Spatio-Temporal Patterns of Water Quality in Lower Chesapeake Bay (1984-85)

Water quality conditions at eight stations in lower Chesapeake Bay were monitored from June 1984 through 1985 as part of the initial phase of the USEPA Chesapeake Bay Program. Multivariate statistical techniques were used to characterize the spatio-temporal patterns of nutrients, organic materials, plant pigments and physicochemical parameters in the study area. Nonlinear multivariate regression analysis was employed to "fit" the overall temporal trends for each variable before spatial patterns were evaluated. Several types of "seasonal" trends were observed for variables displaying significant temporal patterns. A distinct depth effect was noted, with temperature, dissolved oxygen, chlorophylls and organic carbon being higher in surface waters; and salinity, suspended solids and phosphorus being higher in bottom waters. Station location also explained a significant portion of the variance in certain parameters. The James River contributed higher levels of nutrients, organic carbon and chlorophyll to the lower Bay region. Similarities in water quality conditions between various groups of stations can be explained in terms of the hydrography and hydrodynamics of the system.