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Dorman J.G.,University of California at Berkeley | Powell T.M.,University of California at Berkeley | Sydeman W.J.,Farallon Institute for Advanced Ecosystem Research | Bograd S.J.,Southwest Fisheries Science Center
Geophysical Research Letters

A decrease in krill abundance during 2005 in regions of the California Current has been hypothesized to have had immediate (seabird) and long-term (salmon) negative impacts on upper trophic level predators. We use a suite of coupled models to examine the population biology and spatial and temporal distribution of the krill species Euphausia pacifica during the winter/spring of 2001, a "normal" year, and 2005, an "anomalous" year, to determine if this hypothesis is supported mechanistically. Ocean conditions were simulated using the Regional Ocean Modeling System (ROMS), which forced an individual-based model parameterized to simulate the population biology of E. pacifica. Poleward transport during winter 2005 advected particles north of Cape Mendocino, away from seabirds and salmon feeding in the Gulf of the Farallons region. Few of the particles that were advected north in 2005 returned to their region of release throughout the model run time (200 days). Moreover, the "condition" of those particles remaining within the domain was poor in 2005, with greater mortality from starvation and a decreased mean particle weight. Our results indicate that both physical processes (anomalous northern advection) and biological processes (greater starvation and less weight per individual) contributed to reduced krill availability to predators in the northern California region during 2005, and that the productivity and survival of seabirds and salmonids is dependent on krill during critical life history stages. Copyright © 2011 by the American Geophysical Union. Source

Loeb V.J.,Moss Landing Marine Laboratories | Santora J.A.,Farallon Institute for Advanced Ecosystem Research | Santora J.A.,University of California at Santa Cruz
Progress in Oceanography

Shelled (thecosome) and naked (gymnosome) pteropods are regular, at times abundant, members of Southern Ocean zooplankton assemblages. Regionally, shelled species can play a major role in food webs and carbon cycling. Because of their aragonite shells thecosome pteropods may be vulnerable to the impacts of ocean acidification; without shells they cannot survive and their demise would have major implications for food webs and carbon cycling in the Southern Ocean. Additionally, pteropod species in the southwest Atlantic sector of the Southern Ocean inhabit a region of rapid warming and climate change, the impacts of which are predicted to be observed as poleward distribution shifts. Here we provide baseline information on intraseasonal, interannual and longer scale variability of pteropod populations off the Antarctic Peninsula between 1994 and 2009. Concentrations of the 4 dominant taxa, Limacina helicina antarctica f. antarctica, Clio pyramidata f. sulcata, Spongiobranchaea australis and Clione limacina antarctica, are similar to those monitored during the 1928-1935 Discovery Investigations and reflect generally low values but with episodic interannual abundance peaks that, except for C. pyr. sulcata, are related to basin-scale climate forcing associated with the El Niño-Southern Oscillation (ENSO) climate mode. Significant abundance increases of L. helicina and S. australis after 1998 were associated with a climate regime shift that initiated a period dominated by cool La Niña conditions and increased nearshore influence of the Antarctic Circumpolar Current (ACC). This background information is essential to assess potential future changes in pteropod species distribution and abundance associated with ocean warming and acidification. © 2013 Elsevier Ltd. Source

Surman C.A.,Halfmoon Biosciences | Nicholson L.W.,Halfmoon Biosciences | Santora J.A.,Farallon Institute for Advanced Ecosystem Research
Marine Ecology Progress Series

We compared 20 yr of seabird breeding data with oceanographic variables (sea level, sea-surface temperature) and a climate index (Southern Oscillation Index; SOI) for the lesser noddy Anous tenuirostris, brown noddy A. stolidus, sooty tern Onychoprion fuscata and wedgetailed shearwater Ardenna pacifica at the Houtman Abrolhos, eastern Indian Ocean. We found that timing of breeding and performance of these species is related to climate variability, mediated by oceanographic conditions within the eastern boundary Leeuwin Current (LC). The 3 migratory species have breeding parameters which are correlated with sea level and the SOI, while the first egg date of the resident lesser noddy is correlated with SST during their pre-breeding phase. There was poor breeding performance for each species during El Niño Southern Oscillation (ENSO) conditions; moreover, poor breeding success was recorded for all species outside of (ENSO events in the latter years of the study. In addition, breeding was delayed for all species during the time of the present study. The environmental conditions contributing to this appear to be fewer years of strong LC flow with associated high sea levels, warmer SSTs, stronger eddy energy and increased productivity. Migratory seabird species breeding at this location appear less able to respond to climate variability-and its influence upon prey availability-than the resident species. It is suggested that the resident lesser noddy may have an advantage due to its response to a localised environmental cue, SST, in the pre-breeding phase, which may be correlated with prey availability in the waters surrounding the Houtman Abrolhos. © Inter-Research 2012. Source

