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Morrow, RM, Ohman MD, Goericke R, Kelly TB, Stephens BM, Stukel MR.  2018.  CCE V: Primary production, mesozooplankton grazing, and the biological pump in the California Current Ecosystem: Variability and response to El Nino. Deep-Sea Research Part I-Oceanographic Research Papers. 140:52-62.   10.1016/j.dsr.2018.07.012   AbstractWebsite

Predicting marine carbon sequestration in a changing climate requires mechanistic understanding of the processes controlling sinking particle flux under different climatic conditions. The recent occurrence of a warm anomaly (2014-2015) followed by an El Nino (2015-2016) in the southern sector of the California Current System presented an opportunity to analyze changes in the biological carbon pump in response to altered climate forcing. We compare primary production, mesozooplankton grazing, and carbon export from the euphotic zone during quasi-Lagrangian experiments conducted in contrasting conditions: two cruises during warm years - one during the warm anomaly in 2014 and one toward the end of El Nino 2016 - and three cruises during El Ninoneutral years. Results showed no substantial differences in the relationships between vertical carbon export and its presumed drivers (primary production, mesozooplankton grazing) between warm and neutral years. Mesozooplankton fecal pellet enumeration and phaeopigment measurements both showed that fecal pellets were the dominant contributor to export in productive upwelling regions. In more oligotrophic regions, fluxes were dominated by amorphous marine snow with negligible pigment content. We found no evidence for a significant shift in the relationship between mesozooplankton grazing rate and chlorophyll concentration. However, massspecific grazing rates were lower at low-to-moderate chlorophyll concentrations during warm years relative to neutral years. We also detected a significant difference in the relationship between phytoplankton primary production and photosynthetically active radiation between years: at similar irradiance and nutrient concentrations, productivity decreased during the warm events. Whether these changes resulted from species composition changes remains to be determined. Overall, our results suggest that the processes driving export remain similar during different climate conditions, but that species compositional changes or other structural changes require further attention.

Stephens, BM, Porrachia M, Dovel S, Roadman M, Goericke R, Aluwihare LI.  2018.  Nonsinking Organic Matter Production in the California Current. Global Biogeochemical Cycles. 32:1386-1405.   10.1029/2018gb005930   AbstractWebsite

Productive eastern boundary upwelling systems such as the California Current Ecosystem (CCE) are important regions for supporting both local and remote food webs. Several studies have reported on the temporal and spatial variability of primary production and gravitational export in the CCE. However, few studies have quantified the partitioning of net primary and new production into other reservoirs of detrital organic matter. This study tested the hypothesis that nonsinking detrital reservoirs are an exportable reservoir of new production in the CCE with samples collected by the California Cooperative Oceanic Fisheries Investigation survey between 2008 and 2010. Water column gradients in nitrate (NO3-) and total organic carbon (TOC; which excludes sinking particulate organic carbon) were used to estimate potential rates of new production (P-New) and TOC production (P-TOC), respectively. The P-TOC:P-New varied between 0.16 and 0.56 and often increased with indicators of enhanced autotrophic production. At times, surface stratification was also correlated with elevated P-TOC:P-New. In the most productive, inshore region, P-TOC exceeded previously reported sinking export rates, which identified TOC as a quantitatively significant repository of exportable carbon in the CCE. However the sum of P-TOC and sinking export for these productive regions was less than both P-New and oxygen-based estimates of net community production. These results imply that nonsinking reservoirs alone are not sufficient to explain observed imbalances between production and export for the most productive CCE regions. Plain Language Summary The ocean's biological pump is typically quantified as the organic carbon that quickly sinks, that is, is exported, out of the surface lighted zone to be subsequently sequestered in the deep ocean. Recent studies have shown that other forms of organic matter produced by phytoplankton can also contribute to carbon export. In this study, we quantified how much new production and net primary production was channeled into nonsinking reservoirs such as dissolved organic carbon and suspended particulate organic carbon in the productive eastern boundary California Current Ecosystem. To match the data coverage provided by our organic carbon measurements we used satellite data to calculate net primary production and used measured depth profiles of nitrate together with model-derived upwelling velocities, to determine new production. We quantified the amount of nonsinking organic matter that accumulated in surface waters following production and found that the timescale of accumulation enabled this reservoir to participate in export. In some regions, as much carbon was present in the accumulated nonsinking reservoir as was quantified as sinking particulate carbon. We also found that lateral export from the productive coastal region was a potentially important pathway that could carry nutrients and carbon in organic matter to less productive waters.

Lindegren, M, Checkley DM, Koslow JA, Goericke R, Ohman MD.  2018.  Climate-mediated changes in marine ecosystem regulation during El Nino. Global Change Biology. 24:796-809.   10.1111/gcb.13993   AbstractWebsite

