Lakes and other Aquatic Habitats

Lake Habitat Tour

One way of thinking of lakes and ponds is that they are merely slow spots in streams and rivers. This is Avalanche Lake in Glacier National Park, Montana. Water from the glaciers in the background pool temporarily in this depression (which was scooped out by a glacier long ago) before cascading down through the mountains in the waters of Avalanche Creek (below left).

We'll stay up in the mountains for a while. High on the mountaintops cirque lakes form in small depressions gouged out by glacial ice (above right). These lakes are frozen for much of the year, but spring to life with snowmelt in the very brief alpine summer. The cirque lakes pictured here are just outside Yellowstone National Park; the picture was taken in late September just before a snowstorm. To the right is May Lake, high in the Sierra Nevada of California in Yosemite National Park. This lake receives its water from snowmelt off the adjacent rocky slopes. As you might guess, the snow and rain are not able to dissolve many minerals from the igneous rocks of the Sierra and as a result, May Lake is oligotrophic. Oligotrophic means having few nutrients just as oligarchy is rule by a few people. These high lakes have exceptionally clear water (see the curve for Lake Tahoe in the graph below). On the other hand, with few nutrients there is also little production and these lakes cannot support much biomass. Also, with few dissolved minerals in them, such high-altitude lakes often have little buffering capacity, and are thus very susceptible to acid precipitation.

