Evolution of Lake Erhai ecological system in China

Transcription

1 Evolution of Lake Erhai ecological system in China Prof. Wang Sheng-Rui Research Center for Lake Ecology & Environments of CRAES 5 August 2013

2 Outline 1 Overview of Lake Erhai ecological environment 2 Analysis the reason of the aquatic plant degradation 鄱阳湖主要生态环境问题 3 Focused question

3 1. Overview of Lake Erhai ecological environment problems 1.1 General situation of Lake Erhai (south-west in China) Basin areas 2565km 2,area 251km 2 Mean deep m, Rivers 26 (inter rivers 25, and out rivers 1) Capacity of water 2700 M m 3,interring water 800 M m 3, water sources is short Chorography of Lake Erhai Picture of Erhai Lake Location of Lake Erhai

4 1. Overview of Lake Erhai ecological environment 1.2 The eutrophic level of Lake Erhai is not optimistic ( N, P increase) water quality decrease from class Ⅱto class Ⅲ 浓度 (mg/l) Concentration of N Lake Erhai from ClassⅡ 年洱海水体 TN 浓度变化 Class Ⅲ 2001 Year 年份 5 Year

5 1. Overview of Lake Erhai ecological environment 1.3 N, P pollution in the sediment is heavier. Although the amount of its released is small, flux of N and P released accounting for about and 15-20% of the total. But its release risks can not be ignored (N/P heavy). 北部 中部 Polluted level transition layer Normal sediment layer 污染层和过渡层厚度放大了 100 倍 (10-30 厘米 ) 南部

6 1.3 Pollution characteristics and sediment conditions determine the flux is small (release of N and P in the sediments of Erhai) HCl-P(mg/kg) TN(g/kg) 巢湖巢湖巢湖巢湖 钙结合态磷 洞庭湖洞庭湖洞庭湖洞庭湖 洪泽湖洪泽湖洪泽湖洪泽湖 太湖太湖太湖太湖 东湖东湖东湖东湖 TP(mg/kg) 洱海洱海洱海洱海 N a O H -P (m g /k g ) δ 13 C/ 残渣磷 巢湖洞庭湖洪泽湖太湖东湖洱海 Ca-P (Calcium binding phosphorus and R-P (residual phosphorus ) content is high (50%- 60%), is one of the causes of water quality in Erhai good δ 15 N/ 含量 (m g/g) Nutrition levels increased faster, aquatic vegetation increase, organic matter and N, P of sediment from main source of submerged macrophytes 1970s Submerged vegetation degeneration, algal biomass increased significantly, organic matter and N, P of sediment derived from algae increased 1990s 结晶态铝有机络合态铝无定形铝 巢湖洞庭湖洪泽湖太湖东湖洱海 含量 (m g/g) 结晶态铁有机络合态铁无定形铁 巢湖洞庭湖洪泽湖太湖东湖洱海 Distribution of iron, aluminum, manganese and phosphorus is same, and P mainly related with the amorphous iron and aluminum content

7 1. Overview of Lake Erhai ecological environment 1.4 Severe degradation of aquatic plants The single dominant community appear ( in those years ) The coverage was about 20-40% in the 1970s to 1990s 2003 due to the deterioration of water quality, the coverage is only 10%, to about 5% in 2009 (up to now) 覆盖率 (%) 45% 40% 35% 30% 25% 20% 15% 10% 5% 0% 70 年代 The aquatic plants coverage of Lake Erhai from 1970s to 2009

8 1. Overview of Lake Erhai ecological environment 1.5 The dominant phytoplankton Cyanophyta, density increased in recent years to keep 10 7 / high value rise Part of the lake(lake Bay)sometime occur water bloom x10 4 cells/l 微束鱼腥藻 Year

9 1. Overview of Lake Erhai ecological environment 1.5 The dominant phytoplankton Cyanophyta, density increased in recent years to keep 10 7 / high value rise Part of the lake(lake Bay)sometime occur water bloom x10 4 cells/l 年 2009 年 微束鱼腥藻 Year

10 1.6 Benthic animal also presents the characteristics of eutrophication, the dominant species by clean succession for eutrophication common species, aquatic insects and Oligochaeta increased 北部 密度 (ind./m2) 寡毛类 水生昆虫软体动物寡毛类 软体动物 中部 北部 中部 南部 河蚬 螺蛳苏氏尾鳃蚓 水丝蚓 摇蚊萝卜螺 南部 Clean species changed into the polluted species

11 1. Overview of Lake Erhai ecological environment 1.6 The ecosystem degradation of Lake Erhai is moderate, which is the key time to prevent degradation Oligotrophic early stage of eutrophication eutrophication Grass clearly water Grass-algae coexistence Algae Turbid water Nutrition increased + foreign driving (water) Aquatic plant degradation + phytoplankton growth Grass Algae Decline of ecosystem stability Fish structure change largely

