Biology subjects

Weiss, J. F.

Publications and source records attributed to Weiss, J. F..

5 recordsLinked to original sources

bioRxiv2026

Microbial priming controls terrestrial carbon burial in marine sediments

Marine sediments are a globally important sink for organic carbon of both marine and terrestrial origin, yet far less terrestrial carbon is ultimately buried than rivers deliver to the ocean margins. This long-standing "terrestrial carbon conundrum" has resisted explanation, largely because conventional bulk proxies cannot distinguish marine, terrestrial and microbial-degrader carbon pools. Here we use sedimentary ancient DNA from five records spanning the Bering Sea to the Sea of Okhotsk over the past 30,000 years to reconstruct organic carbon resolved simultaneously by taxonomy and habitat. Integrating these taxon-resolved carbon estimates with environmental proxies across the last glacial-interglacial cycle, we find that terrestrial carbon burial is governed not only by supply but by biogeochemical interactions previously documented only in soils. Microbial processing splits into two competing pathways: under priming, marine organic matter fuels the degradation of terrestrial organic matter, whereas under preferential substrate utilization microbes consume marine organic matter and spare terrestrial carbon. Both pathways are triggered only once marine organic-matter availability crosses a critical, temperature-governed threshold. This temperature-sensitive cascade reveals a previously unrecognized vulnerability of the ocean's carbon sink to global warming.

biochemistry↗

bioRxiv2026

Taxon-resolved sources of organic carbon preserved in lake sediments using the sedaDNA GenC pipeline

Organic carbon (OC) burial in lakes is an important component of the global carbon cycle, but the source organisms of preserved OC remain poorly resolved. Here we develop the genC pipeline, which combines sedimentary ancient DNA concentrations, read-based taxonomic assignments, and group-specific priors for DNA and cellular carbon content to derive OCDNA-projected, a semi-quantitative proxy for the magnitude and taxonomic composition of preserved sedimentary OC. We apply genC to six high-latitude lake records spanning the last 30,000 years. OCDNA-projected broadly agrees with independent proxies for total organic carbon and aquatic contribution, supporting its reliability. Our results indicate that environmental conditions, especially warming, rather than preservation alone, are the main drivers of preserved OC variation. Terrestrial sources, mainly woody plants, dominate lake sediment OC. Eukaryotic algae as well as aquatic and terrestrial bacteria become more important during the warmer Holocene. These results establish sedaDNA as a taxonomically resolved tool for reconstructing long-term changes in preserved lake-sediment OC.

paleontology↗

bioRxiv2025

DNA virus-host patterns in lake and marine environments over the last glacial cycle

Viruses are crucial to population control, biogeochemical cycling, and host evolution, making them essential for ecosystem function. Here, we explore long-term virus-host interactions in lake and marine environments across the late Pleistocene and Holocene. We analysed sedimentary ancient DNA (sedaDNA) from five Siberian lakes and four Subarctic/Antarctic marine cores to infer past DNA virus taxa from metagenomic sequences. Viruses accounted for 0.089% (357 161 reads) of mapped reads across 2084 taxa. Virus communities differ between lakes and marine sites, with lakes dominated by Caudoviricetes and marine environments featuring Caudoviricetes and Algavirales. Each time series shows compositional changes in virus communities from the Pleistocene to the Holocene, supporting the inference that sedaDNA can reconstruct time-resolved ancient viral assemblages. Among the most abundant viruses, we identified 83 virus-host pairs known from published literature to infect bacterial, archaeal, or eukaryotic hosts, and assessed their associations using co-variation patterns. Over millennia, virus-host co-variations are particularly stable in marine systems, especially for phytoplankton-infecting viruses. However, in the Bering Sea, we find a lack of virus-host correlation, likely because an Arctic Pelagibacter strain expanded rapidly after the Bering Strait opened, potentially due to absent viral infection. Antagonistic patterns also appear between bacteriophages and hosts, possibly linked to shifts between lytic and lysogenic cycles in response to environmental changes. This study shows that sedaDNA can reveal ancient viral community structures and long-term ecological patterns, highlighting the value of ancient viromes in understanding ecosystem- specific responses to environmental change.

ecology↗

bioRxiv2024

Phaeocystis blooms caused carbon drawdown during the Antarctic Cold Reversal from sedimentary ancient DNA

The Southern Ocean plays a crucial role in the global carbon budget. Modeling studies propose that the atmospheric CO2 plateau during the Antarctic Cold Reversal (ACR; 14,700 to 12,700 calibrated years before present (cal yr BP)) is related to increased marine productivity. However, proxy evidence relating environmental conditions as well as primary community composition and productivity to carbon drawdown is missing. Our ancient DNA shotgun metagenomic analysis of marine sediments revealed Phaeocystis antarctica (haptophyte) as a key element of the primary producer community. Independent proxy evidence (blooming-related bacteria, Ba/Fe ratio) from the same sediment record point to high productivity in response to enhanced sea-ice seasonality caused by ACR cooling. Post ACR, abrupt Phaeocystis community loss shows how sensitive this ecosystem is to warming, potentially representing a key tipping element that may be further enhanced by the Phaeocystis-related sulfur cycle-climate feedback. As an analogy for present warming, it highlights the importance of regions with high seasonal sea-ice variability and Phaeocystis-dominance, such as the Ross Sea, for stabilizing atmospheric CO2 content. Additionally, our shotgun metagenomic data portray complex Holocene ecosystem establishment including key Antarctic taxa such as penguins, whales, and Antarctic fishes with implications for ongoing conservation efforts.

ecology↗

bioRxiv2024

Dynamic land-plant carbon sources in marine sediments inferred from ancient DNA

Terrigenous organic matter in marine sediments is considered a significant long-term carbon sink, yet our knowledge regarding its source taxa is severely limited. Here, we leverage land-plant ancient DNA from six globally distributed marine sediment cores covering the Last Glacial-Holocene transition as a proxy for the share, accumulation rate, preservation, and composition of terrigenous organic matter. We show that the spatial and temporal plant composition as revealed by sedaDNA records reflects mainly the vegetation dynamics of nearby continents as revealed by comparison with pollen from land archives. However, we also find indications of a global north-to-south translocation of sedaDNA. The plant composition shows that upland vegetation is strongly underrepresented in the record compared to riverine and coastal sources. We also find that plant sedaDNA has a higher accumulation rate in samples from the Late Glacial, which is characterized by high runoff and mineral load. Thus plant DNA in marine sediments allows for new perspectives on the global linkages between the terrestrial and marine carbon cycle which would benefit from a more quantitative understanding of DNA preservation and dispersal. This represents the basis of how climate change and land-use change translate into carbon-sink dynamics and also informs about natural carbon-capture solutions.

ecology↗