deliberately excluded shrimp (Thom et al., 1994), and while these measurements would represent tide 
flat habitats that have no shrimp, such areas are only 16% of the total Yaquina tide flat area (DeWitt et 
al., 2004). Thus, because of these uncertainties, benthic flux measurements from those four studies 
(Dollar et al. 1991; Garber et al. 1992; Thom et al. 1994; Lamed 2003) were not used for estimating 
the estuary-scale nutrient fluxes presented in Table 3.1 for the Yaquina Estuary. 
Sediment 
Advection 
Bioturbation 
Deposit Feeding 
Filter Feeding 
0 2 , DOM, 
Seston 
Neotrypaea califomiensis burrows 
Upogebia pugettensis burrows 
GED-- /I 
_ A 
Nutrients 
Seston 
Predators 
j| Tide 
Remineralization 
Particulate —» Dissolved 
Organic -» Inorganic 
Bioirrigation 
Figure A. 1 Conceptual model of the dominant processes (boxes) driving carbon and nutrient flux 
(arrows) between the benthos and water column in Pacific Northwest estuaries. 
To avoid this problem, DeWitt et al. (2004) inserted 1-m deep core barrels into sediments at 
their study sites, and fit benthic chambers to the tops of the core barrels to isolate water, sediments, 
shrimp and burrows inside the chamber from the outside world. Core barrels were inserted > 1 Od 
before the chamber tops were attached so that shrimp enclosed in the barrel could construct new 
burrow openings within the chamber. DeWitt et al. (2004) produced estuary-scale maps of benthic- 
pelagic fluxes of N0 3 + N0 2 , NH/, and DIN for Yaquina Estuary (Figures A.2 and A.3) by linking 
estuarine-scale maps of burrowing shrimp populations to density-dependent flux measurements. DIN 
fluxes had great spatial variability owing to the differences in shrimp species and abundance across the 
n 
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