Biology subjects

Boss, E.

Publications and source records attributed to Boss, E..

7 recordsLinked to original sources

bioRxiv2024

Emergent patterns of patchiness reflect decoupling between ocean physics and biology

While a rich history of patchiness research has explored spatial structure in the ocean, there is still no consensus over the controls on biological patchiness and how biogeochemical processes and patchiness relate. The prevailing thought is that physics structures biology, but this has not been tested at the basin scale with consistent in situ measurements. Here we show that the patchiness of physics and biology are decoupled at the global scale through analysis of a global dataset of in situ surface optical properties from the S/V Tara and using the slope of spatial scale vs variance to quantify patchiness. Based on analysis of [~]650,000 nearly continuous (dx[~]150m) measurements from an underway sampling system - representing five years of consistently collected data across the Atlantic, Pacific, and Southern Oceans - we find the patchiness of physical and biological parameters are uncorrelated. We show that variance slope is an emergent property with unique patterns in biogeochemical properties that are distinct from physical tracers, yet connected to other biological tracers. These results provide context for decades of discrepancy between in situ studies, could support new tests of biogeochemical model parameterizations, and open the way for new insight into processes regulating the observed patterns.

ecology↗

bioRxiv2024

Ubiquity of inverted 'gelatinous' ecosystem pyramids in the global ocean

Summary paragraphPlankton are essential in marine ecosystems. However, our knowledge of overall community structure is sparse due to inconsistent sampling across their very large organismal size range. Here we use diverse imaging methods to establish complete plankton inventories of organisms spanning five orders of magnitude in size. Plankton community size and trophic structure variation validate a long-held theoretical link between organism size-spectra and ecosystem trophic structures. We found that predator/grazer biomass and biovolume unexpectedly exceed that of primary producers at most (55%) locations, likely due to our better quantification of gelatinous organisms. Bottom- heavy ecosystems (the norm on land) appear to be rare in the ocean. Collectively, gelatinous organisms represent 30% of the total biovolume (8-9% of carbon) of marine plankton communities from tropical to polar ecosystems. Communities can be split into three extreme typologies: diatom/copepod-dominated in eutrophic blooms, rhizarian/chaetognath-dominated in oligotrophic tropical oceans, and gelatinous-dominated elsewhere. While plankton taxonomic composition changes with latitude, functional and trophic structures mostly depend on the amount of prey available for each trophic level. Given future projections of oligotrophication of marine ecosystems, our findings suggest that rhizarian and gelatinous organisms will increasingly dominate the apex position of planktonic ecosystems, leading to significant changes in the oceans carbon cycle.

ecology↗

bioRxiv2023

Evidence for kilometer-scale biophysical features at the Gulf Stream front

Understanding the interplay of ocean physics and biology, particularly at the submesoscale and below (<30km), is an ongoing challenge in oceanography. While poorly constrained, these scales may be of critical importance for understanding how changing ocean dynamics will impact marine ecosystems. Fronts in the ocean, regions where two disparate water masses meet and isopycnals become tilted towards vertical, are considered hotspots for biophysical interaction, but there is limited observational evidence at the appropriate scales to assess their importance. Western boundary currents like the Gulf Stream are of particular interest as these dynamic physical regions are thought to influence both productivity and composition of primary producers; however, how exactly this plays out, and at what scales, is not well known. Using satellite data and two years of detailed in situ observations across the Gulf Stream front near Cape Hatteras, North Carolina, U.S.A., we investigate how submesoscale frontal dynamics could affect biological communities associated with frontal regions and generate hotspots of productivity and export. In this analysis we assess the seasonality and phenology of the region, generalize the kilometer-scale structure of the front, and analyze 69 transects to assess two physical processes of potential biogeochemical importance: cold shelf filament subduction and high salinity Sargasso Sea obduction. We link these processes observationally to the meander phase of the Gulf Stream and discuss how cold filament subduction could be exporting carbon and how obduction of high salinity water from depth often leads to high chlorophyll-a. Finally, we report on phytoplankton community composition in each of these features and integrate these new observations into our understanding of frontal submesoscale dynamics. Plain Language SummaryPhytoplankton move with large currents and are stirred by eddies with diameters ranging from 100s of kilometers down to the meter scale. Their growth is impacted by physical factors like light and temperature and also chemical and biological factors like nutrient availability, and their accumulation is also impacted by top down controls (zooplankton grazing, viral lysis) and competition with other phytoplankton. This interplay of physics and biology in determining the biomass and composition of phytoplankton communities is poorly understood and is key to understanding marine ecosystem resilience and structure in a changing ocean. In this work we investigated the impact of physics and biology on phytoplankton across scales focusing on the Gulf Stream front. Fronts in the ocean are where lines of equal density go from being horizontal to having a vertical tile, and because of this can enable nutrients and plankton to move from depth to the surface and vice versa. The objective of this work is to understand how physics might drive important changes in phytoplankton biomass and composition in the Gulf Stream front, which is amongst the sharpest gradients in temperature, density, and current speed in the global ocean. We find two frequent processes at the front, the apparent subduction of cold filaments down along the edge of the Gulf Stream, associated with meander troughs, and obduction of high salinity Sargasso Sea water into the front linked to meander crests. While ephemeral, these processes are frequent and could have a large impact on local phytoplankton biomass, phytoplankton composition, and the export of organic matter to depth. Key PointsO_LIThe frontal zone between the Gulf Stream and the shelf has an interface water mass which appears to have different origins with a range of biogeochemical impacts. C_LIO_LIMeanders appear to largely control the frontal interface: troughs lead to subduction of shelf filaments and crests lead to obduction of high salinity water. C_LIO_LIThese two processes are common at the front and could lead to ephemeral kilometer- scale export and productivity. C_LI

ecology↗

bioRxiv2022

Disparate patterns of genetic divergence in three widespread corals across a pan-Pacific environmental gradient highlights species-specific adaptation trajectories.

