洞庭盆地介形类现生种分布、生态特征及基于其水深转换函数的建立

The Holocene climate evolution, very closely relates to human existence and development, is a focus of the global change research. The middle reaches of the Yangtze River, located in the transitional zone for Chinese east/west and south/north natural environment, very sensitive to climate changes, is an important window for study of Chinese Holocene climate evolution and global change. The Dongting Basin, located in the middle reaches of the Yangtze River, as an important and typical Quaternary basin, is of great potential for high-precision reconstruction of regional paleoclimate. The detailed regional ecological investigation of the recent ostracod is the necessary premise and base for making full use of the fauna potential on paleoclimate analysis. The surface sediment and the corresponding bottom water are sampled in surface waters of the basin synchronously in every season. Physicochemical characteristics (including water depth, salinity, water temperature, pH value, dissolved oxygen, etc) of the water sample, taxonomy, taphonomy and ecology features of the recent ostracod and the fauna distribution responses to environmental parameters, are analysised using the method of canonical correspondence analysis (CCA). Based on the related results, the ostracod-based transfer functions for water depth are established using different methods of regression (including weighted average partial least squares regression, WA-PLS and weighted average binomial regression, WA-BR). Hence, the research can provide the necessary base for high resolution and quantitative Holocene paleoclimate reconstruction of the basin using ostracod sedimentary records and the basic data for deep understanding paleoclimate evolution of the middle reaches of the Yangtze River Holocene and Quaternary, and enrich ecological environment data of the recent ostracod from the middle reaches of the Yangtze River and China, especially the quantitative data.

全新世气候演化是全球变化研究的重点与热点之一。长江中游地区为研究我国全新世气候演化及全球变化的重要窗口。洞庭盆地全新统是重建本区古气候的良好材料。介形类为良好的古气候指标，对其现生种进行详细的区域生态调查是充分发挥该指标潜力的必要前提与基础。本项目以洞庭盆地介形类现生种为研究对象，按季节同步采集各类地表水体表层沉积物与相应底层水样。分析水样的物化性质（水深、盐度、水温、pH值及溶氧量等），研究介形类现生种分类学、埋藏学及生态学特征。利用典范对应分析方法研究该物种分布对环境参数的响应。在此基础上，采用加权平均偏最小二乘回归法与加权平均二项式回归法分别建立基于介形类的水深转换函数。本研究可为利用介形类等沉积记录高分辨率且定量重建洞庭盆地全新世古气候奠定基础，为深入认识长江中游地区全新世及第四纪气候演化积累基础数据，同时丰富长江中游地区及我国介形类现生种生境数据，尤其是定量数据。

洞庭湖所在区域为研究我国全新世气候演化及全球变化的重要窗口，该区域全新世古气候研究薄弱，未见定量研究。对介形类现生种进行详细生态调查是利用其定量重建古气候的必要前提与基础。洞庭湖介形类包含6属10种，比利时舍氏玻璃介（相似种）Schellencandona cf. belgica、布氏土星介Ilyocypris bradyi、粗糙土星介Ilyocypris salebrosa、豆形豆形玻璃介Fabaeformiscandona fabaeformis、克氏丽星介 Cypria kraepelini、喙盲星介（相似种）Typhlocypris cf. rostrata、无偶斗星介 Cypridopsis vidua及斗星介属（未定种）Cypridopsis sp.，其中C. sp.包含3个种。S. cf. belgica、I. bradyi及F. fabaeformis为洞庭湖优势种，分布广且丰度高，四季均有发现。各属种生境参数虽存在一些差异，但不明显，总范围为水温6.34-28.56 ℃，pH 7.34-8.78，溶氧量5.14-13.96 mg/L，电导率197-391 μS/cm，水深1-8.8 m。其中，主要分布于水深1-4 m。利用典范对应分析方法研究了介形类分布对环境参数的响应。对介形类影响最大的环境因子是水深，其次是溶氧量。S. cf. belgica对水深最为敏感，C. sp.1也具一定敏感性，其余属种均不敏感。因此，采用加权平均偏最小二乘回归法建立基于介形类的水深转换函数意义不大，仅采用加权平均二项式回归法。但C. sp.1出现频率与丰度均很低，故不利用该属种建立转换函数。S. cf. belgica丰度与出现频率均高，适合利用其数据建立转换函数。故采用加权平均二项式回归法建立了基于S. cf. belgica的水深转换函数，该函数具有较好的预测能力。本研究可为洞庭湖所在区域利用介形类定量重建全新世古气候奠定基础，同时丰富我国该生物现生种生境数据。