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The zooplankton of the northern California Current are typically characterized by an abundance of lipid-rich copepods that support rapid growth and survival of ecologically, commercially, and recreationally valued fish, birds, and mammals. Disruption of this food chain and reduced ecosystem productivity are often associated with climatic variability such as El Niño events. We examined the variability in timing, magnitude, and duration of positive temperature anomalies and changes in copepod species composition in the northern California Current in relation to 10 tropical El Niño events. Measurable impacts on mesozooplankton of the northern California Current were observed during seven of 10 of these events. The occurrence of anomalously warm water and the response of the copepod community was rapid (lag of zero to 2 months) following the initiation of canonical Eastern Pacific (EP) events, but delayed (lag of 2-8 months) following 'Modoki' Central Pacific ( CP) events. The variable lags in the timing of a physical and biological response led to impacts in the northern California Current peaking in winter during EP events and in the spring during CP events. The magnitude and duration of the temperature and copepod anomalies were strongly and positively related to the magnitude and duration of El Niño events, but were also sensitive to the phase of the lower frequency Pacific Decadal Oscillation. When fisheries managers and biological oceanographers are faced with the prospect of a future El Niño event, prudent management and observation will require consideration of the background oceanographic conditions, the type of event, and both the magnitude and duration of the event when assessing the potential physical and biological impacts on the northern California Current. [ABSTRACT FROM AUTHOR]

Fisheries oceanography is the study of ecological relationships between fishes and the dynamics of their marine environments and aims to characterize the physical, chemical, and biological factors that affect the recruitment and abundance of harvested species. A recent push within the fisheries management community is toward ecosystem-based management. Here, we show how physical and biological oceanography data can be used to generate indicators of ocean conditions in an ecosystem context, and how these indicators relate to the recruitment of salmonids, sablefish, sardines, and rockfish in the California Current. [ABSTRACT FROM AUTHOR]

Few fisheries oceanography surveys in the United States have sampled hydrography and ichthyoplankton or juvenile fishes for 15 years or more. We describe six long time series surveys, including three from the California Current System, and one each from Alaska (Gulf of Alaska, Bering Sea, and the Arctic), the Northeast US Shelf, and the Gulf of Mexico. We examine the applications of long time series data as well as the output of published analyses, Web-based graphical summaries, and quality controlled data to the broader scientific community (including resource managers and stakeholders). Potential improvements to the surveys using new technologies are evaluated, and possible changes in survey design are discussed. We conclude with a summary of the benefits derived from these long time series fisheries oceanography surveys and make the case for their continuation. [ABSTRACT FROM AUTHOR]

The goal of the Pacific Ocean Boundary Ecosystem and Climate Study (POBEX) was to diagnose the large-scale climate controls on regional transport dynamics and lower trophic marine ecosystem variability in Pacific Ocean boundary systems. An international team of collaborators shared observational and eddy-resolving modeling data sets collected in the Northeast Pacific, including the Gulf of Alaska (GOA) and the California Current System (CCS), the Humboldt or Peru-Chile Current System (PCCS), and the Kuroshio-Oyashio Extension (KOE) region. POBEX investigators found that a dominant fraction of decadal variability in basin- and regional-scale salinity, nutrients, chlorophyll, and zooplankton taxa is explained by a newly discovered pattern of ocean-climate variability dubbed the North Pacific Gyre Oscillation (NPGO) and the Paciic Decadal Oscillation (PDO). NPGO dynamics are driven by atmospheric variability in the North Paciic and capture the decadal expression of Central Pacific El Niños in the extratropics, much as the PDO captures the low-frequency expression of eastern Pacific El Niños. By combining hindcasts of eddy-resolving ocean models over the period 1950-2008 with model passive tracers and long-term observations (e.g., CalCOFI, Line-P, Newport Hydrographic Line, Odate Collection), POBEX showed that the PDO and the NPGO combine to control low-frequency upwelling and alongshore transport dynamics in the North Pacific sector, while the eastern Paciic El Niño dominates in the South Pacific. Although different climate modes have diferent regional expressions, changes in vertical transport (e.g., upwelling) were found to explain the dominant nutrient and phytoplankton variability in the CCS, GOA, and PCCS, while changes in alongshore transport forced much of the observed long-term change in zooplankton species composition in the KOE as well as in the northern and southern CCS. In contrast, cross-shelf transport dynamics were linked to mesoscale eddy activity, driven by regional-scale dynamics that are largely decoupled from variations associated with the large-scale climate modes. Preliminary indings suggest that mesoscale eddies play a key role in ofshore transport of zooplankton and impact the life cycles of higher trophic levels (e.g., fish) in the CCS, PCCS, and GOA. Looking forward, POBEX results may guide the development of new modeling and observational strategies to establish mechanistic links among climate forcing, mesoscale circulation, and marine population dynamics. [ABSTRACT FROM AUTHOR]

