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This paper summarises key issues from papers included in a special issue about the impacts of climate change on Australian wetlands. The papers covered: the assessment of wetlands under climate change, adaptation and engineering responses to climate change, and restoring wetlands under a changing climate. The key issues from these papers were used to indicate areas where the Ramsar Convention could develop guidance as part of its' Handbooks for the Wise Use of Wetlands. These included: (i) assessing changes in the distribution of species and whether these constitute a change in the ecological character of the wetland; (ii) assessing the usefulness of models of wetland response to climate change; (iii) assessing the value in allocating water to protected sites where restoration would be contingent on reallocation of larger volumes of water; (iv) assessing the efficacy of engineering responses with the potential to deliver more water-efficient environmental outcomes for wetlands and (v) determining if the description of the ecological character of a Ramsar site at the time of listing is a suitable reference for management purposes. With these issues in mind it is recommended that further attention is directed towards determining and responding to the ecological consequences of climate change. [ABSTRACT FROM AUTHOR]

Research on climate change, water quality, and their relationship is critical for human survival and development. It can help better mitigate climate change and contribute to appropriate water quality management strategies under uncertain challenges in the future. In this study, bibliometric analysis was used to provide a comprehensive review of the research field of climate change and water quality from 1990 to 2022. The extraction of documents was carried out from the Web of Science Core Collection database. VOSviewer, Bibliometrix R-package, and CiteSpace were used for analysis and scientific mapping. The results show that China, the United States, and Canada are the main countries driving this field, and China and the United States closely cooperate. It was also found that the areas of water eutrophication and climate change research had a close relationship and were the current research hotspots. Finally, it is revealed that the areas of sustainable development of climate change and water quality management, model simulation and method improvement between climate change and water quality, groundwater quality risk assessment driven by climate change, the impact of water on climate change, and expanding the research scale of the relationship between climate change and water quality will be the future research trends in this field. [ABSTRACT FROM AUTHOR]

Concerted mangrove research and rehabilitation efforts over the last several decades have prompted a better understanding of the important ecosystem attributes worthy of protection and a better conservation ethic toward mangrove wetlands globally. While mangroves continue to be degraded and lost in specific regions, conservation initiatives, rehabilitation efforts, natural regeneration, and climate range expansion have promoted gains in other areas, ultimately serving to curb the high mangrove habitat loss statistics from the doom and gloom of the 1980s. We highlight those trends in this article and introduce this special issue of Hydrobiologia dedicated to the important and recurring Mangrove and Macrobenthos Meeting. This collection of papers represents studies presented at the fourth such meeting (MMM4) held in St. Augustine, Florida, USA, on July 18-22, 2016. Our intent is to provide a balanced message about the global state of mangrove wetlands by describing recent reductions in net mangrove area losses and highlighting primary research studies presented at MMM4 through a collection of papers. These papers serve not only to highlight on-going global research advancements, but also provide an overview of the vast amount of data on mangrove ecosystem ecology, biology and rehabilitation that emphasizes the uniqueness of the mangrove community. [ABSTRACT FROM AUTHOR]

The seasonal dynamics and spatial variability of macroinvertebrate assemblages in Alpine streams are becoming better understood. However, the implications of this knowledge for indices used in monitoring programs have yet to be fully considered. Establishing the ecological status of such streams using macroinvertebrates may then be difficult if what is expected to be found, and where, varies across small distances between streams at a given altitude, or between years in response to different climatic characteristics. In this paper, we evaluated the degree of spatial variability in macroinvertebrate abundance and diversity for 14 tributaries at similar altitude that feed a 6-km reach of an Alpine stream, and how this spatial variability differs within and between years. Environmental variables and macroinvertebrates were sampled on 10 dates for assessment. The data showed that differences in environmental characteristics over relatively short distances lead to between tributary differences in the "windows of opportunity" and hence when a tributary should be sampled for monitoring purposes. Superimposed on this spatial variability was inter-annual variability linked to climate differences that shifted this "window of opportunity" in time, and thus altered when monitoring was optimal for any one tributary in any one year. If biological indices are not rendered sensitivity to these variations, the results obtained may reflect more natural variability than possible human impacts. [ABSTRACT FROM AUTHOR]

The aim of this review is to introduce and critically comment the main research topics considered in a selection of papers on the European large perialpine lakes (LPL) presented at the XXXIII congress of the International Society of Limnology in 2016. Besides highlighting ongoing research advancements in the LPL, the review provides a critical overview of the scientific information available on the large lake’s ecosystems, identifying a few emerging research topics (e.g., aquatic ‘omics’ and high frequency monitoring). Many limnological investigations are linked to the concept of scientific monitoring, following a “problem solving” approach connected with the management of water resources. Experimental studies and modeling are restricted to specific niches. Overall, the scientific knowledge is quite scattered, showing hot-spots of specialized or integrated research in specific lakes and areas. The advancement of new knowledge in the LPL should rely on a better integration of scientific disciplines using multidisciplinary approaches, and on the continuous adoption of new advanced technologies and tools, contributing, besides basic research, to the next generation monitoring approaches. Finally, the preservation of LPL has to rely on water protection policies addressed towards the sustainable development of both terrestrial and aquatic ecosystems, following the “green” and “blue” infrastructure concepts. [ABSTRACT FROM AUTHOR]

This paper reports a study of oxygen and redox conditions, trophic status, and phytoplankton community in the meromictic Lake Idro (Italy) from 2010 to 2014. The sequence of causes and effects of meromixis are also evaluated by comparing recent research with studies conducted from the late 1960s to the mid-1990s. In the last half century, Lake Idro was steadily meromictic due to solutes which accumulated in its deep waters, along with both dissolved nutrients and chemically reduced substances produced by the anaerobic microbial metabolism. These substances were retained in bottom waters and made unavailable to upper layers until stratification broke. Mixing episodes occurred in 2005-2006 altering stratification, and oxygen and nutrient distribution within the lake. The potential full overturn effects were also evaluated as potential oxygen consumption due to the oxidation of reduced substances to forecast possible oxygen exhaustion and collapse of biological communities. Finally, meromixis is discussed as a potential threat for deep perialpine lakes using Lake Idro as a reference to comparatively evaluate the present status and possible future trends. [ABSTRACT FROM AUTHOR]

