Exotic species in Lake Champlain

The Lake Champlain basin contains substantially fewer exotic species (N = 48) than the Great Lakes (N > 180), in part due to its isolation from commercial traffic. Exotic species have been introduced by authorized and unauthorized stocking, bait buckets, use of ornamental plants, and through the Champlain and Chambly canals that link the lake to the Hudson River, Mohawk River, Erie Canal, and the Great Lakes. Several species, such as water chestnut and zebra mussels, have had severe ecological, economic, and nuisance effects. The rate of appearance of new species increased in the 1990s, potentially as a result of increasing activity in the basin, improved water quality in the Champlain Canal, and increased sampling. Efforts to slow the introduction of new species have focused on public education and legislation to reduce bait bucket introductions and quarantine undesirable plants; however, the major remaining vector for introductions is the Champlain Canal. An estimated 20 species have entered the lake via canals, of which at least 12 used the Champlain Canal, and numerous species in the connected drainage systems could still enter via this route; some are already in the Erie Canal. Most recently (2008), the Asian clam was discovered two locks below Lake Champlain. The Lake Champlain canals also function as a conduit for exotic species exchange between the Hudson River, St. Lawrence River, and Great Lakes. The potential for future introductions could be reduced by a biological barrier on the Champlain Canal, and additional emphasis on public education.     

Relative abundance,age structure,and body size in mudpuppy populations in southwestern Ontario

Little is known of mudpuppy (Necturus maculosus) population structure and ecology; some populations in the Great Lakes are thought to be in decline. Mudpuppies are the obligate hosts for the mudpuppy mussel (Simpsonaias ambigua), a species that is endangered in Canada and in many Great Lakes states. We surveyed mudpuppies from the Sydenham River, the only known Canadian locality of the mudpuppy mussel, in order to generate information on relative density, deformity rates and population age/size structure and used this information to compare them to known mudpuppy populations from Great Lakes sites in the Detroit River, Lake St. Clair and Long Point in Lake Erie. Deformity rates were elevated at some sites in the Sydenham River. The relative density of mudpuppies in the Sydenham River was lower than that of other Great Lakes sites and their age was skewed towards younger individuals. Although at lower densities than at other Great Lakes sites, the mudpuppy population in the Sydenham River appears stable and is showing signs of recruitment which bodes well for the future of the mudpuppy mussel population of the river.     

Interactive effects of abiotic,hydrological and anthropogenic factors on fish abundance and distribution in natural run‐of‐the‐river shallow lakes

Ecological processes in lowland rivers are mostly dominated by hydrology and its interactions with other environmental factors. Fish–habitat relationships in rivers are also influenced by human impacts. In this study, we describe patterns of abundance and distribution of fish species in a group of natural lowland river lakes along spatial anthropogenic and abiotic gradients when four hydrologically different summers are compared. We also describe the proportion of the total variances in fish species abundances that can be accounted for by selected abiotic (water conductivity), hydrological (water residence time) and human activity‐derived (total phosphorus (TP) concentration and NO₃:NH₄) variables. Consequently, our main purpose is to explore how abiotic and anthropogenic factors interact to affect fish abundance and distribution together with consistent results across different hydrological conditions. We conclude with a briefly discussion of some management implications. The anthropogenic impacts on water quality, the extreme hydrological variability and the fluctuating abiotic environment affected fish abundance and distribution. Pampa inland silverside Odontesthes bonariensis was benefited from a less human disturbed environment with higher water residence time and total salinity, whereas species as Cyphocharax voga, Parapimelodus valenciennis and Cyprinus carpio found these conditions largely disadvantageous. On the other hand, while most species showed stronger—either negative or positive—response to anthropogenic, hydrological or abiotic factors Oligosarcus jenynsii was only slightly affected. This paper identified the ecological function of a lowland river under its natural flow regime. There are not many opportunities to study unmodified rivers worldwide. Therefore, our findings may help in assessment programmes of fish communities in flow altered and human disturbed aquatic ecosystems. Copyright © 2008 John Wiley & Sons, Ltd.     

Patterns in the crustacean zooplankton community in Lake Winnipeg,Manitoba: Response to long-term environmental change

Changes in the crustacean zooplankton community composition and abundance in Lake Winnipeg (1969–2006) provide a rare opportunity to examine their response to environmental changes in the largest naturally eutrophic lake on the Canadian prairies. Since 1929, zooplankton species composition in Lake Winnipeg has changed little except for the addition of the invasive cladoceran, Eubosmina coregoni in 1994. The dominant taxa in the lake in summer include: Leptodiaptomus ashlandi, Acanthocyclops vernalis, Diacyclops thomasi, Daphnia retrocurva, Daphnia mendotae, Diaphanosoma birgei, Eubosmina coregoni, and Bosmina longirostris. Climate-accelerated nutrient loading to southern Lake Winnipeg over the last two decades has led to increased phytoplankton abundance and higher frequency of cyanobacterial blooms especially in its northern basin. Crustacean zooplankton have likewise increased especially in the North Basin, but less so in the more nutrient rich South Basin, possibly as a consequence of higher densities of pelagic planktivorous fish and light-limited primary production compared with the more transparent North basin (Brunskill et al., 1979, 1980). Calanoid copepods play a larger role in the South basin food web in contrast to cyclopoid copepods and Cladocera in the North basin. The study begins to fill the recognized gap in understanding of Lake Winnipeg's food web structure and provides a baseline for evaluating ongoing changes in the zooplankton community with the arrival of new non-indigenous taxa, e.g. Bythotrephes longimanus and Dreissena polymorpha. It reinforces previous work demonstrating that zooplankton provide valuable indices toward evaluating the health of an ecosystem.     

