基于浮游植物生物完整性的黄河口近岸海域生态健康评价

Ecological health assessment on the coastal waters in the Yellow River estuary using phytoplankton index of biotic integrity (P-IBI)

中文关键词: 浮游植物  生物完整性指数  生态健康评价  黄河口

英文关键词: Phytoplankton  Index of biotic integrity (IBI)  Ecological health assessment  Yellow River estuary

中文摘要:

      为系统评价黄河口近岸海域生态健康状况，2020年在该海域开展了3次浮游植物调查，共布设采样点31个，采集浮游植物4门73种，以硅藻门(Bacillariophyta)浮游植物种类最多，占82.19%。根据生物多样性指数H´确定参照点和受损点，通过判别能力分析和相关性分析进行指标筛选，确定不同月份的浮游植物完整性指数(P-IBI)核心指标；以核心指标在全部采样点的95%或5%分位数为标准，采用比值法计算各指标分值，从而获得各站点的P-IBI总分值，并根据相应标准确定各站点的生态状况等级，采用1、3、5分赋值法对各站点的生态状况赋分，获得黄河口近岸海域健康评价综合分值。结果表明，不同月份的各调查站位生态状况等级不同且空间分布差异显著。5月，“优”状态站位较少(9.68%)且分散分布于黄河入海口周边区域；7月，“优”状态站位达35.48%，主要分布在黄河入海口口门及莱州湾水域；12月，“优”状态站位高达38.71%且主要分布在入海口以北水域。P-IBI与氨氮(NH4-N)呈极显著正相关，与硝酸盐(NO3-N)、磷酸盐(PO4-P)、溶解氧(DO)呈极显著负相关，与表层水温(SST)呈显著正相关。健康评价综合分值表明，2020年黄河口近岸海域健康状况一般。本研究结果可为区域生态管理提供科学依据。

英文摘要:

      Ecosystem integrity is the foundation of ecosystem health and is popular to quantitatively analyze ecosystem integrity using the Index of Biotic Integrity (IBI). The IBI was initially used as a water pollution index and has been widely applied in ecosystem health assessment, particularly in fish, benthos, and plankton. Phytoplankton is the primary producer in aquatic ecosystems and is sensitive to changes in environmental factors. The Phytoplanktonic IBI (P-IBI) has been increasingly used in the ecosystem health assessment of bays, rivers, lakes, and reservoirs. However, no reports are available on applying P-IBI in the estuary ecosystem. Based on P-IBI, this study constructed an ecological health assessment indicator system and built an evaluation criterion in the coastal waters of the Yellow River estuary. To evaluate the ecological health status, three surveys were conducted on phytoplankton in May, July, and December of 2020. A total of 31 sampling sites were set up in the study area (119°00′E–119°25′E, 37°20′N–38°05′N), and 73 species of phytoplankton from four phyla were collected, with diatoms being the major groups and the species number accounting for 82.19%. The reference points and damaged points were determined according to the Shannon-Wiener diversity index H´, and the sites with H´≥3 were reference points; the others were damaged points. Considering factors such as ecological characteristics of the study area, phytoplankton population distribution, and data availability, 13 biological indicators were selected as candidate indicators. Then, the core indicators of P-IBI in various months were identified by screening candidate indicators. First, the discriminant ability analysis was used to preliminarily select the indicators, and their IQ≥2 were retained. Second, Pearson correlation analysis was conducted for these indicators. The P-IBI core indicator system in May, July, and December contained four, five, and four biological indicators, respectively. The scores of each indicator were calculated using the ratio method. The 95% or 5% quantile of the core indicators in all sampling sites was regarded as the best expected value; for indicators which increased with increasing interference, the best expected value was 5% quantile. Conversely, for indicators which decreased with increasing interference, the best expected value was 95% quantile. Each indicator score was calculated using a different formula according to their response to interference. Accumulating all core indicator scores at the same site, the total P-IBI score for this site was obtained. The 25% quantile of the reference points P-IBI was taken as IBI-expected, the P-IBI range less than IBI-expected was quartered. The delineation standard for the ecological status grade was ascertained, and the ecological status level of each site was identified according to its total P-IBI. The ecological status of each site was marked by using 1, 3, and 5 approximations of value assignment, the marked scores of each site were summed up using the equal weight method, and standardization was conducted to eliminate the differences caused by various indicator numbers. The comprehensive evaluation index (CEI) of the coastal waters in the Yellow River estuary was achieved. The results showed that the ecological status in each site was different and the spatial distribution was significantly diverse for the three months. In May, a few sites were present with excellent levels (9.68%), and they were scattered around the mouth of the Yellow River. In July, the proportion of sites with excellent levels reached 35.48%, and they were mainly located in the estuary of the Yellow River and Laizhou Bay. In December, the proportion of sites with excellent status was approximately 38.71%, and they were concentrated in the waters north of the Yellow River estuary. In general, concerning the stations above “good” ecological level, 21 were present in May; 29, in July; and 26, in December; therefore, the ecological condition was slightly worse in May. P-IBI had a significant positive correlation with ammonium (NH4-N), a significant negative correlation with nitrate (NO3-N), phosphate (PO4-P), and dissolved oxygen (DO), and a significant positive correlation with sea surface temperature (SST). However, no significant correlation was observed between P-IBI and sea surface salinity (SSS), pH value (pH), nitrite (NO2-N), and silicate (SiO3-Si). The CEI indicated the health status was “fair” in the coastal waters of the Yellow River estuary in 2020. Selecting reference points and screening biological parameters were the key steps in constructing the P-IBI indicator system, which determined the science of the evaluation result and the practicality of regional health management. The detailed method was offered in this study, and it could provide information for other research projects. This study provided a reference for the health management and ecological restoration of this water area and offered data support for the ecological protection and high-quality development of the Yellow River Basin.