Are Pulp and Paper Mills Sources of Toxaphene to Lake Superior and Northern Lake Michigan?

Toxaphene was a broad-spectrum pesticide consisting of a mixture of highly chlorinated bornanes and bornenes. After its ban in 1982, toxaphene concentrations have shown a general decline in the environment as a whole and in most of the Great Lakes specifically. Recent work, however, shows that toxaphene concentrations are not decreasing in fishes from Lake Superior and northern Lake Michigan. Non-atmospheric, relatively localized sources are a possible explanation for these observations. For example, toxaphene could be inadvertently produced and released by pulp and paper mills, which could be synthesizing toxaphene-like compounds as a byproduct of bleached paper production. Reported here is a study of surficial river sediment collected upstream and downstream from seven pulp and paper mills, from five areas of previous toxaphene use, and from two presumed pristine locations. Concentrations of toxaphene found downstream are similar to those found upstream from each of the pulp and paper mills. Concentrations in sediment from rivers near previous toxaphene use locations were higher than concentrations in the background samples. These data suggest that pulp and paper mills are not now sources of toxaphene but that toxaphene used as a pesticide in the Great Lakes basin (although these uses were very small compared to its use in the southern US) could be a potential source.     

Analysis of Hydrologic Property of Poyang Lake

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Landscape-scale modeling of water quality in Lake Superior and Lake Michigan watersheds: How useful are forest-based indicators?

The Great Lakes watersheds have an important influence on the water quality of the nearshore environment, therefore, watershed characteristics can be used to predict what will be observed in the streams. We used novel landscape information describing the forest cover change, along with forest census data and established land cover data to predict total phosphorus and turbidity in Great Lakes streams. In Lake Superior, we modeled increased phosphorus as a function of the increase in the proportion of persisting forest, forest disturbed during 2000–2009, and agricultural land, and we modeled increased turbidity as a function of the increase in the proportion of persisting forest, forest disturbed during 2000–2009, agricultural land, and urban land. In Lake Michigan, we modeled increased phosphorus as a function of ecoregion, decrease in the proportion of forest disturbed during 1984–1999 and watershed storage, and increase in the proportion of urban land, and we modeled increased turbidity as a function of ecoregion, increase in the proportion of forest disturbed during 2000–2009, and decrease in the proportion softwood forest. We used these relationships to identify priority areas for restoration in the Lake Superior basin in the southwestern watersheds, and in west central and southwest watersheds of the Lake Michigan basin. We then used the models to estimate water quality in watersheds without observed instream data to prioritize those areas for management. Prioritizing watersheds will aid effective management of the Great Lakes watershed and result in efficient use of restoration funds, which will lead to improved nearshore water quality.     

The Sustainable Utilization of Lake Resources in the Middle and Lower Reaches of Yangtze River

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Fleet Dynamics of the Commercial Lake Trout Fishery in Michigan Waters of Lake Superior during 1929–1961

Understanding fishing fleet dynamics is important when using fishery dependent data to infer the status of fish stocks. We analyzed data from mandatory catch reports from the commercial lake trout (Salvelinus namaycush) fishery in Michigan waters of Lake Superior during 1929–1961, a period when lake trout populations collapsed through the combined effects of overfishing and sea lamprey (Petromyzon marinus) predation. The number of full-time fishermen increased during 1933–1943 and then decreased during 1943–1957. Addition of new fishermen was related to past yield, market prices, World War II draft exemptions, and lost fishing opportunities in Lake Huron and Lake Michigan. Loss of existing fishermen was related to declining lake trout density. Large mesh (≥ 114-mm stretch-measure) gill net effort increased during 1929–1951 because fishermen fished more net inshore as lake trout density declined, even though catch per effort (CPE) was often higher in deeper waters. The most common gill net mesh size increased from 114-mm to 120-mm stretch-measure during 1929–1957, as lake trout growth increased. More effort was fished inshore than offshore and the amount of inshore effort was less variable over time than offshore effort. Relatively stable yield was maintained by increasing gill net effort and by moving some effort to better grounds. Because fishing-up caused yield and CPE to remain high despite declining lake trout abundance, caution must be used when basing goals for lake trout restoration on historical fishery indices.     