Anthropic structures have been deployed in aquatic environments for the most variable purposes. Here, we review the use of artificial aquatic habitats (AAHs) worldwide through a systematic and comprehensive search of peer-reviewed literature. We aimed to synthesize the knowledge on the subject, identify gaps, and propose new perspectives for future research. In total, 460 peer-reviewed papers from 1972 to mid-2016 were included in our systematic review. Field studies carried out in marine temperate environments were predominant, whereas fewer efforts have been made in marine tropical and freshwater ecosystems. Experimental habitats made of concrete were the most common artificial structures. Visual census was the most used sampling method, and there was a dominance of short-term (< 12 months) and shallow waters (< 5 m depth) studies. Fish was the most studied group (18%), whereas tunicates encompassed the large proportion of non-native species associated with AAHs (32.9%). Although idealized for the promotion of biodiversity, AAHs have been serving as stepping stones for non-native invasive species, facilitating biotic homogenization by increasing the connectivity of hard-bottom systems. The scarcity of studies in coastal tropical and freshwater ecosystems, as well as the efforts with reduced temporal scales and restricted depths, calls for future research to better understand the role of artificial habitats, especially in climate change scenarios. In this sense, we provide a conceptual framework exploring major issues regarding AAHs, including biodiversity status, ecosystem services, and climate change, in order to guide future research and assist conservation measures. [ABSTRACT FROM AUTHOR]

Ocean acidification can impair an animal's physiological performance and energetically demanding activities such as swimming. Behavioural abnormalities and changed activity in response to ocean acidification are reported in fish and crustacean species. We studied swimming activity in the calanoid copepod Pseudocalanus acuspes in response to near-future ocean acidification. Water and copepods were sampled from ten mesocosms deployed on the Swedish west coast. The experiments were conducted on animals reared in the mesocosms for 2 months during spring. Copepods were filmed after long-term (chronic) high-CO, and after 20 h acute exposure to CO. There was no significant effect of CO on copepods in chronic high-CO, nor significant effect after the 20 h acute exposure. In addition, we measured prosome length from a large number of adult copepods, but no effect of acidification on body size was found. In this study, P. acuspes did not show sensitivity to near-future pCO levels. Even if a number of papers suggest that copepods seem robust to future ocean acidification, interaction between multiple stress factors, such as elevated temperature, hypoxia and salinity changes may impair a copepod's ability to resist lowered pH. [ABSTRACT FROM AUTHOR]

Meteorological and climatic processes in mountain regions play a key role in many environmental systems, in particular the quantity and quality of water that influences both aquatic ecosystems and economic systems often far beyond the boundaries of the mountains themselves. This paper will provide a general overview of some of the particular characteristics of mountain weather and climate, to highlight some of the unique atmospheric features that are associated with regions of complex topography. The second part of the paper will focus upon characteristics of climate and climatic change in the European Alps, a region with a wealth of high quality data that allows an assessment on how climate and dependent environmental systems have evolved in the course of the 20th century and how alpine climate may undergo further changes to “global warming” in the 21st century, as the atmosphere responds to increasing levels of greenhouse gases that are expected in coming decades. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editors discusses article within the issue on topics including the importance and protection of small waters, the ecological effect of climate change, and the phosphorus retention capacity of small rivers.

Climate change is affecting the global hydrological cycle, causing drastic changes in precipitation patterns. Extreme climatic events are becoming more frequent and intense than in the past, leading to water-level fluctuations and affecting aquatic ecosystems. Semiarid regions are very susceptible to changing climate. We analyzed a 10 years dataset from a tropical semiarid reservoir during extreme hydrological events (heavy rains and prolonged drought), and evaluated phytoplankton functional responses to environmental conditions. We found, as hypothesized, that phytoplankton functional structure change in a temporal scale due to water–volume fluctuation induced by the rainfall pattern. Depth and inorganic material acted as environmental filters selecting phytoplankton groups. High water level seems to improve water quality and low water level worsen it. Colonial and filamentous cyanobacteria dominate the wet period; however, it may have a critical threshold during severe periods of drought, which will lead to dominance of groups well adapted to low light conditions and with mixotrophic metabolism. Phytoplankton functional approaches can simplify phytoplankton identification and reflect better the environmental conditions than the taxonomic approach. Therefore, these approaches can help to understand the shifts in aquatic ecosystems under extreme hydrological events and predict functional response of phytoplankton being an important tool to water management and conservation. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented in which editor discusses topics addressed in the conference on eeChallenges in Aquatic Sciences'' in Keelung, Taiwan in March 2013 including toxins and algal blooms, water quality and climate changes.

This article describes LIMPACS, a research initiative designed by the International Geosphere-Biosphere Program. The LIMPACS programme is designed to assess how and why lakes have changed, are changing and might change in the future as a result of human activity. The article outlines the program's major set of foci, such as: climate forcing, climate variability, land/ocean dynamics, and human-environment interactions. Other papers in this volume are based on a meeting of scientists to develop research priorities.

With the retreat of glaciers, new ponds and lakes are often formed. These are gradually colonised and become more productive as vegetation develops in their catchments, creating more complex food webs. Near the Jakobshavn Isbræ in West Greenland, we studied trophic structure and food web complexity using stable isotopes in 26 lakes belonging to two different age groups (19 new lakes and 7 nearby older (> 150 years) ones). The older lakes had significantly higher total nitrogen and pelagic chlorophyll-a concentrations, as well as a higher organic matter content in the surface sediment. The biomass and richness of cladocerans, copepods and rotifers were higher in the older lakes and so was the zooplankton:phytoplankton biomass ratio. Multivariate analyses showed a marked difference between the zooplankton communities of new and older lakes. Layman food web metrics indicated higher food chain length and width of invertebrates (zooplankton and benthic macroinvertebrates) in the older lakes, being significantly higher in lakes with fish. Our findings highlight a potential sequence of succession occurring in lakes created by glacial retreat in the Arctic, implying an increase in food web complexity and higher taxonomic (and likely also functional) diversity following ageing and increased nutrient state. [ABSTRACT FROM AUTHOR]

