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Diatoms dominate spring bloom phytoplankton assemblages in temperate waters and coastal upwelling regions of the global ocean. Copepods usually dominate the zooplankton in these regions and are the prey of many larval fish species. Recent laboratory studies suggest that diatoms may have a deleterious effect on the success of copepod egg hatching. These findings challenge the classical view of marine food-web energy flow from diatoms to fish by means of copepods. Egg mortality is an important factor in copepod population dynamics, thus, if diatoms have a deleterious in situ effect, paradoxically, high diatom abundance could limit secondary production. Therefore, the current understanding of energy transfer from primary production to fisheries in some of the most productive and economically important marine ecosystems may be seriously flawed. Here we present in situ estimates of copepod egg hatching success from twelve globally distributed areas, where diatoms dominate the phytoplankton assemblage. We did not observe a negative relationship between copepod egg hatching success and either diatom biomass or dominance in the microplankton in any of these regions. The classical model for diatom-dominated system remains valid.

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]

Most modeling and statistical approaches encourage simplicity, yet ecological processes are often complex, as they are influenced by numerous dynamic environmental and biological factors. Pacific salmon abundance has been highly variable over the last few decades and most forecasting models have proven inadequate, primarily because of a lack of understanding of the processes affecting variability in survival. Better methods and data for predicting the abundance of returning adults are therefore required to effectively manage the species. We combined 31 distinct indicators of the marine environment collected over an 11-year period into a multivariate analysis to summarize and predict adult spring Chinook salmon returns to the Columbia River in 2012. In addition to forecasts, this tool quantifies the strength of the relationship between various ecological indicators and salmon returns, allowing interpretation of ecosystem processes. The relative importance of indicators varied, but a few trends emerged. Adult returns of spring Chinook salmon were best described using indicators of bottom-up ecological processes such as composition and abundance of zooplankton and fish prey as well as measures of individual fish, such as growth and condition. Local indicators of temperature or coastal upwelling did not contribute as much as large-scale indicators of temperature variability, matching the spatial scale over which salmon spend the majority of their ocean residence. Results suggest that effective management of Pacific salmon requires multiple types of data and that no single indicator can represent the complex early-ocean ecology of salmon. [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 ocean survival of coho salmon ( Oncorhyncus kisutch) off the Pacific Northwest coast has been related to oceanographic conditions regulating lower trophic level production during their first year at sea. Coastal upwelling is recognized as the primary driver of seasonal plankton production but as a single index upwelling intensity has been an inconsistent predictor of coho salmon survival. Our goal was to develop a model of upwelling-driven meso-zooplankton production for the Oregon shelf ecosystem that was more immediately linked to the feeding conditions experienced by juvenile salmon than a purely physical index. The model consisted of a medium-complexity plankton model linked to a simple one-dimensional, cross-shelf upwelling model. The plankton model described the dynamics of nitrate, ammonium, small and large phytoplankton, meso-zooplankton (copepods), and detritus. The model was run from 1996 to 2007 and evaluated on an interannual scale against time-series observations of copepod biomass. The model's ability to capture observed interannual variability improved substantially when the copepod community size distribution was taken into account each season. The meso-zooplankton production index was significantly correlated with the ocean survival of hatchery coho salmon from the Oregon production area, although the coastal upwelling index that drove the model was not itself correlated with survival. Meso-zooplankton production within the summer quarter (July-September) was more strongly correlated with coho survival than was meso-zooplankton production in the spring quarter (April-June). [ABSTRACT FROM AUTHOR]

Seasonal and inter-annual variability in the abundance and biomass of copepodid stages of the sub-arctic oceanic copepod, Neocalanus plumchrus, was studied during the January–May growth season, using an 11-yr time series of zooplankton samples collected over the upper 100 m of the water column. Abundance and biomass peaks occur in March/April. Abundance and biomass of N. plumchrus were significantly negatively correlated with sea surface temperature and significantly positively correlated with sea surface chlorophyll a, salinity, and density above the pycnocline. The seasonal integrated abundance and biomass of N. plumchrus declined during the warm years (2003–05), and increased during the cold years (2006–08). The date when 50% of the population had passed through stage C5 was significantly negatively correlated with temperature – earlier in warm years and later in cold years. In 3 yr (2003, 2007 and 2008), a second cohort appeared in mid-May, as indicated by the presence of stages C1 and C2 in the samples. Unusually high abundances of N. plumchrus in the spring of 2007 and 2008 were associated with cool ocean temperatures and an early spring transition in the NCC ecosystem, suggesting that the NCC ecosystem has returned to a cold phase. We discuss the merits of a hypothesis that the N. plumchrus population observed off Oregon is a local population as opposed to one that is expatriated from the Gulf of Alaska. [ABSTRACT FROM AUTHOR]