The use of NDVI and its Derivatives for Monitoring Lake Victoria’s Water Level and Drought Conditions

Normalized Difference Vegetation Index (NDVI), which is a measure of vegetation vigour, and lake water levels respond variably to precipitation and its deficiency. For a given lake catchment, NDVI may have the ability to depict localized natural variability in water levels in response to weather patterns. This information may be used to decipher natural from unnatural variations of a given lake’s surface. This study evaluates the potential of using NDVI and its associated derivatives (VCI (vegetation condition index), SVI (standardised vegetation index), AINDVI (annually integrated NDVI), green vegetation function (F _g ), and NDVIA (NDVI anomaly)) to depict Lake Victoria’s water levels. Thirty years of monthly mean water levels and a portion of the Global Inventory Modelling and Mapping Studies (GIMMS) AVHRR (Advanced Very High Resolution Radiometer) NDVI datasets were used. Their aggregate data structures and temporal co-variabilities were analysed using GIS/spatial analysis tools. Locally, NDVI was found to be more sensitive to drought (i.e., responded more strongly to reduced precipitation) than to water levels. It showed a good ability to depict water levels one-month in advance, especially in moderate to low precipitation years. SVI and SWL (standardized water levels) used in association with AINDVI and AMWLA (annual mean water levels anomaly) readily identified high precipitation years, which are also when NDVI has a low ability to depict water levels. NDVI also appears to be able to highlight unnatural variations in water levels. We propose an iterative approach for the better use of NDVI, which may be useful in developing an early warning mechanisms for the management of lake Victoria and other Lakes with similar characteristics.     

Validation of MSWEP daily and extreme precipitation of the Taihu Lake Basin in Jiangsu ProvinceEI北大核心CSCD

基于1979—2019年江苏省太湖流域雨量站实测降水资料,综合解析了全球性降水资料MSWEP(multi-source weighted-ensemble precipitation)对日降水量和各历时极值降水量的表征能力。结果表明:MSWEP对研究区日降水量总体上有较强的解释能力,但在山丘区较集中的湖西区和以水域为主的太湖区两个水利分区的精度相对较差,同时MSWEP难以捕捉到暴雨等级的日降水事件;MSWEP可大致反映研究区各历时极值降水量的空间分布格局,但在细节特征上与地面降水场仍有一定差异;随着历时增加,MSWEP极值降水量的精度不断提高,MSWEP对15 d及更长历时极值降水量具有较强的定量表征能力;MSWEP日降水量和极值降水量的误差与降水强度之间均有显著的线性负相关性,存在较明显的“低值高估、高值低估”现象,且MSWEP的精度与空间尺度有关;在研究区面平均尺度上,由于降水量的空间均化效应和尺度不匹配性的消除,MSWEP对日降水量和极值降水量的表征能力明显优于栅格尺度。     

Results of the collaborative Lake Ontario bloater restoration stocking and assessment, 2012–2020

Bloater, Coregonus hoyi, are deepwater planktivores native to the Laurentian Great Lakes and Lake Nipigon. Interpretations of commercial fishery time series suggest they were common in Lake Ontario through the early 1900s but by the 1950s were no longer captured by commercial fishers. Annual bottom trawl surveys that began in 1978 and sampled extensively across putative bloater habitat only yielded one individual (1983), suggesting that the species had been locally extirpated. In 2012, a multiagency restoration program stocked bloater into Lake Ontario from gametes collected in Lake Michigan. From 2012 to 2020, 1,028,191 bloater were stocked into Lake Ontario. Bottom trawl surveys first detected stocked fish in 2015, and through 2020 ten bloater have been caught (total length mean = 129 mm, s.d. = 44 mm, range: 96–240 mm). Hatchery applied marks and genetic analyses confirmed the species identification and identified stocking location for some individuals. Trawl capture locations and acoustic telemetry suggested that stocked fish dispersed throughout the main lake within months or sooner, and the depth distribution of recaptured bloater was similar to historic distributions in Lake Ontario and other Great Lakes. Predicted bloater trawl catches, based on modeled population abundance and trawl survey efficiency, were similar to observed catches, suggesting that post-stocking survival is less than 20% and contemporary bottom trawl surveys can quantify bloater abundance at low densities and track restoration.     

