Soil Carbon and Nitrogen Storage in Natural and Prop-Scarred Thalassia Testudinum Seagrass Meadows
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Soil Carbon and Nitrogen Storage in Natural and Prop-Scarred Thalassia Testudinum Seagrass Meadows Rachel N. Arney 1
&
Alison K. Shepherd 2 & Heather D. Alexander 3 & Abdullah F. Rahman 4
Received: 22 February 2019 / Revised: 8 May 2020 / Accepted: 20 May 2020 # Coastal and Estuarine Research Federation 2020
Abstract Seagrass meadows are carbon (C) sinks and nitrogen (N)-limited ecosystems that experience degradation from climate change and anthropogenic stressors, including prop-scarring disturbances by boating vessels. To better understand the variability in C and N pools of undisturbed seagrass soils and the recovery of these pools following boat propeller scarring, we quantified organic carbon (Corg) and N pools within the top 1 m of soils in undisturbed Thalassia testudinum seagrass beds of the Lower Laguna Madre (LLM), Texas, USA—a sub-tropical, uniquely hypersaline, and heavily used recreational boating lagoon—and used a chronosequence approach to compare these undisturbed soil pools to those in different aged prop scars (1–3, 4–6, 7–9, and 10+ years). We found that undisturbed soils stored 108.41 ± 2.93 and 6.65 ± 0.26 Mg (megagram) ha−1 of Corg and N, respectively, in the top 1 m, with ~ 30% of these pools stored within the top 20 cm. Scarring impacted these shallow, organic-rich pools, exposing higher bulk density (BD) mineral soils with lower %Corg and %N. Consequently, young scars (1–3 years) had significantly lower %Corg and %N values in the top 20 cm of soil compared with undisturbed soils, but the greater BD offset these changes, leading to no differences in total Corg and N pools in the top 1 m between scarred and undisturbed soils. Scars 10+ years had similar %Corg, %N, and BD soil characteristics to undisturbed soils, producing similar Corg and N pools in both upper and lower soil horizons. These findings indicate that recovery of Corg and N pools of prop-scarred seagrass soils within T. testudinum beds of the LLM will likely recover a decade or more post-disturbance. Our findings contribute to the growing global database on seagrass C and N storage and demonstrate the rate at which seagrass meadows recover post-disturbance. Keywords Soil disturbance . Boat propeller scarring . Blue carbon . Turtlegrass
Introduction Communicated by Masahiro Nakaoka Electronic supplementary material The online version of this article (https://doi.org/10.1007/s12237-020-00765-6) contains supplementary material, which is available to authorized users. * Rachel N. Arney [email protected] 1
Department of Geography, University of Georgia, 210 Field Street #204, Athens, GA 30602, USA
2
New Jersey Department of Environmental Protection, Division of Fish and Wildlife, 360 N. New York Rd, Galloway, NJ 08205, USA
3
Department of Forestry, Forest and Wildlife Research Center, Mississippi State University, 775 Stone Blvd, Mississipp, MS 39762, USA
4
School of Earth, Environmental, and Marine Sciences, The University of Texas at Rio Grande Valley, One West University Blvd, Brownsville, TX 78520, USA
Seagrass eco
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