperature exceeded 22°C. Our results highlight the effects of temperature-dependent bifurcated seasonality on phytoplankton communities in coastal waters. Furthermore, unprecedentedly high summer temperatures in August 2016 coincided with a remarkable increase in the importance (∼70%) of small phytoplankton. Accumulating evidence provides indications regarding future scenarios: while small phytoplankton will probably account for summer blooms, diatom blooms will shift to winter.

Implication of evaporative loss estimation methods in discharge and water temperature modelling in cool temperate climates

AbstractEvaporative flux is a key component of hydrological budgets. Water loss through evapotranspiration reduces volumes available for run‐off. The transition from liquid to water vapour on open water surfaces requires heat. Consequently, evaporation act as a cooling mechanism during summer. Both river discharge and water temperature simulations are thus influenced by the methods used to model evaporation. In this paper, the impact of evapotranspiration estimation methods on simulated discharge is assessed using a semidistributed model on two Canadian watersheds. The impact of evaporation estimation methods on water temperature simulations is also evaluated. Finally, the validity of using the same formulation to simulate both of these processes is verified. Five well‐known evapotranspiration models and five evaporation models with different wind functions were tested. Results show a large disparity (18–22% of mean annual total evapotranspiration) among the evapotranspiration methods, leading to important differences in simulated discharge (3–25% of observed discharge). Larger differences result from evaporation estimation methods with mean annual divergences of 34–48%. This translates into a difference in mean summer water temperature of 1–15%. Results also show that the choice of model parameter has less influence than the choice of evapotranspiration method in discharge simulations. However, the parameter values influence thermal simulations in the same order of magnitude as the choice of evaporation estimation method. Overall, the results of this study suggest that evapotranspiration and open water evaporation should be represented separately in a hydrological modelling framework, especially when water temperature simulations are required.

Biotic and Abiotic Factors Affecting the Population Dynamics of Ceratium hirundinella, Peridinium cinctum, and Peridiniopsis elpatiewskyi

The present research was conducted to assess the impact of abiotic and biotic factors on the growth of freshwater dinoflagellates such as Ceratium hirundinella, Peridinium cinctum, and Peridiniopsis elpatiewskyi, which reduce the quality of drinking water in the Zayandeh Rud Reservoir. To this end, 152 algal and zoological samples were collected from the reservoir located in the Central part of Iran in January, April, July, and October 2011. Abiotic factors such as pH, temperature, conductivity, transparency, dissolved oxygen, and nutrient concentration of the water were measured in all study stations. The results showed that the population dynamics of dinoflagellates in the Zayandeh Rud Reservoir was different depending on season, station, and depth. The findings proved that C. hirundinella was one of the dominant autumn planktons in the highest biovolume in the Zayandeh Rud Reservoir. While P. elpatiewskyi was present in the reservoir throughout a year with biovolume peak in summer. Accompanying bloom of P. elpatiewskyi and C. hirundinella, P. cinctum also grew in well-heated summer and autumn waters. It was further found that Ceratium density was positively correlated with sulfate ion concentrations, while the growth of P. cinctum and P. elpatiewskyi were associated, first and foremost, with NO2− and Mn.

Modelling the impacts of climate change on riverine thermal regimes in western Canada\u2019s largest Pacific watershed

Quantification of climate change impacts on the thermal regimes of rivers in British Columbia (BC) is crucial given their importance to aquatic ecosystems. Using the Air2Stream model, we investigate the impact of both air temperature and streamflow changes on river water temperatures from 1950 to 2015 across BC’s 234,000 km2 Fraser River Basin (FRB). Model results show the FRB’s summer water temperatures rose by nearly 1.0 °C during 1950–2015 with 0.47 °C spread across 17 river sites. For most of these sites, such increases in average summer water temperature have doubled the number of days exceeding 20 °C, the water temperature that, if exceeded, potentially increases the physiological stress of salmon during migration. Furthermore, river sites, especially those in the upper and middle FRB, show significant associations between Pacific Ocean teleconnections and regional water temperatures. A multivariate linear regression analysis reveals that air temperature primarily controls simulated water temperatures in the FRB by capturing ~80% of its explained variance with secondary impacts through river discharge. Given such increases in river water temperature, salmon returning to spawn in the Fraser River and its tributaries are facing continued and increasing physical challenges now and potentially into the future.

