Biochemical compositions of two dominant bloom- forming species isolated from the Yangtze River Estuary in response to different nutrient conditions

Variations of cellular total lipid, total carbohydrate and total protein content of two dominant bloom-forming species (Skeletonema costatum and Prorocentrum donghaiense) isolated from the Yangtze River Estuary were examined under six different nutrient conditions in batch cultures. Daily samples were collected to estimate the cell growth, nutrient concentration and three biochemical compositions content during 7 days for S. costatum and the same sampling procedure was done every other day during 10 days for P. donghaiense. Results showed that for S. costatum, cellular total lipid content increased under phosphorus (P) limitation, but not for nitrogen (N) limitation; cellular carbohydrate were accumulated under both N and P limitation: cellular total protein content of low nutrient concentration treatments were significantly lower than that of high nutrient concentration treatments. For P. donghaiense, both cellular total lipid content and total carbohydrate content were greatly elevated as a result of N and P exhaustion, but cellular total protein content had no significant changes under nutrient limitation. In addition, the capability of accumulation of three biochemical constituents of P. donghaiense was much stronger than that of S. costatum. Pearson correlation showed that for both species, the biochemical composition of three constituents (lipid, carbohydrate and protein) had no significant relationship with extracellular N concentration, but had positive correlation with extracellular and intracellular P concentration. The capability of two species to accumulate cellular total lipid and carbohydrate under nutrient limitation may help them accommodate the fluctuating nutrient condition of the Yangtze River Estuary. The different responses of two species of cellular biochemical compositions content under different nutrient conditions may provide some evidence to explain the temporal characteristic of blooms Caused by two species in the Yangtze River Estuary. (C) 2008 Elsevier B.V. All rights reserved.

Evolution of nutrient structure and phytoplankton composition in the Jiaozhou Bay ecosystem

The inventories of nutrients in the surface water and large phytoplankton( > 69 pm) were analyzed from the data set of JERS ecological database about a typical coastal waters, the Jiaozhou Bay, China, from 1960s for N, P and from 1980s; for Si. By examining long-term changes of nutrient concentration, calculating stoichiometric balance, and comparing diatom composition, Si limitation of diatom production was found to be more possible. The possibility of Si limitation was from 37% in 1980s to 50% in 1990s. Jiaozhou Bay ecosystem is becoming serious eutrophication, with notable increase of NO2-N, NO3-N and NH4-N from 0.1417 mumol/L, 0.5414 mumol/L, 1.7222 mumol/L in 1960s to 0.9551 mumol/L, 3.001 mumol/L, 8.0359 mumol/L in late 1990s respectively and prominent decrease of Si from 4.2614 mumol/L in 1980s to 1.5861 mumol/L in late 1990s; the nutrient structure is controlled by nitrogen; the main limiting nutrient is probably silicon; because of the Si limitation the phytoplankton community structure has changed drastically.

Effects of temperature on the threshold of phosphorus for algal blooms

Algal blooms, worsening marine ecosystems and causing great economic loss, have been paid much attention to for a long time. Such environmental factors as light penetration, water temperature, and nutrient concentration are crucial in blooms processes. Among them, only nutrients can be controlled. Therefore, the threshold of nutrients for algal blooms is of great concern. To begin with, a dynamic eutrophication model has been constructed to simulate the algal growth and phosphorus cycling. The model encapsulates the essential biological processes of algal growth and decay, and phosphorus regeneration due to algal decay. The nutrient limitation is based upon commonly used Monod's kinetics. The effects of temperature and phosphorus limitation are particularly addressed. Then, we have endeavored to elucidate the threshold of phosphorus at different temperature for algal blooms. Based on the numerical simulation, the isoquant contours of change rate of alga as shown in the figure are obtained, which obviously demonstrate the threshold of nutrient at an arbitrary reasonable temperature. The larger the change rate is, the more rapidly the alga grows. If the phosphorus concentration at a given temperature remains larger than the threshold the algal biomass may increase monotonically, leading to the algal blooming. With the rising of temperature, the threshold is apparently reduced, which may explain why likely red tide disasters occur in a fine summer day. So, high temperature and sufficient phosphorus supply are the major factors which result in algal growth and blowout of red tide.

