Jezerce

Klod Mone, 1916—1919

Jezerce je površina napunjena vodom, bilo prirodno ili veštački, koja je obično manja od jezera. Može se pojaviti prirodno u plavnim područjima kao deo rečnog sistema, ili može biti donekle izolovana depresija (kao što je vernalni bazen ili prerijska jama). Može da sadrži plitku vodu s močvarnim i vodenim biljkama i životinjama.

Jezerce u Svažinicama, Poljska

Činioci koji utiču na vrstu života u jezercetu obuhvataju dubinu i trajanje nivoa vode, nivo hranjivih materija, zasenčenost, prisutnost ili odsutnost ulaza i ispusta, učinak ispašnih životinja i saliniteta.

Pond at Cornjum, Netherlands

Ponds are small bodies of freshwater with shallow and still water, marsh, and aquatic plants. Ponds can be created by a wide variety of natural processes (e.g. on floodplains as cutoff river channels, by glacial processes, by peatland formation, in coastal dune systems, by beavers), or they can simply be isolated depressions (such as a kettle hole, vernal pool, prairie pothole, or simply natural undulations in undrained land) filled by runoff, groundwater, or precipitation, or all three of these. They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film. The size and depth of ponds often varies greatly with the time of year; many ponds are produced by spring flooding from rivers. Ponds may be freshwater or brackish in nature. 'Ponds' with saltwater, with a direct connection to the sea that maintains full salinity, would normally be regarded as part of the marine environment because they would not support fresh or brackish water organisms, so not really within the realm of freshwater science.

Ponds are usually by definition quite shallow waterbodies with varying abundances of aquatic plants and animals. Depth, seasonal water level variations, nutrients fluxes, amount of light reaching the ponds, the shape, the presence of visiting large mammals, the composition of any fish communities and salinity can all affect the types of plant and animal communities present. Food webs are based both on free-floating algae and upon aquatic plants. There is usually a diverse array of aquatic life, with a few examples including algae, snails, fish, beetles, water bugs, frogs, turtles, otters and muskrats. Top predators may include large fish, herons, or alligators. Since fish are a major predator upon amphibian larvae, ponds that dry up each year, thereby killing resident fish, provide important refugia for amphibian breeding. Ponds that dry up completely each year are often known as vernal pools. Some ponds are produced by animal activity, including alligator holes and beaver ponds, and these add important diversity to landscapes.

Klasifikacija

The technical distinction between a pond and a lake has not been universally standardized. Limnologists and freshwater biologists have proposed formal definitions for pond, in part to include 'bodies of water where light penetrates to the bottom of the waterbody,' 'bodies of water shallow enough for rooted water plants to grow throughout,' and 'bodies of water which lack wave action on the shoreline.' Each of these definitions are difficult to measure or verify in practice and are of limited practical use, and are mostly not now used. Accordingly, some organizations and researchers have settled on technical definitions of pond and lake that rely on size alone.

Vegetated pond within the sand dunes of the Lençóis Maranhenses National Park, Brazil

Some regions of the United States define a pond as a body of water with a surface area of less than 10 acres (4.0 ha). Minnesota, known as the "land of 10,000 lakes", is commonly said to distinguish lakes from ponds, bogs and other water features by this definition, but also says that a lake is distinguished primarily by wave action reaching the shore. Even among organizations and researchers who distinguish lakes from ponds by size alone, there is no universally recognized standard for the maximum size of a pond. The international Ramsar wetland convention sets the upper limit for pond size as 8 hectares (80,000 m²; 20 acres). Researchers for the British charity Pond Conservation (now called Freshwater Habitats Trust) have defined a pond to be 'a man-made or natural waterbody that is between 1 m²(0.00010 hectares; 0.00025 acres) and 20,000 m² (2.0 hectares; 4.9 acres) in area, which holds water for four months of the year or more.' Other European biologists have set the upper size limit at 5 hectares (50,000 m²; 12 acres).

In North America, even larger bodies of water have been called ponds; for example, Crystal Lake at 33 acres (130,000 m²; 13 ha), Walden Pond in Concord, Massachusetts at 61 acres (250,000 m²; 25 ha), and nearby Spot Pond at 340 acres (140 ha). There are numerous examples in other states, where bodies of water less than 10 acres (40,000 m²; 4.0 ha) are being called lakes. As the case of Crystal Lake shows, marketing purposes can sometimes be the driving factor behind the categorization.