Investigation of Legacy Methane Seepage into Freshwater Food Webs Using Novel Applications in Stoney Creek, New Brunswick

Legacy oil, gas, and coalfields in the Maritime region have emitted methane into the surrounding ecosystem for more than 100 years. Methane escaping from these legacy sites may have effects on the surrounding terrestrial and aquatic environments. I investigated whether methane could be detected entering streams via groundwater inputs in an area with abandoned and active oil and gas wells. Introduction of a foreign compound, such as methane, could act as an environmental stressor and could impact the local food web starting at the lowest trophic level. I predicted that if methane was entering freshwater streams and being incorporated into the food web, it would be evident in the stable isotopes of consumers and prey. Methane would have a distinct isotopic carbon signature and could be traced through the various biotic compartments. This project focuses on the novel application of using a small thermal imaging camera to help detect subsurface groundwater inputs into the stream for site selection. Using this temperature sensing technology, I found and selected 5 suspected groundwater sources flowing into the stream channel. I collected biofilm (e.g. bacteria, algae, diatoms) and benthic macroinvertebrate from both upstream and downstream of each suspected groundwater input site. With small streams and low summer water levels, I was unable to adequately sample the fish community. Stable isotope analysis of biofilm and benthic macroinvertebrates did not show obvious incorporation of methane into the food web, though some values were suspect. Additionally, I completed a diatom community assessment applying the Eastern Canadian Diatom Index (IDEC) as a measure of the biological integrity of streams and were able to show that the study sites in the Stoney Creek region are currently considered “slightly polluted”, with a few select locations bordering on “polluted”. Although these techniques and tools did show the incorporation of methane in the food web at Stoney Creek, the combination of inexpensive tools can be employed in the investigation of methane at other sites. This study serves as an exploration and application of tools and techniques that have not previously been applied in this context.

Impacts of Multiple Environmental Change Drivers on Growth of European Beech (Fagus sylvatica): Forest History Matters

Revealing the interactive effects of multiple environmental change drivers (water deficits, nitrogen (N) deposition, land-use change) is crucial for evaluating actual and possible future changes in forest ecosystem functioning. Here, we analyse whether and to what extent combined effects of spring and summer water deficits and variable amounts of N deposition affect radial growth of beech trees growing on forest sites with a different forest history. Dendrochronological data showed that trees growing on ancient forest sites (forest continuity > 200 years) exhibit a higher negative growth response under high N deposition and simultaneous spring water deficits than trees growing on recent (post-agricultural) forest sites. Based on additional analyses of the fine root system and masting behaviour, we propose two different mechanisms to explain differing influences of N deposition and water deficits on negative radial growth responses in recent and ancient forests: (1) for both forest history types, growth reductions during summer water deficits result from the antagonistic effects of elevated N deposition according to the ‘resource optimization hypothesis’. The tendency towards higher negative growth responses in recent forests seems to be caused by a higher fine root mortality and lower standing fine root biomass compared to ancient forests; (2) higher growth reductions in ancient forests during spring water deficits are likely the result of mass fructification, which is enhanced by N deposition. We conclude that nutrient cycling may differ between forests with contrasting forest history, which can modulate the growth trajectories of forests in response to multiple, co-occurring environmental changes.

