LAUSR

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 (C org ) 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 C org 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 %C org and %N. Consequently, young scars (1–3 years) had significantly lower %C org 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 C org and N pools in the top 1 m between scarred and undisturbed soils. Scars 10+ years had similar %C org , %N, and BD soil characteristics to undisturbed soils, producing similar C org and N pools in both upper and lower soil horizons. These findings indicate that recovery of C org 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.