Flow-regulated discharges of water from control structures into estuaries result in hydrologic and water chemistry conditions that impact spatial and temporal variability in the structure and biomass of phytoplankton communities, including the potential for harmful algal blooms (HABs). The relationships between regulated Caloosahatchee River (i.e., C-43 Canal) discharges and phytoplankton communities in the Caloosahatchee Estuary and adjacent nearshore regions on the southwest coast of Florida were investigated during two study periods, 2009–2010 and 2018–2019. During periods of low to moderate discharge rates, when mesohaline conditions predominated in the estuary, and water residence times were comparatively long, major blooms of the HAB dinoflagellate species Akashiwo sanguinea were observed in the estuary. Periods of high discharge were characterized by comparatively low phytoplankton biomass in the estuary and greater influence of a wide range of freshwater taxa in the upper reaches. By contrast, intense blooms of the toxic dinoflagellate Karenia brevis in the nearshore region outside of the estuary were observed during high discharge periods in 2018–2019. The latter events were significantly associated with elevated levels of nitrogen in the estuary compared to lower average concentrations in the 2009–2010 study period. The relationships observed in this study provide insights into the importance of managing regulated discharge regimes to minimize adverse impacts of HABs on the health of the estuary and related coastal environments. [ABSTRACT FROM AUTHOR]

Salinization in tropical estuarine environments is expected as a result of climate change. The physiological performance of mangrove-associated key macroalgae can negatively be affected by increased salinity in such habitats. Thus, we analyzed photobiological and biochemical responses of the closely related red algae Bostrychia calliptera and Bostrychia montagnei incubated under a range of salinities (5, 11, 18, 37, 47, and 57 SA). Effective and maximum quantum yield, relative electron transport rate vs. photon fluence rate curves, photosynthetic parameters, and complementary energy dissipation pathways indicated that both species had lower photosynthetic performance under increased salinity, which was more strongly pronounced in B. calliptera. Both species increased their organic osmolyte contents with rising salinity stress. Dulcitol was the main organic osmolyte synthesized by B. calliptera, whereas B. montagnei synthesized dulcitol and sorbitol. Our results demonstrate that increased salinity in estuaries due to climate change will be detrimental to photosynthesis of both macroalgae, with B. calliptera more affected than B. montagnei. As B. montagnei synthesizes both dulcitol and sorbitol, it is more tolerant to salinity stress compared to B. calliptera. Our data document for the first time a new organic osmolyte distribution pattern in Bostrychia species, namely the occurrence of dulcitol only. [ABSTRACT FROM AUTHOR]

In Australia's Murray-Darling Basin, small-scale engineering works called 'environmental works and measures' have been implemented as a basis for river and other wetland conservation. While implementing these, governments seem to have embraced the beguiling notion that scarce water supplies can be divided further, while conserving the environment and maintaining agricultural production. The difficulties in doing this are expected to increase in the face of extreme climate variability. With this scenario as a backdrop, the $280 million (Monetary values ($) in this paper are in Australian dollars (AUD). At the time of writing AUD $1.00 = ~USD $1.02.) Living Murray and related programmes are assessed to see whether microengineering works to manage the hydrology of wetlands make for effective adaptation to water scarcity and climate change or whether it amounts to an overly narrow adaptation or maladaptation. Some measures were found to be substantially beneficial, such as the construction of fishways. However, under these programmes, only 0.6% of the Basin's wetlands would be inundated and there are significant risks including desiccation of non-target wetlands and further reductions in water allocations for the environment. It is recommended that trade-offs between alternative strategies are assessed as the basis for minimising perverse impacts under changing climatic and hydrological conditions. [ABSTRACT FROM AUTHOR]

The EU-funded research project WISER ('Water bodies in Europe: Integrative Systems to assess Ecological status and Recovery') developed new assessment methods required by the EU Water Framework Directive (WFD) for lakes, coastal and transitional waters. WISER also addressed the recovery of biotic assemblages from degradation. The results are summarised in five key messages, supported by papers in this special issue and by WISER results published elsewhere: (1) Response to stress differs between organism groups, water types and stressors; a conceptual model is proposed summarising how the individual organism groups respond to different types of degradation in rivers, lakes, transitional and coastal waters. (2) The sources of uncertainty differ between BQEs and water types, leading to methodological suggestions on how to design WFD sampling programmes. (3) Results from about 300 current assessment methods indicate geographical variations in metrics but assessments are comparable at an aggregated level ('ecological status'). (4) Scale and time matter; restoration requires action at (sub)-basin levels and recovery may require decades. (5) Long-term trends require consideration; the effects of both degradation and restoration at the water body or river basin scales is increasingly superimposed by multiple stressors acting at large scales, in particular by climate change. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including the changes in the species distribution in wetland, the response of wetland to climate change, and the efficacy of engineering responses in delivering water-efficient environmental outcomes for wetlands.

Loch Leven is a large, shallow lake in lowland Scotland, UK. Scientific research began here almost 200 years ago. Early research characterised the biodiversity and physical characteristics of the loch, providing an important historical background for future research. In the mid-1960s, this ad hoc approach was superseded by a more structured research programme under the umbrella of the International Biological Programme. This was the beginning of the Loch Leven long-term monitoring programme. Today, the results of these studies form one of the longest and most comprehensive limnological datasets for shallow freshwater lakes in the world, comprising more than 500 physical, chemical and biological variables collected at two-weekly intervals. To celebrate the 40th anniversary of the start of the long term monitoring programme, and to highlight the scientific investigations still being conducted at Loch Leven, the NERC Centre for Ecology & Hydrology (CEH) organised a symposium entitled "Loch Leven: 40 years of scientific research" in Kinross, Scotland, UK, on 11 December 2008. This examined the role of long-term monitoring in developing our understanding of the links between pollution, climate change and ecological responses in shallow lakes. This article introduces a series of papers summarising the scientific results presented at this meeting. [ABSTRACT FROM AUTHOR]

This paper delivers a conceptual framework for the ecological functioning and biodiversity patterns of lakes that is based on the floodpulse concept (FPC). The specific characteristics of rivers and lakes considering water-level fluctuations are compared, with respect to catchment linkages, temporal patterns, and hydraulic forces of flooding and drawdown. The influences of floodpulses on element cycles, biodiversity, and adaptations of lake biota are analyzed, and the importance of multi-annual flooding cycles is highlighted. The degree by which these water-level fluctuations influence lake ecosystems strongly depends on lake morphology, where shallow lakes or those with large shallow margins are the most sensitive. Although floodpulses play a major role for ecosystem services such as lake management and climate change mitigation schemes, this issue is only scarcely dealt with. Tenets of the extended FPC for lakes are formulated in order to overcome this problem. [ABSTRACT FROM AUTHOR]