Persistent establishment of a tropical disease in Europe: the preadaptation of schistosomes to overwinter

BackgroundGlobal changes promote the spread of infectious diseases worldwide. In this context, tropical urogenital schistosomiasis is now permanently established in Corsica since its first emergence in 2013. The local persistence of the tropical pathogens (schistosomes) responsible for urogenital schistosomiasis at such latitudes might be explained by (i) the presence of its intermediate host, the snail Bulinus truncatus, (ii) the recurrent local reseeding of schistosomes by their vertebrate hosts (either human or animal) every summer, and/or (iii) the maintenance and survival of schistosomes within their snail hosts over winter.MethodsIn this study we conducted an ecological experiment to assess the ability of temperate and tropical schistosome strains to survive in classical winter temperatures in Corsican rivers when infecting temperate (local) snail strains. We also quantified the ability of the schistosomes to complete their life-cycle post-overwintering when returned to classical summer water temperatures.ResultsOur results show that Mediterranean molluscs are locally adapted to winter conditions compared to tropical molluscs. Moreover, temperate and tropical schistosome strains equally survived the cold and produced viable offspring when returned to optimal temperatures. These results indicate that schistosomes can overwinter under temperate climates when infecting locally adapted snails and might partly explain the establishment and maintenance of schistosomes in Corsica from year to year.ConclusionsThe observed broader thermal range of schistosomes compared to that of their snail hosts was unexpected and clearly indicates that the spread and establishment of schistosomiasis in temperate countries relies primarily on the presence of the locally adapted snail host lineages, currently known to be present in France, Italy, Portugal, Spain and Greece.

Sea surface temperature dictates movement and habitat connectivity of Atlantic cod in a coastal fjord system.

While movements of organisms have been studied across a myriad of environments, information is often lacking regarding spatio‐seasonal patterning in complex temperate coastal systems. Highly mobile fish form an integral part of marine food webs providing linkages within and among habitats, between patches of habitats, and at different life stages. We investigated how movement, activity, and connectivity patterns of Atlantic cod (Gadus morhua) are influenced by dynamic environmental conditions. Movement patterns of 39 juvenile and subadult Atlantic cod were assessed in two coastal sites in the Swedish Skagerrak for 5 months. We used passive acoustic telemetry and network analysis to assess seasonal and spatial movement patterns of cod and their relationships to different environmental factors, using statistical correlations, analysis of recurrent spatial motifs, and generalized linear mixed models. Temperature, in combination with physical barriers, precludes significant connectivity (complex motifs) within the system. Sea surface temperature had a strong influence on connectivity (node strength, degree, and motif frequency), where changes from warmer summer waters to colder winter waters significantly reduced movement activity of fish. As the seasons changed, movement of fish gradually decreased from large‐scale (km) linkages in the summer to more localized movement patterns in the winter (limited to 100s m). Certain localized areas, however, were identified as important for connectivity throughout the whole study period, likely due to these multiple‐habitat areas fulfilling functions required for foraging and shelter. This study provides new knowledge regarding inshore movement dynamics of juvenile and subadult Atlantic cod that use complex, coastal fjord systems. The findings show that connectivity, seasonal patterns in particular, should be carefully considered when selecting conservation areas to promote marine stewardship.

Modelling historical and potential future climate impacts on Keremeos Creek, an Okanagan-Similkameen watershed, British Columbia, Canada: Part I. Forecasting change in spring and summer water supply and demand

The current study is Part I of a two-part assessment of climate change impacts on hydrology and farm-level Greenhouse Gas (GHG) emissions. The effects of climate change on spring and summer water supply and spring and summer water demand related to the vegetation cover in the Keremeos Creek watershed in the Regional District of Okanagan-Similkameen (RDOS), southern British Columbia, Canada in the time-frame of 1961 to 2100 are investigated in Part I. The GENerate Earth SYstems Science input (GENESYS) spatial hydro-meteorological model is applied to predict the potential changes for the ensemble averages of 15 General Circulation Models (GCMs) for two Representative Concentration Pathways (RCP) scenarios (RCP 4.5 and RCP 8.5) in the 2020’s (2011–2040), 2050’s (2041–2070), and 2080’s (2071–2100) relative to the 1961–1990 base period. Timing of snowmelt may be expected to occur one month earlier in all projected periods with RCP 4.5 and 8.5 except RCP 8.5 in the 2080’s, which may be 2 months earlier relative to the 1961–1990 period. Based on predictions, there may be increases in total spring water supply from 35% to 39% and decreases in summer water supply from 36% to 79% relative to the 1961–1990, based on the three projected periods with RCP 4.5 and 8.5. Average spring vegetation water demand may increase from 20% to 47% but summer vegetation water demand may decrease from 10% to 29% relative to the 1961–1990 period based on the projected periods and emission scenarios. The spring and summer evapotranspiration estimates were controlled by the surface energy and soil moisture availability, respectively. These changes are expected to put stress on the future water resources management in the watershed. The results of Part I are then applied to Part II to estimate changes in farm-level GHG emissions and soil carbon storage.

