Tailings generated by mining account for the largest world-wide waste from industrial activities. As an element, copper is relatively uncommon, with low concentrations in sediments and waters, yet is very elevated around mining operations. On the Keweenaw Peninsula of Michigan, USA, jutting out into Lake Superior, 140 mines extracted native copper from the Portage Lake Volcanic Series, part of an intercontinental rift system. Between 1901 and 1932, two mills at Gay (Mohawk, Wolverine) sluiced 22.7 million metric tonnes (MMT) of copper-rich tailings (stamp sands) into Grand (Big) Traverse Bay. About 10 MMT formed a beach that has migrated 7 km from the original Gay pile to the Traverse River Seawall. Another 11 MMT are moving underwater along the coastal shelf, threatening Buffalo Reef, an important lake trout and whitefish breeding ground. Here we use remote sensing techniques to document geospatial environmental impacts and initial phases of remediation. Aerial photos, multiple ALS (crewed aeroplane) LiDAR/MSS surveys, and recent UAS (uncrewed aircraft system) overflights aid comprehensive mapping efforts. Because natural beach quartz and basalt stamp sands are silicates of similar size and density, percentage stamp sand determinations utilise microscopic procedures. Studies show that stamp sand beaches contrast greatly with natural sand beaches in physical, chemical, and biological characteristics. Dispersed stamp sand particles retain copper, and release toxic levels of dissolved concentrations. Moreover, copper leaching is elevated by exposure to high DOC and low pH waters, characteristic of riparian environments. Lab and field toxicity experiments, plus benthic sampling, all confirm serious impacts of tailings on aquatic organisms, supporting stamp sand removal. Not only should mining companies end coastal discharges, we advocate that they should adopt the UNEP “Global Tailings Management Standard for the Mining Industry”.

Tailings generated by mining account for the largest proportion of global waste from industrial activities. Copper is relatively uncommon world-wide, with low concentrations in sediments and waters, yet is very elevated around mining sites. On the Keweenaw Peninsula of Michigan, USA, jutting out into Lake Superior, 140 mines extracted native copper from the Portage Lake Volcanic Series, part of an intercontinental rift system. Between 1901-1932, two mills at Gay (Mohawk, Wolverine) sluiced 22.7 million metric tonnes (MMT) of copper-rich tailings (stamp sands) into Grand (Big) Traverse Bay. Here we examine: 1) 3D coastal elevation and reef bathymetry, 2) particle dispersal, 3) copper concentrations and leaching, plus 4) shoreline toxicity. About 10 MMT of tailings created a migrating coastal beach that stretches 7 km from the Gay pile to the Traverse River Seawall. Another 10 MMT are moving underwater on the coastal shelf, threatening Buffalo Reef, an important lake trout and whitefish breeding ground. Aerial photos, ALS (plane) LiDAR, and relatively inexpensive UAS (drone) surveys characterize shoreline structure and aid initial remediation. Because sands (natural beach quartz, stamp sand basalt) are silicates of similar density, particle dispersal is similar and challenging. However, stamp sand beaches contrast greatly with natural sand beaches in both physical profile and chemistry. Dispersing particles retain copper, and release toxic concentrations. Leaching is elevated by exposure to high DOC and low pH waters. Field experiments, shoreline seining, and benthic sampling confirm serious impacts on aquatic biota, supporting tailings removal.

