Abstract:

Based on data from benthic trawling in Daya Bay between 2004 and 2015, the temporal and spatial characteristics of species composition and diversity were analyzed. A total of 429 species of marine animals were identified, belonging to 10 phyla, 16 classes, 175 families, and 309 genera. Species numbers varied between 75-114 in Daya Bay between 2004 and 2015. Chordata, Arthropoda, and Mollusca were the dominant phyla from 2004 to 2015, respectively. Species numbers showed a decreasing trend from 2004 to 2015. In the spring, the species number was higher in the western part of Daya Bay than the eastern region before 2007. More recently, the species number was higher in the mouth and the eastern parts of Daya Bay than the northern and western regions. In the summer, the species numbers increased in the southwestern region of the bay before 2008, but after 2009 results showed that the species number was higher in the mouth of the bay than the inner region. Timoclea imbricata or Paphia undulata were the first dominant species in spring. In summer, the first dominant species varied before 2007, but Turritella bacillum was the most dominant species after 2008. In autumn, Timoclea imbricata or Turritella bacillum was the first dominant species. The average Shannon-Wiener diversity index (H'), Pielou’s evenness index (J'), and species richness index (d) varied between 1.46-4.05, 0.30-0.89 and 2.49-6.69, respectively. Diversity decreased in Daya Bay between 2004 and 2015, especially in the northwestern area, mainly due to heavy anthropogenic activities. In recent years, the species resources of some areas of Daya Bay contribute mostly to the function of species diversity of the whole bay in the past, and benthic ecosystems have become more fragile.

Key words: South China Sea, macrobenthos, qualitative investigation, species diversity, dominant species