Winter limnology on the Great Lakes: The role of the U.S. Coast Guard

We describe a unique educational collaboration between the U.S. Coast Guard and Bowling Green State University with the goal of engaging Coast Guard crew members in a monitoring program intended to increase both temporal and spatial resolutions of sampling during winter in Lake Erie, a period where extreme weather conditions and safety considerations challenge our ability to sample.     

Characteristics of double-crested cormorant colonies in the U.S. Great Lakes island landscape

The Great Lakes form the largest freshwater island system in the world and provide breeding habitat for a large proportion of the continental population of double-crested cormorants (Phalacrocorax auritus). Here, cormorants have a high profile due to conflicts with humans; by 2007, most active (64%) breeding sites in U.S. waters were managed. This study used data from the U.S. Great Lakes Colonial Waterbird Database and The Nature Conservancy's Great Lakes Island GIS database to identify important features of breeding sites in the U.S. Great Lakes and broaden understanding of cormorant presence at the island-landscape scale. Islands 0.5–10 ha were used more frequently than expected, and most sites had remoteness values of ≤ 3 km. Colony size was positively correlated with years occupied and large colonies (> 1000 pairs) developed primarily (95%) on island sites > 1.0 ha. Sites supporting large colonies were more remote than those supporting smaller colonies. Presence of other colonial waterbird species, especially Herring Gulls (Larus argentatus), also characterized cormorant sites. Islands used by cormorants comprised a small proportion (n = 90, 3%) of the U.S. Great Lakes island resource, and < 1% of the total island area. Certain characteristics of breeding sites (e.g., small islands, proximity to mainland) may increase negative attitudes about cormorants. To understand cormorant impacts to island resources (e.g., vegetation; other colonial waterbird species), we suggest cormorant presence in the Great Lakes be considered in the broader context of island science, conservation and known threats, and at a landscape scale.     

A review of U.S. Army Corps of Engineers airborne coastal mapping in the Great Lakes

The U.S. Army Corps of Engineers (USACE) Joint Airborne Lidar Bathymetry Technical Center of Expertise (JALBTCX) collected its first airborne coastal mapping data on the Great Lakes in 1995. Since then, the JALBTCX has collected nearly 5 billion elevation and depth measurements and created over 2000 geographic information system (GIS) products for the shorelines of the Great Lakes. With improvements in airborne coastal mapping technology and the introduction of regional management for the USACE, surveys expanded into the regional scale, multi-sensor National Coastal Mapping Program (NCMP). The NCMP was initiated in 2004 to produce recurrent, regional, high-resolution light detection and ranging (lidar) elevation data and hyperspectral and aerial imagery to support regional sediment management, regulatory functions, flood damage reduction, asset management, emergency operations, and environmental stewardship. The JALBTCX is a collaboration among the USACE, the U.S. Naval Oceanographic Office (NAVOCEANO), and the National Oceanic and Atmospheric Administration (NOAA). The partners have worked together on airborne coastal mapping and charting since the late 1980s with the goal of advancing airborne lidar bathymetry and associated technologies. The collaboration has fielded three generations of airborne sensors and has transferred this technology to the commercial sector, supporting an expanding market for bathymetric lidar. The purpose of this paper is to provide an overview of the history of USACE survey efforts in the Great Lakes (1995–2012), an in-depth review of the resulting imagery and lidar data products, and new information product developments and applications to support environmental and coastal engineering throughout the Great Lakes region.     

