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AbstractThe hydrology of riparian areas changes rapidly these years because of climate change‐mediated alterations in precipitation patterns. In this study, we used a large‐scale in situ experimental approach to explore effects of drought and flooding on plant taxonomic diversity and functional trait composition in riparian areas in temperate Europe. We found significant effects of flooding and drought in all study areas, the effects being most pronounced under flooded conditions. In near‐stream areas, taxonomic diversity initially declined in response to both drought and flooding (although not significantly so in all years) and remained stable under drought conditions, whereas the decline continued under flooded conditions. For most traits, we found clear indications that the functional diversity also declined under flooded conditions, particularly in near‐stream areas, indicating that fewer strategies succeeded under flooded conditions. Consistent changes in community mean trait values were also identified, but fewer than expected. This can have several, not mutually exclusive, explanations. First, different adaptive strategies may coexist in a community. Second, intraspecific variability was not considered for any of the traits. For example, many species can elongate shoots and petioles that enable them to survive shallow, prolonged flooding but such abilities will not be captured when applying mean trait values. Third, we only followed the communities for 3 years. Flooding excludes species intolerant of the altered hydrology, whereas the establishment of new species relies on time‐dependent processes, for instance the dispersal and establishment of species within the areas. We expect that altered precipitation patterns will have profound consequences for riparian vegetation in temperate Europe. Riparian areas will experience loss of taxonomic and functional diversity and, over time, possibly also alterations in community trait responses that may have cascading effects on ecosystem functioning.

Science-based, multinational management of the Baltic Sea offers lessons on amelioration of highly disturbed marine ecosystems.

The likelihood of an ecological system to undergo undesired regime shifts is expected to increase as climate change effects unfold. To understand how regional climate settings can affect resilience; i.e., the ability of an ecosystem to tolerate disturbances without changing its original structure and processes, we used a synchronized mesocosm experiment (representative of shallow lakes) along a latitudinal gradient. We manipulated nutrient concentrations and water levels in a synchronized mesocosm experiment in different climate zones across Europe involving Sweden, Estonia, Germany, the Czech Republic, Turkey and Greece. We assessed attributes of zooplankton communities that might contribute to resilience under different ecological configurations. We assessed four indicator of relative ecological resilience (cross-scale, within-scale structures, aggregation length and gap size) of zooplankton communities, inferred from discontinuity analysis. Similar resilience attributes were found across experimental treatments and countries, except Greece, which experienced severe drought conditions during the experiment. These conditions apparently led to a lower relative resilience in the Greek mesocosms. Our results indicate that zooplankton community resilience in shallow lakes is marginally affected by water level and the studied nutrient range unless extreme drought occurs. In practice, this means that drought mitigation could be especially challenging in semi-arid countries in the future.

AbstractSubmerged macrophytes are of key importance for the structure and functioning of shallow lakes and can be decisive for maintaining them in a clear water state. The ongoing climate change affects the macrophytes through changes in temperature and precipitation, causing variations in nutrient load, water level and light availability. To investigate how these factors jointly determine macrophyte dominance and growth, we conducted a highly standardized pan‐European experiment involving the installation of mesocosms in lakes. The experimental design consisted of mesotrophic and eutrophic nutrient conditions at 1 m (shallow) and 2 m (deep) depth along a latitudinal temperature gradient with average water temperatures ranging from 14.9 to 23.9°C (Sweden to Greece) and a natural drop in water levels in the warmest countries (Greece and Turkey). We determined percent plant volume inhabited (PVI) of submerged macrophytes on a monthly basis for 5 months and dry weight at the end of the experiment. Over the temperature gradient, PVI was highest in the shallow mesotrophic mesocosms followed by intermediate levels in the shallow eutrophic and deep mesotrophic mesocosms, and lowest levels in the deep eutrophic mesocosms. We identified three pathways along which water temperature likely affected PVI, exhibiting (a) a direct positive effect if light was not limiting; (b) an indirect positive effect due to an evaporation‐driven water level reduction, causing a nonlinear increase in mean available light; and (c) an indirect negative effect through algal growth and, thus, high light attenuation under eutrophic conditions. We conclude that high temperatures combined with a temperature‐mediated water level decrease can counterbalance the negative effects of eutrophic conditions on macrophytes by enhancing the light availability. While a water level reduction can promote macrophyte dominance, an extreme reduction will likely decrease macrophyte biomass and, consequently, their capacity to function as a carbon store and food source.

