dredged and undredged locations. Chlorophyll a 

 did not fluctuate seasonally. Low primary produc- 

 tion noted in February may be due to turbid con- 

 ditions rather than lack of nutrients or limitation 

 by another factor, such as temperature (table 1). 

 Except for higher values in extremely eutropliic 

 Hillsborough Bay, pigment and production figures 

 (table 5) are both similar to those recorded for 

 other areas of the estuary as well as other estu- 

 arine waters of the southeast (Ragotzkie, 1959; 

 Odum and Wilson, 1962 ; Williams, Murdock, and 

 Thomas, 1966 ; Saville, 1966 ; Dragovich and John- 

 son, 1966). 



In 1962-66, mean chlorophyll a in Boca Ciega 

 Bay was 8.6 mg./m.^ and mean primary produc- 

 tion by phytoplankton was O.-iO G.C/m.Vday. The 

 most extensive data for chlorophyll a and primary 

 production in Boca Ciega Bay are from daily 

 observations by May and Johnson * between June 

 1962 and June 1964 (table 5). These figures show 

 a slightly lower mean annual value for chloro- 

 phyll a (7.3 mg./m.-^) but the same value for mean 

 annual production (0.40 G.C/m.Vday). Earlier 

 data indicate about a twofold rise in chlorophyll 

 a since 1952, following nutrification of the lagoon 

 by sewage (table 5). 



Actually, the productivity figures given above 

 for Boca Ciega Bay are misleading and far too 

 low because sea grasses and unicellular and fila- 

 mentous benthic algae add to the production that 

 was recorded only for phytoplankton. Pomeroy 

 (1960), who considered photosynthetic contribu- 

 tions by all hydrophytes in his study of primaiy 

 production in lower Boca Ciega Bay, concluded 

 that an average value is about 5 G.02/m.-/clay. 

 Odum and Hoskin (1958) gave a value of about 

 5 grams of dry organic material per day. On the 

 basis of an allowance of 0.5 G. of C for each gram 

 of organic matter produced (May, 1966), this is 

 equivalent to about 2.5 G.C/m.-/day or nearly 

 six times the estimates of daily production in the 

 lagoon by phytoplankton alone. The main point 

 to be made is that under natural conditions pri- 

 mary production from a variety of photosynthetic 

 taxa far exceeds production in turbid waters where 

 photosynthetic activity of benthic flora has been 

 reduced or eliminated (Blinks, 1955; Odum, 

 McConnell, and Abbott, 1958; Pomeroy, 1959). 



s See footnote 3. 

 234 



SEDIMENTS 



Sediments of Tampa Bay are mainly a firm mix- 

 ture of sand and shell containing little silt or clay 

 (Goodell and Gorsline, 1961). Soft deposits are 

 l(»calized in upper reaches of Old Tampa Bay, 

 Hillsborough Bay, natural depressions, and 

 dredged bottom of bayfill access canals, where tlie 

 weight pei'centiige of silts and clays may exceed 

 90 percent. In Boca Ciega Bay the sediments in 

 undredged areas averaged 94 percent sand and 

 shell whereas the sediments in dredged canals 

 averaged 92 percent silt and clay ( table 7 ) . 



The ooze measured in two dredged pockets be- 

 tween liayfill fingei'S extended downward to a 

 depth of about 3.6 m. The upper 30 cm. was dark, 

 semifluid, and sulphurous; below was an uncon- 

 solidated horizon of gray clay. The predominantly 

 organic upper layer consists of decompasing detri- 

 tus that accunuilates in the canals. The origin of 

 tlie underlying clay has not been determined, Init 

 it seems likely that a thick stratum of clay was 

 uncovered in the dredging which extended some 

 distance below a bay floor veneer of sand and shell. 

 To judge from the uniformity of the viscous clay 

 layer, tliis material was redeposited after dredging 

 ceased and now lies too deep to be reworked by 

 normal water movements. Clay settles out of sus- 

 pension slowly and may form deposits to 364 m. 

 or more beyond dredging sites (Phillips, 1960a: 

 Mackin, 19G1 ; Hellier and Kornicker, 1962; Odum, 

 1963; Woodburn, 1965). Thus, resident benthos 

 far from fill and lx)rrow areas may be suft'ocated 

 by sedimentation from dredging operations. 



MACROBIOTA 



Analysis of biological samples in Boca Ciega 

 Bay supplements earlier studies in undredged 

 areas and contrasts these findings with a scarcity 

 of macrobiota found in bayfill canals. 



DIVERSITY AND ABUNDANCE 



In the firsi comprehensive survey of Boca Ciega 

 Bay, Hutton et al. (1956) recorded nearly 200 

 plant and animal species from marine and tide- 

 water communities and presented fishery statistics 

 that attest to the importance of commei'cial and 

 sport species. Later a notable addition was made 



U.S. FISH AND WILDLIFE SERVICE 



