Development and Evaluation of a New Predictive Model for Metamorphosis of Great Lakes Larval Sea Lamprey (Petromyzon marinus) Populations

Accurate forecasts of the number of larval sea lamprey (Petromyzon marinus) within a stream that will enter into metamorphosis are critical to currently used methods for allocating lampricide treatments among streams in the Great Lakes basin. To improve our ability to predict metamorphosis we used a mark-recapture technique, involving the marking of individual larval lamprey with sequentially coded wire tags, to combine information regarding individual and stream level parameters collected in year t, with direct observations of metamorphic outcome of lamprey recaptured in year t+1. We used these data to fit predictive models of metamorphosis. The best model demonstrated excellent predictive capabilities and highlighted the importance of weight, age, larval density, stream temperature and geographic location in determining when individual lamprey are likely to transform. While this model was informative, it required data whose measures are not practical to obtain routinely during the larval sea lamprey assessment program. A second model, limited to data inputs that can be easily obtained, was developed and included length of larvae the fall prior to metamorphosis, stream latitude and longitude, drainage area, average larval density in type-2 habitat, and stream lamprey production category (a measure of the regularity with which treatments are required). This model accurately predicted metamorphosis 20% more often than current models of metamorphosis; however, we recommend further validation on an independent set of streams before adoption by the Great Lakes Fishery Commission for ranking streams.     

Sedimentary in-filling of an urban Great Lakes waterfront embayment and implications for threshold-driven shoreline morphodynamics,Montrose Beach,SW Lake Michigan

This paper addresses subaqueous and subaerial patterns of geomorphic change across Montrose Beach, an urban embayment along Chicago’s engineered SW Lake Michigan coastline. Our goal was to better characterize the urban littoral zone, its sediment-transport processes, and associated shoreline morphodynamics (from the early 1950s to present). Succinct beach geomorphic responses to decadal base-level changes (i.e., regression during lake-level fall and transgression during lake-level rise) occurred once a morphologic threshold in the subaqueous portion of the system had been crossed. Despite continuous sand trapping, nearshore elevations were initially not conducive to promoting expansion of the subaerial beach environment, regardless of water-level condition. Rapid beach expansion after 1990 (by a factor of four in <25 years) was facilitated by prior decades of nearshore accretion. Shoreline morphodynamic trajectories and degree of coupling to nearshore sedimentary processes are important considerations for developing long-term beach-management strategies. Rapid cross-shore movements of the shoreline in response to oscillatory base levels are expected to persist at Montrose and other urban beaches of similar design (and nearshore conditions). This has important implications for managing urban lakefront ecosystems, including coastal dunes and shore-bird habitats. Few datasets have thus far quantified time-variant and threshold-driven patterns of beach geomorphic development along engineered coastlines. Such insights should help coastal managers better understand littoral sediment interconnectivity across the urban lakefront and anticipate future geomorphic trajectories of beach environments with anticipated decadal-scale oscillatory patterns in lake level.     

Spatial and temporal trends in invertebrate communities of Great Lakes coastal wetlands,with emphasis on Saginaw Bay of Lake Huron

The shallow-sloping coastal bathymetry of Saginaw Bay (Lake Huron) supports broad fringing wetlands. Because benthic invertebrates form an important forage base for fish, wading birds, and waterfowl that utilize these habitats, understanding the drivers of invertebrate community structure has significant management implications. We used Great Lakes basin-wide data from 2002 to place Saginaw Bay wetland invertebrate communities and their environmental drivers into a basin-wide context. Various aspects of community structure were highly correlated with fetch and watershed agriculture across the basin. Saginaw Bay wetlands had relatively high fetch and watershed agriculture and supported unique invertebrate communities, typified by high abundances of many insect taxa. Wetlands from other regions around the basin tended to have more crustaceans and gastropods than the Saginaw Bay wetlands. A 1997–2012 time series from three representative Saginaw Bay wetlands revealed substantial shifts in community structure throughout the period, especially from 2001 through 2004. These years followed a 1-m decline in Lake Huron water levels that occurred between 1997 and 2000. Major community changes included decreasing insect abundance, especially chironomids, and increasing crustacean abundances, especially Hyalella azteca (Amphipoda). While factors in addition to water levels were likely also important, our time series analysis reveals the marked temporal dynamics of Saginaw Bay wetland invertebrate communities and suggests that water level decline may have influenced these communities substantially. Both the spatial and temporal community patterns that we found should be considered in future bio-assessments utilizing wetland invertebrates.     

