An ecosystem health assessment of the Detroit River and western Lake Erie

The Canada-U.S. State of the Strait Conference is a biennial forum with a 22-year history of assessing ecosystem status and providing advice to improve research, monitoring, and management of the Detroit River and western Lake Erie. The 2019 conference focused on assessing ecosystem health based on 61 indicators. Although there has been considerable improvement in the Detroit River since the 1960s, much additional cleanup is needed to restore ecosystem health. Western Lake Erie is now at risk of crossing several potential tipping points caused by the interactions of a variety of drivers and their stresses. This assessment identified eight environmental and natural resource challenges: climate change; population growth/transportation expansion/land use changes; chemicals of concern; human health/environmental justice; aquatic invasive species; habitat loss/degradation; nonpoint source pollution; and eutrophication/harmful algal blooms. Specific recommendations for addressing each challenge were also made. Climate change is the most pressing environmental challenge of our time and considered a “threat multiplier” whereby warmer, wetter, and more extreme climatic conditions amplify other threats such as poor air quality effects on vulnerable residents, species changes, and nonpoint source runoff and combined sewer overflow events that contribute to eutrophication and can manifest as harmful algal blooms. Our assessment found that investments in monitoring and evaluation are insufficient and that the region's intellectual and environmental capital is not being leveraged sufficiently to address current challenges. Continued investment in this transnational network is essential to support ecosystem-based management.     

Geochemical Availability of Some Trace and Major Elements in Surficial Sediments of the Detroit River and Western Lake Erie

Surficial bottom sediment from twenty locations in the Detroit River and western Lake Erie has been analyzed for potentially available Ba, Be, Cd, Cr, Co, Cu, Pb, Mn, Mo, Ni, P, V, and Zn. The highest concentrations of all but one of these elements were found at a station at the river-lake interface very close to a dumping ground. The environmental mobility of Cd, Zn, Co, Pb, Cr, Ni, and P is controlled by hydrous iron oxides, whereas V and Mo is controlled by aluminosilicates. The iron oxide phase exhibits a very high sorption capacity for phosphorus (molar adsorption coefficient = .361) which is attributed to the high loadings of Fe and P at the confluence of the Rouge and Detroit rivers as well as continuous inputs along the length of the Detroit River. It is suggested that phosphorus controls instituted in the 1970s will probably result in the iron oxide phase having greater sorption capacity for toxic metals because of the decreasing competition from phosphorus for binding sites.     

Organochlorine and Mercury Residues in Young-of-the-Year Spottail Shiners from the Detroit River,Lake St. Clair,and Lake Erie

Young-of-the-year spottail shiners (Notropis hudsonius) were used as biomonitors to determine the spatial distribution (1982/83) and assess trend data for organochlorine and mercury residues. Significantly (p < 0.01) higher PCB residues were found in Detroit River spottail shiners than in collections from southwestern Lake St. Clair and northwestern Lake Erie. The highest PCB residues were found in the west bank collections from Michigan waters (912–2,997ng/g) compared to the mid-stream (96–290 ng/g) and east bank collections (153–316 ng/g). Chlordane residues were found to be elevated in all spottail shiner samples from urbanized areas. Octachlorostyrene and ∑ DDT residues were distributed uniformly within the study area, whereas mercury concentrations were found to be lower in spottail shiners from northwestern Lake Erie than in comparable samples from the Detroit River and southwestern Lake St. Clair. Residues for BHC, heptachlor, aldrin, and chlorinated benzenes were near their detection limits; mirex and chlorinated phenols were not detectable. Recent (1982/83) PCB residue levels in spottail shiners exceeded the IJC aquatic life objective (Great Lakes Water Quality Agreement of 1978) at all the sites sampled, except at Pike Creek in Lake St. Clair. PCB residues in spottail shiners from Pike Creek, Big Creek, and Leamington have declined significantly (p < 0.01) since the mid-seventies. Mercury and chlordane residues have decreased in spottail shiner samples from Leamington, but have remained virtually unchanged at Big Creek and Pike Creek.     