The aquatic colonial stalked diatom, Didymosphenia geminata, has acquired notoriety in recent years because of huge increases in many rivers of temperate regions. However, in some streams in northern England it has probably or, in the case of the R. Coquet (Northumberland), certainly been abundant for many decades. The paper describes the nutrient environment and phosphatase activities of Didymosphenia in Stony Gill (N. Yorkshire), a fast-flowing stream draining an upland catchment with peaty soils overlying limestone. Organic phosphate formed 85% of the filtrable phosphate in the water during the study (January–August 2000), with a maximum in April. Colonies were most abundant in June, but had disappeared by August. Surface phosphomonoesterase (PMEase) and phosphodiesterase activities assayed from March to July showed low PMEase activity in early March, but otherwise both were high throughout the period and especially so in June and July. Use of BCIP-NBT staining procedure showed that PMEase activity occurred in the stalks. A more detailed study of colony structure and staining with material from the R. Coquet in June 2006 also showed marked PMEase activity, with staining localized in the upper part of the stalks and the cells remaining unstained. It is suggested that organic phosphate is hydrolyzed in the stalk and the inorganic phosphate passes to the cell via a central tube in the stalk. It seems likely that organic phosphate as a major P source is a key factor favouring the success of Didymosphenia. The possible impact of environmental changes in the catchment such as climatic warming, C loss from peat and atmospheric N deposition is discussed. [ABSTRACT FROM AUTHOR]

In most cases the negative impacts of climate change to aquatic ecosystems cannot be mitigated by measures in the river basin management. Ignoring climate change by the Water Framework Directive may have strong implications for the typology and quality assessment systems used for water bodies. As a result of climate change, water bodies, especially those located near the type boundaries may change their type. Compared to typology characteristics, water quality parameters are even more labile and may be easily affected by climate change. The paper exemplifies that the anticipated deterioration of water quality within the time frame relevant for WFD implementation may be large enough to endanger the fulfillment of the set water quality objectives. The review of the river basin characterization every six years, as required by the WFD, might also include re-evaluation of reference conditions according to the changes observed at pristine reference sites. As a consequence, the restoration targets (i.e., the good ecological status) would also need to be evaluated periodically. [ABSTRACT FROM AUTHOR]

Present-day Mediterranean marine biodiversity is undergoing rapid alteration. Because of the increased occurrence of warm-water biota, it has been said that the Mediterranean is under a process of ‘tropicalization’. This paper analyses the main patterns of the Mediterranean Sea tropicalization and considers briefly its extent and consequences. As happened during previous interglacial phases of the Quaternary, Atlantic water, entering via the Straits of Gibraltar, carries into the Mediterranean species that are prevalently of (sub)tropical affinity. On the other side of the basin, Red Sea species penetrate through the Suez Canal, a phenomenon called lessepsian migration from the name of F. De Lesseps, the French engineer who promoted the cutting of the Canal. Also the many exotic species introduced by humans voluntarily or involuntarily are nearly always typical of warm waters. Climate change combines with Atlantic influx, lessepsian migration and the introduction of exotic species by humans to the establishment of tropical marine biota in the Mediterranean Sea. Present-day warming ultimately favours the spread of warm-water species through direct and indirect effects, and especially by changing water circulation. It is impossible at present to foresee to what extent the exuberance of warm-water species will affect the trophic web and the functioning of marine ecosystems in the Mediterranean Sea of tomorrow. While Mediterranean Sea communities are modifying their pattern of species composition, they do not seem to be acquiring a more marked tropical physiognomy: Mediterranean coastal marine ecosystems are still dominated by frondose algae (even if the species that are gaining ascendancy are of tropical origin) and not by corals as is normal in tropical seas. [ABSTRACT FROM AUTHOR]

A Wetland Change Model has been developed to identify the vulnerability of coastal wetlands at broad spatial (regional to global (mean spatial resolution of 85 km)) and temporal scales (modelling period of 100 years). The model provides a dynamic and integrated assessment of wetland loss, and a means of estimating the transitions between different vegetated wetland types and open water under a range of scenarios of sea-level rise and changes in accommodation space from human intervention. This paper is an overview of key issues raised in the process of quantifying broad-scale vulnerabilities of coastal wetlands to forcing from sea-level rise discussing controlling factors of tidal range, sediment availability and accommodation space, identification of response lags and defining the threshold for wetland loss and transition. [ABSTRACT FROM AUTHOR]

Climatic variation and change affect the dynamics of organisms and ecosystem processes. Many studies in the past have analyzed and discussed various climate-driven effects on different components of the lake ecosystem. Only a few synthesis papers have been published in this field. In this overview, a conceptual model has been developed to help explain why lakes respond individually to climate. The model consists of two main components, a so-calledLandscape Filtercomprising the features of geographical position, catchment characteristics and lake morphology, and a so-calledInternal Lake Filter, comprising the features of lake history and biotic/abiotic interactions. The application of this conceptual model on published literature findings illustrates the strength in this encompassing perspective. An assessment of current climate research methods is presented with some perspectives given. [ABSTRACT FROM AUTHOR]

Ponds and "pondscapes" (networks of ponds) are crucial habitats for biodiversity and for delivering multiple benefits to humans, so-called "Nature's Contribution to People", such as climate mitigation and adaptation to climate change, creation, and maintenance of habitat for biodiversity, water purification, flood mitigation and cultural benefits (e.g., recreational possibilities). However, ponds are not often considered as Nature-based Solutions to provide all these benefits. In addition, there is insufficient knowledge on how to manage and restore ponds to maximise their role to increase the resilience of ecosystems and society to climate change. To facilitate improved implementation of ponds as Nature-based Solutions for the delivery of a wide range of Nature Contributions to People, it is important to generate and integrate biodiversity, ecosystems, societal, economic and policy knowledge. Hence, there is a need for evidence-based guidance to support the broader use of ponds. Here, we review the role of ponds and pondscapes in delivering Nature's Contributions to People and provide an overview of the challenges and opportunities for their broader implementation as Nature-based Solutions. Finally, we propose a conceptual framework that can help the implementation of pond Nature-based Solutions, and that outlines future research needs. [ABSTRACT FROM AUTHOR]

