Ocean Ecosystem Indicators 2008
During 2008, the trend of cold ocean conditions, which started to become established in 2007, has continued. By the end of August, all of our ocean indicators remained highly favorable for the growth and survival of salmon that entered the ocean in spring and summer 2008. In fact, by the end of the upwelling season in September, when all of our indicators are averaged, 2008 will almost certainly be the most outstanding of the past 11 years. Moreover, these excellent ocean conditions bode well for other marine fish and bird species, since many of them will almost certainly have a good recruitment year.
Below we discuss each of our indicators in the context of how our measurements in 2008 compare to those made by our research team since the late 1990s. Actual values for each indicator are listed in Table 1.
Pacific Decadal Oscillation—Neutral values of the PDO were seen through most of 2007; however, in September 2007, PDO values turned negative, indicating a cold–phase PDO and cold California Current. The PDO continued strongly negative through August 2008 (Figure 5). When we compare PDO behavior over the past 11 years, we find the most negative value for winter occurred in winter 1999–2000, and the second most negative value in winter 2007–2008. This is an important leading indicator: Logerwell et al. (2003) showed that one prerequisite for good coho salmon survival is a cold winter preceding the spring when fish enter the sea. We assume that the same is true for yearling Chinook salmon.
PDO values for summer also indicate that 2008 can be characterized as a year of greatly improved ocean conditions: through August, PDO values were the most negative in the 11–year time series (Figure 2). Should the PDO remain strongly negative through September, the year 2008 will have the most negative summer PDO since the 1950s!
Multivariate ENSO Index—The MEI has been negative since June 2007 and has continued negative through 2008 (Figure 4). This indicates La Niña, and cold ocean conditions in equatorial waters of the eastern Pacific. La Ni�a conditions affect the Northeast Pacific through an atmospheric teleconnection, and generally result in colder–than–normal temperatures. Averaged from January to June 2008, the MEI had its most negative value of the last 11 years: lower values have not been seen since 1988 (and before that, since 1975). Thus, a strongly negative MEI index is not only unusual, but is another indicator that the ocean has transitioned into a state highly favorable for salmon survival.
Sea Surface Temperature—In line with the strongly negative PDO and MEI, sea surface temperatures in 2008 have been among the coolest of our 11–year time series. Wintertime SSTs were the coldest in 11 years, and summertime SSTs at oceanographic station NH 05 (5 miles off Newport) and at NOAA Buoy 46050 (22 miles off Newport; Figure 5) were the second and third coldest. The coldest values were in the years 2000 and 2002 respectively. As mentioned in the PDO section, a cold winter is a necessary condition (but not sufficient) for high growth and survival rates of salmon that enter the sea the following spring.
Coastal Upwelling—Upwelling was initiated early in the year (day 88; 28 March), but did not become strong until one month later on 28 April. Winds remained steady through much of the summer except for a brief lull (and southwesterly storms) in mid–August. Winds resumed in September, and although they have been steady, they have not been strong compared to those of the last 11 years. Thus it is likely that upwelling in 2008 will be regarded as average.
Deep Water Temperature and Salinity—Temperature and salinity is recorded every 2 weeks during our biweekly monitoring cruises. At baseline station NH 05 (5 miles off Newport), the coldest and saltiest water in our time series, which began in 1997, was measured during 2008 (Figure 12 and Figure 12a). This means that nutrient–rich water was on the shelf during the entire upwelling season. The fact that SST values at NH 05 were relatively low indicates that winds were sufficiently strong to bring upwelled water to the surface, promoting high rates of phytoplankton production. Thus, 2008 may be among the most productive years of the past decade. This situation contrasts with that of summer 2007, when very cold, deep water was observed on the shelf but seldom reached the sea surface, as shown by the relatively high SST values during 2007 (see Table 1). Thus productivity was almost certainly much lower in 2007 than in 2008.
Copepod Species Biodiversity (Richness)—Monthly measures of copepod species composition track those of the PDO and SSTs quite closely (Figure 15). When the PDO is negative, surface waters are cold, and the copepod community is dominated by only a few cold–water, subarctic species; when the PDO is positive, SSTs are warm, and the community is dominated by a greater number of warm–water, subtropical copepod species. To date, we have found moderately low species–richness values during 2008. These values are similar to those observed in the 1999–2002 cool phase of the PDO.
Northern Copepod Anomalies—Cold–water copepods originate from the coastal Gulf of Alaska and are referred to as "northern copepods." Their presence indicates that Gulf of Alaska waters are being fed into the coastal California Current. The index is based on average biomass from May to September, so these values will not be available until sometime in October. However, we have examined the samples taken to date, and they are once again dominated by cold–water species, a positive sign.
Of particular interest in 2008 (and 2007) has been the presence in large numbers of the very large and lipid–rich Neocalanus species. They frequently occur off the Oregon coast during winter and spring months, and their presence indicates the presence of subarctic waters off Oregon. However, during both 2007 and 2008, the species Neocalanus plumchrus has been roughly 5 times more abundant than during the previous "cold phase" of the PDO. Moreover, high numbers were seen far offshore—to at least 125 miles from shore—suggesting that the more oceanic species of fishes, such as sablefish, will also benefit.
Biological Spring Transition—Coastal currents off Washington, Oregon, and northern California flow from the north in spring/summer and from the south in fall/winter. These currents are driven by coastal winds: southward–flowing currents result from winds blowing from the north (towards the south) in summer; northward–flowing currents result from winds blowing from the south (towards the north) in winter. Currents from the north bring zooplankton from the Gulf of Alaska in spring and summer, while currents from the south bring zooplankton of subtropical origin. The "dates" when these currents reverse are referred to as the spring or fall transitions. In some years the transition is ill–defined in that the currents and winds do not reverse suddenly with seasonal change. The biological spring transition is defined as the date when the zooplankton community has transitioned from a warm–water "winter" community to a cold–water "summer" community. During 2008, the transition came very early, in early March (day 63). This is a positive sign for fisheries because it means that the food chain was populated by northern species very early in the year.
Several methods are used to calculate dates of the spring transition (including the biological index discussed above), and these can be seen at the University of Washington's Columbia River DART (Data Access in Real Time) project.
Catches of Spring Chinook in June—Pelagic trawl surveys have been carried out for 11 years (since 1998). In the June 2008 survey, we collected the highest number of juvenile spring Chinook salmon of the 11–year time series (Figure 22); this is a harbinger for strong returns of Columbia River Chinook beginning in 2010.
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