Living within dynamic social-ecological freshwater systems: System parameters and the role of ecological engineering

The objective of ecological engineering is to design sustainable ecosystems that integrate human communities and their natural environment for the benefit of both. In this paper, we illustrate how social-ecological modeling can be used as a tool to clarify this objective at a landscape scale for freshwater systems. Coupled social-ecological systems (SESs) are open, dynamic systems subject to both ecological and socioeconomic perturbations. Here we demonstrate the interactive effects of social and technological uncertainties on SES dynamics over time. Additionally, we integrate research on ecosystem stability, social-ecological modeling, and ecological engineering to offer guidance for research at the human-environment interface. Based on a case study of Lake Erie's Sandusky watershed, we use an integrated human-biophysical model to investigate the influence of two parameters on SES dynamics: (1) regional societal preferences that impact watershed management and (2) technological innovation that alters agricultural nutrient efficiency. Our results illustrate ways in which SES dynamics and optimum management strategies depend on societal preferences within the region, indicating a key area of uncertainty for future investigation. As guidance for SES restoration, our model results also illustrate the conditions under which technological change that increases nutrient efficiency on farms can and cannot create a win-win, or increase both human welfare and SES resistance to eutrophication simultaneously. Using these results, we elucidate the value of ecological engineering and offer guidance for assessments of ecological engineering projects using social-ecological modeling.     

Simulation study on water quality based on sediment release flume experiment in Lake Taihu, China

Sediments have a significant influence on the overlying water, and nutrient release from sediments is an important source for lake eutrophication, particularly in shallow lakes. Sediment resuspension is primarily driven by wind-induced currents. In this research, the correlation between release rate of suspended sediment and flow velocity was studied, and an experiment on hydrodynamic forces was conducted in a rectangle flume using water and sediments collected from three sites in Lake Taihu, a eutrophic lake in China. It was shown that the starting velocities of sediment in Lake Taihu at three different incipient standards gained from the experiment were 15, 30, and 40 cm s⁻¹ and the release rate of suspended sediment could reach up to 643.4, 5377.1, and 13980.5 g m⁻² d⁻¹, respectively. Based on the experiment, a water quantity and quality numerical model of wind-induced current with sediment pollution for Lake Taihu was developed. The model was calibrated and validated by applying it to the study of the water quality of Lake Taihu. The calculated values were generally in good agreement with field observations, which indicated that the developed model could represent the dynamics of sediment resuspension to a certain extent. This study provides a new approach and a practical tool for planning and management policy and operations to protect the water quality and ecosystems of shallow lakes.     

Structure and dynamics of the periphytic algae of Jinyang Lake in Shanxi Province, North China

The structure and dynamics of periphytic algae in Jinyang Lake, the largest man-made lake in Taiyuan, Shanxi, have been studied by examining the periphytic algae samples collected from four sampling stations, during March 2006 to February 2007. In total, 227 species of periphytic algae (including varieties), belonging to three divisions, 27 families, 62 genera, have been identified. Diatoms were the dominant periphytic algae group. Taken the Shannon–Weaver, Margalef and Simpson diversity index together, it showed obvious temporal and spatial dynamics among different seasons and different sampling stations. The highest periphytic community structure evenness appeared at sampling station I in spring, summer and autumn, while at sampling station III in winter. The average biomass of periphytic algae varied from seasons. Our data showed that major factors affecting the periphytic algae in Jinyang Lake was water temperature, nutrient levels as well as human activities. In addition, the main effect caused by thermal power plant has been discussed.     

基于物元模型的鄱阳湖生态经济区土地生态安全评价

基于2001-2007年的相关数据,借助物元模型对鄱阳湖生态经济区的土地生态安全状况进行研究.结果表明:2001年鄱阳湖生态经济区土地生态安全状况为较安全状态,2002—2004年处于临界安全状态,2005年下降为不安全状态,2006年后土地生态安全状况有所好转,处于临界安全状态.表明利用物元模型进行区域土地生态安全评价是可行的,具有计算简便、意义明确、评价精度高等优点,为土地生态安全评价提供了另一种途径.     

白洋淀轮虫多样性及群落结构的初步研究

于2006年12月、2007年3～5月调查了白洋淀9个采样点的轮虫种类组成、数量及优势种,并对轮虫群落的多样性指数和群落相似性系数进行了测算,综合评价了白洋淀水质及富营养化状况.本次共发现轮虫41种,平均丰度为607～5024 ind./L,优势种为蒲达臂尾轮虫Brachionus budapesllensis、长肢多肢轮虫Polyarthra doli-choptera、角突臂尾轮虫B.angularis、矩形龟甲轮虫Keratella quadrata等,均为耐污性种类,各样点轮虫群落具较高相似性.从轮虫群落Margalef多样性指数看,白洋淀水质属中度污染和严重污染状况.     