The degree to which ecosystems are regulated through bottom-up, top-down, or direct physical processes represents a long-standing issue in ecology, with important consequences for resource management and conservation. In marine ecosystems, the role of bottom-up and top-down forcing has been shown to vary over spatio-temporal scales, often linked to highly variable and heterogeneously distributed environmental conditions. Ecosystem dynamics in the Northeast Pacific have been suggested to be predominately bottom-up regulated. However, it remains unknown to what extent top-down regulation occurs, or whether the relative importance of bottom-up and top-down forcing may shift in response to climate change. In this study, we investigate the effects and relative importance of bottom-up, top-down, and physical forcing during changing climate conditions on ecosystem regulation in the Southern California Current System (SCCS) using a generalized food web model. This statistical approach is based on nonlinear threshold models and a long-term data set (similar to 60years) covering multiple trophic levels from phytoplankton to predatory fish. We found bottom-up control to be the primary mode of ecosystem regulation. However, our results also demonstrate an alternative mode of regulation represented by interacting bottom-up and top-down forcing, analogous to wasp-waist dynamics, but occurring across multiple trophic levels and only during periods of reduced bottom-up forcing (i.e., weak upwelling, low nutrient concentrations, and primary production). The shifts in ecosystem regulation are caused by changes in ocean-atmosphere forcing and triggered by highly variable climate conditions associated with El Nino. Furthermore, we show that biota respond differently to major El Nino events during positive or negative phases of the Pacific Decadal Oscillation (PDO), as well as highlight potential concerns for marine and fisheries management by demonstrating increased sensitivity of pelagic fish to exploitation during El Nino.

Stukel, MR, Song H, Goericke R, Miller AJ.  2018.  The role of subduction and gravitational sinking in particle export, carbon sequestration, and the remineralization length scale in the California Current Ecosystem. Limnology and Oceanography. 63:363-383.   10.1002/lno.10636   AbstractWebsite

Particles and aggregates created in the surface layers of the ocean are transported not only by gravity, but also by the horizontal and vertical advection of the surrounding water. Subduction, in particular, can transport organic matter from the surface ocean to the mesopelagic in a manner that is not likely to be detected by typical in situ carbon export measurements (e.g., sediment traps and U-238-Th-234 disequilibrium). To assess the importance of subduction to the biological pump, we combined in situ sediment trap, thorium, primary productivity, and particulate organic carbon (POC) measurements with a data-assimilative physical circulation model and a Lagrangian particle tracking model. We develop a simple parameterization of two alternative particle sinking processes (Phytoplankton-Fecal Pellet [PFP] and Aggregation) using results from 13 extensively sampled water parcels in the California Current Ecosystem. Both parameterizations suggested that subduction is an important, at times dominant, mechanism of POC vertical export in the region (median 44% and 23% contribution to total POC export for PFP and Aggregate parameterizations at the 100-m depth horizon). The percentage contribution of subduction was highly variable across water parcels (ranging from 7% to 90%), with subduction typically more important in offshore, oligotrophic regions. On average the fate of particles that are passively transported out of the surface layer by advection is different from that of particles that sink across the 100-m depth horizon. Subducted particles were predominantly remineralized shallower than 150 m, while approximately 50% of gravitationally exported POC was remineralized at depths > 500 m.

Nezlin, NP, McLaughlin K, Booth JAT, Cash CL, Diehl DW, Davis KA, Feit A, Goericke R, Gully JR, Howard MDA, Johnson S, Latker A, Mengel MJ, Robertson GL, Steele A, Terriquez L, Washburn L, Weisberg SB.  2018.  Spatial and temporal patterns of chlorophyll concentration in the Southern California Bight. Journal of Geophysical Research-Oceans. 123:231-245.   10.1002/2017jc013324   AbstractWebsite

Distinguishing between local, anthropogenic nutrient inputs and large-scale climatic forcing as drivers of coastal phytoplankton biomass is critical to developing effective nutrient management strategies. Here we assess the relative importance of these two drivers by comparing trends in chlorophyll-a between shallow coastal (0.1-16.5 km) and deep offshore (17-700 km) areas, hypothesizing that coastal regions influenced by anthropogenic nutrient inputs may have different spatial and temporal patterns in chlorophyll-a concentration from offshore regions where coastal inputs are less influential. Quarterly conductivity-temperature-depth (CTD) fluorescence measurements collected from three southern California continental shelf regions since 1998 were compared to chlorophyll-a data from the more offshore California Cooperative Fisheries Investigations (CalCOFI) program. The trends in the coastal zone were similar to those offshore, with a gradual increase of chlorophyll-a biomass and shallowing of its maximum layer since the beginning of observations, followed by chlorophyll-a declining and deepening from 2010 to present. An exception was the northern coastal part of SCB, where chlorophyll-a continued increasing after 2010. The long-term increase in chlorophyll-a prior to 2010 was correlated with increased nitrate concentrations in deep waters, while the recent decline was associated with deepening of the upper mixed layer, both linked to the low-frequency climatic cycles of the Pacific Decadal Oscillation and North Pacific Gyre Oscillation. These large-scale factors affecting the physical structure of the water column may also influence the delivery of nutrients from deep ocean outfalls to the euphotic zone, making it difficult to distinguish the effects of anthropogenic inputs on chlorophyll along the coast.

Wells, BK, Schroeder ID, Bograd SJ, Hazen EL, Jacox MG, Leising A, Mantua N, Santora JA, Fisher J, Peterson WT, Bjorkstedt E, Robertson RR, Chavez FP, Goericke R, Kudela R, Anderson C, Lavaniegos BE, Gomez-Valdes J, Brodeur RD, Daly EA, Morgan CA, Auth TD, Field JC, Sakuma K, McClatchie S, Thompson AR, Weber ED, Watson W, Suryan RM, Parrish J, Dolliver J, Loredo S, Porquez JM, Zamon JE, Schneider SR, Golightly RT, Warzybok P, Bradley R, Jahncke J, Sydeman W, Melin SR, Hildebrand JA, Debich AJ, Thayre B.  2017.  State Of The California Current 2016-17: Still Anything But "Normal" In The North. California Cooperative Oceanic Fisheries Investigations Reports. 58:1-55. AbstractWebsite

