Charles E. Herdendorf

Large Lakes of the World

Abstract An inventory of the distribution, origin, and morphometry of the worlds large lakes has been undertaken. Natural lakes, fresh and salt, with a surface area greater than 500 km 2 are included; 253 such lakes have been identified. Large lakes occur on all continents, except Antarctica, but nearly half of them (48 percent) are found in North America and most of these lie above the 40th parallel, attesting to the scouring action of continental glaciers. Tectonic belts, such as the Riff Valley of east Africa and the Lake Baikal region of Siberia, are the second most common loci of large lakes. Tabular morphometric data include: surface area, drainage basin, elevation, mean and maximum depth, volume, length and breadth, and orientation of longest axis. These data show that the large lakes of the world occupy a surface area of 1,456,000 km 2 and they have an estimated volume of 202,000 km 3 . Large lakes account for approximately 90 percent of the total surface area and volume of water held in all lakes of the world. Revisions and supplements to the data presented are welcomed.

A geomorphic classification of estuaries and its application to coastal resource management—A New Zealand example

Abstract This paper describes an estuarine classification scheme developed for a wide variety of New Zealand estuaries that has application to coastal resource management. Estuaries are grouped using existing geological and topographic map and air photograph data bases complimented by field reconnaissance. Estuaries are grouped into five classes, and these reflect the primary process that shaped the basin that forms the estuary namely: (1) fluvial erosion, (2) marine/fluvial erosion, (3) tectonic, (4) volcanic, and (5) glacial. These classes are subdivided on a morphologic basis into 16 types, which reflect catchment and coastal hydrologic and sedimentologic processes. Fluvial origin estuaries include unrestricted inlets, headland enclosed inlets, barrier-enclosed lagoons (double-spit, single-spit, tombolo, island and beach barriers) and river mouth (straight-banked, spit-lagoon and deltaic) types. Estuaries of marine/fluvial erosion origin are coastal embayments. Estuaries of tectonic origin include fault defined embayments (inlet width 5 km). Explosion craters are of volcanic origin, while glacial estuaries are of a glacial origin. Compound estuaries are formed from two or more of the basic types. Relationships between inlet throat dimensions and tidal prism support the scheme structure.

Great Lakes Estuaries

ConclusionsAccording to the geomorphology and physiography classification scheme for estuaries proposed by Pritchard (1967) and presented in Kennish (1986), Great Lakes estuaries can be classified as Type A: drowned river valleys or rias. The termination of Wisconsinian glaciation, which resulted in a eustatic rise in sea level of somewhat over 100 m and the formation of such Atlantic coast estuaries as Chesapeake Bay and Delaware Bay, also resulted in isostatic rebound in the northern Great Lakes region and the formation of drowned mouths of many tributaries to the lake.Based on analysis of literature and field observations, it is proposed that the term freshwater or Great Lakes estuary be applied to the drowned portion of streams entering the Great Lakes. The common denominator in virtually all definitions of estuaries is morphology, particularly the basins morphometry and the hydraulic relation of the water level contained therein to the entering stream. Where the land mass and the stream profile rise above a selected datum, the estuary begins and the river debouches. This concept can be useful in modeling water quality and physical attributes in connection with biotic, physiochemical, sedimentary and contemporary geological processes. It can also be applied in the Great Lakes as a practical way of identifying the margins of the lake, thus clarifying ownership disputes and clouded issues where demarkation of lake and river arise.

Lake Erie Coastal Wetlands: an Overview

Abstract Coastal wetlands of Lake Erie fall into three categories, depending on the type of protection available to the wetland vegetation: (1) coastal lagoons behind barrier beaches, (2) managed marshes protected by earthern and rip-rap dikes, and (3) estuarine tributary mouths. At one time the most important protection was that afforded by barrier bars or other natural shoreline features which formed quiet lagoons and embayments. Very few natural wetlands of this type still exist in Lake Erie. Most of the lagoon-type coastal marshes, if they have not been drained or filled or engulfed by the lake, have been replaced by the second type: managed-waterfowl marshes which are now protected by earthen rip-rap dikes. The third type of protection is the natural isolation from lake storms provided by the estuaries of virtually all of the tributaries entering Lake Erie, particularly at the western end. Large wetlands have developed along most of the estuaries where disturbance has been minimal. Estuarine coastal marshes currently form the majority of the naturally protected wetlands bordering western Lake Erie.

