Document Type



Virginia Institute of Marine Science

Publication Date



Special scientific report; no. 92.


A preliminary survey of summer plankton in ·waters surrounding the C. P. Crane generating station in Bengies, Maryland, revealed several possible effects of plant operation. These perturbations were separated into apparent small-scale and large-scale effects:

Small-scale effects were limited to the immediate discharge region of Saltpeter Creek and included (1) occasional elevation of temperatures at the surface (in August) to above the lethal limit for most zooplankton and sufficiently high to inhibit photosynthesis, (2) a decrease in chlorophyll-a, seen in July and August, (3) a sharp decrease in productivity, also in July and August, and (4) absence of a common cladoceran in July.

Possible large-scale effects covered most of the sampled area and included (1) a reduction in diversity due to displacement of a natural freshwater community with an oligohaline one that has been altered somewhat by the addition of heat, (2) increased temperature and productivity throughout Saltpeter Creek and the lower Gunpowder River when higher ambient temperatures coincide with peak demand for electric power and (3) an increase in the barnacle population by the provision of submerged power plant structures for settlement of larvae and the distribution of larvae throughout the system via cooling water discharged into Saltpeter Creek.



Plankton -- Chesapeake Bay (Md. and Va.); Electric power-plants -- Environmental aspects -- Maryland; Gunpowder River