Atmospheric flows of semi-volatile organic pollutants to the Great Lakes estimated by the United States' Integrated Atmospheric Deposition and Canada's Great Lakes Basin Monitoring and Surveillance Networks

We calculated the wet and dry deposition, vapor absorption, and volatilization flows (in kg/yr) of seven polychlorinated biphenyls (PCBs), nine organochlorine pesticides, and two polycyclic aromatic hydrocarbons (PAHs) into and out of the Great Lakes during 2010–2015 (inclusive). Particle, vapor, and precipitation concentrations from five rural and remote stations (one site on each lake) and two urban sites, operated by the United States and Canada, were used for the flow calculations. Output from the water to the air was the most important process for PCBs, chlordanes, and p,p′-DDE. The flows of endosulfan, p,p′-DDT, and phenanthrene were dominated by vapor absorption from the air to the water. The flow of benzo[a]pyrene was controlled by wet and dry deposition to the water. The flows of the hexachlorocyclohexanes (HCHs) into and out of the lakes were about equal, indicating air-water equilibrium for these compounds. Among the lakes, Lakes Superior and Erie had the highest input and output flows. The input and output flows for the five lakes were decreasing with halving times of 1–10 years and 10–40 years, respectively. Most chemicals had seasonal variations in their flows, with maximum inputs in the summer and maximum outputs in the fall. The flows of PCBs and PAHs into Lakes Michigan and Erie were associated with Chicago and Cleveland, respectively. Combining our data with previous data over the period 1992–2015, we estimated that the input flows of most of these chemicals have significantly decreased, but the output flows do not show consistent trends.     

Relative importance of macrophyte community versus water quality variables for predicting fish assemblages in coastal wetlands of the Laurentian Great Lakes

Fish have been shown to be sensitive indicators of environmental quality in Great Lakes coastal wetlands. Fish composition also reflects aquatic macrophyte communities, which provide them with critical habitat. Although investigators have shown that the relationship between water quality and fish community structure can be used to indicate wetland health, we speculate that this relationship is a result of the stronger, more direct relationship between water quality and macrophytes, together with the ensuing interconnection between macrophyte and fish assemblages. In this study, we use data collected from 115 Great Lakes coastal marshes to test the hypothesis that plants are better predictors of fish species composition than is water quality. First we use canonical correspondence analysis (CCA) to conduct an ordination of the fish community constrained by water quality parameters. We then use co-correspondence analysis (COCA) to conduct a direct ordination of the fish community with the plant community data. By comparing the statistic ‘percent fit,’ which refers to the cumulative percentage variance of the species data, we show that plants are consistently better predictors of the fish community than are water quality variables in three separate trials: all wetlands in the Great Lakes basin (whole: 21.2% vs 14.0%; n = 60), all wetlands in Lakes Huron and Superior (Upper: 20.3% vs 18.8%; n =  32), and all wetlands in Georgian Bay and the North Channel (Georgian Bay: 18% vs 17%; n =  70). This is the largest study to directly examine plant–fish interactions in wetlands of the Great Lakes basin.     

A pound of prevention,plus a pound of cure: Early detection and eradication of invasive species in the Laurentian Great Lakes

Ballast water regulations implemented in the early 1990s appear not to have slowed the rate of new aquatic invasive species (AIS) establishment in the Great Lakes. With more invasive species on the horizon, we examine the question of whether eradication of AIS is a viable management strategy for the Laurentian Great Lakes, and what a coordinated AIS early detection and eradication program would entail. In-lake monitoring would be conducted to assess the effectiveness of regulations aimed at stopping new AIS, and to maximize the likelihood of early detection of new invaders. Monitoring would be focused on detecting the most probable invaders, the most invasion-prone habitats, and the species most conducive to eradication. When a new non-native species is discovered, an eradication assessment would be conducted and used to guide the management response. In light of high uncertainty, management decisions must be robust to a range of impact and control scenarios. Though prevention should continue to be the cornerstone of management efforts, we believe that a coordinated early detection and eradication program is warranted if the Great Lakes management community and stakeholders are serious about reducing undesired impacts stemming from new AIS in the Great Lakes. Development of such a program is an opportunity for the Laurentian Great Lakes resource management community to demonstrate global leadership in invasive species management.     