A Post Audit of a Lake Erie Eutrophication Model

Abstract A post audit of a eutrophication-dissolved oxygen model of Lake Erie is presented. The model had been calibrated using data from 1970 and 1975. Projections were then made for use in establishing the IJC target loadings for phosphorus that would essentially eliminate the anoxia in the central basin. In the latter 1970s the phosphorus discharges to Lake Erie dropped substantially due to increased removal from point sources. The observed response of the lake to this change in loading is compared to the predicted response. A 10-year computation from 1970 to 1980 is made using measured lake loadings. Concentrations of total and dissolved phosphorus, nitrate, chlorophyll, dissolved oxygen, and anoxic area are compared to observations. Both agreements and deviations are examined. It is concluded that the IJC target loadings were reasonably accurate forecasts of the loadings required to achieve the goal of elimination of anoxia.

Growth Dynamics of Cladophora Glomerata in Western Lake Erie in Relation to Some Environmental Factors

Cladophora was monitored at two sites in western Lake Erie during 1979 and 1980 as part of a lake-wide Lake Erie Cladophora Surveillance Program. Two distinctive zones within the littoral region were colonized by the alga, the eulittoral (splash zone) and infralittoral (defined in the present study as the 0.5–4 m depth zone). Cladophora of the eulittoral zone became established in May and remained present until late fall. The infralittoral zone Cladophora exhibited a bimodal growth pattern related to the seasonal temperature regime, with growth occurring from April to July and again from September to November. The infralittoral zone supported the largest share of biomass, which resulted in nuisance accumulations upon the beaches in the island region. Peak biomass was observed from mid-June to early July, obtaining maximum values of 102 gDW/m2 and 214 gDW/m2 for the 1979 and 1980 seasons, respectively. The depth to which Cladophora colonized was limited by light availability; maximum depth of growth occurred between 2 and 4 m in western Lake Erie due to the turbid nature of the basin. Phosphorus and nitrogen were not limiting to Cladophora growth in western Lake Erie; tissue nutrients remained above the critical levels defined by Gerloffand Fitzgerald (1976) throughout the season.

Revised Lake Erie Postglacial Lake Level History Based on New Detailed Bathymetry

Abstract Holocene lake level history and paleogeography of Lake Erie are re-interpreted with the aid of new bathymetry, existing water budget data, and published information. Morphology and elevation of present and former shoreline features (sand ridges, forelands, spits, bars, and fans) record the water level at which they were formed. Of eighteen such features observed in Lake Erie, six occur nearshore and were formed at or near present lake level, and twelve features apparently formed at lower lake levels. It seems likely that lake level fell below the level of the outlet sill during the 9–6 ka climate optimum, when warmer and drier conditions prevailed. During such times lake level likely rose and fell as controlled by the water budget, within a window of constraint imposed by increases and decreases in evaporation, which would have varied directly with lake surface area. Near Buffalo, possible shoreline features occurring 3–6 km offshore at depths of 9–12 m could have formed at lower lake levels. Annual water volumes in each term of the water budget, (runoff, precipitation, and evaporation) are large relative to the volumetric capacity of Lake Erie itself. Such events as introduction of even a modest amount of upper Great Lakes water, or the onset of cooler and less dry climate conditions, could cause significant, rapid, lake level rise. Schematic reconstructions illustrate changing paleogeography and a Holocene lake level history which has varied with: blocking/ unblocking of outlet sills; erosion of outlet sills; distance from outlet sills; differential isostatic rebound; upper Great Lakes drainage flowing into or bypassing the lake; and climate-driven water budget of the Lake Erie drainage basin.

A Greenland Shark from the Wreck of the SS Central America at 2,200 Meters

Abstract The three-masted, wooden-hulled steamship Central America sank in 1857 during a hurricane 370 km east of Savannah, Georgia. During a recovery project begun in 1988, the unmanned research submersible Nemo equipped with video and still cameras filmed a 6-m-long, male Greenland shark Somniosus microcephalus at the 2,200-m-deep wreck site. The depth is 1,000 m deeper than the maximum reported depth for this species. The Savannah location is 440 km further south than the previously known North Carolina records for the Greenland shark.

Limnetic Larval Fish in the Ohio Portion of the Western Basin of Lake Erie, 1975–1976

Abstract A total of 19 taxa of larval fish was collected with metered plankton nets in Ohio and adjacent Ontario waters of the western basin of Lake Erie. Analysis of yellow perch, Perca flavescens , collection data indicates that shallow inshore areas serve as important nursery areas for this species. Collection of larvae provides evidence of relict breeding populations of lake whitefish, Coregonus clupeaformis , and sculpin ( Cottus sp.) in the western basin.

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.