Trends of PCB concentrations in Lake Michigan coho and chinook salmon, 1975–2010

The manufacture and use of polychlorinated biphenyls (PCBs) was banned in the United States in 1977 after it was determined that these compounds adversely affect animals and humans. The Wisconsin Department of Natural Resources has quantified total PCB concentrations in Lake Michigan chinook (n = 765) and coho (n = 393) salmon (Oncorhynchus tshawytscha and Oncorhynchus kisutch, respectively) filets since 1975. We analyzed these data to estimate trends in PCB concentrations in these fish (1975–2010). We used generalized linear models with a gamma error distribution and log link fit to the untransformed concentrations. Trend patterns were examined using graphical smoothing and generalized additive models. We identified a candidate set of models that included time trend and other predictor variables. Using the Akaike Information Criterion to select among models we found the best models for both species included piecewise linear time trends, total body length, % lipid, and collection season as predictor variables. The intersection of the two trends was 1985 for chinook salmon and 1984 for coho salmon. PCB concentrations in both species increased with body length and % lipid, and were higher for individuals caught in the fall. Our data reveals a dramatic decline in PCB concentrations of − 16.7% and − 23.9% per year for chinook and coho, respectively, up until the intersection year likely reflecting implementation of restrictions on Aroclor-based PCBs. After the intersection year to 2010, PCB concentrations declined at an annual rate of − 4.0% (95% CI: − 4.4% to − 3.6%) and − 2.6% (95% CI: − 3.3% to − 1.9%) for chinook and coho, respectively.     

Spatial and temporal variation in distribution of larval lake whitefish in eastern Lake Ontario: Signs of recovery?

The lake whitefish (Coregonus clupeaformis) is one of the native Lake Ontario fishes that declined severely over the past century. Recent evidence of larval lake whitefish production in a historic spawning area (Chaumont Bay) might signal a recovery of this species in New York waters. We surveyed coastal and open water areas to evaluate densities and estimate total abundance of larval lake whitefish in Chaumont Bay. Other historic spawning areas and embayments with appropriate spawning and nursery habitat were also surveyed, but only a few larvae were found outside of Chaumont Bay. Lake whitefish larvae were found in every embayment sampled within Chaumont Bay, with larval densities of nearly 600/1000 m² in some samples. Greatest abundances occurred in the northern sectors and near the mouth of the bay. Open water densities were generally less than half that of nearshore sites. The total bay-wide estimate for 2005 was approximately 644,000 lake whitefish larvae, but dropped to 230,000–400,000 in 2006 and 2007, respectively. Mean larval growth rates (0.36 mm/day) did not differ by year, but were consistently higher in early May than in late April. Lake whitefish production in Chaumont Bay is encouraging for this species, but the cause and persistence of the decline after 2005 can be determined only by continued monitoring. Other possible bottlenecks of survival may exist at juvenile and adult stages and could significantly affect recruitment dynamics. This species is sensitive to normal climatic fluctuations and increased variability associated with global climatic change could make winter nursery conditions unfavorable for this species.     

Lake Trout Spawning on Artificial Reefs and the Effect of Zebra Mussels: Fatal Attraction?

Lake trout stocked in the Great Lakes appear to spawn primarily on shallow reefs (< 16 m deep), particularly on breakwaters or water intake lines. Shallow water substrates are being rapidly colonized by zebra mussels, potentially resulting in degraded substrate and interstitial water quality. The attraction of spawning lake trout to new substrate and the effect of zebra mussels on spawning success was examined. Lake trout eggs and fry were collected on clean cobble and cobble fouled with zebra mussels at the Port of Indiana in southern Lake Michigan, and on each of three recently constructed submerged reefs. Egg deposition was similar among all sites except on new, unfouled cobble, where deposition was 11 to 29 times higher, depending on the collection device used. The ratio of empty egg chorions to intact eggs was similar among all sites except the fouled substrate, where the ratio was 129× higher (P < 0.001). Fry catches were similar on fouled and unfouled substrate, but 6.5 × higher on one of the new reefs (P < 0.01). In laboratory incubators, egg hatching rates were similar in cobble with and without zebra mussels. Lake trout were attracted to spawn on newly constructed artificial reefs, but the presence of zebra mussels appeared to reduce egg deposition and increase damage to eggs. Artificial reefs may successfully increase the amount of spawning substrate available for lake trout, but if they are constructed in shallow water they may not be productive areas for egg incubation and fry hatch due to the presence of zebra mussels, shallow-water egg and fry predators, and storm surge.     

