Biology subjects

Listmann, L.

Publications and source records attributed to Listmann, L..

9 recordsLinked to original sources

bioRxiv2026

Exploring Warming Effects on lower food-web dynamics in the plankton of the River Elbe Estuarine Ecosystem in summer: Insights from a Mesocosm Experiment

Understanding how warming alters estuarine plankton communities is essential for predicting future changes in biodiversity and ecosystem functioning. We conducted a four-week indoor mesocosm experiment using natural summer plankton from the Elbe River to examine the effects of warming (+2 {degrees}C and +4 {degrees}C) on abiotic conditions and responses of the plankton community. In this study, oxygen concentrations, primary producer biomass (chlorophyll a, microphytoplankton) and microzooplankton abundances declined sharply during the first 10 days across all treatments while mesozooplankton abundances increased. This suggests a strong top-down control by mesozooplankton on lower trophic levels across all temperature treatments. Primary producers biomass and oxygen concentrations recovered after an initial decline, however to lower levels compared to the onset of the experiment while micro- and mesozooplankton remained low during the second half of the experiment. Nutrient dynamics indicated progressive remineralization, with increasing ammonium, NOx, and silicate concentrations, while phosphate concentrations remained low throughout the experiment. Complementary DNA and RNA metabarcoding revealed similar community turnover over time in all treatments and temperature effects became only pronounced at the end of the experiment. Overall, warming effects were subtle relative to the strong internal trophic dynamics likely caused by the artificial mesocosm setup. Our findings of changes in plankton community dynamics indicate that biotic interactions, changes in trophic diversity and other environmental factors, i.e. oxygen concentrations are likely the drivers of this estuarine system rather than warming alone.

ecology↗

bioRxiv2026

Use of organic compounds by phytoplankton - a synthesis across strains from different habitats and functional groups

Mixotrophy is emerging as a default nutritional strategy in phytoplankton, but research seems so far isolated and mostly focusing on single phytoplankton groups or strains. Here we combined data from 24 oceanic and 22 freshwater strains to analyze phytoplanktons ability to use dissolved organic compounds. The results emphasize that mixotrophy is ubiquitous in phytoplankton across functional groups and taxa isolated from various habitats and not strictly dependent on light or nutrient deficiencies. We propose that the prevalence of mixotrophy stems from phytoplanktons heterotrophic ancestry, while the divergence into different lineages partly explains variation in mixotrophic behavior. Differences found in phytoplankton originating from different habitats may result from adaptive responses to habitat conditions, but conclusions need to be drawn carefully in line with the limited number of taxa included per habitat and potential niche partitioning. This study underscores the ecological significance of heterogeneous nutritional strategies and the necessity to address existing knowledge gaps to finally draw conclusions about the impact of mixotrophy in the context of single ecosystems and on global scales. Graphical abstract textAnalyzing thousands of data points across 46 marine and freshwater strains, this study establishes mixotrophy as a ubiquitous metabolic strategy in phytoplankton. These findings challenge the autotrophic paradigm, demonstrating that organic matter acquisition is a default state with significant implications for our understanding of global carbon cycles. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=93 SRC="FIGDIR/small/703725v2_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@cd9939org.highwire.dtl.DTLVardef@6a4fdorg.highwire.dtl.DTLVardef@39f5a6org.highwire.dtl.DTLVardef@12e811a_HPS_FORMAT_FIGEXP M_FIG C_FIG

microbiology↗

bioRxiv2026

Thermal responses of Baltic Sea Ostreococcus vary in their levels of intra-and interspecific variability

Trait variation within and between phytoplankton species as well as within regions, can shape community dynamics and ecosystem processes. A better understanding of this variability will improve the prediction of future ocean scenarios and the possible resilience of different phytoplankton groups. We investigated thermal response variation within and among three Ostreococcus species--a prominent picophytoplankton genus--using 31 strains from the Baltic Sea area and eastern North Sea. Across a temperature gradient ranging from 18{degrees}C up to 32{degrees}C, we quantified growth, cell size, and a proxy for chlorophyll a (Chla) and characterized their thermal responses using modeling approaches. We further assessed how these traits vary with temperature and quantified interspecific, intraspecific and intraregional variability. Thermal performance traits showed high variability within species and regions and moderate variability between species. Ostreococcus tauri showed significantly higher thermal optimum and a trend for higher peak rates than Ostreococcus mediterraneus. Thermal safety margin and the sensitivity of growth to temperature varied substantially within all species. For size and Chla, the species showed distinct temperature responses: Ostreococcus mediterraneus exhibited highest intraspecific variability and delayed responses at colder temperatures, Ostreococcus tauri responded linearly, with the Ostreococcus mediterraneus variant showing intermediate patterns. High intraspecific variation in Ostreococcus indicates substantial evolutionary potential, while interspecific differences may contribute to ecosystem stability under changing temperatures. This is especially relevant with predicted temperature-induced community shifts favoring smaller phytoplankton groups, highlighting the need to incorporate trait variability in ecosystem models.

ecology↗

bioRxiv2023

Co-evolutionary patterns shown in Ostreococcus-virus system from the Western Baltic Sea in freshly isolated hosts and viruses.