European seas are encountering an upsurge in competing marine activities and infrastructures. Traditional exploitation such as fisheries, tourism, transportation, and oil production are accompanied by new sustainable economic activities such as offshore windfarms, aquaculture, and tidal and wave energy. One proposed solution to overcome possible competing claims at sea lies in combining these economic activities as part of Multi-Use Platforms at Sea (MUPS). MUPS can be understood as areas at sea, designated for a combination of activities, either completely integrated in a platform or in shared marine space. MUPS can potentially benefit from each other in terms of infrastructure, maintenance, etc. Developing MUPS in the marine environment demands adequate governance. In this article, we investigate four European sites to find out how governance arrangements may facilitate or complicate MUPs. In particular, we apply a framework specifying policy, economic, social, technical, environmental, and legal (PESTEL) factors to explore governance arrangements in four case study sites in different sea basins around Europe (the Mediterranean Sea, the Atlantic Ocean, the North Sea, and the Baltic Sea). The article concludes with policy recommendations on a governance regime for facilitating the development of MUPS in the future.

L'eutrophisation est la menace la plus pressante pour les lacs très calcaires (marneux) en Europe. Malgré leur chimie et leur biologie uniques, des études approfondies sur leurs conditions non impactées et leurs réponses à l'eutrophisation sont sous-représentées dans la littérature sur la conservation. Une étude paléolimnologique multi-indicateurs couvrant environ 1260 à 2009 a été entreprise à Cunswick Tarn (Royaume-Uni), un petit lac marneux actuellement eutrophique, afin de capturer les échelles de temps d'impact du centenaire. Les objectifs spécifiques étaient de 1) établir des modèles temporels de changement (progressif/abrupt) entre les groupes biologiques, testant ainsi les théories de résistance des communautés benthiques du lac Marl à l'enrichissement, et 2) comparer le dossier de base de l'état de référence avec les descriptions dominantes de l'état écologique élevé. Les analyses du calcium (Ca), du phosphore (P), des pigments, des diatomées, des amibes testées, des cladocères et des macrofossiles des sédiments ont révélé trois changements brusques dans la structure de l'écosystème. Le premier (1900), avec une augmentation de la biomasse en charophytes et d'autres indicateurs benthiques pauvres en nutriments, a soutenu les idées de résistance à l'eutrophisation dans les lacs Chara. La deuxième transition (années 1930), de la dominance des charophytes à celle des angiospermes, s'est produite parallèlement à des réductions de la couverture des macrophytes, à des augmentations des indicateurs eutrophiques et à une dégradation de la marne, à l'appui des idées de réponses seuils à l'enrichissement. Le carottier P a augmenté de façon constante dans les années 1990, lorsque des transitions rapides vers l'écologie des lacs peu profonds pélagiques ont eu lieu et que le Cunswick Tarn est devenu biologiquement non identifiable en tant que lac marneux. Le P total modéré auquel ces changements se sont produits suggère une grande sensibilité des lacs marneux à l'eutrophisation. De plus, les premiers enregistrements remettent en question les idées de corrélation entre la condition écologique, la biomasse des charophytes et le Ca des sédiments. Au lieu de cela, une faible production benthique, une couverture de macrophytes et une sédimentation de Ca ont été déduites. Les mesures de gestion doivent se concentrer sur la réduction des charges externes de nutriments et de sédiments aux premiers stades de l'impact afin de préserver les lacs marneux. La eutrofización es la amenaza más apremiante para los lagos altamente calcáreos (margas) en Europa. A pesar de su química y biología únicas, los estudios exhaustivos sobre sus condiciones no afectadas y las respuestas de eutrofización están subrepresentados en la literatura conservadora. En Cunswick Tarn (Reino Unido), un pequeño lago de margas actualmente eutrófico, se llevó a cabo un estudio paleolimnológico de múltiples indicadores que abarca desde aproximadamente 1260 hasta 2009, con el fin de capturar escalas de tiempo centenarias de impacto. Los objetivos específicos fueron 1) establecer patrones temporales de cambio (gradual/abrupto) en todos los grupos biológicos, probando así las teorías de resistencia de las comunidades bentónicas del lago de marga al enriquecimiento, y 2) comparar el registro central de la condición de referencia con las descripciones predominantes de alto estado ecológico. Los análisis de sedimentos de calcio (Ca), fósforo (P), pigmentos, diatomeas, amebas testadas, cladóceros y macrofósiles, revelaron tres cambios abruptos en la estructura del ecosistema. El primero (1900), con aumentos de