Haley Lake, Ontario, Canada
Yellowstone Lake, Yellowstone National Park, Wyoming	Here are some more oligotrophic lakes. It's not necessary to be high up in the mountains for a lake to be oligotrophic. The nature of the land in the basin is the important thing. Haley Lake is in Ontario not too far north of Kingston. It is a long narrow gouge in the ancient Canadian Shield, some of the oldest rocks on the planet, composed mostly of granite. The lake is indicated by the red arrow in the satellite image above. I can attest that while this lake might be oligotrophic (or at least it was in the 1970's), it did have quite a fish population and was well worth the trouble to haul a boat back several miles from the road (white line). From a boat, it was possible to see the bottom in 20 feet of water. Nearby Beaver Lakes (green arrow) was much more eutrophied (nutrient rich), as you might expect from its position in a lower area with many farm fields which tended to lose nutrients into the lakes.
Yellowstone Lake and MacDonald Lake, both being situated in National Parks, are at least spared the runoff from agricultural fields. On the other hand, all those visitors to the parks have to go to the bathroom, and one wonders where all that sewage winds up, as septic systems are notoriously ineffective in rocky soils. Nutrients from sewage are, along with fertilizer runoff, major causes of cultural eutrophication. The term cultural eutrophication needs some explaining. It should first be noted that the process of eutrophication - by which a lake accumulates nutrients and gradually moves from oligotrophic to mesotrophic to eutrophic - is perfectly natural and proceeds, albeit very slowly, even if humans aren't around. It may take tens of thousands of years for a lake to make this transition as it gradually fills in. Cultural eutrophication occurs when humans accelerate the natural process of eutrophication by adding nutrients and sediment through careless farming and construction, logging, sewage and other environmental insults. Where they still exist, oligotrophic lakes are jewels. The picture of the bottom of Jenny Lake in the Grand Teton National Park (below) was taken through several feet of water, yet it looks as though the rocks are on dry land, so clear is the water. Only the tufts of algae give the water away in this photo.	MacDonald Lake, Glacier National Park, Montana
Jenny Lake (left), Grand Teton National Park, Wyoming (right, Jackson Lake in Foreground)
Sandy Stream Pond, Baxter State Park, Maine
Moving back east, lets visit Sandy Stream Pond in Baxter State Park, Maine, as we did in 1998. This shallow pond lies at the base of several mountains. If you look carefully at the picture above, you can see a photographer taking pictures of a bull moose (above right). Swarming about the moose, and not really that discernible at this resolution, are adult black flies, the bane of the boreal forest. A larval blackfly is shown to the right. The larvae do not normally inhabit ponds or lakes, but prefer flowing water. There, they spin a circlet of silk which they attach to a rock. They then attach themselves to the silk through means of tiny hooks on their posteriors, and lay back in the current to filter food from the water with the help of antennae heavily modified to collect tiny particles from the water. Adult female flies must find a blood meal in order to obtain the protein necessary to produce eggs. Moose are an attractive target, and it has been suggested that moose spend a lot of time in the water just to avoid the flies (moose also get a lot of their food from the aquatic plants in shallow ponds). This bull moose is growing his antlers; the bony structures are currently covered with "velvet" - a layer of skin and blood vessels which nourishes the developing antler and which will be scraped off on a tree when the antlers have reached full size in the fall.
Lake Superior	Put-in-Bay, Lake Erie
The Lauretian Great Lakes - Superior, Huron, Michigan, Erie and Ontario - comprise one of the greatest freshwater systems on the planet. Ranging from deep, cold oligotrophic Lake Superior in the north to shallow, eutrophic Lake Erie in the south, there are a range of aquatic habitats here. The size of the lakes means they have processes that are sometimes more akin to what happens in the ocean than what you would expect in a lake. For instance, the extensive sandy spit off the southern point of Pelee Island (lower right) moves about mush the same way that barrier islands on the eastern coast of the US do. On the other hand, the western part of Lake Erie is very shallow - only about 10m or so deep on average - and spotted with islands, including Pelee Island, South Bass Island, and Gibraltar Island, home of the Franz Theodore Stone Laboratory, operated by Ohio State University. The oldest biological field station in the United States, Stone Lab has done much to document the changes in Lake Erie as developing agriculture in Northwestern Ohio, as well as burgeoning cities such as Detroit, all added nutrients to the lake, culminating in extensive areas of anoxic sediments in the 1950's and the widely reported "death" of Lake Erie (actually the lake had more living biomass then than it did at any other time). The western part of Lake Erie is often called river like because the invertebrate species and plankton dynamics are more like a wide river than a lake.	Gibraltar Island, Stone Research Laboratory, Put-in-Bay, Lake Erie
Daphnia sp.	Pelee Island, Ontario Canada
