Table 4.- 



-Biotic and physical characteristics of unhealthy benthic stations in Hillsborough Bay, Fla., August and September 



1963 



station 



Depth 



Mean sedi- 

 ment grain 

 size 



Sediment 

 sorting 



Sediment type 



Bottom vegetation 



Bottom 

 salinity 



C-7.... 

 C-9.... 



7-2 



7-3 



8-1 



8-2 



8-5 



8-6 



8-7 



8-10 



9-2 



9-5 



9-6 



9-7 



9-8 



9-10 



10-17.... 

 10-18.... 

 10-21.... 



Mean. 

 Range 



' Negative grain size^ excluded. 



Table 5. — Range of tolerance in ecological factors and geographical distribution of the five inost commonly collected mollusks in 



Hillsborough Bay, Fla., August and September 1963 



Species 



Temper- 

 ature 



Salinity 



pH 



Turbidity Depth Current Sediment type 



Bottom type 



Distribution 



Mulinia lateralis ' 2 1-34 



Amygdalum papytitt '9-vl6 



Nastariua vibex i 3-36 



Tagelus plebeius "1-34 



Melongena corona 21 1-34 



P.p.t. M. Cm.liec. 



'1.4-75 26.8-8.7 Tolerant^'.. "1-4.7 59.4-90 Nonselective; fine Unvegetated s Maine to Florida 



sand and and Out ol 



. silt.' « ' ' Mexico." 



'»5-38 26.8-8.7 doJii... 3»l-i.7 ' <90 Fine sand > Unvegetatedi Maryland to Flor- 



Vegetated. ida and Qulf of 



Mexico.' • 



"'9-42 2 6.8-8.7 do2'i'... '2 1-15 "8.6-90 Nonselective; sand Unvegetated "2 Cape Cod to Flor- 



and silt. 5 '3 Vegetated. ida and OuU of 



Mexico.* 



"1-37 26.8-8.7 do2 "21-4.7 "30-90 Nonselective; sand Unvegetated > Cape Cod to Flor- 



and silt ' '* Vegetated. ida and Gulf of 



Mexico." 



i"«8-45 26.8-8.7 do 2 '». . . "0 1-4. 7 « <90 Nonselective; Unvegetated ""' Florida and Gulf 



shell, sand and of Mexico.' " 



silt » " 



' Parker, 1959. 



2 Saloman and Taylor, 1968. 



2 Breuer, 1962. 



' Brett, 1963. 



' This report. 



« Taylor and Saloman, 1969. 



' Hedgpeth, 1954. 



« Marland, 1958. 



• Abbott, 1954. 



'" Tabb, Dubrow, and Manning, 1962. 



" Wells. 1961. 



"2 Wass, 1965. 



'2 Moore, Davies, Fraser, Gore, and Lopez, 1968. 



" Allen, 1954. 



'i Tabb and Manntog, 1961. 



ifl Hathaway and Woodburn, 1961. 



" Menzel, 1956. 



i« Hedgpeth, 1953. 



Most of the healtliy stations (60 percent) were 

 at the mouth of Hillslxirough Bay along transect 

 10. The most numerous and diverse molhisk as- 

 semblage was at station 10-15, where we collected 

 512 individuals and 17 species. At the upper end of 

 the bay, conditioiis were healthy at stations C, C-2, 

 and C-3 where more than average current (C— 2 

 and C-3) and benthic algae (C, C-2, and C-3) 

 maintain a favorable environment for many mol- 

 lusks despite the proximity of effluent discharged 



from the Tampa Sewage Treatment plant at 

 Hooker Point. Throughout the rest of the bay, all 

 stations were either marginal or unhealthy (fig. 1 ) . 



The predominant sediment type at healthy 

 stations was fine sand (2.80 0). Sediment sorting 

 was poor (1.5 0), according to the classification 

 of Folk (1964), and is a reflection of the weak 

 current system in the bay (Taylor and Saloman, 

 1969). A number of authors have noted that fine 

 sand is well suited for colonization by a variety of 



MOLLUSKS AND BENTHIC ENVIRONMENTS IN HILLSBOROUGH BAY, FLA. 



197 