This report examines the ecosystem state of the California Current System (CCS) from spring 2016-spring 2017. Basin-scale indices suggest conditions that would support average to below average coast-wide production across the CCS during this time period. Regional surveys in 2016 sampled anomalously warm surface and subsurface waters across the CCS. Chlorophyll concentrations were low across the CCS in 2016 and, concomitant with that, copepod communities had an anomalously high abundance of subtropical species. Early in 2017 conditions between northern, central, and southern CCS were dissimilar. Specifically, surface conditions north of Cape Mendocino remained anomalously warm, chlorophyll was very low, and subtropical copepods were anomalously abundant. Southern and central CCS surveys indicated that environmental conditions and chlorophyll were within normal ranges for the longer time series, supporting an argument that biophysical conditions/ecosystem states in the southern and central CCS were close to normal. Epipelagic micronekton assemblages south of Cape Mendocino were generally close to longer-term average values, however the northern assemblages have not returned to a "normal" state following the 2014-15 large marine heatwave and 2016 El Nino. North of Cape Mendocino the epipelagic micronekton was largely composed of offshore and southern derived taxa. We hypothesize that stronger-than-typical winter downwelling in 2017 and a reduced spawning biomass of forage taxa are contributors to the anomalous forage community observed in the north. Also of note, surveys indicate northern anchovy (Engraulis mordax) abundance was greater than average (for recent years) and nearer shore in northern regions. Finally, record-low juvenile coho and Chinook salmon catches in the 2017 northern CCS salmon survey suggest that out-migrating Columbia Basin salmon likely experienced unusually high early mortality at sea, and this is further supported by similarities between the 2017 forage assemblage and that observed during poor outmigration survival years in 2004, 2005, and 2015. Generally, the reproductive success of seabirds in 2016 (the most current year available) was low in the north but near average in central California. At Yaquina Head off Oregon and Castle Rock off northern California some of the lowest reproductive success rates on record were documented. In addition to reduced abundance of prey, there was a northward shift of preferred seabird prey. Seabird diets in northern areas also corroborated observations of a northward shift in fish communities. Nest failure was attributed to a combination of bottom-up and top-down forces. At Castle Rock, most chicks died of starvation whereas, at Yaquina Head, most nests failed (95% of common murre, Uria aagle) due to disturbance by bald eagles (Haliaeetus leucocephalus) seeking alternative prey. Mean bird densities at sea for the 2017 surveys between Cape Flattery Washington and Newport Oregon were the lowest observed and may indicate continued poor reproductive performance of resident breeders in 2017. South of Cape Mendocino, where forage availability was typical, seabird reproductive success was also below average for most species in 2016, but did not approach failure rates observed in the north. Finally, in 2017, abundances of seabirds observed at-sea off southern California were anomalously high suggesting an improved foraging environment in that area. Marine mammal condition and foraging behavior were also impacted by the increased abundance and shifting distribution of the northern anchovy population. Increases in the abundance of northern anchovy in the Southern California Bight coincided with improved condition of sea lion (Zalophus californianus) pups in 2016. Namely, lipid-rich northern anchovy occurred in great frequencies in the nursing female diet. Increases in northern anchovy nearshore in the central and northern CCS may have also contributed to a shoreward shift in distribution of humpback whales (Megaptera -novaeangliae) in these regions. These shifts along with recovering humpback whale populations contributed to recent increases in human-whale interactions (e.g., fixed-gear entanglements).

Stukel, MR, Aluwihare LI, Barbeau KA, Chekalyuk AM, Goericke R, Miller AJ, Ohman MD, Ruacho A, Song H, Stephens BM, Landry MR.  2017.  Mesoscale ocean fronts enhance carbon export due to gravitational sinking and subduction. Proceedings of the National Academy of Sciences of the United States of America. 114:1252-1257.   10.1073/pnas.1609435114   AbstractWebsite

Enhanced vertical carbon transport (gravitational sinking and subduction) at mesoscale ocean fronts may explain the demonstrated imbalance of new production and sinking particle export in coastal upwelling ecosystems. Based on flux assessments from U-238:Th-234 disequilibrium and sediment traps, we found 2 to 3 times higher rates of gravitational particle export near a deep-water front (305 mg C.m(-2).d(-1)) compared with adjacent water or to mean (nonfrontal) regional conditions. Elevated particle flux at the front wasmechanistically linked to Fe-stressed diatoms and high-mesozooplankton fecal pellet production. Using a data assimilative regional ocean model fit to measured conditions, we estimate that an additional similar to 225 mg C.m(-2).d(-1) was exported as subduction of particle-rich water at the front, highlighting a transport mechanism that is not captured by sediment traps and is poorly quantified by most models and in situ measurements. Mesoscale fronts may be responsible for over a quarter of total organic carbon sequestration in the California Current and other coastal upwelling ecosystems.