Predicting the response of Hamilton Harbour to the nutrient loading reductions: A modeling analysis of the “ecological unknowns”

We examine the likelihood of delisting the Hamilton Harbour as an Area of Concern, if the nutrient loading reductions proposed by the Remedial Action Plan are actually implemented. Our analysis suggests that the chl a criterion of 10 μg L^{− 1} is achievable, but the water quality setting process should explicitly accommodate the natural variability by allowing for a realistic percentage of violations, e.g., exceedences of less than 10–15% of the weekly samples during the stratified period should still be considered as compliance of the system. The current epilimnetic total phosphorus criterion of 17 μg L^{− 1} is probably stringent and therefore a somewhat higher value (e.g., 20 μg L^{− 1}) may provide a more realistic goal. Phosphorus dynamics in the sediment–water column interface need to be revisited, as the internal nutrient loading can conceivably be a regulatory factor of the duration of the transient phase and the recovery resilience of the Harbour. We also pinpoint two critical aspects of the system dynamics that invite further investigation and will likely determine our predictive capacity to assess compliance with the chlorophyll a criterion of 10 μg L^{− 1}, i.e., the nutrient recycling mediated by the microbial food web and the structural shifts towards a zooplankton community dominated by large-sized and fast-growing herbivores. The latter prospect highlights the notion that the bottom-up (i.e., nutrient loading reduction) approach historically followed in the Harbour was sufficient to bring the system in its present state, but any further improvements should be viewed in the context of a combined bottom-up and top-down (i.e., alleviation of the zooplanktivorous pressure) control.     

Tributary phosphorus monitoring in the U.S. portion of the Laurentian Great Lake Basin: Drivers and challenges

This paper examines the tributary monitoring network currently in place for sampling the amount of phosphorus entering the U.S. Great Lakes, focusing on the challenges faced by the agencies and organizations responsible for maintaining the network. The tributaries that are monitored vary in terms of flow, the size and terrain of the watershed being drained, and patterns of land use. Data generated by this network are used by researchers to compute lake-wide phosphorus loads. In this work, the primary drivers and challenges associated with operating an effective phosphorus tributary monitoring program were investigated through interviews with stakeholders responsible for managing a portion of the existing network. Based on these interviews, the authors identify three recommendations that policy makers interested in maintaining an effective phosphorus monitoring network in the Great Lakes should consider. The first is to provide states with incentives to support the long-term monitoring that is required to estimate phosphorus loads in tributaries to the Great Lakes; currently, most states design their programs to meet the requirements of the Clean Water Act, which results in patterns of sampling that are not necessarily useful for computing loads. The second recommendation is to facilitate the creation of a monitoring protocol that generates enough samples to identify trends and quantify loads at a level of certainty necessary for use in statistical models and load control programs. Finally, funding mechanisms capable of supporting long-term monitoring programs need to be established, with programs in Michigan and Minnesota serving as potential models.     

A historical perspective on the “fish tumors or other deformities” beneficial use impairment at Great Lakes Areas of Concern

The Great Lakes Water Quality Agreement defines Areas of Concern as geographic areas that fail to meet the general or specific objectives of the agreement where such failure has caused or is likely to cause impairment of beneficial use of the area's ability to support aquatic life. One of the beneficial use impairments, fish tumors or other deformities, is defined by the International Joint Commission to occur when the incidence rate of fish tumors and other deformities exceeds rates at unimpacted or control sites, or when survey data confirm the presence of neoplastic or preneoplastic liver tumors in bullhead or suckers. Brown bullhead, a benthic species with a limited home range, have frequently been used as indicator species in U.S. Areas of Concern. While there is strong field evidence for an association between PAH exposure and hepatic neoplasia in brown bullhead, laboratory investigations would strengthen the association. There is less evidence linking specific classes of chemicals in the environment to orocutaneous neoplasia in brown bullhead. Studies on orocutaneous neoplasia of brown bullhead should focus on assessing the presence or absence of viruses and on epidermal exposure to specific chemicals and chemical mixtures. Lastly, the effects of covariates such as length, age, and gender on the prevalence of liver and skin neoplasms should be investigated. This paper reviews the state of science on the fish tumors or other deformities beneficial use impairment. Subsequent papers address specific issues related to this impairment and provide recommendations for standardized criteria.     

