Abstract:

In order to study the spatial and temporal variations of invertebrate community structure and diversity in the Yangtze River Estuary and its adjacent waters, we investigated invertebrate populations using fixed double bottom trawling during the springs of 1999-2012. Results show that: (1) there were 41 invertebrate species recorded, belonging to 6 classes, 10 orders, and 23 families. Crustaceans were the most recorded species (26 species), followed by mollusks (13 species). The number of recorded species decreased over the sampling period; (2) dominant invertebrates included Loligo japonica, Portunus trituberculatus, Palaemon gravieri, and Trachypenaeus curvirostris. There was significant inter-annual variation but Loligo japonica was the most dominant species across the sampling period; (3) there was significant inter-annual variation in invertebrate abundance, species richness and diversity in the estuary. Abundance, species richness and diversity peaked in 1999 and 2001, and increased after 2004; (4) there were 2 or 3 species assemblages in the estuary, which had different indicator species; (5) the temporal variation in the invertebrate community can be divided into three distinct periods. 1999-2001 featured high species diversity, 2004-2007 saw a decrease to the lowest species diversity, and by 2009-2012 diversity had recovered but was still below the level of 1999-2001. A decline in crab populations has resulted in the decline of overall invertebrate biomass, while deficiencies at high trophic levels has promoted a diversification of invertebrate diet.

Key words: invertebrate, diversity, assemblages, Yangtze River Estuary