Lindegren, M, Checkley DM, Ohman MD, Koslow JA, Goericke R.  2016.  Resilience and stability of a pelagic marine ecosystem. Proceedings of the Royal Society B-Biological Sciences. 283   10.1098/rspb.2015.1931   AbstractWebsite

The accelerating loss of biodiversity and ecosystem services worldwide has accentuated a long-standing debate on the role of diversity in stabilizing ecological communities and has given rise to a field of research on biodiversity and ecosystem functioning (BEF). Although broad consensus has been reached regarding the positive BEF relationship, a number of important challenges remain unanswered. These primarily concern the underlying mechanisms by which diversity increases resilience and community stability, particularly the relative importance of statistical averaging and functional complementarity. Our understanding of these mechanisms relies heavily on theoretical and experimental studies, yet the degree to which theory adequately explains the dynamics and stability of natural ecosystems is largely unknown, especially in marine ecosystems. Using modelling and a unique 60-year dataset covering multiple trophic levels, we show that the pronounced multi-decadal variability of the Southern California Current System (SCCS) does not represent fundamental changes in ecosystem functioning, but a linear response to key environmental drivers channelled through bottom-up and physical control. Furthermore, we show strong temporal asynchrony between key species or functional groups within multiple trophic levels caused by opposite responses to these drivers. We argue that functional complementarity is the primary mechanism reducing community variability and promoting resilience and stability in the SCCS.

Stukel, MR, Kahru M, Benitez-Nelson CR, Decima M, Goericke R, Landry MR, Ohman MD.  2015.  Using Lagrangian-based process studies to test satellite algorithms of vertical carbon flux in the eastern North Pacific Ocean. Journal of Geophysical Research-Oceans. 120:7208-7222.   10.1002/2015jc011264   AbstractWebsite

The biological carbon pump is responsible for the transport of similar to 5-20 Pg C yr(-1) from the surface into the deep ocean but its variability is poorly understood due to an incomplete mechanistic understanding of the complex underlying planktonic processes. In fact, algorithms designed to estimate carbon export from satellite products incorporate fundamentally different assumptions about the relationships between plankton biomass, productivity, and export efficiency. To test the alternate formulations of export efficiency in remote-sensing algorithms formulated by Dunne et al. (2005), Laws et al. (2011), Henson et al. (2011), and Siegel et al. (2014), we have compiled in situ measurements (temperature, chlorophyll, primary production, phytoplankton biomass and size structure, grazing rates, net chlorophyll change, and carbon export) made during Lagrangian process studies on seven cruises in the California Current Ecosystem and Costa Rica Dome. A food-web based approach formulated by Siegel et al. (2014) performs as well or better than other empirical formulations, while simultaneously providing reasonable estimates of protozoan and mesozooplankton grazing rates. By tuning the Siegel et al. (2014) algorithm to match in situ grazing rates more accurately, we also obtain better in situ carbon export measurements. Adequate representations of food-web relationships and grazing dynamics are therefore crucial to improving the accuracy of export predictions made from satellite-derived products. Nevertheless, considerable unexplained variance in export remains and must be explored before we can reliably use remote sensing products to assess the impact of climate change on biologically mediated carbon sequestration.

Brzezinski, MA, Krause JW, Bundy RM, Barbeau KA, Franks P, Goericke R, Landry MR, Stukel MR.  2015.  Enhanced silica ballasting from iron stress sustains carbon export in a frontal zone within the California Current. Journal of Geophysical Research-Oceans. 120:4654-4669.   10.1002/2015jc010829   AbstractWebsite

Nutrient dynamics, phytoplankton rate processes, and export were examined in a frontal region between an anticyclone and a pair of cyclones 120 km off the coast in the southern California Current System (sCCS). Low silicic acid: nitrate ratios (Si:N) and high nitrate to iron ratios (N: Fe) characteristic of Fe-limiting conditions in the sCCS were associated with the northern cyclone and with the transition zone between the cyclones and the anticyclone. Phytoplankton growth in low-Si:N, high-N:Fe waters responded strongly to added Fe, confirming growth limitation by Fe of the diatom-dominated phytoplankton community. Low Si: N waters had low biogenic silica content, intermediate productivity, but high export compared to intermediate Si: N waters indicating increased export efficiency under Fe stress. Biogenic silica and particulate organic carbon (POC) export were both high beneath low Si: N waters with biogenic silica export being especially enhanced. This suggests that relatively high POC export from low Si: N waters was supported by silica ballasting from Fe-limited diatoms. Higher POC export efficiency in low Si: N waters may have been further enhanced by lower rates of organic carbon remineralization due to reduced grazing of more heavily armored diatoms growing under Fe stress. The results imply that Fe stress can enhance carbon export, despite lowering productivity, by driving higher export efficiency.

Bograd, SJ, Buil MP, Di Lorenzo E, Castro CG, Schroeder ID, Goericke R, Anderson CR, Benitez-Nelson C, Whitney FA.  2015.  Changes in source waters to the Southern California Bight. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 112:42-52.   10.1016/j.dsr2.2014.04.009   AbstractWebsite

Historical hydrographic data (1984-2012) from the California Cooperative Oceanic Fisheries Investigations (CalCOFI) program and global reanalysis products were used to quantify recent water mass variability off the coast of Southern California. Dissolved oxygen concentrations continued to decline within the lower pycnocline, concurrent with strong increases in nitrate and phosphate that have spatial patterns matching those of dissolved oxygen. Silicic acid also shows an increasing trend in the offshore portion of the region, but has strong and opposing trends in the upper (increasing) and lower-pycnocline (decreasing) within the Southern California Bight. The varying rates of change in the inorganic nutrients yield a more complex pattern of variability in the nutrient ratios, resulting in large decreases in the N:P and Si:N ratios within the Southern California Bight at depths that provide source waters for upwelling. Basin-scale reanalysis products are consistent with low-frequency water mass changes observed off Southern California and suggest that advection of modified source waters is the cause of the variability. The biogeochemical changes described here may have important impacts on the regional ecosystem, including a reduction of viable pelagic habitat and community reorganization. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (

