1,721,248 research outputs found
Depth distribution and biomass of sublittoral seaweeds at the island of Helgoland in 2005
No full textIn 2005, the species composition and spatial distribution of the seaweed community were investigated in the frame of diving surveys along a sublittoral transect in the North of Helgoland that had been investigated ~40 years earlier by Lüning (1970). The cover of dominant brown seaweeds, Fucus serratus, Sargassum muticum, Laminaria digitata, L. hyperborea and Saccharina latissima, was semi-quantitatively assessed to define vegetation zones. Within each zone, all macroalgal species were estimated quantitatively in 3 to 6 random 1 m² quadrats. Additionally, a replicated biomass survey was performed at 6 depths (0.5, 2, 4, 6, 8 and 10 m below mean low water spring tide). The survey investigated the occurrence, cover and relative frequency of the algae community and information about fresh mass and dry mass were obtained. For kelps also stipe length, blade area, blade fresh mass, age and fresh mass of epiphytes was recorded
Algal information along a transect at the island of Helgoland in 2005
No full textA sublittoral transect (P3) in the North of Helgoland that had been investigated ~40 years earlier by Lüning (1970) was traversed again. Scuba dives were carried out between 13.07.2005 and 25.08.2005. For each sampling point, time, date and coordinates were given as well as the depth in m mean low water spring tide. 0.25 m² frames were used to obtain the species composition, total fresh mass and total dry mass. In addition, 1 m² frames were used to record the kelp community by counting the individuals and measuring kelp stipe length, kelp blade area, kelp blade fresh mass, kelp age and fresh mass of epiphytes on the kelp stipes. Equal Location IDs represent the same frame
Frequency of algae along a transect at the island of Helgoland in 2005
No full textA sublittoral transect (P3) in the North of Helgoland that had been investigated ~40 years earlier by Lüning (1970) was traversed again. Scuba dives were carried out between 24.06.2005 and 19.08.2005. For each sampling point, time, date and coordinates were given as well as the corrected depth in m mean low water spring tide. Along the transect, substrate and topography were recorded. Relative frequency and cover of 32 species grown attached to the seafloor and cover of 12 epiphytic species were obtained
Variations of Fucus vesiculosus photophysiological performance in the Kiel Outdoor Benthocosms in four different seasons – relative electron transport rate and maximum quantum yield
No full textOcean warming and acidification may substantially affect the photophysiological performance of keystone species such as Fucus vesiculosus (Phaeophyceae) in shallow coastal waters. In four consecutive benthic mesocosm experiments (Kiel Outdoor Benthocosm, Kiel, Germany, 54°20'N; 10°09'E), we compared the photophysiological performance (i.e., oxygen production, in vivo chlorophyll a fluorescence, energy dissipation pathways and chlorophyll concentration) of Baltic Sea Fucus under the single and combined impact of elevated seawater temperature (Δ + 5°C) and pCO2 (1100 ppm). Fucus specimens were sampled, in each season (spring: April 2, 2013; summer: July 2, 2013; autumn: 8 October; winter: January 14, 2014) from a depth of 0.2–1 m in the Kiel Fjord (Bülk), western Baltic Sea, Germany (54°27'N; 10°11,5'E). Photosynthetic performance was measured with two different methods, one based on in vivo chlorophyll a fluorescence measurements of photosystem II (PSII), the other one based on oxygen production. For each experiment and treatment, three Fucus specimens 15–25 cm long with 91 ± 30 total apices and apparently equal vigor were chosen, each individually growing on a stone (10–15 cm in diameter) from a single holdfast. For details see material and methods in Graiff et al. 2021. Photosynthesis was highest in spring/early summer when water temperature and solar irradiance increases naturally, and was lowest in winter (December to January/February). Temperature had a stronger effect than pCO2 on photosynthetic performance of Fucus in all seasons. Photophysiological responses were generally positive during the cooler spring months, but strongly negatively affected during summer (due to a marine heat-wave). Especially, future summer temperatures exceeded the thermal tolerance threshold of western Baltic Sea Fucus and had a deleterious impact overall. Potential benefits of the combination of future ocean warming and increased pCO2 over most of the year for Fucus photophysiological performance are suggested by our study, but not during summer peak temperatures
