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An epiphytic gammarid species, Apohyale sp., was abundant in the floating Ulva prolifera (U. prolifera), which forms large-scale green tides in the Yellow Sea (YSGT). Field observation and laboratory experiments were subsequently conducted to study the species identity, abundance, and grazing effects on the floating algal biomass. The abundance of Apohyale sp. showed great spatial variation and varied from 0.03 to 1.47 inds g−1 in the YSGT. In average, each gram of Apohyale sp. body mass can consume 0.43 and 0.60 g algal mass of U. prolifera per day, and the grazing rates varied among the algae cultured with different nutritional seawaters. It was estimated that grazing of Apohyale sp. could efficiently reduce ~0.4 and 16.6% of the algal growth rates in Rudong and Qingdao, respectively. The U. prolifera fragments resulting from gnawing of Apohyale sp. had a higher growth rate and similar photosynthetic activities compared to the floating algae, indicating probably positive feedback on the floating algal biomass. This research corroborated the significant impact of Apohyale sp. on the floating algal mass of YSGT through the top-down control. However, further research is needed to understand the population dynamics of these primary predators and hence their correlation with the expansion or decline of YSGT, especially under the complex food webs in the southern Yellow Sea. [ABSTRACT FROM AUTHOR]

A 42‐day feeding trial was conducted to investigate the effects of supplementation with various additives from Bacillus cereus A4 (fermentation supernatant, FS; live cells, BC; spores, BS; and cell‐free extract, CE) on the growth performance, intestinal morphology, digestive enzyme activities, immune responses and disease resistance of Litopenaeus vannamei (initial weight approximately 2.34 g). The results indicated that the growth performance of shrimp in BC, BS and CE groups improved significantly and no significant difference was observed between the control and FS groups. The villus height of the shrimp mid‐intestine in the FS, BC, BS and CE groups improved significantly compared with the control, and the maximum intestinal wall thickness was observed in BS group. Compared to the control, the activities of amylase, trypsin, lipase, acid phosphatase (ACP), alkaline phosphatase (AKP), superoxide dismutase, lysozyme and total nitric oxide synthase and the relative expression levels of Immune deficiency (Imd), Toll and Relish genes in shrimp of BC, BS and CE groups enhanced significantly. The activities of amylase, trypsin, ACP, AKP and the relative expression levels of Imd, Toll and Relish genes in shrimp of BC and BS groups were significantly higher than those of other groups. In the challenge test against Vibrio parahaemolyticus, the cumulative mortality of shrimp in BC and BS groups was significantly lower compared with that of other groups. Thus, the live cells and spores of B. cereus A4 provided superior probiotic benefits to L. vannamei, including improvements in growth, intestinal morphology, digestive enzyme activities, disease resistance and immune responses. [ABSTRACT FROM AUTHOR]