A Comment on the Paper by John r. M. Kelso and Gary s. Milburn: “Entrainment and Impingement of Fish by Power Plants in the Great Lakes Which Use the Once-Through Cooling Process” (J. Great Lakes Res. 5:182-194, 1979)

Assessment of entrainment and impingement impact of the 89 steam-electric generating stations on Great Lakes fish stocks reported by Kelso and Milburn (1979) is evaluated. Despite the large number of fish impinged at these stations, impingement losses typically constituted less than 1% of the standing stocks of fish in the lakes. Similarly, entrainment losses also represented a small fraction of total larvae in the lakes. Therefore, power plants alone probably have minimal impact on the Great Lakes sport and commercial fisheries and no detectable impact on fish populations. Despite Kelso and Milburn's assertion to the contrary, future fish losses from proposed generating capacity expansion may be less, due to improvements in cooling water intake design.     

Assessing the impacts of stream regulation in the flathead river Basin,Montana, U.S.A. I. Simulation modelling of system water balance

A Fortran-based simulation model was written to predict water movement into and out of Flathead Lake. Since tributaries, the lake proper and downstream flows were either freeflowing or regulated by hydroelectric dams, it was necessary for the model to adjust simulated, regulated flows to account for predicted natural flows. Empirical input to the model consisted of daily discharge data or statistical summaries of data sets for an 80+ year period of record for gauging sites on major tributaries, the lake and its outlet river. The model produces graphical output of empirical observations or simulates lake levels and riverine flows on the basis of any selected period of the record. The model was successfully used to evaluate the feasibility of various water management scenarios to enhance or protect fish and wildlife and also permit various hydropower production quotas.     

Highlights of Drought Policy and Related Science in Australia and the U.S.A.

Abstract

Patterns of water supply and use in Australia and the U.S.A. differ in many ways. This results in different perceptions concerning the nature of drought and policy approaches to its management. This paper discusses the differences and similarities and explores lessons that policy makers in both countries can learn from one another. A key difference between the two countries is that whereas drought is perceived in Australia essentially in terms of its impact on agriculture, in the U.S. both perceptions and policy are also heavily influenced by the impact of drought on urban communities. This has led to different policy emphases. In 1992 Australia established its National Drought Policy; the U.S. is presently considering the adoption of a national drought policy. These policies highlight drought being accepted as part of natural climate variability, rather than as a natural disaster. They also emphasize the protection of the natural resource base.     

Validation of a diatom-based index of water quality confirms its utility in monitoring of the Lake Erie's nearshore area

We conducted a validation of the Planktonic Diatom Index (PDI) to demonstrate the utility of a water quality index for the monitoring of Lake Erie's nearshore pelagial zone. Using a large, independent dataset from the Western and Central Basins of Lake Erie for validation ensures realistic assessment of the performance of the index. Diatom-based biomonitoring allows for the inference of integrative information about water quality based on diatom species composition. The PDI is based on the assumption that phosphorus, an established proxy for eutrophication, is instrumental in the structuring of diatom communities. In this study, PDI scores and measured total phosphorus were significantly correlated (r²?=?0.34, r²?=?0.63 outliers removed). However, when samples were considered on a basin-wide basis, the PDI scores were not significantly predicted by measured total phosphorus in the Western Basin. We suggest that snapshot phosphorus measurements are less likely to represent the overall condition in the highly variable, eutrophic Western Basin. When multiple phosphorus measurements were averaged over time, the relationship with the integrative PDI scores was more apparent (r²?=?0.52). Through validation with an independent dataset, we show that the PDI is likely a monitoring tool that provides a robust assessment of water quality in the pelagial zone of the nearshore waters in Lake Erie.     

Benthic macroinvertebrate communities in nonregulated and regulated waters of the clearwater river,Idaho, U.S.A.

