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Oyster reefs have the potential as eco-engineers to improve coastal protection. A field experiment was undertaken to assess the benefit of oyster breakwater reefs to mitigate shoreline erosion in a monsoon-dominated subtropical system. Three breakwater reefs with recruited oysters were deployed on an eroding intertidal mudflat at Kutubdia Island, the southeast Bangladesh coast. Data were collected on wave dissipation by the reef structures, changes in shoreline profile, erosion-accretion patterns, and lateral saltmarsh movement and related growth. This was done over four seasons, including the rainy monsoon period. The observed wave heights in the study area ranged 0.1–0.5 m. The reefs were able to dissipate wave energy and act as breakwaters for tidal water levels between 0.5–1.0 m. Waves were totally blocked by the vertical relief of the reefs at water levels <0.5 m. On the lee side of the reefs, there was accretion of 29 cm clayey sediments with erosion reduction of 54% as compared to control sites. The changes caused by the deployed reefs also facilitated seaward expansion of the salt marsh. This study showed that breakwater oyster reefs can reduce erosion, trap suspended sediment, and support seaward saltmarsh expansion demonstrating the potential as a nature-based solution for protecting the subtropical coastlines.

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The efficacy of cellular components of probiotics Kocuria SM1 and Rhodococcus SM2 to protect rainbow trout (Oncorhynchus mykiss, Walbaum) against vibriosis was assessed. Groups of fish (average weight = 10–15 g) were immunized intraperitoneally (i.p.) with 0.1 ml of subcellular materials, i.e. 0.2 ± 0.05 mg protein per fish, comprising extracellular proteins (ECPs), cell wall proteins (CWPs) and whole cell proteins (WCPs) of SM1 and SM2, respectively, or with 0.1 ml of phosphate-buffered saline (PBS) to serve as the control. Seven days after administration, fish from each group were challenged i.p. with 0.1 ml of a suspension in PBS of 3 × 105 cells ml−1 per fish of Vibrio anguillarum. Use of CWPs and WCPs demonstrated significantly (P < 0.05) better protection against V. anguillarum insofar as mortalities were reduced to 11–17% [relative percent survival (RPS) = 80–87%], although ECPs fared less well (mortalities = 33–38%; RPS = 56–62%; P > 0.05), compared to 86% mortalities of the controls. The mode of action reflected activation of innate immune factors by CWPs and WCPs, demonstrating significantly (P < 0.05) increased expression of respiratory burst (optical density; OD550nm) from 0.039 to 0.043–0.045, peroxidase (OD550nm) from 0.26 to 0.37–0.55, and bacterial killing activities (i.e. percentage of surviving bacteria reduced from 79% to 56–57% for SM2). Moreover, an elevation of leucocyte number (from 1.93% to 1.98–2.93%; P > 0.05) and immunoglubolin level (from 27 mg ml−1 to 28.5–33 mg ml−1; P > 0.05) were observed with the experimental groups. These results indicate that cell components of the probiotics stimulate an immune response

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Aims: To develop probiotics for the control of vibriosis caused by Vibrio anguillarum and Vibrio ordalii in finfish. Methods and Results: Kocuria SM1, isolated from the digestive tract of rainbow trout, was administered orally to rainbow trout (Oncorhynchus mykiss) for 2 weeks at a dose equivalent to c. 10 8 cells per g of feed and then challenged intraperitoneally with V. anguillarum and V. ordalii. Use of SM1 led to a reduction in mortalities to 15-20% compared to 74-80% mortalities in the controls. SM1 stimulated both cellular and humoral immune responses in rainbow trout, by elevation of leucocytes (5AE5 ± 0AE8 · 10 6 ml )1 from 3AE7 ± 0AE8 · 10 6 ml )1 ), erythrocytes (1AE2 ± 0AE1 · 10 8 ml )1 from 0AE8 ± 0AE1 · 10 8 ml )1 ), protein (23 ± 4AE4 mg ml )1 from 16 ± 1AE3 mg ml )1 ), globulin (15AE7 ± 0AE2 mg ml )1 from 9AE9 ± 0AE1 mg ml )1 ) and albumin (7AE3 ± 0AE2 mg ml )1 from 6AE1 ± 0AE1 mg ml )1 ) levels, upregulation of respiratory burst (0AE05 ± 0AE01 from 0AE02 ± 0AE01), complement (56 ± 7AE2 units ml )1 from 40 ± 8AE0 units ml )1 ), lysozyme (920 ± 128AE8 units ml )1 from 760 ± 115AE3 units ml )1 ) and bacterial killing activities.Conclusions: Kocuria SM1 successfully controlled vibriosis in rainbow trout, and the mode of action reflected stimulation of the host innate immune system. Significance and Impact of the Study: Probiotics can contribute a significant role in fish disease control strategies, and their use may replace some of the inhibitory chemicals currently used in fish farms.

Subcellular components of the probiotics Aeromonas sobria GC2 and Bacillus subtilis JB-1, when administered to rainbow trout, Oncorhynchus mykiss, conferred protection against a new biogroup of Yersinia ruckeri. Thus, intraperitoneal or intramuscular injection of rainbow trout with cell wall proteins (CWPs), outer membrane proteins (OMPs), lipopolysaccharides (LPS), whole cell proteins (WCPs) and live cells followed by challenge on day 8 with Y. ruckeri led to 80-100% survival compared with 10% survival in the controls. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) profiles of WCPs and OMPs from GC2 had 10 and 5 variable protein bands in comparison to 11 and 5 bands in the WCPs and CWPs from JB-1. Proteomic analyses were employed following SDS-PAGE to categorize one dominant protein of 104.7 kDa from the CWPs of JB-1 and equated it with 'Bacillus spp. endoglucanase' with a Mascot score >69. These results point to the potential of using cellular components of probiotics for protection of fish against bacterial diseases.