12 1.7 Realization of Erhai Lake ecosystem (improving the habitat is the premise of ecological restoration) Aquatic plant fish pollution sediment Overlying water phytoplankton Restoration of aquatic plants (submerged) (water quality improvement,) The fish structure regulation, restore native fish, adjustment of food chain structure, algal control algal bloom Emergency treatment Water quality is generally good (Ⅱ- Ⅲ), but the ecological system has undergone great changes, control loading, restoration of aquatic vegetation, fish ecology regulation (optimization adjustment of fishery structure), improving habitat is the key measures of ecosystem restoration of Lake Erhai

13 Outline 2 Analysis of Lake Erhai aquatic plant degradation 鄱阳湖主要生态环境问题

14 Community structure of the submerged vegetation of Lake Erhai is simplification and serious degradation. The central platform disappeared, lake bay area shrinking. The plots of submerged vegetation area is about 8Km 金鱼藻 + 微齿眼子菜金鱼藻 + 微齿眼子菜 + 光叶眼子菜 微齿眼子菜 马来眼子菜 + 牛叶眼子菜 6 微齿眼子菜 year ago 2006 year Distribution of submerged vegetation 6 in Lake Erhai 4 苦草

15 2. Analysis of Lake Erhai aquatic plant degradation 2.1 Light compensation depth of Lake Erhai was reduced near The aquatic plants in central platform was disappeared by weak light stress.

16 2. Analysis of Lake Erhai aquatic plant degradation 2.2 Reason of aquatic plants degradation-relationship between aquatic plants and light compensation depth (depth) 现场试验区 bio ma ss 生物量 (g FW/m 2 ) Increas 海潮湾 biomass Water level Water level 0 6 月 7 月 8 月 9 月 10 月 11 月时间

17 2. Analysis of Lake Erhai aquatic plant degradation 2.3 Degradation reason-the distribution of submerged macrophytes in Lake Erhai was decided by light intensity vertical distribution Different depth of water pots experiment 相对生长率 RGR(d-1) 光照百分比 (%) y = x R 2 = light compensation depth 水深 (m) y = 100e -0.66x y = 100e -1.47x y = 100e x 9 月 3.1m 12 月 5.0m 3 月 6.9m 10 光补偿点 月 9 月 12 月 水深 ( 米 ) The water level is higher in spring, the weak light, delaying the submerged vegetation recovery; summer low transparency is insufficient to inhibit the growth and distribution of Submerged Macrophytes

18 Seed bank-other way of aquatic plant restoration?

19 Seed bank-other way of aquatic plant restoration? 轮藻 Ⅰ 调查区域 Ⅱ Ⅲ submerged plant seed bank in Erhai 黑藻 Seed germination experiment 金鱼藻 黄丝草菱马来眼子菜 The platform of seed bank species Erhai seed bank species 2.4 The current condition is not suitable for the restoration of 共有 10 科 15 属 19 种严格意义上的水生植物 12 种, 其余 7 种为湿生平均密度为 : 颗 / m Most seeds buried deeper Anaerobic Seed bank is 年environment,re not suitable duce the seed as a major vigour means of 失Plant debris aquatic plant hinder seed recovery 7 germination 密度 ( 粒 / 平方米 ) 西岸湖心东岸湖湖心平台植被消失北部中部南部

20 3. Focused question How to realize the Lake Erhai ecological system-very special? TSIm Water quality (Ⅱ-Ⅲ Class) Algae Aquatic plants fish et al Oligotrophication Mestrophication Eutrophication Heavily Early stage of eutrophication Mestrophication: Water quality Ⅱ to Ⅲ Eutrophication: N, P high in sediment/ from Algae, aquatic pant; Fish et al.,

21 What is the problem? 1. Algal bloom Risk prediction and bloom control In Lake Erhai (or Yun-gui plateau lakes, regional problem?) Biomass of algae in Erhai Lake, 2009 Lake distribution in Yun-gui plateau

22 What is the problem? 2. How to control the release of N and P from sediment? Dredge, cover, ecological restoration by aquatic plant, chemic fixation, or other? Nitrogen Nitrogen Content and distribution of N and P in Lake Dianchi and Erhai sediments

23 What is the problem from the point of watershed? 3. Watershed pollution control and ecological restoration the level of the watershed is the level of water quality (1) How to planning land in lakeside? (2) How to cleaning Low pollution water in lakeside? Lake Erhai (3) How to protecting biological diversity?

24 What is national strategy from the point of Economy? Lake Erhai Lake Dianchi Polluted lake Good water quality that is the national strategy. This is the very important adjustment of our national lake protection strategy. The fact is that this work was promoted by our research, about 300 lakes with good water quality will be protected in the future ten years. What is the new national strategy? The lake with good water quality should be protected preferentially. The lake with good water quality should be paid more attention by government.

25 Thank you for your attention! Lake ecological restoration is our dream? Nature Lake is our dream!