Harmful algal blooms and eutrophication: "strategies" for nutrient uptake and growth outside the Redfield comfort zone

While many harmful algal blooms have been associated with increasing eutrophication, not all species respond similarly and the increasing challenge, especially for resource managers, is to determine which blooms are related to eutrophication and to understand why particular species proliferate under specific nutrient conditions. The overall goal of this brief review is to describe why nutrient loads are not changing in stoichiometric proportion to the "Redfield ratio", and why this has important consequences for algal growth. Many types of harmful algae appear to be able to thrive, and/or increase their production of toxins, when nutrient loads are not in proportion classically identified as Redfield ratios. Here we also describe some of the physiological mechanisms of different species to take up nutrients and to thrive under conditions of nutrient imbalance.

Effects of ambient DIN:DIP ratio on the nitrogen uptake of harmful dinoflagellate Prorocentrum minimum and Prorocentrum donghaiense in turbidistat

The effects of varying nitrogen (N): phosphorus (P) ratios on the growth and N-uptake and assimilation of the harmful dinoflagellates Prorocentrum minimum and Prorocentrum donghaiense were examined in turbidistat culture experiments. Algal cultures were supplied with media containing PO34? in various concentrations to obtain a wide range of N:P ratios. Experiments to determine rates of N uptake and assimilation of different N sources (NO3?, NH4+, urea and glycine by P. minimum and NO3?, NH4+ by P. donghaiense) were conducted using 15N tracer techniques at each N:P ratio. The growth rates suggested nutrient limitation at both high and low N:P ratios relative to the Redfield ratio. On a diel basis, the growth of both species was regulated by the light-dark cycle, which may be a result of regulation of both light- dependent growth and light-independent nutrient uptake. Maximum growth rates of both species always occurred at the beginning of light phase. In P-rich medium (low N:P ratio), both species had higher N assimilation rates, suggesting N limitation. Low assimilation coefficients at high N:P ratios suggested P limitation of N uptake and assimilation. NO3? and NH4+ contributed more than 90% of the total N uptake of P. minimum. Reduced N sources were more quickly assimilated than NO3?. Highest average daily growth rates were recorded near an N:P ratio of 12 for both species. The N uptake rates of cultures at N:P ratios near Redfield ratio were more balanced with growth rates. The linkage between growth rates and N uptake/assimilation rates were conceptually described by the variation of cell N quota. The N:P ratios affect the N uptake and growth of Prorocentrum spp., and may regulate their bloom progression in eutrophic ecosystems.

Seasonal variation of eddy kinetic energy in the South China Sea

Mesoscale eddy activity and its modulation mechanism in the South China Sea （SCS） are inves- tigated with newly reprocessed satellite altimetry observations and hydrographic data. The eddy kinetic energy （EKE） level of basin-wide averages show a distinct seasonal cycle with the maximum in August-December and the minimum in February-May. Furthermore, the seasonal pattern of EKE in the basin is dominated by region offshore of central Vietnam （OCV）, southwest of Taiwan Island （SWT）, and southwest of Luzon （SWL）, which are also the breeding grounds of mesoscale eddies in the SCS. Instability theory analysis suggests that the seasonal cycle of EKE is modulated by the baroclinic instability of the mean flow. High eddy growth rate （EGR） is found in the active eddy regions. Vertical velocity shear in the upper 50-500 m is crucial for the growth of baroclinic instability, leading to seasonal EKE evolution in the SCS.

