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The potential immunostimulatory effects of small peptides on sea cucumber, Apostichopus japonicus, were investigated in vivo and in vitro. Small peptides were injected into sea cucumbers and a control group was injected with equal volume of sterile filtered seawater. The nonspecific humoral and cellular responses were determined, respectively, and sea cucumbers were challenged by Vibrio splendidus. The results showed that test groups significantly enhanced most of the immune parameters tested (P < 0.05). Both phagocytic capacity and respiratory burst activity were up to maximum value on the fourth day and the values were 2.3 and 1.4 times as high as the control group, respectively. However, small peptides had no significant effect on total coelomocytes counts. Among the humoral responses, the activities of acid phosphatase, alkaline phosphatase, and superoxide dismutase were up to maximum value on the fourth, fourthth and seventh day, respectively. The values were 2.3, 2.2, and 2.0 times as high as the control group, respectively. At the end of the challenge, the cumulative mortality rate of sea cucumber injected with 0.5 mg small peptides (43.3%) was significantly lower than the control group (66.7%). In conclusion, small peptides as an additive could improve the nonspecific immunity level of Apostichopus japonicus.

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An empirical algorithm is proposed to estimate suspended particulate matter (SPM) ranging from 0.675 to 25.7 mg L in the turbid Pearl River estuary (PRE). Comparisons between model predicted and in situ measured SPM resulted in Rs of 0.97 and 0.88 and mean absolute percentage errors (MAPEs) of 23.96% and 29.69% by using the calibration and validation data sets, respectively. The developed algorithm demonstrated the highest accuracy when compared with existing ones for turbid coastal waters. The diurnal dynamics of SPM was revealed by applying the proposed algorithm to reflectance data collected by a moored buoy in the PRE. The established algorithm was implemented to Hyperspectral Imager for the Coastal Ocean (HICO) data and the distribution pattern of SPM in the PRE was elucidated. Validation of HICO-derived reflectance data by using concurrent MODIS/Aqua data as a benchmark indicated their reliability. Factors influencing variability of SPM in the PRE were analyzed, which implicated the combined effects of wind, tide, rainfall, and circulation as the cause.

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A MODIS-based algorithm was developed to investigate the impact of Typhoon Vicente on the total suspended solid concentration in the Pearl River Estuary. This algorithm used two high resolution bands at 645 nm and 555 nm to map the concentrations. Regression between the remote sensing reflectance and in situ total suspended solid concentration showed good correlation (R2 = 0.91), indicating that the algorithm was valid for the high turbid waters in the Pearl River Estuary. MODIS-derived maps showed different total suspended solid concentration anomalies in different sub-regions of the estuary during the passage of Typhoon Vicente. In western inlets, the increase of total suspended solids (maximum values of 22.20 g m−3 before and 55.71 g m−3 after the typhoon) was possibly related to the larger rainfall discharge from the Pearl River. In Lingdingyang, the increase of total suspended solids (maximum values of 19.60 g m−3 before and 44.59 g m−3 after the typhoon) might be the result of typhoon-induced resuspension. In the southeastern portion of the Estuary, due to the typhoon-induced current, a significant decrease of total suspended solid area (decreased by 10 g m−3) was observed. Different changes were observed in different sub-regions under the influence of the typhoon, implying the complicated hydrological environment is an important feature in the Pearl River Estuary.

A 4-week feeding trial was conducted to determine the effects of different dietary supplements on the growth, immunity and resistance of sea cucumber Apostichopus japonicus against Vibrio splendidus infection. The control group was supplied with blank microcapsules, and Astragalus polysaccharide (APS) microcapsules, tuckahoe polysaccharide (TPS) microcapsules, (APS ? TPS) microcapsules, (APS ? TPS) microcapsules ? Bacillus subtilis, were tested for effects. Coelomic fluid was collected at 7-day intervals to test activities of lysozyme (LSZ), superoxide dismutase (SOD), alkaline phosphatase (AKP), and complement 3 (C3) content. After the feeding trial, the specific growth rate of sea cucumbers fed a diet supplemented with (APS ? TPS) microcapsules ? B. subtilis was significantly increased (P \ 0.05); activities of LSZ, SOD, AKP and C3 content were significantly higher than in other groups (P \ 0.05). The challenge test showed that the cumulative mortality of sea cucumbers fed a diet supplemented with (APS ? TPS) microcapsules ? B. subtilis reduced significantly (P \ 0.05). In conclusion, dietary combinations of (APS ? TPS) microcapsules ? B. subtilis has a potential for use in diet formulations for sea cucumbers to significantly increase growth, immunity and disease resistance against V. splendidus infection.