102 research outputs found

    Basin-specific changes in filamentous cyanobacteria community composition across four decades in the Baltic Sea

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    Almost every summer, dense blooms of filamentous cyanobacteria are formed in the Baltic Sea. These blooms may cause problems for tourism and ecosystem services, where surface accumulations and beach fouling are commonly occurring. Future changes in environmental drivers, including climate change and other anthropogenic disturbances, may further enhance these problems. By compiling monitoring data from countries adjacent to the Baltic Sea, we present spatial and temporal genus-specific distribution of diazotrophic filamentous cyanobacteria (Nostocales) during four decades (1979–2017). While the summer surface salinity decreased with a half up to one unit, the surface temperature in July-August increased with 2–3 °C in most sub-basins of the Baltic Sea, during the time period. The biovolumes of the toxic Nodularia spumigena did not change in any of the sub-basins during the period. On the other hand, the biovolume of the non-toxic Aphanizomenon sp. and the potentially toxic Dolichospermum spp. increased in the northern parts of the Baltic Sea, along with the decreased salinity and elevated temperatures, but Aphanizomenon sp. decreased in the southern parts despite decreased salinity and increased temperatures. These contradictory changes in biovolume of Aphanizomenon sp. between the northern and southern parts of the Baltic Sea may be due to basin-specific effects of the changed environmental conditions, or can be related to local adaptation by sub-populations of the genera. Overall, this comprehensive dataset presents insights to genus-specific bloom dynamics by potentially harmful diazotrophic filamentous cyanobacteria in the Baltic Sea. Highlights • Biovolumes of bloom-forming cyanobacteria during four decades in the Baltic Sea. • Aphanizomenon sp. has increased with decreased salinity in the Bothnian Sea. • Dolichospermum spp. has increased with temperature in Bothnian Sea. • The total biovolume of Nostocales has decreased in the Southern Baltic Proper. • The biovolume of the toxic Nodularia spumigena has not changed since the 1980s

    The Effect of Optical Properties on Secchi Depth and Implications for Eutrophication Management

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    Successful management of coastal environments requires reliable monitoring methods and indicators. Besides Chlorophyll-a concentration (Chl-a), water transparency measured as Secchi Depth (ZSD) is widely used in Baltic Sea management for water quality assessment as eutrophication indicator. However, in many coastal waters not only phytoplankton but also colored dissolved organic matter (CDOM) and suspended particulate matter (SPM) influence the under-water light field, and therefore the ZSD. In this study all three main optical variables (CDOM, Chl-a, and SPM [organic and inorganic]) as well as ZSD were measured in three Swedish regions: the Bothnian Sea, the Baltic Proper, and the Skagerrak in 2010–2014. Regional multiple regressions with Chl-a, CDOM, and inorganic SPM as predictors explained the variations in ZSD well (Radj2 = 0.53–0.84). Commonality analyses of the regressions indicated considerable differences between regions regarding the contribution of each factor to the variance, Radj2, in ZSD. CDOM explained most of the variance in the Bothnian Sea and the Skagerrak; in general, Chl-a contributed only modestly to the ZSD variance. In the Baltic Proper the largest contribution was from the interaction of all three variables. As expected, the link between Chl-a and ZSD was much weaker in the Bothnian Sea with high CDOM absorption and SPM concentration. When applying the Swedish EU Water Framework Directive threshold for Good/Moderate Chl-a status in the models it was shown that ZSD is neither a sufficient indicator for eutrophication, nor for changes in Chl-a. Natural coastal gradients in CDOM and SPM influence the reference conditions for ZSD and other eutrophication indicators, such as the depth distribution of macro-algae. Hence, setting targets for these indicators based on reference Chl-a concentrations and simple Chl-a to ZSD relationships might in some cases be inappropriate and misleading due to overestimation of water transparency under natural conditions

    GlobalHAB - the International SCOR-IOC Science Program on Harmful Algal Blooms. Activities 2020-2021 and Plans for 2021-2022