Geographical distribution of red and green Noctiluca scintillans

The dinoflagellate Noctiluca scintillans is one of the most important and abundant red tide organisms and it is distributed world-wide. It occurs in two forms. Red Noctiluca is heterotrophic and fills the role of one of the microzooplankton grazers in the foodweb. In contrast, green Noctiluca contains a photosynthetic symbiont Pedinomonas noctilucae (a prasinophyte), but it also feeds on other plankton when the food supply is abundant. In this review, we document the global distribution of these two forms and include the first maps of their global distribution. Red Noctiluca occurs widely in the temperate to sub-tropical coastal regions of the world. It occurs over a wide temperature range of about 10°C to 25°C and at higher salinities (generally not in estuaries). It is particularly abundant in high productivity areas such as upwelling or eutrophic areas where diatoms dominate since they are its preferred food source. Green Noctiluca is much more restricted to a temperature range of 25°C-30°C and mainly occurs in tropical waters of Southeast Asia, Bay of Bengal (east coast of India), in the eastern, western and northern Arabian Sea, the Red Sea, and recently it has become very abundant in the Gulf of Oman. Red and green Noctiluca do overlap in their distribution in the eastern, northern and western Arabian Sea with a seasonal shift from green Noctiluca in the cooler winter convective mixing, higher productivity season, to red Noctiluca in the more oligotrophic warmer summer season.

Spatio-temporal variability of phytoplankton assemblages and its controlling factors in spring and summer in the Subei Shoal of Yellow Sea, China

The Subei Shoal is a special coastal area with complex physical oceanographic properties in the Yellow Sea.In the present study,the distribution of phytoplankton and its correlation with environmental factors were studied during spring and summer of 2012 in the Subei Shoal of the Yellow Sea.Phytoplankton species composition and abundance data were accomplished by Utermohl method.Diatoms represented the greatest cellular abundance during the study period.In spring,the phytoplankton cell abundance ranged from 1.59×10^3 to 269.78×10^3 cell/L with an average of 41.80×10^3 cell/L,and Skeletonema sp.and Paralia sulcata was the most dominant species.In summer,the average phytoplankton cell abundance was 72.59×10^3 cell/L with the range of 1.78×10^3 to 574.96×10^3 cell/L,and the main dominant species was Pseudo-nitzschia pungens,Skeletonema sp.,Dactyliosolen fragilissima and Chaetoceros curvisetus.The results of a redundancy analysis(RDA)showed that turbidity,temperature,salinity,pH,dissolved oxygen(DO),the ratio of dissolved inorganic nitrogen to silicate and SiO4-Si(DIN/SiO4-Si)were the most important environmental factors controlling phytoplankton assemblages in spring or summer in the Subei Shoal of the Yellow Sea.

Impacts of household income on beef at-home consumption:Evidence from urban China

Beef consumption in China has increased substantially from 5.0 million tons in 2000 to 7.7 million tons in 2019 thanks to rapid income growth,but still remains low compared to pork and poultry consumption.Improving the understanding about the impacts of household income on beef consumption in China is necessary to forecast future beef demand and inform the domestic beef industry,especially in the context of unprecedented expansion of middle income class in China.Based on survey data of 32878 urban households collected by the National Bureau of Statistics of China,we employed the inverse hyperbolic sine(IHS)double-hurdle model to estimate income elasticities of beef demand across different income groups and simulated possible trends of future beef consumption of Chinese urban residents.The empirical results showed that the unconditional income elasticities of beef consumption at home vary between 0.169 for the lowincome group and 0.671 for the high-income group.The simulated results indicated that beef consumption is expected to increase by 12.0 to 38.8%in 10 years and by 18.6 to 70.5%in 15 years under distinct income growth scenarios.Our findings provide practical insights for policy makers and other stakeholders about future beef demand,such as potential opportunities embedded in rising beef demand for domestic producers and world beef exporters as well as the urgency of improving the supply chain resilience of beef in China.

Role of Ekman Transport Versus Ekman Pumping in Driving Summer Upwelling in the South China Sea

Relative roles of Ekman transport and Ekman pumping in driving summer upwelling in the South China Sea(SCS) are examined using QuikSCAT scatterometer wind data.The major upwelling regions in the SCS are the coastal regions east and southeast of Vietnam(UESEV),east and southeast of Hainan Island(UESEH),and southeast of Guangdong province(USEG).It is shown that the Ekman transport due to alongshore winds and Ekman pumping due to offshore wind stress curl play different roles in the three upwelling systems.In UESEV,Ekman pumping and Ekman transport are equally important in generating upwelling.The Ekman transport increases linearly from 0.49 Sv in May to 1.23 Sv in August,while the Ekman pumping increases from 0.36 to 1.22 Sv during the same period.In UESEH,the mean estimates of Ekman transport and Ekman pumping are 0.14 and 0.07 Sv,respectively,indicating that 33% of the total wind-driven upwelling is due to Ekman pumping.In USEG,the mean Ekman transport is 0.041 Sv with the peak occurring in July,while Ekman pumping is much smaller(0.003 on average),indicating that the upwelling in this area is primarily driven by Ekman transport.In the summers of 2003 and 2007 following El Ni o-Southern Oscillation(ENSO) events,both Ekman transport and Ekman pumping decrease in UESEV due to the abnormally weak southwest monsoon.During the same events,however,Ekman transport is slightly enhanced and Ekman pumping is weakened in UESEH and USEG.

