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1. Seagrass Abundance Predicts Surficial Soil Organic Carbon Stocks Across the Range of Thalassia testudinum in the Western North Atlantic

   James W. Fourqurean1 · Justin E. Campbell1, 2 · (May 2023, Estuaries and coasts)

   The organic carbon (Corg) stored in seagrass meadows is globally significant and could be relevant in strategies to mitigate increasing CO2 concentration in the atmosphere. Most of that stored Corg is in the soils that underlie the seagrasses. We explored how seagrass and soil characteristics vary among seagrass meadows across the geographic range of turtlegrass (Thalassia testudinum) with a goal of illuminating the processes controlling soil organic carbon (Corg) storage spanning 23° of latitude. Seagrass abundance (percent cover, biomass, and canopy height) varied by over an order of magnitude across sites, and we found high variability in soil characteristics, with Corg ranging from 0.08 to 12.59% dry weight. Seagrass abundance was a good predictor of the Corg stocks in surficial soils, and the relative importance of seagrass-derived soil Corg increased as abundance increased. These relationships suggest that first-order estimates of surficial soil Corg stocks can be made by measuring seagrass abundance and applying a linear transfer function. The relative availability of the nutrients N and P to support plant growth was also correlated with soil Corg stocks. Stocks were lower at N-limited sites than at P-limited ones, but the importance of seagrass-derived organic matter to soil Corg stocks was not a function of nutrient limitation status. This finding seemed at odds with our observation that labile standard substrates decomposed more slowly at N-limited than at P-limited sites, since even though decomposition rates were 55% lower at N-limited sites, less Corg was accumulating in the soils. The dependence of Corg stocks and decomposition rates on nutrient availability suggests that eutrophication is likely to exert a strong influence on carbon storage in seagrass meadows. 

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2. Global seagrass carbon stock variability and emissions from seagrass loss

   https://doi.org/10.1038/s41467-025-59204-4  

   Krause, Johannes R; Cameron, Clint; Arias-Ortiz, Ariane; Cifuentes-Jara, Miguel; Crooks, Steve; Dahl, Martin; Friess, Daniel A; Kennedy, Hilary; Lim, Kiah Eng; Lovelock, Catherine E; et al (December 2025, Nature Communications)

   Seagrass ecosystems are recognized for their capacity to sequester and store organic carbon, but there is large variability in soil organic carbon stocks associated with plant traits and environmental conditions, making the quantification and scaling of carbon storage and fluxes needed to contribute to climate change mitigation highly challenging. Here, we provide estimates of carbon stocks associated with seagrass systems (biomass and soil) through analyses of a comprehensive global database including 2700+ seagrass soil cores. The median global soil Corg stock estimate is 24.2 (12.4 – 44.9) Mg Corg ha−1 in the top 30 cm of soil, 27% lower than estimates from previous global syntheses, refining the IPCC Tier 1 soil Corg stock currently used for carbon accounting in places without local data. We estimate that seagrass carbon stocks at risk of degradation could emit 1,154 Tg (665 – 1699) CO2 with a social cost of $213 billion (2020 US dollars), if no action is taken to conserve these habitats. 

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3. Climate oscillations drive nutrient availability and seagrass abundance at a regional scale

   https://doi.org/10.1002/lno.12787  

   Krause, Johannes R; Roden, Ana; Briceño, Henry; Fourqurean, James W (March 2025, Limnology and Oceanography)

   Abstract Seagrasses are increasingly recognized for their ecosystem functions and services. However, both natural and anthropogenic stressors impact seagrass functional traits, for example by altering nutrient regimes. Here, we synthesize 27 yr of data from regional, long‐term seagrass and water quality monitoring programs of south Florida to investigate the impacts of relative nutrient availability on seagrass abundance (as expressed by percent cover) across an oligotrophic seascape. We employ linear mixed‐effect models and generalized additive models to show that seagrass abundance is driven by interannual variations in nutrient concentrations, which are ultimately controlled by climate oscillations (El Niño Southern Oscillation Atlantic Multidecadal Oscillation) via regional rainfall‐runoff relationships. Our study suggests that climate oscillations drive interannual variations in seagrass cover on a regional scale, with high‐rainfall years leading to increased nitrogen availability and higher seagrass abundance in typically nitrogen‐limited backreef meadows. Conversely, these periods are associated with reduced seagrass cover at the more P‐limited inshore sites and in Florida Bay, with yet unknown consequences for the provision of seagrass ecosystem services. We show that nutrient delivery from runoff can have diverging impacts on benthic communities, depending on spatial patterns of relative nutrient limitation, with some N‐limited seagrass meadows showing resilience to periodic nutrient enrichment. 

