Alexandrium fundyense cyst viability and germling survival in light vs. dark at a constant low temperature

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 103 (2014): 112–119, doi:10.1016/j.dsr2.2013.05.010.Both observations and models suggest that large-scale coastal blooms of Alexandrium fundyense in the Gulf of Maine are seeded by deep-bottom cyst accumulation zones (“seed beds”) where cysts germinate from the sediment surface or the overlying near-bottom nepheloid layers at water depths exceeding 100 m. The germling cells and their vegetative progeny are assumed to be subject to modest mortality while in complete darkness as they swim to illuminated surface waters. To test the validity of this assumption we investigated in the laboratory cyst viability and the survival of the germling cells and their vegetative progeny during prolonged exposure to darkness at a temperature of 6°C, simulating the conditions in deep Gulf of Maine waters. We isolated cysts from bottom sediments collected in the Gulf of Maine under low red light and incubated them in 96-well tissue culture-plates in culture medium under a 10:14h light: dark cycle and under complete darkness. Cyst viability was high, with excystment frequency reaching 90% in the illuminated treatment after 30 days and in the dark treatment after 50 days. Average germination rates were 0.062 and 0.038 d-1 for light and dark treatments, respectively. The dark treatment showed an approximately two-week time lag in maximum germination rates when compared to the light treatment. Survival of germlings was considerably lower in the dark treatment. In light treatments, 47% of germinated cysts produced germlings that were able to survive for 7 days and produce vegetative progeny, i.e. there were live cells in the well along with an empty cyst at least once during the experiment. In the dark treatments 12% of cysts produced germlings that were able to survive. When dark treatments are scaled to take into account non-darkness related mortality, approximately 28% of cysts produced germlings that were able to survive for at least 7 days. Even though cysts are able to germinate in darkness, the lack of illumination considerably reduces survival rate of germling cells. In addition to viability of cysts in surface sediments and the near-bottom nepheloid layer, survivability of germling cells and their vegetative progeny at aphotic depths is an important consideration in assessing the quantitative role of deep-coastal cyst seed beds in bloom formation.E. Vahtera was funded by the Academy of Finland (grant #130934) and B. Gomez-Crespo was supported by a Xunta de Galicia Ángeles Alvariño fellowship. Additional funding support was also provided by the National Oceanic Atmospheric Administration ECOHAB program through grants NA06NOS4780245 and NA09NOS4780193 and from National Science Foundation grants OCE- 0430724 and OCE-0911031 and National Institute of Environmental Health Sciences grant 1P50- ES01274201 through the Woods Hole Center for Oceans and Human Health

Alexandrium fundyense cyst viability and germling survival in light vs. dark at a constant low temperature

