Community structure and controlled factor of attached green algae on the Porphyra yezoensis aquaculture rafts in the Subei Shoal, China

This study analyzes the community structure, the quantity changes of the algae and the effect of important environmental factors and estimates the total biomass of the attached green algae in the survey areas. The study uses data from surveys of the attached green algae on the Porphyra yezoensis aquaculture rafts and data regarding the environmental factors from October 2010 to April 2011 in the Subei Shoal. The attached green algae on the rafts included Ulva prolifera, Capsosiphon groenlandicus, U. linza, U. intestinalis, U. clathrata, and U. cornpressa. The biomass changes of the attached green algae exhibited an inverted parabola： the biomass was the highest （14 898 t） in April, and was the second highest （2 034 t） in November; it was lowest in February （only 729 t） and increased sharply from March to April. The species diversity differed significantly among the seasons. In September and October, when the P. yezoensis aquaculture rafts were initially set up, the attached green algae had a high biodiversity, while from December to the next February, a variety of green algae species coexisted on the rafts, although the biomass was low, and from March to April, as the biomass increased sharply, the species diversity dropped to the minimum. During this time, C. groenlandicus was apparently dominant with the maximum biomass proportion up to 80%, while the U. prolifera proportion increased exponentially to 20% to 40%. The water temperature had a direct regulating effect on the biomass and the species succession of the attached green algae. The estimation of the community dynamics and the biomass of the green algae provided the evidence needed to track the origin of the large-scale green tide in the southern Yellow Sea.

The contribution of attached Ulva prolifera on Pyropia aquaculture rafts to green tides in the Yellow Sea

Green tides caused by the unusual accumulation of high floating Ulva prolifera have occurred regularly in the Yellow Sea since 2007.The primary source of the Yellow Sea green tides is the attached algae on the Pyropia aquaculture rafts in the Subei Shoal.Ulva prolifera and Blidingia(Italic)sp.are the main species observed on Pyropia aquaculture rafts in the Subei Shoal.We found that U.prolifera has strong buoyancy and a rapid growth rate,which may explain why it is the dominant species of green tides that occur in the China's sea area of the Yellow Sea.The growth rate of floating U.prolifera was about 20%–31%d–1,which was much higher than Blidingia(Italic)sp.There were about 1.7×104 t of attached algae on the Pyropia aquaculture rafts in May 2012.We found that 39%of attached algae could float when the tide rose in the Subei Shoal,and U.prolifera accounted for 63%of the floating algae.Our analysis estimated that about 4000 t of attached U.prolifera floated into the surrounding waters of the Subei Shoal during the recycling period of aquaculture rafts.These results suggest that the initial floating biomass of large-scale green tides in the Yellow Sea is determined by the U.prolifera biomass attached to Pyropia aquaculture rafts,further impacting the scale of the green tide。

Bionic Flexible Texture Design Based on Bio-Fouling Suppression Effect for Protection of Marine Structures

Marine equipments such as marine risers and oil pipelines operate in complex underwater environments and are usually attached by animals,plants and microorganisms.The attachment of marine fouling organisms will accelerate the corrosion damage of offshore structure and greatly reduce the service life.Studies have shown that non-smooth bionic surfaces with specific microstructures can inhibit fouling formation.Based on the idea of bionics,this paper proposes a new type of underwater flexible fretting texture,which is a composite material prepared by mixing graphene and silicone rubber,and modified by pulsed laser to construct a hexagonal bionic surface texture.Under the impact of specific water flow,the flexible texture can produce an angular displacement around 8°and a linear displacement in the amplitude range of 165μm,and the inhibition rate of fouling biological diatoms up to 97.5%,which can effectively avoid the occurrence of marine biological fouling.The results provide a new idea for the surface protection of marine structures,which is of great significance for the development of marine industry.

Effects of surface texturing on microalgal cell attachment to solid carriers

The objective of this study was to understand the role of surface texturing in microalgal cell attachment to solid surfaces.Two microalgal species,Scenedesmus dimorphus and Nannochloropsis oculata,were studied on solid carriers made of nylon and polycarbonate.Ridge,pillar and groove at micro-scale were engineered on the solid carriers.Cell response to the textured surfaces was separately described by the Cassie and Wenzel models and the contact point theory.Comparison between measured and model-predicted contact angles indicated that the wetting behavior of the textured solid carriers fell into the Wenzel state,which implied that algal cells could fully penetrate into the designed textures,but the adhesion behavior would be dependent on the size and shape of the cell.Experimental results showed that the attachment was preferred when the feature size was close to the diameter of the cell attempting to settle.Larger or smaller feature dimensions had the potential to reduce cellular attachment.The observation was found to qualitatively comply with the contact point theory.