Reconstructed life history metrics of the iconic seagrass Posidonia oceanica (L.) detect localized anthropogenic disturbance signatures

Substantial losses of the seagrass Posidonia oceanica have initiated investigations into localized resilience declines related to anthropogenic disturbances. In this study, we determined reconstructed shoot age and interannual growth metrics can detect anthropogenic impact effects on P. oceanica production. Interannual rhizome vertical growth, leaf production, and demographics of shoots collected from sewage and trawling impacted areas were examined using mixed effects modeling. Detected impact effects were specific to the type of impact, manifesting as an older-skewed age distribution of sewage outfall shoots and reduced vertical growth and reduced leaf production of trawling site shoots. A stress event period was also detected for all shoots >5 years old, with trawling impacted shoots indicating little recovery. Reconstructed age and growth metrics are simple to measure, incorporate multiple years of in situ shoot development, and are advantageous for identification of declining P. oceanica resilience prior to catastrophic losses.

Automated summary

This study found that reconstructed shoot age and interannual growth metrics can detect anthropogenic impact effects on Posidonia oceanica production. The impacts varied depending on the type, with sewage outfall resulting in an older-skewed age distribution and trawling leading to reduced vertical growth and leaf production. A stress event period was detected for older shoots, with little recovery observed in trawling impacted areas. Reconstructed age and growth metrics provide a simple and effective method for identifying declining resilience in P. oceanica before catastrophic losses occur.