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Elsevier for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part II: Topical Studies in Oceanography 103 (2014): 112–119, doi:10.1016/j.dsr2.2013.05.010.Both observations and models suggest that large-scale coastal blooms of Alexandrium fundyense in the Gulf of Maine are seeded by deep-bottom cyst accumulation zones (“seed beds”) where cysts germinate from the sediment surface or the overlying near-bottom nepheloid layers at water depths exceeding 100 m. The germling cells and their vegetative progeny are assumed to be subject to modest mortality while in complete darkness as they swim to illuminated surface waters. To test the validity of this assumption we investigated in the laboratory cyst viability and the survival of the germling cells and their vegetative progeny during prolonged exposure to darkness at a temperature of 6°C, simulating the conditions in deep Gulf of Maine waters. We isolated cysts from bottom sediments collected in the Gulf of Maine under low red light and incubated them in 96-well tissue culture-plates in culture medium under a 10:14h light: dark cycle and under complete darkness. Cyst viability was high, with excystment frequency reaching 90% in the illuminated treatment after 30 days and in the dark treatment after 50 days. Average germination rates were 0.062 and 0.038 d-1 for light and dark treatments, respectively. The dark treatment showed an approximately two-week time lag in maximum germination rates when compared to the light treatment. Survival of germlings was considerably lower in the dark treatment. In light treatments, 47% of germinated cysts produced germlings that were able to survive for 7 days and produce vegetative progeny, i.e. there were live cells in the well along with an empty cyst at least once during the experiment. In the dark treatments 12% of cysts produced germlings that were able to survive. When dark treatments are scaled to take into account non-darkness related mortality, approximately 28% of cysts produced germlings that were able to survive for at least 7 days. Even though cysts are able to germinate in darkness, the lack of illumination considerably reduces survival rate of germling cells. In addition to viability of cysts in surface sediments and the near-bottom nepheloid layer, survivability of germling cells and their vegetative progeny at aphotic depths is an important consideration in assessing the quantitative role of deep-coastal cyst seed beds in bloom formation.E. Vahtera was funded by the Academy of Finland (grant #130934) and B. Gomez-Crespo was supported by a Xunta de Galicia Ángeles Alvariño fellowship. Additional funding support was also provided by the National Oceanic Atmospheric Administration ECOHAB program through grants NA06NOS4780245 and NA09NOS4780193 and from National Science Foundation grants OCE- 0430724 and OCE-0911031 and National Institute of Environmental Health Sciences grant 1P50- ES01274201 through the Woods Hole Center for Oceans and Human Health

Polycyclic aromatic hydrocarbon sorption and bacterial community composition of biodegradable and conventional plastics incubated in coastal sediments

Resistant to degradation, plastic litter poses a long-term threat to marine ecosystems. Biodegradable materials have been developed to replace conventional plastics, but little is known of their impacts and degradation in marine environments. A 14-week laboratory experiment was conducted to investigate the sorption of polycyclic aromatic hydrocarbons (PAHs) to conventional (polystyrene PS and polyamide PA) and bio-based, biodegradable plastic films (cellulose acetate CA and poly-L-lactic acid PLLA), and to examine the composition of bacterial communities colonizing these materials. Mesoplastics (1 cm(2)) of these materials were incubated in sediment and seawater collected from two sites in the Gulf of Finland, on the coast of the highly urbanized area of Helsinki, Finland. PS sorbed more PAHs than did the other plastic types at both sites, and the concentration of PAHs was consistently and considerably smaller in plastics than in the sediment. In general, the plastic bacterial biofilms resembled those in the surrounding media (water and/or sediment). However, in the sediment incubations, the community composition on CA diverged from that of the other three plastic types and was enriched with Bacteroidia and potentially cellulolytic Spirochaetia at both sites. The results indicate that certain biodegradable plastics, such as CA, may harbour potential bioplastic-degrading communities and that PAH sorption capacity varies between polymer types. Since biodegradable plastics are presented as replacements for conventional plastics in applications with risk of ending up in the marine environment, the results highlight the need to carefully examine the environmental behaviour of each biodegradable plastic type before they are extensively introduced to the market. (C) 2020 The Author(s). Published by Elsevier B.V.peerReviewe

Fosforin merkitys kukintoja muodostavien ja typpeä sitovien syanobakteerien esiintymistä säätelevänä tekijänä