*Aboard the RV Hydra* on Lake Erie.**	*A real Hydra.*
Burrowing Mayfly (Ephemeridae). These larvae dominated the bottom sediments of Lake Erie until it went anoxic in the fall of 1953, killing the approximately 240 mayfly larvae per square meter on most of the bottom of the lake.	Lake Erie has been the site of some exciting research into not only eutrophication, but the effects of introduced species as well. In the 1980's, Stone Lab operated the Research Vessel Hydra to study the lake in more detail. About that time, the lake was still turbid with algal growth, although efforts to stem the flow of nutrients into the lake were beginning to have an effect. The mayflies, which had once covered the bottom of the lake but which were almost completely replaced by midge larvae in the mid 1950's, began to be found in swarms once again. Less phosphorous coming into the lakes from farms and untreated sewage meant smaller algal blooms; algal blooms, when they die and decompose use up oxygen and kill sensitive organisms such as the mayflies. Thus, the presence of the mayflies is a sign of relative ecosystem health. Burrowing Mayfly adults swarming on the front of the Stone Lab building, 1981.
Midge Larvae (Chironomidae). Midge larvae largely replaced the mayflies on the bottom of Lake Erie from 1953 through the 1990's, when the mayflies began a strong comeback. The red is hemoglobin, which allows the midge larvae to attract and store oxygen, a useful trait in anoxic sediments.	Burrowing Mayfly adults swarming on the front of the Stone Lab building, 1981. More on the Mayflies.
Sea Lamprey (Pacific, not Atlantic) Zebra Mussels.	Among the invasive species that have entered Lake Erie, few have been as notorious as the zebra mussels or the sea lamprey. The sea lamprey entered the lake in the 1800's after the construction of the Welland ship canal between Lakes Erie and Ontario effectively removed the considerable barrier of Niagara Falls for lampreys attempting to move upstream. Adult Sea Lampreys feed by attaching their mouths to the side of a large fish and rasping a hole in it. The lampreys were widely vilified for destroying stocks of important commercial fish in Lake Erie, but in truth it was probably only a minor insult compared to the industrial pollution and cultural eutrophication striking the lake at the same time. Chemical lampricides to kill the larval lampreys as they filter-feed in tributary Lake Erie streams also adversely affect native species, adding to the detrimental impact of this invader. The zebra mussel (Dreissena polymorpha) entered Lake Erie around 1988, probably as a result of a ship from Europe discharging freshwater ballast upstream in Lake St. Clair a few years earlier. These mussels bind to virtually every hard substrate - rocks, pilings, boats, water pipes and intakes, even native mussels and large dragonfly nymphs! From these sites they filter the water for food, and are very efficient at removing algae and other suspended particles from the water. The apparent increase in clarity of Lake Erie from 1974 to 1995 in the graph at left is largely the result of huge numbers of zebra mussels. This has been a mixed blessing for the lake. Greater water clarity is good for some species, but many native species have been hurt and the overall effect remains to be seen - if it can ever be sorted out from the cascading effects of pollution, pollution control, and a parade of invasive species. One web page lists these invasive species for the great lakes: Cercopagis pengoi \| Rusty Crayfish \| Spiny Water Flea, Common Carp \| Goby \| Ruffe \| Sea Lamprey \| White Perch Zebra Mussel Curly-leaf Pondweed \| Eurasian Watermilfoil \| Flowering Rush \| Purple Loosestrife - and there are a lot more. Some species were perfectly happy in Lake Erie, even when it was polluted, once again the pronouncement of the "death" of Lake Erie was a bit premature. The cyanobacterium *Plectonema woolei* in turbid Lake Erie has virtually all the known accessory pigments. Grown under low-light conditions (it can grow in a refrigerator, apparently getting enough light when the door is opened occasionally) it is black in color. Its LCP in Lake Erie was often about 10 m, where visibility to the human eye was measured in cm. This cyanobacterium was well adapted for the turbid days in Lake Erie. A friend of mine was studying it, and as a result we spent a lot of time diving in the lake and looking for it, as well as trawling for it with our specially designed Plectonema sampler (below right). I often wonder what happened to the Plectonema now that the Lake is much clearer as the result of the zebra mussels? What does all this tell us? Life adapts to whatever we throw at it. Pollutants, nutrients, invasive species - in all of these situations some organisms are able to survive, and, with their competitors and predators reduced by the disturbance, some of them can even thrive. The consequences of these changes, however, are usually not too obvious and rarely are to our benefit, and the effort required to clean up after ourselves is usually much greater (and more expensive) than it would have been not to create the mess in the first place. My dog knows not to go to the bathroom in its den (also known as our house) - will humans ever learn this basic fact that canines mastered hundreds of thousands of years ago?
Oscillatoria sp.; a near look alike to Plectonema woolei.	*The world-famous Plectonema* sampler. This device is now in the Smithsonian.**