We examined variability in growth rate during the larval stage of northern anchovy ( Engraulis mordax) in response to physical and biological environmental factors in 2005 and 2006. The onset of spring upwelling was anomalously delayed by 2-3 months until mid-July in 2005; in contrast, spring upwelling in 2006 began as a normal year in the northern California Current. Larval and early juvenile E. mordax were collected in August, September, and October off the coast of Oregon and Washington. Hatch dates ranged from May to September, with peaks in June and August in 2005 and a peak in July in 2006, based on the number of otolith daily increments. Back-calculated body length-at-age in the June 2005 hatch cohort was significantly smaller than in the August 2005 cohort, which had comparable growth to the July 2006 cohort. Standardized otolith daily increment widths as a proxy for seasonal variability in somatic growth rates in 2005 were negative until late July and then changed to positive with intensification of upwelling. The standardized increment width was a positive function of biomass of chlorophyll a concentration, and neritic cold-water and oceanic subarctic copepod species sampled biweekly off Newport, Oregon. Our results suggest that delayed upwelling in 2005 resulted in low food availability and, consequently, reduced E. mordax larval growth rate in early summer, but once upwelling began in July, high food availability enhanced larval growth rate to that typical of a normal upwelling year (e.g., 2006) in the northern California Current. [ABSTRACT FROM AUTHOR]

The synchrony between coastal and shelf-slope copepod communities was investigated in the northern California Current (NCC) system, a strong upwelling zone, using time series of zooplankton sampled from a nearshore station (9 km offshore, water depth 62 m) and a shelf-slope station (46 km offshore, water depth 297 m). Long-term trends and seasonal changes were constructed for the dissimilarity index (Euclidean distance) between the two stations and for the biomass of three different copepod assemblages at the two stations: cold neritic, southern, and warm neritic copepods. The dissimilarity between the community structures of the two stations showed little variation in the long-term trend, but exhibited a clear seasonal pattern. All three copepod assemblages showed similar long-term trends in relation to the large-scale forcing as indexed by the Pacific Decadal Oscillation at both stations, but variations in the long-term trend at the nearshore station were much higher than the offshore station. Most copepod groups exhibited regular seasonal patterns at both stations except southern copepods at the nearshore station. All three copepod assemblages exhibited more pronounced seasonal fluctuations at the nearshore station compared with the slope station, and this difference is likely driven by higher productivity nearshore fueled by nutrient-enriched upwelled water. Copepods in the inshore and offshore waters in the NCC ecosystem showed synchronized response to the large-scale variability in physical forcing and copepods in the coastal waters were more responsive to local perturbations than were those in the slope waters. [ABSTRACT FROM AUTHOR]

The article offers information on the impact of elevated sea surface temperatures (SSTs) or warm blob on the physical and biological oceanography of the northern California Current (NCC). It mentions that the blob of warm surface waters in the North Pacific in 2015 had been presented since the summer of 2014 and was associated with North Pacific High (NPH). It discusses the study about the impact of the condition on zooplankton species in the area.