Fifty Years of Physical Investigations and Related Limnological Studies on Lake Erie, 1928–1977

To set the scene for the papers which follow, this review presents the principal findings of hydrodynamic and related chemical and sedimentological studies in Lake Erie beginning with the 1928/29 cooperative surveys of the central and eastern basins (Fish 1929, 1960) and ending with the (also cooperative) “Project Hypo” (Burns and Ross 1972) and the papers assembled in the 1976 special number, “Lake Erie in the Early Seventies” (J. Fish. Res. Board Canada, Vol. 33). Attention is also drawn to the far-reaching and interweaving influence of the physical phenomena on biological and sedimentological processes operating in the lake. Where needed to place the half-century's findings in context or to lead into the papers which follow in this issue, some references to work published before 1928 or after 1977 are also included. After an introduction, the review examines: surface surges and seiches; thermal stratification and its coupling with the distribution of oxygen and phosphorus in bottom water; long-term and short-term circulation patterns; sedimentation and sediment transport.     

Water Balance of Zhangdu Lake in Yangtze River Basin

1 IntroductionIn the central Yangtze Basin in China ,there were thou-sands of large lakes .In the past , most of them were naturallyconnected with rivers ,such as the Yangtze ,but gradually losttheir hydrological and biological linkages due to both natura…     

Using 223Ra and 224Ra to estimate discharges of groundwater and associated nutrients into southeast of Qinghai Lake,in Qinghai–Tibet Plateau

With its important geographical location and status as the largest saltwater body in China, Qinghai Lake plays a vital role in the ecological environment of the northeastern part of the Qinghai-Tibet Plateau. Due to climate change and the subsequent adjustment of Qinghai Lake’s tourism policy, it is necessary to understand groundwater discharges in southeast of Qinghai lake both for ecological protection and risk prevention. This study used radium isotopes ²²³Ra and ²²⁴Ra to trace groundwater discharges and nutrients carried into the lake. The spatial characteristics of Ra isotopes with greater activity in the upper and bottom layers in the lake indicated that they were influenced by inputs of shallow groundwater and diffusion from sediments. The average ²²⁴Ra diffusion flux of the sediments in the Lake was 33.54 dpm m^?2 d^?1. Based on the ²²⁴Ra mass balance model, the discharge flux of shallow groundwater in this region was estimated to be 3.49 × 10⁶ ～ 3.68 × 10⁶ m³ d^?1. The PO₄^3? and SiO₂ fluxes carried into the southeastern of the lake by groundwater were 1.78 × 10¹¹ ～ 1.88 × 10¹¹ mg/y and 2.22 × 10¹² ～ 2.34 × 10¹² mg/y, respectively. It is thus essential to monitor shallow groundwater discharge into Qinghai Lake for the protection of the water environment and prevention of potential ecological risks.     

Large Lake Models—Uses,Abuses, and Future

Mathematical modeling has played and should continue to play an important role in Great Lakes management and scientific development. Great Lakes modeling is entering a phase of relative maturity in which expectations are more realistic than in the past. For example, it is now realized that the modeling process itself is valuable even if the resulting models are not immediately useful for management. The major thrust in the past has been water quality (eutrophication) modeling, but there has been a recent shift toward developing toxic substances models. Modelers and model users have been limited by a lack of knowledge of Great Lakes processes, limited data availability, and incomplete or improper validation. In the future, greater emphasis is needed on specifying prediction uncertainty and conducting proper model validation — including calibration, verification, and post-audits. Among the Great Lakes modeling activities likely to have the greatest payoff in the near future are (1) the development and refinement of toxic substances models, (2) post-auditing and improvement of eutrophication models, and (3) the adaption of models for use on personal computers to allow greater model utilization.     