The balance between competition and predation prompted early research into species coexistence. Spe-cies in a sibling species complex (subgenus Bosmina) often occur together in lakes (47 %). Initial studies in Lake Washington revealed that two sibling species of Bosmina (western B. longirostris, B. liederi) overlapped across Union Bay. One species with shorter spines was the competitive dominant and was more abundant in shallow, nearshore bay waters, whereas the other species had longer defensive spines that allowed it to survive with an off-shore invertebrate predator (Epischura). Initially a simple population model developed by Slobodkin, and slightly modified by Emlen, was applied to the circumstances. The model predicted reversed outcomes over a gradient of predation and stable coexistence of species at intermediate predation levels. Here we conduct a full stability analysis of the Slobodkin/Emlen model, and then incorporate a simple evolutionary tradeoff into the equations. By "tradeoffs" we mean that defensives are purchased at a cost to competitive ability. The L-V trade-off model predicts coexistence of two species because there are two limiting factors (competition, predation), and increases the range of stability conditions. Field experiments in Lake Washington demonstrated reversal of outcomes at predation ex-tremes, whereas enclosure experiments in Lake Norford, Vermont, confirmed co-existence of sibling species over a range of intermediate predation levels. Comparable experiments in Third Sister Lake, Michigan, showed that when predation removal rates were pushed to extremes (more efficient predators), sibling species mixtures collapsed to single species and then to local extinction, a final aspect of the simple model.

Over a century ago, copper mills on the Keweenaw Peninsula of Lake Superior sluiced 64 million metric tonnes (MMT) of tailings into coastal waters, creating a metal-rich “halo”. Here we show that relatively small discharges can spread widely in time and space. Mass Mill (2.9 MMT) dumping into Lake Superior also illustrates the complexity of interactions with Indigenous Peoples. A combination of aerial photos, LiDAR, and a microscope technique for distinguishing end-member particles traces the migration of tailings. The clay fraction spread rapidly across Keweenaw Bay and curled into terminal L’Anse Bay, within tribal Reservation boundaries. The coarse stamp sand fraction moved more slowly southward as a beach sand deposit onto Sand Point, a sacred burial ground. Despite the partial recovery of northern beaches and southern sediments, concerns continue about chemical contamination. Mass Mill provides an excellent example of Indigenous Peoples’ territorial and resource issues with mining. A major difficulty with “legacy” discharges is that there are no longer any “responsible parties”. Initially, federal and state officials were fearful that treaty rights might warrant reparations. Recently, multiple agency/state funding programs supported international (IJC) award-winning restoration efforts by tribal members, illustrating how Indigenous Peoples and governments can work together to safeguard treaty rights.

On the Keweenaw Peninsula of Lake Superior, two stamp mills (Mohawk and Wolverine) discharged 22.7 million metric tonnes (MMT) of tailings (1901–1932) into the coastal zone off the town of Gay. Migrating along the shoreline, ca. 10 MMT of the tailings dammed stream and river outlets, encroached upon wetlands, and contaminated recreational beaches. A nearly equal amount of tailings moved across bay benthic environments into critical commercial fish spawning and rearing grounds. In the middle of the bay, Buffalo Reef is important for commercial and recreational lake trout and lake whitefish production (ca. 32% of the commercial catch in Keweenaw Bay, 22% along southern Lake Superior). Aerial photographs (1938–2016) and five LiDAR and multispectral over-flights (2008–2016) emphasize: (1) the enormous amounts of tailings moving along the beach; and (2) the bathymetric complexities of an equal amount migrating underwater across the shelf. However, remote sensing studies encounter numerous specific challenges in coastal environments. Here, we utilize a combination of elevation data (LiDAR digital elevation/bathymetry models) and in situ studies to generate a series of physical, chemical, and biological geospatial maps. The maps are designed to help assess the impacts of historical mining on Buffalo Reef. Underwater, sand mixtures have complicated multispectral bottom reflectance substrate classifications. An alternative approach, in situ simple particle classification, keying off distinct sand end members: (1) allows calculation of tailings (stamp sand) percentages; (2) aids indirect and direct assays of copper concentrations; and (3) permits determinations of density effects on benthic macro-invertebrates. The geospatial mapping shows how tailings are moving onto Buffalo Reef, the copper concentrations associated with the tailings, and how both strongly influence the density of benthic communities, providing an excellent example for the International Maritime Organization on how mining may influence coastal reefs. We demonstrate that when large amounts of mine tailings are discharged into coastal environments, temporal and spatial impacts are progressive, and strongly influence resident organisms. Next steps are to utilize a combination of hi-resolution LiDAR and sonar surveys, a fish-monitoring array, and neural network analysis to characterize the geometry of cobble fields where fish are successful or unsuccessful at producing young.

