256 



AqitaUc Ecos\s!ems — Our Livin^i Rc\oinves 



For further inforniatiun: 



Richard L, Moc 



University of Calit'ornia 



University Herhariiim 



Berlieley'CA 94720 



the lOO-yeai" recofd of west coast phycology 

 (study of algae) by using a lilei'ature review. 

 compilation of data from specimens at west 

 coast herbaria, and original observations. For 

 each species a tabular representation of geo- 

 graphic and hydrographic range is provided. 

 Presence or absence in different precincts along 

 the coast and details of phenology (relations 

 between climate and periodic biological phe- 

 nomena), such as reproductive state throughout 

 the year, are indicated. The study gives ecolog- 

 ical information such as requirements for sub- 

 strate and exposure to waves as well as the pres- 

 ence of epiphytes and parasites. In addition, 

 illustrations and references to pertinent taxo- 

 nomic. chemical, ecological, genetic, and phys- 

 iological literature are given. 



If this kind of project is done on a national 

 scale, workers must have the necessary taxo- 

 nomic training and herbarium resources must 

 be preserved. About 100 American scientists 

 have algal taxonomy as a principal area of inter- 

 est (Anonymous 1992). Modem molecular tax- 

 onomic methods aid in the study of some 

 groups of algae, but to progress toward a nation- 

 al inventory, traditional taxonomic methods 

 must be supported. 



References 



Abbott, I.A.. and G.J. Hollenberg. 1976. Maiine algae of 



California. Stanford University Press. CA. 827 pp. 

 Anonymous. 1992. 1992 Membership Directory and 



Bylaws [of the Phycological Society of America]. 



Journal of Phycology (4. supplement). 

 Brock. T.D. 198.^. A eutrophic lake: Lake Mendota. 



Wisconsin. Springer- Verlag. New York. 308 pp. 



Dawes. C.J. 1974. Marine algae of the west coast of Florida. 

 University of Miaini Press. Coral Gables. FL. 201 pp. 



Dawson. E.Y. 1 959. A preliminary report on the marine ben- 

 thic flora of southern California mainland shelf. Pages 

 169-264 in Oceanographic survey of the Continental 

 Shelf area of southern Califoniia. California State Water 

 Pollution Control Board Publ. 20. 



Dillard. G.E. 1989. Freshwater algae of the southeastern 

 United States. Part 1. Chlorophyceae: Volvocales. 

 Tetrasporales and Chlorococcales. Bibliothcca 

 Phycologica81. 202 pp. 



Foster. M.S.. A. P. De Vogelaere. C. Harrold. J.S. Pear.se. and 

 A.B. Thum. 1988. Causes of spatial and temporal pat- 

 terns in rocky intertidal communities of central and 

 northern California. Memoirs of the California Academy 

 of Sciences 9. 45 pp. 



Foster. M.S.. and D.R. Schiel. 1985. The ecology of giant 

 kelp forests in California: a community profile. U.S. Fish 

 and Wildlife Service Biological Rep. 85 (7.2). 152 pp. 



Hoshaw. R.W.. and R.M. McCourt. 1988. The 

 Zygnemataceae (Chlorophyta): a twenty-year update of 

 research. Phycologia 27:51 1-548. 



Johan.sen. J.R. 1993. Cryptogamic crusts of semiarid and 

 arid lands of North America. Journal of Phycology 

 29:140-147. 



Makarewicz. J.C. 1993. Phytoplankton biomass and species 

 composition in Lake Erie. 1970 to 1987. Journal of Great 

 Lakes Res. 19:258-274. 



Nicholls. K.H. 1993. Recent changes in Lake Erie (North 

 Shore) phytoplankton: cumulative impacts of phospho- 

 rous loading reductions and the .?ebra mussel introduc- 

 tion. Journal of Great Lakes Res. 19:637-647. 



North. W.J.. editor. 1971. The biology of giant kelp beds 

 (Macmcysti.s) in California. Beihefte zur Nova Hedwigia 

 3 1 . 600 pp. 



Schneider. C.W.. and R.B. Searles. 1991. Seaweeds of the 

 southeastern United States: Cape Hatteras to Cape 

 Canaveral. Duke University Press. Durham. NC. 553 pp. 



Widdowson. T.B. 197 1 . Changes in the intertidal algal flora 

 of the Los Angeles area since the survey by E. Yale 

 Dawson in 1957-1959. Bull, of the Southern California 

 .^cademy of Sciences 70:2-16. 



Freshwater 

 Diatoms: 

 Indicators of 

 Ecosystem 

 Change 



by 



Donald Charles 



Academy of Natural Sciences, 



Philadelphia 



Pat Kociolek 



California Academy of 



Sciences, San Francisco 



Diatoms are photosynthetic unicellular 

 organisms. They are found in almost all 

 aquatic and semi-aquatic habitats and are of 

 great ecological importance because they form 

 an important part of the base of the food web. 

 Although diatoms are widely distributed as a 

 group, most species occur only in habitats with 

 specific physical, chemical, and biological char- 

 acteristics. Ecologists have long made practical 

 use of this habitat specificity by collecting and 

 analyzing individual species and community 

 data to determine the quality or condition of 

 aquatic habitats. Both long-term monitoring of 

 specific lake and stream habitats and analysis of 

 diatom remains (that become part of the sedi- 

 mentary record of lakes) allow scientists to 

 obtain a unique long-term historical perspective 

 on these ecosystems. This perspective is espe- 

 cially valuable in assessing the long-term 

 effects of human activities on aquatic and ter- 

 restrial ecosystems. Diatoms have been studied 

 throughout the country, but no reasonably com- 

 plete compilation or summary of these studies 

 exists. 



Diatoms are divided into two groups based 

 on overall symmetry of the cell walls; radially 

 symmetrical forms are informally called "cen- 

 tric" diatoms while bilaterally symmetrical 

 forms are referred to as "pennate" diatoms. One 

 remarkable aspect of these organisms is that 

 they have cell walls made of glass (silicon diox- 

 ide). The glass cell walls are perforated and 

 ornamented with many holes, which are usually 

 arranged in definite patteiTis. The nature of 

 these perforations as well as their orientation 

 and densities help in the identification of diatom 

 species. Diatom cell walls come in two pieces 

 that fit together the way a Petri dish or pill box 

 does. When the.se organisms divide, each half 

 reproduces a "daughter" half that, because of 

 the rigidity of the glass walls, must be smaller 

 than the original half 



Despite the important roles diatoms play in 

 aquatic ecosystems and their utility in evaluat- 

 ing and monitoring environmental change in 

 these systems, intensive tloristic or taxonomic 

 studies on freshwater diatoms in North America 

 have been limited. A two-volume work entitled 



