Ulrich Sommer

Ulrich Sommer
Leibniz-Institut für Meereswissenschaften an der Universität Kiel | IFM GEOMAR · Marine Evology

About

286
Publications
95,615
Reads
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19,774
Citations
Citations since 2017
10 Research Items
7265 Citations
201720182019202020212022202302004006008001,0001,200
201720182019202020212022202302004006008001,0001,200
201720182019202020212022202302004006008001,0001,200
201720182019202020212022202302004006008001,0001,200
Additional affiliations
October 1994 - present
GEOMAR Helmholtz Centre for Ocean Research Kiel
Position
  • Professor, Head of research Unit "Experimental Ecology - Food Webs"

Publications

Publications (286)
Article
The copepod Acartia tonsa is a key component of a wide range of marine ecosystems, linking energy transfer from phytoplankton to higher trophic levels, and has a central role in productivity and biogeochemistry. The interaction of end-of-century global warming and ocean acidification scenarios with testing moderate temperature effects on a seminatu...
Article
Abstract Harmful invader ctenophore Mnemiopsis leidyi's expansions in the Eurasian Seas, its spatio-temporal population dynamics depending on environmental conditions in recipient habitats have been synthesized. M. leidyi found suitable temperature, salinity and productivity conditions in the temperate and subtropical environments of the semi-enc...
Article
Full-text available
Anthropic activities impact ecosystems worldwide thus contributing to the rapid erosion of biodiversity. The failure of traditional strategies targeting single species highlighted ecosystems as the most suitable scale to plan biodiversity management. Network analysis represents an ideal tool to model interactions in ecosystems and centrality indice...
Article
Cyanobacteria are an essential biological component of phytoplankton water quality assessment. However, there are some problems associated with the widely used everyday practices of sampling, estimation and use of cyanobacteria when calculating phytoplankton indices assessing water quality. Many indices were developed during the implementation of t...
Article
Food chains in the pelagic zones of oceans and lakes are longer than in terrestrial ecosystems. The perception of the pelagic food web has become increasingly complex by progressing from a linear food chain (phytoplankton – crustacean zooplankton – planktivorous fish – predatory fish) to a food web because of an increasing appreciation of microbial...
Article
Light and nutrients are essential resources for phytoplankton growth and considered to shape the size structure and other morphometric traits (surface:volume ratio, deviation from spherical shape) of phytoplankton communities. If morphometric traits influence the growth and resource use, shifts by one of the two factors should influence the capabil...
Article
In situ mesocosm experiments on the effect of ocean acidification (OA) are an important tool for investigating potential OA-induced changes in natural plankton communities. In this study we combined results from various in-situ mesocosm studies in two different ocean regions (Arctic and temperate waters) to reveal general patterns of plankton commu...
Article
Estuaries are among the most valuable aquatic systems by their services to human welfare. However, increasing human activities at the watershed along with the pressure of climate change are fostering the co-occurrence of multiple environmental drivers, and warn of potential negative impacts on estuaries resources. At present, no clear understanding...
Article
Climate-driven changes in environmental conditions have significant and complex effects on marine ecosystems. Variability in phytoplankton elements and biochemicals can be important for global ocean biogeochemistry and ecological functions, while there is currently limited understanding on how elemental stoichiometry and biochemicals respond to the...
Article
The abundance, biomass and the taxonomic composition of the total airborne bacterial communities in a coastal urban area of Northeastern Mediterranean Sea were examined. In total, 27 air samples were collected across three seasons from a sampling point of approximately 30 m altitude in the center of the city. The abundance and biomass were determin...
Article
Phytoplankton cell or colony sizes range from <1 µm to several cm, i.e. 4–5 orders of magnitude in linear dimensions, which is roughly equivalent to the log-size span within terrestrial vegetation. It is commonplace to assume that smaller phytoplankton have an advantage in growth related traits while larger ones are more resistant to losses. Howeve...
Article
Full-text available
Concerns about increasing atmospheric CO2 concentrations and global warming have initiated studies on the consequences of multiple-stressor interactions on marine organisms and ecosystems. We present a fully-crossed factorial mesocosm study and assess how warming and acidification affect the abundance, body size, and fatty acid composition of copep...
Data
Temporal development of (A) mean total alkalinity, (B) mean dissolved inorganic carbon DIC), and (C) temperature of each treatment. Error bars denote ± 1 SE (n = 3). Open symbols represent high pCO2 (1400 μatm) and closes symbols low pCO2 (560 μatm) concentrations. Symbols for the treatment combinations as in key. (TIFF)
Data
Magnitudes of change between treatments compared to the 9°C / 560 μatm treatment. OA (9°C / 1400 μatm), OW (ocean warming: 15°C / 560 μatm), and OW/OA (15°C / 1400 μatm). Values in bold notice significant ANOVA results (see Tables 1A, 4A and 5A) at p < 0.05. (DOCX)
Data
Fatty acid content (ng per individual) of adult female Paracalanus sp. of the last experimental day. (DOCX)