Over a century ago, shoreline copper mills sluiced more than 64 million metric tonnes of tailings into Lake Superior, creating a “halo” around the Keweenaw Peninsula with a buried copper peak. Here we examine how tailings from one of the smaller mills (Mass Mill, 1902–1919) spread as a dual pulse across southern Keweenaw Bay and onto tribal L’Anse Indian Reservation lands. The fine (“slime clay”) fraction dispersed early and widely, whereas the coarse fraction (stamp sands) moved more slowly southward as a black sand beach deposit, leaving scattered residual patches. Beach stamp sands followed the path of sand eroding from Jacobsville Sandstone bluffs, mixing with natural sands and eventually adding onto Sand Point, at the mouth of L’Anse Bay. Dated sediment cores and a multi-elemental analysis of the buried Cu-rich peak in L’Anse Bay confirm a tailings origin. Copper concentrations are declining in the bay, yet copper fluxes remain elevated. The spatial and temporal studies underscore that enhanced sediment and copper fluxes around the Keweenaw Peninsula largely reflect historic mining releases. Mercury is correlated with copper, yet mercury concentrations and fluxes remain relatively low in Keweenaw Bay compared to nearby Superfund sites (Torch and Portage Lakes), perhaps reflecting the absence of smelters on Keweenaw Bay. Tribal efforts to remediate contamination are progressing, but are hindered by recent high water levels plus severe storms. The long-term repercussions of Mass Mill discharges caution against mine companies discharging even small amounts of tailings into coastal environments.

How do native species react to the presence of an invader? Consumption by resident fish is important in determining the yearly mortality of the invasive cladoceran Bythotrephes. In aquarium experiments, we discovered that small pumpkinseed sunfish (Lepomis gibbosus) were efficient at removing spines from Bythotrephes longimanus and consuming the adults. Experiments quantified how frequently pumpkinseeds showed successful removal of spines, and compared predatory performance relative to other species of fish. We also checked if Bythotrephes' resting eggs pass through the guts of pumpkinseeds in viable condition. The experiments revealed that pumpkinseed sunfish (45-70 mm total length, TL) from two geographic regions removed spines 87% of the time. Spine-handling techniques allowed pumpkinseeds to consume Bythotrephes faster than other species of small (<70 mm, TL) fish [yellow perch (Perca/lavescens) and smallmouth bass (Micropterus dolomieu)]. Forty three percent of Bythotrephes' resting eggs fed to pumpkinseeds passed through digestive systems intact, a property shared with other fish species. Our findings suggest that a native fish that possesses specialized morphology and behavior for hard-shelled prey manipulation (mollusk consumption) is pre-adapted to counter Bythotrephes' spine defense. The studies raise two questions: 1) to what degree does pumpkinseed predation influence the geographic distribution of Bythotrephes, and 2) could pumpkinseeds become an effective biological control agent? Published by Elsevier B.V. on behalf of International Association for Great lakes Research.

