Ocean Indicators 2007
The Good News—2007 was an extraordinary year in that the ocean was cold during winter 2006–2007, and the transition from winter downwelling to summer upwelling conditions began very early. Zooplankton thus changed to a "boreal subarctic" or "cold water" community beginning in late March. Spring upwelling was also the second strongest observed during April–May for the past 10 years. These observations point to excellent ocean conditions for salmon early in 2007. Thus, juvenile coho and spring Chinook entering the ocean in spring 2007 encountered some of the best conditions for survival observed since 2000.
The Bad News—The bottom waters of the continental shelf were cold and relatively salty throughout the summer. In fact, cold, deep waters in 2007 were the saltiest that we have recorded in 10 years of measurements. They were also the 4th coldest in 10 years (only 1999, 2001, and 2002 were colder). However, upwelling of these waters was not effective during June to August, so these cold waters were not brought to the sea surface. Thus, despite the existence of a source of very cold and nutrient–rich water on the sea floor, summer surface waters never cooled. Rather, the sea surface temperatures (SST) at our baseline stations 5 miles off Newport were, on average, the 8th warmest since 1998. Summer–averaged SST at the NOAA weather buoy off Newport (Buoy 46050) was the 9th warmest (the warmest temperatures were observed during the devastating 1998 El Niño event).
These mixed signals in 2007 may provide insight as to which indicators are most important to juvenile salmon. For example, the weak upwelling in early summer and prevalence of warm sea–surface temperatures may indicate whether conditions during the first month or two at sea are more critical than average conditions during the first summer. We hope to discover what the necessary conditions are for very good survival and when these conditions are most critical.
Pacific Decadal Oscillation—The PDO was positive from November 2002 until mid–2006, indicating warm ocean conditions, a situation that is unfavorable for good salmon survival (Figure 1a). However, during much of 2007, the PDO was in a neutral state, with a summer (May–September) average of +0.2, but an annual averaged of –0.2. The PDO turned negative in September and strongly negative in Oct–Dec. These strongly negative values reflect the development of La Niña conditions at the equator—a harbinger of good things to come in 2008.
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| Figure 1a. |
Top, center, and bottom panels respectively show summer average PDO and MEI, temperature anomalies at NOAA Buoy 46050, and anomalies of copepod species diversity (richness) from 1996–2008. |
Multivariate ENSO Index—The MEI has been positive in most months since spring 2002, but turned strongly negative in July 2007 (Figure 1). As of February 2008, the MEI continues strongly negative—in fact as negative as in 1999—signaling the development of La Niña conditions (cold ocean conditions), in the eastern Pacific. This development is a good sign for the overall productivity of the California Current and a positive indicator for salmon survival in 2008.
Sea Surface Temperature—Sea surface temperatures at NOAA Weather Buoy 46050 (20 miles off Newport) were slightly cooler than average for most months of 2006 and 2007, with the notable exception of summer 2007 (Figure 1a). Summer SSTs were anomalously warm averaging 2.8 and 1.5°C warmer in July and August, respectively than the 15–year averages for those months. Likewise, SSTs at NH–05 (our baseline station 5 miles off Newport) were quite warm during summer 2007, reflecting weak upwelling conditions.
However, as an indicator of ocean conditions for salmon, SST is also important during the winter before salmon enter the ocean, as well as the winter during their first year at sea. The winter of 2006–2007 had the coldest SST in 10 years, a very positive sign for salmon that entered the sea in April–May 2007. As for winter 2007–2008, the SST has continued to be cold through February, another harbinger of good times to come for salmon.
Coastal Upwelling—Upwelling began relatively early in 2007, in mid–March. However upwelling did not become strong until the first week of May. Regardless, the April–May average was the second highest of the past 10 years.
Deep Water Temperature and Salinity—Temperature and salinity is measured every 2 weeks at the 50–m depth from our baseline station, NH 05. These measurements showed that deep waters in spring and summer 2007 were very cold and relatively salty. In fact, salinities were the highest that we have measured since we began making CTD measurements off Newport in 1997, and temperatures were the 4th coldest. Cold, salty water is nutrient–rich; thus a good harbinger for high primary production. However, as noted above in the SST section, warmer–than–average SST values dominated this summer. These surface temperatures indicated that the deep nutrient–rich water did not reach the sea surface, thus productivity was probably low during the summer of 2007.
Copepod Species Biodiversity (Richness)—Copepods track the PDO and SST quite closely. A positive PDO and warm SST are consistently accompanied by a copepod community that is more diverse than that during a negative PDO and cool SSTs. Copepod species richness anomalies were negative in 2007, a good indicator.
Northern Copepod Anomalies—Northern copepods are those which originate in the Gulf of Alaska, and their presence indicates the presence of large volumes of coastal water transported from the north into the northern California Current. Positive values of this index indicate a higher–than–average biomass of northern (cold water) copepods and vice versa (Figure 18).
The northern copepod index was strongly positive in 2007, a very good indicator that recruitment and growth of baitfish should have been good in summer 2007, and if true, growth conditions for juvenile salmonids were probably good as well.
Biological Spring Transition—We know that ocean currents off Washington, Oregon and California exhibit a seasonal reversal. When this transition is early, salmon generally do well; when late, they do poorly. Although the physical transition to the upwelling season began early in 2007, strong upwelling was not established until early May (Figure 20). The biological transition (the time when the copepod community switched from a winter warm water community to a summer cold water community) was also prolonged, first occurring on 30 March but not becoming firmly established until 4 May.
Length of the Upwelling Season—This is a new indicator this year and is based on the difference between the first date when a summertime, cold–water copepod community was seen in the spring and the last date that a summertime cold–water community was seen in the autumn. In 2007 the biological upwelling season was average in length (Table 2).
Catches of Spring Chinook in June—Trawl surveys in June and September are funded by the Bonneville Power Administration. These surveys follow eight transect lines running from Newport, Oregon, north to La Push, Washington. In June 2007, we collected the third highest number of juvenile spring Chinook in our 10 years of sampling, suggesting improved adult spring Chinook runs can be expected in 2009 (Figure 22).
Catches of juvenile coho in September—Warm ocean conditions continued to prevail throughout the summer and perhaps as a result, our juvenile salmon trawl survey in September produced some of the lowest catches of juvenile coho (7th worse in 10 years of surveys). Since it is widely believed that juvenile coho live only within the upper few meters of the water column, we hypothesize that the anomalously warm waters, in some way, led to the demise of the juvenile coho. (Figure 22).
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