Seasonal photophysiological responses of Fucus vesiculosus in the Kiel Outdoor Benthocosms – PI-curve parameters, non-photochemical quenching, maximum quantum yield, gross oxygen production and chlorophyll concentrations
No full textOcean warming and acidification may substantially affect the photophysiological performance of keystone species such as Fucus vesiculosus (Phaeophyceae) in shallow coastal waters. In four consecutive benthic mesocosm experiments (Kiel Outdoor Benthocosm, Kiel, Germany, 54°20'N; 10°09'E), we compared the photophysiological performance (i.e., oxygen production, in vivo chlorophyll a fluorescence, energy dissipation pathways and chlorophyll concentration) of Baltic Sea Fucus under the single and combined impact of elevated seawater temperature (Δ + 5°C) and pCO2 (1100 ppm). Fucus specimens were sampled, in each season (spring: April 2, 2013; summer: July 2, 2013; autumn: 8 October; winter: January 14, 2014) from a depth of 0.2–1 m in the Kiel Fjord (Bülk), western Baltic Sea, Germany (54°27'N; 10°11,5'E). Photosynthetic performance was measured with two different methods, one based on in vivo chlorophyll a fluorescence measurements of photosystem II (PSII), the other one based on oxygen production. For each experiment and treatment, three Fucus specimens 15–25 cm long with 91 ± 30 total apices and apparently equal vigor were chosen, each individually growing on a stone (10–15 cm in diameter) from a single holdfast. For details see material and methods in Graiff et al. 2021. Photosynthesis was highest in spring/early summer when water temperature and solar irradiance increases naturally, and was lowest in winter (December to January/February). Temperature had a stronger effect than pCO2 on photosynthetic performance of Fucus in all seasons. Photophysiological responses were generally positive during the cooler spring months, but strongly negatively affected during summer (due to a marine heat-wave). Especially, future summer temperatures exceeded the thermal tolerance threshold of western Baltic Sea Fucus and had a deleterious impact overall. Potential benefits of the combination of future ocean warming and increased pCO2 over most of the year for Fucus photophysiological performance are suggested by our study, but not during summer peak temperatures
Contrasting temperature chracteristics of Laminaria digitata and Hedophyllum nigripes - C:N-ratio, growth rate, PAM fluorometry, gametogenesis
No full textWe investigated effects of temperature on gametophytes and sporophytes of the two morphologically similar kelp species Laminaria digitata and Hedophyllum nigripes co-occurring in the Arctic. We quantified gametogenesis, sporophyte recruitment and growth, optimal quantum yield and carbon and nitrogen content of sporophytes, as well as survival of both life cycle stages along temperature gradients (0-25°C), using several unialgal strains isolated from the European Arctic in Kongsfjorden, western Spitsbergen
Seasonal variations of Fucus vesiculosus photophysiological performance (Kiel Outdoor Benthocosms)
No full textShallow coastal marine ecosystems are exposed to intensive warming events in the last decade, threatening keystone macroalgal species such as the bladder wrack (Fucus vesiculosus, Phaeophyceae) in the Baltic Sea. Herein, we experimentally tested in four consecutive benthic mesocosm experiments, if the single and combined impact of elevated seawater temperature (? + 5◦C) and pCO2 (1100 ppm) under natural irradiance conditions seasonally affected the photophysiological performance (i.e., oxygen production, in vivo chlorophyll a fluorescence, energy dissipation pathways and chlorophyll concentration) of Baltic Sea Fucus. Photosynthesis was highest in spring/early summer when water temperature and solar irradiance increases naturally, and was lowest in winter (December to January/February). Temperature had a stronger effect than pCO2 on photosynthetic performance of Fucus in all seasons. In contrast to the expectation that warmer winter conditions might be beneficial, elevated temperature conditions and sub-optimal low winter light conditions decreased photophysiological performance of Fucus. In summer, western Baltic Sea Fucus already lives close to its upper thermal tolerance limit and future warming of the Baltic Sea during summer may probably become deleterious for this species. However, our results indicate that over most of the year a combination of future ocean warming and increased pCO2 will have slightly positive effects for Fucus photophysiological performance
Occurrence and cover of algae along a transect at the island of Helgoland in 2005