神农架巴山冷杉天然林凋落物特性的研究

神农架地区的巴山冷杉（Abies fargesii）林是秦巴山地重要的森林生态系统类型，长期以来其在水土保持、水源涵养、林产品供给等方面的生态服务功能受到了广泛的重视，近年来该类森林的生物地球化学循环正成为关注的热点。本文以神农架巴山冷杉天然林为研究对象，从其凋落物的数量、养分、能量3个方面入手，着重研究1)凋落物组成及其凋落量的月变化模式;2)凋落物养分含量及养分年归还量的特征;3）凋落物的能流量及其月变化模式。研究表明： 巴山冷杉天然林的年凋落量为5702.99kg.hm-2，处于亚热带森林年凋落量的范围内;巴山冷杉林的凋落物组成比较丰富，主要有落叶、落枝、球花、球果和其它五部分，其中以落叶为多，占总凋落量的46.00%;凋落量的月变化模式呈双峰型，分别在2006年10-11月和2007年4-5月达到峰值。 巴山冷杉林凋落物养分含量的大小顺序为：N＞K＞Ca＞P＞Mg;N、P、K、Ca、Mg的年归还量分别为：39.1063 kg.hm-2、4.5346 kg.hm-2、13.4367 kg.hm-2、5.4965 kg.hm-2、0.0911 kg.hm-2，以N的年归还量最多;就凋落物各组分的养分年归还量而言，落叶的养分归还量远远大于其余组分的养分归还量，占总归还量的52.65%。因此，不论凋落量还是养分归还量，巴山冷杉林凋落物中的落叶都占有绝对的优势。 在巴山冷杉林凋落物各组分中，干重热值介于20.60 KJ/g 至22.70 KJ/g之间，灰分浓度介于1.38%至5.94%之间，去灰分热值介于21.34 KJ/g至23.55KJ/g之间，充分表明了灰分对热值的影响。在各组分中，无论是干重热值还是去灰分热值，均以落叶的热值最高。从整年来看，落叶的热值在2006年10－11月和2007年6－7月较高。巴山冷杉林通过凋落物的年能流量为 12500.96 KJ.m-2，以落叶能流量最大，占总能流量的47.72%。通过计算凋落物的能流量占太阳有效辐射的百分数可以得出太阳辐射进入凋落物的转化效率，巴山冷杉林凋落物的能量转化效率为0.61%，这在亚热带和热带森林类型中属于中等水平。

新型土壤改良剂对冬小麦生长及养分吸收的影响

通过对冬小麦施加一种以秸秆为主要原料研制的新型土壤改良剂(简称PJG),采用田间试验,探讨其对冬小麦生长、产量、各生长期养分含量及氮、磷累积吸收量的影响。结果表明:施加PJG土壤改良剂能提高小麦地上部各生长期干物质累积量,单施可提高8.4%,与氮肥配施可提高37.8%;可增加植株地上部各器官中氮、磷含量及其累积吸收量,但对钾素影响不大。施加1 500 kg/hm2的PJG改良剂,能较对照增产1.90%,与氮肥配施效果更佳,最高增产9.96%。综合考虑,应用PJG土壤改良剂时应与适量的氮肥配施,对作物的生长和产量的提高效果更佳。

The variation of upper ocean structure and paleoproductivity in the Kuroshio source region during the last 200 kyr