Phytoplankton Composition and Biomass in the Offshore Waters of Lake Erie: Pre- and Post-Dreissena Introduction (1983–1993)

Phytoplankton was collected in all basins of Lake Erie during 42 cruises during the spring and summer from 1983 to 1993—a period that spans the Dreissena mussel invasion. Two potential impacts of Dreissena on the phytoplankton community of the western, central, and eastern basins of Lake Erie were evaluated: Was selective feeding occurring as observed in Saginaw Bay and were reductions in biomass evident in the offshore regions of the three basins of Lake Erie? In the western basin, significant summer decreases in Chlorophyta, Bacillariophyta, Cyanobacteria, and total phytoplankton biomass were observed after Dreissena introduction. Similarly in the spring, Bacillariophyta and total phytoplankton biomass and chlorophyll a concentrations decreased significantly. Since several divisions of phytoplankton did not decrease in phytoplankton biomass in the western basin, and spring Cyanobacteria biomass increased significantly while other divisions decreased in biomass, selective feeding on the phytoplankton community was suggested. Where significant reductions in biomass were observed in the offshore waters of the western basin, they were approximately 50% of the reduction observed at the nearshore sites in Lake Erie by other workers.Dreissena impact on the phytoplankton community of the pelagic waters of the central and eastern basin appeared to be minimal. Pre- and post-Dreissena total phytoplankton biomass and chlorophyll a concentrations were not significantly different or increased significantly after the Dreissena invasion. Biomass of several divisions of phytoplankton significantly increased after Dreissena introduction in the central and eastern basins. These included Bacillariophyta (central basin), Cyanobacteria (central and eastern basin), Chrysophyta (eastern basin), Chlorophyta biomass (eastern basin) and phytoplankton biomass (central basin) and chlorophyll a (central basin) in the spring, and Chrysophyta (eastern basin) and Cryptophyta biomass (central basin) in the summer. Generally, a reduction in phytoplankton biomass would be expected as a result of Dreissena grazing, not an increase in biomass. Dreissena-mediated changes in phytoplankton have generally occurred in shallow, well-mixed lakes, ponds, and embayments, not in deeper waters such as the central and eastern basins of Lake Erie.     

Temporal and spatial differences in deposition of organic matter and black carbon in Lake Michigan sediments over the period 1850–2010

Inorganic carbon (IC), total organic carbon (OC), and black carbon (BC) were analyzed in eight sediment cores obtained from deep water (>30 m) sediments in the Chippewa and south Chippewa basins, as well as Green Bay in Lake Michigan. These cores were segmented at high resolution and radio-dated to reconstruct a detailed history of deposition to the lake both spatially and temporally since ca. 1850 CE. To help interpret the depositional record, cores were also characterized for stable isotopes (¹³C and ¹⁵N), as well as particle size distribution, density, organic matter (OM), and other parameters. Fine (silt and clay) sediment particles contained OM of primarily lacustrine algal biomass origin. Sedimentation fluxes showed large increases in OM and OC fluxes through much of the lake during the onset of industrialization and the period of rapid industrialization to onset of Great Lakes environmental legislation. In contrast, fluxes and loading of BC increased dramatically in the southern basin until the 1930's, then decreased substantially after the 1940's. This observation was due largely to results from site M009 nearest the steel mills and industrial zones of Chicago and northern Indiana. Together, whole lake loadings of OM and BC provide evidence that changing industrial activity and legislation intended to curb air pollution in the Great Lakes region have had a fairly rapid and dramatic impact. In contrast, legislation intended to decrease eutrophication through reductions in nutrient loading to the lake have not had a similar impact on sedimentation of OM in the lake.     

