Origins and pathways of the subsurface and intermediate water masses of the Indonesian Throughflow derived from historical and Argo data

On the basis of Argo data and historic temperature/salinity data from the World Ocean Database 2001 (WOD01 origins and spreading pathways of the subsurface and intermediate water masses in the Indonesian Throughflow (ITF) region were discussed by analyzing distributions of salinity on representative isopycnal layers. Results were shown that, Subsurface water mostly comes from the North Pacific Ocean while the intermediate water originates from both the North and South Pacific Ocean, even possibly from the Indian Ocean. Spreading through tire Sulawesi Sea, the Makassar Strait, and the Flores Sea, the North Pacific subsurface water and the North Pacific Intermediate water dominate the western part of the Indonesian Archipelago. Furthermore its the depth increases, the features of the North Pacific sourced water masses become more obvious. In the eastern part of the waters, high salinity South Pacific subsurface water is blocked by a strong salinity front between Halmahera and New Guinea. Intermediate water in the eastern interior region owns salinity higher than the North Pacific intermediate water and the antarctic intermediate water (AAIW), possibly coming from the vertical mixing between subsurface water and the AAIW from the Pacific Ocean, and possibly coming front the northward extending of the AAIW front the Indian Ocean as well.

Distribution patterns of chlorophyll a in spring and autumn in association with hydrological features in the southern Yellow Sea and northern East China Sea

Two field studies were conducted to measure pigments in the Southern Yellow Sea (SYS) and the northern East China Sea (NECS) in April (spring) and September (autumn) to evaluate the distribution pattern of phytoplankton stock (Chl a concentration) and the impact of hydrological features such as water mass, mixing and tidal front on these patterns. The results indicated that the Chl a concentration was 2.43 +/- 2.64 (Mean +/- SD) mg m(-3) in April (range, 0.35 to 17.02 mg m(-3)) and 1.75 +/- 3.10 mg m(-3) in September (from 0.07 to 36.54 mg m(-3)) in 2003. Additionally, four areas with higher Chl a concentrations were observed in the surface water in April, while two were observed in September, and these areas were located within or near the point at which different water masses converged (temperature front area). The distribution pattern of Chl a was generally consistent between onshore and offshore stations at different depths in April and September. Specifically, higher Chl a concentrations were observed along the coastal line in September, which consisted of a mixing area and a tidal front area, although the distributional pattern of Chl a concentrations varied along transects in April. The maximum Chl a concentration at each station was observed in the surface and subsurface layer (0-10 m) for onshore stations and the thermocline layer (10-30 m) for offshore stations in September, while the greatest concentrations were generally observed in surface and subsurface water (0-10 m) in April. The formation of the Chl a distributional pattern in the SYS and NECS and its relationship with possible influencing factors is also discussed. Although physical forces had a close relationship with Chl a distribution, more data are required to clearly and comprehensively elucidate the spatial pattern dynamics of Chl a in the SYS and NECS.

The Yellow Sea cold bottom water - an oversummering site for Calanus sinicus (Copepoda, Crustacea)

The vertical distribution and stage-specific abundance of Calanus sinicus were investigated on three key transects in the southern Yellow Sea and the northern East China Sea in August 1999. The results showed that in summer C. sinicus shrank its distribution area to the central cold (less than or equal to10degreesC) bottom water in the Yellow Sea, i.e. the Yellow Sea Cold Bottom Water, remaining in high abundance (345.7 ind m(-3)). In the northern East China Sea on a transect from the mouth of the Yangtze River to the Okinawa trench, only a few individuals appeared in the inner side and none had been found either in the upper layer or in the deep layer of the outer shelf area. The population of C. sinicus in YSCBW consisted of mainly adults (46.83%) and C5 (37.41%). C1-C4 only accounted for 15.76%. The low proportion of the earlier copepodite stages and the high female:male ratio (11.39) indicated that the reproduction of C. sinicus in YSCBW was at a very low level due to the low temperature and low food concentration. It is concluded that the dramatic decrease of C. sinicus population in the shelf area of China seas in summer is caused by the shrinkage of its distribution area and the YSCBW served as an oversummering site.

Seasonal and spatial variation in abundance and egg production of Paracalanus parvus (Copepoda: Calanoida) in/out Jiaozhou Bay, China

The spatial distribution of stage-specific abundance and reproduction of the copepod Paracalanus parvus were studied from October 2005 to September 2006 in the Jiaozhou Bay. This copepod occurred continuously in this bay throughout the year. The species reached the lowest abundance in April and peaked in June. From October to December, distribution center mainly occurred in offshore water and at the mouth of the bay. In winter, early copepodites and adults gradually decreased and till February, most of the population was only comprised of CIV-CV stages. Overwintering copepodites matured in March and males tended to mature before female. From May to September, each stage occurred in the population and gradually reached high abundance. Temperature and chlorophyll a (Chl-a) concentration in the three stations can't clearly explain the seasonal variation in stage-specific abundance, so we surmised the important effect of the Yellow Sea. Egg production rate (EPR) reached its lowest in winter and peaked in June at 60.8 eggs female(-1) day(-1) in nearshore water. In the warming period, EPR in nearshore water was statistically higher and EPR > 10 eggs female(-1) day(-1) lasted longer than that in offshore water, showing the importance of nearshore water for recruitment of R parvus. Our study showed that EPR was positively related to temperature and total chlorophyll a in offshore water and mouth of the bay. In nearshore water, the relationships between EPR and temperature and Chl-a in three size fractions were not the same as those in offshore water, suggesting complicated ecosystem in such a eutrophic area in warming period. (C) 2008 Elsevier Ltd. All rights reserved.

Survival, growth and immune activity of scallop Chlamys farreri cultured at different depths in Haizhou Bay (Yellow Sea, China) during hot season

Survival, growth and immune response of the scallop, Chlamys farreri, cultured in lantern nets at five different depths (2, 5, 10, 15, and 20 m below the sea surface) were studied in Haizhou Bay during the hot season (summer and autumn) of 2007. Survival and growth rates were quantified bimonthly. Immune activities in hemolymph (superoxide dismutase (SOD) and acid phosphatase (ACP)) were measured to evaluate the health of scallops at the end of the study. Environmental parameters at the five depths were also monitored during the experiment. Mortalities mainly occurred during summer. Survival of scallops suspended at 15 m (78.0%) and 20 m (86.7%) was significantly higher than at 2 m (62.9%), 5 m (60.8%) or 10 m (66.8%) at the end of the study. Mean shell height grew significantly faster at 10 m (205.0 mu m/d) and 20 m (236.9 mu m/d) than at 2, 5 or 15 m in summer (July 9 to September 1); however, shell growth rate at 20 m was significantly lower than at the other four depths in autumn (September 2 to November 6). In contrast to summer, scallops at 5 m grew faster (262.9 mu m/d) during autumn. The growth of soft tissue at different depths showed a similar trend to the shell. Growth rates of shell height and soft tissue were faster in autumn than in summer, with the exception of shell height at 20 m. SOD activity of scallops increased with depth, and ACP activity was significantly higher at 15 and 20 m than at other depths, which suggests that scallops were healthier near the bottom. Factors explaining the depth-related mortality and growth of scallops are also discussed. We conclude that the mass mortality of scallop, C. farreri, during summer can be prevented by moving the culture area to deeper water and yield can be maximized by suspending the scallops in deep water during summer and then transferring them to shallow water in autumn.