Climate change could alter fluxes of organic matter and macronutrients through freshwater ecosystems potentially affecting stream organisms. However, riparian controls on litter dynamics offer an opportunity to adapt headwaters to climate change by protecting or restoring riparian vegetation. We assessed how riparian land cover and climatic variability affected the supply, retention and downstream transport of particulate organic matter (POM) in headwaters—the most extensive small water bodies in temperate landscapes. Leaf litter inputs, benthic stocks and suspended organic matter were measured nominally monthly in second–third-order streams draining broadleaf woodland, conifer, acid moorland and circumneutral moorland over four years with varying discharge. Streams draining broadleaf woodland received more leaf litter from the riparian zone than conifer and moorland and transported higher concentrations of CPOM and FPOM at base flows. Broadleaf sites had higher CPOM stocks, even after hydrological events that reduced CPOM in conifer and moorland sites. In contrast, FPOM dynamics reflected hydrological conditions irrespective of land cover. These results show how some organic matter fractions in streams are sensitive to hydrological conditions, illustrating how wetter climates will influence FPOM exports. Nevertheless, riparian broadleaves have the potential to offset climatic effects on organic matter processing in headwaters through the replenishment and retention of CPOM. [ABSTRACT FROM AUTHOR]

Droughts, or severe reductions of water flow, are expected to become more frequent and intense in rivers in many regions under the ongoing climate change scenario. It is therefore important to understand stream ecosystem functioning under drought conditions. We performed a meta-analysis of studies addressing drought effects on litter decomposition in streams (50 studies contributing 261 effect sizes) to quantify overall drought effects on this key ecosystem process and to identify the main moderators controlling these effects. Drought reduced litter decomposition by 43% overall, which can impact energy and matter fluxes along heterotrophic food webs. The magnitude of drought effects on litter decomposition depended on the type of drought (natural drought > human-induced drought), type of decomposer community (microbes + macroinvertebrates > microbes) under natural drought, climate (warm and humid > temperate and Mediterranean) under human-induced drought, and on litter identity. The magnitude of drought effects on litter decomposition also increased with the severity of the drought. The effects of ongoing climate change will likely be strongest in streams with abundant shredders undergoing natural drought, especially if the streams become temporary. The composition of the riparian vegetation may modulate the magnitude of drought effects on litter decomposition, which may have management applications. [ABSTRACT FROM AUTHOR]

Arctic stream biofilm responses to ongoing climate-related changes in physical and chemical conditions have major implications for stream food webs and biogeochemical cycles. Yet, such effects have rarely been studied outside summer months or at sub-catchment scales in the Arctic. We used deployments of nutrient diffusing substrates (NDS) to assess the spatial (20 deployments) and seasonal patterns (10 deployments) and physical and chemical drivers of nutrient limitation within an Arctic stream catchment. Results show that nutrient limitation of autotrophic processes was common during summer, but that light inhibited biomass accrual under the ice in winter. Alongside single N, P and C responses, co-limitation dominated the overall pattern of limitation over time and across the catchment. However, the primary limiting nutrient to autotrophs changed from N to P in parts of the catchment with higher N concentrations. As Arctic studies are often conducted at individual sites during summer, these may miss shifts in the drivers of stream productivity that arise from variable nutrient, temperature, and light regimes. Our results caution against focusing on one single most important limiting nutrient, as we found that this can shift seasonally and over small spatial scales in this Arctic catchment. [ABSTRACT FROM AUTHOR]

While many studies predict changes in the distribution of individual species as a result of climate change, few studies have assessed such changes at the community level for aquatic invertebrates. We used ostracods (bivalved micro-crustaceans) to assess the effects of climate change on regional species richness, (re-) distribution and community composition across the river basins of the Southern Cone of South America. Using a range of niche-based models, we present projections of changes in diversity components in the light of two scenarios on increased carbon emissions: the moderate-optimistic (RCP 4.5) and the pessimistic (RCP 8.5) scenarios from four climate models on 2050 and 2080 scenarios. Future projections show increase in the number of (mapped) cells with a richness up to five species as compared to present-day situations. La Plata basin (LPLA) presents the highest species loss, mainly in the Paraguay and Paraná rivers, while the species gain occurred mainly in the La Puna Region, North Chile-Pacific Coast and southern LPLA basins. Global change might impact ostracod communities even on a medium term (2050). Despite losses of local species in all future scenarios, a small portion of the LPLA was identified as a potential future climatic refugia for ostracod communities, while the distribution area in Patagonia was predicted to be extremely small for some ostracods at the southernmost parts of South Argentina-South Atlantic Coast and South Chile-Pacific Coast basins in both futures. These results indicate that non-model organisms can also contribute greatly to formulate evidence-based management plans for aquatic ecosystems under climate change scenarios. [ABSTRACT FROM AUTHOR]

Climatic and hydrological variation is of utmost importance in regions of the globe facing water scarcity and river intermittency (e.g. areas under Mediterranean influence). The main aim of this study was to compare the macroinvertebrate community structure and its bioindicator value (i.e. waterbody ecological status) in streams from three Portuguese regions (Regions C, N and S), representing distinct climatic features and water availability scenarios. Results showed that, overall, sampling sites differed in their climatic, hydromorphological and physical and chemical features, and environmental (abiotic) and ecological (community dissimilarities) gradients among regions were clearly identified. Sites from Regions C (wettest) and S (driest) represented non-overlapping clusters of samples, both in terms of their environmental context and ecological (dis)similarity; sites from Region N occupied an intermediate position, and their macroinvertebrate community was highly variable locally. This coincided with overall higher ecological quality and uniformity in Region C, whereas Regions N and S were more heterogeneous and generally presented lower ecological quality. Our data showed that climate (and associated water scarcity) is coupled with other environmental drivers of the macroinvertebrate community structure, highlighting a shared influence of the three environmental components (climatic, hydromorphological, and physical and chemical) in the modulation of macroinvertebrate communities. [ABSTRACT FROM AUTHOR]

In aquatic ecosystems, phytoplankton is an important component of biodiversity. Although much is already known about the main climate change agents impacting phytoplankton, it is necessary to systematize this knowledge in order to identify the main trends, gaps, and perspectives for future research in this field. Thus, we conducted a systematic review of the global scientific literature on phytoplankton and climate change. We found 660 articles published between 1991 and 2020 using the Web of Science platform. The studies were mostly conducted in marine and freshwater environments using an observational approach. The main variables studied were temperature and nutrient concentrations. The main phytoplankton response variables are linked to metrics of species composition/diversity or physiological/biochemical traits of organisms. We found that over the last 30 years, a large number of climatic predictors and phytoplankton response variables have been studied. However, the number of studies evaluating interactions of multiple variables (climate and phytoplankton response) is small in comparison to the total amount of research. Thus, the combination of methodological approaches, as well as the simultaneous study of multiple climate predictors and response variables, can help in the production of new information to understanding of the effects of climate change on phytoplankton. [ABSTRACT FROM AUTHOR]

The authors reflect on the importance of coastal wetlands and lagoons and the need for ecosystem management. They discuss the impacts of multiple stressors and human activities on these vulnerable ecotones as described in articles in this issue. They suggest that global climate changes and sea level rise together with coastal subsidence and saltwater intrusion put these invaluable buffer zones at risk.