Diet complexity of Lake Michigan salmonines: 2015–2016

In Lake Michigan, the unintended introduction of invasive species (e.g., zebra mussel, Dreissena polymorpha; quagga mussel, D. rostriformis bugensis; round goby, Neogobius melanostomus) and reduced nutrient loading has altered nutrient dynamics, system productivity, and community composition over the past two decades. These factors, together with sustained predation pressure, have contributed to declines of several forage fish species, including alewife (Alosa pseudoharengus), which has dominated diets of the five primary salmonine species of Lake Michigan for the last 50 years. Salmonines that have inflexible, less complex diets may struggle if alewife declines continue. We analyzed stomach contents of salmonines collected throughout the main basin of Lake Michigan in 2015 and 2016 to investigate diet composition, diet diversity, and individual variation of alewife lengths consumed. Chinook salmon (Oncorhynchus tshawytscha) almost exclusively consumed alewife and had lower diet diversities compared to the other four species, which consumed relatively high frequencies of round goby (brown trout, Salmo trutta; lake trout, Salvelinus namaycush), aquatic invertebrates (coho salmon, Oncorhynchus kisutch) and terrestrial invertebrates (rainbow trout, Oncorhynchus mykiss) along with alewife. Although clear spatio-temporal feeding patterns existed, much of the variation in diet composition and diet diversity was expressed at the individual level. Salmonine populations consumed the entire size range of alewife that were available, whereas individual stomachs tended to contain a narrow range of alewife sizes. Due to their reliance on alewife, it is likely that Chinook salmon will be more negatively impacted than other salmonine species if alewife abundance continues to decline in Lake Michigan.     

Abundance and distribution of benthic macroinvertebrates in offshore soft sediments in Western Lake Huron, 2001–2007

Invasive species have had major impacts on the Great Lakes. This is especially true of exotic dreissenid mussels which are associated with decreased abundance of native macroinvertebrates and changes in food availability for fish. Beginning in 2001, we added a benthic macroinvertebrate survey to the USGS-Great Lakes Science Center's annual fall prey fish assessment of Lake Huron to monitor abundance of macrobenthos. Mean abundance of Diporeia, the most abundant benthic taxon in Lake Huron reported by previous investigators, declined greatly between 2001 and 2007. Diporeia was virtually absent at 27-m sites by 2001, decreased and was lost completely from 46-m depths by 2006, but remained present at reduced densities at 73-m sites. Dreissenids in our samples were almost entirely quagga mussels Dreissena bugensis. Zebra mussels Dreissena polymorpha were virtually absent from our samples, suggesting that they were confined to nearshore areas shallower than we sampled. Loss of Diporeia at individual sites was associated with arrival of quagga mussels, even when mussel densities were low. Quagga mussel density peaked during 2002, then decreased thereafter. During the study quagga mussels became established at most 46-m sites, but remained rare at 73-m sites. Length frequency distributions suggest that initial widespread recruitment may have occurred during 2001–2002. Like other Great Lakes, Lake Huron quagga mussels were associated with decreased abundance of native taxa, but negative effects occurred even though dreissenid densities were much lower. Dreissenid effects may extend well into deep oligotrophic habitats of Lake Huron.     

Use of flow-normalization to evaluate nutrient concentration and flux changes in Lake Champlain tributaries, 1990–2009

The U.S. Geological Survey evaluated 20 years of total phosphorus (P) and total nitrogen (N) concentration data for 18 Lake Champlain tributaries using a new statistical method based on weighted regressions to estimate daily concentration and flux histories based on discharge, season, and trend as explanatory variables. The use of all the streamflow discharge values for a given date in the record, in a process called “flow-normalization”, removed the year-to-year variation due to streamflow and generated a smooth time series from which trends were calculated. This approach to data analysis can be of great value to evaluations of the success of restoration efforts because it filters out the large random fluctuations in the flux that are due to the temporal variability in streamflow. Results for the full 20 years of record showed a mixture of upward and downward trends for concentrations and yields of P and N. When the record was broken into two 10-year periods, for many tributaries, the more recent period showed a reversal in N from upward to downward trends and a similar reversal or reduction in magnitude of upward trends for P. Some measures of P and N concentrations and yields appear to be related to intensity of agricultural activities, point-source loads of P, or population density. Total flow-normalized P flux aggregated from the monitored tributaries showed a decrease of 30 metric tons per year from 1991 to 2009, which is about 15% of the targeted reduction established by the operational management plan for the Lake Champlain Basin.