Distribution of Hydrocarbons and Chlorinated Hydrocarbons in Various Phases of the Detroit River

Concentrations of several chlorohydrocarbons, polychlorinated biphenyls, and polynuclear aromatic hydrocarbons in the Detroit River were measured. For purposes of this study, the river ecosystem was divided into six phases or compartments: sediments, pore water in the sediments, suspended solids, subsurface water, surface microlayer, and air. Significant amounts of the above mentioned compounds occur in all of these compartments except air (for which our detection was relatively insensitive). The sediments contained over 99% of the chlorinated compounds. The polynuclear aromatic hydrocarbons were distributed between the subsurface water and the sediments.     

From River to Lake: Phosphorus partitioning and algal community compositional changes in Western Lake Erie

The Maumee River is an important source of phosphorus (P) loading to western Lake Erie and potentially a source of Microcystis seed colonies contributing to the development of harmful algal blooms in the lake. Herein, we quantified P forms and size fractions, and phytoplankton community composition in the river–lake coupled ecosystem before (June), during (August), and after (September) a large Microcystis bloom in 2009. Additionally, we determined the distribution and density of a newly emergent cyanobacterium, Lyngbya wollei, near Maumee Bay to estimate potential P sequestration. In June, dissolved organic phosphorus (DOP) was the most abundant P form whereas particulate P (partP) was most abundant in August and September. Green algae dominated in June (44% and 60% of total chlorophyll in river and lake, respectively) with substantial Microcystis (17%) present only in the river. Conversely, in August, Microcystis declined in the river (3%) but dominated (32%) the lake. Lake phytoplankton sequestered < 6% of water column P even during peak Microcystis blooms; in all lake samples < 112 μm non-algal particles dominated partP. Lyngbya density averaged 19.4 g dry wt/m², with average Lyngbya P content of 15% (to 75% maximum) of water column P. The presence of Microcystis in the river before appearing in the lake indicates that the river is a potential source of Microcystis seed colonies for later lake blooms, that DOP is an important component of early summer total P, and that L. wollei blooms have the potential to increase P retention in nearshore areas.     

Restoration of Wildcelery,Vallisneria americana Michx., in the Lower Detroit River of the Lake Huron-Lake Erie Corridor

American wildcelery (Vallisneria americana Michx.) is a valuable submersed aquatic plant that was negatively affected by pollution and urban runoff in the lower Detroit River for much of the 20th century. Following 25 years of water-pollution and urban-runoff abatement initiated in the early 1970s, we postulated that water clarity had increased and that this would allow restoration of wildcelery in the lower Detroit River. In addition, water clarity increased in the late 1980s due to water filtration and particulate removal by exotic dreissenid mussels (Dreissena polymorpha and D. bugensis), which could contribute to potential wildcelery restoration. We sampled wildcelery in 1996–97 and compared these data to wildcelery data from 1950–51 and 1984–85. Over the 48-year period of comparison, areal density of wildcelery tubers decreased 72% (from 51.2 million to 14.4 million tubers) between 1950–51 and 1984–85 then increased 251% (from14.4 million to 50.5 million tubers) between 1984–85 and 1996–97. As a result, overall areal abundance was about the same in 1950–51 as in fall 1996–97. However, tuber densities in spring 1996 were similar to historical low abundances in springs of 1984–85. Then between spring and fall 1996, tuber densities increased 333% and remained relatively abundant through October 1997 indicating the beginning of the restoration of wildcelery in the lower Detroit River. In addition, we believe further reductions of turbidity through continued pollution-abatement programs and water filtration by dreissenid mussels combined with habitat protection and active management of wildcelery will contribute even further to the restoration of wildcelery in the Detroit River in the 21st century.     

Food of Freshwater Drum in Western Lake Erie

The abundance of freshwater drum (Aplodinotus grunniens) suggests they play an important role in the Lake Erie ecosystem. Our analysis of freshwater drum digestive tracts and macrobenthic samples collected from western Lake Erie indicates that drum were selective feeders. Planktonic cladocerans and larval midges (Chironomidae) were the primary prey organisms eaten by drum. Young-of-the-year fed mostly on cladocerans, while yearling and older drum ate both cladocerans and midge larvae. Decapods, pelecypods, and fish were found only in the digestive tracts of drum longer than 250 mm. While the most abundant organisms in benthic samples were cladocerans (ephippial) and oligochaetes (89.5% by number), they constituted less than 1% of the diet. An evaluation of food selectivity, using Ivlev's index of electivity for benthic organisms, indicated that adult drum preferred midges to any other benthic food.     

