Nutrient Structure of the Taiwan Warm Current and Estimation of Vertical Nutrient Fluxes in Upwelling Areas in the East China Sea in Summer

Based on field data for nutrients collected on the continental shelf of the East China Sea(ECS) during summer 2006, the structure and variations of nutrients in every water mass related to the Taiwan Warm Current(TWC) were analyzed. The supplementary effect of nutrient of upwelling on harmful algal blooms(HABs) in the ECS was also estimated, based on upwelling data. Then the maintenance contribution of nutrient of upwelling to HABs was assessed. The results showed that N/P ratio is fairly low in both surface and deep layers of the TWC, which possibly controls nutrient structure of the HABs-frequently-occuring areas. In upwelling areas, the rate of phosphate(PO4-P) uptake exceeds that of nitrate(NO3-N) of the TWC. The TWC may relieve PO4-P limitation during the process of HABs. Furthermore, upwelling plays an important role in providing nutrients to HABs. After estimating nutrient fluxes(NO3-N, PO4-P, Si O3-Si) in the upwelling areas along a typical section(S07), the results showed that the nutrient uptake rate is the greatest at 10-20 m below euphotic zone, sustaining the ongoing presence of HABs. The uptake rate of PO4-P is the highest among dissolved inorganic nutrients. Therefore, upwelling is most likely the main source of PO4-P supply to HABs.

Using vibrational infrared biomolecular spectroscopy to detect heat-induced changes of molecular structure in relation to nutrient availability of prairie whole oat grains on a molecular basis

Background： To our knowledge, there is little study on the interaction between nutrient availability and molecular structure changes induced by different processing methods in dairy cattle. The objective of this study was to investigate the effect of heat processing methods on interaction between nutrient availability and molecular structure in terms of functional groups that are related to protein and starch inherent structure of oat grains with two continued years and three replication of each year.Method： The oat grains were kept as raw（control） or heated in an air-draft oven（dry roasting： DO） at 120 °C for 60 min and under microwave irradiation（MIO） for 6 min. The molecular structure features were revealed by vibrational infrared molecular spectroscopy.Results： The results showed that rumen degradability of dry matter, protein and starch was significantly lower（P 〈0.05） for MIO compared to control and DO treatments. A higher protein α-helix to β-sheet and a lower amide I to starch area ratio were observed for MIO compared to DO and/or raw treatment. A negative correlation（-0.99, P 〈 0.01）was observed between α-helix or amide I to starch area ratio and dry matter. A positive correlation（0.99, P 〈 0.01） was found between protein β-sheet and crude protein.Conclusion： The results reveal that oat grains are more sensitive to microwave irradiation than dry heating in terms of protein and starch molecular profile and nutrient availability in ruminants.

Long-term nutrient variation trends and their potential impact on phytoplankton in the southern Yellow Sea,China

The concentration and composition of nutrients,such as N,P,and Si,respond to biogeochemical processes and in turn,impact the phytoplanktons'community structure and primary production.In this study,historical data was systematically analyzed to identify long-term variations in nutrient trends,red tide frequency,phytoplankton community abundance,and dominant species succession in the southern Yellow Sea(SYS).Results showed that N/P concentration ratios dramatically increased as a function of increasing dissolved inorganic nitrogen concentrations,and Si/N concentration ratios were generally larger than 1,indicating that N limitation morphed to P limitation and potentially to Si limitation,which impacted the phytoplankton community.Furthermore,inter-annual trends over the past 50 years show that phytoplankton community abundance has been higher in spring and summer,relative to autumn and winter.Moreover,with respect to red tide frequency,diatom abundance gradually decreased,while that of dinoflagellates gradually increased.Dominant species succession showed that the phytoplankton community exhibited an evident tendency to transform from diatoms to dinoflagellates.These research results clearly depict the presence of an important correlation between the phytoplankton community and nutrient structure in the SYS.

Causes and Consequences of Changes in Nutrient Structure in the Jiaozhou Bay

: Concentrations and ratios of nutrients in Jiaozhou Bay, China, have changed much in the past decades, with trends indicating an increase in nitrogen and a decrease in silicate. Statistical analysis has shown that the long-term variations of nutrients are associated with agricultural activities, precipitation, and anthropogenic factors. Stoichiometric calculations indicate that the nutrient structure has become more and more unbalanced. There has been almost no possibility for nitrogen limitation since the 1980s, the probability of P limitation has increased, and the probability of Si limitation has also increased markedly from the 1980s to the 1990s. As a consequence of changes in nutrient structure, a decrease in the abundance of net phytoplankton was evident, whereas total chlorophyll a, levels have remained roughly unchanged at around 3.55 g/L. Thus, it is likely that smaller species have taken the niche vacated by the larger species. Changes in phytoplankton size and species composition may ultimately lead to various functional and structural changes at the system level.