Phytoplankton communities and size-fractioned chlorophyll a in newly opened summer waters of the central Arctic Ocean

Phytoplankton communities and size-fractioned chlorophyll a in newly opened summer waters of the central Arctic Ocean

Effects of water temperature and pikeperch (Sander lucioperca) abundance on the stock\u2013recruitment relationship of Eurasian perch (Perca fluviatilis) in the northern Baltic Sea

How spawning stock size, environmental conditions and recruitment relate to each other is an essential question in understanding population dynamics of exploited fish stocks. We estimated the recruitment of Eurasian perch (Perca fluviatilis), one of the most important species in coastal fisheries in northern Baltic Sea, and examined the factors that determine perch recruitment success. We hypothesized that perch spawning population biomass and summer water temperature would increase perch recruitment, with potential density dependence, while the effect of the population size of pikeperch (Sander lucioperca) would be negative. Different forms of general stock–recruitment functions, with and without density dependence, and with and without water temperature and pikeperch population size as environmental factors were fitted to long-term (1981–2014) stock assessment data of perch and pikeperch in the Archipelago Sea, southwestern coast of Finland. Perch spawning stock biomass (ages 5–14), water temperature in June–July and pikeperch stock size (ages ≥ 1) at spawning year best explained variation in perch recruitment. The results supported the predictions: perch recruitment increased with spawning stock in density-dependent manner, pikeperch effect on perch recruitment was negative and summer temperature effect was positive suggesting environmentally affected competitive interaction between these two percids.

The Distribution and Prediction of Summer Near-Surface Water Temperatures in Lakes of the Coterminous United States and Southern Canada

The goals of the study were: (i) To describe the distribution of summer near-surface water temperatures in lakes of the coterminous United States and southern Canada (ii) to determine the geographic, meteorological and limnological factors related to summer water temperatures and (iii) to develop and test predictive models for summer near-surface water temperatures. We used data from the United States National Lakes Assessments of 2007 and 2012 as well as data collected from several different studies of Canadian lakes. Using multiple regressions, we quantified the general observations that summer water temperatures decreased when going from south to north, from east to west, and from lower elevations to higher elevations. Our empirical model using 8-day average air temperatures, latitude, longitude, elevations and month was able to predict water temperatures in individual lakes on individual summer days with a standard deviation of 1.7 °C for United States lakes and 2.3 °C for lakes in the southern regions of Canada.

Using δ18O as a Tracer of the Formation of Water Masses in the Laptev Sea. Part 2. Quantification of the Volume of Atlantic, River, and Melt Water as well as Water Withdrawn for Ice Formation

The main characteristics of water masses in the Laptev Sea formed as a result of the mixing of Atlantic and river water and transformed as a result of ice formation and ice melting were revealed using the conservative isotopic parameter δ18O as a tracer. The amount of Atlantic, river, and melt water as well as the volumes of water withdrawn for ice formation are quantified for six water masses typical of the Laptev Sea. Both melt and transformed (as a result of ice formation) water types are present in the surface river water mass. The prevalence of melt water is observed in the range of sea water salinity from 0 to 7–8 psu. The maximum content of melt water in this salinity range can reach 40%, and the desalination resulting from ice melting reaches 0.2–0.7 psu. The areas with the maximum water removal for ice formation are linked to the position of summer and winter water of the Laptev Sea, in the area of the Anabar-Lena, East Taymyr, West New Siberian, and North New Siberian flaw polynyas and fast ice in the southeastern part of the sea. In these regions water removal for ice formation makes up 10 to 20% and is observed from the surface to the bottom even during the summer-autumn period. Atlantic water is characterized not only by mixing with river water from Siberian rivers but also by transformations resulting from ice formation. However, this effect is largely associated with the convective mixing with overlying layers where ice formation occurs. Mean temperature of the bottom layers of Arctic basin water is by 2.2°C lower than the mean temperature of Atlantic water, and mean salinity is by ~0.06 psu higher. In this water the presence of river water as well as the influence of ice formation and ice melting mass are less pronounced as compared to Atlantic water.

