第 42 卷 第 6 期 水 生 生 物 学 报 Vol. 42, No. 6 2018 年 11 月 ACTA HYDROBIOLOGICA SINICA Nov., 2018 doi: 10.7541/2018.141 MAPPING SPATIOTEMPORAL TRENDS IN THE ABUNDANCE AND DISTRIBUTION OF MACROPHYTES IN HONGZE LAKE GUO Chuan-Bo1, LI Wei1, ZHANG Ying-Xue1, 2, XIA Wen-Tong1, 2, XIN Wei1, CHEN Yu-Shun1, 2 and LI Zhong-Jie1, 2 (1. State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China; 2. University of Chinese Academy of Sciences, Beijing 100049, China) Abstract: A comprehensive investigation on macrophyte community in Hongze Lake was conducted seaso- nally from May 2010 to February 2011. Overall, twelve species representing eight families of macrophytes were identified in Hongze Lake, including nine species of submerged plants, two species of floating-leaved plants, and one species of emerging plant. In general, Potamogeton malaianus, P. maackianu, P. pectinatus and P. crispus were the four dominant species throughout the whole year, the highest biomass of macro- phytes was presented in autumn, followed by summer and winter, while spring had the lowest biomass of macrophytes. Based on field data, we used kriging interpolation in ArcGis to map the spatiotemporal distribu- tion of the entire macrophyte community as well as each of the four dominant species. From the GIS maps we observed that the northern area of the lake, namely the Chengzihu region, had the highest biomass of macro- phytes potentially as a result of better water quality and greater transparency. Potential factors that affected the community structure, biomass, and distribution patterns of macrophytes considerably were then discussed. The results of this study illuminate the need for more information on the role and importance of aquatic mac- rophytes in shallow lake ecosystems. Conservation of macrophytes should be taken to maintain the lake eco- system health. Key words: Macrophyte community; GIS and GPS; Hongze Lake; Spatiotemporal patterns; Shallow lakes CLC number: S932.8 Document code: A Article ID: 1000-3207(2018)06-1153-10 Macrophytes play an important role in the struc- macrophytes in shallow lake ecosystems is related to ture and functioning of shallow freshwater ecosys- their structural attributes such as species composition, tems[1—3]. They serve as a base of most aquatic food- distribution, abundance, and diversity. These attri- webs, and also produce food for biota, provide refu- butes which in turn rely on various environmental gia for other organisms[4], anchor soft bottom sedi- factors including water level, water temperature, sub- ments, remove suspended particles and nutrients[4], strate composition, disturbance, competitive interac- and contribute to the promotion and maintenance of tions, herbivory, epiphyte loading, water quality and aquatic foodwebs and ecosystem services[5, 6]. Macro- sediment nutrients[3, 9—11]. Therefore understanding phytes also contribute to the general fitness and di- and quantifying the community structure and spati- versity of aquatic ecosystems by serving as indicators otemporal patterns of macrophytes is indispensable for water quality and aiding in nutrient cycling[7, 8]. As for integrated management practices and aquatic con- a result of their significance, macrophytes are com- servation in shallow lake ecosystems. An example of monly viewed as one of the most important foci in a macrophyte-driven shallow water ecosystem is that shallow lake ecosystems. Generally, the function of of Hongze Lake. Received date: 2016-06-21; Accepted date: 2018-01-17 Foundation item: Supported by Chinese Academy of Sciences Grants (Y62302, Y45Z04,Y55Z06 and QYZDB-SSW-SMC041); National Natural Science Foundation of China (31602158) Corresponding author: Chen Yu-Shun, E-mail: [email protected] 1154 水 生 生 物 学 报 42 卷 Hongze Lake (33°06′—33°40′N, 118°10′— 118° ecosystem provides multiple benefits to various stake- 52′E), which lies in the middle reach of the Huaihe holders. Hongze Lake acts as a navigation junction, River, is the fourth largest freshwater lake in China aids flood-and-drought resistance, provides fishing 2 with a surface area of 1597 km , a mean water depth and aquaculture opportunities, as well as supports [12] of 1.7 m . Hongze Lake is also the largest storing biodiversity conservation and tourism in eastern reservoir and water channel on the east route of the China[12, 13]. China’s South-North Water Division Project (SN- 1.2 Sampling procedure [13] WDP) . Hongze Lake ecosystems provide multiple Four field surveys were conducted in Hongze benefits that are fundamental to human wellbeing, in- Lake during 2010－2011 in spring (May), summer cluding commercial navigation, flood control, com- (August), autumn (November) and winter (February) mercial fishing, aquaculture, biodiversity conserva- respectively. Finally, a total of 631 sites, each consist- [12, 13] tion, and tourism in eastern China . However, ing