OK - how about something completely different? This little lake (above) forms part of the continental divide. Water flowing out the far end flows (eventually) into the Snake and Columbia Rivers and out into the Pacific Ocean. Water flowing from the near end (a dry ditch at the edge of a parking lot, below) ends up flowing into the Yellowstone, Missouri and Mississippi Rivers and out into the Gulf of Mexico and the Atlantic Ocean. Continental divides of one sort or another are fairly common, and are often not associated with a knifelike mountain ridge, but with a low swampy area. In Akron, Ohio, Summit Lake drains to its north into the Cuyahoga River, thence Lake Erie and the St. Lawrence River to the Atlantic, and from its southern end into the Tuscarawas, Muskingum, Ohio and Mississippi Rivers into the Gulf of New Mexico. A guide in Yosemite National Park once drew her horse to a stop in a puddle which she claimed formed the divide between watersheds supplying water to San Francisco and Los Angeles. During her explanation, the horse urinated. Like dogs, sometimes horses can be really smart, or at least have a sense of the ironic.
	Horses: Smarter than they look!
Alligator Snapping Turtle (Macroclemys temminckii)	Apple Snail
Animal time! The Alligator Snapping Turtle lives in lakes and ponds in the southern United States and is the the largest freshwater turtle in the world. Note the pink structure in the mouth - it looks like a wriggling worm, and any fish that comes to investigate is going to get a surprise! The Apple Snail is a large snail that lives in the Everglades and the lakes of southern Florida. It can grow to the size of an apple, and is one of the main prey items in the diet of the endangered Snail Kite. The eggs are somewhat hard-shelled and laid above the waterline, both unusual for snails. The Bullfrog, native to the eastern US, has been introduced all over the world, and in moist places it is an invasive pest. The largest frog in North America, it is voracious and rapidly consumes native species in the areas where it has been introduced. I had a captive specimen once, who, over the course of 3 years, ate a 6" long bass, hatchling chicks, raw hamburger, a baby snapping turtle, marshmallows, lettuce, and a bunch of other stuff. The bass and the turtle were accidents (in fact, the tadpole from whence the frog sprang was intended as food for the bass and I never thought it would eat the turtle); the lettuce and marshmallows were the results of bets (I was confident that, properly presented, the frog would eat anything) and the chicks are a long story. Canada Geese were rare when I was a kid; now there are conferences on controlling them. Part of the change is due to a change in the geese themselves - fewer are migratory and more are staying resident in certain areas. By the way, snapping turtles eat goslings. An the circle is complete....	Apple Snail Eggs
*Canada Geese (Branta canadensis)*	*Bullfrog (Rana catesbeiana)*
Florida landscape with circular sinkhole lakes.	A sinkhole lake.
The landscape of peninsular Florida is dotted with lakes of a particular type - sinkhole lakes. These lakes form when water dissolves a large cavity in the underground limestone. Eventually, the cavern collapses, leaving a perfectly round hole on the surface (sometimes in the Sears store at the local shopping mall). These cavities fill with water and a sinkhole lake is born. Lake Annie is one of the cleanest of the sinkhole lakes in Florida. Protected by its location as part of the Archbold Biological Station, it hasn't suffered from the cultural eutrophication that has affected many of the lakes in Florida. As the underwater pictures attest, the water is relatively clear. However, plant life is abundant, and the leaves waiting to decompose on the bottom are another source of nutrients waiting to be tapped. Indeed, diving in Lake Annie I have seen algal blooms suspended in the water column at places where the water density changes abruptly.	Lake Annie, a sinkhole lake at the Archbold Biological Station.
Underwater in Lake Annie.	The surface of Lake Annie.