Distribution and controlling factors of phytoplankton assemblages associated with mariculture in an eutrophic enclosed bay in the East China Sea

The distribution of phytoplankton and its correlation with environmental factors were studied monthly during August 2012 to July 2013 in the Yantian Bay. A total of 147 taxa of phytoplankton were identified, and the average abundance was in the range of 0.57×10~4 to 7.73×10~4 cell/L. A total of 19 species dominated the phytoplankton assemblages, and several species that are widely reported to be responsible for microalgae blooms were the absolutely dominant species, such as Skeletonema costatum, Navicula sp., Thalassionema nitzschioides,Pleurosigma sp., and Licmophora abbreviata. The monthly variabilities in phytoplankton abundance could be explained by water temperature, dissolved oxygen, salinity, dissolved inorganic nitrogen（DIN）, and suspended solids. The results of a redundancy analysis showed that p H and nutrients, including DIN and silicate（SiO_4）, were the most important environmental factors controlling phytoplankton assemblages in specific months. It was found that nutrients and pH levels that were mainly influenced by mariculture played a vital role in influencing the variation of phytoplankton assemblages in the Yantian Bay. Thus, a reduction of mariculture activities would be an effective way to control microalgae blooms in an enclosed and intensively eutrophic bay.

Tides and Turbulent Mixing in the North of Taiwan Island

Microstructure and hydrological profiles were collected along two cross-shelf sections from the deep slope to the shallow water in the north of Taiwan Island in the summer of 2006. While the tidal currents on the shelf were dominated by the barotropic tide with the current ellipse stretched across the shelf, significant internal tides were observed on the slope. The depth-mean turbulent kinetic energy(TKE) dissipation rate on the shelf was 10^(-6)W kg-1, corresponding to a diapycnal diffusivity of 10^(-2)m^2s^(-1). The depth-mean TKE dissipation rate on the slope was 1 × 10^(-7)W kg-1, with diapycnal diffusivity of 3.4 × 10^(-4)m^2s^(-1). The shear instability associated with internal tides largely contributed to the TKE dissipation rate on the slope from the surface to 150 m, while the enhanced turbulence on the shelf was dominated by tidal or residual current dissipations caused by friction in the thick bottom boundary layer(BBL). In the BBL, the Ekman currents associated with the northeastward Taiwan Warm Current were identified, showing a near-bottom velocity spiral, which agreed well with the analytical bottom Ekman solution.

Effect of Nitrogen Source on Biomass and Lipid Production of a Marine Microalga, <i>Nannochloropsis oceanica</i>IMET1

The effects of the nitrogen sources sodium nitrate (NaNO3) and urea (CH4N2O) on growth, lipid production, and fatty acid composition of Nannochloropsis oceanica IMET1 were investigated. Nitrogen source affected cell density, dry cell weight, and lipid production. Cells grown in the nitrate medium increased dry cell weight and lipid weight in comparison with cells grown in the urea medium. The composition of fatty acids varied with nitrogen sources. IMET1cultured in the nitrate medium mainly contained C18:2 (14.9%) and C16:0 (6.3%) fatty acids, while IMET1 in the urea medium mainly contained C22:0 (33.1%), C18:3 (8.6%), and C16:0 (6.8%). This study demonstrates that nitrogen source can strongly influence lipid production and composition of N. oceanica IMET1.

