How long-term water level changes influence the spatial distribution of fish and other functional groups in a large shallow lake

We numerically explored the effects of long-term water level changes on biotic biomass and spatial distribution of fish in a large shallow lake. We calibrated Ecospace model (Ecopath with Ecosim modelling suite) with data from various functional groups (ranging from phytoplankton to piscivorous fish), and considered 14 different habitats. Two scenarios representing, respectively, a long-term water-level increase and decrease by 1 m were constructed and run for a period of thirty eight years (1979–2016). The results showed a very uneven spatial distribution of fish biomass in the lake, with the highest concentration in the southern basin. The 1 m decrease scenario caused a diminution in the biomass of all groups but piscivorous fish. The 1 m increase scenario saw a weak decrease in most species biomass. Consequently, in both scenarios, long-term water level changes would be generally detrimental to the lake biota. In the context of more frequent climate-induced hydrological fluctuations, we encourage the use of these simulations as effective tools for future prediction and assessment of ecosystem-based fisheries management and ecological status maintenance of shallow lakes.     

净水厂生物活性炭池无脊椎动物群落结构研究

调查了南方某净水厂生物活性炭(BAC)池中无脊椎动物的群落结构周年变化.共发现无脊椎动物26种(属或类).轮虫为优势类群,其次为桡足类及其无节幼体、枝角类、寡毛类.调查期间BAC池炭总管水中无脊椎动物的平均丰度是主臭氧后水的8.2倍,炭滤后水中无脊椎动物的平均丰度是炭滤前水的12～18.7倍.研究结果表明,BAC池是无脊椎动物滋生的重要场所.春夏两季BAC池中无脊椎动物增长较快,水温升高对BAC池中无脊椎动物滋生起促进作用.夏季和其他时期分别以桡足类和轮虫占据优势,存在着小型无脊椎动物(轮虫)向大型无脊椎动物(桡足类)演替的现象.     

Spatiotemporal trends of polychlorinated biphenyls (PCBs) in surface and suspended sediments from the Lake Ontario Canadian nearshore 1994–2018: A fish consumption advisory perspective

Spatiotemporal trends for polychlorinated biphenyls (PCBs) were examined in surface and suspended sediments collected between 1994 and 2018 from over twenty nearshore stations on the Canadian side of Lake Ontario and the St. Lawrence River. In 2018, PCB concentrations ranged over an order-of-magnitude in surface (<10 ng/g?357 ng/g) and suspended sediments (<10 ng/g–330 ng/g), illustrating the presence of legacy hotspots as well as diffuse urban inputs. PCB concentrations in both surface and suspended sediments were consistently highest in Hamilton Harbour, but were also elevated at other stations around the perimeter of the Niagara basin as well as near Trenton and Kingston, Ontario. Generally, higher PCB concentrations were found in surface sediment relative to paired suspended sediment samples suggesting temporal improvements in nearshore sediment quality. However, many stations demonstrated temporal variability in PCB concentrations, a likely factor in the lack of an overall nearshore declining trend. Given that PCBs are listed as a consumption-limiting contaminant for all fish sampling blocks in the Canadian waters of Lake Ontario and are responsible for 78% of restricted advisories, sediment quality benchmarks that account for bioaccumulation potential should be considered over toxicologically-derived guidelines to gauge severity of PCB contamination of nearshore sediments. Relatively higher TOC-normalized PCB concentrations in the western end of Lake Ontario suggests additional research on PCB bioavailability from nearshore sediment would be beneficial in understanding basinwide trends of PCBs in fish, and that an adaptive approach to sediment management may be needed in the context of consumption advisories.     

