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Ainley D.,983 University Avenue | Russell J.,University of Arizona | Jenouvrier S.,Woods Hole Oceanographic Institution | Woehler E.,University of Tasmania | And 3 more authors.
Ecological Monographs | Year: 2010

We assess the response of pack ice penguins, Emperor (Aptenodytes forsteri) and Adélie (Pygoscelis adeliae), to habitat variability and, then, by modeling habitat alterations, the qualitative changes to their populations, size and distribution, as Earth's average tropospheric temperature reaches 2°C above preindustrial levels (ca. 1860), the benchmark set by the European Union in efforts to reduce greenhouse gases. First, we assessed models used in the Intergovernmental Panel on Climate Change Fourth Assessment Report (AR4) on penguin performance duplicating existing conditions in the Southern Ocean. We chose four models appropriate for gauging changes to penguin habitat: GFDL-CM2.1, GFDL-CM2.0, MIROC3.2(hi-res), and MRI-CGCM2.3.2a. Second, we analyzed the composited model ENSEMBLE to estimate the point of 2°C warming (2025-2052) and the projected changes to sea ice coverage (extent, persistence, and concentration), sea ice thickness, wind speeds, precipitation, and air temperatures. Third, we considered studies of ancient colonies and sediment cores and some recent modeling, which indicate the (space/time) large/centennialscale penguin response to habitat limits of all ice or no ice. Then we considered results of statistical modeling at the temporal interannual-decadal scale in regard to penguin response over a continuum of rather complex, meso- to large-scale habitat conditions, some of which have opposing and others interacting effects. The ENSEMBLE meso/decadal-scale output projects a marked narrowing of penguins' Zoogeographic range at the 2°C point. Colonies north of 70° S are projected to decrease or disappear: ∼50% of Emperor colonies (40% of breeding population) and ∼75% of Adélie colonies (70% of breeding population), but limited growth might occur south of 73° S. Net change would result largely from positive responses to increase in polynya persistence at high latitudes, overcome by decreases in pack ice cover at lower latitudes and, particularly for Emperors, ice thickness. Adélie Penguins might colonize new breeding habitat where concentrated pack ice diverges and/or disintegrating ice shelves expose coastline. Limiting increase will be decreased persistence of pack ice north of the Antarctic Circle, as this species requires daylight in its wintering areas. Adélies would be affected negatively by increasing snowfall, predicted to increase in certain areas owing to intrusions of warm, moist marine air due to changes in the Polar Jet Stream. © 2010 by the Ecological Society of America.

Ruzicka J.J.,Oregon State University | Steele J.H.,Woods Hole Oceanographic Institution | Ballerini T.,Aix - Marseille University | Gaichas S.K.,National Oceanic and Atmospheric Administration | Ainley D.G.,983 University Avenue
Progress in Oceanography | Year: 2013

Similarly structured food web models of four coastal ecosystems (Northern California Current, Central Gulf of Alaska, Georges Bank, southwestern Antarctic Peninsula) were used to investigate competition among whales, fishes, pinnipeds, and humans. Two analysis strategies simulated the effects of historic baleen and odontocete whale abundances across all trophic levels: food web structure scenarios and time-dynamic scenarios. Direct competition between whales and commercial fisheries is small at current whale abundances; whales and fisheries each take similar proportions of annual pelagic fish production (4-7%). Scenarios show that as whale populations grow, indirect competition between whales and fish for zooplankton would more likely impact fishery production than would direct competition for fish between whales and commercial fisheries. Increased baleen whale abundance would have greater and broader indirect effects on upper trophic levels and fisheries than a similar increase in odontocete abundance. Time-dynamic scenarios, which allow for the evolution of compensatory mechanisms, showed more modest impacts than structural scenarios, which show the immediate impacts of altered energy pathways.Structural scenarios show that in terms of energy availability, there is potential for large increases in whale abundance without major changes to existing food web structures and without substantial reduction of fishery production. For each ecosystem, a five-fold increase in baleen whale abundance could be supported with minor disruptions to existing energy flow pathways. However, such an increase would remain below historical population levels for many cetaceans. A larger expansion (20X) could be accommodated only with large reductions in energy flow to competitor groups. The scope for odontocete expansion varies between ecosystems but may be more restricted than the scope for baleen expansion because they feed at higher, less productive trophic levels. © 2013 Elsevier Ltd.