Abstract: Growth rates and intermolt periods for Euphausia pacifica were determined from individual growth rate (IGR) experiments carried out over a 7-year period (2000–2006) on euphausiids collected off the Oregon Coast. Adult growth rates averaged 0.020mm total length (TL) day−1 during the summer upwelling season and 0.011mm TL day−1during the winter downwelling season. Average intermolt period (IMP) was 8d during upwelling and 11d during downwelling. Growth rates and IMPs were highly variable, and were not related to surface chl-a concentration or length of the euphausiid. Negative growth occurred at all times of year. Negative growth rates during winter downwelling were most likely related to poor feeding conditions, while negative growth rates during the summer upwelling season were likely a result of the euphausiids investing ingested energy towards reproduction rather than somatic growth. Growth rates from this study using the IGR method were generally lower than E. pacifica growth rates from other studies that used the cohort analysis method. Since negative growth rates are difficult to capture using cohort analysis, we calculated a seasonal growth rate using only the positive values from our experiments to compare with cohort analysis growth rates. These seasonal positive growth rates were 0.08mmTLd−1 (2.4mmmonth−1) for the upwelling season and 0.04mmTLd−1 (1.2mmmonth−1) for the downwelling season, equivalent to weight-specific growth rates of 0.0135d−1 (upwelling) and 0.0089d−1 (downwelling), and are comparable to rates obtained in other studies using cohort analysis. Highest annual growth rates during upwelling were measured in 2004 (warm) and 2006 (cold), suggesting that E. pacifica is less affected by warm and cool periods than other types of zooplankton, such as copepods. [Copyright &y& Elsevier]

Peterson, J. O., and Peterson, W. T. 2008. Influence of the Columbia River plume (USA) on the vertical and horizontal distribution of mesozooplankton over the Washington and Oregon shelf. – ICES Journal of Marine Science, 65: 477–483.River plumes extending out over continental shelf waters have distinct frontal boundaries along their leading edges that concentrate highly buoyant particles, including zooplankton. The margin between the base of the plume and the underlying oceanic waters is often many times larger in spatial extent than the visible surface front, but the influence of this region of a river plume on the vertical and horizontal distribution of zooplankton is less well understood. Using a laser optical plankton counter (LOPC) and a conductivity–temperature–depth sensor (CTD) mounted to a rapidly undulating tow body, we examined the horizontal and vertical distribution of zooplankton proximate to the Columbia River plume, to study how plume waters affect zooplankton over the continental shelf. Overall, vertically integrated zooplankton abundance and biovolume was elevated close to “aged” plume waters. Zooplankton tended to aggregate near the surface close to river plume waters. When plume waters are present at the surface, zooplankton aggregations tended to be in the upper 10 m of the water column, compared with 25 m when the plume was not present. The presence of river plumes may be ecologically and energetically important to surface feeding planktivores such as larval and juvenile fish. [ABSTRACT FROM PUBLISHER]