Eutrophication favours harmful algal blooms worldwide. The blooms cause toxic outbreaks and deteriorated recreational and aesthetic values, causing both economic loss and illness or death of humans and animals. The Baltic Sea is the world s only large brackish water habitat with recurrent blooms of toxic cyanobacteria capable of biological fixation of atmospheric nitrogen gas. Phosphorus is assumed to be the main limiting factor, along with temperature and light, for the growth of these cyanobacteria. This thesis evaluated the role of phosphorus nutrition as a regulating factor for the occurrence of nitrogen-fixing cyanobacteria blooms in the Baltic Sea, utilising experimental laboratory and field studies and surveys on varying spatial scales. Cellular phosphorus sources were found to be able to support substantial growth of the two main bloom forming species Aphanizomenon sp. and Nodularia spumigena. However, N. spumigena growth seemed independent of phosphorus source, whereas, Aphanizomenon sp. grew best in a phosphate enriched environment. Apparent discrepancies with field observations and experiments are explained by the typical seasonal temperature dependent development of Aphanizomenon sp. and N. spumigena biomass allowing the two species to store ambient pre-bloom excess phosphorus in different ways. Field experiments revealed natural cyanobacteria bloom communities to be predominantly phosphorus deficient during blooms. Phosphate additions were found to increase the accumulation of phosphorus relatively most in the planktonic size fraction dominated by the nitrogen-fixing cyanobacteria. Aphanizomenon sp. responded to phosphate additions whereas the phosphorus nutritive status of N. spumigena seemed independent of phosphate addition. The seasonal development of phosphorus deficiency is different for the two species with N. spumigena showing indications of phosphorus deficiency during a longer time period in the open sea. Coastal upwelling introduces phosphorus to the surface layer during nutrient deficient conditions in summer. The species-specific ability of Aphanizomenon sp. and N. spumigena to utilise phosphate enrichment of the surface layer caused by coastal upwelling was clarified. Typical bloom time vertical distributions of biomass maxima were found to render N. spumigena more susceptible to advection by surface currents caused by coastal upwellings. Aphanizomenon sp. populations residing in the seasonal thermocline were observed to be able to utilise the phosphate enrichment and a bloom was produced with a two to three week time lag subsequent to the relaxation of upwelling. Consistent high concentrations of dissolved inorganic phosphorus, caused by persistent internal loading of phosphorus, was found to be the main source of phosphorus for large-scale pelagic blooms. External loads were estimated to contribute with only a fraction of available phosphorus for open sea blooms. Remineralization of organic forms of phosphorus along with vertical mixing to the permanent halocline during winter set the level of available phosphorus for the next growth season. Events such as upwelling are important in replenishing phosphate concentrations during the nutrient deplete growth season. Autecological characteristics of the two main bloom forming species favour Aphanizomenon sp. populations in utilising the abundant excess phosphate concentrations and phosphate pulses mediated through upwelling. Whilst, N. spumigena displays predominant phosphorus limited growth mode and relies on more scarce cellular phosphorus stores and presumably dissolved organic phosphorus compounds for growth. The Baltic Sea is hypothesised to be in an inhibited state of recovery due to the extensive historical external nutrient loading, extensive internal phosphorus loading and the substantial nitrogen load caused by cyanobacteria nitrogen fixation. This state of the sea is characterised as a vicious circle .Rehevöityminen suosii haitallisia leväkukintoja. Haitalliset