Fall AGU Meeting (Dec. 2002) COAST abstracts:

• Allen
  
• Bane et al.
  
• Barth et al.
  
• Carney et al.
  
• Couch et al.
  
• Cowles et al.
  
• Dale et al.
  
• Durski et al.
  
• Egbert et al.
  
• Gan et al.
  
• Hales et al.
  
• Kosro et al.
  
• Kuebel et al.
  
• Kurapov et al.
  
• Perlin et al.
  
• Pierce et al.
  
• Ruttenberg et al.
  
• Samelson
  
• Spitz et al.
  
• Wheeler
  

Abstracts should be cited as:

EOS Trans. AGU, 83 (47),
Fall Meet. Suppl.,
Abstract XXXXX-XX, 2002

OS62A-0229

Spatial and Temporal Patterns of Dissolved Phosphorus Distribution
in Coastal Waters of Central Oregon

K C Ruttenberg and S T Dyhrman

As part of the CoOP-funded COAST project, we have analyzed 0.4 um-
and 0.2 um-filtered water samples for Total Dissolved Phosphorus
(TDP), Soluble Reactive Phosphorus (SRP, sometimes referred to
as Dissolved Inorganic Phosphate (DIP), or simply phosphate). The
difference between TDP and SRP provides an estimate of Dissolved
Organic Phosphorus (DOP) concentration.  Dissolved phosphorus
(P) analyses are complete for the Spring (May 2001) and Summer
(August 2001) cruises of the seasonal COAST study. Surface water
samples from these two cruises have also been analyzed for bulk
water Alkaline phosphatase (APase), a phosphohydrolytic enzyme
that can render DOP compounds bioavailable, as well as for cell-
specific APase using Enzyme Labeled Fluorescence (ELF). Depth
profiles of TDP, DOP and SRP from both spring and summer cruises
show highest DOP concentrations occur in the upper water column,
but that many of the deeper water samples also contain resolvable
DOP. In spring, DOP ranges from 10-40% of TDP in the upper 40
m of the water column, with highest proportions (30-40%) in the
upper 5 m. DOP concentrations range from undetectable to 0.5 uM.
In summer, DOP in the upper 10 m of the water column ranges as high
as 80% of TDP, averaging 40%. The average fraction of DOP in the
upper 20 m in summer is 22-28%, for 0.4 and 0.2 um filtered water,
respectively. DOP concentrations in summer range from undetectable
to as high as 1.8 uM. Thus in summer, the segregation of the DOP
concentration maxima to the upper water column is compressed into
the upper 20 m, and DOP concentrations are significantly higher. In
spring, in contrast, DOP maxima are expanded to occupy the upper
40 m, and concentrations are lower. Bulk-water (e.g., unfiltered)
Alkaline phosphatase activity is present in surface waters during
both spring and summer, but can only be clearly resolved in samples
with low levels of SRP. More samples showed ELF activity than showed
APase activity, illustrating the higher degree of sensitivity of
the ELF technique over the standard fluorometric technique applied
to bulk waters. The fluorometric technique is now being applied
to particulate samples concentrated from bulk waters, and improved
detection is anticipated, permitting us to resolve Apase activities
in samples for which activities in the bulk water are too low. The
presence of APase activity in waters with low SRP yet high DOP
concentrations suggests that DOP may play a role in meeting the
phytoplankton phosphorus demand in this system.