Spatial variations of macrozoobenthos and sediment nutrients in Lake Yangcheng: Emphasis on effect of pen culture of Chinese mitten crab

We determined the effect of Chinese mitten crab（CMC） pen culture on the quantified spatial distribution of the macrozoobenthic community and sediment nutrients in Lake Yangcheng.Redundancy analysis indicated that water temperature, macrophyte occurrence, sediment type, and crab culture were the main environmental factors that influence the spatiotemporal macrozoobenthic distribution. Macrozoobenthic assemblages in the lake were characterized by eutrophic indicator species. In the most polluted estuaries, the abundance and diversity indices of the whole community and abundance of chironomids and oligochaetes were significantly depressed, and sediment carbon（C） and phosphorus（P） were significantly enhanced compared with those in the western, middle（MB）, and eastern basin（EB）. Crab culture in this lake had significant effects on the species composition of the macrozoobenthic community in one of three CMC culture pens（CP）, and generally depressed the abundance of most chironomid and oligochaete species. Significantly increased diversity, evenness, sediment carbon and nitrogen content, and sediment C：P ratio in the CP were found compared with those in the three basins.However, no conspicuous difference in sediment P content between the CP and the two basins of MB and EB was detected. Our results showed that the enhanced diversity and evenness of macrozoobenthos might be associated with the joint effect of macrophyte planting and crab predation, and macrophyte planting may modify the effects of CMC culture by leading to disproportional accumulation of C and N in the sediment relative to P in the CP of the lake.

A comparative study on the alternating mesophilic and thermophilic two-stage anaerobic digestion of food waste

An alternating mesophilic and thermophilic two stage anaerobic digestion （AD） process was conducted. The temperature of the acidogenic （A） and methanogenic （M） reactors was controlled as follows： System 1 （S1） mesophilic A-mesophilic M; （S2） mesophilic A-thermophilic M; and （S3） thermophilic A-mesophilic M. Initially, the AD reactor was acclimatized and inoculated with digester sludge. Food waste was added with the soluble chemical oxygen demand （SCOD） concentrations of 41.4-47.0 g/L and volatile fatty acids of 2.0-3.2 g/L. Based on the results, the highest total chemical oxygen demand removal （86.6%） was recorded in S2 while S3 exhibited the highest SCOD removal （96.6%）. Comparing S1 with S2, total solids removal increased by 0.5%;S3 on the other hand decreased by 0.1% as compared to S1. However, volatile solids （VS） removal in S1, S2, and S3 was 78.5%, 81.7%, and 79.2%, respectively. S2 also exhibited the highest CH4 content, yield, and production rate of 70.7%, 0.44 L CH4/g VSadded, and 1.23 L CH4/（L.day）, respectively. Bacterial community structure revealed that the richness, diversity, evenness, and dominance of S2 were high except for the archaeal community. The terminal restriction fragments dendrogram also revealed that the microbial community of the acidogenic and methanogenic reactors in S2 was distinct. Therefore, S2 was the best among the systems for the operation of two-stage AD of food waste in terms of CH4 production, nutrient removal, and microbial community structure.

How silicon fertilizer improves nitrogen and phosphorus nutrient availability in paddy soil?

In order to reveal the mechanism of silicon(Si)fertilizer in improving nitrogen(N)and phosphorus(P)nutrient availability in paddy soil,we designed a series of soil culture experiments by combining application of varying Si fertilizer concentrations with fixed N and P fertilizer concentrations.Following the recommendations of fertilizer manufacturers and local farmers,we applied Si in concentrations of 0,5.2,10.4,15.6,and 20.8μg/kg.At each concentration of added Si,the availability of soil N and P nutrients,soil microbial activity,numbers of ammonia-oxidizing bacteria and P-decomposing bacteria which means that the organic P is decomposed into inorganic nutrients which can be absorbed and utilized by plants,and urease and phosphatase activity first increased,and then decreased,as Si was added to the soil.These indicators reached their highest levels with a Si application rate of 15.6μg/kg,showing values respectively 19.78%,105.09%,8.34%,73.12%,130.36%,28.12%,and 20.15%higher than those of the controls.Appropriate Si application(10.4 to 15.6µg/kg)could significantly increase the richness of the soil microbial community involved in cycling of N and P nutrients in the soil.When the Si application rate was 15.6μg/kg,parameters for characterizing microbial abundance such as sequence numbers,operational taxonomic unit(OTU)number,and correlation indices of microbial community richness such as Chao1 index,the adaptive coherence estimator(ACE)index,Shannon index,and Simpson index all reached maximum values,with amounts increased by 14.46%,10.01%,23.80%,30.54%,0.18%,and 2.64%,respectively,compared with the control group.There is also a good correlation between N and P mineralization and addition of Si fertilizer.The correlation coefficients between the ratio of available P/total P(AP/TP)and the number of ammonia-oxidizing bacteria,AP/TP and acid phosphatase activity(AcPA),AP/TP and the Shannon index,the ratio of available N/total amount of N(AN/TN)and the number of ammoniated bacteria,and AN/TN and AcPA were 0.9290,0.9508,0.9202,0.9140,and 0.9366,respectively.In summary,these results revealed that enhancement of soil microbial community structure diversity and soil microbial activity by appropriate application of Si is the key ecological mechanism by which application of Si fertilizer improves N and P nutrient availability.