Biology subjects

Blasius, B.

Publications and source records attributed to Blasius, B..

6 recordsLinked to original sources

bioRxiv2026

A growth-maintenance tradeoff determines nutrient-limited growth in phytoplankton

Phytoplankton encounter a range of light and nutrient conditions in nature and must adjust their internal carbon and nitrogen allocations to grow across different resource environments. Current phytoplankton carbon budget models treat respiration simply as a carbon loss. In reality, respiration is a critical cellular process that produces energy for nutrient uptake and cellular maintenance. Drawing on empirical evidence, we developed an eco-physiological model that incorporates a more realistic role of respiration. In our model, photosynthetic carbon is partitioned into: (i) the Pentose Phosphate Pathway (PPP) for assimilation and (ii) respiration for energy production that is then used in nutrient uptake. Stored nitrogen is partitioned between three pools: cellular structure, photosynthesis and nutrient uptake. Using an optimality-based approach, we identify strategies that maximize either exponential growth rate or competitive ability. We find that optimal internal allocations follow a growth-maintenance tradeoff, favoring population growth through carbon acquisition in nitrogen-replete conditions and population maintenance through nitrogen acquisition in nitrogen-limited conditions. The optimal allocations match empirically observed shifts in carbon partitioning at different dilution rates. Our model also generates an interactive growth response surface with an asymmetry, where light is the dominant limiting factor at low light intensities and co-limitation by light and nitrogen only occurs at high light levels. Furthermore, the model recovers the widely accepted Droop function for growth vs nitrogen quota and predicts a hyperbolic decline in growth vs energy quotas. Through a simple growth-maintenance tradeoff, our model provides a mechanistic foundation for predicting phytoplankton productivity in biogeochemical models.

ecology↗

bioRxiv2022

Inherited geomagnetic signposts can maintain migratory detours in changing geomagnetic landscapes

BackgroundFor many migratory species, inexperienced (naive) individuals reach remote nonbreeding areas independently using one or more inherited compass headings and, potentially, magnetic signposts to gauge where to switch between compass headings. Inherited magnetic-based migratory orientation programs have not yet been assessed as a population-level process, particularly where strong geomagnetic spatial gradients or long-term shifts could create mismatches with inherited magnetic headings. In particular, it remains unstudied whether and how, under natural selection, inherited headings and signposts could potentially adapt to long-term geomagnetic shifts. MethodsTo address these unknowns, we modelled bird migration using an evolutionary algorithm incorporating global geomagnetic data (1900-2023). Modelled population mixing incorporated both natal dispersal and trans-generational inheritance of magnetic headings and signposts, the latter including intrinsic (stochastic) variability. Using the model, we assessed robustness of signposted and non-signposted trans-hemispheric songbird migration across a rapidly magnetically-shifting Nearctic breeding region (mean 34{degrees} declination shift) via Europe to Africa. ResultsModel-evolved magnetic-signposted migration was (i) overall successful throughout the 124-year period, with 60-90% mean successful arrival across a broad range in plausible compass precision, (ii) through reduced trans-Atlantic flight distances, up to twice as successful compared with non-signposted migration, but (iii) to avoid evolving unsustainable open-ocean flights, intrinsic variability in inheritance of magnetic headings was required (model-evolved {sigma} {approx} 2.6{degrees} standard error in inherited headings). ConclusionsOur study supports the potential long-term viability of inherited magnetic migratory headings and signposts, and illustrates more generally how inherited migratory programs can both mediate and constrain evolution of routes, in response to global environmental change.

ecology↗

bioRxiv2022

Growth, organic matter release, aggregation and recycling during a diatom bloom: A model-based analysis of a mesocosm experiment