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4. Seagrass Recovery Following Marine Heat Wave Influences Sediment Carbon Stocks

   https://doi.org/10.3389/fmars.2020.576784  

   Aoki, Lillian R.; McGlathery, Karen J.; Wiberg, Patricia L.; Oreska, Matthew P.; Berger, Amelie C.; Berg, Peter; Orth, Robert J. (January 2021, Frontiers in Marine Science)

   null (Ed.)

   Worldwide, seagrass meadows accumulate significant stocks of organic carbon (C), known as “blue” carbon, which can remain buried for decades to centuries. However, when seagrass meadows are disturbed, these C stocks may be remineralized, leading to significant CO 2 emissions. Increasing ocean temperatures, and increasing frequency and severity of heat waves, threaten seagrass meadows and their sediment blue C. To date, no study has directly measured the impact of seagrass declines from high temperatures on sediment C stocks. Here, we use a long-term record of sediment C stocks from a 7-km 2 , restored eelgrass ( Zostera marina ) meadow to show that seagrass dieback following a single marine heat wave (MHW) led to significant losses of sediment C. Patterns of sediment C loss and re-accumulation lagged patterns of seagrass recovery. Sediment C losses were concentrated within the central area of the meadow, where sites experienced extreme shoot density declines of 90% during the MHW and net losses of 20% of sediment C over the following 3 years. However, this effect was not uniform; outer meadow sites showed little evidence of shoot declines during the MHW and had net increases of 60% of sediment C over the following 3 years. Overall, sites with higher seagrass recovery maintained 1.7x as much C compared to sites with lower recovery. Our study demonstrates that while seagrass blue C is vulnerable to MHWs, localization of seagrass loss can prevent meadow-wide C losses. Long-term (decadal and beyond) stability of seagrass blue C depends on seagrass resilience to short-term disturbance events. 

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5. Soil properties and root characteristics across four lowland Panamanian forests from 0 - 1 m soil depths

   https://doi.org/10.15485/2447894  

   Cordeiro, Amanda L; Cusack, Daniela F; Dietterich, Lee H; Hockaday, William C; McFarlane, Karis J; Sivapalan, Vinothan; Hedgpeth, Alexandra; Neupane, Avishesh; Colburn, Lily; Konwent, Weronika; et al (January 2024, Environmental System Science Data Infrastructure for a Virtual Ecosystem; Consequences of Plant Nutrient Uptake for Soil Carbon Stabilization)

   Objectives:Fine roots significantly influence ecosystem-scale cycling of nutrients, carbon (C), and water, yet there is limited understanding of how fine root traits vary across and within tropical forests, some of Earth's most C-rich ecosystems. The biomass of fine roots can impact soil carbon storage, as root mortality is a primary source of new carbon to soils. A positive relationship has been observed between fine root biomass and soil carbon stocks in Panama (Cusack et al 2018). Beyond biomass, root characteristics like specific root length (SRL) could also influence soil carbon, as roots with higher SRL are less dense and thinner, potentially decomposing more easily or promoting soil aggregation. Understanding the effects of root morphology and tissue quality on soil carbon storage and with soil properties in general can improve predictions of landscape-scale carbon patterns. We aggregated new data of root biomass, morphology and nutrient content at 0-10 cm, 10-20 cm, 20-50 cm and 50-100 cm depth increments across four distinct lowland Panamanian forests and paired with already published datasets (Cusack et al 2018; Cusack and Turner 2020) of soil chemistry from the same sites and soil depths to explore relationship between soil carbon stocks and root characteristics.Datasets included:The datasets provided include .csv and .xlsx files for fine root characteristics and soil chemistry from four different forests across 0-10 cm, 10-20 cm, 20-50 cm, and 50-100 cm depth increments. Root characteristics include live fine root biomass, dead fine root biomass, coarse root biomass, specific root length, root diameter, root tissue density, specific root area, root %N, root %C, and root C/N ratio. Soil chemistry data includes total carbon (TC), dissolved organic carbon (DOC), bulk density, total phosphorus (TP), available phosphorus (AEM Pi), and various Mehlich-extractable elements such as aluminum, calcium, iron, potassium, manganese, phosphorus, and zinc. Nitrogen content measures include ammonium, nitrate, total dissolved nitrogen (TDN), dissolved inorganic nitrogen (DIN), and dissolved organic nitrogen (DON). The dataset also includes total exchangeable bases (TEB) and effective cation exchange capacity (ECEC) in both centimoles of charge per kilogram and micromoles of charge per gram. The soil chemistry data was obtained from Cusack et al (2018) and Cusack and Turner (2020) and paired with root characteristics data for the same depth increments and sites. Additionally, a .kml file is provided with coordinates for all 32 plots included in the study across four forests (n = 8 plots per site). Root data was averaged across these 8 plots per site and soil data was collected in one pit in each site. This dataset serves as baseline data before a throughfall exclusion experiment, Panama Rainforest Changes with Experimental Drying (PARCHED), was implemented. No special software is needed to open these files. 

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