胶州湾秋季海水低分子量有机酸转化速率的分布特征

Distribution Characteristics of Low Molecular Weight Organic Acid Conversion Rates in Seawater of the Jiaozhou Bay During Autumn

为考察近海海水中低分子量有机酸(Low Molecular Weight Organic Acids,LMWOAs)的分布、来源和转化,系统研究了2022年11月胶州湾海水中LMWOAs的组成,以及其浓度和转化速率的分布特征,通过相关分析探讨了不同LMWOAs组分之间的关系,以及影响LMWOAs转化速率的因素。结果表明,秋季胶州湾海水中的乳酸(Lactic Acid,LA)、乙酸(Acetic Acid,AA)和甲酸(Formic Acid,FA),以及3种酸总量(Total Low Molecular Weight Organic Acids,TOA)的浓度范围分别为0~0.55、0.94~3.39和0~3.35,以及1.24~7.19μmol·L-1,AA平均浓度占TOA的63.99%。LMWOAs浓度较高的区域集中于河口和湾口附近,且整体上表层海水LMWOAs的浓度高于底层,其主要来源是人类活动。加富培养实验结果表明:秋季胶州湾海水在整体上净消耗LMWOAs,其转化速率在不同站位、不同水层呈现复杂的变化,具有局部性、多样性的特点。3种LMWOAs的微生物转化速率与其对应的非生物转化速率出现负相关关系,不同站位海水的微生物活动能够以不同的速率产生和消耗LMWOAs,以净消耗为主,对控制胶州湾海水LMWOAs的转化速率起决定性作用;在没有光化学过程的情况下,非生物过程在不同站位的海水中也能够以不同的速率产生和消耗LMWOAs,以净产生为主,是胶州湾LMWOAs的重要来源。微生物释放的酶对控制LMWOAs转化起关键作用。秋季胶州湾海水中的AA和FA有相似的生物来源,具有相近的新陈代谢过程,其微生物转化速率受到水温、盐度和营养盐因素的显著影响。温度和盐度降低、溶解氧(Dissolved Oxygen,DO)浓度降低、营养盐浓度升高,以及周边河流的输入,都有利于促进秋季胶州湾海水LMWOAs的产生。

To investigate the distribution,source and conversion of low molecular weight organic acids(LMWOAs)in coastal seawater,the distribution characteristics of composition,concentration and conversion rates of LMWOAs in the Jiaozhou Bay were systematically investigated during November 2022.Correlation analyses were applied to explore the relationship between different components of LMWOAs and the factors influencing their conversion rates.The results showed that during autumn the concentrations of lactic acid(LA),acetic acid(AA),formic acid(FA)and the total concentration of these three acids(TOA)in the Jiaozhou Bay were within the ranges of 0 to 0.55,0.94 to 3.39,0 to 3.35,and 1.24 to 7.19μmol·L-1,respectively.Average concentration of AA accounted for 63.99%of TOA.High concentrations areas of LMWOAs were predominantly observed near the estuaries and the bay entrance,and the overall concentrations of LMWOAs in the surface seawater were consistently higher than those in the bottom layer,indicating their sources originated from human activities.The results from enrichment culture experiments revealed that the seawater of the Jiaozhou Bay exhibited a net consumption of LMWOAs during autumn.Their conversion rates showed complex variations in different stations and different water layers with characteristics of locality and diversity.A negative correlation was observed between the microbial conversion rates of the three LMWOAs and their corresponding non-biological conversion rates.Microbial activities in the seawater from different stations could produce and consume LMWOAs at different rates,primarily resulting in net consumption,and microorganisms were found to play a critical role in controlling the conversion rates of LMWOAs in the seawater of the bay.In the absence of photochemical processes,non-biological mechanisms produced and consumed LMWOAs at differing rates among various stations,predominantly resulting in net production,as important source of LMWOAs in the bay.The enzymes released by microorganisms played crucial roles on controlling the conversion of LMWOAs.During autumn,in the seawater of the Jiaozhou Bay,AA and FA shared similar biological origins with similar metabolic processes,and their microbial conversion rates were obviously influenced by water temperature,salinity and nutrient levels.In the seawater of the Jiaozhou Bay,several factors promoted the production of LMWOAs in autumn,including decreased water temperature,decreased salinity and concentrations of dissolved oxygen,increased concentrations of nutrients,and input from surrounding rivers.