Can ecosystem functional recovery be traced to decomposition and nitrogen dynamics in estuaries of the Lower Laguna Madre, Texas?
The biggest incentive to attempt the restoration and protection of estuaries is their widely acknowledged ecological and economic importance. Assessing estuary health and recovery can most accurately come from examining ecosystem processes. The purpose of this study was to explore the potential of mass loss and nitrogen (N) dynamics during leaf litter decomposition, to detect signs of functional recovery in two estuarine systems in south Texas. Submerged litterbags with black mangrove (Avicennia germinans) leaves were retrieved at various dates over 320 days. Decomposition was about 50% slower in one of the recovering systems compared to a reference site. Nitrogen immobilization and release from decaying leaf litter also discriminated among sites. Nitrogen immobilization potentials ranged from 4.15 to 6.89 mgN/g leaf litter, with the reference site exhibiting the highest value and thus the highest potential to conserve N during litter decomposition. The reference site also had a N immobilization time twice as long as the recovering sites, and a slower net release after the immobilization, appearing again as the most conservative in this part of the N cycling, possibly pointing to a less disturbed, or more stable ecosystem. Overall, the N dynamics during decomposition of mangrove leaf litter were similar in both recovering sites, whereas the reference site had a more conservative nutrient dynamics with more N being retained for longer in decomposing litter, coupled with a slower net release. Metrics derived from N dynamics may provide a finer resolution assessment of functional recovery, than only decomposition metrics.
Implications for Practice
- Metrics derived from decomposition and concurrent N dynamics have the potential to be effective indicators of functional recovery in estuaries.
- Nitrogen immobilization potential, immobilization time, and release rates may be more accurate tracers of estuarine system recovery than mass loss rates.
- Decomposition and nutrient net immobilization and release are processes that can be quantified with relative ease and could be included in assessments of restoration efforts.
- Stable isotope analyses can detect more subtle differences in N dynamics during litter decay.
Marquez, M.A., Fierro-Cabo, A. and Cintra-Buenrostro, C.E. (2017), Can ecosystem functional recovery be traced to decomposition and nitrogen dynamics in estuaries of the Lower Laguna Madre, Texas?. Restor Ecol, 25: 618-628. https://doi.org/10.1111/rec.12469