Seasonal Patterns in Growth,Blood Consumption,and Effects on Hosts by Parasitic-Phase Sea Lampreys in the Great Lakes: An Individual-Based Model Approach

An individual-based model (IBM) was developed for sea lamprey (Petromyzon marinus) populations in the Laurentian Great Lakes. The IBM was then calibrated to observed growth, by season, for sea lampreys in northern Lake Huron under two different water temperature regimes: a regime experienced by Seneca-strain lake trout (Salvelinus namaycush) and a regime experienced by Marquettestrain lake trout. Modeling results indicated that seasonal blood consumption under the Seneca regime was very similar to that under the Marquette regime. Simulated mortality of lake trout directly due to blood removal by sea lampreys occurred at nearly twice the rate during August and September under the Marquette regime than under the Seneca regime. However, cumulative sea lamprey-induced mortality on lake trout over the entire duration of the sea lamprey's parasitic phase was only 7% higher for the Marquette regime compared with the Seneca regime. Thus, these modeling results indicated that the strain composition of the host (lake trout) population was not important in determining total number of lake trout deaths or total blood consumption attributable to the sea lamprey population, given the sea lamprey growth pattern. Regardless of water temperature regime, both blood consumption rate by sea lampreys and rate of sea lamprey-induced mortality on lake trout peaked in late October. Elevated blood consumption in late October appeared to be unrelated to changes in water temperature. The IBM approach should prove useful in optimizing control of sea lampreys in the Laurentian Great Lakes.     

Spatial patterns of rainbow smelt energetic condition in Lakes Huron and Erie in 2017: Evidence for Lake Huron resource limitation

Rainbow smelt (Osmerus mordax) is a key planktivore and prey fish in Lake Huron. Given the declining offshore productivity in the lake since the early 2000s, we described the energy content of rainbow smelt in 2017 across five different regions (North Channel, Georgian Bay, Saginaw Bay, northern main basin, southern main basin) where phytoplankton and zooplankton productivity likely varied. To increase contrast across the productivity gradient, rainbow smelt energy content was also estimated from western Lake Erie. Within the North Channel where large fish (≥90 mm, total length) were sampled most frequently, mean energy density (kJ/g wet weight) varied seasonally: 4.29 in April (month of spawning), 3.86 in June, 3.99 in July, and up to 4.35 in September. Energy density of rainbow smelt from higher productivity western Lake Erie was 37% (large fish ≥90 mm) to 60% higher (small fish <90 mm) than that of fish from Lake Huron. Within Lake Huron, energy density of rainbow smelt from North Channel was slightly higher than those from other regions; rainbow smelt from Georgian Bay generally had the lowest energy density. Across regions, including western Lake Erie, energy density increased with chlorophyll a concentration. Compared with Lake Huron studies prior to 2004, when oligotrophication had not yet accelerated, energy density of rainbow smelt in 2017 was up to 31% lower. The decline in rainbow smelt energy density is likely the result of declining primary and secondary pelagic production and increased resource limitation for planktivorous fish.     