No full textA sublittoral transect (P3) in the North of Helgoland that had been investigated ~40 years earlier by Lüning (1970) was traversed again. Scuba dives were carried out between 21.04.2005 and 23.06.2005. At different sampling points (Location ID: P1-P44; start with P1 every new day) along the transect, substrate and topography was recorded and every 5m occurrence and the cover was obtained of the dominant brown algae Fucus serratus, Sargassum muticum, Laminaria digitata, L. hyperborea and Saccharina latissima. The occurrence was measured qualitatively as present/absence (1/0) and the cover was estimated semi-quantitative according to the Kautsky scale as 0 for not present to 100 as 100% cover (Kautsky, 1995). Furthermore, the transect was split into different zones (1-7) depending on the algal vegetation according to the master thesis of C. Gehling (2006). For each sampling point, time, date and coordinates were given as well as the corrected depth in m mean low water spring tide
Seawater carbonate chemistry and seasonal variations of Fucus vesiculosus fertility in the western Baltic Sea
No full textOcean warming and acidification may substantially affect the reproduction of keystone species such as Fucus vesiculosus (Phaeophyceae). In four consecutive benthic mesocosm experiments, we compared the reproductive biology and quantified the temporal development of Baltic Sea Fucus fertility under the single and combined impact of elevated seawater temperature and pCO2 (1100 ppm). In an additional experiment, we investigated the impact of temperature (0–25°C) on the maturation of North Sea F. vesiculosus receptacles. A marked seasonal reproductive cycle of F. vesiculosus became apparent in the course of 1 year. The first appearance of receptacles on vegetative apices and the further development of immature receptacles of F. vesiculosus in autumn were unaffected by warming or elevated pCO2. During winter, elevated pCO2 in both ambient and warmed temperatures increased the proportion of mature receptacles significantly. In spring, warming and, to a lesser extent, elevated pCO2 accelerated the maturation of receptacles and advanced the release of gametes by up to 2 weeks. Likewise, in the laboratory, maturation and gamete release were accelerated at 15–25°C relative to colder temperatures. In summary, elevated pCO2 and/or warming do not influence receptacle appearance in autumn, but do accelerate the maturation process during spring, resulting in earlier gamete release. Temperature and, to a much lesser extent, pCO2 affect the temporal development of Fucus fertility. Thus, rising temperatures will mainly shift or disturb the phenology of F. vesiculosus in spring and summer, which may alter and/or hamper its ecological functions in shallow coastal ecosystems of the Baltic Sea
Effects of temperature and nutrient regimes on the recruitment of laminaria digitata
Full text linkKelps are important macroalgae found in the temperate rocky marine habitats along the
northern Atlantic Ocean coast. Kelp forests and its services to the ecosystem are globally at
risk due to anthropogenic activity and climate change, by altering the temperature gradient and
the nutrient input and where the kelps exist. This could be detrimental for the coming
generations of the kelp, Laminaria digitata, which is one of the major kelp species in the north
Atlantic Ocean. As of this, nutrients and temperature regimes that allow microscopic phases
for gametogenesis and survival could be at risk. As gametophyte growth and sporophyte
development have different optimal temperatures, the microscopic life phases develop at
different rates when exposed to different environmental conditions. To investigate the effects
of temperature and nutrient regimes on gametophyte growth, gametogenesis, and early
sporophyte formation of L. digitata, two populations (Bodø and Quiberon) were exposed to
four temperature regimes (4, 8, 12, 18o
C) and two nutrient treatments (high (HN) and low(LN))
based on local data from each site. Bodø represents the intermediate zone, which might provide
optimum conditions while Quiberon represent the southern distributional limit. The experiment
followed a factorial design, testing all temperatures in both nutrient conditions through a
mechanistic approach considering both sites. We hypothesized that the response of each
population shows local adaptation relating to local nutrient and temperature histories. Results
showed that the gametophytes of each population responded differently to the treatments,
especially in respect to sporophyte formation, however had similar patterns for development in
general. Sporophyte recruitment was 7% higher for the Quiberon population, however, both
populations responded positively to optimal temperatures (8 and 12o
C) in terms of ontogenetic
development. Moreover, both populations interaction with temperature were significantly
related to sporophyte recruitment, with Bodø also having a response to the nutrient treatment.