Previous studies of zooplankton communities off the central Oregon coast have been primarily descriptive or have focused on only a few taxa. To more formally explore patterns in zooplankton community structure, we used cluster analysis, Non-metric Multidimensional Scaling (NMDS) ordination, and Indicator Species Analysis to examine seasonal, El Nin˜o/La Nin˜a, and onshore/offshore differences in community composition. Hydrographic and zooplankton data were collected off Newport, Oregon (44.7°N) at eight stations between 8 and 105 km from shore (60-2900 m water depth), on 15 cruises between Jan 1998 and Sept 2000 as part of the US GLOBEC Northeast Pacific Long-Term Observation Program. Zooplankton were collected with a 202 μm, 0.5 m diameter ring net lifted vertically at 30 m min−1 from 100 m, to the surface.The 1997/1998 El Nin˜o played an important role in structuring the zooplankton community from the beginning of our sampling in January 1998 through November 1998. The “El Nin˜o” group identified by cluster analysis and NMDS ordination was highly diverse and was characterized by taxa with offshore and subtropical neritic affinities. When the El Nin˜o group was present, there was no onshelf-offshelf gradient in community composition as was seen during “normal” summers. The “El Nin˜o” group was preceded and followed by a “Transitional” group with slightly lower diversity that existed through the spring of 1999. By summer 1999, conditions had returned to “normal.”Summer upwelling strongly affected the structure of zooplankton assemblages in the “normal” years of 1999 and 2000, leading to differences between nearshore and offshore zooplankton groups. The zooplankton assemblages sampled on the continental shelf during these summers were unique, composed of boreal neritic species (such as the copepods Calanus marshallae, Pseudocalanus mimus, and Acartia longiremis) and larvae of several meroplanktonic taxa, whereas the off-shelf assemblages resembled the winter zooplankton assemblages which were comprised of subtropical neritic and Transition Zone species. The spatial extent of the continental shelf group present during the summer upwelling season varied between early and late summer; differences may be related to the integrated strength and duration of the north winds over the upwelling season. [Copyright &y& Elsevier]

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.

The article presents information on the 2010 Sendai Zooplankton Workshop held on April 25, 2010 in Sendai, Japan. The workshop's aim was to provide an opportunity for those keenly interested in "how data on zooplankton and krill can be used to better understand and forecast the impacts of climate change on fisheries" to discuss the topic in an informal workshop atmosphere.

Abstract: We synthesize information on changes in ecosystems of the North Pacific at seasonal, interannual, and event time scales. Three approaches are used to cope with inadequate temporal, spatial and trophic resolution in generating this synthesis. First, we use highly spatially and temporally resolved data on physical forcing and chlorophyll (SeaWiFS data from 1998 to 2005) to describe basin-wide spatial patterns and seasonal to interannual time scales. The second approach is to compare time series of zooplankton at selected spatial sites at which sampling resolution is sufficient to describe seasonal biomass/abundance patterns, and where multiple years of data exist to examine interannual variability. The third approach is to infer trophic relationships, and broaden the first two approaches to higher trophic levels, by examining the impacts of several event scale phenomena on many trophic levels, but only over a rather limited geographic region. The 8years of satellite chlorophyll data clearly show that interannually persistent seasonal patterns exist in most regions in the North Pacific, even in the tropical waters. From frequency analysis (Lomb periodograms), the annual cycle was the strongest in most regions, but in the tropics and eastern boundary current regions, periods greater than 1year were significant. In mid- to high-latitude regions, periods of less than 1year were also significant in addition to the annual period indicating double peaks with varying intervals. Seasonal progression of the timing of annual peak chlorophyll concentration in the North Pacific showed a different pattern compared with the Atlantic or Indian Ocean, largely due to the presence of the subarctic high nutrient–low chlorophyll (HNLC) and equatorial upwelling regions, which had later phytoplankton blooms than would have been predicted based on a simple equatorial to pole progression of bloom timing. Seasonal cycles in zooplankton were more or less synchronized (concomitant with or slightly lagged) with those of phytoplankton with a few exceptions. Exceptions occur in the Eastern Subarctic Gyre where annual peaks of chlorophyll occur in autumn, after the peak in zooplankton biomass. Interannual variation of annually averaged chlorophyll in 30 regions show three patterns, one positively related to El Niño, one negatively related to El Niño, and one with longer-scale variation, possibly related to climate regimes. Nine regions did not match any of the three patterns. Interannual variation in zooplankton abundance/biomass from selected regions indicates that El Niño may be the major source of interannual variability with its effects modulated by longer-scale variation, such as by the Pacific Decadal Oscillation. Two well-documented environmental events in the Northern California Current, in 2002 and 2005, exemplify how short-term disruption in atmospheric forcing causes changes in ocean hydrography and circulation that has significant impacts on primary production and ripple effects throughout multiple trophic levels of the ecosystem. We conclude that a closer look at the data often yields interesting results that might not necessarily be gained by considering the broad generalizations. Specifically, we observe that short-term disruptions of the ecosystem at the primary producer level may impact higher trophic levels in nonlinear ways that lead to unpredic impacts when one considers the entire food chain. [Copyright &y& Elsevier]