Benthic macroinvertebrates were examined over a two-year period in nonregulated, regulated, and semiregulated reaches of the Clearwater River in northern Idaho. Macroinvertebrate communities in the nonregulated reach above Dworshak Reservoir were taxonomically diverse at all stations. In contrast, the macroinvertebrate community in the regulated reach of the North Fork of the Clearwater River (NFCR) was severely altered with high macroinvertebrate abundance and low taxa richness (2 to 8 taxa). Orthoclad chironomids dominated this reach composing between 68 and 99 per cent of total benthic invertebrate numbers. The mayfly Ephemerella infrequens was the only other macroinvertebrate to be abundant in the regulated reach. The major factors contributing to the simplified macroinvertebrate community are reduced habitat diversity, fluctuating water levels, altered thermal regime, and possibly an altered food supply. The effects of the dam were mitigated in the semiregulated Mainstem of the Clearwater River (MSCR) due to the merger of a nonregulated fork entering 2.5 km downstream from the dam. The macroinvertebrate community in the semiregulated MSCR was more complex than the regulated reach with a community structure resembling that found above the reservoir.     

Q3与Q14黄土地基承载力确定的新方法及应用评价

为了评价基础尺寸效应对黄土地基承载力确定的影响,基于黄土地基载荷试验和地基承载力确定新方法,并对比分析了以往规范中地基承载力表存在的偏离问题,提出了适当的修正建议.研究表明:在大部分情况下,计算值与规范承载力表中的黄土地基承载力值是相符的,但在液限同孔隙比的比值较小时,规范承载力值趋于偏大,应将其适当调小;而当液限同孔隙比的比值较大时,规范承载力值趋于偏小,应将其适当调大.     

Discontinuity of trichopteran (caddisfly) communities in regulated waters of the clearwater river,Idaho, U.S.A.

Riverine trichopteran (caddisfly) communities were sampled seasonally at eight locations over a two-year period to determine if a multiple-level release hydroelectric dam created a faunal discontinuity along the longitudinal profile of the Clearwater River in northern Idaho. The confluence of a non-regulated river with a regulated reach provided an unusual opportunity to examine the recovery of community parameters in a semi-regulated river. A marked discontinuity in the caddisfly community occurred in the regulated reach immediately below the dam, reflected by greatly reduced diversity and abundance values, and by shifts in functional relationships. These faunal changes are primarily attributable to the modified temperature, discharge, and food resources induced by river regulation. The non-regulated river exerted a major mitigative effect on the trichopteran fauna below its confluence with the regulated reach, despite maintenance of semi-regulated conditions. Trichopteran community parameters approached near normal levels concomitant with partial reductions in flow fluctuations, and partial recovery of temperature and food resources. In addition, the non-regulated river provided an important colonization pathway for riverine species to enter the semi-regulated lower reaches.     

Effects of stream and lake regulation on reproductive success of kokanee in the flathead river system,Montana, U.S.A

Kokanee (Oncorhynchus nerka) provided an important recreational fishery in the Flathead River-Lake system (Columbia River Basin, U.S.A.-Canada) until the late 1970s when populations declined dramatically. The declines coincided with peaking river discharge from Hungry Horse Dam during the autumn spawning period and an increase in the duration of lake drawdown caused by the operation of Kerr Dam on the outlet of Flathead Lake. Redds of both river and lakeshore spawners were, therefore, dewatered in winter, causing high freezing and desiccation mortality of eggs during the incubation period. It appeared that growth rates of kokanee were density dependent. Female kokanee from strong year classes (i.e., those produced during years of favourable water levels and flow conditions during the incubation period) were smaller than those from weak year classes when unfavourable conditions for incubation prevailed. A highly significant relationship (r² = 0.929, p < 0.001) was demonstrated between female kokanee spawner length, river gauge heights, and lake levels during years which produced each year class. The close fit of the relationship was further validated by the strong correlation (r = 0.964) between actual kokanee lengths and predicted lengths. Other factors which could have influenced kokanee year class strength include hatchery plants of kokanee fry, harvest of kokanee by anglers, variations in the carrying capacity of Flathead Lake, and natural fluctuations in egg and fry mortality.