The last snapshot of natural pelagic fish assemblage in Lake Turkana,Kenya: A hydroacoustic study

A hydroacoustic survey and supplementary gillnet investigation were carried out in the open water of the central part of Lake Turkana in September 2009. Overall acoustic fish density and biomass were assessed as 1381 ind./ha and 30 kg/ha, respectively. The fish density estimate was lower than the results from two previous investigations in the 1970s and 1980s (long-term average 3739 ind./ha), but the biomass remained relatively unchanged (long-term average 25.4 kg/ha). A decreasing gradient in pelagic fish density from the western to eastern shore of the lake was observed. Fish were distributed unevenly within the water column. During the day, a majority of fish aggregated in the mid-water layers (10–12 m below the water surface), creating on echograms the so-called Midwater Scattering Layer. This feature dissipated completely during dusk and the majority of fish occurred in the surface layers at night. These diel vertical fish migrations influenced day and night hydroacoustic estimates of the total fish abundance. Synodontis spp., Lates spp. and Schilbe uranoscopus dominated the catch of both mid-water and bottom gillnets installed in open water areas. Hydrocynus forskalii and Brycinus spp. contributed significantly to the catch of mid-water gillnets while Bagrus bayad and the endemic Haplochromis macconneli occurred only in the catch of the bottom gillnets.     

Hydrodynamics in an expanded bed of large size ion‐exchange resin,and natural product adsorption

Successful applications of expanded bed adsorption (EBA) technology have been widely reported in the literature for protein purification. Little has been reported on the recovery of natural products and active components of Chinese herbal preparations using EBA technology. In this study, the hydrodynamic behavior in an expanded bed of cation resin, 001 × 7 Styrene‐DVB, was investigated. Ephedrine hydrochloride (EH) was used as a model natural product to test the dynamic binding capacity (DBC) in the expanded bed. EBA of EH directly from a feedstock containing powdered herbs has also been investigated. These particles are different from commercially available expanded bed adsorbents by virtue of their large size (205 to 1030 µm). When the adsorbent bed is expanded to approximately 1.3 to 1.5 times its settled bed height, the axial liquid‐phase dispersion coefficient was found to be of the order 10^?5 m² s^?1, which falls into the range 1.0 × 10^?6 to 1.0 × 10^?5 m² s^?1 observed previously in protein purification. Because of the favorable column efficiency (low axial dispersion coefficient), the recovery yield and purification factor values of EH directly from a feedstock reached 86.5% and 18, respectively. The results suggest that EBA technology holds promise for the recovery of natural products and active components of Chinese herbal preparations. Copyright © 2007 Society of Chemical Industry     

Towards a methodology for mapping ‘regions for sustainability’ using PPGIS

There is debate about the problems of communication between scientists, planners and stakeholder, and the scale at which environmental planning should take place. A review of the literature reveals that the concept of holistic landscape ecology is gaining ground in the scientific community. It also becomes clear that participation by stakeholders is not only important in satisfying the requirements of Agenda 21 but also of ensuring cooperation by local inhabitants in the final plan. Moreover, participation is becoming accepted as a vehicle for the planners to gain access to local knowledge, which is a vital complement to scientific knowledge. The challenge is to create a methodology that will overcome the shortfalls currently encountered and allow participants to be proactive in their definition of their landscape. This is possible by extending the experiments in public participation geographical information systems so long as care is taken to overcome problems in public unfamiliarity with the technology. The purpose of this paper is to draw together research in the fields of landscape ecology and planning to enable the formulation of a methodology for achieving greater and more proactive input in participation. The methodology proposed is currently actionable and this paper also points to the potential for a new emphasis in research.     

基于遥感技术的海岸带资源环境管理

海岸带是人口密集、资源丰富、开发程度较高,但生态环境又往往相对脆弱的地区。随着我国沿海地区经济高速发展,海岸带区域的环境状况发生了显著变化。这些变化信息依靠常规的调查手段难以及时获取,而卫星遥感技术则能够为监测海岸带及毗连海域资源环境变化提供有效手段。如何利用多源、多通道、多时相、主被动融合的星载遥感数据获取海岸带及毗连海域资源环境信息是我们亟需了解的问题。分别从海洋渔业资源调查、珊瑚礁及红树林等海岸生物资源的遥感、海洋水质监测、赤潮的监测与预警、溢油和海冰的监测等方面论述了遥感技术的特点与优势。并对遥感技术在海岸带资源环境管理中的应用做了展望。     

Relationship between nutrient loading and phytoplankton standing crop in outdoor experimental ponds with continuous flow systems