We evaluated copepod taxonomic diversity as a potential biological indicator of ocean conditions in the northeast Pacific Ocean using data collected biweekly between May 1996 and December 2004 and from 1969 to 1973 and 1983 off Newport, Oregon. During the summer, low copepod biodiversity is accompanied by high biomass, with the opposite patterns prevailing in the winter. High biodiversity, and associated low biomass, is also observed during the summers of major El Nino events (1983, 1997-1998) and during years when the Pacific Decadal Oscillation is in a positive phase. From 1996 to the present, seasonally adjusted monthly anomalies of taxa richness and the Shannon-Weiner diversity index were compared to hydrographic and meteorological variables and to basin-wide climatological indices. Correlations of biodiversity with physical variables were strongest during the summer months for the Multivariate El Nino/Southern Oscillation Index, temperatures at a water depth of 50 m, and the Pacific Decadal Oscillation. During a 4-year cool period (1999-2002), biodiversity was low, likely a result of the increased transport of coastal subarctic waters into the northern California current. In recent years (2002-2005), however, there has been a dramatic increase in biodiversity. These increases may be attributable to the influence of a weak El Nino event in 2003; yet, high biodiversity persisted through the summer of 2005 and at times was higher than during the strongest El Nino events of the 20th century (1983 and 1997-1998). Our analyses suggest that changes in source waters, driven by remote basin scale forcing and not local environmental events, cause interannual-to-decadal variations in copepod biodiversity in the northern California current. [ABSTRACT FROM AUTHOR]

Reported trends in the mean and variability of coastal upwelling in eastern boundary currents have raised concerns about the future of these highly productive and biodiverse marine ecosystems. However, the instrumental records on which these estimates are based are insufficiently long to determine whether such trends exceed preindustrial limits. In the California Current, a 576-year reconstruction of climate variables associated with winter upwelling indicates that variability increased over the latter 20th century to levels equaled only twice during the past 600 years. This modern trend in variance may be unique, because it appears to be driven by an unprecedented succession of extreme, downwelling-favorable, winter climate conditions that profoundly reduce productivity for marine predators of commercial and conservation interest. [ABSTRACT FROM AUTHOR]

Highlights: [•] We designed seasonal environmental multivariate indicators (MOCI). [•] MOCI reproduced known temporal variability and key events of anomalous conditions. [•] Subtropical transport decreased, subarctic increased, and upwelling intensified. [•] Seasonal MOCI did not relate to chlorophyll-a concentrations or krill abundance. [•] Seasonal MOCI explained variability in copepod biomass and seabird breeding success. [Copyright &y& Elsevier]

Both simple and more complex lower trophic ecosystem models were applied to the near shore pelagic zone of the California Current System. The ecosystem models were a simple nitrogen–phytoplankton–zooplankton (NPZ) model derived from that of Edwards et al. (J. Mar. Res. 58, 37–60, 2000), and a modified version of the more complex PICES North Pacific Ecosystem Model for Understanding Regional Oceanography (NEMURO), which includes both nitrogen and silicate cycles, as well as multiple phytoplankton and zooplankton components. These models were framed within two simplified physics models, similar to those constructed by Newberger et al. (J. Geophys. Res. 108 (3), 3061, doi:10. 1029/2001JC001182, 2003). The first physics model was a zero-dimensional closed system, used for structural analysis of the biological models. The second was a one-dimensional (horizontal, with no vertical structure) cross-shelf model of the mixed layer, used to examine the biological response to upwelling. The predictions of the two biological models within the one-dimensional physical framework were compared with observed nutrients, chlorophyll, and zooplankton on the Newport Hydrographic Line. Equilibrium behavior of the zero-dimensional models was similar to that in previous studies; differences between the models resulted primarily from differences in the density dependence of mortality. Both models were found to be highly sensitive to the same four parameters: source nitrate concentration, maximum grazing rate, zooplankton Ivlev constant, and zooplankton mortality rate. In the cross-shelf case, both biological models had a similar timing of phytoplankton response to upwelling, but maximum phytoplankton concentration and zooplankton dynamics differed, with the simpler NPZ model resulting in lower dissolved nutrients but higher plankton densities than the modified NEMURO model. While the modified NEMURO model provided a slightly better overall fit to observations, neither model was able to fully capture observed phytoplankton and zooplankton dynamics. [Copyright &y& Elsevier]