Carter H.R.,Carter Biological Consulting | Ainley D.G.,983 University Avenue | Wolf S.G.,Center for Biological Diversity | Weinstein A.M.,California Audubon
Marine Ornithology | Year: 2016

In February 2015, a special paper session about the range-wide conservation and science of the Ashy Storm-Petrel Oceanodroma homochroa (ASSP) was held at the Pacific Seabird Group annual meeting. The main goal was to share information amassed during the past 20 years on this species, which breeds almost entirely in California, United States, for formulating future research and conservation actions. One key result is the six papers on ASSP and two on Leach’s Storm-Petrels O. leucorhoa in this issue of Marine Ornithology. In this introduction, we augment contributed papers with a summary of historic and recent knowledge about the ASSP breeding range, key conservation issues and data gaps. The largest breeding concentration is at the South Farallon Islands in central California, but four other concentrations occur in southern California at the Channel Islands (Prince, Santa Barbara-Sutil, northwest Santa Cruz and northeast Santa Cruz). Over the past two centuries, many ASSP breeding colonies have been affected by introduced mammals and human-altered breeding habitats. Population decline due to heavy avian predation has been documented at the South Farallon Islands since 1972; decline due to eggshell thinning from organochlorine pollutants is suspected in the Channel Islands since the 1950s. Eradication of introduced mammals, reduction of pollution and social attraction (vocalization broadcasting and artificial nest sites) have helped to restore population size at certain colonies. © 2016, Marine Ornithology. All rights reserved.

Ribic C.A.,U.S. Geological Survey | Ainley D.G.,983 University Avenue | Glenn Ford R.,University of California at Santa Cruz | Fraser W.R.,Polar Oceans Research Group | And 2 more authors.
Deep-Sea Research Part II: Topical Studies in Oceanography | Year: 2011

Waters off the western Antarctic Peninsula (i.e., the eastern Bellingshausen Sea) are unusually complex owing to the convergence of several major fronts. Determining the relative influence of fronts on occurrence patterns of top-trophic species in that area, therefore, has been challenging. In one of the few ocean-wide seabird data syntheses, in this case for the Southern Ocean, we analyzed ample, previously collected cruise data, Antarctic-wide, to determine seabird species assemblages and quantitative relationships to fronts as a way to provide context to the long-term Palmer LTER and the winter Southern Ocean GLOBEC studies in the eastern Bellingshausen Sea. Fronts investigated during both winter (April-September) and summer (October-March) were the southern boundary of the Antarctic Circumpolar Current (ACC), which separates the High Antarctic from the Low Antarctic water mass, and within which are embedded the marginal ice zone and Antarctic Shelf Break Front; and the Antarctic Polar Front, which separates the Low Antarctic and the Subantarctic water masses. We used clustering to determine species' groupings with water masses, and generalized additive models to relate species' densities, biomass and diversity to distance to respective fronts. Antarctic-wide, in both periods, highest seabird densities and lowest species diversity were found in the High Antarctic water mass. In the eastern Bellingshausen, seabird density in the High Antarctic water mass was lower (as low as half that of winter) than found in other Antarctic regions. During winter, Antarctic-wide, two significant species groups were evident: one dominated by Adélie penguins (. Pygoscelis adeliae) (High Antarctic water mass) and the other by petrels and prions (no differentiation among water masses); in eastern Bellingshausen waters during winter, the one significant species group was composed of species from both Antarctic-wide groups. In summer, Antarctic-wide, a High Antarctic group dominated by Adélie penguins, a Low Antarctic group dominated by petrels, and a Subantarctic group dominated by albatross were evident. In eastern Bellingshausen waters during summer, groups were inconsistent. With regard to frontal features, Antarctic-wide in winter, distance to the ice edge was an important explanatory factor for nine of 14 species, distance to the Antarctic Polar Front for six species and distance to the Shelf Break Front for six species; however, these Antarctic-wide models could not successfully predict spatial relationships of winter seabird density (individual species or total) and biomass in the eastern Bellingshausen. Antarctic-wide in summer, distance to land/Antarctic continent was important for 10 of 18 species, not a surprising result for these summer-time Antarctic breeders, as colonies are associated with ice-free areas of coastal land. Distance to the Shelf Break Front was important for 8 and distance to the southern boundary of the ACC was important for 7 species. These summer models were more successful in predicting eastern Bellingshausen species density and species diversity but failed to predict total seabird density or biomass. Antarctic seabirds appear to respond to fronts in a way similar to that observed along the well-studied upwelling front of the California Current. To understand fully the seabird patterns found in this synthesis, multi-disciplinary at-sea investigations, including a quantified prey field, are needed. © 2011.