Marine viruses are a major driver of phytoplankton mortality and thereby influence biogeochemical cycling of carbon and other nutrients. In recent years, an understanding of the potential importance of phytoplankton-targeting viruses on ecosystem dynamics has emerged, but experimental investigations of host-virus interactions on a broad spatial and temporal scale are still missing. Here, we investigated in detail a phytoplankton hosts responses reacting to infections by species-specific viruses from i) distinct geographical regions and ii) different sampling seasons. Specifically, we used two species of picophytoplankton (1 {micro}m) Ostreococcus tauri and O. mediterraneus and their viruses (size ca. 100 nm), which represent systems well-known in marine biology, but almost entirely ignored in evolutionary biology. The strains stem from different regions of the Southwestern Baltic Sea that vary in salinity and temperature. Using an experimental cross-infection set-up, we show that in this natural system evolutionary history, and thus the timing of when hosts and their associated viruses coexisted, was the main driver of infection patterns. In addition species and strain specificity underline the present understanding of rapid host-virus co-evolution.

microbiology↗

bioRxiv2022

Predicting the unpredictable: heatwaves and history of variability shape phytoplankton community thermal responses within one generation

Predicting the effect of increased thermal unpredictability, for example in the shape of heatwaves on phytoplankton metabolic responses is ripe with challenges. While single genotypes in laboratory environments will respond to environmental fluctuations in predictable and repeatable ways, it is difficult to relate rapid evolutionary responses of whole communities to their ecological history. Previously experienced environments, including fluctuations therein, can shape an organisms specific niche as well as their responses to further environmental changes. This is a testable hypothesis as long as samples can be obtained where the environmental history is known, sufficiently diverse, and not obscured by confounding parameters such as day length and precipitation patterns. Here, we tested immediate (i.e. within one generation) metabolic temperature responses of natural phytoplankton assemblages from two thermally distinct regions in the Baltic Sea: the warmer and less predictable Kiel Area, and the overall colder and more predictable Bornholm Basin. Our approach allows us to investigate effects on immediate physiological time scales (responses curves), ecological and evolutionary processes on longer time scales (seasonal differences between basins) as well as mid-term responses during a natural occurring heatwave. We found evidence for a higher degree of phenotypic plasticity in samples from unpredictable environments (Kiel Area).

ecology↗

bioRxiv2021

Epidemiological dynamics of viral infection in a marine pico-eukaryote

Ostreococcus tauri is a ubiquitous marine pico-eukaryote that is susceptible to lysis upon infection by its species specific Ostreococcus tauri viruses (OtVs). In natural populations of O. tauri, costs of resistance are usually invoked to explain the persistence or reappearance of susceptible individuals in resistant populations. Given the low costs of resistance measured in laboratory experiments with the O. tauri/OtV system to date, the question remains of why susceptible individuals persist in the wild at all. Epidemiological models of host and pathogen population dynamics are one useful approach to understand the conditions that can allow the coexistence of susceptible and resistant hosts. We used a SIR (Susceptible-Infected-Resistant) model to investigate epidemiological dynamics under different laboratory culturing regimes that are commonly used in the O.tauri/OtV system. When taking into account serial transfer (i.e. batchcycle lengths) and dilution rates as well as different resistance costs, our model predicts that no susceptible cells should be detected under any of the simulated conditions - this is consistent with laboratory findings. We thus considered an alternative model that is not used in laboratory experiments, but which incorporates one key process in natural populations: host populations are periodically re-seeded with new infective viruses. In this model, susceptible individuals re-occurred in the population, despite low costs of resistance. This suggests that periodic attack by new viruses, rather than (or in addition to) costs of resistance, may explain the high proportion of susceptible hosts in natural populations, and underlie the discrepancy between laboratory studies and observations of fresh isolates. ImportanceIn natural samples of Ostreococcus sp. and its associated viruses, susceptible hosts are common. However, in laboratory experiments, fully resistant host populations readily and irreversibly evolve. Laboratory experiments are powerful methods for studying process because they offer a stripped-down simplification of a complex system, but this simplification may be an oversimplification for some questions. For example, laboratory and field systems of marine microbes and their viruses differ in population sizes and dynamics, mixing or migration rates, and species diversity, all of which can dramatically alter process outcomes. We demonstrate the utility of using epidemiological models to explore experimental design and to understand mechanisms underlying host-virus population dynamics. We highlight that such models can be used to form strong, testable hypotheses about which key elements of natural systems need to be included in laboratory systems to make them simplified, rather than oversimplified, versions of the processes we use them to study.

microbiology↗

bioRxiv2020

Carbon acquisition in a Baltic pico-phytoplankton species - Where does the carbon for growth come from?