A core from the source region of the Kuroshio warm current (east of the Luzon Island) was analyzed using several proxies in order to study the variability of the Western Pacific Warm Pool (WPWP) during the last two glacial-interglacial cycles. Primary productivity (PP) variations were deduced from variations in the coccolith flora. Primary productivity was higher during glacial periods (the end of Marine Isotope Stage [MIS] 3, some periods in MIS 2 and 6), and decreased during interglacial periods (MIS 7, MIS Se and probably MIS 5c-5d), with the lowest PP in MIS 5e. variations in the delta C-13 difference in benthic and bulk carbonate, thus in the vertical gradient of delta C-13 in dissolved inorganic carbon (Delta delta C-13(c). (wuellerstorfi-N. dutertrei) and Delta delta C-13(c.) (wuellerstorfi-coccolith)) Coincided With the PP Changes, showing that export productivity was low during interglacial periods (MIS 7, MIS 5e and Holocene) and high during glacial periods (MIS 6, probably MIS 5c-5d, late MIS 4 and late MIS 3). Comparison of foraminiferal carbonate dissolution indicators and PP changes reveals that nannofossil assemblage in core Ph05-5 is not sensitive to carbonate dissolution intensity. The depth of the thermocline (DOT) was estimated from planktonic forminiferal assemblages, and was relatively greater during interglacial periods (MIS 7, MIS 5e, probably MIS 5c and Holocene) than during glacials (middle MIS 6, probably MIS 5b and 5d, some periods in MIS 4, MIS 3 and MIS 2). Good coherence between the paleoproductivity records and the DOT suggests that the DOT changes could be the primary control factor in changes of paleoproductivity, and the glacial high productivity in the Kuroshio source region could be associated with a global increase of nutrient concentration in the intermediate waters that upwelled into the photic zone. The low CO2 values derived for intervals of high productivity and a relatively shallow DOT suggest that the changes in biological productivity and DOT in the equatorial Pacific could have modified atmospheric CO2 concentrations. High Sea Surface Temperatures (SSTs) during the warm MIS 5e in combination with intensified monsoonal rain fall could have resulted in a more intense stratification of the upper waters, resulting in low nutrient supply to the surface waters and a resulting decrease in productivity. (C) 2010 Elsevier B.V. All rights reserved.

The main phosphorous sources in the Changjiang estuary

Analysis using historical data on the phosphate sources in Changjiang (Yangtze River) estuary show that phosphate was supplied equally from the east, south, west and north of the estuary. These sources include the Changjiang River, the Taiwan Warm Current (TWC), a cyclone-type eddy, and the 32A degrees N Upwelling, supplying different phosphates in different times, ways and intensities. The magnitude of their supplying phosphate concentration was related with the size in the order of the Changjiang River < the TWC < the 32A degrees N Upwelling < the cyclone-type eddy, and the duration of the supplying was: the Changjiang River > the TWC > the cyclone-type eddy > the 32A degrees N Upwelling. The four sources supplied a great deal of phosphate so that the phosphate concentration in the estuary was kept above 0.2 mu mol/L in previous years, satisfying the phytoplankton growth. The horizontal and vertical distribution of the phosphate concentration showed that near shallow marine areas at 122A degrees E/31A degrees N, the TWC in low nutrient concentration became an upwelling through sea bottom and brought up nutrients from sea bottom to marine surface. In addition, horizontal distribution of phosphate concentration was consistent with that of algae: Rhizosolenia robusta, Rhizosolenia calcaravis and Skeletonema, which showed that no matter during high water or low water of Changjiang River, these species brought by the TWC became predominant species. Therefore, the authors believe that the TWC flowed from south to north along the coast and played a role in deflecting the Changjiang River flow from the southern side.