巢湖夏、秋季浮游植物叶绿素a及蓝藻水华影响因素分析

2007年6-11月份,对设置在巢湖全湖的23个样点水体的理化指标水温(WT)、pH值、溶解氧(DO)、总氮(TN)、总磷(TP)、活性磷(RP)以及浮游植物的种类组成和叶绿素a(Chl-a)浓度进行了调查分析。结果表明:在巢湖夏秋季温差变化不大的环境中,温度依然是影响藻类生物量的重要因素。夏、秋季蓝藻为最主要的藻类类群(其平均值占藻类总生物量的63.36%);藻类生物量与所测理化因子均有显著正相关。在夏、秋季各月份,蓝藻生物量呈前高后低状M型波动,其中7月份湖水中蓝藻浓度最低。夏、秋季湖水中叶绿素的浓度没有太大变化,维持在一个较高的水平(>10mg/m3),遇到合适的气象条件有形成大面积水华的可能。     

The presence of atrazine and atrazine-degrading bacteria in the residential, cattle farming, forested and golf course regions of Lake Oconee

Aims: To assess the concentration of atrazine in Lake Oconee and develop a qPCR assay as a potential marker for the presence of atrazine‐degrading bacteria indicating atrazine contamination. Methods and Results: Water and sediment samples were collected from the Oconee Lake at four golf course sites, two residential sites, one cattle farming site and a forested site. Atrazine concentration at the study sites was determined using an ELISA kit and indicated the presence of atrazine from 0·72 ppb at the forested sites to 1·84 ppb at the golf course sites. QPCR results indicate the presence of atzA gene (atrazine chlorohydrolase) from 1·51 × 10² gene copies at the residential sites to 3·31 × 10⁵ gene copies per 100 ml of water at the golf course regions of the lake and correlated (r = 0·64) with atrazine concentration. Sediment samples had higher atzA gene copies compared with the water samples (P < 0·05). Conclusions: Atrazine concentration and the highest quantity of atzA gene were detected in the golf course regions of the lake. Overall, atrazine concentration monitored in Lake Oconee was below the Environment Protection Agency (EPA) regulatory standards. Significance and Impact of the Study: Quantitative PCR is an efficient technique for assessing the presence of atrazine catabolism gene as a functional marker for atrazine‐degrading bacteria and the presence of atrazine contamination.     

Reed die-back in southern Europe? A case study from Central Italy

Common reed die-back is a widely investigated phenomenon in Central Europe, not frequently recorded in S-European areas and almost unknown in the Mediterranean Basin. Symptoms of reed decline recently observed in the Italian Peninsula provided the starting point for a detailed investigation on a reed population in one of the largest freshwater ecosystems in Central Italy. The analyses were conducted over two vegetative seasons in 19 plots at seven locations. A set of 13 morphologic and phenologic reed traits were screened, monitored and statistically analysed. The data indicated the presence of the reed die-back syndrome in a wet Mediterranean ecosystem and enabled us to highlight a set of usable traits to detect the condition of decline. Among them, the stem height and diameter, the number of nodes, the relative growth rate and the lateral root diameter resulted the most significant factors highlighting the declining condition. Some environmental characteristics of the reed stands were also taken into account. The period of submersion and the presence of standing litter emerged as important features of the stands, strictly related to the degree of decline in the population. The results draw attention to the risk, in southern Europe too, of the loss of an ecosystem which plays an important role in biodiversity conservation.     

IDENTIFICATION OF A PSYCHROPHILIC GREEN ALGA FROM LAKE BONNEY ANTARCTICA: CHLAMYDOMONAS RAUDENSIS ETTL. (UWO 241) CHLOROPHYCEAE1

An unusual psychrophilic green alga was isolated from the deepest portion of the photic zone (<0.1% of incident PAR) at a depth of 17 m in the permanently ice‐covered lake, Lake Bonney, Antarctica. Here we identify and report the first detailed morphological and molecular examination of this Antarctic green alga, which we refer to as strain UWO 241. To determine the taxonomic identity, UWO 241 was examined using LM and TEM and partial sequences of the small subunit (SSU), internal transcribed spacer (ITS) 1 and ITS2 regions (including the 5.8S) of the ribosomal operon. These data were compared with those of previously described taxa. We identified UWO 241 as a strain of Chlamydomonas raudensis Ettl (SAG 49.72). Chlamydomonas raudensis is closely related to C. noctigama Korshikov (UTEX 2289) as well as foraminifer symbionts such as C. hedleyi Lee, Crockett, Hagen et Stone (ATCC 50216). In addition, its morphology, pigment complement, and phototactic response to temperature are reported. Chlamydomonas raudensis (UWO 241) contains relatively high levels of lutein and low chl a/b ratios (1.6±0.15), and the phototactic response was temperature dependent. The Antarctic isolate (UWO 241) included the typical photosynthetic pigments found in all chl a/b containing green algae. It possesses a small eyespot and, interestingly, was positively phototactic only at higher nonpermissive growth temperatures. Comparison of SSU and ITS rDNA sequences confirms the identification of the strain UWO 241 as C. raudensis Ettl and contradicts the previous designation as C. subcaudata Wille.     

A new species and geographical variation in the Telmatochromis temporalis complex (Teleostei, Cichlidae) from Lake Tanganyika

Telmatochromis brachygnathus sp.n. is described from the southern and central parts of Lake Tanganyika. It can be distinguished from the similar T. temporalis mainly by its smaller mouth. Morphological distinct populations were found in both species.