Spring and fall microheterotrophic utilization of dissolved free amino acids in a California Borderland basin

DB Craven, AF Carlucci
1989 Marine Ecology Progress Series  
Seasonal variation in microheterotrophic utilization of dissolved free amino acids (DFAA) was examined in depth profiles from the central Santa Monica Basin, a California Borderland basin offshore of Los Angeles. Although little change was observed between spring and fall in bacterial abundances, DFAA concentrations, or utilization in the basin midwaters, a substantial increase was measured in all parameters under late spring bloom conditions in euphotic zone waters and in fall in the benthic
more » ... ll in the benthic boundary layer (BBL). Neither zone showed enhanced values in early spring. Late spring euphotic zone bacterial abundances, total dissolved free amino acids (TFAA) and utilization of selected DFAA increased 2 to 4-fold over fall values, while values in the BBL increased by similar ratios over those measured in spring. Benthic utilization of spring bloom detritus apparently continued into the fall season in the basin environment studled. Utilization of a single DFAA, glutamic acid, and of a mixture of glutamic acid, aspartic acid and serine were highly correlated throughout the water column in spring and fall, although TFAA utilization rates calculated using glutamic acid alone slightly overestimated rates using the mixture. DFAA utilization was estimated to account for a larger fraction of primary carbon production in fall (11 to 18 %) than in early (1 % ) or late spring (7 X).
doi:10.3354/meps051229 fatcat:o5ehmpil75fjnfbr7h6hmttahy