Sampling aboard the NOAA ship Bell M. Shimada has been progressing smoothly and we have completed two of our highest priority transects: the Newport Hydrographic Line and the Crescent City Line off northern California. The Crescent City Line is important because it is south of Cape Blanco, a known biogeographic break, where upwelling is generally weaker to the north and stronger to the south- possibly fueling different plankton communities.
Along the Newport Line, we encountered warm surface water from 200 nm offshore to nearshore. On Monday we were sampling 150 miles off Crescent City and encountered 18°C surface water with a physical signature similar to what we came across on the Newport Line. However, by our next offshore station, 125 miles offshore, surface waters were 16°C and they continued to cool as we moved onshore. At our most nearshore station, the water column was well-mixed and surface water was closer to 11°C.
After downloading the recent MODIS satellite image (thanks to Maria Kavanaugh who is onboard), we could see from the image that south of Cape Blanco the surface waters are cooler than north of Cape Blanco, and there was a distinct filament of cooler water being advected off Cape Blanco. Interestingly, while processing one of the offshore samples off Crescent City, we found species that we'd normally encounter nearshore. Possibly they were transported offshore via this jet?
The plankton community along the Crescent City Line was also more dynamic compared to Newport. We caught large euphausiids at several offshore stations and larger copepods, including mature Calanus at nearshore stations. Historically, for our NCC surveys, we see a significant uptick in krill abundance along the Crescent City Line. Dinoflagellates still dominated the phytoplankton community, but we sampled a community with abundant diatoms at our two most nearshore stations.
We shall see what our samples look like as we continue the survey and head north of Cape Blanco, into what the satellite image says is warmer waters with high chlorophyll concentrations.