Particulate and dissolved amino acids in the lower Mississippi and Pearl Rivers (USA)

In this study, we present seasonal changes (monthly samples from September 2001 to August 2003) in the abundance and composition of dissolved and particulate amino acids, at one station in the lower Mississippi and Pearl Rivers (LA, MS: USA). Spatial changes over a 4-day transmit from river km 390 to river mouth (Head of Passes, LA) in the Mississippi River, and a two-day downstream sampling from Jackson (MS) to Stennis Space Center (MS) were also determined. Temporal data in the lower Mississippi River showed significantly lower concentrations of dissolved combined amino acids (DCAA, 0.8 to 2.2 μM) and dissolved amino acids in high molecular weight fraction (HMW DAA, 0.2–0.4 μM) than in the Pearl River (DCAA, 1.4–4.3 μM; HMW DAA, 0.4–1.4 μM). Dissolved free amino acids (DFAA) were significantly lower than DCAA in both rivers, and displayed minimal seasonal variability. DCAA, HMW DAA, and particulate amino acids (PAA) were generally higher during high-flow periods, which may have suggested dominance in terrestrial sources. Carbon-normalized yield of PAA (%C-PAA) was generally higher during low-flow conditions and positively correlated with chlorophyll-a (chl-a), reflective of in situ sources. Downstream variability in the lower Mississippi River showed stable DCAA concentrations, a decline in PAA (from 1.06 to 0.43 μM), and a gradual increase in mole percent of non-protein amino acids (%NPAA). This likely reflected bacterial degradation of phytoplankton biomass during falling discharge. Nitrogen-normalized yield of PAA (%N-PAA) was inversely correlated with PAA (R = − 0.7, n = 48), indicative of short-term sedimentation and resuspension events. Conversely, downstream decreases in DCAA and middle-reach peaks of PAA and %N-PAA in the Pearl River, likely resulted from photochemical degradation of DOM as well as algal production during base-flow conditions. The comparisons in abundance and composition of DAA and PAA in these different river systems provides important information on in situ nitrogen and carbon cycling as related to riverine inputs of organic matter to coastal ocean.     

秋季南黄海表层海水中溶解氨基酸的分布与组成研究

用高效液相色谱法对2010年9月南黄海33个站位表层海水中总水解氨基酸(THAA)、溶解游离氨基酸(DFAA)、溶解结合氨基酸(DCAA)的分布、组成以及它们与环境因子的相关性进行了研究。结果表明:THAA平均浓度为2.08μmol/L,DFAA平均浓度为0.39μmol/L,DCAA平均浓度为1.69μmol/L。THAA浓度的分布大致呈近岸高、远岸低的特点;DFAA分布的规律性较差,在东部海域(中心约在35°N,123°E)出现高值。相关性分析显示溶解氨基酸与叶绿素a(Chl-a)、溶解无机氮(DIN)、细菌丰度、温度和盐度之间均无显著相关性。THAA中含量较高的个体氨基酸为丝氨酸、甘氨酸、天门冬氨酸、谷氨酸和丙氨酸,总和占70.59%。DFAA、DCAA中的主要成分与THAA基本相同。THAA中个体氨基酸的组成以34°N为界分为南北2个海区呈现明显的区域性特点。     

大亚湾海域溶解游离氨基酸及其与环境的关系

对大亚湾海域溶解游离氨基酸(DFAA)的分布特征及其影响因素进行了研究。现场采样调查分别于1995年5月、11月和2000年4月进行。结果表明 :(1)大亚湾海域DFAA的含量较高 ,在0.69～4.73μmol/L之间 ,平均2.16±0.87μmol/L,可能主要源于较为旺盛的生物活动 ;(2)DFAA含量在海域的平面分布变化较大 ,垂直分布和季节及年变化不明显 ;(3)DFAA与海水中的DOC呈正相关、与叶绿素呈负相关关系 ,与TIN的相关性则呈季节变化 ,生物效应可能是影响该海域DFAA含量的主要因素。     

胶州湾海水中溶解氨基酸的研究

于１９８６年１月－１１月用高效液相色谱法分析胶州湾１０个站位表层和底层海水中溶解游离氨基酸（ＤＦＡＡ）的组成、含量的分布及其季节变化。结果表明，７个站位的表层海水中月平均总溶解游离氨基酸（ＴＤＦＡＡ）含量范围为１．２４－２．２８ｕｍｏｌ／Ｌ。多数站位在２月份处于最低值（０．４ｕｍｏｌ／Ｌ），１１月份达最高值（５．０ｕｍｏｌ／Ｌ）。所测氨基酸中，Ｇｌｕ，Ｇｌｙ、Ａｒｇ、Ｌｅｕ，Ｏｒｎ，Ｓｅｒ等占优势     

