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• We first report regime shifts in phytoplankton RUE along TSI gradient across space and time. • Tipping point values of TSI were lower in subtropical than temperate waterbodies. • Regime shifts regulated trophic transfer efficiency from phytoplankton to zooplankton. • Nitrogen-fixing filamentous cyanobacteria can drive eutrophication under mesotrophic state. • Early management practices for algal bloom prevention and control were latitude-dependent. Eutrophication and harmful algal blooms have severe effects on water quality and biodiversity in lakes and reservoirs. Ecological regime shifts of phytoplankton blooms are generally thought to be driven by the rapidly rising nutrient use efficiency of bloom-forming species over short periods, and often exhibit nonlinear dynamics. Regime shifts of trophic state, eutrophication, stratification, and clear or turbid waters are well-studied topics in aquatic ecology. However, information on the prevalence of regime shifts in relationships between trophic states and phytoplankton resource transfer efficiencies in ecosystems is still lacking. Here, we provided a first insight into regime shifts in nitrogen use efficiency of phytoplankton along the trophic state gradient. We explored the regime shifts of phytoplankton resource use efficiency and detected the tipping points by combining four temporal or spatial datasets from tropical to temperate zones in Asia and Europe. We first observed significant abrupt transitions (abruptness > 1) in phytoplankton nitrogen use efficiency along the trophic state gradient. The tipping point values were lower in subtropical/tropical waterbodies (mesotrophic states; TSIc: around 50) than those in temperate zones (eutrophic states; TSIc: 60–70). The regime shifts significantly reduced the primary production transfer efficiency via zooplankton (from 0.15 ± 0.03 to 0.03 ± 0.01; mean ± standard error) in the aquatic food web. Nitrogen-fixing filamentous cyanobacteria can drive eutrophication under mesotrophic state. Our findings imply that the time-window of opportunity for harmful algae prevention and control in lakes and reservoirs is earlier in subtropical/tropical regions. Conceptual scheme showing the trophic state index-dependent trend of nitrogen use efficiency of phytoplankton in the subtropical (red) and temperate (blue) zones. Tipping points were lower in the subtropical zones. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract Resource use efficiency in Asian carp farming systems is analysed based on a survey of 2493 farms of nine countries. Multivariate classification of farms by intensity and diversity identified six farm types: four types of specialized aquaculture farms at different levels of intensity, and two types of integrated agriculture–aquaculture systems. Pond-based, specialized semi-extensive systems (using mainly inorganic fertilizers and feeds of off-farm origin), and integrated semi-intensive systems (using feeds and fertilizer of both on and off-farm origin) are by far the most common types, accounting for 59% and 27% of all farms respectively. Specialized semi-extensive systems also show the highest protein and nutrient (N and P) use efficiencies, and among the highest labour use efficiency. Super-intensive cage farms are less efficient in nutrient and labour use, but provide very high returns to land and capital investment. On average, the aquaculture components of integrated agriculture– aquaculture systems are less nutrient, land, and labour efficient than specialized semi-extensive systems. Integrated semi-extensive systems (using organic fertilizers of on-farm origin) are particularly inefficient across all indicators. Hence in practice, gains in overall resource use efficiency through on-farm integration with agricultural production are constrained by the relative inefficiency of the aquaculture subsystems on integrated farms. Although such systems can likely be improved, integration as such is not a panacea to increasing resource use efficiency. Wide variation in resource use efficiency within all systems indicates potential for substantial efficiency gains through improved management regardless of the fundamental choice of system. [ABSTRACT FROM AUTHOR]

Abstract: In Asia, as elsewhere in the world, countries rushed to promote biofuels during the dramatic oil price increases of 2007–2008 as way to enhance energy security, without waiting for the settlement of controversial debates about the environmental effects of biofuels, especially their effects on greenhouse gas emissions, deforestation, biodiversity, and whether biofuels cause a conflict between food and fuel. This paper does not settle this debate, but instead argues that there are straightforward, practical and feasible measures that can be implemented immediately in order to reduce the pressure of biofuels on the environment and food supply, and more generally increase food production. The key is to focus on increasing resource use efficiency in agriculture, especially different forms of energy use. Resource use efficiency in agriculture is low in many parts of Asia. Concrete measures that could be taken include reductions in market-distorting input subsidies and the introduction of resource-conserving technologies. These could be supplemented with greater use of non-fossil fuels in agricultural production, use of agricultural wastes in energy production, inclusion of input use levels in biofuel certification systems, and greater investment in agricultural research, extension systems, and infrastructure development. Biofuel fever has waned since the onset of the global financial crisis in late 2008, but it is likely to return when economic conditions eventually improve, and possible moves to strengthen the European Union biofuel blending requirements could further accelerate it. Much of the debate on biofuel-related impacts in the region has focused on deforestation, with little attention on agricultural input use, which could also have serious consequences for greenhouse gas (GHG) emissions. In sum, this paper argues that governments can still improve the environmental performance of biofuels while reducing potential conflicts with food security by implementing the straightforward measures suggested here. Though these may appear to be basic textbook suggestions, many governments are still not following them even though the spread of biofuels increases their importance and urgency. The message is that the governments in the region should get back to the basics. [Copyright &y& Elsevier]