Moret-Ferguson
Skye E.
Moret-Ferguson
Skye E.
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ArticleInfluence of Central Pacific oceanographic conditions on the potential vertical habitat of four tropical tuna species(University of Hawai'i Press, 2015-10) Deary, Alison L. ; Moret-Ferguson, Skye E. ; Engels, Mary ; Zettler, Erik R. ; Jaroslow, Gary E. ; Sancho, GorkaClimate change has resulted in the geographic and vertical expansion of oxygen minimum zones but their impact on the vertical distribution of commercially important species, such as tunas, is not well understood. Although La Niña events are characterized by increased upwelling along the equator, the increased primary productivity and bacterial proliferation drive the expansion of oxygen minimum zones. Vertical habitat of four tropical tuna species were characterized using direct observations of the oceanographic conditions of the Central Pacific Ocean during the 2008 La Niña event and existing primary literature on temperature and dissolved oxygen physiological tolerances for these tunas. Concentrations of potential prey were estimated using Acoustic Doppler Current Profiler raw backscatter and surface zooplankton tows. Based on the oceanographic conditions observed from February to June, low dissolved oxygen levels, more so than low temperatures, were inferred to restrict the predicted vertical habitat of four commercially important tuna species (bigeye, yellowfin, skipjack, and albacore). During peak La Niña conditions, temperature and dissolved oxygen tolerance limits of all four tuna species were reached at approximately 200m. Zooplankton and myctophid fish densities peaked in the upper 200m between 0° N and 5° N, which corresponded to a region with a shallow thermocline (150 m). Our findings suggest the possibility that competition and susceptibility to surface fishing gears may be increased for tropical tunas during a strong La Niña event due to vertical habitat restrictions.
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ArticleDistribution of surface plastic debris in the eastern Pacific Ocean from an 11-Year data set(American Chemical Society, 2014-04-07) Law, Kara L. ; Moret-Ferguson, Skye E. ; Goodwin, Deborah S. ; Zettler, Erik R. ; DeForce, Emelia A. ; Kukulka, Tobias ; Proskurowski, GioraWe present an extensive survey of floating plastic debris in the eastern North and South Pacific Oceans from more than 2500 plankton net tows conducted between 2001 and 2012. From these data we defined an accumulation zone (25 to 41°N, 130 to 180°W) in the North Pacific subtropical gyre that closely corresponds to centers of accumulation resulting from the convergence of ocean surface currents predicted by several oceanographic numerical models. Maximum plastic concentrations from individual surface net tows exceeded 106 pieces km–2, with concentrations decreasing with increasing distance from the predicted center of accumulation. Outside the North Pacific subtropical gyre the median plastic concentration was 0 pieces km–2. We were unable to detect a robust temporal trend in the data set, perhaps because of confounded spatial and temporal variability. Large spatiotemporal variability in plastic concentration causes order of magnitude differences in summary statistics calculated over short time periods or in limited geographic areas. Utilizing all available plankton net data collected in the eastern Pacific Ocean (17.4°S to 61.0°N; 85.0 to 180.0°W) since 1999, we estimated a minimum of 21 290 t of floating microplastic.