Nutrients Extracted from Chicken Manure Accelerate Growth of Microalga <i>Scenedesmus obliquus</i>HTB1

Sustainable development using wastes as resources is a new paradigm. Chicken manure contains rich amounts of nitrogen and phosphorus and has been used as crop fertilizer. However, little is known about whether nutrients of chicken manure are suitable and efficient to support the rapid growth of microalgae. In this study, we explore the possibility of using nutrient extracted from chicken manure to grow microalgae. We used an algal strain Scenedesmus sp. HTB1, which is an oleaginous species with high CO2 tolerance capability. The growth performance of HTB1 on various media amended with nutrient extracted from three different chicken manure sources was monitored and compared to the growth rate of HTB1 grown in the standard medium BG11. Meanwhile, the changes of total nitrogen (N) and phosphorus (P), both organic and inorganic, were measured during the growth period. Culture media enriched with the nutrient extracted from two chicken manure sources outperformed the standard culture medium BG11 in terms of algal biomass production. When cultivated with manure nutrient, HTB1 utilized inorganic N efficiently, but consumed very little organic N during the experimental growth period. However, HTB1 was able to utilize both organic and inorganic phosphorus. We demonstrate that nutrient extracted from chicken manure support rapid growth and high biomass yield in microalgae?Scenedesmus obliquus?HTB1. Therefore chicken manure holds great promise to be used as a cost-effective and efficient fertilizer for large-scale production of microalgae.

Swine waste as a source of natural products: A carotenoid antioxidant

Development of Environmentally Superior Technologies swine waste management has focused on extraction of products with relatively low unit values. Analyses of the bacterial composition of swine waste lagoon samples confirmed the presence of several purple non-sulfur bacteria (PNSB) species known to produce a variety of carotenoids. We examined a carotenoid naturally abundant in North Carolina swine waste lagoons dominated by PNSB. Analytical methods including high performance liquid chromatography (HPLC), mass spectrometry, and nuclear magnetic resonance (NMR) confirmed the identity of the dominant carotenoid as spirilloxanthin, C42H60O2, with 13 conjugated double bonds. This structure confers antioxidant properties as good as those of carotenoids currently marketed as antioxidants. Visual estimates of the “redness” of swine waste lagoon liquids were highly correlated with carotenoid content. Spirilloxanthin concentrations in a lagoon with a strong PNSB bloom were approximately 0.5 grams·m-3. These results support further investigations into the potential for extracting commercially valuable natural products from swine waste lagoons.

Water Use in Sugar and Ethanol Industry in the State of Sao Paulo(Southeast Brazil)

Brazil is the largest producer of ethanol from sugarcane in the world. While the ethanol industry is economically important to Brazil for several reasons, it also has a significant impact on the environment. Here we analyze the water consumptive use in the transformation of the feedstock (sugarcane) into ethanol and the impact of industrial byproduct effluents on water resources of the state of Sao Paulo, Brazil. Our estimates indicated that in the 2007-2008 harvest, 700 million m3 was withdrawn mainly from rivers and streams by 140 mills, and of this total 440 million m3 was consumed which yielded a water use of approximately 1.53 m3 ·water·tonˉ1 sugarcane or approximately 18 L·water·L-ˉ1 ethanol. At the same time, a total of 120 million m3 of vinasse by-product was produced in the state, equivalent to an organic load of approximately 3 billion kg·BOD during the harvest season or approximately 8 million kg·BOD·dˉ1. Although the water used by sugarcane mills has decreased in recent decades, it is still possible to further decrease the amount of water used by ethanol production. This would decrease the pressure on 1st order streams of the state from which most water is withdrawn. In addition, the enormous volume of vinasse production must be reduced because it exerts constant pressure on aquatic ecosystems, soil and groundwater due to the constant increase in the potassium (K) concentration in areas where it is used as a fertilizer.

