25S 



Aqualic Ecosystems — Our Living Resources 



For further information: 



Donald Charles 



Academy of Natural Sciences 



1900 Benjamin Franklin Parkway 



Philadelphia. PA 19103 



times (Gumming et al. 1992). Lakes in other 

 regions of the country have also acidified but 

 not to the same extent (Charles et al. 1989). The 

 amount of acidification inferred from diatoms is 

 related to the level of atmospheric loading of 

 strong acids and the ability of watersheds to 

 neutralize those acids. Analysis of diatoms and 

 sedimentary remains of other biological groups 

 (e.g.. chrysophytes, chironomids. Cladocera) 

 reveals that acidic deposition has had significant 

 effects on aquatic communities in many lakes. 

 Numbers of taxa are reduced, but some acid-tol- 

 erant taxa have significantly increased in abun- 

 dance. 



Lake Eutrophication 



Population estimates of the numbers of lakes 

 in New England and New York that are more 

 eutrophic now than in presettlement times are 

 being obtained from analyses of diatom assem- 

 blages from recent and preindustrial levels of 

 sediment cores taken as part of the U.S. 

 Environmental Protection Agency's Surface 

 Water component of the Environmental 

 Monitoring and Assessment Program (EMAP: 

 Dixit and Smol 1994). The approach of examin- 

 ing lake eutrophication by using diatom assem- 

 blages has been widely applied in North 

 America and throughout the world. 



Rivers and Streams 



Many long-term diatom data sets exist that 

 can inform us about trends in water quality. The 

 monitoring program conducted by the Federal 

 Water Pollution Control Agency in the 1960's 

 tracked the status of major rivers throughout the 

 country (Williams and Scott 1962). Monitoring 

 of diatom assemblages in rivers and streams is 

 just beginning as part of the U.S. Geological 

 Survey's National Water Quality Assessment 

 (NAWQA) and of the Environmental 

 Monitoring and Assessment Program. The 

 Academy of Natural Sciences of Philadelphia 

 has long-term records for several rivers in the 

 eastern United States. Many of these records 

 show that the quality of water downstream from 

 industrial effluent outfalls and sewage treatment 

 plants has improved markedly, but others show 

 worsening conditions, often due to the 



increased number of sources of stress along the 

 river or in the watershed. Much more could be 

 learned about trends by simply analyzing the 

 immense data that already exist, especially by 

 using new quantitative techniques developed in 

 the past 5-10 years. 



Climate Change 



Diatom assemblage composition is sensitive 

 to changes in water level, salinity, ice cover, 

 wind-mixing patterns, and other characteristics 

 directly and indirectly affected by climate. 

 Paleolimnological studies of sediment cores are 

 providing valuable data on climate change over 

 the past hundreds to thousands of years, which 

 are essential for understanding the nature and 

 magnitude of ecosystem change that can be 

 expected in future years. 



Conclusions 



The ability to infer ecosystem status and 

 trends from diatoms is largely dependent on the 

 availability of ecological data for the species 

 occuiTing at study sites. The amount of such 

 data is accumulating at an increasingly rapid 

 rate, but it is in many separate data bases. These 

 need to be coordinated so that users will have 

 easier access to the data that already exist. 



References 



Charles. D.F.. R.W. Battarbee. I. Renberg. H. Van Dam. and 

 J. P. Smol. 1989, Paleoecological analysis of lake acidifi- 

 cation trends in North America and Europe using diatoms 

 and chrysophytes. Pages 207-276 in S.A. Norton. S.E. 

 Lindberg. and A.L. Page. eds. Acidic precipitation. Soils, 

 aquatic processes, and lake acidification. Vol. 4. 

 Springer- Verlag. New York. 



Cumming. B.F., J. P. Smol. J.C. Kingston, D.F. Charles. 

 H.J.B. Birks. K.E. Cambum. S.S. Dixit. A.J. Uutala. and 

 A.R. Selle. 1992. How much acidification has occurred 

 in Adirondack region lakes (New York. USA) since 

 preindustrial times? Canadian Journal of Fisheries and 

 .Aquatic Sciences 49:128-141. 



Dixit. S.S.. and J. P. Smol. 1994. Diatoms and indicators in 

 the Environmental Monitoring and Assessment Program 

 — Surface Waters (EMAP — SW). Environmental 

 Monitoring and Assessment 31:275-306. 



Patrick. R.. and C.W. Reimer. 1966. 1975. The diatoms of 

 the United States. Vols. 1 and 2. The Academy of Natural 

 Sciences of Philadelphia. Vol. 1:688 pp. Vol. 2:213 pp. 



Williams. E.G.. and C. Scott. 1962. Principal diatoms of 

 major waterways of the United States. Ecology 7:365- 

 379. 