Ainley D.G.,983 University Avenue | Ribic C.A.,U.S. Geological Survey | Woehler E.J.,University of Tasmania
Marine Ecology Progress Series | Year: 2012

We review the history of how research directed towards marine ornithology has led to an appreciation of seabirds as highly specialized marine organisms. Beginning with R. C. Murphy (Pacific), V. C. Wynne-Edwards (Atlantic), and associates in the early 1900s, the research approach grew from an emphasis on seabird single-species ecology to an appreciation of interacting species assemblages and finally to seabirds being considered as important components of marine food webs. After a slow, drawn-out beginning, the initial main impetus for developing the field was a need to map seabird abundance and distribution tied to understanding impacts of continental shelf resource exploitation. Coalescing during the 1970s to 1980s to facilitate this line of research were 6 factors: (1) ability to identify birds at sea; (2) standardization of techniques to quantify abundance; (3) resources and techniques for mapping; (4) appreciation of how scale affects seabird relationships to hydrographic features and patchy prey; (5) development of computing power and appropriate statistics; and (6) seabird biologists becoming embedded in, as well as organizing, multidisciplinary marine research projects. Future advances in understanding the role of seabirds in marine food webs will be made by seabird biologists participating in multi - disciplinary projects using grid-like surveys relative to oceanographic features in combination with instrumentation that reveals the finer details of seabird foraging behaviors. © Inter-Research 2012.

Ainley D.G.,983 University Avenue | David Hyrenbach K.,Hawaii Pacific University
Progress in Oceanography | Year: 2010

