LINDALL, FABLE, and COLLINS: CONDITIONS OF UPLAND CANALS 



STATION 1 iCONTROLi 



30 



26 



22 



18 

 30K STATION 2 



26 



22 



SURFACE n^ BOTTOM 



JJ^ 



M 



1 



1 



1 



18 

 30 



O 

 ,0 26 



22 



— 18 



Z 30 



26 



22 



18 

 30 



26 



22 



18 

 30 



26 

 22 



18 



1 



1 



1 



I 



1 



1 



1 



STATION 3 



1 



1 



■1 



1 



1 



1 



1 



1 



1 



STATION 4 



1 





1 



J 



1 



1 



1 



1 



J. 



STATION 5 



1 



1 



1 



nri 



1 



STATION 6 



1 



1 



1 



- ri 



1 



1 



1 



1 



1 



1 



1 



1 



OCT NOV DEC JAN FEB MAIi APR MAT JUN JUL AUG SEP 



6 

 4 

 2 

 

 6 

 4 

 2 



s° 



Z 4 



UJ 



go 



Q 6 



a 



6 

 4 

 2 





 6 

 4 

 2 







STATION 1 ICONTROLi 



SURFACE [^BOTTOM 



1 



1 



1 



1 



STATION 2 



BO, 



^ 



- STATION 3 



1 



STATION 4 



STATION 5 



T 



STATION 6 



1 



1 



OCT NOV DEC JAN FEB MAR APR MAY JUN JUl AUG SEP 



Figure 3. ^Monthly salinity at the surface and bottom of all 

 hydrologic stations, October 1971 -November 1972. 



of the canals was always less than at the surface 

 with the single exception of Station 6 in June. 

 Moreover, about 50% of the bottom samples taken 

 throughout the year at stations farthest from the 

 bayou (Stations 3-5) contained less than 2.0 

 ml/liter of oxygen; several were anoxic or nearly 

 so. At Station 6, closest to the bayou, oxygen levels 

 were never observed to be less than 2.1 ml/liter. 

 Trent et al. (1972) also reported oxygen depletion 

 at inland portions of housing development canals 

 in Galveston Bay, Tex., during the summer. 



Results of the previous year's study showed se- 

 vere oxygen depletion in the canals during the 

 summer months following a red tide (caused by 

 Gymnodinium breve) outbreak (Lindall et al. 

 1973). In that study decaying fish killed by the red 

 tide placed additional oxygen demand on the sys- 

 tem and precluded the determination of the extent 

 to which dissolved oxygen would have been de- 

 pressed in the absence of red tide. In the present 

 study, no red tide occurred, but oxygen was again 



Figure 4. — Monthly dissolved oxygen at the surface and bottom 

 of all hydrologic stations, October 1971-November 1972. 



depleted at the bottom of the most inland stations 

 in the canals during the summer. In fact, low dis- 

 solved oxygen occurred more frequently and over 

 a longer period of time (October 1971 and May 

 through September 1972) than in the previous 

 year. 



FISHES AND 

 MACROINVERTEBRATES 



Thirty-eight species and 9,502 individuals of 

 vertebrates and invertebrates were collected in 

 the canals during the year (Table 1). Of the 38 

 species, 34 were finfish, 1 was the diamondback 

 terrapin, Malaclemys terrapin, and 3 were com- 

 mercially important invertebrates (blue crab, 

 Callinectes sapidus; pink shrimp, Penaeus 

 duorarum; and brief squid, Lolliguncula brevis). 

 Fourteen of the 34 species of finfish did not occur in 

 the previous year's catch. These 14 species, how- 

 ever, made up less than 1% of the total catch. 



83 