基于数值模拟与统计学方法的南黄海近岸沙脊与水道稳定性评价

以南黄海江苏岸外辐射沙脊群为对象,基于已验证的该区域沉积动力学数值模型模拟近30 a（1979-2011年）的水下地形演化,计算辐射沙脊区域海底地形年际变化标准偏差,对沙脊和水道的地貌稳定性进行定量评估。研究发现,地形变化标准偏差愈小,地貌愈稳定;标准偏差愈高,地貌愈不稳定。定量地确定了南黄海辐射沙脊区域内沙脊与水道稳定性系数的时空分布,发现主要淤积区域位于沙脊周围,近岸沙洲有淤高的趋势;主要侵蚀区位于水道,沙脊间水道逐渐冲刷加深,如西洋水道和黄沙洋水道。本研究提出的基于海底地形年际变化标准偏差确定地貌稳定性评估方法,可为海岸陆架地貌稳定性研究、区域资源开发和环境保护等提供参考。

Preface to the special issue on eutrophication and HABs: the GEOHAB approach

Harmful algal blooms (HABs), those proliferations of algae that can contaminate seafood with toxins, cause fish or shellfish kills, or alter ecosystems in detrimental ways, have been increasing in global geographic extent, in the frequency and duration of occurrence and in their ecological,

Genomic characterization and molecular dating of the novel bacterium Permianibacter aggregans HW001T,which originated from Permian ground water

The Permian Basin is a unique ecosystem located in the southwest of the USA.An unanswered question is whether the bacteria in the Permian Basin adapted to the changing paleomarine environment and survived in the remnants of Permian groundwater.In our previous study,a novel bacterial strain,Permianibacter aggregans HW001T,was isolated from micro-algae cultures incubated with Permian Basin waters,and was shown to originate from the Permian Ocean.In this study,strain HW001T was shown to be the representative strain of a novel family,classified as‘Permianibacteraceae’.The results of molecular dating suggested that the strain HW001T diverged~447 million years ago(mya),which is the early Permian period(~250 mya).Genome analysis was used to access its potential energy utilization and biosynthesis capacity.A large number of transporters,carbohydrate-active enzymes and protein-degradation related genes have been annotated in the genome of strain HW001T.In addition,a series of important metabolic pathways,such as peptidoglycan biosynthesis,osmotic stress response system and multifunctional quorum sensing were annotated,which may confer the ability to adapt to vari-ous unfavorable environmental conditions.Finally,the evolutionary history of strain HW001T was reconstructed and the horizontal transfer of genes was predicted,indicating that the adaptation of P.aggregans to a changing marine environment depends on the evolution of their metabolic capabilities,especially in signal transmission.In conclusion,the results of this study provide genomic information for revealing the adaptive mechanism of strain HW001T to the changing ancient oceans.

Producing Designer Oils in Industrial Microalgae by Rational Modulation of Co-evolving Type-2 Diacylglycerol Acyltransferases

Microalgal oils, depending on their degree of unsaturation, can be utilized as either nutritional supplements or fuels; thus, a feedstock with genetically designed and tunable degree of unsaturation is desirable to maximize process efficiency and product versatility. Systematic profiling of ex vivo （in yeast）, in vitro, and in vivo activities of type-2 diacylglycerol acyltransferases in Nannochloropsis oceanica （NoDGAT2s or NoDGTTs）, via reverse genetics, revealed that NoDGAT2A prefers saturated fatty acids （SFAs）, NoDGAT2D prefers monounsaturated fatty acids （MUFAs）, and NoDGAT2C exhibits the strongest activity toward polyunsaturated fatty acids （PUFAs）. As NoDGAT2A, 2C, and 2D originated from the green alga, red alga, and eukaryotic host ancestral participants of secondary endosymbiosis, respectively, a mecha- nistic model of oleaginousness was unveiled, in which the indigenous and adopted NoDGAT2s formulated functional complementarity and specific transcript abundance ratio that underlie a rigid SFA：MUFA：PUFA hierarchy in triacylglycerol （TAG）. By rationally modulating the ratio of NoDGAT2A＇：2C^D transcripts, a bank of N. oceanica strains optimized for nutritional supplement or fuel production with a wide range of degree of unsaturation were created, in which proportion of SFAs, MUFAs, and PUFAs in TAG varied by 1.3-, 3.7-, and 11.2-fold, respectively. This established a novel strategy to simultaneously improve productivity and quality of oils from industrial microalgae.