Small streams in the temperate continental region of central Europe have been recently exposed to frequent drying. We investigated the effects of drying on clitellate communities in 25 small streams evenly distributed along the gradient of flow intermittence. We observed that the community exposed to both irregular and periodic drying could maintain local species diversity. However, significant differences in clitellate species composition were observed between perennial, irregularly drying, and intermittent streams. The effect of drying was even stronger in intermittent streams, where significantly lower beta diversity was observed compared to perennial streams. The most important changes in clitellate composition were controlled by water temperature and geographical variables in perennial streams, while streams affected by drying were controlled by climate, with high mean July air temperature and low annual precipitation sums amplifying the effect. The abundance of semiaquatic species was also affected by the periodicity of the dry phase, with their proportion predicted in the regression tree analysis to be 11% in perennial and irregularly drying streams, and 40% in periodically drying streams. The observed changes in clitellate community structure suggest a gradual adaptation to increasing drying severity, in which sensitive species (e.g., rheobionts) may be replaced by desiccation-tolerant and semiaquatic species. [ABSTRACT FROM AUTHOR]

We combined paleolimnological reconstructions and space-for-time substitutions to unravel chironomid biodiversity responses to climate change in subarctic mountains across temporal and spatial scales. Using sediment records, we found that long-term temporal changes in chironomid taxonomic diversity were mainly induced by the temperature tolerance/optimum of species, while little changes in functional diversity were found due to the replacement of similar functional-type taxa within the community. Overall, paleolimnological reconstructions suggested the selection of larger chironomid species by long-term climate cooling and little changes in trophic guilds. Space-for-time substitutions showed, however that low-elevation lakes with forested have more sediment-feeding taxa and larger larvae than high-elevation lakes, thus, suggesting the selection of large chironomid morphotypes with a sediment-feeding mode under warmer climate. Space-for-time substitutions and paleolimnological reconstructions, therefore, gave contrasting results for the link between climate and functional diversity of chironomid communities, likely because space-for-time substitutions failed to match the extent of both spatial and temporal climatic gradients. We suggest that future studies must address biodiversity issues across both temporal and spatial scales as an improved understanding of biodiversity responses to climate change may help us to understand how biodiversity will be affected by ongoing and future change. [ABSTRACT FROM AUTHOR]

The Great Lakes region of western Mongolia includes a diversity of lake ecosystems, from alpine freshwater to lowland, saline lakes, which increasingly face environmental threats from excessive grazing and climate change. We assessed environment-species relationships and patterns of biodiversity of non-biting midges (Diptera: Chironomidae) in 55 western Mongolian lakes using surface-floating pupal exuviae. Overall, the gamma diversity of chironomids from these lakes was high with 117 taxa, but alpha diversity was relatively low. Results from canonical correspondence analysis indicated that chironomid communities were most strongly related to salinity and water temperature. Indicator species analysis identified 12 taxa which were indicative of four lake salinity categories: freshwater, subsaline, hyposaline, and mesohaline. Most of the variation in the chironomid communities could be attributed to the loss of taxa in lakes with higher salinity. Observations also suggested that groundwater upwelling along the margins of lakes with extreme salinity could possibly allow small populations of chironomids to survive in littoral zones. Climate change and watershed disturbance are already altering water quality in western Mongolian lakes, and our results establish a baseline for chironomid communities along gradients of salinity and temperature by which future studies may be compared. [ABSTRACT FROM AUTHOR]

Calcium (Ca) concentrations of many softwater lakes on the Canadian Shield have been in decline for decades as a response primarily to regional acid deposition and repeated cycles of forest harvesting. These Ca declines are of ecological interest, as many lakes have fallen to Ca levels detrimental to the fitness of ecologically important Ca-rich cladoceran taxa such as Daphniapulex. However, distinguishing the impacts of reduced Ca from acidification (i.e., decreasing pH) on Ca-demanding fauna has proven difficult due to strong correlations between pH and Ca in softwater lakes. Here, we examine cladoceran sedimentary assemblages from low Ca lakes (mean present-day Ca < 2.0 mg l −1) in the Experimental Lakes Area (ELA) of Ontario, Canada, where Ca concentrations have declined since the 1980s, despite being closed to forestry and remote from (i.e., not downwind of) major sources of acid deposition. Differences between present-day and pre-industrial cladoceran assemblages were greatest among planktonic taxa, including Bosmina spp. and Holopedium glacialis. However, daphniid remains were present in only three of the ten study lakes with minimal directional trends. Overall, in these ELA lakes, daphniid abundance was low historically, and impacts possibly attributable to Ca declines have been obscured by the effects of regional climate warming. [ABSTRACT FROM AUTHOR]

Aquatic insects are the dominant taxon group in most freshwater ecosystems. As temperature is the main driver of their life cycle development, metabolic activity, and geographic distribution, these macroinvertebrates are particularly suitable for large scale and comparative studies of freshwater community responses to climate change. A dataset of bio-ecological traits of 1,942 Ephemeroptera, Plecoptera, and Trichoptera (EPT) taxa was used to analyze (1) the relationships among traits, (2) the potential vulnerability of EPT species to climate change, and (3) the geographical occurrence patterns of these potentially endangered species at the scale of European ecoregions. By means of a fuzzy correspondence analysis (FCA), two gradients emerged: (1) a longitudinal gradient, describing successive upstream–downstream features, and (2) a biogeographical gradient, separating endemic and micro-endemic species from widely distributed taxa. Moreover, aquatic insects of southern European ecoregions emerged as those most endangered in terms of potential vulnerability to climate change. Comparative multi-taxon studies provide important new insights into freshwater ecosystem functioning and responses to climate change, and could be the first step toward developing integrative monitoring or assessment tools (e.g., trait-based indicators at the species level) by means of non-arbitrary statistical methods. [ABSTRACT FROM AUTHOR]