浅水湖泊水生态数学模型研究及应用

该文针对珠三角感潮浅水湖泊水环境模拟问题,在二维水流-污染物输移耦合数学模型基础上,结合WASP(water quality analysis simulation program)水生态数学模型原理,考虑溶解氧、氨氮、硝酸盐氮、有机氮、无机磷、有机磷、碳生化需氧量和叶绿素a等8个水质变量及其相互作用的溶解氧平衡子系统、氮循环子系统、磷循环子系统和浮游植物动力学子系统,建立了浅水湖泊水生态数学模型。通过室内实验系统模拟了珠三角某典型感潮人工湖泊外江来水营养条件对蓝藻生长的影响,确定了蓝藻生长速率等关键模型参数,并模拟了湖泊不同换水方案下叶绿素a的时空分布规律,为控制湖泊水体富营养化、预防蓝藻水华爆发提供科学依据。     

近40年来中国西北内陆5个典型湖泊面积变化遥感分析

在全球气候变暖的背景下,研究中国西北内陆地区湖泊的面积变化不仅对水资源管理和可持续发展战略有着重要意义,也为评价气候变化与人类活动对湖泊的影响提供参考。以中国西北内陆区5个典型湖泊为研究对象,利用1970-2015年的Landsat MSS/TM/ETM+/OLI影像数据,利用归一化差异水体指数(Normalized Difference Water Index,NDWI)和改进型归一化差异水体指数(Modified Normalized Difference Water Index,MNDWI)分别提取5个典型湖泊边界并获取湖泊面积,同时利用5个典型湖泊周边的气象站降雨量、蒸发量等气象数据,尝试分析湖泊面积发生变化的原因。结果表明:红碱淖近30年来面积呈减小趋势,入湖河流拦蓄和煤炭地下开采等是导致面积减少的原因;博斯腾湖近40年来的面积呈先增加后减少的趋势,其面积变化主要受地表径流和积雪融水的影响;呼伦湖近40年来面积呈减少的趋势,其面积变化主要受入湖径流量的影响;贝尔湖近30年来呈相对稳定的趋势,其面积变化主要入湖径流量的影响;青海湖近40年来面积呈现先减小后增大的趋势,其面积变化主要受区域降水和入湖径流量的影响。     

Using bald eagles to indicate the health of the Great Lakes' environment

The bald eagle (Haliaeetus leucocephalus) is one of the most studied birds of North America, and a great amount of natural life‐history information, including the response of various stressors on the eagles' ability to reproduce, are well known. In Michigan, the eagle has been chosen to track the trends of bioaccumulative compounds of concern across watersheds in the state. The state has been divided into major watersheds, and 20% of these are surveyed each year. A control area in northern Minnesota, Voyageurs National Park, is also sampled annually. We report here on the methods used, the preliminary results of the 1999 field season, and how differences in mercury concentrations varied over a 10‐year period. Mercury in feathers of nestling eagles declined over time only in Lakes Michigan and Huron, but have not decreased among other subpopulations in Michigan. Concentrations of polychlorinated biphenyls (PCBs) and 4,4′‐DDE in blood plasma from nestling eagles have declined over time for most subpopulations; however, they remain greater for breeding areas associated with the Great Lakes' food web. Sea eagles of the genus Haliaeetus are a good sentinel species to track trends in bioaccumulative compounds in aquatic systems.     

Great Lakes' contaminants reduce sperm production and fertilizing ability in mice

The long‐term effects of Great Lakes' contaminants on male reproductive performance resulting from lactational and dietary exposure were investigated. Female C57BL/6 J mice (F‐0) were mated with DBA/2 J male mice to produce B₆D₂‐F₁ offspring. Dams (F‐0) were fed one of three treatment diets during lactation. The three treatment diets were: (i) diet C, containing lab chow and fish oil; (ii) diet I, containing 60% Iowa carp and 40% lab chow; and (iii) diet G, containing 60% Great Lakes' carp and 40% lab chow. Diet C served as a lab‐chow control treatment, while diet I served as a fish‐diet control treatment. Diet G contained 2500 µg of polychlorinated biphenyls (PCBs) and 300 µg of 1,1‐dichloro‐2,2‐bis‐[p‐chlorophenyl]ethylene (4,4′‐DDE) per kilogram of feed. The offspring (F‐1) were continued on their respective maternal treatment diets from weaning until termination. Greater neonatal mortality and lesser body weights were observed in the F‐1 male mice on diet G. Lesser fecundity was observed in one‐year‐old F‐1 male mice on diet G following pairing with non‐treated female mice. The sperm concentration of F‐1 male mice on diet G was less than 30% of that of mice on diets C and I. The in vitro fertilizing ability of the sperm decreased to 10% of that of mice on the two control diets. Sperm motility, velocity, linearity and amplitude of lateral head (ALH) displacement were also decreased in 15‐month‐old F‐1 male mice on diet G.