Metabolic tuning of a stable microbial community in the surface oligotrophic Indian Ocean revealed by integrated meta-omics

Understanding the mechanisms,structuring microbial communities in oligotrophic ocean surface waters remains a major ecological endeavor.Functional redundancy and metabolic tuning are two mechanisms that have been proposed to shape microbial response to environmental forcing.However,little is known about their roles in the oligotrophic surface ocean due to less integrative characterization of community taxonomy and function.Here,we applied an integrated meta-omics-based approach,from genes to proteins,to investigate the microbial community of the oligotrophic northern Indian Ocean.Insignificant spatial variabilities of both genomic and proteomic compositions indicated a stable microbial community that was dominated by Prochlorococcus,Synechococcus,and SAR11.However,fine tuning of some metabolic functions that are mainly driven by salinity and temperature was observed.Intriguingly,a tuning divergence occurred between metabolic potential and activity in response to different environmental perturbations.Our results indicate that metabolic tuning is an important mechanism for sustaining the stability of microbial communities in oligotrophic oceans.In addition,integrated meta-omics provides a powerful tool to comprehensively understand microbial behavior and function in the ocean.

Resilience indicators support valuation of estuarine ecosystem restoration under climate change

Economic valuation of ecological restoration most often encompasses only the most tangible ecosystem service benefits,thereby omitting many difficult-to measure benefits,including those derived from enhanced reliability of ecosystem services.Because climate change is likely to impose novel ecosystem stressors,a typical approach to valuing benefits may fail to capture the contribution of ecosystem resilience to sustaining long-term benefits.Unfortunately,we generally lack predictive probabilistic models that would enable measurement and valuation of resilience.Therefore,alternative measures are needed to complement monetary values and broaden understanding of restoration benefits.We use a case study of Chesapeake Bay restoration(total maximum daily load)to show that ecosystem service benefits that are typically monetized leave critical information gaps.To address these gaps,we review evidence for ecosystem services that can be quantified or described,including changes in harmful algal bloom risks.We further propose two integrative indicators of estuarine resilience-the extent of submerged aquatic vegetation and spatial distribution of fish.Submerged aquatic vegetation extent is indicative of qualities of ecosystems that promote positive feedbacks to water quality.Broadly distributed fish populations reduce risk by promoting diverse responses to spatially heterogeneous stresses.Our synthesis and new analyses for the Chesapeake Bay suggest that resilience metrics improve understanding of restoration benefits by demonstrating how nutrient and sediment load reductions will alleviate multiple sources of stress,thereby enhancing the system’s capacity to absorb or adapt to extreme events or novel stresses.

Twenty-first century climate change and submerged aquatic vegetation in a temperate estuary:the case of Chesapeake Bay

Introduction:The Chesapeake Bay was once renowned for expansive meadows of submerged aquatic vegetation(SAV).However,only 10%of the original meadows survive.Future restoration effortswill be complicated by accelerating climate change,including physiological stressors such as a predicted mean temperature increase of 2-6℃and a 50-160%increase in CO_(2)concentrations.Outcomes:As the Chesapeake Bay begins to exhibit characteristics of a subtropical estuary,summer heat waves will become more frequent and severe.Warming alone would eventually eliminate eelgrass(Zostera marina)from the region.It will favor native heat-tolerant species such as widgeon grass(Ruppia maritima)while facilitating colonization by non-native seagrasses(e.g.,Halodule spp.).Intensifying human activity will also fuel coastal zone acidification and the resulting high CO_(2)/low pH conditions may benefit SAV via a“CO_(2)fertilization effect.”Discussion:Acidification is known to offset the effects of thermal stress and may have similar effects in estuaries,assuming water clarity is sufficient to support CO_(2)-stimulated photosynthesis and plants are not overgrown by epiphytes.However,coastal zone acidification is variable,driven mostly by local biological processes that may or may not always counterbalance the effects of regional warming.This precarious equipoise between two forces-thermal stress and acidification-will be critically important because it may ultimately determine the fate of cool-water plants such as Zostera marina in the Chesapeake Bay.Conclusion:The combined impacts of warming,coastal zone acidification,water clarity,and overgrowth of competing algae will determine the fate of SAV communities in rapidly changing temperate estuaries.