	The pond at the left (actually a turning basin on the Ohio and Erie Canal near Coshocton, Ohio) is eutrophic. The green water, rich with planktonic algae, as well as the floating mats of algae, are, in this case, diagnostic. Such a pond supports quite a bit of life, but there are places which are even more eutrophic. Sewage lagoons, say on a pig farm, may be hypereutrophic. Dissolved oxygen levels may be so low that the only organisms that can survive are those with special adaptations for low oxygen levels, such as the Rat-tailed Maggot (above). The "rat tail" of the maggot is actually a "snorkel", an extension of the body bearing two spiracles and attached air tubes through which the maggot breathes. By extending the snorkel to the surface, the maggot can breathe a short distance down into the anoxic, yet food-rich water.
Hungry Horse Dam	Lake Arenal
	Humans create still, or lentic habitats, from streams all the time. These are some pictures of "lakes" resulting from that practice. Dams slow the water and cause it to pool above the dam. We have many reasons for making dams - flood control, generation of electricity, storage of irrigation or drinking water, navigation, recreation, etc. Above left is the Hungry Horse Dam in Montana near Glacier National Park; a prime purpose of this dam is electric generation. Lake Arenal, in Costa Rica (above and below right) is used primarily to capture water that would otherwise run down the already water-rich Atlantic Slope of that country and send it instead to the water poor Pacific Slope - it sits on the continental divide. It also generates electricity. The large lake in Quebec, Canada (left) was formed by a dam in order to generate hydropower. The Bonneville Dam (below left) on the Columbia River generates power and backs up the Columbia to maintain water depths suitable for navigation. Dams and their effects are discussed further in the section on streams.
Bonneville Dam	Lake Arenal
Pike	Painted Turtle, *Chrysemys picta*
More animals: The pike, above, is one of the top predatory fish of a lake. Not only do they feed on other fish, but amphibians and small reptiles, birds and mammals. They are adapted to attack their prey from below. Turtles of many types are found in lakes and ponds; one of the most common across the midwestern and eastern United States is the Painted Turtle, *Chrysemys picta* ssp. Unlike some other pond and lake species, these turtles spend a lot of time basking in the sun. Basking helps them make vitamin D necessary to incorporate calcium into bone (and the shell is made of bone, so this is important), and also warms them up so that they can swim faster and catch more agile prey. Still, they really aren't much of a threat to a healthy fish in open water. Basking also reduces algal growth on the shell and reduces the load of external parasites such as leeches. The snapping turtle (Chelydra serpentina) in the picture doesn't do much basking. Unlike many other species of wildlife, painted turtles and snapping turtles have done quite well by humans; every small farm pond or large lake we build adds to their habitat, while the streams and wetlands destroyed in the process take away from the habitats of other turtles like the Spotted Turtle (Clemmys guttata). Below are two pictures of Whirlygig Beetles (Gyrinidae, probably Dineutes). These beetles are fascinating for several reasons. First, they live between two worlds on the surface of the water, rowing rather rapidly with their flattened legs. Their two compound eyes are divided, with one set looking up at the aerial world and the other down underwater; predators could come from either direction. They secrete a chemical into the water to change the surface tension; this allows them to move faster and the Navy has studied them with an eye towards applying this to ships and submarines. Also, they are quite social, and produce an aggregating hormone which reportedly is similar to the aroma of Juicy Fruit gum. After handling the beetles, I'm more reminded of the smell of cucumbers, but that might be a defensive secretion I'm smelling.	*Spotted Turtle (Clemmys guttata)*
Whirlygig Beetles (Gyrinidae)	Whirlygig Beetles (Gyrinidae)

