ACCESS partners have been investigating the spatial and temporal relationships between oceanographic processes, zooplankton, and marine birds and mammals in the region surrounding Cordell Bank and Gulf of the Farallones.
Ongoing surveys started in May 2004. Three to four cruises are conducted annually between April and October. Thirty four (34) cruises have been completed to date and 3 more cruises have been planned for 2013.
Research updates to 2012
Average ocean year in 2012
Alongshore winds (strong = blue, weak = red) are responsible for driving upwelling. Winds were strong in early 2012, followed by a relaxation period, then remained relatively weak to average. Intermittent strong winds were observed in 2004, followed by weak winds in 2005-06. Strong winds were consistent through the spring and summer months of 2007-08. Winds started to wane in 2009 and have remained relatively weak to average since then.
The spring transition that marks the beginning of the upwelling season in each year occurred at a very early date compared to the long-term average in 2012. This is similar to the early spring transitions observed in 2006-09 and in contrast to the late transitions observed in 2005 and 2010.
Sea surface temperature (cold = blue, warm = red) measured by the NOAA buoy near Bodega Bay showed cold temperatures for most months in 2012. In 2004, sea surface temperatures were relatively warm but close to the long-term averages. Warm temperatures were observed in 2005-06, followed by cold surface temperatures in 2007-09. Sea surface temperatures in 2010 were warm early in the year and cold for all other months, and temperatures have remained relative cold since.
Pacific-scale climate indices have shown great variability in ocean conditions since the start of our research in 2004. Overall, results from 2012 showed a productive ocean state. From 2005 to 2009, PDO and NPGO were following opposite trends; a positive PDO and negative NPGO values indicated poor ocean conditions in 2005-06, while a negative PDO and positive NPGO indicated productive ocean conditions in 2007-08. Since mid-2009, both PDO and NPGO have been following relatively parallel trends; a positive PDO and NPGO indicated productive ocean conditions during 2010, despite the year being deemed an El Niño year. These indices showed signs of diverging in mid-2012.
Strong upwelling = more zooplankton
Zooplankton community composition results are not yet available for 2011-12, but results to date illustrate the effects of improved ocean conditions on overall zooplankton abundance, with low abundances in poor ocean condition years (2004-06), followed by a significant increase in zooplankton abundance in 2007-08 (particularly for copepods and euphausiids [also known as krill]). Zooplankton abundance appears to decline again in 2009, and preliminary results from 2010 show increased zooplankton abundance.
Strong upwelling = more adult krill and fatty copepods
Zooplankton communities were different between poor and productive years. Gelatinous zooplankton dominated under poor ocean conditions from 2004-2006. Northern copepod species (i.e., large, fatty copepods) reappeared in the study region starting in 2007.
The abundance of adult krill as indicated by our Tucker trawl samples declined during periods of low productivity. Relatively high abundances of adult krill (main prey of fish, auklets, and whales) were caught in June 2012, although the proportion declined as the year progressed. Overall, abundance of adult krill was low during the anomalous ocean conditions of 2005-06, as well as summer and fall of 2009. In the productive years of 2007-08 and 2010, almost all of the krill were adults.
Copepod community composition results are not yet available for 2011-12. Results to date indicate a large increase in the abundance of boreal (northern) copepods in 2007, 2008 and in the spring of 2009 and 2010, when cold, productive ocean conditions prevailed in our region. Species common to mid-latitudes (transition zone copepods) also became more abundant in 2007, although not as dramatically. Equatorial copepods (i.e., copepods from southern latitudes) increased in abundance in the September cruises of 2007 and 2008, likely when the equatorward California Current flow relaxed.
Good times for the Cassin’s auklet (the krill-eater)
The Cassin’s auklet, a zooplanktivorous seabird, mainly ate euphausiids (krill) in most years, including in 2012. Mysids were the dominant prey in 2005-06 (poor ocean condition years), and the Cassin’s auklet experienced unprecedented breeding failure (see figure below). Increasing amounts of krill in the diet since those years has coincided with increasing productivity on the Farallon Islands from 2007 to 2011.
Average times for the common murre (the fish-eater)
The common murre, an omnivorous seabird species, fed mostly on juvenile rockfish, smelt and squid in 2012. Common murre diet shows predominantly rockfish in the 1970s and 1980s, then mostly pelagic anchovy and sardine in the 1990s and mid-2000s, and back to rockfish under recent improved ocean conditions (2008-12). In general, poor ocean conditions correspond to a lower percentage of rockfish in the diet and reduced productivity for murres on the Farallones (see figure below).
Increasing trends for krill and Humpback Whales
While results for 2012 are not yet available, acoustic measurements on krill in the upper 200 m of the water column have shown an overall increase in krill biomass through time. Krill biomass had low abundances overall from 2004 to 2007. The apparent high abundance in spring 2006 is due to high abundance of highly reflective gelatinous zooplankton in the water at that time. High krill biomass was observed in 2009 and 2010, despite the later year being deemed an El Niño year. Krill biomass remained relatively high in 2011, although not as high as the previous two years.
The Humpback Whale, a main predator of krill, follows very similar patterns to the krill abundance. Years of lower krill abundance (2004-07) have corresponded to low abundance of Humpback Whales in the region. Signs of increasing Humpback Whales abundance began in 2008, and almost five times as many whales were sighted in the summer and fall of 2010 compared to the first four years of the study. This rise in whale abundance coincided with the great krill biomass observed in 2010 and 2011.