leväkukinnot aiheuttavat myrkytystapauksia ja haittaavat vesistöjen hyöty- ja vapaa-ajankäyttöä johtaen taloudellisiin menetyksiin, ihmisten ja eläinten sairastumisiin ja jopa kuolemiin. Itämeri on maailman ainoa suuri murtovesiallas, jossa esiintyy toistuvia myrkyllisten ja ilmakehän typpeä sitovien syanobakteerien muodostamia kukintoja. Fosfori-ravinteen oletetaan olevan pääasiallinen syanobakteerien kasvua rajoittava tekijä lämpötilan ja valon ohella. Väitöskirjassa arvioidaan fosforin merkitystä myrkyllisten ja typpeä sitovien syanobakteerien kukintoja säätelevänä tekijänä. Solunsisäisesti varastoidun fosforin todettiin olevan tärkeä fosforin lähde kukintoja muodostaville lajeille (Aphanizomenon sp. ja Nodularia spumigena). Koeolosuhteissa N. spumigena -lajin kasvun todettiin kuitenkin olevan riippumattomampi tutkituista fosforin lähteistä, kun taas Aphanizomenon sp. laji kasvoi paremmin runsasfosforisessa ympäristössä. Tulokset ovat ristiriidassa aiempien kenttähavaintojen sekä kokeiden kanssa. Ristiriidat selitetään kyseisten lajien lämpötilasta riippuvien kasvunopeuksien eroilla, mikä johtaa siihen että luonnon oloissa Aphanizomenon sp. pystyy varastoimaan huomattavasti enemmän fosforia soluihinsa ennen varsinaista kasvukautta. Täten koe- ja luonnonoloista saatujen tulosten suora vertailu hankaloituu. Kenttäkokeet osoittivat kukintayhteisöjen olevan pääasiallisesti fosforivajeisia. Lisätyn fosfaatti-fosforiravinteen todettiin parantavan Aphanizomenon sp. -lajin fosforiravitsemustilaa. N. spumigena laji ei puolestaan vaikuttanut pystyvän hyötymään tämänkaltaisesta hetkellisestä lisäyksestä. N. spumigena lajilla huomattiin myös pitkäkestoisempaa ja voimakkaampaa fosforivajetta kasvukauden aikana. Luonnossa rannikonläheisellä kumpuamisella on tärkeä rooli leväkukintojen muodostumisessa, sillä sen mukana meren pintakerrokseen nousee kesäisin lisää fosforia, jonka normaalisti hyvin alhainen määrä on voimakkaimmin syanobakteerien ja levien kasvua rajoittava tekijä. Aphanizomenon sp. ja N. spumigena lajit kuitenkin eroavat kyvyissään hyödyntää tätä fosforilisää. Usein havaittu kukintojenaikainen lajeille ominainen pystysuuntainen populaatioden jakauma aiheuttaa sen että N. spumigena laji työntyy pois kumpuamisalueilta ja syvemmällä viihtyvä Aphanizomenon sp. laji siirtyy pintaan nousevan ravinteikkaan veden myötä. Aphanizomenon sp. lajin huomattiin pystyvän hyödyntämään kumpuamisen tuoma fosfaatti-fosforin lisä. Kasvu on hidasta kumpuamisen aiheuttamasta matalasta pintavesilämpötilasta johtuen ja kukinnot muodostuvat täten noin kahden viikon viiveellä kumpuamisen lakattua. Sisäisen kuormituksen aiheuttaman korkean liuenneen epäorgaanisen fosforin määrän todettiin olevan pääasiallinen fosforinlähde laajoille avoimella merellä esiintyville kukinnoille. Ulkoisen kuormituksen merkitys fosforin lähteenä kukinnoille todettiin olevan vähäinen. Orgaanisten fosforiyhdisteiden luonnollinen hajoaminen fosfaatti-fosforiksi syksyisin sekä talvisin tapahtuvan pystysuuntaisen sekoittumisen todettiin olevan tärkeimmät tekijät, jotka asettavat saatavilla olevan fosfaatin määrän perustason seuraavaa kasvukautta varten. Kesällä tapahtuvien kumpuamisten todettiin olevan tärkeä tekijä fosforin kulkeutumisessa pintakerrokseen. Lajille ominaisista piirteistä johtuen, Aphanizomenon sp. laji hyötyy N. spumigena lajia enemmän talven ja kevään korkeista fosfaatti-fosforipitoisuuksista sekä kumpuamisen kautta tulevasta lisästä. N. spumigena lajin kasvu on fosforivajeisempaa ja sen pääasialliset fosforinlähteet vaikuttavat olevan solunsisäiset varastot sekä orgaaniset fosforiyhdisteet. Itämeren voidaan todeta olevan rehevöitymisen suhteen tilassa josta palautuminen parempaan on estynyt. Tämä johtuu pitkäkestoisesta ulkoisesta ravinteiden kuormituksesta, voimakkaasta fosforin sisäisestä kuormituksesta sekä typpeä sitovien syanobakteerien aiheuttamasta suuresta typpilisästä. Tätä tilaa luonnehditaan eräänlaisena rehevöitymisen aiheuttamana noidankehänä

