tion, and exchange along food webs off Peru, the Mid-Atlantic Bight, in 

 the Bering Sea, and within the Gulf of Mexico, suggest that large 

 fractions of the organic matter produced on continental shelves must be 

 exported to continental slopes (Walsh et al., 1981). The annual loss of 

 organic matter from continental shelf ecosystems is far greater than in 

 the open ocean (Table 1-2). If part of the loss of nearshore primary 

 production has increased in those coastal zones where anthropogenic 

 inorganic nutrient supplies have been consistently increasing since the 

 industrial revolution, then burial and diagenesis of this material in 

 slope depocenters, similar to the fate of particulate nitrogen in Lake 

 Erie, could represent the missing BMTs of carbon in global CCL budgets. 



As a result of colonial deforestation by 1850, subsequent farming, and 



>re 

 ■1 



present urban wastes, Lake Erie received an input of 1.6 x 10 tons N yr 



during 1966-67, of which a range of 5 to 50 percent was then thought 

 to be of non-agricultural origin (Vollenweider, 1968; Sly, 1976). 

 Between 1930 and 1970, moreover, the nitrogen content of western Lake 

 Erie had increased by an order of magnitude to a winter-spring maximum 

 of 30 to 60 yg-at Ni~ (Burns, 1976), similar to the nitrogen content of 

 the Mississippi River in 1970 (Walsh et al., 1981). By this time, 

 phytoplankton numbers had increased 20-fold in the western basin (Leach 



and Nepszy, 1976) and the mean annual primary production of Lake Erie 



-? -1 

 was 250 yg C m yr , over two- to four-fold that of the more 



oligotrophic Lakes Huron and Superior (Vollenweider et al., 1974), and 



similar to that of most continental shelves (Walsh, 1982). 



The entire Lake Erie food web, from phytoplankton to fish species 

 (Regier and Hartman, 1973), had changed as a result of this nutrient 

 transient, yet as much as 1/3 of the annual carbon production was uncon- 

 sumed and accumulating on the bottom of the lake in 1970-71 (Kemp et 

 al., 1976). Estimates of sedimentation rate within Lake Erie at that 

 time ranged as high as 1.50 cm yr (Kemp et al., 1976), compared to a 

 mean Holocene rate of 0.17 cm yr (Sly and Lewis, 1972). Nitrogen 

 loading to the sediments increased seven-fold between 1850 and 1970 

 (Kemp et al., 1974); between 1930 and 1970 the organic carbon and 

 nitrogen content of the sediments doubled. Within the last decade, the 

 amount of organic matter on the lake bottom may, in fact, have doubled 



3-2 