The low turbidity of northern Great Lakes waters allows lidar sufficient penetration to greatly aid environmental studies of coastal environments. On the Keweenaw Peninsula of Lake Superior, Big Traverse Bay provides an excellent example of mine tailings spreading from an old coastal release site. Between 1901 and 1932, two stamp mills (Mohawk and Wolverine) discharged 22.7 million metric tonnes of tailings (stamp sands) off the town of Gay. Along beaches, migrating stamp sands have dammed stream outlets, encroached upon wetlands, and contaminated recreational beaches. The tailings are now threatening benthic environments and critical commercial fish breeding grounds. Buffalo Reef is important for commercial and recreational lake trout and lake whitefish production (32% of the commercial catch in Keweenaw Bay, 22% of southern Lake Superior). Aerial photographs and five lidar over-flights emphasize: 1) the enormous amounts of stamp sands moving along the shoreline, and 2) large amounts migrating underwater across the bay towards Buffalo Reef. Differences between 2008 and 2016 lidar over-flights are used to quantify underwater stamp sand movement. For years, tailings have accumulated in an ancient riverbed cut (“trough”) just north of Buffalo Reef. Stamp sand overflow out of the “trough” is now moving into Buffalo Reef cobble fields, where fish drop eggs. Ponar sediment studies quantify % stamp sand in sand mixtures around Buffalo Reef, copper concentrations, and quantify impacts on benthic invertebrate taxa. Our study emphasizes that when large amounts of mine tailings are discharged into coastal environments, temporal and spatial impacts are progressive, threatening benthic organisms and fish.

Where light penetration is excellent, the combination of LiDAR (Light Detection And Ranging) and passive bottom reflectance (multispectral, hyperspectral) greatly aids environmental studies. Over a century ago, two stamp mills (Mohawk and Wolverine) released 22.7 million metric tons of copper-rich tailings into Grand Traverse Bay (Lake Superior). The tailings are crushed basalt, with low albedo and spectral signatures different from natural bedrock (Jacobsville Sandstone) and bedrock-derived quartz sands. Multiple Lidar (CHARTS and CZMIL) over-flights between 2008–2016—complemented by ground-truth (Ponar sediment sampling, ROV photography) and passive bottom reflectance studies (3-band NAIP; 13-band Sentinal-2 orbital satellite; 48 and 288-band CASI)—clarified shoreline and underwater details of tailings migrations. Underwater, the tailings are moving onto Buffalo Reef, a major breeding site important for commercial and recreational lake trout and lake whitefish production (32% of the commercial catch in Keweenaw Bay, 22% in southern Lake Superior). If nothing is done, LiDAR-assisted hydrodynamic modeling predicts 60% tailings cover of Buffalo Reef within 10 years. Bottom reflectance studies confirmed stamp sand encroachment into cobble beds in shallow (0-5m) water but had difficulties in deeper waters (>8 m). Two substrate end-members (sand particles) showed extensive mixing but were handled by CASI hyperspectral imaging. Bottom reflectance studies suggested 25-35% tailings cover of Buffalo Reef, comparable to estimates from independent counts of mixed sand particles (ca. 35% cover of Buffalo Reef by >20% stamp sand mixtures).

A geographic enigma is that present-day atmospheric deposition of mercury in the Upper Peninsula of Michigan is low (48%) and that regional industrial emissions have declined substantially (ca. 81% reduction) relative to downstate. Mercury levels should be declining. However, state (MDEQ) surveys of rivers and lakes revealed elevated total mercury (THg) in Upper Peninsula waters and sediment relative to downstate. Moreover, Western Upper Peninsula (WUP) fish possess higher methyl mercury (MeHg) levels than Northern Lower Peninsula (NLP) fish. A contributing explanation for elevated THg loading is that a century ago the Upper Peninsula was a major industrial region, centered on mining. Many regional ores (silver, copper, zinc, massive sulfides) contain mercury in part per million concentrations. Copper smelters and iron furnace-taconite operations broadcast mercury almost continuously for 140 years, whereas mills discharged tailings and old mine shafts leaked contaminated water. We show that mercury emissions from copper and iron operations were substantial (60-650 kg per year) and dispersed over relatively large areas. Moreover, lake sediments in the vicinity of mining operations have higher THg concentrations. Sediment profiles from the Keweenaw Waterway show that THg accumulation increased 50- to 400-fold above modern-day atmospheric deposition levels during active mining and smelting operations, with lingering MeHg effects. High MeHg concentrations are geographically correlated with low pH and dissolved organic carbon (DOC), a consequence of biogeochemical cycling in wetlands, characteristic of the Upper Peninsula. DOC can mobilize metals and elevate MeHg concentrations. We argue that mercury loading from mining is historically superimposed upon strong regional wetland effects, producing a combined elevation of both THg and MeHg in the Western Upper Peninsula.