长江口上升流区营养盐动力学

近年来，东中国海赤潮灾情严重，且74.7%的赤潮集中在 30°30′～32°00′N、122°15′～123°10′E的“赤潮高发区”。在研究该区赤潮成因时，长江口沿岸上升流的影响越来越受到人们的关注，并被一些专家观测和研究。但目前为止，针对该区营养盐动力学特征及其对叶绿素a影响的研究较少，且不系统。 本文根据2004年四个季度月的调查资料，系统地探讨了长江口上升流区营养盐动力学特征；估算了上升流的营养盐通量，并和陆源输入通量进行了比较。初步探讨了上升流对该区营养盐结构和浮游植物生长的影响。为深入研究长江口富营养化和赤潮形成机制提供了参考。 结果表明春季在122°20′～123°00′E，31°00′～32°00′N以北海域存在低温、高盐、低溶解氧的沿岸上升流。它不但可把底层高含量磷酸盐输送到10m层以上海区，而且还为上层海区输入了相对低含量硝酸盐和硅酸盐，从而改善了上层营养盐结构，使得营养盐比值接近Redfield Ratios，同时还改善了上层的透明度；从而有利于浮游植物的繁殖。夏季上升流受到强大的长江冲淡水压制，表现不如春季明显，主体水团出现在122°20′～123°00′E，31°15′～31°50′N海区10m层以下。 在秋、冬季，上升流现象被更强的对流现象所掩盖，表现为台湾暖流表层水的入侵。表、底层水域不仅温、盐度分布十分接近，而且营养盐结构差异也较小。冬季台湾暖流水中的磷酸盐含量远比秋季高，与春、夏季上升流水团中磷酸盐含量接近。硝酸盐和硅酸盐含量比秋季稍高，比春、夏季上升流水团中的含量稍低。 叶绿素a季节性分布表明，在春、夏季的10m层以下水域，叶绿素a受到透明度限制，含量相差不大；而在表层和10m层之间，春季叶绿素a的含量远高于夏季，说明春季的营养盐结构和自然条件更有利于浮游植物的繁荣生长。在秋季台湾暖流水影响的区域，表层叶绿素a含量较夏季稍低。而冬季该区叶绿素a含量则是最低的。 对长江口上升流水团春季营养盐通量的计算结果表明，上升流水团中磷酸盐输送通量远远高于长江径流输入，是其径流通量的两倍以上，可能会成为影响该海区磷酸盐分布以及浮游植物生长的一个值得关注的因素。 关键词：上升流，营养盐动力学，营养盐结构，叶绿素a，长江冲淡水

Forecasting Daily Chlorophyll a Concentration during the Spring Phytoplankton Bloom Period in Xiangxi Bay of the Three-Gorges Reservoir by Means of a Recurrent Artificial Neural Network

A recurrent artificial neural network was used for 0-and 7-days-ahead forecasting of daily spring phytoplankton bloom dynamics in Xiangxi Bay of Three-Gorges Reservoir with meteorological, hydrological, and limnological parameters as input variables. Daily data from the depth of 0.5 m was used to train the model, and data from the depth of 2.0 m was used to validate the calibrated model. The trained model achieved reasonable accuracy in predicting the daily dynamics of chlorophyll a both in 0-and 7-days-ahead forecasting. In 0-day-ahead forecasting, the R-2 values of observed and predicted data were 0.85 for training and 0.89 for validating. In 7-days-ahead forecasting, the R-2 values of training and validating were 0.68 and 0.66, respectively. Sensitivity analysis indicated that most ecological relationships between chlorophyll a and input environmental variables in 0-and 7-days-ahead models were reasonable. In the 0-day model, Secchi depth, water temperature, and dissolved silicate were the most important factors influencing the daily dynamics of chlorophyll a. And in 7-days-ahead predicting model, chlorophyll a was sensitive to most environmental variables except water level, DO, and NH3N.

In situ nutrient removal from aquaculture wastewater by aquatic vegetable Ipomoea aquatica on floating beds

Nutrient-rich effluents caused rising concern due to eutrophication of aquatic environment by utilization of a large amount of formula feed. Nutrient removal and water quality were investigated by planting aquatic vegetable on artificial beds in 36-m(2) concrete fishponds. After treatment of 120 days, 30.6% of total nitrogen (TN) and 18.2% of total phosphorus (TP) were removed from the total input nutrients by 6-m(2) aquatic vegetable Ipomoea aquatica. The concentrations of TN, TP, chemical oxygen demand (COD) and chlorophyll a in planted ponds were significantly lower than those in non-planted ponds (P<0.05). Transparency of water in planted ponds was much higher than that of control ponds. No significant differences in the concentration of total ammonia nitrogen (TAN), nitrate nitrogen (NO3-N) and nitrite nitrogen (NO2--N) were found between planted and non-planted ponds. These results suggested that planting aquatic vegetable with one-sixth covered area of the fishponds could efficiently remove nutrient and improve water quality.

