partitioning of space or other com- 

 mon resources are obvious examples. 

 Symbiotic relationships within which 

 two species absolutely require each 

 other for their mutual survival is 

 the evolutionary epitome of this 

 avenue of feedback. The signifi- 

 cance of the feedback concept in 

 influencing long term energy flow 

 patterns is perhaps best exemplified 

 by noting the degree to which organ- 

 isms develop and depend upon protec- 

 tive coloration and mimicry. 



In using Figure 47 (and subse- 

 quent ones) as a conceptual device, 

 it is also useful to keep in mind 

 some basic characteristics of 

 trophic levels, as pointed out by 

 Lindemann (1942): 



(1) Progressively higher trophic 

 levels (in keeping with the 

 laws of thermodynamics) con- 

 tain progressively lower 

 standing crops of biomass; 

 and 



(2) Delineations between pro- 

 gressively higher trophic 

 levels become progressively 

 more difficult to discern. 



To this is added a third char- 

 acteristic, the metamorphosis of 

 trophic position that often accom- 

 panies the transition of an organism 

 over its personal life history. 

 Larvae and juveniles often have 

 different nutritional requirements 

 and exhibit feeding anatomies and 

 preferences not found in adult 

 forms. They may also be subject to 

 a different spectrum of predation 

 pressures than adults of the same 

 species. 



In moving into the subject of 

 how these habitats produce fish and 

 wildlife, it seems appropriate to 

 begin with one particularly impor- 

 tant element of the vegetation cover 

 that does not appear as an distinct 

 community in Table 23, the blue- 



green algal mat community. Attached 

 blue-green algae and diatoms are 

 most abundant in association with 

 the relatively open, wet conditions 

 of the spike rush/beak rush type of 

 marsh. However, since the algal mat 

 community tends to survive dessica- 

 tion quite well, it is also found to 

 varying degrees in the drier grami- 

 noid habitats as well. During the 

 dry season it can be found through- 

 out the sawgrass and prairie zones 

 as a scummy looking cake on the peat 

 or limestone substrate. 



Wood and Maynard (1974) esti- 

 mate that a significant, if not 

 greater portion, of the total pri- 

 mary production of these habitats 

 derives from the 200+ species of 

 periphyton rather than from the vas- 

 cular plant species. Brock (1970) 

 reports higher productivity from 

 epiphyte-laden Utricularia than 

 nonladen Utricularia . Hunt (1961) 

 estimates that nearly all of the 

 production and respiration of the 

 open water prairies is due to the 

 mat, not the macrophytes. Carbon 

 production rates in one such prairie 

 community in Taylor Slough ranged 

 from 0.80 to 1.67 g/m2/d; respi- 

 ration ranged from 0.25 to 0.38 

 g/m 2 /d. 



Productivity rates, however, do 

 not tell the full story of the key 

 role played by the algal mat in the 

 seasonal cycle of Everglades ecolo- 

 gy. One element of its ecological 

 importance arises from the fact that 

 during drought conditions it tends 

 to coat the substrate and prevent 

 total dessication within and beneath 

 it, thus providing a microhabitat 

 within which small invertebrates (or 

 larvae and eggs) can survive season- 

 al drought conditions. As water 

 levels once again rise, a ready, 

 local source of small crustaceans, 

 insects, and fish can quickly ex- 

 ploit the newly flooded environment 



130 