- Pico-phytoplankton have ample scope to react to environmental change. But we know little about the underlying physiological mechanisms that govern how evolutionary history may affect short-term responses to environmental change. - We investigated growth rates and carbon uptake related traits (i.e. fitness proxies) in different temperatures and at different times during the microbial growth curve of eight novel strains of Ostreococcus sp. (ca. 1-2{micro}m). The strains were isolated from two distinct regions of the Baltic Sea differing in salinity and temperature from North-East (Bornholm Basin) to South-West (Kiel area). - Strains from the warmer, more variable Kiel area had higher growth rates in general and showed more variable growth rates compared to strains from the colder and less variable Bornholm Basin. - In addition, growth was maintained in early stages of the growth curve by organic carbon acquisition and the increase in growth over time and with temperature was associated with an increase in inorganic carbon acquisition (net primary productivity). - Based on the differences between net primary productivity and potential growth on organic carbon, we postulate a shift in carbon acquisition between inorganic and organic sources in Ostreococcus sp. with potential implications on ecological dynamics within microbial communities.

plant biology↗

bioRxiv2020

Functional redundancy in natural pico-phytoplankton communities depends on temperature and biogeography

Biodiversity affects ecosystem function, but how this relationship will pan out in a changing world is still a major question in ecology. It remains especially understudied for pico-phytoplankton communities, which contribute to carbon cycles and aquatic food webs year-round. Observational studies show a link between phytoplankton community diversity and ecosystem stability, but there is only scarce causal or empirical evidence. Here, we sampled phytoplankton communities from two biogeographically distinct (but close enough to not be confounded by differences in day length and precipitation) regions in the Southern Baltic Sea, and carried out a series of dilution/regrowth experiments across three assay temperatures. This allowed us to investigate the effects of loss of rare taxa and establish causal links in natural communities between species richness and several ecologically relevant traits (e.g. size, biomass production, and oxygen production), depending on sampling location and assay temperature. We found that the samples bio-geographical origin determined whether and how functional redundancy changed as a function of temperature for all traits under investigation. Samples obtained from the slightly warmer and more thermally variable regions showed overall high functional redundancy. Samples from the slightly cooler, less variable, stations showed little functional redundancy, i.e. function decreased the more species were lost from the community. The differences between regions were more pronounced at elevated assay temperatures. Our results imply that the importance of rare species and the amount of species required to maintain ecosystem function even under short-term warming (e.g. during heat waves) may differ drastically even within geographically closely related regions of the same ecosystem.

ecology↗

bioRxiv2020

Eco-evolutionary interaction in competing phytoplankton: genotype sorting likely explains dominance shift and species responses to CO2

How ecological and evolutionary processes interact and together determine species and community responses to climate change is poorly understood. We studied long-term dynamics (over approximately 200 asexual generations) in two phytoplankton species, a coccolithophore (Emiliania huxleyi) and a diatom (Chaetoceros affinis), to increased CO2 growing alone or competing with one another in co-occurrence. To allow for rapid evolutionary responses, the experiment started with a standing genetic variation of nine genotypes in each of the species. Under co-occurrence of both species, we observed a dominance shift from C. affinis to E. huxleyi after about 120 generations in both CO2 treatments, but more pronounced under high CO2. Associated with this shift, we only found weak adaptation to high CO2 in the diatom and none in the coccolithophore in terms of species growth rates. In addition, no adaptation to interspecific competition could be observed by comparing the single to the two-species treatments in reciprocal assays, regardless of the CO2 treatment. Nevertheless, highly reproducible genotype sorting left only one genotype remaining for each of the species among all treatments. This strong evolutionary selection coincided with the dominance shift from C. affinis to E. huxleyi. Since all other conditions were kept constant over time, the most parsimonious explanation for the dominance shift is that the strong evolutionary selection potentially altered competitive ability of the two species. Thus, here observed changes in the simplest possible two-species phytoplankton "community" demonstrated that eco-evolutionary interactions can be critical for predicting community responses to climate change in rapidly dividing organisms such as phytoplankton.

evolutionary biology↗