In both populations, longer periods of increased temperatures (18o
C) enhanced vegetative
gametophyte growth but inhibited sporophyte production. This study provides an insight to
how Laminaria digitata gametophytes responds to forced environmental conditions in terms
of survival, growth, and recruitment. It shows distinct differences between populations,
exhibiting local adaption based on local nutrient and temperature histories. With emphasis on
which treatments results in the optimal conditions to further knowledge on the adaptation
responses of the species to environmental conditions and climate change.Macroalgas como a Laminaria digitata, são algas importantes capazes de fornecer abrigo
e recursos a outros organismos na extensão da costa norte do Oceano Atlântico,
especificamente em habitats marinhos rochosos temperados. A atividade antropogénica e as
alterações climáticas, colocam as florestas de algas e os serviços que estas oferecem ao
ecossistema em risco a nível global ao alterar o gradiente de temperatura e a entrada de
nutrientes e onde estas existem. Isto poderá ser prejudicial para as próximas gerações de uma
espécie de algas, Laminaria digitata, a maior das algas no Oceano Atlântico Norte. Este risco
está associado ao facto de os nutrientes e os regimes de temperatura que permitem fases
microscópicas de gametogénese e sobrevivência poderem estar em risco. Em condições
desfavoráveis, os gametófitos têm o potencial de permanecer em crescimento vegetativo. Por
sua vez há um fornecimento de um banco de sementes ao fundo do oceano, à espera de
condições mais favoráveis. Além disso, em comparação com as plantas terrestres, os
gametófitos de algas carecem de cápsulas de sementes para proteção contra o stress local, sendo
assim mais suscetíveis a fatores ambientais e perturbações causadas por correntes, herbívoros,
e alterações diretas ao seu ambiente local. Algas, tais como L. digitata, possuem crescimento
de gametófitos e a formação de esporófitos através da gametogénese em intervalos de
temperatura diferentes. Isto torna as espécies vulneráveis a períodos prolongados de
temperaturas abaixo do ideal, o que pode ter um impacto nos períodos de tempo normais de
desenvolvimento e crescimento de gametófitos, e na formação de esporófitos.
Colocamos a hipótese de que a resposta de cada população mostra uma adaptação local
relacionada com o registo de ocorrência de nutrientes e temperaturas. Para investigar os efeitos
dos regimes de temperatura e nutrientes no recrutamento de L. digitata, duas populações (Bodø
e Quiberon) ao longo do gradiente de distribuição ótimo e mais meridional foram examinadas
sob um conjunto de tratamentos. Os gametófitos foram expostos a quatro regimes de
temperatura (4, 8, 12, 18o
C) e dois tratamentos de nutrientes (alto (HN) e baixo (LN)) com base
na média local dos dados do verão e inverno de cada local. A experiência seguiu um desenho
fatorial, testando todas as temperaturas em ambas as condições nutricionais através de uma
abordagem mecanicista considerando ambos os locais. Cada um dos meios nutritivos (HN e
LN) foi criado individualmente para ambas as populações, antes do início da experiência em
t0. Duas semanas antes do início do processo experimental em água do mar artificial, o material
experimental de gametófito vegetativo não foi alimentado. Este procedimento foi aplicado para
que os isolados de gametófito se esgotassem em nutrientes, a fim de examinar as concentrações de nutrientes no meio e o seu efeito no desenvolvimento e crescimento dos mesmos.
Posteriormente, para permitir que os gametófitos se aclimatassem à sua temperatura final
atribuída no dia 0, a aclimatação foi estabelecida 5 dias antes do início do processo
experimental para permitir que os gametófitos recuperassem do stress da sementeira, se
ajustassem e replicassem a criação.
Os resultados mostraram que os gametófitos de cada população responderam de forma
diferente aos tratamentos, especialmente no que diz respeito à formação de esporófitos, tendo,
no entanto, padrões semelhantes para o desenvolvimento em geral. Em Quiberon, havia
aproximadamente 20% mais machos do que fêmeas no quinto dia, enquanto que em Bodø,
havia aproximadamente 30% mais fêmeas do que machos, tornando-o um artefacto
experimental. É provável que a diferença entre a proporção de sexos entre as populações tenha
influenciado o recrutamento esporófito final no 20º dia. No entanto, a proporção entre sexos
não foi influenciada pela temperatura e condições nutricionais e não houve interação de fatores.