The relationship between nutrient loading and phytoplankton standing crop was studied in outdoor experimental ponds during a period from autumn 1978 to winter 1979. Throughout the experimental period, phosphate, nitrate and ammonium at 3.5, 7.0 and 10.6 mg m⁻² d⁻¹ of phosphorus, respectively were added continuously into three experimental ponds. Nitrogen loading was adjusted to about 7 times the phosphorus by weight. The apparent water residence time of each experimental pond was 20 days.The phytoplankton standing crop at steady state showed a high correlation to the nutrient loading. The relationship between phosphorus loading (P, mg m⁻² d⁻¹) and concentrations of chlorophyll-a (Chl-a, μg l⁻¹) in the experimental ponds could be expressed by the following formula; (Chl-a) = 18.1 (P) − 57 (n = 14, r = 0.90).The relationship between total phosphorus and chlorophyll-a concentrations in the experimental ponds varied in each season. The slopes of the regression lines were greatest in autumn, and smallest in summer.     

Fungal community dynamics associated with harmful cyanobacterial blooms in two Great Lakes

Harmful algal blooms (HABs) impose major costs on aquatic ecosystems worldwide, including the Laurentian Great Lakes. Microbial consumers, including fungi, can have important interactions with bloom-forming algae and cyanobacteria, although relatively few studies have investigated the relationship between fungi and HABs. We examined changes in the aquatic fungal community coincident with the occurrence of large cyanobacterial blooms in two areas of the Great Lakes (western Lake Erie and Saginaw Bay, Lake Huron). We collected water samples over the course of bloom development, peak, and decline from 3 sites in western Lake Erie on 11 dates and 2 sites in Saginaw Bay on 4 dates. Single molecule sequencing (PacBio RS II) with two molecular markers (the internal transcribed spacer (ITS) of the rRNA locus using fungal-specific primers and the 18S rRNA with primers targeting early-diverging lineages of fungi) was used to estimate fungal community composition. Results indicate a diverse fungal community within the lakes, including several major fungal phyla. The Chytridiomycota were particularly well-represented (54.8% and 45.4% of ITS and 18S sequences, respectively), and we also found representation from both Cryptomycota and Aphelidiomycota, which are putatively obligate intracellular parasites. Further, we found associations between the fungal community (alpha diversity; community composition) and measures of bloom magnitude (chlorophyll a, phycocyanin, and microcystin concentrations) in western Lake Erie. Our results suggest potentially important spatial and temporal heterogeneity in the fungal community that motivates further research on functional importance of fungi in the Great Lakes and consequences for HABs and freshwater ecosystems more broadly.     

PeakTrace: Routing of hydropeaking waves using multiple hydrographs—A novel approach

Hydropeaking is known for its adverse impacts on river ecosystems. However, the implementation of mitigation measures is still largely pending due to conflicting priorities of ecology and economics, which require scenario building to assess trade-offs. Therefore, widely applicable and standardized tools are needed to analyze hydropeaking hydrology in affected rivers to expedite mitigation efforts. Here, we present a novel empirical approach—PeakTrace—that can (a) detect and follow source-specific hydropeaking waves in the downstream direction by using multiple hydrographs and (b) describe how to flow metrics of hydropeaking waves change along a river's course. In detail, PeakTrace first identifies associated flow events and then models translation and retention processes between neighboring hydrographs. Finally, the models can be combined to establish a non-linear hydropower plant-specific model. We demonstrate the PeakTrace method's usability in 16 Austrian case studies. The results underline the high performance of PeakTrace, describing the longitudinal development of flow metrics with high model accuracy up to 25 km or more. Ecologically-relevant metrics, such as rate of change or amplitude, decrease with distance from the hydropower outlet regarding down-ramping events; the same pattern can be observed for up-ramping events too, except for the rate of change for which an intensity increase may be observed, probably due to slope and the roughness difference between base flow and peak flow. Overall, this paper underlines the usability of PeakTrace as a basis to assess hydropower plant-specific hydro-ecological impacts and evaluate hydropeaking mitigation measures, especially by incorporating critical flow thresholds of river biota and life stages.