Sydeman, WJ, Thompson SA, Santora JA, Koslow JA, Goericke R, Ohman MD.  2015.  Climate-ecosystem change off southern California: Time-dependent seabird predator-prey numerical responses. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 112:158-170.   10.1016/j.dsr2.2014.03.008   AbstractWebsite

Climate change may increase both stratification and upwelling in marine ecosystems, but these processes may affect productivity in opposing or complementary ways. For the Southern California region of the California Current Ecosystem (CCE), we hypothesized that changes in stratification and upwelling have affected marine bird populations indirectly through changes in prey availability. To test this hypothesis, we derived trends and associations between stratification and upwelling, the relative abundance of potential prey including krill and forage fish, and seabirds based on the long-term, multi-disciplinary CalCOFI/CCE-LTER program. Over the period 1987 through 2011, spring and summer seabird density (all species combined) declined by similar to 2% per year, mostly in the northern sector of the study region. Krill showed variable trends with two species increasing and one deceasing, resulting in community reorganization. Nearshore forage fish, dominated by northern anchovy (Engraulis mordax) as well as offshore mesopelagic species, show declines in relative abundance over this period. The unidirectional decline in springtime seabird density is largely explained by declining nearshore fish abundance in the previous season (winter). Interannual variability in seabird density, especially in the 2000s, is explained by variability in krill abundance. Changes in the numerical responses of seabirds to prey abundance correspond to a putative ecosystem shift in 1998-1999 and support aspects of optimal foraging (diet) theory. Predator-prey interactions and numerical responses clearly explain aspects of the upper trophic level patterns of change in the pelagic ecosystem off southern California. (C) 2014 Elsevier Ltd. All rights reserved.

Goericke, R, Bograd SJ, Grundle DS.  2015.  Denitrification and flushing of the Santa Barbara Basin bottom waters. Deep-Sea Research Part Ii-Topical Studies in Oceanography. 112:53-60.   10.1016/j.dsr2.2014.07.012   AbstractWebsite

The sediments of the Santa Barbara Basin (SBB) are an important paleoecological resource since their structure reflects the oxygenation of the bottom waters and the quality and quantity of the particulate matter which is sequestered to the bottom of the basin. These properties are controlled by regional atmospheric and oceanic climate. The California Cooperative Oceanic Fisheries Investigations (CalCOFI) program has been monitoring the bottom waters of the SBB on a regular basis since 1986. Over the last decade, properties of SBB bottom waters have undergone dramatic changes: low concentrations of nitrate were observed more frequently and concentrations of nitrite, at times, reached values of 7 mu M, in contrast to maximum concentrations of 0.2 mu M observed during the earlier time period. Here we study the links between regional climate and conditions at the bottom of the SBB by relating recent changes in bottom water chemistry to local and regional forcing of the basin. Varying rates of primary production of the overlying water or rates of export production were not significantly related to the observed biogeochemical changes in the basin. Rather, the frequency or rate of flushing, as inferred from phosphate concentration changes at the bottom of the basin, and decreasing concentrations of oxygen in the waters outside the basins could be related to the observed changes. The episodic more than 10-fold increases of nitrite in the bottom waters likely represent a tipping point in the biogeochemical system driven by decreasing concentrations of oxygen in the bottom waters. (C) 2014 Elsevier Ltd. All rights reserved.

Leising, AW, Schroeder ID, Bograd SJ, Abell J, Durazo R, Gaxiola-Castro G, Bjorkstedt EP, Field J, Sakuma K, Robertson RR, Goericke R, Peterson WT, Brodeur R, Barcelo C, Auth TD, Daly EA, Suryan RM, Gladics AJ, Porquez JM, McClatchie S, Weber ED, Watson W, Santora JA, Sydeman WJ, Melin SR, Chavez FP, Golightly RT, Schneider SR, Fisher J, Morgan C, Bradley R, Warybok P.  2015.  State of the California Current 2014-15: Impacts of the warm-water "blob". California Cooperative Oceanic Fisheries Investigations Reports. 56:31-68. AbstractWebsite

In 2014, the California Current (similar to 28 degrees-48 degrees N) saw average, or below average, coastal upwelling and relatively low productivity in most locations, except from 38 degrees-43 degrees N during June and July. Chlorophyll-a levels were low throughout spring and summer at most locations, except in a small region around 39 degrees N. Catches of juvenile rockfish (an indicator of upwelling-related fish species) remained high throughout the area surveyed (32 degrees-43 degrees N). In the fall of 2014, as upwelling ceased, many locations saw an unprecedented increase in sea surface temperatures (anomalies as large as 4 degrees C), particularly at 45 degrees N due to the coastal intrusion of an extremely anomalous pool of warm water. This warm surface anomaly had been building offshore in the Gulf of Alaska since the fall of 2013, and has been referred to as the "blob." Values of the Pacific Decadal Oscillation index (PDO) continued to climb during 2014, indicative of the increase in warm coastal surface waters, whereas the North Pacific Gyre Oscillation index (NPGO) saw a slight rebound to more neutral values (indicative of average productivity levels) during 2014. During spring 2015, the upwelling index was slightly higher than average for locations in the central and northern region, but remained below average at latitudes south of 35 degrees N. Chlorophyll a levels were slightly higher than average in similar to 0.5 degrees latitude patches north of 35 degrees N, whereas productivity and phytoplankton biomass were low south of Pt. Conception. Catches of rockfish remained high along most of the coast, however, market squid remained high only within the central coast (36 degrees-38 degrees N), and euphausiid abundance decreased everywhere, as compared to the previous year. Sardine and anchovy were nearly absent from the southern portion of the California Current system (CCS), whereas their larvae were found off the coast of Oregon and Washington during winter for the first time in many years. Waters warmed dramatically in the southern California region due to a change in wind patterns similar to that giving rise to the blob in the broader northeast Pacific. For most of the coast, there were intrusions of species never found before or found at much higher abundances than usual, including fish, crustaceans, tunicates and other gelatinous zooplankton, along with other species often indicative of an El Nino. Thus species richness was high in many areas given the close juxtaposition of coastal upwelling-related species with the offshore warm-water intrusive or El Nino-typical taxa. Thus the California Current by 2015 appears to have transitioned to a very different state than previous observations.