Spatial analysis for spring bloom and nutrient limitation in Xiangxi bay of three Gorges Reservoir

The spatial and temporal dynamics of physical variables, inorganic nutrients and phytoplankton chlorophyll a were investigated in Xiangxi Bay from 23 Feb. to 28 Apr. every six days, including one daily sampling site and one bidaily sampling site. The concentrations of nutrient variables showed ranges of 0.02-3.20 mg/L for dissolved silicate (Si); 0.06-2.40 mg/L for DIN (NH4N + NO2N + NO3N); 0.03-0.56 mg/L for PO4P and 0.22-193.37 mu g/L for chlorophyll a, respectively. The concentration of chlorophyll a and inorganic nutrients were interpolated using GIS techniques. The results indicated that the spring bloom was occurred twice in space during the whole monitoring period (The first one: 26 Feb.-23 Mar.; the second one: 23 Mar.-28 Apr.). The concentration of DIN was always high in the mouth of Xiangxi Bay, and PO4P was high in the upstream of Xiangxi Bay during the whole bloom period. Si seems no obvious difference in space in the beginning of the spring bloom, but showed high heterogeneity in space and time with the development of spring bloom. By comparing the interpolated maps of chlorophyll a and inorganic variables, obvious consumptions of Si and DIN were found when the bloom status was serious. However, no obvious depletion of PO4P was found. Spatial regression analysis could explained most variation of Chl-a except at the begin of the first and second bloom. The result indicated that Si was the factor limiting Chl-a in space before achieved the max area of hypertrophic in the first and second bloom period. When Si was obviously exhausted, DIN became the factor limiting the Chl-a in space. Daily and bidaily monitoring of Site A and B, representing for high DIN: PO4P ratio and low DIN:PO4P ratio, indicated that the concentration of Si was decreased with times at both site A and B, and the dramatically drop of DIN was found in the end monitoring at site B. Multiple stepwise regression analysis indicated that Si was the most important factor affect the development of spring bloom both at site A and B in time series.

Response of growth and fatty acid compositions of Nannochloropsis sp to environmental factors under elevated CO2 concentration

Nannochloropsis sp. was grown with different levels of nitrate, phosphate, salinity and temperature with CO2 at 2,800 mu l l(-1). Increased levels of NaNO3 and KH2PO4 raised protein and polyunsaturated fatty acids (PUFAs) contents but decreased carbohydrate, total lipid and total fatty acids (TFA) contents. Nannochloropsis sp. grew well at salinities from 22 to 49 g l(-1), and lowering salinity enhanced TFA and PUFAs contents. TFA contents increased with the increasing temperature but PUFAs contents decreased. The highest eicosapentaenoic acid (EPA, 20:5 omega 3) content based on the dry mass was above 3% under low N (150 mu M NaNO3) or high N (3000 mu M NaNO3) condition. Excessive nitrate, low salinity and temperature are thus favorable factors for improving EPA yields in Nannochloropsis sp.

Growth of Gracilaria lemaneiformis under different cultivation conditions and its effects on nutrient removal in Chinese coastal waters

Gracilaria lemaneiformis (Bory) Daws has been extensively cultivated as a source of commercial agar and the ecomaterials in Shenao Bay, Guangdong Province, Jiaozhou Bay, Shandong Province and other waters in China. This paper examines the in situ suspended farming of G. lemaneiformis using raft cultivation under different conditions and its effects on nutrient removal in the laboratory. The results showed that cultivated Gracilaria grew well in both Shenao Bay and Jiaozhou Bay. The biomass of Gracilaria increased from 50 to 775 g m(-1) (fresh weight) during 28 days, with special growth rate (SPG) 13.9% d(-1) under horizontal cultivation in Jiaozhou Bay. Light, temperature, nutrient supply, as well as cultivation treatments such as initial density, and depth of suspension seaweed were important to the growth of Gracilaria. The highest biomass production was observed in the horizontal culture condition (0.0 m) and 0.5-1.5 m deep layer in Jiaozhou Bay. However, the highest growth rate in Shenao Bay appeared under the lowest initial stocking density treatment. In the laboratory, the aquarium experiments (fish and seaweed culture systems) demonstrated that Gracilaria was able to remove inorganic nutrients effectively. The concentration of NH4+-N decreased by 85.53% and 69.45%, and the concentration of PO4-P decreased 65.97% and 26.74% in aquaria with Gracilaria after 23 days and 40 days, respectively. The results indicate that Gracilaria has the potential to remove excess nutrient from coastal areas, and the large-scale cultivation of G. lemaneiformis could be effective to control eutrophication in Chinese coastal waters. (c) 2005 Elsevier B.V. All rights reserved.

