14 March 2016
by Nanci Bompey
Nanci Bompey is AGU’s public information manager. She is spending a week aboard the R/V Oceanus with scientists from Oregon State University who are studying the role that small rivers play in the productivity of the coastal ocean during the winter. Click here to read Nanci’s previous blogs from this trip.
On Sunday afternoon, we headed back to Newport. The scientists and crew were closely watching the weather to see when we will be able to head back on the water.
The down time gives Goni and his team some time to filter water samples that were collected from the Newport Hydrographic Line on Friday. The samples are one piece of a larger project trying to figure out how small coastal rivers are influencing coastal ocean productivity during the winter.
There are about 30 USGS-monitored rivers stretching from Northern California to Washington. During the winter, when there are heavy rains, these rivers can send huge amounts of water – up to three to four times more than the Columbia River — into the coastal ocean. Winds push this freshwater up against the shore, potentially affecting the coastal ocean for weeks.
The river water contains both particulate organic matter as well as dissolved organic matter. Scientists think the particulate matter stays close to the shore, feeding zooplankton that potentially feed larger organisms up the food chain. They think that the dissolved materials, which don’t sink, travel further away from the shore and are broken down by microbes. These microbes release nutrients that can be used by phytoplankton to perform photosynthesis and produce organic compounds that fuel the food chain. One way to look at it is: could the organic matter exported by watersheds this winter affect next summer’s crab season?
The additional filtering that Goni and his team performed on Sunday is looking at the dissolved material piece of this puzzle. The filtering separates out the water from the organic material dissolved in it. The dissolved organic material that is captured on extraction columns will then be analyzed back in the lab at OSU. There, the team will look for certain compounds that come from plants on land, called lignins. By quantifying the amount of lignin in the samples, the researchers can tell how much of the dissolved organic matter in the water is coming from the land.
They can also look at how the amount of lignin changes in water samples with varying amounts of salinity. Lignin acts as a biomarker for the land-derived dissolved organic material in the water. In some cases, the researchers have seen greater declines in the amount of lignin than expected, indicating that microbes are degrading the dissolved organic matter to produce nutrients that feed phytoplankton.
Next up is the sampling along the Umpqua River line further down the Oregon coast. Stayed tuned.