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    The partial renovation took place on May 2020. It was conducted virtually due to the Covid-19 pandemic. Since then, all the communication has been conducted by email and virtual meetingsThe GlobalHAB Scientific Steering Committee (SSC) acknowledges the financial and logistic support received from SCOR and IOC during the 2020-2021 period and for the activities postponed to 2022 due to the Covid-19 pandemicsPeer reviewe

    GlobalHAB : a new program to promote international research, observations, and modeling of harmful algal blooms in aquatic systems

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    From 1998 to 2013, the international community of scientists researching harmful algal blooms (HABs) in marine systems worked through the Intergovernmental Oceanographic Commission (IOC) of UNESCO and the Scientific Committee on Oceanic Research (SCOR) to better understand the ecological and oceanographic controls on these natural events that cause harm to humans and ecosystems. During this period, IOC and SCOR cosponsored the Global Ecology and Oceanography of Harmful Algal Blooms (GEOHAB) program to facilitate progress in HAB research, observations, and modeling. In 2016, building on the foundation provided by GEOHAB, IOC and SCOR launched a new HAB project design to extend research into freshwater systems and address several topics related to the effects of HABs on human society now and in a rapidly changing world

    Harmful algal blooms and their effects in coastal seas of Northern Europe

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    Highlights • Fish mortalities due to harmful algae cause substantial economic and social costs for the fish farming industry in the northeastern Atlantic, North Sea and adjacent European waters • Toxin syndromes associated with Diarrhetic Shellfish Toxins and Paralytic Shellfish Toxins and their regulation have the most profound effect on the bivalve aquaculture industry in the northeastern Atlantic region • Cyanobacteria and cyanotoxins are mainly problems in brackish water areas, particularly in the Baltic Sea • Emerging threats to the shellfish and finfish industries include the known presence of the phycotoxins azaspiracids and goniodomins • The IOC-ICES-PICESHAEDAT contains time-series baseline information on harmful algal events in EuropeHarmful algal blooms (HAB) are recurrent phenomena in northern Europe along the coasts of the Baltic Sea, Kattegat-Skagerrak, eastern North Sea, Norwegian Sea and the Barents Sea. These HABs have caused occasional massive losses for the aquaculture industry and have chronically affected socioeconomic interests in several ways. This status review gives an overview of historical HAB events and summarises reports to the Harmful Algae Event Database from 1986 to the end of year 2019 and observations made in long term monitoring programmes of potentially harmful phytoplankton and of phycotoxins in bivalve shellfish. Major HAB taxa causing fish mortalities in the region include blooms of the prymnesiophyte Chrysochromulina leadbeateri in northern Norway in 1991 and 2019, resulting in huge economic losses for fish farmers. A bloom of the prymesiophyte Prymnesium polylepis (syn. Chrysochromulina polylepis) in the Kattegat-Skagerrak in 1988 was ecosystem disruptive. Blooms of the prymnesiophyte Phaeocystis spp. have caused accumulations of foam on beaches in the southwestern North Sea and Wadden Sea coasts and shellfish mortality has been linked to their occurrence. Mortality of shellfish linked to HAB events has been observed in estuarine waters associated with influx of water from the southern North Sea. The first bloom of the dictyochophyte genus Pseudochattonella was observed in 1998, and since then such blooms have been observed in high cell densities in spring causing fish mortalities some years. Dinoflagellates, primarily Dinophysis spp., intermittently yield concentrations of Diarrhetic Shellfish Toxins (DST) in blue mussels, Mytilus edulis, above regulatory limits along the coasts of Norway, Denmark and the Swedish west coast. On average, DST levels in shellfish have decreased along the Swedish and Norwegian Skagerrak coasts since approximately 2006, coinciding with a decrease in the cell abundance of D. acuta. Among dinoflagellates, Alexandrium species are the major source of Paralytic Shellfish Toxins (PST) in the region. PST concentrations above regulatory levels were rare in the Skagerrak-Kattegat during the three decadal review period, but frequent and often abundant findings of Alexandrium resting cysts in surface sediments indicate a high potential risk for blooms. PST levels often above regulatory limits along the west coast of Norway are associated with A. catenella (ribotype Group 1) as the main toxin producer. Other Alexandrium species, such as A. ostenfeldii and A. minutum, are capable of producing PST among some populations but are usually not associated with PSP events in the region. The cell abundance of A. pseudogonyaulax, a producer of the ichthyotoxin goniodomin (GD), has increased in the Skagerrak-Kattegat since 2010, and may constitute an emerging threat. The dinoflagellate Azadinium spp. have been unequivocally linked to the presence of azaspiracid toxins (AZT) responsible for Azaspiracid Shellfish Poisoning (AZP) in northern Europe. These toxins were detected in bivalve shellfish at concentrations above regulatory limits for the first time in Norway in blue mussels in 2005 and in Sweden in blue mussels and oysters (Ostrea edulis and Crassostrea gigas) in 2018. Certain members of the diatom genus Pseudo-nitzschia produce the neurotoxin domoic acid and analogs known as Amnesic Shellfish Toxins (AST). Blooms of Pseudo-nitzschia were common in the North Sea and the Skagerrak-Kattegat, but levels of AST in bivalve shellfish were rarely above regulatory limits during the review period. Summer cyanobacteria blooms in the Baltic Sea are a concern mainly for tourism by causing massive fouling of bathing water and beaches. Some of the cyanobacteria produce toxins, e.g. Nodularia spumigena, producer of nodularin, which may be a human health problem and cause occasional dog mortalities. Coastal and shelf sea regions in northern Europe provide a key supply of seafood, socioeconomic well-being and ecosystem services. Increasing anthropogenic influence and climate change create environmental stressors causing shifts in the biogeography and intensity of HABs. Continued monitoring of HAB and phycotoxins and the operation of historical databases such as HAEDAT provide not only an ongoing status report but also provide a way to interpret causes and mechanisms of HABs