To characterize the environmental factors affecting seabird population trends in the central portion of the California current system (CCS), we analyzed standardized vessel-based surveys collected during the late spring (May-June) upwelling season over 22 yr (1985-2006). We tested the working hypothesis that population trends are related to species-specific foraging ecology, and predicted that temporal variation in population size should be most extreme in diving species with higher energy expenditure during foraging. We related variation in individual species abundance (number km-2) to seasonally lagged (late winter, early spring, late spring) and concurrent ocean conditions, and to long-term trends (using a proxy variable: year) during a multi-decadal period of major fluctuations in the El Niño-Southern oscillation (ENSO) and the Pacific decadal oscillation (PDO). We considered both remote (Multivariate ENSO Index, PDO) and local (coastal upwelling indices and sea-surface temperature) environmental variables as proxies for ocean productivity and prey availability. We also related seabird trends to those of potentially major trophic competitors, humpback (Megaptera novaeangliae) and blue (Balaenoptera musculus) whales, which increased in number 4-5-fold midway during our study. Cyclical oscillations in seabird abundance were apparent in the black-footed albatross (Phoebastria nigripes), and decreasing trends were documented for ashy storm-petrel (Oceanodroma homochroa), pigeon guillemot (Cepphus columbus), rhinoceros auklet (Cerorhinca monocerata), Cassin's auklet (Ptychoramphus aleuticus), and western gull (Larus occidentalis); the sooty shearwater (Puffinus griseus), exhibited a marked decline before signs of recovery at the end of the study period. The abundance of nine other focal species varied with ocean conditions, but without decadal or long-term trends. Six of these species have the largest global populations in the CCS, and four are highly energetic, diving foragers. Furthermore, three of the diving species trends were negatively correlated with the abundance of humpback whales in the study area, a direct competitor for the same prey. Therefore, on the basis of literature reviewed, we hypothesize that the seabirds were affected by the decreasing carrying capacity of the CCS, over-exploitation of some prey stocks and interference competition from the previously exploited, but now increasing, baleen whale populations. Overall, our study highlights the complexity of the ecological factors driving seabird population trends in the highly variable and rapidly changing CCS ecosystem. © 2009 Elsevier Ltd. All rights reserved.

Ballard G.,PRBO Conservation Science | Ballard G.,University of Auckland | Dugger K.M.,Oregon State University | Nur N.,PRBO Conservation Science | Ainley D.G.,983 University Avenue
Marine Ecology Progress Series | Year: 2010

Animals modulate breeding effort by balancing investment in self-maintenance against investment in their young, potentially impacting reproductive success when faced with difficult conditions. This life history trade-off model has been evaluated for flying birds, especially those that forage over large pelagic regions of relatively sparse prey availability. We evaluated its applicability to penguins which, lacking flight, depend on reliably available prey relatively close to colonies. We used transponders and an automated weighing system to monitor 40 to 75 breeding Adélie penguins Pygoscelis adeliae per season for 10 seasons, while environmental conditions varied dramatically, measuring foraging trip duration, parental mass change, and total food load delivered to chicks. Parents that lost the most mass during breeding provided more food to chicks while maintaining their own condition. In contrast, in years when adult mass was lower to begin with, parents recovered their own condition and delivered less food to chicks. Food loads were also related to environmental variables, with parents making longer trips and delivering less food when access to prey was more difficult, but delivering more food to 2-chick broods than to 1-chick broods. Penguins did not alternate between short (chick provisioning) and long (self-maintenance) trips, as has been observed in farranging seabirds. Nevertheless, our results indicate they regulated their condition depending on environmental and physiological factors, with impacts on the amount of food delivered to young and pre-fledging mass. Parental choice of multiple foraging habitats and depletion of prey in the nearest habitat due to intraspecific competition have important implications in explaining contrasting patterns observed among studies investigating the life history trade-off model in birds. © Inter-Research 2010.

Ballard G.,PRBO Conservation Science | Jongsomjit D.,PRBO Conservation Science | Veloz S.D.,PRBO Conservation Science | Ainley D.G.,983 University Avenue
Biological Conservation | Year: 2012

Designation of an effective marine protected area (MPA) requires substantial knowledge of the spatial use of the region by key species, particularly those of high mobility. Within the Ross Sea, Antarctica, the least altered marine ecosystem on Earth, unusually large and closely interacting populations of several marine bird and mammal species co-exist. Understanding how that is possible is important to maintaining the ecological integrity of the system, the major goal in designating the Ross Sea as an MPA. We report analyses of niche occupation, two-dimensional habitat use, and overlap for the majority (9) of mesopredator species in the Ross Sea considering three components: (1) diet, (2) vertical distribution and (3) horizontal distribution. For (1) and (2) we used information in the literature; for (3) we used maximum entropy modeling to project species' distributions from occurrence data from several ocean cruises and satellite telemetry, correlated with six environmental variables. Results identified and ranked areas of importance in a conservation prioritization framework. While diet overlapped intensively, some spatial partitioning existed in the vertical dimension (diving depth). Horizontal partitioning, however, was the key structuring factor, defined by three general patterns of environmental suitability: (1) continental shelf break, (2) shelf and slope, and (3) marginal ice zone of the pack ice surrounding the Ross Sea post-polynya. In aggregate, the nine mesopredators used the entire continental shelf and slope, allowing the large populations of these species to co-exist. Conservation prioritization analyses identified the outer shelf and slope and the deeper troughs in the Ross Sea shelf to be most important. Our results substantially improve understanding of these species' niche occupation and imply that a piecemeal approach to MPA designation in this system is not likely to be successful. © 2011 Elsevier Ltd.

