In 2014, the Bering Sea shifted back to warmer ocean temperatures (+2 oC above average), bringing concern for the potential for a new warm stanza and broad biological and ecological cascading effects. In 2015 and 2016 dedicated surveys were executed to study the progression of ocean heating and ecosystem response. We describe ecosystem response to multiple, consecutive years of ocean warming and offer perspective on the broader impacts. Ecosystem changes observed include reduced spring phytoplankton biomass over the southeast Bering Sea shelf relative to the north, lower abundances of large-bodied crustacean zooplankton taxa, and degraded feeding and body condition of age-0 walleye pollock. This suggests poor ecosystem conditions for young pollock production and the risk of significant decline in the number of pollock available to the pollock fishery in 2–3 years. However, we also noted that high quality prey, large copepods and euphausiids, and lower temperatures in the north may have provided a refuge from poor conditions over the southern shelf, potentially buffering the impact of a sequential-year warm stanza on the Bering Sea pollock population. We offer the hypothesis that juvenile (age-0, age-1) pollock may buffer deleterious warm stanza effects by either utilizing high productivity waters associated with the strong, northerly Cold Pool, as a refuge from the warm, low production areas of the southern shelf, or by exploiting alternative prey over the southern shelf. We show that in 2015, the ocean waters influenced by spring sea ice (the Cold Pool) supported robust phytoplankton biomass (spring) comprised of centric diatom chains, a crustacean copepod community comprised of large-bodied taxa (spring, summer), and a large aggregation of midwater fishes, potentially young pollock. In this manner, the Cold Pool may have acted as a trophic refuge in that year. The few age-0 pollock occurring over the southeast shelf consumed high numbers of euphausiids which may have provided a high quality alternate prey. In 2016 a retracted Cold Pool precluded significant refuging in the north, though pollock foraging on available euphausiids over the southern shelf may have mitigated the effect of warm waters and reduced large availability of large copepods. This work presents the hypothesis that, in the short term, juvenile pollock can mitigate the drastic impacts of sustained warming. This short-term buffering, combined with recent observations (2017) of renewed sea ice presence over southeast Bering Sea shelf and a potential return to average or at least cooler ecosystem conditions, suggests that recent warm year stanza (2014–2016) effects to the pollock population and fishery may be mitigated.

The role of behavior, especially vertical migration, is recognized as a critical component of realistic models of larval fish dispersion. Unfortunately, our understanding of these behaviors lags well behind our ability to construct three-dimensional flow-field models. Previous field studies of vertical behavior of larval Pacific cod (Gadus macrocephalus) were limited to small, preflexion stages (£11 mm SL) in a narrow range of thermal conditions. To develop a more complete picture of larval behavior, we examined the effects of ontogeny, temperature, and light on vertical responses of larval Pacific cod in experimental columns. While eggs were strictly demersal, yolk-sac larvae displayed a strong surface orientation as early as 1 day post hatch ( 5 mm SL). Consistent with field observations, small preflexion larvae (<10 mm SL) showed no response to varying light levels. However, there was a direct effect of temperature on larval behavior: Pacific cod larvae exhibited a stronger surface orientation at 4°C than at 8°C. The behavior of larger, postflexion larvae (>15 mm SL) in experimental columns was consistent with a diel vertical migration and independent of water temperature: fish were more widely distributed in the column, and median positions were consistently deeper at higher light levels. These laboratory observations are combined with observations from discrete-depth (MOCNESS) sampling in the Gulf of Alaska to characterize the vertical distribution of larval Pacific cod and contrast ontogenetic patterns with walleye pollock (Theragra chalcogramma). The vertical movements of larval Pacific cod described here will be applied in the development of dispersal projections from Gulf of Alaska spawning grounds.

The Dibba Zone, Northern Oman Mountains, documents the history of an oblique-rifted (transtensional) segment of the Arabian passive margin. Unmetamorphosed Palaeozoic, pre-rift (Ordovician to ?Devonian) successions, exposed in rifted continental slivers (Oman Exotics), record stable siliciclastic and carbonate platform deposition. Early Permian rifting of the Neo-Tethys initiated a carbonate platform in the Musandam Peninsula, while shallow marine bioclastic carbonate and quartzose sediments accumulated in the subsiding axial zones (Asfar Fm., Jebel Qamar Exotics). During final continental break-up, in the Late Triassic-Early Jurassic, a carbonate platform in the Musandam Peninsula was bordered by an escarpment-bypass margin with a turbiditic apron to the southeast (Zulla Fm.). Rifted continental slivers underwent mass-wasting, giving rise to detached blocks, or olistoliths that slid into organic-rich muds and turbiditic sands (Kub Melange). During the Jurassic, the subsiding Musandam carbonate platform was bordered by a steep slope (Sumeini Gp.) and redeposited carbonates accumulated on the continental rise (Guweyza Limestone Fm.). A switch to mainly siliceous accumulation, from Late Jurassic to Early Cretaceous (Tithonian-Berriasian Sid'r Fm.) ensued, mainly in response to tensional faulting, combined with eustatic sea level rise. Following re-establishment of the platform, carbonate sediment was again shed into the basin in the Early Cretaceous (Nayid Fm.). During Cenomanian time, tholeiitic and alkaline basalt extrusions formed seamounts that locally built-up into shallow water (99-92 Ma). Platform deposition halted in the Turonian (c. 90 Ma), with flexural upwarp and erosion, followed by subsidence and slumping of shelf edge and upper slope sediments into a syntectonic foredeep, accumulating siliceous sediments and redeposited lithoclastic carbonates (Riyamah unit, Muti Fm.). Associated with emplacement of the Semail ophiolite, the passive margin successions were then imbricated by foreland-progagating thrusts (76-65 Ma), modified by the effects of possible oblique convergence, sidewall ramping and late-stage (dorsal) culmination collapse. Following erosion in the Campanian-Maastrichtian (Juweiza Fm.), platform deposition was reestablished in Palaeocene-early Oligocene. Renewed compression after mid-Eocene resulted in folding and reverse faulting of the Dibba Zone and thrust culmination of the Musandam shelf carbonates, driven by incipient continent-continent collision in the Zagros area.

Describing essential habitat is an important step toward understanding and conserving harvested species in ecosystem-based fishery management. Using data from fishery-independent ichthyoplankton, groundfish surveys, and commercial fisheries observer data, we utilized species distribution modeling techniques to predict habitat-based spatial distributions of federally managed species in Alaska. The distribution and abundance maps were used to refine existing essential fish habitat descriptions for the region. In particular, we used maximum entropy and generalized additive modeling to delineate distribution and abundance of early (egg, larval, and pelagic juvenile) and later (settled juvenile and adult) life history stages of groundfishes and crabs across multiple seasons in three large marine ecosystems (Gulf of Alaska, eastern Bering Sea, and Aleutian Islands) and the northern Bering Sea. We present a case study, featuring Kamchatka flounder (Atheresthes evermanni), from the eastern and northern Bering Sea to represent the >400 habitat-based distribution maps generated for more than 80 unique species–region–season–life-stage combinations. The results of these studies will be used to redescribe essential habitat of federally managed fishes and crabs in Alaska.