Effects of Hydrological Flow Regime on Sediment-water Interface and Water Column Nitrogen Dynamics in a Great Lakes Coastal Wetland (Old Woman Creek,Lake Erie)

Sediment-water interface nitrogen (N) transformations and water column ammonium cycling rates were measured along a stream to lake gradient at three sites within Old Woman Creek (OWC) and one near-shore Lake Erie site during two hydrological regimes: one with open flow to the lake after a rain event (July 2003), and another with a sand barrier blocking flow (July 2004). Net N2 effluxes in OWC at all times and at the near-shore Lake Erie site in July 2003 suggest that sediments are a N sink via denitrification. Observed dissimilatory nitrate reduction to ammonium (DNRA) may counteract some of this N removal, particularly when the creek mouth is closed. Upstream, a closed creek mouth led to higher sediment oxygen demand, net N₂ flux, potential DNRA, and potential denitrification rates. The lake site exhibited lower rates of these processes with the creek mouth closed except denitrification potential, which was unchanged. Denitrification in OWC appeared to drive N limitation in the lower wetland when the sand barrier was blocking flow to the lake. Higher potential versus in situ denitrification estimates imply that water column NO₃⁻ limits and drives denitrification in OWC. Water column to sediment regeneration ratios suggest that sediment recycling may drive primary production in the OWC interior when the creek mouth is closed and new N inputs from runoff are absent, but more data are needed to confirm these apparent trends. Overall, hydrological regime in OWC appeared to have a greater impact on sediment N processes than on water column cycling.     

Distribution and abundance of freshwater polychaetes, Manayunkia speciosa (Polychaeta), in the Great Lakes with a 70-year case history for western Lake Erie

Manayunkia speciosa has been a taxonomic curiosity for 150 years with little interest until 1977 when it was identified as an intermediate host of a fish parasite (Ceratomyxa shasta) responsible for fish mortalities (e.g., chinook salmon). Manayunkia was first reported in the Great Lakes in 1929. Since its discovery, the taxon has been reported in 50% (20 of 40 studies) of benthos studies published between 1960 and 2007. When found, Manayunkia comprised < 1% of benthos in 70% of examined studies. In one extensive study, Manayunkia occurred in only 26% of 378 sampled events (1991–2009). The taxon was found at higher densities in one area of Lake Erie (mean = 3658/m²) and Georgian Bay (1790/m²) than in five other areas (mean = 60 to 553/m²) of the lakes. A 70-year history of Manayunkia in western Lake Erie indicates it was not found in 1930, was most abundant in 1961 (mean = 8039, maximum = 67,748/m²), and decreased in successive periods of 1982 (3529, 49,639/m²), 1993 (1876, 25,332/m²), and 2003 (79, 2583/m²). It occurred at 48% of stations in 1961, 58% in 1982, 52% in 1993, and 6% of stations in 2003. In all years, Manayunkia was distributed primarily near the mouth of the Detroit River. Causes for declines in distribution and abundance are unknown, but may be related to pollution-abatement programs that began in the 1970s, and invasion of dreissenid mussels in the late-1980s which contributed to de-eutrophication of western Lake Erie. At present, importance of the long-term decline of Manayunkia in Lake Erie is unknown.     

河湖长制下跨界河湖联合管理保护对策研究——以太湖为例

以太湖流域为例,通过文献整理、现场调研、座谈交流等方式,梳理太湖流域生态环境现状和管理情况,总结太湖流域联合管理保护经验,分析太湖流域联合管理保护方面存在的不足。在此基础上,从推进流域整体管理保护立法、出台跨界河湖联防联控指导意见、统一规划、统一标准、加强河湖保护和治理协同作业、以水定产、绿色发展等方面,提出加强太湖流域联合管理保护的对策建议,以期能对提升太湖流域跨界综合管理与河湖长制推行水平有所帮助。     

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.     