Mechanisms terminating phytoplankton blooms are often not well understood. Potentially involved processes such as consumption by grazers, flocculation, and viral lysis each have different post-bloom consequences on the processing of the organic material, therefore it is important to develop a better understanding of the relevance of these processes, and potential interactions between them. In this study, we present a model-based analysis of a spring bloom observed in a mesocosm experiment. The intermediate-complexity (27-state variable) numerical model we extended from an earlier version to this end can resolve C, N, P and Si cycles, and relevant processes like formation of various organic material size classes (low and high molecular weight (hereafter small and large) dissolved organic carbon (DOC), transparent exopolymer particles (TEP), and small/large detritus) and their degradation by two bacterial sub-communities (free-living and particle-attached) and planktonic protists (heterotrophic flagellates and ciliates). The model can explain > 90% of the variation of a rich set of observations consisting of 11 independent variables over the course of 13 days during which a bloom largely dominated by diatoms develops, and disappears almost entirely. Fluxes estimated by the model point to the importance of coagulation (TEP formation) as a sink term for DOC, and a source term for POC. Consequently, aggregation with TEPs constitute an important loss term for phytoplankton. The flocculated phytoplankton, and detrital material, in turn become rapidly degraded by the particle attached bacteria and other protist heterotrophs. Through a scenario analysis, the relevance of nutrient-stress enhanced lysis rates; alterations between small and large DOC in phytoplankton exudates; and coagulation of smaller DOC molecules were investigated. Our results suggest that the former two processes have negligible effects in isolation, but when combined with the latter, they can synergistically cause substantial deviations in TEP formation, hence, in flocculation rates; and consequently in the peak magnitude of the diatom bloom, and in timing of its termination. Our results point to a need for better understanding of processes governing the termination of phytoplankton blooms, their inter-dependencies, and consequences on the global biogeochemical cycles.

microbiology↗

bioRxiv2021

Emergent Diversity and Persistent Turnover in Evolving Microbial Cross-Feeding Networks

A distinguishing feature of many ecological networks in the microbial realm is the diversity of substrates that could potentially serve as energy sources for microbial consumers. The microorganisms are themselves the agents of compound diversification via metabolite excretion or overflow metabolism. It has been suggested that the emerging richness of different substrates is an important condition for the immense biological diversity in microbial ecosystems. In this work, we study how complex cross-feeding networks (CFN) of microbial species may develop from a simple initial community given some elemental evolutionary mechanisms of resource-dependent speciation and extinctions using a network flow model. We report results of several numerical experiments and report an in-depth analysis of the evolutionary dynamics. We find that even in stable environments, the system is subject to persisting turnover, indicating an ongoing co-evolution. Further, we compare the impact of different parameters, such as the ratio of mineralization, as well as the metabolic versatility and variability on the evolving community structure. The results imply that high microbial and molecular diversity is an emergent property of evolution in cross-feeding networks, which affects transformation and accumulation of substrates in natural systems, such as soils and oceans, with potential relevance to biotechnological applications.

systems biology↗

bioRxiv2021

Coexistence patterns and diversity in a trait-based metacommunity on an environmental gradient

The dynamics of trait-based metacommunities have attracted much attention, but not much is known about how dispersal and spatial environmental variability mutually interact with each other to drive coexistence patterns and diversity. Here, we present a spatially-explicit model of resource competition in a metacommunity on a one-dimensional environmental gradient. We find that both the strength of dispersal and the range of spatial environmental variability affect coexistence patterns, spatial structure, trait distribution and local and regional diversity. Without dispersal, species are sorted according to their optimal growth conditions on the gradient. With the onset of dispersal source-sink effects are initiated, which increases the effects of environmental filtering and interspecific competition and generates trait lumping, so that only a few species from an environment-defined trait range can survive. Interestingly, for very large dispersal rates the system becomes spatially homogeneous, but nevertheless two species at the extreme ends of the trait-off curve can coexist for large environmental variability. Local species richness follows a classic hump-shaped dependence on dispersal rate, while local and regional diversity exhibit a pronounced peak for intermediate values of the environmental variability. Our findings provide important insights into the factors that shape the structure of trait-based metacommunities.

ecology↗

bioRxiv2020

Shape matters: cell geometry determines phytoplankton diversity

Size and shape profoundly influence an organisms ecophysiological performance and evolutionary fitness, suggesting a link between morphology and diversity. However, not much is known about how body shape is related to taxonomic richness, especially in microbes. Here we analyse global datasets of unicellular marine phytoplankton, a major group of primary producers with an exceptional diversity of cell sizes and shapes and, additionally, heterotrophic protists. Using two measures of cell shape elongation, we quantify taxonomic diversity as a function of cell size and shape. We find that cells of intermediate volume have the greatest shape variation, from oblate to extremely elongated forms, while small and large cells are mostly compact (e.g., spherical or cubic). Taxonomic diversity is strongly related to cell elongation and cell volume, together explaining up to 92% of total variance. Taxonomic diversity decays exponentially with cell elongation and displays a log-normal dependence on cell volume, peaking for intermediate-volume cells with compact shapes. These previously unreported broad patterns in phytoplankton diversity reveal selective pressures and ecophysiological constraints on the geometry of phytoplankton cells which may improve our understanding of marine ecology and the evolutionary rules of life.

ecology↗