Convictfish on the move: variation in growth and trophic niche space along a latitudinal gradient

Abstract The range expansion of tropical fish into temperate waters is increasing markedly in response to climate change. Range-expanding fish encounter novel diets and environments, but we know little about how these conditions facilitate or hinder distribution shifts. Here, we quantified relative growth rate, morphometric condition and trophic niche of juvenile Acanthurus triostegus, a dominant range-expanding tropical surgeonfish, at four locations across 10° of latitude off eastern Australia. We related these metrics to differences in temperature and nutritional quality of dominant seaweeds and the epilithic algal matrix. Temperate food sources were richer in nitrogen than tropical diets. Stable isotope analysis (δ13 carbon and δ15 nitrogen) of fish muscle revealed a large trophic niche breadth at the highest latitude indicating a generalist foraging strategy, and more nitrogen-enriched isotopic signatures compared to tropical regions. Fish length was strongly correlated to δ13C in all regions, suggesting an ontogenetic shift in diet independent of latitude. Despite temperature differences of 4°C, fish growth and body condition were similar across tropical and temperate regions. These results suggest that more nutritious temperate diets may compensate for the effects of cooler water temperatures. Neither summer water temperatures nor dietary factors appear to limit the success of juvenile tropical vagrants as they continue to expand their range along eastern Australia.

Water temperature drives variability in salmonfly abundance, emergence timing, and body size

AbstractFreshwater organisms are disproportionately impacted by climate change and human disturbance, resulting in shifts in species' distributions and life histories. We coupled contemporary and historical datasets documenting physical and ecological variables over four decades to quantify changes in the abundance, emergence timing, and body size of salmonflies (Pteronarcys californica) in the Madison River in southwest Montana. In contemporary surveys, water temperature was the main driver of salmonfly abundance, emergence timing, and body size. Salmonfly densities were negatively correlated with summer water temperature, which explained 60% of variation in larval density among sites, whereas substrate type played a negligible role. Emergence occurred 20 days earlier, and male and female exuvia length were 13.8% and 11.3% shorter, respectively, at the warmest site relative to the coolest site (4°C difference). These patterns were supported by historical data. For example, a 1.2°C increase in mean annual water temperature in the Madison River between 1977 and 2017 coincided with evidence for upstream range contraction. Between 1973 and 2017, emergence timing varied widely among years, occurring up to 41 days earlier in years when spring water temperatures were relatively warm. As climate change progresses, we predict that salmonflies could be extirpated from an additional 28 km of currently occupied habitat, representing a 22.6% reduction in suitable habitat along the Madison River. This study provides evidence of long‐term biological change of an aquatic insect and highlights the importance of combining spatial and historical datasets to better understand species' responses to environmental stressors across both space and time.

Low Subsurface Water Storage Capacity Relative to Annual Rainfall Decouples Mediterranean Plant Productivity and Water Use From Rainfall Variability

AbstractPlant water stress in response to rainfall variability is mediated by subsurface water storage, yet the controls on stored plant‐available water remain poorly understood. Here we develop a probabilistic water balance model for Mediterranean climates that relates the amount of water stored over the wet season to annual rainfall statistics and subsurface storage capacity in soil and weathered bedrock. This model predicts that low storage capacity—relative to winter rainfall—results in similar year‐to‐year summer water availability, as both relatively wet and dry winters replenish storage. Observed water balances in seven catchments in the Northern California Coast Ranges exhibited this dynamic. We hypothesized that plants would be decoupled from precipitation variability at these storage‐capacity‐limited sites and observed that summer productivity and water use (inferred from the enhanced vegetation index) were independent of winter rainfall totals. These areas emerged largely unscathed from recent extreme drought, despite widespread plant mortality elsewhere.