Occurrence of the Asiatic Clam Corbicula Fluminea in the Maumee River and Western Lake Erie

The Asiatic clam was found in only two locations along the southern shore of the western basin of Lake Erie: the thermal plume areas of two coal-fired power plants with once-through condenser cooling systems. Three sewage treatment plant outfalls were sampled, but Corbicula were found only in the sewage treatment plant outfall that was within the thermal plume of a power plant. No Corbicula were found in the vicinity of the nuclear power plant which has a closed-cycle natural draft cooling tower, and hence no significant thermal plume.From the age of some of the specimens, this clam has probably resided in the region since 1978. The Great Lakes are farther north than the natural range of this clam, and prolonged cold temperatures in this region may be responsible for the confinement of this clam to baseload power plants with continuous thermal plumes.     

Updated phosphorus loads from Lake Huron and the Detroit River: Implications

The binational Great Lakes Water Quality Agreement (GLWQA) revised Lake Erie’s phosphorus (P) loading targets, including a 40% western and central basin total P (TP) load reduction from 2008 levels. Because the Detroit and Maumee River loads are roughly equal and contribute almost 90% of the TP load to the western basin and 54% to the whole lake, they have drawn significant policy attention. The Maumee is the primary driver of western basin harmful algal blooms, and the Detroit and Maumee rivers are key drivers of central basin hypoxia and overall western and central basin eutrophication. So, accurate estimates of those loads are particularly important. While daily measurements constrain Maumee load estimates, complex flows near the Detroit River mouth, along with varying Lake Erie water levels and corresponding back flows, make measurements there a questionable representation of loading conditions. Because of this, the Detroit River load is generally estimated by adding loads from Lake Huron to those from the watersheds of the St. Clair and Detroit rivers and Lake St. Clair. However, recent research showed the load from Lake Huron has been significantly underestimated. Herein, I compare different load estimates from Lake Huron and the Detroit River, justify revised higher loads from Lake Huron with a historical reconstruction, and discuss the implications for Lake Erie models and loading targets.     

Seasonal Variation of Nutrient Limitation in Western Lake Erie

Monthly nutrient enrichment experiments were performed from April through October, 1983, to identify growth limiting nutrients of natural phytoplankton assemblages collected from a station in the Pigeon Bay waters off the north shore of Lake Erie's western basin. Data from these experiments suggest that silica was the major limiting nutrient in April, phosphorus was the major limiting nutrient in May-September, and trace metals were limiting in October. These results show that nutrient enrichment experiments should be performed often enough to account for seasonal changes in the physicochemical environment as well as seasonal succession in phytoplankton. The conclusion that phosphorus was the major limiting nutrient in summer is different from the conclusions of the late 1960s and early 1970s that nitrogen was the major limiting nutrient in the summer in the western basin and suggests a possible shift from nitrogen to phosphorus limitation. Pigeon Bay nutrient trend data show that summer nitrate:soluble reactive phosphorus ratios have increased from approximately 4 in the late 1960s to over 40 in the late 1970s and early 1980s, corroborating that a shift has probably occurred. This shift in nutrient limitation is probably due to reduced bioavailable phosphorus loadings and increased nitrate loadings to the western basin. The southern portion of the western basin is physicochemically different from the northern portion and may not have responded in the same manner.     

Sampling Larval Fish in the Littoral Zone of Western Lake Erie

Sampling techniques for larval fish were evaluated in the littoral zone (1- to 6-m deep) of western Lake Erie in 1975 and 1976. Catch rates were compared using slow-speed, 1-m-diameter plankton nets in daytime and nighttime oblique and stratified tows above bottom and in daytime epibenthic tows with an aluminum sled. Sampling efficiency also was compared using nets of 363-, 571-, 760-, and 1,000-μm mesh towed from 1 to 5 min. The most abundant larvae captured were clupeids (Alosa pseudoharengus and Dorosoma cepedianum), yellow perch (Perca flavescens), rainbow smelt (Osmerus mordax), and white bass (Morone chrysops) Larvae did not consistently occur in one stratum over another in water above bottom, but concentrated near bottom during the day. Oblique, nighttime tows above bottom caught at least 20 times the larvae caught in daylight tows above bottom. Post-yolk-sac larvae were most efficiently captured in nighttime oblique or stratified tows, while yolk-sac larvae were more efficiently captured by epibenthic, daytime tows. The 363-μm-mesh net retained more yolk-sac larvae than nets of larger mesh sizes and was at least as effective as the larger nets at capturing post-yolk-sac larvae. Nets with 571-μm mesh towed for 1, 2, 3, 4, and 5 min had similar catch rates so mesh plugging was not a problem under conditions sampled. Filtering rates of 363- and 760-μm mesh were similar to the filtering rate of 571-μm mesh when towed for 3 min. Precision (number of larvae caught per minute) and number of species caught were similar in tows more than 1-min long up to 5 min.     

