Xi Xiao

Bio: Xi Xiao is an academic researcher from Zhejiang University. The author has contributed to research in topics: Microcystis aeruginosa & Algal bloom. The author has an hindex of 17, co-authored 42 publications receiving 1083 citations. Previous affiliations of Xi Xiao include University of Oslo & University of Southern Denmark.

Can seaweed farming play a role in climate change mitigation and adaptation

Abstract: Seaweed aquaculture, the fastest-growing component of global food production, offers a slate of opportunities to mitigate and adapt to climate change. Seaweed farms release carbon that maybe buried in sediments or exported to the deep sea, therefore acting as a CO2 sink. The crop can also be used, in total or in part, for biofuel production, with a potential CO2 mitigation capacity, in terms of avoided emissions from fossil fuels, of about 1500 tons CO2 km-2 year-1. Seaweed aquaculture can also help reduce the emissions from agriculture, by improving soil quality substituting synthetic fertilizer and, when included in cattle fed, lowering methane emissions from cattle. Seaweed aquaculture contributes to climate change adaptation by damping wave energy and protecting shorelines, and by elevating pH and supplying oxygen to the waters, thereby locally reducing the effects of ocean acidification and de-oxygenation. The scope to expand seaweed aquaculture is, however, limited by the availability of suitable areas and competition for suitable areas with other uses, engineering systems capable of coping with rough conditions offshore and an increasing market demand for seaweed products, among other factors. Despite these limitations, seaweed farming practices can be optimized to maximize climate benefits, which may, if economically compensated, improve the income of seaweed farmers.

Nutrient removal from Chinese coastal waters by large-scale seaweed aquaculture

Abstract: China is facing intense coastal eutrophication. Large-scale seaweed aquaculture in China is popular, now accounting for over 2/3’s of global production. Here, we estimate the nutrient removal capability of large-scale Chinese seaweed farms to determine its significance in mitigating eutrophication. We combined estimates of yield and nutrient concentration of Chinese seaweed aquaculture to quantify that one hectare of seaweed aquaculture removes the equivalent nutrient inputs entering 17.8 ha for nitrogen and 126.7 ha for phosphorus of Chinese coastal waters, respectively. Chinese seaweed aquaculture annually removes approximately 75,000 t nitrogen and 9,500 t phosphorus. Whereas removal of the total N inputs to Chinese coastal waters requires a seaweed farming area 17 times larger than the extant area, one and a half times more of the seaweed area would be able to remove close to 100% of the P inputs. With the current growth rate of seaweed aquaculture, we project this industry will remove 100% of the current phosphorus inputs to Chinese coastal waters by 2026. Hence, seaweed aquaculture already plays a hitherto unrealized role in mitigating coastal eutrophication, a role that may be greatly expanded with future growth of seaweed aquaculture.

Optimization of FDA–PI method using flow cytometry to measure metabolic activity of the cyanobacteria, Microcystis aeruginosa

Abstract: A rapid toxicity test based on inhibition of esterase activity in the harmful freshwater microalgae – Microcystis aeruginosa was developed using flow cytometry. The hydrolysis rate of fluorescein diacetate (FDA) by intracellular esterase to fluorescein was used to indicate the metabolic activity of algae. Uptake of FDA was optimized at different concentrations and incubation times. Propidium iodide (PI) was utilized to assess cell membrane integrity. The optimized FDA/PI staining dosages were 10 mg/L and 10 μM, respectively, lower than the reported concentrations. Correspondingly, the proper incubation time was 14–21 min at the optimal FDA dosage determined in this study. A new procedure based on optimized FDA/PI condition, called “whole algal culture flow cytometry with fluorescence triggering”, was developed for short-term bioassays. This new procedure, taking account of working conditions such as pH and impure cultures, is able to avoid algal cell damages in sample preparation and separate algal cells from non-algal particles by fluorescence triggering. This newly-developed procedure was then used to assess the toxicity of copper on M. aeruginosa in a short-term exposure (36 h). As copper concentrations increased, it was found that the esterase activity decreased in a concentration-dependent manner with increased membrane fragments. Moreover, esterase activity was a good indicator of copper toxicity in M. aeruginosa . The EC 50 value based on mean fluorescence intensity (MFI) was 123.3 μg/L (95% confidence limits 101.5–146.2 μg/L). Therefore, the new-developed procedure could be used for sublethal endpoints detection, and has the potential to be a rapid and cost-effective bioassay for selecting M. aeruginosa control methods or exploring the M. aeruginosa activity inhibition mechanism.

A 20-year retrospective review of global aquaculture.

Abstract: The sustainability of aquaculture has been debated intensely since 2000, when a review on the net contribution of aquaculture to world fish supplies was published in Nature. This paper reviews the developments in global aquaculture from 1997 to 2017, incorporating all industry sub-sectors and highlighting the integration of aquaculture in the global food system. Inland aquaculture—especially in Asia—has contributed the most to global production volumes and food security. Major gains have also occurred in aquaculture feed efficiency and fish nutrition, lowering the fish-in–fish-out ratio for all fed species, although the dependence on marine ingredients persists and reliance on terrestrial ingredients has increased. The culture of both molluscs and seaweed is increasingly recognized for its ecosystem services; however, the quantification, valuation, and market development of these services remain rare. The potential for molluscs and seaweed to support global nutritional security is underexploited. Management of pathogens, parasites, and pests remains a sustainability challenge industry-wide, and the effects of climate change on aquaculture remain uncertain and difficult to validate. Pressure on the aquaculture industry to embrace comprehensive sustainability measures during this 20-year period have improved the governance, technology, siting, and management in many cases. The volume of global aquaculture production has tripled since 2000 with positive trends in environmental performance, but the sector faces mounting challenges including pathogen management, pollution, climate change, and increasing dependence on land-based resource systems.

Seaweed production: overview of the global state of exploitation, farming and emerging research activity

Abstract: The use of seaweeds has a long history, as does the cultivation of a select and relatively small group of species. This review presents several aspects of seaweed production, such as an update on t...

Rebuilding marine life

Abstract: Sustainable Development Goal 14 of the United Nations aims to "conserve and sustainably use the oceans, seas and marine resources for sustainable development". Achieving this goal will require rebuilding the marine life-support systems that deliver the many benefits that society receives from a healthy ocean. Here we document the recovery of marine populations, habitats and ecosystems following past conservation interventions. Recovery rates across studies suggest that substantial recovery of the abundance, structure and function of marine life could be achieved by 2050, if major pressures-including climate change-are mitigated. Rebuilding marine life represents a doable Grand Challenge for humanity, an ethical obligation and a smart economic objective to achieve a sustainable future.