Morphological taxonomic methods are currently insufficient to satisfy the rising demand for taxonomic information and rapid sample turnover required to support conservation and resource management efforts. Next generation DNA sequencing (NGS) is capable of rapidly producing taxonomic assessments for a broad diversity of organisms present in environmental samples. To achieve taxonomic coverage of similar breadth, multiple morphologists who tend to specialize by taxonomic group would be required. Unfortunately, both morphological and molecular approaches are subject to various methodological biases. Accurate assessment (both taxonomic composition and abundances) of marine zooplankton assemblages is a critical component of effective ecosystem-based conservation and resource management efforts. To address this need and determine the extent of agreement between methods, morphological data was compared to 454 NGS results for zooplankton assemblages collected in plankton net tows from northern Monterey Bay, California. Results indicate areas of agreement between data sets, but also characterize biases specific to each method. Morphological analyses provided life history stage and biomass information for many zooplankton taxa. The NGS data included 313 bp from the 3′ end of the mitochondrial cytochrome- c -oxidase subunit-I ( COI ; 3234 OTUs) region and 365 bp from the 5′ end of the large subunit of the nuclear ribosomal RNA ( 28S ; 1669 OTUs). Results of NGS analysis corroborated the presence of 40 of the 61 morphologically identified genera and species. For some organisms, NGS provided finer taxonomic resolution where morphological data or knowledge was limited. Correlations between biomass and NGS percent sequence abundances were significant for some, but not all taxa, and were gene-specific in some cases (i.e., COI —Diplostraca, Polychaeta, Callianassidae, Clausocalanidae, Oncaeidae, Podonidae, Evadne , Neotrypaea , Oncaea , Podon , Psuedocalanus ; 28S —Euphausiacea, Euphausiidae, Oncaeidae, Oncaea ). Despite various methodological biases, both data sets were in agreement with respect to alpha diversity indices generated for zooplankton assemblages collected at four sampling stations. These results suggest that a partnership between morphological and molecular methods represents a powerful tool, that when used appropriately, can effectively extend taxonomic assessment capabilities to better address present needs. [ABSTRACT FROM AUTHOR]

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]

Ecosystem indicators track information about states and trends in ocean systems and are a valuable tool for ecosystem assessment and management. To ensure that indicators are used appropriately in both science and management contexts, it is important to understand the extent to which they represent broader spatial patterns. In the Northern California Current (NCC) off the Oregon and Washington state coasts in the USA, copepod metrics derived from data collected at a well-sampled station on the Newport Hydrographic (NH) Line ('NH05', five nmi offshore from Newport, OR, USA) are commonly used as indicators of the region's general ocean conditions. Using correlation analyses, we examined the utility of NH05 as a sentinel station (i.e. representative of a broader region) with respect to the abundance and biomass of warm-water and cold-water copepods in the NCC. Copepod correlations between NH05 and other locations in the NCC were higher for the warm-water copepods than the cold-water group, with correlations being slightly higher for abundance than biomass. Paracalanus parvus had the highest NH05 correlations among the warm-water copepod species, and Acartia longiremis had the highest NH05 correlations among the cold-water copepod species. We also broadened our analysis to evaluate other sampling sites as sentinel stations and found that some sites were equally or more representative of copepod dynamics in the NCC than NH05, though none of these sites tend to be sampled as often as NH05. This analysis emphasized that the warm-water copepods tend to be more similarly distributed in the NCC than the cold-water copepods, and thus their changes through time are better captured by most stations. In contrast, correlations among the cold-water copepods in the NCC vary by location and appear to be strongly related to depth, with the highest correlations at mid-shelf stations. • Copepod abundance correlations were higher than biomass correlations at NH05. • Warm-water copepods correlations were higher than cold-water copepod correlations. • Cold-water copepod correlations were related to station depth. • Paracalanus parvus had the highest correlations among the warm-water copepods. • Acartia longiremis had the highest correlations among the cold-water copepods. [ABSTRACT FROM AUTHOR]