Evidence for Remote Effects of Dreissenid Mussels on the Amphipod Diporeia: Analysis of Lake Ontario Benthic Surveys, 1972–2003

The status of invasive dreissenid mussels (Dreissena polymorpha and D. bugensis) and native amphipods (Diporeia spp.) in Lake Ontario was assessed in 2003 and compared with historical data. D. polymorpha (zebra mussels) were rarely observed in 2003, having been displaced by D. bugensis (quagga mussels). D. bugensis expanded its depth range from 38 m depth in 1995 to 174 m in 2003 and this dreissenid reached densities averaging 8,000/m² at all sites < 90 m. During the same time period, Diporeia populations almost completely disappeared from 0–90 m depth, continuing a declining trend from 1994–1997 reported in previous studies. The average density of Diporeia in the 30–90 m depth interval decreased from 1,380/m² to 63/m² between 1997 and 2003. Prior to 2003, areas deeper than 90 m represented a refuge for Diporeia, but even these deep populations decreased, with densities declining from 2,181/m2 in 1999 to 545/m2 in 2003. Two common hypotheses for the decline of Diporeia in the Great Lakes are food limitation and a toxin/pathogen associated with dreissenid pseudofeces. The Diporeia decline in deep waters preceded the expansion of D. bugensis to these depths, and suggests that shallow dreissenid populations remotely influence profundal habitats. This pattern of decline is consistent with mechanisms that act from some distance including nearshore dreissenid grazing and downslope transport of pseudofeces.     

湖泊分蓄洪区洪水风险图编制探讨——以湖北武湖、涨渡湖为例

通过对湖北省武湖和涨渡湖分蓄洪区洪水风险图编制工作的总结,介绍了这2个分蓄洪区洪水风险图编制的范围、内容及方法,探讨了溃口洪水风险的影响因素,并分析了分蓄洪区特征参数可能存在的问题。结果表明此次复核的武湖分蓄洪区的容积和面积与《长江流域防洪规划》中的值基本一致,但涨渡湖的值却差别很大。另外,根据编制成果,无论长江干流扒口还是支流溃堤,武湖分蓄洪区的三里桥街和武湖街,涨渡湖分蓄洪区的双柳街、涨渡湖街和汪集街等地势低洼地区,洪水到达较快,受影响均较严重。但由于安全设施缺乏,安全避洪转移存在着一定困难,因此对避洪转移方案提出了新的思路,建议利用分蓄洪区内的高速公路进行人口的转移和临时安置。研究成果可为后续分蓄洪区的风险图编制提供参考。     

Bacterial abundance on the skin,gills and intestines of Cyprinus carpio in Lake Naivasha,Kenya: Implications for public health and fish quality

Cyprinus carpio is the most important fish species in the Lake Naivasha fishery, comprising 51% of the total catch in the lake. Microflora, especially enteric bacteria of human or animal origin, are the causative agent for fish contamination and spoilage. Poor sanitation standards and poor sewage treatment and disposal methods within Lake Naivasha and its catchment pose a great threat for degrading the quality of C. carpio. The potential impact is rejection of the fish in the local, regional and international markets, risking the collapse of the Lake Naivasha fishery. This study determined the bacterial quality of water and C. carpio from three different sites within Lake Naivasha, namely Malewa River mouth, sewage discharge point and a mid‐lake site, based on plate count techniques. Physicochemical parameters characterizing the lake water also were also measured in situ. This study results indicated that both the fish and water in Lake Naivasha exhibited poor bacterial quality. All the physicochemical parameters were within the recommended range for fish culture, although they also were conducive to the proliferation of bacteria. Most of the sampling sites exhibited significant spatial variation in their bacterial abundance (P < 0.05). The sewage discharge sampling site exhibited the highest mean density values for bacterial densities and clearly degrade the quality of the fish in the lake. Proper sewage treatment, and the installation of modern sanitation facilities, is recommended to improve the bacterial quality of the fish.     

