1. The occurrence of the jellyfish Aequorea cf. forskalea in the Adriatic Sea : comparison of historical and recent dataAlenka Malej, Davor Lučić, Natalia Bojanić, Martin Vodopivec, Paolo Paliaga, Branka Pestorić, Ivana Violić, Nastjenjka Supić, 2022, original scientific article Abstract: Jellyfish are becoming an increasingly important component of studies of the global marine environment, as their frequent mass phenomena affect ecosystem performance and have economic and health consequences. Recent research has focused primarily on mass occurrences of scyphozoans and ctenophores, while less attention has been paid to hydromedusae blooms, which can also have significant impacts on the marine ecosystem with economic consequences. Like many members of the Scyphozoa and Ctenophora, Aequorea species can be numerous and form blooms. Based on surveys from 2000 to 2020 and information provided by marine professionals, we examine the (multiannual) variability, seasonality, and spatial distribution patterns of the poorly studied temperate species Aequorea cf. forskalea (Hydrozoa: Leptothecata). We hypothesized that this macrogelatinous jellyfish with a bipartite life cycle (benthic polyps and planktonic medusae) is sensitive to seasonal and long-term temperature fluctuations, particularly because temperature has been shown to play a critical role in mediating transitions in the life cycle of cnidarians. The cold-water affinity of A. cf. forskalea was confirmed by a significant negative correlation with temperature and the most frequent occurrence during the winter-spring period. For the northern Adriatic (Gulf of Trieste), sea temperature data and semi-quantitative plankton data are available for the first decade of the 20th century, allowing comparison of the historical data (1900-1911) with our current data set. Compared to historical records, the current occurrence of A. cf. forskalea differs significantly. With the warming of the northern Adriatic Sea since the beginning of the 20th century, the current phenology of A. cf. forskalea has changed, probably related to the delayed production of medusae by hydroids in autumn, the absence of medusae in this season and their less frequent occurrence in winter.
Keywords: hydromedusae, blooms, long-term monitoring, multiannual variability, Mediterranean Sea
Published in DiRROS: 31.07.2024; Views: 272; Downloads: 110
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2. Contrasting resource dynamics in mast years for European Beech and Oak - a continental scale analysisAnita Nussbaumer, Arthur Gessler, Sue Benham, B. De Cinti, Sophia Etzold, Morten Ingerslev, Frank Jacob, François Lebourgeois, Tom Levanič, Hrvoje Marjanović, 2021, original scientific article Abstract: Resource allocation to different plant tissues is likely to be affected by high investment into fruit production during mast years. However, there is a large knowledge gap concerning species-specific differences in resource dynamics. We investigated the influence of mast years on stem growth, leaf production, and leaf carbon (C), nitrogen (N), and phosphorus (P) concentrations and contents in Fagus sylvatica, Quercus petraea, and Q. robur at continental and climate region scales using long-term data from the International Co-operative Programme on Assessment and Monitoring of Air Pollution Effects on Forests (ICP Forests) and similar datasets. We discussed the results in the light of opposing resource dynamics hypotheses: (i) resource accumulation before mast years and exhaustion after mast years (resource storage hypothesis), (ii) shifting resources from vegetative to generative compartments (resource switching hypothesis), and (iii) investing resources concurrently in both vegetative and generative compartments (resource matching hypothesis). Linear mixed-effects modelling (LMM) showed that both stem growth and leaf production were negatively influenced by weather conditions which simultaneously lead to high fruit production. Thus, the impact of generative on vegetative growth is intermixed with effects of environmental factors. Superposed epoch analyses and LMM showed that for mast behaviour in F. sylvatica, there are indicators supporting the resource storage and the resource switching hypotheses. Before mast years, resources were accumulated, while during mast years resources switched from vegetative to generative tissues with reduced stem and leaf growth. For the Quercus species, stem growth was reduced after mast years, which supports the resource storage hypothesis. LMM showed that leaf C concentrations did not change with increasing fruit production in neither species. Leaf N and P concentrations increased in F. sylvatica, but not in Quercus species. Leaf N and P contents decreased with increasing fruit production in all species, as did leaf C content in F. sylvatica. Overall, our findings suggest different resource dynamics strategies in F. sylvatica and Quercus species, which might lead to differences in their adaptive capacity to a changing climate.
Keywords: climate change, Fagus sylvatica, long-term monitoring, mast fruiting, Quercus petraea, Quercus robur, resource dynamics
Published in DiRROS: 15.07.2021; Views: 1065; Downloads: 755
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