McClatchie, S, Duffy-Anderson J, Field JC, Goericke R, Griffith D, Hanisko DS, Hare JA, Lyczkowski-Shultz J, Peterson WT, Watson W, Weber ED, Zapfe G.  2014.  Long time series in U.S. fisheries oceanography. Oceanography. 27:48-67.   10.5670/oceanog.2014.86   AbstractWebsite

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.

Wang, SY, Lambert W, Giang S, Goericke R, Palenik B.  2014.  Microalgal assemblages in a poikilohaline pond. Journal of Phycology. 50:303-309.   10.1111/jpy.12158   AbstractWebsite

Microalgal strains for algal biofuels production in outdoor ponds will need to have high net growth rates under diverse environmental conditions. A small, variable salinity pond in the San Elijo Lagoon estuary in southern California was chosen to serve as a model pond due to its routinely high chlorophyll content. Profiles of microalgal assemblages from water samples collected from April 2011 to January 2012 were obtained by constructing 18S rDNA environmental clone libraries. Pond assemblages were found to be dominated by green algae Picochlorum sp. and Picocystis sp. throughout the year. Pigment analysis suggested that the two species contributed most of the chlorophyll a of the pond, which ranged from 21.9 to 664.3 mu g center dot L-1 with the Picocystis contribution increasing at higher salinities. However, changes of temperature, salinity or irradiance may have enabled a bloom of the diatom Chaetoceros sp. in June 2011. Isolates of these microalgae were obtained and their growth rates characterized as a function of temperature and salinity. Chaetoceros sp. had the highest growth rate over the temperature test range while it showed the most sensitivity to high salinity. All three strains showed the presence of lipid bodies during nitrogen starvation, suggesting they have potential as future biofuels strains.

Ohman, MD, Barbeau K, Franks PJS, Goericke R, Landry MR, Miller AJ.  2013.  Ecological transitions in a coastal upwelling ecosystem. Oceanography. 26:210-219. AbstractWebsite

The southern California Current Ecosystem (CCE) is a dynamic eastern boundary current ecosystem that is forced by ocean-atmosphere variability on interannual, multidecadal, and long-term secular time scales. Recent evidence suggests that apparent abrupt transitions in ecosystem conditions reflect linear tracking of the physical environment rather than oscillations between alternative preferred states. A space-for-time exchange is one approach that permits use of natural spatial variability in the CCE to develop a mechanistic understanding needed to project future temporal changes. The role of (sub)mesoscale frontal systems in altering rates of nutrient transport, primary and secondary production, export fluxes, and the rates of encounters between predators and prey is an issue central to this pelagic ecosystem and its future trajectory because the occurrence of such frontal features is increasing.

Munro, DR, Quay PD, Juranek LW, Goericke R.  2013.  Biological production rates off the Southern California coast estimated from triple O-2 isotopes and O-2 : Ar gas ratios. Limnology and Oceanography. 58:1312-1328.   10.4319/lo.2013.58.4.1312   AbstractWebsite

The isotopic composition of dissolved O-2 ((17)Delta) and the biological O-2 saturation from O-2 : Ar ratios were measured in the surface ocean during six cruises off the coast of southern California from November 2005 to August 2008 to determine rates of gross oxygen production (GOP), net oxygen production (NOP), and the NOP:GOP ratio (a measure of potential export efficiency). In the mixed layer, (17)Delta of dissolved O-2 (17 Delta(diss)) ranged from 24 to 108 per meg and biological O-2 saturation ranged from 101% to 113% for all regions and cruises. Mixed-layer (17)Delta-GOP ranged from 49 +/- 23 mmol O-2 m(-2) d(-1) to 533 +/- 185 mmol O-2 m(-2) d(-1) with an annual mean for the California Cooperative Oceanic Fisheries Investigations (CalCOFI) grid of 151 +/- 59 mmol O-2 m(-2) d(-1). Mixed-layer O-2 : Ar-NOP ranged from 8 +/- 6 mmol O-2 m(-2) d(-1) to 135 +/- 31 mmol O-2 m(-2)d(-1) with an annual mean of 25 +/- 8 mmol O-2 m(-2) d(-1), implying that the CalCOFI grid is autotrophic year-round. (17)Delta-GOP estimates were consistently greater than on-deck incubation-based C-14-primary production (C-14-PP) by a factor of 5.6 +/- 6 0.4 and greater than satellite PP estimates by a factor of 3.5 +/- 0.3 (mmol O-2 : mmol C). The (17)Delta-GOP to C-14-PP factor was twice the expected factor of 2.7 determined from comparisons of incubation-based O-18-GOP and C-14-PP. The annual mean NOP: GOP ratio was 0.16 +/- 0.06, suggesting a potential export efficiency that is surprisingly similar to the open ocean using comparable methods.

