Abstract:

We analyzed and compared the differences in community composition, K-dominance curves and diversity index (H') of zooplankton community structure characteristics inside and outside the Hangzhou Bay in autumn (outside the bay: 122.10°-122.58° E, 30.54°-30.93° N; inside the bay: the east area of north: 121.67°-121.87° E, 30.68°-30.83° N; the east area of south: 121.60°-121.85° E, 29.95°-30.24° N; the west area of north: 121.31°-121.56° E, 30.58°-30.77° N). Results indicated that there were large differences between the community composition of zooplankton outside the bay and those in the three areas inside the bay. The area outside the bay (community I) was composed of nearshore species such as Pseudeuphausia sinica and nearshore low-salinity species such as Centropages dorsispinatus, followed by offshore species. Community II (the eastern area of south Hangzhou Bay) was composed of nearshore low-salinity species such as Labidocera sinilobata, followed by nearshore species. Community III (the eastern area of north Hangzhou Bay) was mixed with nearshore low-salinity species such as Labidocera euchaeta and estuarine brackish-water species such as Tortanus vermiculus. Community IV (the western area of north Hangzhou Bay) was characterized by the dominant species, Tortanus vermiculus of estuarine brackish-water species that had the highest proportion, which was different from the community I. Generally, the community with lower salinity adaptability appeared in the western and northern areas. According to K-dominance curves, the dominance curves of community I and community III were quite gentle. In addition, the initial cumulative dominance of community III was higher than that of community I. Compared with community I, the initial cumulative dominance of community II and community IV were far higher than that of community I. The initial cumulative dominance of community I (outside the bay) was particularly low, which indicated that there were many types of dominant species in community I, and the dominance of single dominant species was lower than those communities inside the bay. Results of variance analysis indicated that there were highly significant differences between the diversity index of zooplankton outside the bay and those in the other three waters inside the bay (P < 0.01). Meanwhile, there were no significant differences between the three communities inside the bay (P > 0.05). This showed that the diversity index of zooplankton outside the bay was higher than those of the communities inside the bay. The influence of different water masses resulted in zooplankton community differences in the inner and outer waters of the bay.

Key words: Hangzhou Bay, community, cumulative dominance, zooplankton, diversity