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Open research questions in Marine and coastal ecosystems

83 unresolved questions extracted from the limitations and future-work sections of 676 Marine and coastal ecosystems papers in our library. Each links back to the study that raised it.

What the literature leaves open

  • However, how the composition of riverine POC has evolved in response to declining sediment supply, and how such shifts influence OC burial in subaqueous deltaic systems remain unclear.

    Shifts in riverine POC sources reduce terrestrial OC burial in the Changjiang subaqueous delta · 2026 · DOI

  • While the present work addresses key limitations of previous designs through targeted improvements in optical configuration and signal processing (including a laser reference channel, internal temperature monitoring, and ambient light rejection), variability in the relationship between sensor signal and PIC concentration across depths and regions remains an open challenge. Furthermore, sensor performance under elevated pressure, variable temperature regimes, complex natural particle assemblages, and long-term autonomous deployment conditions remains to be established.

    A cross-polarized light scattering sensor for measuring the concentration of particulate inorganic carbon in seawater: laboratory validation · 2026 · DOI

  • One area that remains poorly understood is how urbanization impacts the bioavailability of dissolved organic carbon (BDOC), a measure of how readily heterotrophic microorganisms utilize organic carbon.

    Controls on Dissolved Organic Carbon Bioavailability Across an Urban Stream Network: Disturbance, Metabolism, and Seasonality · 2026

  • Though a highly stratified water column and stormy weather conditions at the time of our cruise seem to have limited the amount of Fe that reached the surface waters, also limiting subsequent phytoplankton growth, our findings point to a need for additional research on the connection between hydrothermal fluid release at mid-ocean ridges and primary productivity.

    Ironing Out Primary Productivity: The Effect of Hydrothermal Iron on Phytoplankton Photophysiology in the Southern Ocean · 2026 · DOI

  • Future research should focus on developing integrated characterization techniques to provide reliable and comparable multidimensional structural information for DBC, investigating structure-dependent heteroaggregation mechanisms in complex environmental matrices, and developing robust predictive models for its colloidal behavior.

    Colloidal stability of dissolved black carbon: interfacial mechanisms and environmental implications · 2026 · DOI

  • The establishment of the EaST station represents a structured step toward building a sustained, multidisciplinary observing system in the ES. The EaST program establishes a time-series framework designed to capture short-term variability and long- term changes in physical and biogeochemical properties, including deep oxygen content, ocean acidification, and greenhouse-gas dynamics in the ES. Through its integrative design, the EaST station provides an observational basis for examining the coupling between physical processes and biogeochemical feedbacks. The sustained time-series enables continuous monitoring of potential regime shifts—such as changes in deep convection, nutrient stoichiometry, and acidification—that may not be fully resolved by short-term surveys alone. These data are expected to support model evaluation of regional carbon budgets, greenhouse-gas fluxes, and ecosystem response projections under future climate scenarios. At the national level, the EaST station contributes to strengthening Korea’s ocean observation infrastructure by providing standardized, open-access datasets through the KODC. The program complements existing NIFS line-transect surveys and coastal monitoring networks, creat- ing an observational continuum from the coastal shelf to the open basin. This integration enhances Korea’s capacity to assess climate impacts on marine resources, water-mass properties, and biogeo- chemical cycles, ultimately informing marine policy and manage- ment. Internationally, the EaST station is designed to function as an interoperable node within the GOOS, OceanSITES, and Biogeoscapes frameworks. By harmonizing data and metadata standards with these global programs, EaST facilitates the inclusion of marginal-sea observations into global ocean databases. This contribution addresses the underrepresentation of marginal seas in global datasets. Collectively, these elements position the EaST program as a nationally coordinated and internationally interoper- able component of sustained ocean observation efforts.

    Establishment of the East Sea (Japan Sea) Time-series station: an integrated physical–biogeochemical observatory for a climate-sensitive marginal sea · 2026 · DOI

  • The artificial sharp increase in Ωsat across the outbound transect near the Society Islands was attributed to anomalies in normalized fluorescence line height (nFLH) or photosynthetically available radiation (iPAR) estimation from satellite products; improved validation and calibration of these satellite algorithms for coastal island environments is needed to accurately resolve iron stress responses.

    Dynamics of island mass effect – Part 2: Phytoplankton physiological responses · 2026 · DOI

  • Two stations near Rapa Nui and Samoa showed low total iron concentrations despite coastal proximity and upwelling signatures, contradicting the expected positive relationship between coastal upwelling and iron availability; the mechanisms driving low iron availability in these specific coastal zones need investigation to understand terrigeous versus upwelling iron sources.

    Dynamics of island mass effect – Part 2: Phytoplankton physiological responses · 2026 · DOI

  • The comparison of in situ bio-optical properties (chlorophyll a, backscattering coefficient, iron stress index) between inbound and outbound transects is confounded by different water masses being sampled, particularly for the Society Islands where 38 days separated the two transects; concurrent temporal sampling or Lagrangian tracking of the same water masses is needed to isolate island mass effect processes.

    Dynamics of island mass effect – Part 2: Phytoplankton physiological responses · 2026 · DOI

  • The variability in η' decline across the three island mass effect (IME) zones (sharp decline in Samoa versus marginal decreases in Rapa Nui and Society Islands) despite detected upwelling signatures requires investigation of island-specific hydrodynamic and biogeochemical mechanisms controlling nutrient availability and phytoplankton physiological response patterns.