Wells, BK, Schroeder ID, Santora JA, Hazen EL, Bograd SJ, Bjorkstedt EP, Loeb VJ, McClatchie S, Weber ED, Watson W, Thompson AR, Peterson WT, Brodeur RD, Harding J, Field J, Sakuma K, Hayes S, Mantua N, Sydeman WJ, Losekoot M, Thompson SA, Largier J, Kim SY, Chavez FP, Barcelo C, Warzybok P, Bradley R, Jahncke J, Goericke R, Campbell GS, Hildebrand JA, Melin SR, DeLong RL, Gomez-Valdes J, Lavaniegos B, Gaxiola-Castro G, Golightly RT, Schneider SR, Lo N, Suryan RM, Gladics AJ, Horton CA, Fisher J, Morgan C, Peterson J, Daly EA, Auth TD, Abell J.  2013.  State of the California current 2012-13: No such thing as an "average" year. California Cooperative Oceanic Fisheries Investigations Reports. 54:37-71. AbstractWebsite

This report reviews the state of the California Current System (CCS) between winter 2012 and spring 2013, and includes observations from Washington State to Baja California. During 2012, large-scale climate modes indicated the CCS remained in a cool, productive phase present since 2007. The upwelling season was delayed north of 42 degrees N, but regions to the south, especially 33 degrees to 36 degrees N, experienced average to above average upwelling that persisted throughout the summer. Contrary to the indication of high production suggested by the climate indices, chlorophyll observed from surveys and remote sensing was below average along much of the coast. As well, some members of the forage assemblages along the coast experienced low abundances in 2012 surveys. Specifically, the concentrations of all life-stages observed directly or from egg densities of Pacific sardine, Sardinops sagax, and northern anchovy, Engraulis mordax, were less than previous years' survey estimates. However, 2013 surveys and observations indicate an increase in abundance of northern anchovy. During winter 2011/2012, the increased presence of northern copepod species off northern California was consistent with stronger southward transport. Krill and small-fraction zooplankton abundances, where examined, were generally above average. North of 42 degrees N, salps returned to typical abundances in 2012 after greater observed concentrations in 2010 and 2011. In contrast, salp abundance off central and southern California increased after a period of southward transport during winter 2011/2012. Reproductive success of piscivorous Brandt's cormorant, Phalacrocorax penicillatus, was reduced while planktivorous Cassin's auklet, Ptychoramphus aleuticus was elevated. Differences between the productivity of these two seabirds may be related to the available forage assemblage observed in the surveys. California sea lion pups from San Miguel Island were undernourished resulting in a pup mortality event perhaps in response to changes in forage availability. Limited biological data were available for spring 2013, but strong winter upwelling coastwide indicated an early spring transition, with the strong upwelling persisting into early summer.

Anthony Koslow, J, Goericke R, Watson W.  2013.  Fish assemblages in the Southern California Current: relationships with climate, 1951–2008. Fisheries Oceanography. 22:207-219.   10.1111/fog.12018   AbstractWebsite

We examined the dominant patterns of variability in the fish fauna of the southern California Current based on a principal component (PC) analysis of the California Cooperative Oceanic Fisheries Investigations ichthyoplankton data set, 1951–2008. Eighty-six taxa were analyzed, including all ecologically dominant fish species, both exploited and unexploited. The first three PCs accounted for 20.5, 12.4 and 6.8% of the variance of the data, respectively (total: 39.7%). Each was dominated by taxa from particular adult or larval habitats. PC 1 predominantly represented the coherent response of 24 mesopelagic taxa from 10 families and was most highly correlated with long-term trends in midwater oxygen levels. PC 2 was dominated by six of the seven most abundant ichthyoplankton taxa in the region, predominantly California Current endemics including key pelagic species (northern anchovy, Pacific sardine and Pacific hake), rockfishes (genus Sebastes) and two midwater taxa. It was correlated primarily with sea surface temperature and exhibited a significant declining trend. PC 3 was dominated by coastal and reef-associated fishes with predominantly southerly affinities. It was positively correlated with sea surface temperature and sea level height, a proxy for diminished flow of the California Current. The taxa dominating PCs 2 and 3 mostly spatially co-occur as ichthyoplankton. These results suggest that fish assemblages in the California Current are predominantly influenced by environmental forcing of their ocean habitats as adults or larvae, or both.

Chekalyuk, AM, Landry MR, Goericke R, Taylor AG, Hafez MA.  2012.  Laser fluorescence analysis of phytoplankton across a frontal zone in the California Current ecosystem. Journal of Plankton Research. 34:761-777.   10.1093/plankt/fbs034   AbstractWebsite

Spatial variability of chlorophyll, phycobiliproteins, chromophoric dissolved organic matter and variable fluorescence (F-v/F-m) was analyzed across a deep-water density front in the Southern California Current Ecosystem using an Advanced Laser Fluorometer (ALF) calibrated to assess chlorophyll concentration (C-chl), total autotrophic carbon (AC) and Synechococcus carbon biomass (SYN). Three distinct autotrophic assemblages were identified. Fluorescence was found to be three to four times higher in cooler mesotrophic waters north of the front than in warm oligotrophic waters to the south. Northern waters were distinguished by a shallow pigment maximum dominated by a blue-water type of Synechococcus and by the presence of green-water Synechococcus and cryptophytes; only blue-water Synechococcus were detected at lower concentration south of the front. The highest C-chl and AC values, accompanied by elevated F-v/F-m and chlorophyll fluorescence per unit of C-chl, and minimal Synechococcus abundance, were found directly at the front in a 2040 m deep layer dominated by diatoms. The covariation of F-v/F-m with nitrate concentration in this layer, along with the structural changes in the phytoplankton community, suggest that it had been generated by in situ processes rather than advection. Strong structural responses to the local hydrography were also revealed by high-frequency underway ALF surface sampling, which detected an abrupt transition from low to high SYN on the northern side of a sharp salinity gradient at the front. Synechococcus-specific phycoerythrin fluorescence (F-PE12) and SYN were highly correlated in surface waters (R-2 0.95), while F-PE12:SYN gradually increased with depth. Strong relationships were found for chlorophyll fluorescence versus C-chl (R-2 0.95) and AC (R-2 0.79).

