Our Ijvtiti; Rcs(mn't'\ — Atiutilic Ecn.wstfnis 



255 



Algae are an extremely diverse group of pho- 

 tosynthelie organisms that range from sin- 

 gle-celled organisms to complex thalli (e.g.. 

 kelps). Benthic algae live attached to the bottom 

 of a water body or to living or nonliving objects 

 on the bottom. Planktonic algae live free-tloat- 

 ing in the ocean and in the largest to smallest 

 lakes and streams. Algae also occur in such var- 

 ied places as the surface layers of soils and 

 porous rocks, on the bark and leaves of trees, in 

 snow, hot springs, and in symbiotic association 

 with fungi to form lichens. 



These organisms are important as primary 

 producers (representing the base of the food 

 chain or pyramid), in contributing to the fertili- 

 ty of soil, in providing substrate for other organ- 

 isms, and in defining aquatic environments such 

 as kelp beds and algal reefs. 



The toxicity of certain marine unicellular 

 algae can limit coastal marine fisheries (e.g.. 

 dinoflagellates in red tide). In fresh water. 

 blooms tied to nutrient enrichment are often a 

 major nuisance. A few species of macrophytic 

 algae (large enough to be seen by the naked eye) 

 are harvested from the wild for food and indus- 

 trial purposes. 



Knowledge of the algae of the United States 

 is not uniform across various groups or environ- 

 ments. Some modern regional floras, or lists of 

 plants (e.g., California, southeastern coast, gulf 

 coast), are available for marine benthic macro- 

 scopic algae (Dawes 1974; Abbott and 

 HoUenberg 1976; Schneider and Searles 1991), 

 of which there are approximately 900 species 

 on the Pacific coast and fewer on the Atlantic 

 and gulf coasts (approximately 450 for the 

 northern Atlantic coast, 350 for the southeastern 

 Atlantic coast, and 300 for the gulf coast). Local 

 floras are available for many places. Few 

 species are shared between the Atlantic and 

 Pacific coasts. Information about marine 

 microalgae is less accessible. 



Local and regional floras are available for 

 some groups of freshwater algae (e.g., Hoshaw 

 and McCourt 1988; Dillard 1989; Johansen 

 1993), but information is absent or has not been 

 compiled for much of the country. Because no 

 attempt has been made to produce a national 

 flora of freshwater algae in this century, it is not 

 possible to estimate the number of such species. 

 Many groups of algae are cosmopolitan, how- 

 ever, and European monographs and floras can 

 be u.seful. 



In general, distribution, status, and trends of 

 algae, even of conspicuous marine algae, are not 

 well established. Floras usually provide ranges, 

 but distribution of many species may be discon- 

 tinuous, with various causes for the discontinu- 

 ity. Filling the gaps (or confirming the disconti- 

 nuities) will require considerable effort. 



Although nationwide data on status and 

 trends of North American algal populations are 

 not readily available, scientists do know that a 

 great deal of formerly aquatic habitat has 

 become unavailable for algae because of landfill, 

 reclamation, and water diversion. In addition, 

 other habitat has been altered through farming 

 and municipal and industrial waste discharge. 

 In the case of reservoirs, however, one kind of 

 aquatic habitat has been replaced by another. 



Long-term information about phytoplankton 

 is available for the Great Lakes; this informa- 

 tion has allowed documentation of water-quali- 

 ty improvement in Lake Erie and analysis of the 

 effect of the invasion of the zebra mussel 

 [Dreisseiui polymorpba: Makarewicz 1993; 

 Nicholls 1993). Much limnological information 

 is available for individual water bodies or catch- 

 ment basins (e.g.. Brock 1985 for Lake 

 Mendota in Wisconsin), but reconciling the dif- 

 ferent methods used when comparing separate 

 studies is a challenge. 



Interpretation of marine baseline and trend 

 data is complicated by differences in communi- 

 ties over time and space (Foster et al. 1988). An 

 example of the utility of marine baseline studies 

 is the census of algae along the coast near Los 

 Angeles (Dawson 1959) that showed how 

 sewage discharge reduced algal diversity. 

 Subsequent resurveys (Widdowson 1971) 

 demonstrated some improvement after stricter 

 environmental regulations were enacted. 

 Long-term studies are available for giant kelp 

 {Macrocysti.s pyrifera). the economically 

 impoilant component of southern California 

 kelp beds. North (1971) and Foster and Schiel 

 (1985) documented the decline of kelp beds 

 after sewage was discharged into the ocean. 

 They also discussed the partly successful 

 attempts at remediation, which involved trans- 

 plantation and predator control and which led to 

 an appreciation of the complexity of organismal 

 interactions in kelp beds. 



Achieving a uniform estimate of the status of 

 algae in North America will take considerable 

 original observation and collection. Further- 

 more, different research approaches will be nec- 

 essary for freshwater versus marine algae and 

 for macrophytic algae versus microphytic algae. 

 To determine status and trends of marine 

 macroalgae. published literature must be com- 

 piled and analyzed. In addition, unpublished 

 information should be obtained from herbaria 

 and from private collections in the form of spec- 

 imens, labels, and collectors' notebooks, illus- 

 trations, and checklists. 



This process has been followed for west 

 coast algae in a project by T. DeCew, the results 

 of which are available at the Herbarium of the 

 University of California. This project condenses 



Marine and 

 Freshwater 

 Algae 



by 

 Richard Moe 



University of California 



