FISHERY BULLETIN: VOL. 69, NO. i 



2 - 

 I - 



JUNE 18-19 



JULY 9-10 



E-. 



m 



AA 



JULY 24-25 



W; 



JULY 30-31 



AUGUST 13-14 



m 





JUN 18-AUG 14 



RESPIBiTION 

 I 



I 2 6 7 10 



STATION 



Figure 2. — Gross and net production and respiration by 

 station and date, and average values for all sampling 

 dates. 



DISCUSSION 



It is probable that eutrophic conditions will de- 

 velop more frequently in housing development 

 canals than in natural marsh areas because of 

 differences in phytoplankton production, water 

 circulation, water exchange, and high nutrient 

 levels. In this study, gross production of phy- 

 toplankton in surface waters was higher in the 

 canals than in the marsh or bay. We did not 

 obtain information for computing production per 

 unit area, but it is iirobable that production per 

 unit area was significantly greater in the canals 

 than in the other two areas, the reasons being 

 the greater depths and lower turbidities in the 



canals. Wind-driven circulation responsible for 

 reaeration of the waters in the development is 

 less than in the natural area because of houses 

 blocking and diverting prevailing winds and be- 

 cause many of the canals are narrow and per- 

 pendicular to the direction of prevailing summer 

 winds. Water depths at mean low tide in the 

 development averaged about 1.5 m but were 

 often much greater, sometimes over 3 m, whereas 

 depths in the natural ai'ea averaged about 0.6 m 

 but were always less than 1 m. With the average 

 tide level change of 0.3 m, this means that only 

 about one-fifth of the volume of water in the 

 development exchanges with the bay during a 

 normal tidal cycle, whereas about one-half ex- 

 changes per cycle in the natural area. Nutrient 

 levels were about the same (nitrogen) or slightly 

 higher (phosphates) in the canals than in the 

 natural area (Moore and Trent, 1971). It is 

 possible, however, that because of reduced water 

 exchange, nutrient levels in parts of the devel- 

 opment were too high to maintain a balanced 

 ecological system. 



LITERATURE CITED 



American Public Health Association. 



1962. Standard methods for the examination of 

 water and wastewater. 11th ed. Am. Public 

 Health Assoc, Inc., New York, 626 p. 

 Carritt, D. E., and J. H. Carpenter. 



1966. Comparison and evaluation of currently em- 

 ployed, and modification of the Winkler method 

 for determining dissolved oxygen in seawater; 

 NASCO Report. J. Mar. Res. 24: 286-318. 

 Gaarder, T., and H. H. Gran. 



1927. Investigations of the production of plankton 

 in the Oslo Fjord. Cons. Perm. Int. Explor. Mer., 

 Rapp. P.-V. Reun. 42, 48 p. 

 Moore, D., and L. Trent. 



1971. Setting, growth and mortality of Crassostrea 

 virijivica in a natural marsh and a marsh altered 

 by a housing development. Proc. Natl. Shellfish. 

 Assoc. 61: 51-58. 

 Rytiier, J. H. 



1956. The measurement of primary productivity. 

 Limnol. Oceanogr. 1: 72-84. 

 Taylor, J. L., and C. H. Saloman. 



1908. Some effects of hydraulic dredging and 

 coastal development in Boca Ciega Bay, Florida. 

 U.S. Fish Wildl. Serv., Fish. Bull. 67: 213-241. 



832 



