Distribution characteristics and influencing factors of benthic diatoms on several typical beaches along the southern coast of China

Benthic diatoms are the primary beach vegetation on sandy coasts, acting as the main primary producers in such environments. Changes in their community structure and biomass can have substantial impact on both the entire micro-food web and the nearshore shallow marine ecosystem. This study focused on four typical beaches along the southern coast of China (Fuzhou Changle Beach, Xiamen Huizhan Beach, Xiamen Guanyinshan Beach, and Beihai Silver Beach). Analysis of benthic diatoms and environmental factors revealed that the distribution of benthic diatom communities on the studied beaches is influenced by elevation, salinity changes due to freshwater inputs, sediment composition, and hydrodynamic factors. The most important factor is elevation, which reflects the location of the beach in the tidal zone. On Beihai Silver Beach and the Xiamen beaches, the mid-tidal and low tidal zones are more conducive to growth and reproduction of benthic diatoms, and some diatom species show preference for different tidal zones. On dissipative beaches, benthic diatom abundance peaks in the mid-tidal zone, whereas on low tidal terrace beaches, diatom abundance is generally low in the high tidal zone and relatively high in the low tidal zone. Additionally, low tidal terrace beaches exhibit a “steep increase zone” of diatom abundance at the junction of the steep and gentle slopes, indicating that benthic diatom abundance responds more to this type of beach landform than to that of dissipative beaches.