Mediterranean-climate rivers are projected to warm by 0.5–4°C and river flows to decline by 34% by 2071–2100. Using data from 191 Greek streams/rivers, we projected macroinvertebrate responses to 12 climate change scenarios for 2071–2100 to identify critical hydro-thermal limits beyond which irreversible responses are triggered and to assess the potential of environmental flows to mitigate the ecological impacts of climate change. Overall, macroinvertebrate assemblages will be less diverse, represented mostly by limnophilic, warm-dwelling taxa. Ephemeroptera, Plecoptera, Trichoptera and some Diptera will be replaced by Odonata, Amphipoda, Gastropoda and Heteroptera. Moderate average warming (1–1.8 °C) will not significantly affect assemblage abundance and richness but extreme warming (≥ 5 °C) will shift to limnophilic-type assemblages even in non-lentic hydrological conditions. Our models predict irreversible macroinvertebrate responses at ≥ 3°C average warming combined with ≥ 50% average flow decrease, or ≥ 5°C warming regardless of flow decrease, or ≥ 90% flow decrease regardless of warming. Beyond these limits, cold-dwelling taxa such as Limnephillidae and Potamanthidae will almost disappear (abundance: –87%), replaced by warm-dwelling Physidae (+ 100%) and Coenagrionidae (+ 97%). Environmental flows could mitigate the impacts of warming, compensating macroinvertebrates for up to 3°C when 50% decreased flows are provided, and for up to 5°C when flows within the 0–25% range are provided. [ABSTRACT FROM AUTHOR]

Climate change has the potential to greatly alter species distributions and threatens biodiversity in marine ecosystems. Mapping changes in species distribution patterns under climate change will help facilitate management strategies to maintain ecosystem structure and function. The lizardfish Harpadon nehereus is an aggressive predator that has experienced rapid population growth along the coast of China in recent decades, compressing the ecological niches of other marine species and disrupting food webs. If this species' range is shifting due to climate change, it could further impact the integrity of ecological communities. To map the distribution of H. nehereus, we developed an ensemble species distribution model and projected the present and future habitat suitability in Chinese coastal waters. Annual mean benthic water temperature was identified as the most important variable affecting the projected distribution of H. nehereus, followed by water depth and salinity. Currently suitable habitats are along the coast from Guangxi Province to the southern Jiangsu Province. As climate changes, the southern portion of its distribution is predicted to recede with habitat losses, and the overall suitable habitat will shift northward. To avoid the potential impacts of H. nehereus redistribution, precautionary management based on species distribution modeling would help to maintain healthy marine ecosystems in the newly invaded areas. [ABSTRACT FROM AUTHOR]

The greatest known global response of lakes to climate change has been an increase in water temperatures. The responses of many lake fishes to warming water temperatures are projected to be inadequate to counter the speed and magnitude of climate change. We experimentally evaluated the responses of embryos from a group of cold, stenothermic fishes (Salmonidae Coregoninae) to increased incubation temperatures. Study groups included cisco (Coregonus artedi) from lakes Superior and Ontario (USA), and vendace (C. albula) and European whitefish (C. lavaretus) from Lake Southern Konnevesi (Finland). Embryos from artificial crossings were incubated at water temperatures of 2.0, 4.5, 7.0, and 9.0°C, and their responses were quantified for developmental and morphological traits. Embryo survival, incubation period, and length-at-hatch were inversely related to incubation temperature whereas yolk-sac volume increased with incubation temperature within study groups. However, varying magnitudes of responses among study groups suggested differential levels of developmental plasticity to climate change. Differential levels of parental effects indicate genetic diversity may enable all study groups to adapt to cope with some degree of changing environmental conditions. Our results suggest that the coregonines sampled within and among systems may have a wide range of embryo responses to warming incubation conditions. [ABSTRACT FROM AUTHOR]

Mountain lakes are increasingly impacted by a series of both local and global disturbances. The present study reveals the eutrophication history of a remote subalpine lake (Oberer Soiernsee, Northern Alps, Germany), triggered by deforestation, alpine pasturing, hut construction, tourism and atmospheric deposition, and identifies the intertwined consequences of on-going global warming on the lake's ecosystem. The primary objective was to disentangle the various direct and indirect impacts of these multiple stressors via down-core analyses. Our multi-proxy approach included subfossil diatom assemblages, carbon and nitrogen stable isotope ratios and subfossil pigments from dated sediments. Shifts within the diatom assemblages were related to variations in trophic state, lake transparency, water temperature and thermal stratification. The organic carbon isotope (δ13Corg) records, the diatom valve density and the pigment concentrations documented the development of primary production and composition. Total nitrogen isotope values (δ15N) are more likely to reflect the history of atmospheric nitrogen pollution than lake-internal processes, also mirrored by the decoupling of δ15N and δ13Corg trends. The composition of sedimentary pigments allowed a differentiation between planktonic and benthic primary production. Concordant trends of all indicators suggested that the lake ecosystem passed a climatic threshold promoted by local and long-distance atmospheric nutrient loadings. [ABSTRACT FROM AUTHOR]

Phragmites australis is a cosmopolitan plant species with high intraspecific diversity and phenotypic plasticity. Due to its variability and large ecological niche breadth, subgroups of P. australis have become invasive in North America, and this invasion has been recognized late. While this cryptic invasion on the American continent has received much attention, little is known about the potential invasiveness of other subgroups, especially within Asian/Australian P. australis. We therefore compared the performance of three subgroups within the Asian/Australian group: a freshwater (CN) and an estuarine (YRD) subgroup collected in China and a genetically closely related subgroup collected from Australia (FEAU), grown in two common gardens in China. Our results showed that the FEAU subgroup had no strong invasive potential, as its total biomass, height, shoot number, specific leaf area, and stomatal conductance were lower than that of the two native subgroups. All three subgroups responded similarly with most traits to the different climates of the gardens, albeit with different response strength, expressed as phenotypic plasticity indices. The potential cryptic invasion risk of the FEAU subgroup in China seems to be low, since its functional traits showed low competitiveness and most traits with the lowest plasticity occurred in FEAU. However, caution is still advised, because other invasive mechanisms, such as enemy release or the performance under extreme environmental conditions were not tested in our study. [ABSTRACT FROM AUTHOR]