Alexandrium fundyense cyst viability and germling survival in light vs. dark at a constant low temperature

Special issue Harmful Algae in the Gulf of Maine: Oceanography, Population Dynamics, and Toxin Transfer in the Food Web.-- 8 pages, 4 figures, 2 tablesBoth observations and models suggest that large-scale coastal blooms of Alexandrium fundyense in the Gulf of Maine are seeded by deep-bottom cyst accumulation zones (“seed beds”) where cysts germinate from the sediment surface or the overlying near-bottom nepheloid layers at water depths exceeding 100 m. The germling cells and their vegetative progeny are assumed to be subject to mortality while in complete darkness, as they swim to illuminated surface waters. To test the validity of this assumption we conducted laboratory investigations of cyst viability and the survival of the germling cells and their vegetative progeny during prolonged exposure to darkness at a temperature of 6 °C, simulating the conditions in deep Gulf of Maine waters. We isolated cysts from bottom sediments collected in the Gulf of Maine under low red light and incubated them in 96-well tissue culture-plates in culture medium under a 10:14 h light:dark cycle and under complete darkness. Cyst viability was high, with excystment frequency reaching 90% in the illuminated treatment after 30 days and in the dark treatment after 50 days. Average germination rates were 0.062 and 0.038 d−1 for light and dark treatments, respectively. The dark treatment showed an approximately 2-week time lag in maximum germination rates compared to the light treatment. Survival of germlings was considerably lower in the dark treatment. In the light treatments, 47% of germinated cysts produced germlings that were able to survive for 7 days and produce vegetative progeny, i.e., there were live cells in the well along with an empty cyst at least once during the experiment. In the dark treatments 12% of the cysts produced germlings that were able to survive for the same length of time. When dark treatments are scaled to take into account non-darkness related mortality, approximately 28% of the cysts produced germlings that were able to survive for at least 7 days. Even though cysts are able to germinate in darkness, the lack of illumination considerably reduces survival rate of germling cells. In addition to viability of cysts in surface sediments and the near-bottom nepheloid layer, survivability of germling cells and their vegetative progeny at aphotic depths is an important consideration in assessing the quantitative role of deep-coastal cyst seed beds in bloom formationE. Vahtera was funded by the Academy of Finland (Grant no. 130934) and B. Gomez-Crespo was supported by a Xunta de Galicia Ángeles Alvariño fellowship. Additional funding support was also provided by the National Oceanic Atmospheric Administration ECOHAB program through grants NA06NOS4780245 and NA09NOS4780193, and from National Science Foundation grants OCE-0430724, OCE-0911031, OCE-1314642 and National Institute of Environmental Health Sciences grants1P50-ES01274201 and 1P01ES021923-01 through the Woods Hole Center for Oceans and Human HealthPeer Reviewe

Upwelling events, coastal offshore exchange, links to biogeochemical processes - Highlights from the Baltic Sea Science Congress

The Baltic Sea Science Congress was held at Rostock University, Germany, from 19 to 22 March 2007. In the session entitled"Upwelling events, coastal offshore exchange, links to biogeochemical processes" 20 presentations were given,including 7 talks and 13 posters related to the theme of the session.This paper summarises new findings of the upwelling-related studies reported in the session. It deals with investigationsbased on the use of in situ and remote sensing measurements as well as numerical modelling tools. The biogeochemicalimplications of upwelling are also discussed.Our knowledge of the fine structure and dynamic considerations of upwelling has increased in recent decades with the advent ofhigh-resolution modern measurement techniques and modelling studies. The forcing and the overall structure, duration and intensity ofupwelling events are understood quite well. However, the quantification of related transports and the contribution to the overall mixingof upwelling requires further research. Furthermore, our knowledge of the links between upwelling and biogeochemical processes is stillincomplete. Numerical modelling has advanced to the extent that horizontal resolutions of c. 0.5 nautical miles can now be applied,which allows the complete spectrum of meso-scale features to be described. Even the development of filaments can be describedrealistically in comparison with high-resolution satellite data.But the effect of upwelling at a basin scale and possible changes under changing climatic conditions remain open questions