Tropical coral reefs are among the worst affected ecosystems by climate change with predictions ranging between a 70-90% loss of reefs in the coming decades. Effective conservation strategies that maximize ecosystem resilience, and potential for recovery, must be informed by the accurate characterization of extant genetic diversity and population structure together with an understanding of the adaptive potential of keystone species. Here, we analyzed samples from the Tara Pacific Expedition (2016 to 2018) that completed an 18,000 km longitudinal transect of the Pacific Ocean sampling three widespread corals - Pocillopora meandrina, Porites lobata, and Millepora cf. platyphylla - across 33 sites from 11 islands. Using deep metagenomic sequencing of 269 colonies in conjunction with morphological analyses and climate variability data we can show that the sampled transect encompasses multiple morphologically cryptic species that exhibit disparate biogeographic patterns, and most importantly, distinct evolutionary patterns, despite exposure to identical environmental regimes. Our findings demonstrate on a basin-scale that evolutionary trajectories are species-specific and complex, and can only in part be predicted from the environment. This highlights that conservation strategies must integrate multi-species investigations to consider the distinct genomic footprints shaped by selection as well as the genetic potential for adaptive change.

genetics↗

bioRxiv2022

Global observation of plankton communities from space

Satellite remote sensing from space is a powerful way to monitor the global dynamics of marine plankton. Previous research has focused on developing models to predict the size or taxonomic groups of phytoplankton. Here we present an approach to identify representative communities from a global plankton network that included both zooplankton and phytoplankton and using global satellite observations to predict their biogeography. Six representative plankton communities were identified from a global co-occurrence network inferred using a novel rDNA 18S V4 planetary-scale eukaryotic metabarcoding dataset. Machine learning techniques were then applied to train a model that predicted these representative communities from satellite data. The model showed an overall 67% accuracy in the prediction of the representative communities. The prediction based on 17 satellite-derived parameters showed better performance than based only on temperature and/or the concentration of chlorophyll a. The trained model allowed to predict the global spatiotemporal distribution of communities over 19-years. Our model exhibited strong seasonal changes in the community compositions in the subarctic-subtropical boundary regions, which were consistent with previous field observations. This network-oriented approach can easily be extended to more comprehensive models including prokaryotes as well as viruses.

ecology↗

bioRxiv2022

Characterizing phytoplankton communities in the absence of resource-based competition

AO_SCPLOWBSTRACTC_SCPLOWUnder most natural marine conditions, phytoplankton cells suspended in the water column are too distantly spaced for direct competition for resources to be a routine occurrence. Accordingly, resource-based competitive exclusion should be rare. In contrast, contemporary ecosystem models typically predict an exclusion of larger phytoplankton size classes under low-nutrient conditions, an outcome interpreted as reflecting the competitive advantage of small cells having much higher nutrient affinities than larger cells. Here, we develop mechanistically-focused expressions for steady-state, nutrient-limited phytoplankton growth that are consistent with the discrete, distantly-spaced cells of natural populations. These expressions are then encompassed in an ecosystem model that sustains diversity across all size classes over the full range in nutrient concentrations observed in the ocean. In other words, our model does not exhibit resource-based competitive exclusion between size classes. We show that the basis for species exclusions in earlier models is not a reflection of size-dependent nutrient affinities, but rather a consequence of inappropriate descriptions of non-grazing phytoplankton mortality.

ecology↗

bioRxiv2020

Plankton Planet: 'seatizen' oceanography to assess open ocean life at the planetary scale

In every liter of seawater there are between 10 and 100 billion life forms, mostly invisible, called plankton, which form the largest and most dynamic ecosystem on our planet, at the heart of global ecological and economic processes. While physical and chemical parameters of planktonic ecosystems are fairly well measured and modelled at the planetary scale, but biological data are still scarce due to the extreme cost and relative inflexibility of the classical vessels and instruments used to explore marine biodiversity. Here we introduce Plankton Planet, an initiative whose goal is to merge the creativity of researchers, makers, and mariners to (i) develop frugal scientific instrumentation and protocols to assess the genetic and morphological diversity of plankton life, and (ii) organize their systematic deployment through fleets of volunteer sailors, fishermen, or cargo-ships to generate comparable and open-access plankton data across global and long-term spatio-temporal scales. As proof-of-concept, we show how 20 crews of sailors ("planktonauts") were abl to sample plankton biomass from the world surface ocean in a single year, generating the first citizen-based, planetary dataset of plankton biodiversity based on DNA barcodes. The quality of this dataset is comparable to that generated by Tara Oceans and is not biased by the multiplication of samplers. This dataset has unveiled significant genetic novelty and can be used to explore the taxonomic and ecological diversity of plankton at both regional and global scales. This pilot project paves the way for construction of a miniaturized, modular, evolvable, affordable and open-source citizen field-platform that will allow systematic assessment of the eco/morpho/genetic variation of aquatic ecosystems across the dimensions of the Earth system.

ecology↗