Samo, TJ, Pedler BE, Ball GI, Pasulka AL, Taylor AG, Aluwihare LI, Azam F, Goericke R, Landry MR.  2012.  Microbial distribution and activity across a water mass frontal zone in the California Current Ecosystem. Journal of Plankton Research. 34:802-814.   10.1093/plankt/fbs048   AbstractWebsite

Ocean fronts with accumulated biomass and organic matter may be significant sites of enhanced microbial activity. We sampled a frontal region (the A-Front) separating oligotrophic and mesotrophic water masses within the California Current Ecosystem (CCE) to assess the influence of frontal hydrography on several microbial parameters. Samples for heterotrophic bacterial, viral and flagellate abundance, dissolved and particulate carbon and nitrogen, transparent particles and bacterial carbon production were collected at 6 depths from the surface to 100 m with 59 conductivity/temperature/depth casts along a 26-km northerly transect across the front. Relative to adjacent oligotrophic and mesotrophic waters, the frontal transition displayed peaks in the mean estimates of cell-specific bacterial carbon and bulk bacterial production, particulate organic carbon and particulate organic nitrogen concentrations, and the abundance and size of transparent particles. Bacterial carbon production increased approximate to 5-fold northward from oligotrophic waters to the frontal zone, in agreement with an increase in the frequency of dividing cells, but bacterial abundance was lower than at adjacent stations. This may be partially explained by high chlorophyll, elevated virus:bacteria ratios and low nanoflagellate grazer abundance at the front. Our data suggest that CCE fronts can facilitate intense biological transformation and physical transport of organic matter, in sharp contrast to adjacent low productivity waters, and harbor dynamic microbial populations that influence nutrient cycling.

Landry, MR, Ohman MD, Goericke R, Stukel MR, Barbeau KA, Bundy R, Kahru M.  2012.  Pelagic community responses to a deep-water front in the California Current Ecosystem: overview of the A-Front Study. Journal of Plankton Research. 34:739-748.   10.1093/plankt/fbs025   AbstractWebsite

In October 2008, we investigated pelagic community composition and biomass, from bacteria to fish, across a sharp frontal gradient overlying deep waters south of Point Conception, California. This northsouth gradient, which we called A-Front, was formed by the eastward flow of the California Current and separated cooler mesotrophic waters of coastal upwelling origin to the north, from warm oligotrophic waters of likely mixed subarcticsubtropical origin to the south. Plankton biomass and phytoplankton growth rates were two to three times greater on the northern side, and primary production rates were elevated 5-fold to the north. Compared with either of the adjacent waters, the frontal interface was strongly enriched and uniquely defined by a subsurface bloom of large diatoms, elevated concentrations of suspension-feeding zooplankton, high bioacoustical estimates of pelagic fish and enhanced bacterial production and phytoplankton biomass and photosynthetic potential. Such habitats, though small in areal extent, may contribute disproportionately and importantly to regional productivity, nutrient cycling, carbon fluxes and trophic ecology. As a general introduction to the A-Front study, we provide an overview of its design and implementation, a brief summary of major findings and a discussion of potential mechanisms of plankton enrichment at the front.

Taylor, AG, Goericke R, Landry MR, Selph KE, Wick DA, Roadman MJ.  2012.  Sharp gradients in phytoplankton community structure across a frontal zone in the California Current Ecosystem. Journal of Plankton Research. 34:778-789.   10.1093/plankt/fbs036   AbstractWebsite

Spatial variability of plankton biomass, community composition and size structure was investigated across a strong frontal transition (A-Front) in the southern California Current Ecosystem in October 2008. Depth profiles were taken across a 25-km transect of nine stations sampled semi-synoptically during one night and for 3 days following drifter arrays in the adjacent water masses. Community compositions are compared based on analyses by digital epifluorescence microscopy, flow cytometry and pigment composition by high-pressure liquid chromatography. Our results show three assemblages sharply delineated in space, with plankton at the front being compositionally distinct and biomass elevated relative to either of the adjacent water masses. Depth-averaged chlorophyll a (Chl a) varied by a factor of 2.3 (0.350.81 g Chl a L-1) and autotrophic carbon (AC) varied almost 3-fold (13.635.4 g C L-1) across the front. One of the most striking features was a sharp gradient in the distribution of Prochlorococcus (PRO) and Synechococcus (SYN), with PRO located in the warmer oligotrophic waters on the south side of the front and SYN located in the cooler mesotrophic waters to the north. Both PRO and SYN had local biomass minima directly at the front. The peak in phytoplankton biomass at the front was dominated by large (20 m) diatom cells, comprising 71 of the total community biomass. In contrast to previous studies of frontal features in the southern California Current, our study of the A-Front shows strong frontal enhancement of phytoplankton biomass and a shift of phytoplankton size structure towards larger cells.