Pre-settlement sedimentation rates for the Chesapeake Bay, 
in the basin and its tributaries, were on the order of .14 centi¬ 
meters per year. 
By the time 20 percent of the land had been cleared by agri¬ 
cultural activity, the rate of sedimentation had increased to as 
much as .24 centimeters (cm) per year. By the time half the 
land had been cleared, essentially by the time it reached its 
present status on the Chesapeake Bay, sedimentation rates in¬ 
creased to as much as .39 cm per year. These data are based on 
a relatively large number of samples in several of the major 
tributaries in the Chesapeake Bay. 
We know something of the historic attributes of the Ches¬ 
apeake. Part of the research that has been conducted over the 
last 5 or 6 years with special intensity in the Chesapeake has 
been related to an attempt to discern and decipher the history 
of what's happening in the Chesapeake Bay. We have no quantita¬ 
tive historical record of activities that have occurred and may 
have impacted a change in ecology of the Chesapeake. One ex¬ 
ample of the kind of information that can be derived from a 
sediment core is illustrated in Figures 5, 6, and 7. 
The City of Baltimore has discharged most of its treated sew¬ 
age into a small sub-estuary of the Bay called Back River. An 
area immediately adjacent to Back River has essentially the same 
circulation and receives nothing but recreational or a very mod¬ 
erate level of sewage input. That area is called Middle River. 
An analysis of a sediment core (Figure 5) for the Middle River 
and the Back River as a function of time from 1780 to 1980 
showed the clear change in sediment degradation products, 
perhaps associated with eutrophication, associated with the 
input of nutrient-laden waters into Back River. 
Sediments can provide us with evidence of what changes have 
occurred in systems. In Figure 6, we show two cores located in 
Chesapeake Bay, one north of Annapolis and one in the vicinity 
of the mouth of the Patuxent River, illustrating the concentra¬ 
tion of zinc in the core sediments as a function of time. This 
example is merely to show that from 1780 to 1980 concentrations 
of zinc reached some sort of a maximum at about 1940. The rise 
of zinc and other metals begins around 1880, which may be an 
indication of the initiation of industrial activities and other 
workings affecting the Bay. 
The fact that this pattern is observed in areas far removed 
down the Bay suggests that the transport of potentially toxic 
materials may in fact be relatively widespread in the Chesa¬ 
peake. 
26 
