Photosynthetic characteristics of mangrove seedlings in chronosequence of restored and recolonized stands under field conditions
| Authors: | Maria Elisa Gerona-Daga, Richard A. MacKenzie, Severino G. Salmo III |
| Year: | 2025 |
| Type: | Scientific Journal |
| Station: | Pacific Southwest Research Station |
| DOI: | https://doi.org/10.5343/bms.2024.0020 |
| Source: | Bulletin of Marine Science. |
Abstract
Mangrove forests are the dominant ecosystems on tropical and subtropical coasts, subjected to widespread degradation and land conversion, such as aquaculture. To restore mangrove cover, mangrove seedlings were planted in coastal fringes and abandoned ponds. Most restoration reports were focused on seedling survival and growth rates. However, physiological conditions of mangrove seedlings, in terms of photosynthetic characteristics under field conditions has seldom been studied. Mangrove seedlings from restored “planted” (5 ,8, 15, and 30 yr old) and recolonized (5 and 20 yr old) stands were monitored for a year to assess their photosynthetic performance. These were compared with a reference system consisting of mature, natural stands of unknown ages. Chlorophyll fluorescence–based parameters, leaf temperature differential (LTD), and relative chlorophyll content (SPAD) were measured. At younger restored and recolonized stands, actual photosystem II (PSII) efficiency (Phi2) and PSII maximum efficiency (Fv’/Fm’) of the seedling leaves were lower compared to natural stands. Yield of nonregulatory energy dissipation (PhiNO) and electron transport rates (ETRPSII) were higher in younger restored and recolonized stands than natural stands. This suggests excess energy production which can lead to potential damage to photosystems. The lower photosynthetic efficiency and higher potential damage of seedling leaves may reflect suboptimal environmental conditions in both the restored and recolonized stands. The photosynthetic efficiency tended to improve as the age of the stands mature. This study provides the first physiological measurements of mangrove seedlings under different field conditions in the Philippines, and highlights the role of photosynthetic regulation for seedling establishment and growth.