Loeb V.J.,Moss Landing Marine Laboratories | Santora J.A.,Farallon Institute for Advanced Ecosystem Research
Progress in Oceanography

The salp Salpa thompsoni has exhibited increased abundance in high latitude portions of the Southern Ocean in recent decades and is now frequently the numerically dominant zooplankton taxon in the Antarctic Peninsula region. The abundance increase of this species in high latitude waters is believed related to ocean warming. Due to its continuous filter feeding and production of dense rapidly sinking fecal pellets S. thompsoni is considered to be an important link in the export of particulate carbon from the surface waters. Hence basic information on the life history of this component of the Antarctic marine ecosystem is essential for assessing its impact given continued climate warming. Here we cover various aspects of the life history of S. thompsoni collected in the north Antarctic Peninsula during annual austral summer surveys of the US Antarctic Marine Living Resources (AMLR) Program between 1993 and 2009. We focus on seasonal and interannual variations in the size composition and abundance of the aggregate (sexual) and solitary (asexual) stages. This information is valuable for refining components of Southern Ocean food web models that explicitly deal with size-structured and life history information on zooplankton. Intraseasonal changes in length-frequency distribution of both stages are used to estimate their growth rates. These average 0.40mmday -1 for aggregates and 0.23mmday -1 for solitaries; together these represent ~7week and ~7.5month generation times, respectively, and a 9month life cycle (i.e., onset of aggregate production year 1 to aggregate production year 2). Based on the maximum lengths typically found during January-March, the life spans of the aggregate and solitary stages can reach at least ~5 and ~15months, respectively. Length-frequency distributions each year reflect interannual differences in timing of the initiation and peak reproductive output. Interannual differences in the abundance of total salps and proportions of the overwintering solitary stage are significantly correlated with El Niño Southern Oscillation indices (SOI and Nino3.4) prevailing over the previous 2years. Massive salp blooms result from two successive summers of elevated solitary production following a reversal from La Niña to El Niño conditions. These results indicate the role of basin-scale atmospheric-oceanic processes in establishing optimal conditions that support aggregate and solitary stage reproduction, development and growth. © 2011 Elsevier Ltd. Source

Agency: NSF | Branch: Standard Grant | Program: | Phase: BIOLOGICAL OCEANOGRAPHY | Award Amount: 110.86K | Year: 2016

This research has the potential to transform our understanding of how climate affects marine ecosystems and improve efforts toward ecosystem-based fisheries management. Investigators will analyze existing data to determine how shifts in climate properties over time may have affected commercially important fishes in the Gulf of Alaska (GOA). For several decades, significant relationships between sea surface temperature (SST) and abundance of a broad group of marine organisms in the GOA offered some promise for incorporating environmental data into fisheries management strategies. However, many of these statistical connections deteriorated abruptly in the late 1980s, while at the same time interactions between GOA SST and other aspects of climate conditions changed as well. This study will test the hypothesis that a switch in large-scale climate variability in the 1980s led to reorganization of relationships among GOA atmospheric and oceanographic properties, which in turn, produced a change in connection between temperature and ocean biology. These types of no-analogue climate states are well recognized in paleoecology and have been anticipated as a potential outcome of climate change, but few studies of ecological response to such switches are available. The project will support a postdoctoral scientist, as well as graduate and undergraduate student researchers. It will facilitate cooperation among scientists at three public universities, a non-profit research lab, and a federal management agency in order to combine the range of expertise that will be required to carry out this research.

This research has the potential to transform our understanding of how climate affects marine ecosystems. It is based on preliminary analyses showing that the statistical relationships between SST and community state in the Gulf of Alaska appear to be nonstationary, with driver-response relationships that differ markedly before and after 1988/89. Preliminary analyses also show that correlations between SST and a number of other GOA climate parameters are significantly different before and after 1988/89. Additionally, leading modes in North Pacific SST anomalies for 1950-present changed their relative importance before and after 1988/89, with the second mode (North Pacific Gyre Oscillation, or NPGO) explaining more variability than the first mode (Pacific Decadal Oscillation, or PDO) during the past three decades. This change is consistent with a switch to a no-analogue climate state, characterized by markedly different patterns of variability among basin-scale climate processes. The proposed hypothesis will be tested with a combination of statistical ecological models and numerical ocean models. The statistical approach (threshold generalized additive models) will provide formal tests for nonstationary relationships between SST variability and ecological characteristics at the community and population level using time series data (1965-present) for 17 salmon, groundfish and crustacean populations from the GOA. In addition, nonstationary relationships among atmospheric and hydrographic processes at basin and regional scales will be tested with time series generated by ocean data-assimilation and hindcast models. Finally, those nonstationary relationships identified will be used to parameterize statistical models of biological variability that account for non-analogous states in the system.

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