Effects of Temperature and Other Factors on Summer Phosphorus in the Inner Bay of Quinte,Lake Ontario: Implications for Climate Warming

Summer total phosphorus (TP) concentrations in the inner Bay of Quinte (northeastern Lake Ontario), averaging about five times higher than winter concentrations, were strongly influenced by positive reflux of sediment TP. Several factors potentially influencing the magnitude of the summer peak (1 July to 30 September mean), including seasonal point-source and non-point-source TP loading, seasonal flushing rates, and water temperature, were explored in a multiple regression analysis. Three variables contributed significantly to explanation of the variance in the overall regression (adjusted R² = 0.876): June to September water temperature, total daily TP loading rate from three local point-sources (sewage treatment plants) and flow-weighted averaged July to September TP concentrations in the lower Trent and Moira rivers.The strong influence of temperature on summer TP concentrations in the inner Bay of Quinte (where water and air temperatures are nearly 1:1) has important implications for climate change. Summer average water temperature increases of 3 to 4°C are within the range of those predicted by several general circulation models (GCMs with 2x CO₂ end points). The multiple regression model suggests that summer TP concentrations could about double with a water temperature rise of 3 to 4°C above the 1990 to 1994 mean. This would effectively “undo” many benefits achieved to date in point-source TP loading control.     

Effects of Anthropogenic Influences on the Trophic State,Land Uses and Aquatic Vegetation in a Shallow Mediterranean Lake: Implications for Restoration

Lake Pamvotis, NW Greece is a shallow Mediterranean eutrophic lake that has changed drastically over the past 50 years. Strong effects, resulted mainly from anthropogenic causes, in the hydrological regime are shown for this area using long term hydrological data and a GIS system for extracting land cover/use changes. A set of aerial imagery acquired in 1945 through 2002 were used to monitor and assess the spatial and temporal changes in land cover/use, focused mainly on the lake’s surface area and its surrounding ecosystem (Natura 2000 area). The significance of the changes in land cover/use distribution within Pamvotis wetland is further discussed depicting the role of the anthropogenic influence on the fragile ecosystem that resulted in the shrinkage of lake’s habitats extent. The purpose of this analysis was to examine the long-term changes on macrophyte community composition, species occurrence and relative abundance with water quality and water level changes over the past century, using historical data, aerial photos and GIS techniques. The results showed that for the last 25 years annual water level fluctuation ranged from 70 to 159 cm. Water level starts decreasing in mid June and increasing again gradually from November until March–April. Intra annual water level fluctuation seems to be affected by land use for agricultural purpose through intensive irrigation and the summer drought as well. A dramatic decline of the submerged vegetation is apparent mainly attributed to anthropogenic pressures. Regarding the land cover/use changes, the most notable and significant alterations are concerning the urban development around the lake, the disappearance of wet meadows and the extension of reed beds. Finally it seems that water budget data as well as the response of the key eutrophication parameters are affected from both hydrological alterations and point/non-point pollution sources.     

The Effects of Groundwater and Surface Water Use on Total Water Availability and Implications for Water Management: The Case of Lake Naivasha, Kenya

This study discusses the effects of water abstractions from two alternative sources on the available water volume around Lake Naivasha, Kenya: the lake itself and a connected aquifer. An estimation of the water abstraction pattern for the period 1999–2010 is made and its effect on the available water volume in Lake Naivasha and its connected aquifer is evaluated using a simple water balance modeling approach. This study shows that accurate estimates of annual volume changes of Lake Naivasha can be made using a simple monthly water balance approach that takes into account the exchange of water between the lake and its connected aquifer. The amount of water that is used for irrigation in the area around Lake Naivasha has a substantial adverse effect on the availability of water. Simulation results of our simple water balance model suggests that abstractions from groundwater affect the lake volume less than direct abstractions from the lake. Groundwater volumes, in contrast, are much more affected by groundwater abstractions and therefore lead to much lower groundwater levels. Moreover, when groundwater is used instead of surface water, evaporation losses from the lake are potentially higher due to a larger lake surface area. If that would be the case then the overall water availability in the area is more strongly affected by the abstraction of groundwater than by the abstraction of surface water. Therefore water managers should be cautious when using lake levels as the only indicator of water availability for restricting water abstractions.