Oxbow lakes form in floodplains. As a river ages, it starts to form large loops (oxbows) in its floodplain; eventually oxbows are cut off from the main channel to form an oxbow lake (right). Lying in the rich sediments of a floodplain, such lakes are usually eutrophic from the start, and tend to fill in rather quickly, geologically speaking. The surrounding floodplain is often used for agriculture and often from an aerial vantage you can see the remains of former oxbow lakes reflected in curved shapes on the ground (above). During times of flood (below right), oxbow lakes may be connected back to the river channel. During floods, they receive fresh infusions of sediment, nutrients and fish. The former two hasten the demise of the oxbow as the sediment and the plants grown from the nutrients act to fill in the pond. In the meantime, however, these ponds are often very productive of everything from fish to waterfowl. The picture of the Water Lily below is gratuitous.

	The dragonfly larvae to the left (Family Corduliidae) captures small prey items in the basket-shaped labial palp which can be extended forward from the face by hydrostatic pressure in the blink of an eye. Dragonfly larvae may be the top predators in some fishless ponds. Fishless ponds are also home to many other species, including unique insects, crustaceans and many species of amphibians including the red-spotted newt (Notophthalmus viridescens). Do wildlife a favor and don't transport fish to every little puddle you can find; we're never going to run out of bluegills but a lot of species depend on fishless ponds.
The Great Salt Lake	The Great Salt Lake
	Finally, a real clash in habitats. The Great Salt Lake (above left), in Utah, is one of the saltiest bodies of water around. With no outlets, water flowing in from the surrounding mountains bring additional salts, which are left behind when the water evaporates. Most living organisms cannot tolerate the saltiness, but the are algae, crustaceans and insects which can, and these organisms make up the simple food chain of the lake. The dikes in the picture above divide up portions of the Great Salt Lake, and the coloration is caused by algae in the water.
The Great Salt Lake Food Chain The base of the food chain in the Great Salt Lake is phytoplankton. In the Great Salt Lake the phtyoplankton include green algae, diatoms and cyanobacteria. You can see a green color caused by algae in the photo above; other algae in the lake are reddish in color. For instance, a railroad causeway runs across the middle of the lake and reduces water flow. The northern part of the lake is more saline and supports a large population of Dunaliella salina which is red in color. The southern part is less saline and the dominant algae is Dunaliella viridis, which, as the Latin name implies, is greenish. Dunaliella viridis probably dominates in the image above, and is likely responsible for the greens in the image below. The red colored areas in the image below are evaporation basins. These are diked off from the main part of the lake and allowed to dry out so minerals can be extracted; as a result they are saltier than the main part of the lake and probably harbor a lot of Dunaliella salina. Other algae live on the bottom of the lake as well and can be an important food source. Algae in the lake are consumed by two main herbivores: brine flies and brine shrimp. These are the two main organisms able to live in the high salinity of the lake. The brine flies, below, emerge in huge numbers in the summer (the pictures below were taken in the fall when there were fewer flies and thus do not do this phenomenon justice). These flies remove a tremendous amount of organic material from the lake. I don't have a picture of the larvae, which look like small maggots and live on the bottom of the lake. When it is time to transform to the adult stage, the larvae transform into pupae, which eventually make their way to the surface. The pupal case splits open and the adult flies away. The pupal skins then wash up on the shore (below) and decompose. Once ashore, the brine flies provide food for birds and smaller creatures including this tiger beetle: Tiger beetle larvae (below) live in borrows in the soil. The larvae uses the expanded top of its head to cover the entrance to its burrow; when a small insect such as a brine fly approaches it leaps out and grabs the prey. The species pictured below is not the same as the one seen at the Great Salt Lake; these larvae were found on the shores of Lake Erie. The other (and more famous) inhabitant of the lake is the brine shrimp, which are also present in large numbers. This species, Artemia salina, is able to inhabit the salty waters of the lake, where it also feeds on algae. Towards fall, the females begin to encase their eggs in hard spherical cysts. These cysts are able to resist dessication, and are produced by the billions. Below, a female brine shrimp is shown amid a profusion of cysts (eggs). She has more eggs ready to lay in her Brood Sac. Some of the brine shrimp are bright red in color as a result of the algae they have ingested. Harvesting brine shrimp eggs is a large industry; the eggs are sold for use in feeding tropical fish and for pets - this is where we get Sea Monkeys from. Brine Shrimp Harvest
More on life in the Great Salt Lake: http://faculty.weber.edu/sharley/AIFT/GSL-Life.htm


The Great Salt Lake is know for its saltiness. On the other extreme are springs, which often have few salts dissolved in the water. To the right is a picture of the extremely clear water in a Florida spring (the picture is of the bottom of the spring taken from about 2 meters away). To the lower right is a view of the water in the spring's outflow creek. Below is a new species of blind cave crayfish recently isolated from this cave system by Terrence Tysall of the Cambrian Foundation. A former Marietta Student, Amy Gianotti (MC 1995) (center, below) is the Vice President for Science and Research at the foundation, and also works for the Florida Department of Environmental Protection.

To the right is an image of Prairie Potholes from North Dakota (or Minnesota). These small depressions were formed by glaciers; unlike the bog lakes mentioned above, prairie potholes tend to be much shallower. Many dry up in the summer and are better considered wetlands than lakes. The image to the right shows many potholes retaining water even in August of 2012, a drought year. Many others are dried up. As can be seen, agriculture is a definite threat. The potholes are critical stopovers for migrating waterfowl, whose migrations are often timed to the thawing of these potholes in the spring.

If you haven't seen the section on streams yet, perhaps this is a good time to go there.

Take a Tour of Lake Habitats Take A Tour of Wetland Habitats

Crescent Lake

Crescent Lake, a glacial lake on the Olympic Peninsula in Washington.