Ainley D.G.,983 University Avenue
Polar Record | Year: 2010

Recent analyses of anthropogenic impacts on marine systems have shown that the Ross Sea is the least affected stretch of ocean on Earth, although historical effects were not included in those studies. Herein the literature is reviewed in order to quantify the extent of extraction of biological resources from the Ross Sea continental shelf and slope from the start of the 20th century. There was none before that time. An intense extraction of Weddell seals Leptonychotes weddellii by the expeditions of the heroic period and then by New Zealand to feed sled dogs in the 1950-1980s caused the McMurdo Sound population to decrease permanently. Otherwise no other sealing occurred. Blue whales Balaenoptera musculus intermedia were extirpated from waters of the shelf break front during the 1920s, and have not reappeared. Minke whales B. bonaerensis probably expanded into the blue whale vacated habitat, but were then hunted during the 1970-1980s; their population has since recovered. Some minke whales are now taken in scientific whaling, twice more from the slope compared to the shelf. Other hunted cetaceans never occurred over the shelf and very few ever occurred in slope waters, and therefore their demise from whaling does not apply to the Ross Sea. No industrial fishing occurred in the Ross Sea until the 1996-1997 summer, when a fishery for Antarctic toothfish Dissostichus mawsoni was initiated, especially along the slope. This fishery has grown since then with effects on the ecosystem recently becoming evident. There is probably no other ocean area where the details of biological exploitation can be so elucidated. It appears that the Ross Sea continental shelf remains the least affected of any on the globe. However the same cannot be said of the slope. © Cambridge University Press 2009.

Ainley D.G.,983 University Avenue | Ballard G.,PRBO Conservation Science
Aquatic Mammals | Year: 2012

Foraging events and related trends in numbers of Type-B and -C killer whales (Orcinus orca) are reported for the vicinity of Ross Island, Ross Sea, Antarctica between 2002 and 2010. Updating an earlier report, the frequency of sightings and the number of individuals per sighting of Ross Sea killer whales (Type-C; RSKWs), a fishing-eating ecotype, has continued to decrease in a pattern coincident with a decrease in the number and size of an important prey: Antarctic toothfish (Dissostichus mawsoni). Increasingly rare, large fish are much more energetically dense and may also be socially important to the whales, a relationship with potential parallels to that known between well-studied fish-eating killer whales and large Chinook salmon (Oncorhynchus tshawytscha) in the northeast Pacific. In contrast, the prevalence of the larger, mammal-eating Type-B killer whales has not changed in the southern Ross Sea study area. Predation events by Type-B killer whales involving Weddell seals (Leptonychotes weddellii), interest in large penguins, such as emperors (Aptenodytes forsteri), and lack of interest in small penguins, such as Adélies (Pygoscelis adeliae), are presented. In the case of both killer whale forms, the progressive seasonal breakup of fast ice in large bays bordering the Ross Sea likely provides reliable, enhanced foraging opportunities as prey are exposed one area at a time during summer. Given the apparent relationship between RSKW prevalence and the availability of large toothfish, we speculate that the current management strategy of Antarctic toothfish in the Ross Sea region threatens current population levels of RSKWs.

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