Reduced streamflow because of climate change presents a major threat to aquatic biodiversity in arid, semi-arid and Mediterranean climatic regions. Freshwater mussels are particularly sensitive to this threat, because of their sedentary nature and limited mobility as juveniles or adults. The freshwater mussel Westralunio carteri, which is endemic to south-western Australia, has undergone a 49% reduction in range in the last 50 years, and a drying climate presents substantial extinction risk, as highlighted by two recent cases of mass mortality. Experimental studies found that mussels respond to water emersion by first tracking receding water levels, then burrowing. The amount of horizontal movement by mussels was not affected by size, but smaller mussels initiated burrowing sooner and were also more likely to be predated if they remained on the surface. Burrowing and shading both significantly reduced mortality rate and increased survival time when mussels were exposed to drying; when shaded or allowed to burrow, mussels could survive at least 62 days out of water. Predicted future reductions in streamflow are likely to increase the mortality rate in W. carteri, but it may be possible to partially avert the adverse effects of drying rivers by increasing riparian shading. [ABSTRACT FROM AUTHOR]

Females of freshwater mussels spawn eggs which, after fertilization, are brooded until the developing larvae reach a stadium ready to infest a fish host in order to complete the obligate parasitic phase of their life. We investigated the duration of the brooding period in the endangered thick-shelled river mussel Unio crassus in two rivers in southern Poland and identified the stadia of glochidia development which could be used to assess current larval developmental stages. The eggs were fertilized in marsupia. The duration of the brooding period shortened significantly during the season, from 35 days in early spring to 9 days in summer. The break between consecutive broods was usually short but very variable: from almost no break to 17 days. 20% of brooding events inspected every other day were miscarried at different stadia of larval development. The recorded differences in brooding time may significantly influence the reproductive output of individuals and populations, depending on the thermal conditions, which may be affected by both anthropogenic impact and global climate change. The study offers a practical scheme for assessing female gravidity advancement in Unio crassus, which may be very informative for the future application of conservation measures in this endangered European species. [ABSTRACT FROM AUTHOR]

Chironomids are a useful group for investigating body size responses to warming due to their high local abundance and sensitivity to environmental change. We collected specimens of six species of chironomids every 2 weeks over a 2-year period (2017–2018) from mesocosm experiments using five ponds at ambient temperature and five ponds at 4°C higher than ambient temperature. We investigated (1) wing length responses to temperature within species and between sexes using a regression analysis, (2) interspecific body size responses to test whether the body size of species influences sensitivity to warming, and (3) the correlation between emergence date and wing length. We found a significantly shorter wing length with increasing temperature in both sexes of Procladius crassinervis and Tanytarsus nemorosus, in males of Polypedilum sordens, but no significant relationship in the other three species studied. The average body size of a species affects the magnitude of the temperature-size responses in both sexes, with larger species shrinking disproportionately more with increasing temperature. There was a significant decline in wing length with emergence date across most species studied (excluding Polypedilum nubeculosum and P. sordens), indicating that individuals emerging later in the season tend to be smaller. [ABSTRACT FROM AUTHOR]

This review compiles principal data on Antarctic cynobacteria published in recent decades and focuses on the diversity, environmental adaptations, and ecotypes of these microorganisms. Multidisciplinary investigation of Antarctica is important especially in times of global climate change and anthropogenic threats to unaltered ecosystems. Antarctica, which has been disconnected from Gondwana for the last 65 Myr, harbors relict biota mainly including microorganisms adapted to multiextreme environments. Cyanobacteria represent the most well studied Antarctic microorganisms related to the cell biology, abundance, distribution, and symbioses. However, substantial drawbacks remain, e.g., (i) the diversity of Antarctic cyanobacteria has been evaluated without a consensus between bacteriologists and phycologists due to the intricate interplay of morphological records, genomic data and culturing restrictions as well as taxonomic obstacles; (ii) although the main strategy of Antarctic cyanobacteria is biofilms (in particular, microbial mats), detailed knowledge on these symbiotic systems is still fragmentary; (iii) the specificity of the 'Antarctic cyanobacteria biosphere' should be better understood in light of unresolved questions related to endemism in prokaryotes, and (iv) the strains of Antarctic cyanobacteria maintained in culture are not numerous and not very diverse. These issues are at the forefront of cyanobacteriology, which is supported by related biosciences and earth sciences. [ABSTRACT FROM AUTHOR]

During summer 2014, three hypersaline brines were discovered in two frozen lakes of Boulder Clay (Northern Victoria Valley, Antarctica). Ongoing research seeks to gain novel insights on the microbial ecology of such environments, in order to further the understanding of life adaptation to extreme conditions. To this aim, the abundance of prokaryotic cells (including cell morphologies and size for biomass conversion), the amount of viable cells (in terms of membrane-intact cells and respiring cells), the viral count, the physiological profiles at community level and the main microbial enzymatic activities were described. The brines differed each other in terms of prokaryotic cells' abundance, size, and viability as well as viral abundance. Cell morphotypes and metabolic responses also varied among the brine samples. Underground interconnections were likely to occur, with the microbial community becoming more abundant and structured to better exploit the limited resource availability. Overall, complex interactions among multiple environmental factors, including marine water origin, depth horizon, isolation time of the brines, and climatic variations, reflected on the microbial community distribution patterns and highlighted the need to preserve these niches of extreme life. [ABSTRACT FROM AUTHOR]

Warming and higher nitrogen loading induced by increasing precipitation are expected scenarios in north temperate regions as consequence of global climate change, with potential effects on the functional traits of submerged macrophytes and periphyton. Using an experimental heating facility we investigated the responses of three-week growth of two submerged macrophytes (Potamogeton crispus Linn. and Elodea canadensis Michx.), and periphyton on these plants and their artificial mimics. Analysis was based on IPCC climate scenarios A2 (ca. + 3°C) and A2 + 50% (called A3 in our study) relative to ambient conditions, across warming in spring and early summer (summer showed higher nitrogen loading). Some functional traits of plants showed species-specific responses to warming: A3 promoted the growth of E. canadensis in both seasons, while for P. crispus warming reduced the leaf number in spring but enhanced the turion production in early summer. Periphyton biomass was lower in A3 in early summer, but not in spring. Our results further show that the growth of E. canadensis and the asexual reproduction of P. crispus might increase in a warmer future. Moreover, we found a complex response of periphyton to the temperature increase and substrate type, varying with season and nutrient state. [ABSTRACT FROM AUTHOR]