Floating vegetation (Fig. 2.S) : water lily, poiul 

 lily, ])oiul\vcc(l, smartweed, duckweed, and water 

 hyacinth. All c.vcept the last two are rooted in the 

 nnid, often at depths of two to three meters, and may 

 ha\e rhizomes from which long petioles extend to 

 the leaves floating on the surface. Duckweeds and 

 water hyacinths are unattached floaters, and cover 

 the surface extensively in some localities. 



Emergent vegetation (marsh) The dominant 

 s])ecies are: cattail, reed, bulrush, bur-reed, swamp 

 loosestrife, wild rice, and sawgrass. They invade 

 waters of over a meter depth, but in shallower waters 

 or in secondary succession they are replaced by a 

 sedge meadow composed of sedge, rush, and spike 

 rush. 



Swamp shrubs: huttonbusli, alder, dogwood, 

 swamp rose, and sometimes slirubby willow and Cot- 

 tonwood. 



Swamp forest: red and siKer niaples. elm. ash, 

 swamp white oak, and pin oak. 



Succeeding stages depend on the climate of the 

 region. In arid regions the swamp forest may be 

 poorly developed, and grassland or desert vegetation 

 may come in quickly. In the mesic climate of the 

 Kastern states, an oak-hickory associes follows the 

 swamp forest, replaced in turn by a climax of sugar 

 maple-beech or mi.xed mesophytic forest. The hydro- 

 sere in the broad-leaved evergreen climax area of 

 southeastern North America brings in cypress and 

 a number of other unique species. 



\'egetative debris and animal remains, together 

 with inwashed silt, fill the basin gradually, reducing 

 the depth of water and allowing vegetation to en- 

 croach on the periphery. As this process continues, 

 the succession is effected. Ultimately, open water en- 

 tirely disappears as the ground stratum is built up 

 above the water table, and climax vegetation replaces 

 all other types. 



ANIMAL SERE 



Animals characteristic of marshes and 

 ponds constitute a distinct pond-marsh biocies which 

 extends into sluggish or base-leveled streams and 

 the littoral zone of eutrophic lakes. Most animal spe- 

 cies are not restricted to a single stage or community 

 of the plant sere, but commonly occur in several 

 stages in varying abundance and for various activities. 

 Fish, for instance, feed in open water but spawn in 

 shallow water among the emergent vegetation. Sub- 

 merged, floating, and emergent vegetation represent 

 diflferent levels or strata in a single biotic community, 

 and each stratum has about the same degree of dis- 

 tinctiveness as forest community strata. 



With the invasion of swamp shrubs and with the 

 grotmd level well above the water table most of the 

 year, jx^nd and marsh species largely disappear, re- 

 placed by many characteristic new species. This ani- 

 mal comnnmity represents the swamp facies of the 

 deciduous jorcst-cd(/e biocies. which will be discussed 

 later. The swani]) forest is often quite open at its 

 outer margin, and forest edge species remain com- 

 mon. But as this forest develops a closed canopy and 

 drier ground stratum, it is invaded by the swamp 

 facies of the deciduous forest biociation. In the pond 

 sere there is a succession of animal adaptations from 

 aquatic to amphibious to terrestrial. 



POND-MAHSU BIOCIES 



Neuston 



The supraticustoti. organisms which move on 

 top of the surface film in pursuit of most of their life 

 activities, consists of the water striders Gerridae, 

 V'eliidae, Mesoveliidae : the water measurers Hy- 

 drometridae ; the whirligig beetles Gyrinidae ; the 

 springtails Collembola ; some spiders ; and occasional 

 other forms. The gyrinids of several species com- 

 monly occur in social groups (Robert 1955). They 

 are remarkable for having each eye divided by the 

 margin of the head so that the upper portion looks 

 into the air and the lower portion into the water. 

 Several of the forms listed have long legs that dis- 

 tribute the weight of the body over a large area of 

 surface film. The portions of the legs or body that 

 contact the surface film are water repellant. 



The undersurface of the water film supports an 

 injraneuston of Hydra, planarians, ostracods, cla- 

 docerans, snails, and insect eggs, larvae, and pupae 

 (mosquitoes, certain kinds of midge flies, and so 

 forth). For all except the insects, however, the use 

 of the surface film in this manner is usually transi- 

 tory. Some cladocerans, such as Bosmina and 

 Daphnia. occasionally break through the surface film 

 from below, fall over onto their sides, and cannot 

 return. 



The species of plankton found in ponds differ 

 somewhat from those in lakes (Klugh 1927), but the 

 transition from lake species to pond species is a grad- 

 ual and progressive one. Protozoa and Rotatoria are 

 usually more abundant in ponds than in lakes. 



Ponds, marshes, swamps, and bogs 