    Dynamics of island mass effect – Part 2: Phytoplankton physiological responses · 2026 · DOI

  • The 8 km spatial resolution of the mixed layer depth (MLD) product used for computing the macronutrient stress index (η') is too coarse to accurately estimate the isothermal mixed layer (IML) depth in coastal zones near islands, leading to artificially sharp decreases in η' that may not reflect true phytoplankton physiological responses to nutrient stress.

    Dynamics of island mass effect – Part 2: Phytoplankton physiological responses · 2026 · DOI

  • The Spearman's rank correlation analysis examined relationships between environmental variability and N removal rates, but collinearity among fjord environmental factors (oxygen concentration, organic carbon, salinity) may mask direct mechanistic drivers—multivariate approaches or structural equation modeling of N burial versus denitrification in different redox conditions are not addressed.

    Long-term nitrogen burial exceeds denitrification in global fjords · 2026 · DOI

  • The spatial bootstrap analysis was performed to weight fjord observations, but the paper does not specify how fjord-specific environmental factors (glacier discharge, freshwater inputs, anthropogenic nitrogen loading) were incorporated into the weighting scheme or validated against independent fjord datasets.

    Long-term nitrogen burial exceeds denitrification in global fjords · 2026 · DOI

  • The study compared NAR and N2 production rates across oxic and deoxygenated fjords using permutation tests, but does not address how anammox (anaerobic ammonium oxidation) rates were quantified or partitioned from total N2 production in hypoxic sediments, which is critical for accurately assessing nitrogen removal pathways.

    Long-term nitrogen burial exceeds denitrification in global fjords · 2026 · DOI

  • The study compiled a global dataset of sediment burial and microbial N2 production rates from fjords, but does not specify whether temporal dynamics of nitrogen removal were captured at seasonal or interannual scales, limiting understanding of how climate-driven oxygen fluctuations affect long-term nitrogen burial versus denitrification partitioning.

    Long-term nitrogen burial exceeds denitrification in global fjords · 2026 · DOI

  • The Bayesian segmented regression model with three linear segments was used to examine potential change points in N2 production across redox regimes, but the paper does not specify validation of this three-segment model structure against alternative segmentation approaches or justification for why three segments best represent the O2 concentration-N2 production relationship in different fjord types.

    Long-term nitrogen burial exceeds denitrification in global fjords · 2026 · DOI

  • Heterotrophic bacterial emissions are still largely ignored when modeling marine BVOC cycling, indicating a need to incorporate both abundant compounds and bacterial trait variation into marine microbial models, BVOC budgets, and flux estimates.

    Volatile emissions from diverse estuarine bacteria share core compounds with a subset of strain-specific, low abundance compounds · 2026 · DOI

  • It is unknown whether the high BVOC emission found in BAL129 is a general feature in Sphingomonas, or specific to our strain. A future volatilomic analysis of this genus would be warranted.

    Volatile emissions from diverse estuarine bacteria share core compounds with a subset of strain-specific, low abundance compounds · 2026 · DOI

  • While the biodegradability of permafrost‐derived dissolved organic carbon (DOC) has been extensively studied in inland soils and freshwaters, few studies have examined dissolved OM (DOM) leached from eroding coastal permafrost in seawater.

    Eroding Permafrost Coastlines Release Biodegradable Dissolved Organic Carbon to the Arctic Ocean · 2024 · DOI

  • Most of the world’s lakes are located >45° N, where accelerated climate warming and elevated carbon loads might severely increase the risk of hypoxia, but this has not been systematically examined.

    Climate-driven deoxygenation of northern lakes · 2024 · DOI

  • In addition, although the runoff and sediment discharge of the Yellow River also decreased during 2003–2016, they were not related to the spatiotemporal variation of SSSCs and their direct impact was limited to the range of 15 km from the estuary.

    Decadal Variation and Regulation Mechanisms of the Suspended Sediment Concentration in the Bohai Sea, China · 2022 · DOI

  • Streams like this one are common in landscapes with low topographic relief, making it likely that the high contribution of instream metabolism to GHG fluxes that we observed is a widespread yet understudied behavior of many small streams.

    Patterns and Drivers of Dissolved Gas Concentrations and Fluxes Along a Low Gradient Stream · 2022 · DOI

  • Moreover, most arctic lake DOM compositions have been examined during the ice‐free summer, whereas DOM cycling between the ice‐covered winter months and summer have not been addressed.

    Trapped Under Ice: Spatial and Seasonal Dynamics of Dissolved Organic Matter Composition in Tundra Lakes · 2022 · DOI

  • Abstract Arctic lakes store, modify, and transport large quantities of carbon from terrestrial environments to the atmosphere; however, the spatial and temporal relationships between quantity and composition of dissolved organic matter (DOM) have not been well characterized across broad arctic regions.

    Trapped Under Ice: Spatial and Seasonal Dynamics of Dissolved Organic Matter Composition in Tundra Lakes · 2022 · DOI

  • Aerobic oxidation is a major sink of CH 4 in freshwater environments and thus an important determinant of aquatic CH 4 emissions, yet strikingly little is known about its drivers.

    The Extent and Regulation of Summer Methane Oxidation in Northern Lakes · 2018 · DOI

Most-cited papers in Marine and coastal ecosystems

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83 open questions have been extracted from the limitations and future-work passages of 676 Marine and coastal ecosystems papers in our library. Each one below links back to the study that raised it, so you can read the original claim in context.

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