Polycyclic Aromatic Hydrocarbons in Sediments of the Southern Basin of Lake Michigan

The southern basin of Lake Michigan is receiving polycyclic aromatic hydrocarbon (PAH) inputs from many sources. An investigation of parent PAH compounds in sediments from different depositional zones revealed concentrations ranging from 0.2–6.2 μg/g dry sediment weight. The distribution of the parent PAH is distinctive of high temperature combustion sources. PAH alkyl homolog analyses showed the presence of several highly alkylated PAHs, such as retene, indicating possible inputs from paper industries, and alkylated naphthalenes, which may indicate contributions from municipal/industrial effluents and petroleum shipping activities. A subsurface concentration maximum of total parent PAHs observed in depositional zone sediments may be due to either a physical process (resuspension) or decreased anthropogenic input.     

Occurrence of Zebra Mussels in Near-shore Areas of Western Lake Erie

We measured biomass, percent coverage, and length-frequency of zebra mussels in near-shore areas of western Lake Erie between 16 September and 10 November 1993 as part of a larger study on the ecological relationship between diving ducks and zebra mussels. Wet weight biomass of zebra mussels, determined by SCUBA diving, ranged from 0 to 3,611 g/m² and averaged ( ± 1 SE) 1,270 ± 380 g/m² (n = 11). Percent coverage of lake bottom by zebra mussels ranged from 0 to 70% and averaged 17 ± 4.0% (n = 27). Percent coverage of zebra mussels was relatively high in the northern portion (28–70% coverage) and in the southwestern portion (18–40%), but relatively low ( < 5%) in the southeastern portion of the study area. Percent coverage by zebra mussels, determined from underwater videography, was highly correlated (r² = 0.96) with zebra mussel biomass. Analysis of length-frequency data indicated that there was prominent recruitment of juvenile zebra mussels at only three of eight sites. Average shell length ranged from 11 mm to 15 mm at the other five sites. The non-uniform distribution of zebra mussels, as determined from biomass and videography, may have important ramifications when assessing zebra mussel impacts on waterfowl. These data may also be used when assessing impact of zebra mussels on other aquatic organisms in the near-shore areas of western Lake Erie.     

Occurrence of the Deepwater Sculpin (Myoxocephalus thompsoni) in Western Lake Erie

Reported here is the collection of two specimens of deepwater sculpin (Myoxocephalus thompsoni) from Ohio waters of western Lake Erie in 1995. Both specimens were collected while sampling for pelagic walleye (Stizostedion vitreum) larvae. A 15.0-mm TL deepwater sculpin larva was collected over Toussaint Reef on 29 April 1995 and a 17.0-mm TL juvenile was collected west of South Bass Island State Park on 12 May 1995. It appears that there are no references to collections of deepwater sculpins from western Lake Erie in the literature or from communications with local management agency personnel. While these young deepwater sculpin may have come from ballast water or from a reproducing population in Lake Erie, the collection of 21 deepwater sculpin (12 to 19 mm TL) in the St. Clair River in May 1990 provides evidence of downstream transport from Lake Huron where indigenous populations exist.     

Lake Erie in Mid-Winter

The results of four surveys of Lake Erie during mid-winter are presented here. The most recent survey, from February 15 to 17, 1977, was conducted during an exceptionally cold winter to determine whether six weeks of complete ice-cover had led to low levels of oxygen concentration in the lake. The results showed that all parts of the lake, even the shallow, normally highly productive areas, contained acceptable levels of oxygen. Apparently, production of oxygen by a small phytoplankton population counterbalanced a fairly low uptake of oxygen and maintained the level of oxygen concentration in most of the water above 90% saturation. The 1976-77 winter phytoplankton biomass was low (0.1 to 1.0 gm biomass per m³) and consisted mostly of diatoms. It appears that some of the phytoplankton were photo-synthetically active under 70 cm of ice and 23 m of water. All surveys of the lake showed the water to be virtually isothermal at a temperature just above the freezing point of water. The maximum temperature differences observed were about 0.2° in magnitude and were found in the East Basin. Nevertheless, the slight temperature differences apparently caused density currents under the ice, which resulted in lowered oxygen concentrations in the deepest part of the East Basin.     