biomasa en carófitos y otros indicadores bentónicos pobres en nutrientes, apoyó las ideas de resistencia a la eutrofización en los lagos Chara. La segunda transición (década de 1930), de la dominancia de los carófitos a las angiospermas, se produjo junto con reducciones en la cobertura de macrófitos, aumentos en los indicadores eutróficos y una ruptura en el marmolado, en apoyo de las ideas de respuestas de umbral al enriquecimiento. Core P aumentó constantemente en la década de 1990, cuando se produjeron transiciones rápidas a la ecología de los lagos pelágicos poco profundos y Cunswick Tarn se volvió biológicamente no identificable como un lago de marga. La P total moderada a la que se produjeron estos cambios sugiere una alta sensibilidad de los lagos de marga a la eutrofización. Además, el registro inicial desafía las ideas de correlación entre la condición ecológica, la biomasa de carófitos y el sedimento Ca. En cambio, se infirió una baja producción bentónica, cobertura de macrófitos y sedimentación de Ca. Las medidas de gestión deben centrarse en reducir las cargas externas de nutrientes y sedimentos en las primeras etapas del impacto para preservar los lagos de marga. Eutrophication is the most pressing threat to highly calcareous (marl) lakes in Europe. Despite their unique chemistry and biology, comprehensive studies into their unimpacted conditions and eutrophication responses are underrepresented in conservation literature. A multi-indicator palaeolimnological study spanning ca 1260 to 2009 was undertaken at Cunswick Tarn (UK), a small, presently eutrophic marl lake, in order to capture centennial timescales of impact. Specific aims were to 1) establish temporal patterns of change (gradual/abrupt) across biological groups, thereby testing theories of resistance of marl lake benthic communities to enrichment, and 2) compare the core record of reference condition with prevailing descriptions of high ecological status. Analyses of sediment calcium (Ca), phosphorus (P), pigments, diatoms, testate amoebae, cladocerans, and macrofossils, revealed three abrupt changes in ecosystem structure. The first (1900s), with biomass increases in charophytes and other benthic nutrient-poor indicators, supported ideas of resistance to eutrophication in Chara lakes. The second transition (1930s), from charophyte to angiosperm dominance, occurred alongside reductions in macrophyte cover, increases in eutrophic indicators, and a breakdown in marling, in support of ideas of threshold responses to enrichment. Core P increased consistently into the 1990s when rapid transitions into pelagic shallow lake ecology occurred and Cunswick Tarn became biologically unidentifiable as a marl lake. The moderate total P at which these changes occurred suggests high sensitivity of marl lakes to eutrophication. Further, the early record challenges ideas of correlation between ecological condition, charophyte biomass and sediment Ca. Instead, low benthic production, macrophyte cover, and Ca sedimentation, was inferred. Management measures must focus on reducing external nutrient and sediment loads at early stages of impact in order to preserve marl lakes. التغذي بالمغذيات هو التهديد الأكثر إلحاحًا للبحيرات الجيرية للغاية (المارل) في أوروبا. على الرغم من كيمياءها وبيولوجيتها الفريدة، فإن الدراسات الشاملة حول ظروفها غير المتأثرة واستجاباتها للمغذيات ممثلة تمثيلاً ناقصًا في أدبيات الحفظ. تم إجراء دراسة متعددة المؤشرات للحفريات تمتد من عام 1260 إلى عام 2009 في كونسويك تارن (المملكة المتحدة)، وهي بحيرة مارل صغيرة مغذية في الوقت الحاضر، من أجل التقاط الجداول الزمنية المئوية للتأثير. كانت الأهداف المحددة هي 1) إنشاء أنماط زمنية للتغيير (تدريجية/مفاجئة) عبر المجموعات البيولوجية، وبالتالي اختبار نظريات مقاومة مجتمعات قاع بحيرة مارل للتخصيب، و 2) مقارنة السجل الأساسي للحالة المرجعية مع الأوصاف السائدة للوضع البيئي العالي. كشفت تحليلات الكالسيوم الرسوبي (Ca)، والفوسفور (P)، والأصباغ، والدياتومات، والأميبات الخصية، والكلادوسيرانات، والحفريات الكبيرة، عن ثلاثة تغييرات مفاجئة في بنية النظام البيئي. الأولى (1900s)، مع زيادة الكتلة الحيوية في النبات النباتي وغيرها من المؤشرات الفقيرة بالمغذيات القاعية، دعمت أفكار مقاومة المغذيات في بحيرات شارا. حدث الانتقال الثاني (1930s)، من النبات النباتي إلى هيمنة كاسيات البذور، جنبًا إلى جنب مع الانخفاضات في غطاء النبات الضخم، والزيادات في المؤشرات المغذية، والانهيار في الرخام، لدعم أفكار استجابات العتبة للإثراء. ازدادت النواة P باستمرار في التسعينيات عندما حدثت تحولات سريعة إلى بيئة البحيرة السطحية الضحلة وأصبح كونزويك تارن غير معروف بيولوجيًا كبحيرة مارل. يشير إجمالي P المعتدل الذي حدثت فيه هذه التغييرات إلى حساسية عالية لبحيرات المارل تجاه المغذيات. علاوة على ذلك، يتحدى السجل المبكر أفكار العلاقة بين الحالة البيئية والكتلة الحيوية للنباتات والرسوبيات. وبدلاً من ذلك، تم الاستدلال على الإنتاج القاعي المنخفض، وغطاء النباتات الكبيرة، وترسيب الكالسيوم. يجب أن تركز تدابير الإدارة على تقليل أحمال المغذيات والرواسب الخارجية في المراحل المبكرة من التأثير من أجل الحفاظ على بحيرات المرل.