A geographic enigma is that present-day atmospheric deposition of mercury in the Upper Peninsula of Michigan is low (48%) and that regional industrial emissions have declined substantially (ca. 81% reduction) relative to downstate. Mercury levels should be declining. However, state (MDEQ) surveys of rivers and lakes revealed elevated total mercury (THg) in Upper Peninsula waters and sediment relative to downstate. Moreover, Western Upper Peninsula (WUP) fish possess higher methyl mercury (MeHg) levels than Northern Lower Peninsula (NLP) fish. A contributing explanation for elevated THg loading is that a century ago the Upper Peninsula was a major industrial region, centered on mining. Many regional ores (silver, copper, zinc, massive sulfides) contain mercury in part per million concentrations. Copper smelters and iron furnace-taconite operations broadcast mercury almost continuously for 140 years, whereas mills discharged tailings and old mine shafts leaked contaminated water. We show that mercury emissions from copper and iron operations were substantial (60–650 kg per year) and dispersed over relatively large areas. Moreover, lake sediments in the vicinity of mining operations have higher THg concentrations. Sediment profiles from the Keweenaw Waterway show that THg accumulation increased 50to 400-fold above modern-day atmospheric deposition levels during active mining and smelting operations, with lingering MeHg effects. High MeHg concentrations are geographically correlated with low pH and dissolved organic carbon (DOC), a consequence of biogeochemical cycling in wetlands, characteristic of the Upper Peninsula. DOC can mobilize metals and elevate MeHg concentrations. We argue that mercury loading from mining is historically superimposed upon strong regional wetland effects, producing a combined elevation of both THg and MeHg in the Western Upper Peninsula.

Bythotrephes longimanus, an invasive zooplankter from Eurasia, has caused severe declines in native zooplankton communities in Rainy and Kabetogama lakes in northern Minnesota. Both lakes have experienced a 40–60% decrease in peak summer zooplankton biomass following B. longimanus establishment around 2006–2007. In these lakes, yellow perch (Perca flavescens) are a key fishery species, and young-of-the-year (YOY) yellow perch are mainly planktivorous during their first summer. This led to concern that their growth could be detrimentally affected by the depletion of zooplankton forage. We used seining data to compare growth rates of YOY yellow perch before (2001–2005) and after (2008–2012) B. longimanus establishment in Rainy and Kabetogama lakes. Nearby Lake Vermilion, assumed to have been unaffected by B. longimanus during this time period, was used as a reference for natural variation in YOY growth in the region. YOY yellow perch length was modeled as a linear function of cumulative growing degree days (GDD) throughout the summer, and the slope of the relationship was compared between pre- and post-B. longimanus time periods for the three study lakes. The two lakes with B. longimanus showed similar decreases in YOY yellow perch growth rate relative to GDD, whereas Lake Vermilion showed no evidence of a decline in growth rates during this period. The reduction in growth rates resulted in an approximate 10% decrease in mean length of YOY yellow perch at the end of the summer after B. longimanus establishment, which could lead to further effects of this invasive zooplankter at higher trophic levels.