The Pond in Central Park in Manhattan, New York City

In practice, a body of water is called a pond or a lake on an individual basis, as conventions change from place to place and over time. In origin, a pond is a variant form of the word pound, meaning a confining enclosure. In earlier times, ponds were artificial and utilitarian, as stew ponds, mill ponds and so on. The significance of this feature seems, in some cases, to have been lost when the word was carried abroad with emigrants. However, some parts of New England contain "ponds" that are actually the size of a small lake when compared to other countries. In the United States, natural pools are often called ponds. Ponds for a specific purpose keep the adjective, such as "stock pond", used for watering livestock. The term is also used for temporary accumulation of water from surface runoff (ponded water).

There are various regional names for naturally occurring ponds. In Scotland, one of the terms is lochan, which may also apply to a large body of water such as a lake. In the South Western parts of North American, lakes or ponds that are temporary and often dried up for most parts of the year are called playas.  These playas are simply shallow depressions in dry areas that may only fill with water on certain occasion like excess local drainage, groundwater seeping, or rain.

Formiranje

Pond formation through seeping groundwater in South Tufa, California

Any depression in the ground which collects and retains a sufficient amount of water can be considered a pond, and such, can be formed by a variety of geological, ecological, and human terraforming events.

Ornamental pond with waterfall in Niagara Falls Rock Garden

Natural ponds are those caused by environmental occurrences. These can vary from glacial, volcanic, fluvial, or even tectonic events. Since the Pleistocene epoch, glacial processes have created most of the Northern hemispheric ponds; an example is the Prairie Pothole Region of North America. When glaciers retreat, they may leave behind uneven ground due to bedrock elastic rebound and sediment outwash plains. These areas may develop depressions that can fill up with excess precipitation or seeping ground water, forming a small pond. Kettle lakes and ponds are formed when ice breaks off from a larger glacier, is eventually buried by the surrounding glacial till, and over time melts. Orogenies and other tectonic uplifting events have created some of the oldest lakes and ponds on the globe. These indentions have the tendency to quickly fill with groundwater if they occur below the local water table. Other tectonic rifts or depressions can fill with precipitation, local mountain runoff, or be fed by mountain streams. Volcanic activity can also lead to lake and pond formation through collapsed lava tubes or volcanic cones. Natural floodplains along rivers, as well as landscapes that contain many depressions, may experience spring/rainy season flooding and snow melt. Temporary or vernal ponds are created this way and are important for breeding fish, insects, and amphibians, particularly in large river systems like the Amazon. Some ponds are solely created by animals species such as beavers, bison, alligators and other crocodilians through damning and nest excavation respectively. In landscapes with organic soils, local fires can create depressions during periods of drought. These have the tendency to fill up with small amounts of precipitation until normal water levels return, turning these isolated ponds into open water.

Literatura

• Keddy, Paul A. (2010). Wetland Ecology: Principles and Conservation. Cambridge University Press. ISBN 978-0-521-73967-2. 
• Clegg, John (1986). The New Observer's Book of Pond Life. Frederick Warne. стр. 460. ISBN 978-0-7232-3338-1. 
• Clegg, J. (1986). Observer's Book of Pond Life. Frederick Warne, London. 460p.
• Hughes, F.M.R. (ed.). (2003). The Flooded Forest: Guidance for policy makers and river managers in Europe on the restoration of floodplain forests. FLOBAR2, Department of Geography, University of Cambridge, Cambridge, UK. 96 p.[1]
• Environment Canada. (2004). How Much Habitat is Enough? A Framework for Guiding Habitat Rehabilitation in Great Lakes Areas of Concern. 2nd ed. 81 p.[2]
• Keddy, P.A. (2010). Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p.
• Herda DJ (2008) Zen & the Art of Pond Building Sterling Publishing Company. ISBN 978-1-4027-4274-3..
• W.H. MacKenzie and J.R. Moran (2004). Wetlands of British Columbia: A Guide to Identification. Ministry of Forests, Land Management Handbook 52.

Spoljašnje veze

• Dugout Pond Aeration Flash Animation
• North American Water Garden Society
• WikiHow: Build A Water Garden in 20 Steps
• Pond Conservation: Advice on garden ponds for wildlife