    On Imprimitive Representations of Finite Reductive Groups in Non-defining Characteristic

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    In this paper, we begin with the classification of Harish-Chandra imprimitive representations in non-defining characteristic. We recall the connection of this problem to certain generalizations of Iwahori-Hecke algebras and show that Harish-Chandra induction is compatible with the Morita equivalence by Bonnaf\'{e} and Rouquier, thus reducing the classification problem to quasi-isolated blocks. Afterwards, we consider imprimitivity of unipotent representations of certain classical groups. In the case of general linear and unitary groups, our reduction methods then lead to results for arbitrary Lusztig series

    GlobalHAB (IOC-UNESCO and SCOR): Latinamerica contribution to the international coordination for sound knowledge of HABs to manage their impacts

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    12th International Phycological CongressThe Global Harmful Algal Blooms (GlobalHAB, www.global hab.info) Program is aimed at fostering international cooperative research directed toward improving the prediction of harmful algal bloom (HAB) events in aquatic ecosystems, and providing sound knowledge for policy- and decision-making to manage and mitigate HAB impacts in a changing planet. GlobalHAB is sponsored by the Intergovernmental Oceanographic Commission (IOC) of UNESCO and the Scientific Committee on Oceanic Research (SCOR). GlobalHAB was launched in 2016 and will last for 10 years. The GlobalHAB scientific objectives are focused on the research of taxonomic, ecological and toxicology knowledge gaps, on the effects of climate change on HABs and their biogeographic distribution, the implementation of HABs observing systems, and overall, to promote aquatic food and water safety and security. The GlobalHAB program has an international nature, and collaborates with international entities and programs that share objectives on HABs research, management and mitigation, as was already done by the former program GEOHAB. In particular, scientists from Latin America were active participants in GEOHAB and today Latin America is key in the implementation of GlobalHAB. Extreme HAB events affecting aquaculture sites and natural environments, Sargassum beachings, HABs monitoring programs, ciguatera fish poisoning, toxin transfer through the food webs, are examples of topics where scientists in Latin America are very active and thus, contribute to the implementation of GlobalHAB. Scientists are invited to participate in GlobalHAB by designing and endorsing scientific activities linked to the goals of GlobalHAB, and by participating in other international activitiesThe GlobalHAB (www.globalhab.info) international program is funded by IOC UNESCO and SCORPeer reviewe
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