of a 0.125 m2 quadrat, were randomly selected in Hongze Lake has also experienced numerous natural the whole lake according to the lake morphology and and artificial disturbances in recent years, such as re- habitat heterogeneity. Seasonaly, we sampled 173, gional climate change, high nutrients inputs, water 173, 130 and 155 sites during spring, summer, au- conservancy construction, recreational and commer- tumn and winter respectively. Throughout sampling, cial fishing, and aquaculture. As a result of these dis- we avoided selection of area near intensive block nets turbances, aquatic macrophytes have seen great de- in the lake (Fig. 1). Within each 0.125 m2 sampling clines, specifically the biomass and species diversity [13, 14] quadra in each of the sampling site, all macrophytes has decreased whilst distributional areas shrunk . were uprooted with a bottom sampler. All macro- These alterations have the potential to affect the dis- phytes were then cleaned, identified into species fol- tribution patterns and community structure of other lowing Cook[18] and then weighed to the nearest 0.1 g organisms which can ultimately, affect the overall [15] wet weight in the field immediately. The geographic health of the lake ecosystem . coordinates of each sampling site were recorded us- However, very little knowledge about the spatial ing a handling GPS unit (Garmin eTrex 301). and temporal dynamics of macrophytes in Hongze 1.3 Data processing and GIS mapping Lake exists, mainly due to the fact that large-scale and The relative biomass (B ), frequency of occur- long-term field monitoring efforts for macrophytes in ri rence (F ) and degree of dominance (D ) were calcu- such a large lake presents numerous challenges. Pre- i i lated according to the following equations[19]: vious studies of macrophytes in Hongze Lake have only been conducted with very limited datasets either B ri = B i=B t 100 (1) [14, 16] £ on a small spatial scale or during a single season . Fi = N i=N t 100 (2) The current study was conducted by integrating GPS £ D i = (B ri + Fi) =2 (3) and GIS technologies with field monitoring data to simulate the community structure and spatiotemporal Where Bri is the relative biomass of the species i, Bi is patterns and dynamics of macrophytes in the whole the biomass of the species i, Bt is the total biomass of Hongze Lake. The main objective of our study was to all the species; Fi is the frequency of occurrence of map the distribution patterns and seasonal dynamics species i, Ni and Nt is the occurrence number of spe- of macrophytes community structure in Hongze Lake cies i and the total sampling sites, respectively; Di is across broad spatial and temporal scales. The results the degree of dominance. of this study will benefit the conservation of macro- The spatiotemporal patterns of the total macro- phytes resources in not only Hongze but other shal- phytes biomass and four dominant macrophyte were low lakes as well. then mapped using Arcgis 10.1 (ESRI) using the Kri- ging interpolation utility on a map of Hongze Lake 1 Materials and Methods that was modified from Google Earth (Google 1.1 Study area Earthtm). Hongze Lake is the fourth largest freshwater lake 2 2 Results in China with a surface area of 1597 km , and a mean water depth of 1.7 m[12]. The rivers draining into 2.1 Community structure of macrophytes Hongze Lake are located primarily along the western A total of twelve species belong to eight fami- bank of the lake. Among them, the Huaihe River is lies of macrophytes were identified from the whole the largest, and contributes 87% of the total inflow to Hongze Lake. Collections included nine species of the lake[12]. Hongze Lake is a transitional lake, mean- submerged plants (Potamogeton malaianus, Myrio- ing the water levels of the lake often undergo large phyllum spicatum, P. maackianus, P. pectinatus, Hy- annual and seasonal changes[17]. The Hongze Lake drilla verticillata, Ceratophyllum demersum, Elodea 6 期 郭传波等: 洪泽湖大型水生植物群落结构和时空格局的GIS模拟 1155 nuttallii, P. crispus, Vallisneria natans), two species lowest macrophyte biomass (Fig. 2). In particular, of floating-leaved plants (Eichhornia crassipes, high biomasses of P. crispus observed mostly during Trapa bispinosa) and one species of emerging plant spring and winter had disappeared by summer, while (Miscanthus sacchariflorus). The greatest biomass of biomasses of E. nuttallii and M. sacchariflorus in- macrophytes were observed during autumn, followed creased only during spring (Tab. 1; Fig. 2). by summer and winter, while spring contained the Macrophyte communities in Hongze Lake were 118°20′E 118°30′E 118°40′E 118°50′E 33°40′N SpringN Summer N Hongze Lake Hongze Lake 33°30′N 33°20′N 33°10′N 33°00′N 0 5 10 20 Sampling site 0 5 10 20 Sampling site km km Autumn N Winter N Hongze Lake Hongze Lake Sampling site Sampling site 0 5 10 20 0 5 10 20 km km Fig.