Data
Species- and stage specifically raw data abundances [individuals L-1]. (DOCX)
Data
(A) ANOVA results of correlation coefficients of phytoplankton vs zooplankton biomass. (B) Tukey Honest Significance Test results on phytoplankton vs zooplankton biomass correlation coefficients. Values in bold are significant at p <0.05. (DOCX)
Data
(A) Temporal mean biomass of edible phytoplankton [μg C * L-1] and (B) mean copepod abundance (C1-adult) [ind * L-1]. Error bars denote for ± 1 SD (n = 3). Open symbols represent high pCO2 (1400 μatm) and closes symbols low pCO2 (560 μatm) concentrations. Symbols for the treatment combinations as in key. (TIFF)
Data
Cross-correlation coefficients of phytoplankton and zooplankton biomass (see S2 Fig). (DOCX)
Article
Full-text available
Global warming has revitalized interest in the relationship between body size and temperature, proposed by Bergmann's rule 150 years ago, one of the oldest manifestations of a 'biogeography of traits'. We review biogeographic evidence, results from clonal cultures and recent micro- and mesocosm experiments with naturally mixed phytoplankton communi...
Article
In a literature search, the presence of Haematococcus in phytoplankton communities and its biogeography were investigated. Haematococcus, although showing a wide biogeographical distribution, has been rarely found in phytoplankton communities. Simultaneously, the colonization potential of air-dispersed Haematococcus in ephemeral waters and its inte...
Article
Full-text available
We investigated the impacts of predicted ocean acidification and future warming on the quantity and nutritional quality of a natural phytoplankton autumn bloom in a mesocosm experiment. Since the effects of CO2-enrichment and temperature have usually been studied independently, we were also interested in the interactive effects of both aspects of c...
Article
Full-text available
About 60 years ago, the critical depth hypothesis was proposed to describe the occurrence of spring phytoplankton blooms and emphasized the role of stratification for the timing of onset. Since then, several alternative hypotheses appeared focusing on the role of grazing and mixing processes such as turbulent convection or wind activity. Surprising...
Article
Full-text available
Cell size is one of the ecologically most important traits of phytoplankton. The cell size variation is frequently related to temperature and nutrient limitation. In order to disentangle the role of both factors, an experiment was conducted to determine the possible interactions of these factors. Baltic Sea water containing the natural plankton com...
Article
Full-text available
The combined effects of warming and densities of overwintering copepods on the spring succession of Baltic Sea plankton were investigated using indoor mesocosms. Three zooplankton densities (1.5, 4 and 10 copepods l−1) and 2 temperature levels (Δ0°C and Δ6°C; 0°C and 6°C above present-day temperatures in the Kiel Bight) were chosen. Both the timing...
Article
An integral concept of ecological research is the constraint of biodiversity along latitudinal and environmental gradients. The Red Sea features a natural example of a latitudinal gradient of salinity, temperature and nutrient richness. Coral reefs along the Red Sea coasts are supported with allochthonous resources such as oceanic and neritic phyto...
Article
Full-text available
Concern about climate change has re-ignited interest in universal ecological responses to temperature variations: (1) biogeographical shifts, (2) phenology changes, and (3) size shifts. In this study we used copepods as model organisms to study size responses to temperature because of their central role in the pelagic food web and because of the on...
Conference Paper
Full-text available
We investigated the impacts of ocean acidification and increasing temperatures on natural plankton communities of the Baltic Sea in two mesocosm experiments, performed with summer and autumn plankton communities respectively. In the first experiment in 2012, we found that higher temperatures more affect the plankton community by lowering food-avail...
Article
The widely cited Plankton Ecology Group (PEG) model of plankton seasonal succession is often used as a template to explain the seasonal changes in plankton communities outside the cold temperate zone, where it was developed, but this may be inappropriate for lower-latitude lakes.Lower-latitude lakes have high light availability in winter and less p...
Article
Full-text available
Simultaneous triple stable isotope analysis of carbon, nitrogen and sulphur was employed to study the temporal variation in the food web of a subtidal eelgrass (Zostera marina) bed in the western Baltic Sea. Samples of three potential food sources: eelgrass, epiphytes and seston, as well as consumer species were collected biweekly from March throug...
Conference Paper
Full-text available
Concerns about climate change have re-ignited interest in universal ecological responses to temperature variations: 1) biogeographical shifts, 2) phenology changes and 3) size shifts. Size reduction due to warming is discussed to via three different mechanisms: interspecific shifts, age structure within populations, and intraspecific changes. Copep...
Article
Ocean warming has been implicated in the observed decline of oceanic phytoplankton biomass. Some studies suggest a physical pathway of warming via stratification and nutrient flux, and others a biological effect on plankton metabolic rates; yet the relative strength and possible interaction of these mechanisms remains unknown. Here, we implement pr...
Article
Full-text available
