Surface water temperature ranged from 10.15°C to 19.76°C (average (13.70±2.24)°C). Higher temperatures occurred nearer shore in each bay; lower temperatures occurred in the central sea (Fig. 2). The comparison of average temperature among the three bays showed that the highest average temperature occurred in the Laizhou Bay, and lowest in the Liaodong Bay (Fig. 3).
Figure 2. Spatial distribution of temperature (°C, a), salinity (b) and Chl a concentration (μg/L, c) in surface waters of the Bohai Sea.
Figure 3. Average temperature (a), salinity (b) and Chl a concentration (c) in the Bohai Bay (BHB), Laizhou Bay (LZB) and Liaodong Bay (LDB).
Surface water salinity ranged from 26.97 to 31.19 (averaging 29.69±1.05). Salinity was higher in the central sea and lower in each bay, and lowest average salinity occurred in the Laizhou Bay (Fig. 3). The distribution of temperature and salinity in surface waters showed that a weak flow of low temperature, high salinity water intruded into the central Bohai Sea (Fig. 2).
Chl a concentration ranged from 0.89 μg/L to 11.87 μg/L (average (3.8±2.62) μg/L), with higher values occurring mainly in coastal waters (Fig. 2). The average Chl a concentration was higher in the Bohai Bay and Laizhou Bay than in the Liaodong Bay (Fig. 3).
Three genera and 11 tintinnid species were identified in samples (Table 1, Fig. 4). Only two tintinnid geographical types were found in the Bohai Sea, i.e., neritic and cosmopolitan tintinnids. In terms of abundance in whole Bohai Sea, neritic tintinnids were more abundant than cosmopolitan ones, comprised 79.5% and 20.5% of total abundance, respectively.
Dominance index Cosmopolitan Codonellopsis lusitanica 168 0.08 0.00 C. mobilis 118 0.40 0.03 Neritic Tintinnidium
41 0.14 0.01 Tintinnopsis baltica 1 219 0.27 0.19 T. beroidea 8 0.31 0.00 T. brasiliensis 6 0.06 0.00 T. directa 8 0.02 0.00 T. kofoidi 3 0.02 0.00 T. lohmanni 8 0.06 0.00 T. radix 3 0.02 0.00 T. rapa 217 0.33 0.03
Table 1. List of tintinnid species in the Bohai Sea
Figure 4. Photos of tintinnid species in the Bohai Sea. a. Tintinnopsis radix, b. Tintinnopsis kofoidi, c. Tintinnidium mucicola, d. Codonellopsis mobilis, e. Tintinnopsis lohmanni, f. Tintinnopsis brasiliensis, g. Codonellopsis lusitanica, h. Tintinnopsis directa, i. Tintinnopsis rapa, j. Tintinnopsis baltica, and k. Tintinnopsis beroidea. Scale bar: 20 μm.
Tintinnopsis baltica, C. mobilis and T. rapa represent the three most dominant species according to dominance index. Tintinnopsis baltica was more abundant in waters with temperature of 15–20°C (Fig. 5), and the maximum abundance was recorded in the Laizhou Bay (Fig. 6). Codonellopsis mobilis was more abundant in waters with temperature of 10–17°C (Fig. 5) with maximum abundance in the Liaodong Bay (Fig. 6). Tintinnopsis rapa was more abundant in waters of 10–17°C (Fig. 5), and the maximum abundance was recorded in the Liaodong Bay (Fig. 6).
Figure 5. Relationship between tintinnid abundance and temperature. a. Tintinnopsis baltica, b. Codonellopsis mobilis, and c. Tintinnopsis rapa.
Tintinnid assemblages and some dominant taxa differed among the three bays. In the Bohai Bay, Tintinnopsis baltica was dominant, contributing 79.5% to total tintinnid abundance. In the Laizhou Bay, Tintinnopsis baltica was also dominant, with a contribution of 85.8% to total tintinnid abundance. In the Liaodong Bay, Tintinnopsis rapa and Codonellopsis mobilis contributed 53.4% and 37.1% to total tintinnid abundance, respectively (Fig. 7). Average abundance of tintinnids was highest in the Laizhou Bay ((328±445) ind./L), where the value was ~1.3 and 8.8 times higher than that in the Bohai Bay ((143±297) ind./L) and Liaodong Bay ((34±57) ind./L), respectively.
Figure 7. Percentage of each species among total tintinnid abundance in the Bohai Bay (BHB), Laizhou Bay (LZB) and Liaodong Bay (LDB).
Using Bray-Curtis similarity index and cluster analysis, stations (except for stations with no tintinnid recorded) were clustered into three groups. Group I mainly included most stations in the Bohai Bay (except for Stations I1 and I2) and some stations in the central sea adjacent to the Bohai Bay. Group II mainly included most stations in the Liaodong Bay (except for Stations D3, E2, F3, F4, and G3). Group III mainly included most stations in the Laizhou Bay (except for Stations M3 and N1) and some stations in the central sea adjacent to the Laizhou Bay (Figs 1 and 8). Each group represented tintinnid community from single bay and its adjacent area, and three groups tended to converge in the central sea.
Average species richness throughout the Bohai Sea was 2. Species richness was greater in bays than in deeper central-sea waters. No tintinnid occurred in some stations of central sea (Fig. 9a). Average abundance throughout the sea was (81±216) ind./L (0–1 234 ind./L). Higher abundance of total tintinnids was distributed in bays, especially near the Huanghe River Estuary. Tintinnid abundance was low in the central Bohai Sea, with average abundance of (14±37) ind./L (Fig. 9b).
Tintinnid community throughout the Bohai Sea during the spring
- Received Date: 2018-12-29
- Accepted Date: 2019-05-06
- Available Online: 2020-12-28
- Publish Date: 2020-06-25
Abstract: As one of the important microzooplankton in marine pelagic habitats, tintinnids are classified as neritic genera, oceanic genera and cosmopolitan genera. Until now, we know little about the interaction between neritic and oceanic genera in continental shelves. Low species richness area was found in the mixing area between neritic and oceanic genera in the East China Sea. In this study, we investigated the spatial distribution of tintinnid community throughout the entire Bohai Sea in May (spring) of 2014 to find out: (1) whether the tintinnid assembalges differed in the three major bays bordering this shallow inland sea; (2) whether there was low species richness area in the Bohai Sea. Three genera and 11 species attributed to neritic and cosmopolitan taxa were reported from this region. Tintinnid abundance averaged (81±216) ind./L (0–1 234 ind./L). Tintinnid community differed within the three major bays, with each characterized by different tintinnid taxa. Referring to the average abundance of three bays, tintinnids were most abundant in the Laizhou Bay ((328±445) ind./L), and least abundant in the Liaodong Bay ((34±57) ind./L). A low species richness area occurred in the central Bohai Sea (20–40 m isobaths), in some stations of which no tintinnid was recorded. Our study demonstrates that tintinnid community varied greatly over small spatial scales, and low species richness area was found in the mixing area between neritic and oceanic genera within this inland sea.
|Citation:||Ying Yu, Feng Zhou, Wuchang Zhang, Chen Wei, Qunshan Wang, Enjun Fang. Tintinnid community throughout the Bohai Sea during the spring[J]. Acta Oceanologica Sinica, 2020, 39(6): 65-71. doi: 10.1007/s13131-020-1588-y|