Todos os gametófitos apresentavam apenas uma baixa fertilidade independentemente da
temperatura e do nutriente, não ultrapassando os 20% para os gametófitos com ovos ou
esporófitos. O recrutamento de esporófitos foi 7% mais elevado para a população de Quiberon,
contudo, ambas as populações responderam positivamente às temperaturas ótimas (8 e 12o
C)
em termos de desenvolvimento ontogenético. A maioria dos esporófitos desenvolveu-se a 8 e
12°C em ambas as populações, enquanto que a 4 e 18°C, os gametófitos cresceram
vegetativamente na sua maioria. Além disso, a interação de ambas as populações com a
temperatura estava significativamente relacionada com o recrutamento de esporófitos, tendo
Bodø também uma resposta ao tratamento com nutrientes. O maior recrutamento de esporófitos
por população no 21º dia foi observado a 12o
C sob tratamento HN para Quiberon com 37
esporófitos cm2
. Enquanto que, o máximo para Bodø verificou-se a 8o
C sob tratamento de HN
com 11 esporófitos cm2
.
O crescimento do gametófito foi avaliado apenas para a população de Bodø. O
crescimento de gametófitos foi significativamente afetado pelo tratamento com nutrientes no
final (t20) da experiência: os gametófitos em tratamentos com nutrientes altos cresceram mais
do que aqueles sujeitos a tratamentos com nutrientes baixos. Os gametófitos a 18o
C HN não se
tornaram férteis, mas cresceram mais do que todos os outros gametófitos sujeitos a outros
tratamentos. Além disso, uma vez que alguns gametófitos cresceram em grande escala, levou
a que outros estivessem em decomposição, provavelmente causando a libertação adicional de
fosfato no meio de cultura e a concentrações finais do mesmo mais elevadas comparativamente
aquelas do tratamento inicial. Derivado dos tratamentos com baixos nutrientes sob temperaturas abaixo dos níveis ótimos, a densidade de gametófitos diminuiu com o tempo,
devido à sua deterioração. Os efeitos resultantes da interação população x nutriente e população
x temperatura, foram significativos para a densidade de gametófitos no 20º dia.
Adicionalmente, o tratamento de temperatura também teve um efeito significativo
independente sobre a densidade para ambas as populações. Em condições de HN, a
concentração inicial de nitrato não foi totalmente utilizada no prazo de 21 dias, sendo apenas
reduzida em cerca de 50% (de 15 para 7-12 µmol L-1
), em contraste com o fosfato, que foi
totalmente utilizado.
Períodos mais longos de aumento de temperatura (18o
C) têm o potencial de aumentar o
crescimento vegetativo de gametófitos, mas atrasam ou inibem a produção de esporófitos. As
temperaturas dentro da gama ótima (8-12o
C) para o recrutamento são cruciais para que a
espécie persista numa área ao longo do tempo. Com o aumento das temperaturas de verão e as
limitações da disponibilidade de nutrientes resultantes das flutuações locais causadas pelas
alterações climáticas, as concentrações naturais de nutrientes e as temperaturas anuais podem
ser alteradas. Isto poderá levar a que mais gametófitos permaneçam em fase vegetativa, à espera
de condições ambientais favoráveis. Assim, como as populações em foco responderam de
forma semelhante aos tratamentos de temperatura, as mudanças nas interações das espécies
com o ambiente podem ser mais proeminentes, e a sua gama de distribuição pode mudar para
fazer face às mudanças no seu ambiente. No entanto, é necessário realizar mais estudos para
aprofundar mais conhecimento e consciência sobre a forma como diferentes fatores ambientais
afetam a vida biológica e os processos de subpopulação de algas, com mudanças contínuas que
estão a ocorrer não só a nível global, mas também a nível local. Este estudo fornece uma
perspetiva de como a alga laminaria digitata responde às condições ambientais forçadas em
termos de sobrevivência, crescimento de gametófitos, desenvolvimento, recrutamento e
utilização de nutrientes. Com destaque às variantes de temperaturas e concentrações de
nutrientes que resultam em condições ótimas e abaixo de ótimas, visando aprofundar o
conhecimento sobre as respostas de adaptação das espécies às condições ambientais e às
alterações climáticas
- …
