We examine effects of high river particulate flux and municipal wastewater effluent on heterotrophic
organic carbon cycling in coastal subtidal sediments. Heterotrophic production was a predictable
(r2 = 0.95) proportion (56%) of oxidized OC flux and strongly correlated with organic/inorganic flux. Consistent
growth efficiencies (36%) occurred at all stations. Organic biomass was correlated with total, OC
and buried OC fluxes, but not oxidized OC flux. Near the river, production was modest and biomass high,
resulting in low P/B. Outfall deposition resulted in depleted biomass and high bacterial production,
resulting in the highest P/B. These patterns explain why this region is production ‘‘saturated’’. The
d15N in outfall effluent, sediments and dominant taxa provided insight into where, and which types of
organisms feed directly on fresh outfall particulates, on older, refractory material buried in sediments,
or utilize chemosynthetic symbiotic bacteria. Results are discussed in the context of declining bottom
oxygen conditions along the coast.
We examine effects of high river particulate flux and municipal wastewater effluent on heterotrophicorganic carbon cycling in coastal subtidal sediments. Heterotrophic production was a predictable(r2 = 0.95) proportion (56%) of oxidized OC flux and strongly correlated with organic/inorganic flux. Consistentgrowth efficiencies (36%) occurred at all stations. Organic biomass was correlated with total, OCand buried OC fluxes, but not oxidized OC flux. Near the river, production was modest and biomass high,resulting in low P/B. Outfall deposition resulted in depleted biomass and high bacterial production,resulting in the highest P/B. These patterns explain why this region is production ‘‘saturated’’. Thed15N in outfall effluent, sediments and dominant taxa provided insight into where, and which types oforganisms feed directly on fresh outfall particulates, on older, refractory material buried in sediments,or utilize chemosynthetic symbiotic bacteria. Results are discussed in the context of declining bottomoxygen conditions along the coast.
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