FISHERY BULLETIN: VOL. 79. NO. 4 



bacteria as a food source. The meiofauna- 

 macrofauna correlation completed the trophic web 

 between the sediment inhabitants. 



Finally, densities of shrimp on the Texas shelf 

 were tied to the sediment detritus pool by correla- 

 tions between shrimp body burdens of nickel and 

 total hydrocarbons and sediment nickel concen- 

 trations and a sediment hydrocarbon variable 

 (Figure 3). The correlations between zooplankton 

 nickel body burdens, nickel concentrations in the 

 sediment, and shrimp nickel body burdens (Figure 



z 

 o 



H 

 <J 



=> J? 

 Q % 

 O ^ 



Q- o 



> E 



a: 

 < 



S 



at 

 a. 



J FMAMJJ ASOND JF MAMJ JISOND 



1976 1977 



SAMPLING DATE 



Figure 4. — The 2-yr cycle of primary production (carbon fixa- 

 tion I for Texas coastal waters between 1976 and 1977. Primary 

 production calculated according to methods of Ryther and 

 Yentsch (1957) using chlorophyll a measurements. 



3) allowed us to propose a trophic coupling 

 hypothesis for the shelf shrimp populations that 

 included both pelagic and benthic components. 



Trophic Web 



Primary production for Texas inner shelf 

 waters, determined from the Reference Station 

 chlorophyll a measurements, was bimodal annu- 

 ally with peaks usually occurring in spring and 

 fall (Figure 4). Since the spring peak in biomass 

 for 1977 was not measured and presumably missed 

 by the timing of our sampling, the estimate of 103 

 g C/m^ per yr representing the amount of carbon 

 fixed in the primary level of the trophic web (Fig- 

 ure 5) was probably low. 



Macrozooplankton biomass on the Texas shelf 

 averaged 3.57 g/m^ wet weight (Table 2). From 

 this amount, annual production of macrozoo- 

 plankton was estimated to be 24.98 g/m^ per yr. In 

 conversion for sampling bias, the production esti- 

 mate was doubled to 49.96 g/m^ per yr. The carbon 

 equivalent of zooplankton production was esti- 

 mated to be 3 g C/m^ per yr. Similarly converted 

 biomass data from the neuston component of the 

 planktonic community added 0.2 g C/m^ per yr 

 (Table 2) to the macrozooplankton portion of the 

 trophic web (Figure 5). Standing stock of mi- 

 crozooplankton was 0.47 g/m^ wet weight which 

 converted to an annual production of 0.9 g C/m^ 



ZOOPLANKTON 



MICRO MACRO 



0.9 3.2 



OTHER 

 INVERTEBRATE 



EPIFAUNA 

 O.OIgCArZ/yr 



Figure 5.— Theoretical model of an 

 annual production and energy flow food 

 web for the south Texas continental 

 shelf All material flows represent gram 

 C/square meter per year. 



742 