Energy Relations in Cladophora Glomerata from Lake Erie

Photosynthesis and respiration measurements were made at lake temperatures with Cladophora glomerata collected from the eastern basin of Lake Erie. Although water temperatures varied from 10°C in May to almost 25°C in July, neither photosynthesis nor respiration showed any general increase in rates, even though there were wide daily fluctuations. Starch levels were low during the period of rapid growth but then increased until the time of sloughing. These data suggest that photosynthesis and respiration in Cladophora temperature-adapt and that a negative energy balance is not the cause of the mid-summer die-off.     

Invertebrate Communities Associated with Bangia Atropurpurea and Cladophora Glomerata in Western Lake Erie

The appearance of the marine alga Bangia atropurpurea (Rhodophyta) in Lake Erie has been followed by its rapid dispersal throughout the eulittoral zone of the lake. Bangia was extensively sampled to determine its suitability as a habitat for littoral organisms. Present data indicate that the only organisms capable of maintaining populations on Bangia filaments are larval Chironomidae. Cladophora supports a larger and more diverse community. It is concluded that the mucilaginous cell wall of Bangia provides a less stable substrate for attached or clinging organisms than does the cellulose cell wall of Cladophora. The presence of Bangia in the littoral zone of Lake Erie results in a reduction of the quantity and diversity of algal epiphytes and may negatively impact the littoral food web.     

Limnetic Larval Fish in the Nearshore Zone of the Western Basin of Lake Erie

Gizzard shad/alewife, Dorosoma cepedianum/Alosa pseudoharengus, emerald shiners, Notropis atherinoides, white bass/white perch, Morone chrysops/Morone americana, and yellow perch, Perca flavescens, constituted over 97% of the larval fish collected in Ohio and Michigan waters of the western basin of Lake Erie during 1977. Significantly greater numbers of gizzard shad/alewife and spottail shiner, Notropis hudsonius, larvae were captured immediately adjacent to the shore than at a depth of 5 m offshore while greater numbers of smelt, Osmerus mordax, larvae were captured at points further offshore at a depth of 5 m than at points immediately adjacent to the shore. Significantly greater numbers of walleye, Stizostedion vitreum, larvae were collected along the Ohio shoreline portion of the study area than in Maumee Bay or along the Michigan shoreline. Significantly greater numbers of freshwater drum, Aplodinotus grunniens, larvae were collected in Maumee Bay.     

Predation on Walleye Eggs by Fish on Reefs in Western Lake Erie

We examined diets of fishes from gillnet and egg pump collections conducted on reefs in western Lake Erie during walleye (Sander vitreus) egg incubation periods from 1994–1999 and 2004 to assess incidence of walleye eggs in fish diets. We collected no potential egg predators in samples taken in 1994 but from 1995–1999 and in 2004 we caught 22 different species of fish on reefs in addition to spawning walleye. In most years, white perch (Morone americana) stomachs contained more walleye eggs than any other species on the reefs averaging 253 eggs per stomach. We also found lower numbers of walleye eggs in the stomachs of channel catfish (Ictalurus punctatus; 53 eggs/stomach), johnny darter (Etheostoma nigrum; 2 eggs/stomach), logperch (Percina caprodes; 10 eggs/stomach), quillback (Carpiodes cyprinus; 184 eggs/stomach), rock bass (Ambloplites rupestris; 3 eggs/stomach), round goby (Neogobius melanostomus; 4 eggs/stomach), sculpin (Cottidae; 21 eggs/stomach), silver chub (Macrhybopsis storeriana; 3 eggs/stomach), spottail shiner (Notropis hudsonius; 14 eggs/stomach), trout-perch (Percopsis omiscomaycus; 30 eggs/stomach), white sucker (Catastomus commersonii; 20 eggs/stomach), and yellow perch (Perca flavescens; 181 eggs/stomach). Similar to other studies of predation on walleye eggs, our results indicate that prolonged incubation periods increase the potential for egg loss due to predation.