Dissolved free amino acids in coastal seawater using a modified fluorometric method

The method of Parsonset al. (1984) for measuring dissolved free amino acids (DFAA) in coastal seawater was modified. We found considerable interference in DFAA determination from ammonia dissolved in coastal seawater, although the interference of urea could be ignored. For DFAA analysis for coastal seawater samples, ammonia determinations for the same sample are needed to correct DFAA values. For coastal surface seawater samples from all over the Seto Inland Sea, Japan, values of DFAA ranged from undetectable to 1.87 μg-at N/l when corrected for ammonia, while uncorrected values ranged from undetectable to 2.61 μg-at N/l. DFAA, urea, nitrate+nitrite, ammonia and DON concentrations in surface seawater collected in the Seto Inland Sea were analyzed simultaneously. DFAA at four seasons constituted from 1.4 to 10.1% of DON, with a mean value of 6.5%. The concentration of urea was similar to that of DFAA and often higher than that of ammonium, although generally lower than that of nitrate.     

高效液相色谱法测定海水中溶解态游离氨基酸

采用邻苯二甲醛柱前衍生-高效液相色谱-荧光检测器(OPA—HPLC-FLD)联用技术分离测定了海水中的14种主要溶解游离氨基酸(DFAA),通过邻苯二甲醛—3-巯基丙酸(OPA—3-MPA)柱前衍生后,在XDB-C18柱上分离。不同氨基酸测定的精密度(RSD)为1.62%~3.80%,检测限为11.4~69.7 ng.L-1,海水加标回收率在92%~110%之间。利用该方法测得青岛近海表层海水中氨基酸浓度为0.015~0.284μmolL-1。     

小角刺藻生长过程中溶解游离氨基酸含量在海水中的变化

于1986年12月-1987年2月在温度为25±1℃下培养小角刺藻，以HPLC法测定该藻在培养过程中海水的溶解游离氨基酸（DFAA）含量变化。结果表明，小角刺藻不仅是海水中DFAA的主要生产者，而且也是DFAA的消耗者。小角刺藻不仅在缺乏硝酸盐的时候要吸收DFAA，即使在硝酸盐充足的情况下也会吸收。在小角刺藻的生长初期，水体中DFAA的含量迅速降低，而在后期却又大大增高。在小角刺藻的不同生长阶段，水体中DFAA的组成也不同。这些都可以说明海洋中DFAA的含量、组成和地区分布是密切地同浮游植物群落的繁殖消亡过程相关联的。     

Distribution of dissolved free amino acids, dissolved inorganic nitrogen and chlorophyll a in the surface microlayer and subsurface water of the Yellow Sea, China

Concentrations of 14 different dissolved free amino acids (DFAA), dissolved inorganic nitrogen (DIN), and chlorophyll a were determined in the surface microlayer and subsurface waters at 41 stations in the Yellow Sea, China in April 2006. The concentrations of DFAA in the subsurface water ranged from 0.13 to 1.62 μM, with an average of 0.57±0.05 μM, while those in the surface microlayer varied between 0.22 and 2.6 μM, with an average of 0.94±0.08 μM. Major constituents of DFAA present in the study area were glycine, alanine, glutamic acid, serine and histidine. One-way analysis of variance (ANOVA) showed no significant difference in average mol fractions of DFAA between microlayer and subsurface water (F=0.0440, P=0.8355). Hierarchical cluster analysis of the station similarity based on the DFAA composition in both the surface microlayer and subsurface water separated three clusters of stations at the 70% Bray–Curtis similarity level. The average concentrations of chlorophyll a and DIN were 1.18 (0.34–4.44) μg L⁻¹ and 16.57 (3.98–49.59) μM in the subsurface water, and those in the surface microlayer were 1.30 (0.24–3.97) μg L⁻¹ and 18.56 (5.77–48.93) μM, respectively. Our results showed that concentrations of chlorophyll a (r²=0.7940, n=41, p<0.0001), DIN (r²=0.6939, n=41, p<0.0001) and DFAA (r²=0.2416, n=41, P=0.0011) in the microlayer were, respectively, correlated with their subsurface water concentrations, implying that there was a strong exchange effect between the microlayer and subsurface water. The enrichment factor of DFAA in the microlayer ranged from 0.47 to 2.24 with a mean of 1.88±0.16.