Simultaneous analysis of carbon, nitrogen and sulphur stable isotope ratios was applied in this pilot study to examine the food web of a Zostera marina L. system in the western Baltic Sea. Samples of 3 potential food sources: eelgrass, epiphytic algae and seston, as well as 69 consumer species were collected during the growing season of Z. marina f...
Article
We compared the development and fatty acid content of the harpacticoid copepods Tachidius discipes and Tisbe sp. fed with different microalgal species (Dunaliella tertiolecta, Rhodomonas sp., Phaeodactylum tricornutum, Isochrysis galbana and a concentrate of Pavlova sp.), which differed in cell size and fatty acid composition. Tisbe could develop i...
Article
Recent climate warming is expected to affect phytoplankton biomass and diversity in marine ecosystems. Temperature can act directly on phytoplankton (e.g. rendering physiological processes) or indirectly due to changes in zooplankton grazing activity. We tested experimentally the impact of increased temperature on natural phytoplankton and zooplank...
Article
Full-text available
The Saudi Arabian Red Sea coast is characterized by a strong environmental gradient from north (28.5°N) to south (16.5°N) with challenging conditions for coral growth particularly in the south (high temperature and nutrient input). We investigated whether assemblies of reef-building corals and the distribution of functional groups follow a latitudi...
Article
Full-text available
The Saudi Arabian Red Sea coast is characterized by a strong environmental gradient from north (28.5°N) to south (16.5°N) with challenging conditions for coral growth particularly in the south (high temperature and nutrient input). We investigated whether assemblies of reef-building corals and the distribution of functional groups follow a latitudi...
Article
Full-text available
The objective of this study was to quantify chemical and biological responses to an experimentally increased nutrient input to an open coastal planktonic ecosystem and to contribute to a scientific concept and credible indicators for managing nutrient supply to coastal waters. Data were derived in a 5year fertilisation experiment of a tidal driven...
Article
Three species of marine phytoplankton, Rhodomonas sp., Isochrysis galbana Parke, and Phaeodactylum tricornutum Bohlin, were cultivated in semicontinuous cultures to test biochemical responses (fatty acids; FAs) to five nitrogen (N):phosphorus (P) supply ratios and four growth rates (dilution rates). The characteristic FA profile was observed for ea...
Article
In our recent contribution to the special issue on plankton dynamics in a fast‐changing world, we outlined some general predictions of plankton dynamics in different climate regions now and in future, building on the Plankton Ecology Group (PEG) model (de Senerpont Domis et al., 2013).We proposed a stylised version of plankton dynamics in Fig. 3 of...
Conference Paper
Full-text available
In the frame of the German BIOACID project, we investigate the impacts of acidification and temperature changes on the quantity and quality of the marine planktonic food web. We aim to understand the interaction between warming and acidification effects on primary producers (phytoplankton) and consumers (copepods) when embedded in natural plankton...
Data
Scientific name, ecological guild, number of collected specimens (n), δ13C and δ15N values (‰; mean ±SE and number of stable isotope analysis (n) of animals collected during the field expedition in September and October 2011 from Maqna (Gulf of Aqaba) to the Farasan archipelago (southern Red Sea) at the west coast of Saudi Arabia.
Article
Full-text available
Shrinking of body size has been proposed as one of the universal responses of organisms to global climate warming. Using phytoplankton as an experimental model system has supported the negative effect of warming on body-size, but it remains controversial whether the size reduction under increasing temperatures is a direct temperature effect or an i...
Article
Full-text available
Driving factors of phytoplankton spring blooms have been discussed since long, but rarely analyzed quantitatively. Here, we use a mechanistic size-based ecosystem model to reconstruct observations made during the Kiel mesocosm experiments (2005–2006). The model accurately hindcasts highly variable bloom developments including community shifts in ce...
Article
Full-text available
Changing seawater chemistry towards reduced pH as a result of increasing atmospheric carbon dioxide (CO2) is affecting oceanic organisms, particularly calcifying species. Responses of non-calcifying consumers are highly variable and mainly mediated through indirect ocean acidification effects induced by changing the biochemical content of their pre...
Article
Global warming is assumed to alter the trophic interactions and carbon flow patterns of aquatic food webs. The impact of temperature on phyto-bacterioplankton coupling and bacterial community composition (BCC) was the focus of the present study, in which an indoor mesocosm experiment with natural plankton communities from the western Baltic Sea was...
Article
The Eastern Tropical North Atlantic (ETNA) is characterised by a strong east to west gradient in the vertical upward flux of dissolved inorganic nitrogen to the photic zone. We measured the stable nitrogen isotope (δ15N) signatures of various zooplankton taxa covering twelve stations in the ETNA (04°–14°N, 016–030°W) in fall 2009, and observed sign...
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##
Data
Sequences were screened for chimeras by the submitter using Bellerophon and DECIPHER. ##Assembly-Data-START## Sequencing Technology :: Sanger dideoxy sequencing ##Assembly-Data-END##