ANALYSIS OF PARTICULATE ORGANIC MATTER DISTRIBUTION ALONG SURFACE WATERS OF THE CALIFORNIA CURRENT

Kylie Welch1, Miguel Goni2, Yvan Alleau2, Lauren Smith2

OBJECTIVE: To use high resolution sampling of the concentrations of particulate organic carbon (POC) and nitrogen (PN) to provide a comprehensive picture of the spatial distribution of particulate organic matter along the California Current.

APPROACH: Approximately 1500 samples were collected aboard the R/V Wecoma over the course of 28 days during August 2011 via a semi-automated filtration system1 (as shown below). Additional measurements of temperature, salinity, transmittance, and beam attenuation were taken in-situ to establish characteristics of the different regions. Back at the lab, the samples were dried, acidified and analyzed for POC and PN concentrations. The data were then analyzed to evaluate patterns and resulting relationships.

STUDY AREA: The cruise started in Newport, Oregon and then traveled to Northern Washington, down to Southern California, and back up to Newport. (See path below.)

ACKNOWLEDGEMENTS: We would like to thank the captain and crew of the R/V Wecoma as well as chief scientists Laurie Juranek and Richard Feely. Funding for this project was provided by the National Science Foundation and Oregon State University Honors College via the Grandma Honors Travel Award, the DeLoach Work Scholarship and Chambers Environmental Fund.

1 Holster et al., “Design and application of a semi-automated filtration system to study the distribution of particulate organic carbon in the water column of a costal upwelling system.” MARINE CHEMISTRY, 123(1-4), (2011): 67-77.

Path of the cruise taken by R/V Wecoma. The path was divided into three sections based on characteristics (North, Middle, and South) and then further divided into A and B based on whether the samples were collected along the initial path or along the return path.

Observations:• POC concentrations are greater overall in the Northern transects, with most values ranging

from 5 – 28 µmol.• The Middle transects show the lowest concentration of POC of all three regions with ranges

of 3 – 11 µmol.• POC in the Southern transects lie between the other two with a range of about 5 – 17 µmol.• Overall, POC concentrations are higher closer to shore and lower farther from shore.

Particulate Organic Carbon

Particulate Nitrogen

Observations:• Greater concentrations of PN are seen in the Northern transects with a range of 0.6 – 3.5

µmol.• Lower concentrations of PN are seen in the Middle transects with a range of 0.3 – 1.8 µmol,

though B) has a much smaller median than A).• The Southern transects have a moderate amount of PN, ranging from 0.5 – 2 µmol.• Once again, we see higher PN values closer to shore and much lower values farther offshore.

Beam Attenuation

Observations:• Cp values are greater in the Northern transects with most values ranging between 0.3 and

1.08 cm-1.• The Middle transects once again show the lowest values with a range of 0.25 - 0.45 cm-1.• The Southern transects have a range of 0.25 – 0.6 cm-1.• As we have seen before, the higher values of Cp are found closer to shore and the lower

values farther offshore.

Particle Distribution Particle Composition

Conclusions

The water mass characteristics along the Pacific Coast are shown by constrasting temperature and salinity associated with the different regions. Maps above show temperature and salinity changes over temporal and spatial differences. To the right is a plot depicting the temperature vs salinity relationships found in each transect. Transect A) North is where the Columbia River is located, thus it is much less salty than the other regions of the Pacific Coast, and has an influence on much of the area nearby. The colder, saltier characteristics, particularly in A) and B) Middle transects, provide evidence of recently upwelled water.

Hydrography

Initial Interpretations:• The greatest values of POC, PN, and Cp are seen in the Northern transects, indicating

probable influence of the Columbia river on productivity and biomass.• Greater values inshore versus offshore suggests higher biomass and productivity.

1 University Honors College, 229 Strand Hall, Oregon State University, Corvallis, OR 2 College of Earth, Ocean, and Atmospheric Sciences, 104 CEOAS Administration Building, Corvallis, OR

The analysis of this data set demonstrates spatial patterns in the distribution and composition of particulate organic matter along the California Current. These patterns show a general coherence with the distribution of chlorophyll derived from satellite based measurements during the time period of the cruise.

Molar C:N Ratio

Observations:• Particulate organic C:N ratios are greatest in

transect A) North (range of 7 – 10) with lesser values in the Middle transects (5 to 7).

• There is a general positive correlation between POC and PN with different regions displaying variable relationships.

Observations:• There is a general positive

correlation between POC and Cp with differences among water masses.

• High ratios occur in the Northern transect and low ratios occur in the Middle transect.

Initial Interpretations: The composition of the particles in the regions of A) North and A) Middle are different from the other transects. This could be further evidence of the influence from the Columbia River.

POC:Beam Attenuation

Continued research in this area will focus on further characterization of the organic matter and analysis of suspended particles collected from different regions of the water column.

Our initial results show the feasibility of this high resolution approach to quantify standing stocks of POM in ocean margin regions.

Introduction

PO

C (m

M)

PO

C (m

M)

PN

(m

M)

PN (mM)