Do aquatic predator and prey species interact strongly enough to foster specialized coevolutionary feedbacks, or are interactions strongly asymmetrical, with prey species responding much more strongly and to multiple threats? Here we utilize prey induction to measure the strength of interactions around a reciprocal arms race candidate (Epischura-Bosmina). When prey (Bosmina) are transferred from predator-poor to predator-rich environments, defensive spines increase in length to achieve a plateau after 12-16 d (1-2 generations). Spine lengths are reversible with predator addition and removal, confirming developmental induction as the major short-term response. Laboratory assays reveal major geographic variation, implying active evolution. Responses range from almost no spine elongation where Epischura is historically absent (Europe), to major elongation where the predator and prey are in prolonged contact (Laurentian Great Lakes). Trade-offs (i.e., loss of competitive ability) can be related to spine lengths of the prey species. However, induction is not exclusive to Epischura, as a collection of invertebrate predators also induce spine elongation. Bosmina responses to individual predator species are different, implying active recognition of multiple predation threats in nature. The absence of induction responses to some exotics (e.g., Bythotrephes) may help explain disproportionate food web impacts. Both revelations underscore the importance of ongoing evolution in aquatic communities.

The spiny cladoceran (Bythotrephes longimanus) is an invasive, predaceous zooplankter that is expanding from Great Lakes coastal waters into inland lakes within a northern latitudinal band. In a large, Boundary Water lake complex (largely within Voyageurs National Park), we use two comparisons, a 2-year spatial and a 12-year temporal, to quantify seasonal impacts on food webs and biomass, plus a preliminary calculation of secondary production decline. Bythotrephes alters the seasonal biomass pattern by severely depressing microcrustaceans during summer and early fall, when the predator is most abundant. Cladoceran and cyclopoid copepods suffer the most serious population declines, although the resistant cladoceran Holopedium is favored in spatial comparisons. Microcrustacean biomass is reduced 40–60 % and secondary production declines by about 67 %. The microcrustacean community shifts towards calanoid copepods. The decline in secondary production is due both to summer biomass loss and to the longer generation times of calanoid copepods (slower turnover). The Bythotrephes "top-down" perturbation appears to hold across small, intermediate, and large-sized lakes (i.e. appears scale-independent), and is pronounced when Bythotrephes densities reach 20–40 individuals L−1. Induction tests with small cladocerans (Bosmina) suggest that certain native prey populations do not sense the exotic predator and are "blind-sided". Failure of prey to deploy defenses could explain the disproportionate community impacts in New World versus Old World lakes.

To examine issues of mercury contamination in lake sediments and fish, we require insight into historic sources of mercury and details of watershed methyl mercury (MeHg) cycling. Modern-day National Atmospheric Deposition Program (NADP) estimates of atmospheric mercury deposition in the upper Midwest region range from 4–10μg/m2/y (wet only) to 5–30μg/m2/y (gross deposition). Sedimentary records from scattered Michigan lakes, removed from mining sites, record around 5–24μg/m2/y modern THg deposition. However, these values are not representative of historic deposition near mining sites. On the Keweenaw Peninsula, mercury occurs naturally in copper ores and was discharged by smelting and stamp mill (tailings) operations. Here we examine mercury fluxes into two lakes (Portage and Torch Lake, portions of the Keweenaw Waterway) off Lake Superior, part of the previous Torch Lake Superfund site. Total mercury fluxes document greatly enhanced mercury loading (mean ca. 1590μg/m2/y; peaks of 5120 to 21,300μg/m2/y) during the height of copper mining (1880–1930), followed by a rapid decline once activities ceased. Methylmercury profiles appear to document both current methylation and historic methylation during mining operations. Time differences in MeHg and THg profiles may relate to watershed delivery time lags, toxic effects of copper on methylating bacteria, or to stratigraphic mobility. Whereas rapid sedimentation and lowered copper flux are promoting ecosystem recovery in Portage Lake, slower burial by organic-rich sediments is enhancing metal concentrations in Torch Lake sediments.

