Effects of marine pollution, climate, and tidal range on biomass and sediment organic carbon in Chinese mangrove forests

Abstract

Mangroves are among the most important carbon reservoirs for atmospheric CO2. Nonetheless, how the biomass and sediment organic carbon (SOC) of mangrove forests are affected by marine pollution, in addition to climate and tidal range, on a regional scale is unknown. This study aimed to assess how spatial patterns of biomass and SOC could be influenced by the climate, tidal range, and marine pollution in China’s mangrove forests. The result showed that aboveground biomass (AGB), surface SOC content (SOCC), and SOC density (SOCD) showed clear latitudinal change patterns on a regional scale and decreased in a non-linear manner with increasing latitude. Correlation analysis and principal component analysis (PCA) indicated that latitudinal variation in AGB, SOCC, and SOCD was mainly regulated by temperature-related indicators. However, AGB, SOCC, and SOCD were not found to be correlated to annual precipitation. Besides, the tidal range was found to be negatively correlated to biomass and SOC content/stock. Tidal range is one important abiotic predictor used to understand the latitudinal patterns of mangrove biomass and SOC dynamics. Correlation analysis and PCA revealed that mangrove biomass and SOC content/stock were negatively affected by heavy metal pollution, and they were disproportionately negatively correlated to marine heavy metal concentrations in the coastlines neighboring mangrove forests. Environmentally-sound technology should be adapted to prevent, control, and remediate heavy metal pollution to increase carbon storage in China’s mangrove forests. Mangrove biomass and SOC content/stock were also found to be negatively related to the suspended solid concentration in the coastlines neighboring mangrove forests. In contrast, vegetation biomass was found to be positively correlated to ammonia nitrogen content. However, biomass was found to be not correlated to nitrate-nitrogen, nitrites-nitrogen, inorganic forms of nitrogen, and non-ionic ammonia. Additional studies are needed to confirm the mechanisms by which different forms of nitrogen enrichment affect biomass storage.