Review on Using of Macro Algae (seaweeds) in Fish Nutrition

Currently,the search is on for alternative sources of feed ingredients,the main reasons being the increasing cost and uncertainty about the continuous supply of common feed ingredients especially fishmeal and soybean meal.The importance of macro algae or seaweeds as a potential substitute protein source for fish nutrition cultured has been documented in recent years.Macro algae are receiving consideration for their essential amino acid content and high protein value,trace metals and vitamins in fish nutrition.In addition,macro algae or seaweeds could be a potential low cost source of protein for fishes.Furthermore,the economic comparison of feed cost revealed that the increase in the level of dried and fresh seaweeds in alternative feeding treatments,and commercial diets used for fish growth have decreased which led to a significant decrease in the cost of feed.From the results of previous studies,using of macro algae(seaweeds)in fish diets may improves growth performance,feed efficiency,physiological activity,carcass quality,disease resistance and reduced stress response.This review describes effects of using of macro algae(seaweeds)in diets on growth performance of fish.

Antibacterial activity of selected marine macro algae against vancomycin resistant Enterococcus faecalis

Objective:To evaluate the antibacterial activity of different extracts of Caulerpa chemnitzia(Epser)J.V.Lamououx,Caulerpa racemosa(Frosk.)Weber-van-Bosse(C.racemosa),Caulerpa scalpelliformis(R.Br.)Weber-van-Bosse,Ulva lactuca Lin,Ulva fasciata Dellie,Ulva reticulata Forsk,Stoechospermum marginatum(Ag.)Kutz(S.marginatum),Sargassum wightii Grev,Gracilaria verrucosa(Huds.)Papenfuss and Gracilaria edulis(S.G.Gemelin)P.C.Silva against Enterococcus faecalis(MTCC 439)(E.faecalis)and one clinical isolate of vancomycin resistant E.faecalis.Methods:The selected marine macro algae were extracted with different solvents viz.,hexane,chloroform,ethyl acetate,acetone and methanol.Antibacterial assay was carried out by using disc diffusion method,determination of minimum inhibitory concentration and minimum bactericidal concentration.Results:The maximum antibacterial activity was recorded in the ethyl acetate extracts of S.marginatum and C.racemosa than the other extracts.The mean zone of inhibition produced by the extracts in agar diffusion assays against the tested bacterial strains ranged from 7.1 to 14.5 mm.The minimum inhibitory concentration was between 250 and 500μg/mL,while the minimum bactericidal concentration was from 500 to 1000μg/mL.The ethyl acetate extracts of the seaweeds showed the presence of strong terpenoids,tannins and phenolic compounds compared with the other solvent extracts.Conclusions:These findings suggest that ethyl acetate extracts of S.marginatum and C.racemosa can be used as an antibacterial substance for the treatment of infection caused by E.faecalis.

Spatiotemporal distribution and influencing factors of Ulva prolifera and Sargassum and their coexistence in the South Yellow Sea,China

Marine ecological disasters occurred frequently in recent years and raised widespread concerns about the ecological health of the ocean.We analyzed the spatiotemporal distributions of Ulva prolifera and Sargassum from April to July each year between 2016 and 2020 in the South Yellow Sea using multisource(GF-1 and HJ-1A/1B)remote sensing images,combined with the MODIS sea surface temperature(SST)data,photosynthetically active radiation(PAR)data,and Quick SCAT sea surface wind(SSW)data,to explore the potential influencing factors.The results show that(1)U.prolifera and Sargassum appeared mainly from May to July and April to June,respectively;(2)U.prolifera showed an impact in larger spatial scope than that of Sargassum.U.prolifera originated in the shoal area of northern Jiangsu and finally disappeared in the sea near Haiyang-Rongcheng area.The spatial scope of the impact of Sargassum tended to expand.Sargassum was first detected in the ocean northeast of the Changjiang(Yangtze)River estuary and disappeared near 35°N;and(3)correlation analysis showed that the SST influenced the growth rate of U.prolifera and Sargassum.PAR had varied eff ects on U.prolifera and Sargassum at different times.A moderate light conditions could accelerate the growth and reproduction of U.prolifera and Sargassum.High irradiance levels of ultraviolet radiation may cause photoinhibition and damage on U.prolifera and Sargassum.The southeast monsoon and surface currents promoted the drift of U.prolifera and Sargassum from the southeast to the northwest and north.Therefore,the spatial and temporal similarities and differences between U.prolifera and Sargassum were influenced by a combination of factors during their growth processes.