Summary The effects of the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriformis bugensis (quagga mussel) on aquatic ecosystems, including Lake Michigan, are a topic of current interest to scientists and resource managers. We hypothesised that the winter–spring phytoplankton bloom in Lake Michigan is reduced at locations where the fraction of the water column cleared per day by Dreissena filter feeding approached the net growth rate of phytoplankton, when the water column was not stratified. To test this hypothesis, we compared the spatial distribution of Dreissena filter‐feeding intensity (determined from geostatistical modelling) to the spatial distribution of chlorophyll (determined from satellite remote sensing). To map the spatial distribution of Dreissena biomass and filter‐feeding intensity, we developed a geostatistical model based on point observations of mussel biomass measured in Lake Michigan in 1994/1995, 2000, 2005 and 2010. The model provided fine‐scale estimates of the spatial distribution of biomass for the survey years and provided estimates, with their uncertainty, of total biomass lakewide and within subregions. The approach outlined could be applied more generally to map the distribution of benthic biota in lakes from point observations. Total biomass of Dreissena in Lake Michigan, estimated from the geostatistical model, increased significantly over each five‐year period. The total biomass in units of 106 kg ash‐free dry mass (AFDM) (with 90% confidence interval) was 6 (4–8) in 1994/1995, 18 (14–23) in 2000, 408 (338–485) in 2005 and 610 (547–680) in 2010. From 1994/1995 to 2005, increases were observed in all regions of the lake (northern, central and southern) and in all depth zones (<30, 30–50, 50–90 and >90). However, from 2005 to 2010, for depths of <50 m, biomass declined in the northern region, remained constant in the central region and increased in the southern region; biomass continued to increase in all three lake regions for depths >50 m. The filter‐feeding intensity of Dreissena exceeded the benchmark spring phytoplankton growth rate of 0.06 day−1 in 2005 for depths <50 m (lakewide). In 2010, the filter‐feeding impact exceeded 0.06 day−1 within depths <90 m (lakewide), which greatly increased the spatial area affected relative to 2005. A regression analysis indicated a significant relationship between the reduction in satellite‐derived chlorophyll concentration (pre‐D. r. bugensis period to post‐D. r. bugensis period) and spatially co‐located filter‐feeding intensity (fraction of water column cleared per day) during periods when the water column was not stratified (December to April).

The Chapter 4.17 has described the geological evolution of the Great Lakes and their hydrology and introduced selected features of lake physics, chemistry, and biology. In this chapter, two of the most important pollutant classes in the Great Lakes, nutrients and persistent bioaccumulative toxins, and biogeochemically mediated interactions between water, atmosphere, and lake sediments are examined. Next, the role of satellite remote sensing in enhancing our understanding these features of lake behavior is reviewed. Finally, policy and the regulatory environment, the bases for management of sustainable futures is looked at. As with the previous chapter, two key points are emphasized: (1) we should look to nature before the fact for help in differentiating sustainable and unsustainable practices and (2) it is critical that we increase our awareness of those things that ‘we don't know we don't know’ about the response of the Great Lakes to human perturbation. Adoption of an outlook that embraces an ethic, sensitivity, and understanding represents an excellent start to ensuring a sustainable future for these Great Lakes.

Thirteen years of SeaWiFS data (1998–2010) from the early spring isothermal period (March–April) were used to determine trends of water attenuation coefficient (KdPAR), chlorophyll a (Chl a), Photosynthetic Available Radiation (PAR), and modeled primary production in southern Lake Michigan. Surface PAR values remained unchanged between 1998 and 2010, but there was an 18–22% drop in KdPAR during the March/April isothermal period as water clarity increased. This transparency increase was accompanied by a 41–53% decline in Chl a concentration (μg·L−1) and a 42–46% decline in modeled primary production (Great Lakes Primary Production Model). These changes were most pronounced in 2001–2003 which coincided with the period of initial colonization of the quagga mussels. Statistically significant spatial differences were noted in Chl a (μg·L−1) concentrations between mid-depth (z=30–90m deep), and offshore (z>90m deep) waters. Chl a concentrations in the mid-depth region (30–90m) decreased at a higher rate compared to offshore waters (>90m) likely as a result of filtration activities of quagga mussel.