Relationship of carbon availability in estuanne phytoplankton to isotopic composition

Abstract

ABSTRACT:The carbon isotope ratio of particulate carbon in an estuary can vary by at least 10 %O throughout the year. In this study. 2 periods of high primary productivity are compared from data collected in both spring and summer of 1987 and 1988 from the Delaware Estuary (USA). In spring. particulate carbon isotopic compositions (6I3C) were the most positive (up to -17 %0), whereas in summer the values were the most negative (to -32 %o). Equations calculating the CO, concentrations within algal cells were used to show that growth of phytoplankton, especially in spring, may be limited by the availability of dissolved carbon dioxide, C02(d)-An alternative hypothesis for the enrichment of I3c in diatoms from spring blooms includes the possibility that a mechanism for active bicarbonate accumulation is induced during high primary productivity. Similarly, a model is developed for phytoplankton growth during summer with C02(d), rather than bicarbonate, being the species of dissolved inorganic carbon (DIC) transported across the membrane. The influence of respired CO2 on the isotopic composition of total DIC in summer is also calculated to explain the differences in isotopic compositions of particulate carbon. The demand for during periods of high primary productivity limits its availability to phytoplankton. This demand could easily be met by the induction of an active transport system for concentrating DIC, which could explain some of the variability in 6'" of partlculate carbon In estuaries and oceans.

Trophic position of zebra mussel veligers and their use of dissolved organic carbon

“…The values in Table 3 for fractionation relative to CO 2 (d) compare well with those of Fogel et al (1992) for phytoplankton-dominated seston in the Delaware Estuary (pH from 7.0 to 8.4). Marine diatoms have been shown to directly take up bicarbonate without the energy-requiring steps of the enzyme carbonic anhydrase, which converts accumulated bicarbonate to CO 2 , thereby reducing the overall carbon isotope fractionation (Korb et al 1997;Tortell et al 1997).…”

Spatial variability in Florida Bay particulate organic matter composition: combining flow cytometry with stable isotope analyses

“…13 C values of )17.6& to )14.4& fell within the published range of values from estuarine phytoplankton (Gearing et al, 1984;Velinsky & Fogel, 1999;Rau et al, 2001 (Badger & Andrews, 1982;Mayo et al, 1986;Fogel et al, 1992;Popp et al, 1998;Matsuda et al, 2001;Rau et al, 2001). It is reasonable then, that the cyanobacterial populations at both northeastern and western Florida Bay stations employ this mechanism under carbon stress.…”

Factors controlling seasonal variations in stable isotope composition of particulate organic matter in a softwater eutrophic lake

“…The magnitude of this variation is typically driven by external physical forces such as temperature and photoperiod that affect phytoplankton growth rates and isotope fractionation (Fogel et al 1992;Lehmann et al 2004). In general, eutrophic lakes in the low latitude region show relatively narrow ranges of d 13 C POM .…”