Nutrient characteristics in the Yangtze River Estuary and the adjacent East China Sea before and after impoundment of the Three Gorges Dam

From November 2002 to 2006, five cruises were undertaken in the Yangtze River Estuary and the adjacent East China Sea to compare the nutrient concentrations, ratios and potential nutrient limitation of phytoplankton growth before and after impoundment (June 2003) of the Three Gorges Dam (TGD). Concentrations of dissolved inorganic nitrogen (DIN), soluble reactive phosphorus (SRP) and total nitrogen (TN) exhibited an increasing trend from 2002 to 2006. In contrast, total phosphorus (TP) concentration exhibited a decreasing trend. The mean concentrations of DIN, SRP, and TN in the total study area increased from 21.4 mu M, 0.9 mu M, and 41.8 mu M in 2002 to 37.5 mu M, 1.3 mu M. and 82.2 mu M in 2006, respectively. while TP decreased from 2.1 mu M to 1.7 mu M. The concentration of dissolved reactive silica (DRSi) had no major fluctuations and the differences were not significant. The mean concentration of DRSi in the total study area ranged from 52.5 to 92.3 mu M. The Si:N ratio decreased significantly from 2.7 in 2002 to 1.3 in 2006, while TN: TP ratio increased from 22.1 to 80.3. The area of potential P limitation of phytoplankton growth expanded after 2003 and potential Si limitation appeared in 2005 and 2006. Potential P limitation mainly occurred in an area of salinity less than 30 after 2003, while potential Si limitation occurred where the salinity was greater than 30. By comparison with historical data, the concentrations of nitrate and SRP in this upper estuary during November 1980-2006 increased obviously after impoundment of TGD but DRSi decreased. Meanwhile, the ratios of N:P, Si:N and Si:P decreased obviously. (c) 2009 Elsevier B.V. All rights reserved.

Nutrient Dynamics in the Upwelling Area of Changjiang (Yangtze River) Estuary

Nutrient dynamics and its influence on the distribution of chlorophyll-a in the upwelling area of the Changjiang (Yangtze) River estuary were investigated in the spring (May) and summer (August) of 2004. In the spring, upwelling was apparent in the region of 122 degrees 20'-123 degrees 00' E, 31 degrees 00'-32 degrees 00' N and was associated with low temperature (16-21 degrees C), high salinity (24-33 practical salinity units [psu]), and low dissolved oxygen (2.5-6.0 mg L-1) in the upper 10 m of the water column. The spring upwelling increased the mixed-layer phosphate, nitrate, and silicate concentrations to roughly 1, 15, and 15 mu mol L-1, respectively, and improved the light transparency in the euphotic zone. This improvement in phytoplankton growing conditions was followed by an increase in chlorophyll-a concentrations. The summer upwelling was weaker and occurred over a smaller geographical area (122 degrees 20'-123 degrees 00' E, 31 degrees 15'-31 degrees 50' N). Strongly influenced by turbid Changjiang diluted water (CDW), it had little impact on the upper 10 m of the water column but instead increased nutrient concentrations at greater depths. The high concentration of particulates in the CDW reduced light transmission in the upper 10 m and, hence, limited phytoplankton growth throughout the water column. Chlorophyll-a concentrations in the summer upwelling area were roughly an order of magnitude lower than in the spring. Water clarity, as influenced by the CDW, appears to be the principal factor limiting the impact of upwelling on phytoplankton biomass in this area.