Day R.H.,ABR Inc. Environmental Research and Services |
Weingartner T.J.,University of Alaska Fairbanks |
Weingartner T.J.,National Oceanic and Atmospheric Administration |
Hopcroft R.R.,University of Alaska Fairbanks |
And 11 more authors.
Continental Shelf Research
We conducted an interdisciplinary ecological study in and near 3 nearby proposed exploratory oil and gas prospects in the offshore northeastern Chukchi Sea during the open-water seasons of 2008-2010. This region exhibits a classical pelagic-benthic dichotomy of food-web structure in ecological function. The Klondike study area borders the eastern edge of the Central Channel and functions as a pelagic-dominated ecosystem, whereas the Burger study area lies south of Hanna Shoal and functions as a benthic-dominated ecosystem. The Statoil study area, which is located north of Klondike and northwest of Burger, has both pelagic and benthic attributes, although it is more like Burger than like Klondike. Klondike has lower benthic density and biomass, a higher biomass of oceanic zooplankton, and more fishes and planktivorous seabirds than does Burger, which has benthic communities with high density and biomass, primarily neritic zooplankton, and higher densities of benthic-feeding marine mammals than Klondike; Statoil has characteristics of both ecosystems. Patterns of sea-ice retreat vary interannually; in some years, much of the northeastern Chukchi is ice-free by mid-May, leading to pelagic and ice-edge phytoplankton blooms, whereas heavy ice cover in other years leads to substantial within-ice production. The characteristics of this region during the open-water season are not consistent among years, in that Bering Sea Water impinges onto all study areas only in some years, resulting in interannual variation in the distribution and abundance of zooplankton, planktivorous seabirds, and pelagic-feeding seals. These interannual variations alter several aspects of this pelagic-benthic dichotomy, and some aspects of this region suggest unusual structure (e.g., replacement of benthic-feeding fishes in some areas by predatory invertebrates, a lack of benthic-feeding seaducks). © 2013 Elsevier Ltd. Source
Aerts L.A.M.,LAMA Ecological |
McFarland A.E.,Fairweather LLC |
Watts B.H.,Fairweather LLC |
Lomac-MacNair K.S.,Northern Exploration Services LLC |
And 4 more authors.
Continental Shelf Research
This paper describes the distribution and abundance of marine mammals during the open-water season within and near three offshore oil and gas prospects in the northeastern Chukchi Sea, known as the Klondike, Burger, and Statoil study areas. We collected vessel-based marine mammal data during July-October 2008-2010 along line transects oriented in a north-south direction. Over this period, we surveyed ~18,600. km of on-transect effort in the three study areas. Sightings of cetaceans were rare. The bowhead whale was the primary cetacean species sighted and was mostly observed in October (33 of 35 animals). Pinnipeds were the most abundant marine mammals in the study area, with 980 seals and 367 walruses recorded on transect. Most seals were observed as solitary animals, while walruses were often observed in aggregations. We calculated seal and walrus densities using species-specific detection functions corrected for probability of detection. There was high interannual variability in the abundance of seals and walruses that for some species may be related to interannual differences in ice conditions. Notwithstanding this variation, the distribution data suggest that benthic-feeding bearded seals and walruses generally were more common in the Burger and Statoil study areas, which can be characterized as more benthic-dominated ecosystems. The distribution of ringed/spotted seals did not show any statistically significant differences among the study areas, although a slight preference for the Klondike and Statoil study areas was suggested. Both of these study areas are affected by Bering Sea Water from the Central Channel and have a stronger pelagic component than the Burger study area. Continued sampling of these areas will help establish whether the observed trends in marine mammal distribution and abundance are persistent. © 2013 Elsevier Ltd. Source
Clarke J.,Leidos |
Stafford K.,University of Washington |
Moore S.E.,National Oceanic and Atmospheric Administration |
Rone B.,National Oceanic and Atmospheric Administration |
And 2 more authors.
The southern Chukchi Sea is one of the most productive areas in the world ocean. Over the past decade, there have been dramatic changes in this region in sea ice cover and in Bering Strait inflow, and it is now in the path of transpolar shipping and destinational ship traffic, including vessels supporting Arctic offshore oil and gas development and tourism, all of which are anticipated to increase with decreasing seasonal sea ice cover. Little research on cetaceans has been conducted in the southern Chukchi Sea, and most information on the occurrence of subarctic species (humpback whale Megaptera novaeangliae, fin whale Balaenoptera physalus, minke whale B.acutorostrata, and killer whale Orcinus orca) comes from the ships' logs of commercial whalers in the mid to late twentieth century and from observers stationed along the Chukotka Peninsula. Information on cetacean seasonal occurrence east of the International Date Line (IDL) in US waters is particularly scarce. To address this information gap, we compiled visual sightings and acoustic detections of subarctic cetaceans in the southern Chukchi Sea during summer and early autumn from 2009 to 2012. Humpback whales were common on both sides of the IDL in August and September. Fin and minke whales were widely distributed east of the IDL from July to September, and killer whales were seen sporadically but were the most widely dispersed of the four species. Comparisons of our results with historical records indicate that the incidence of subarctic cetaceans may be increasing in the southern Chukchi Sea. An increase in occurrence may simply be a post-commercial whaling recovery of whale numbers and seasonal range by each species, or it may reflect responses to ongoing climate change. Understanding current stock identity, spatial and temporal distribution, habitat preference, relative abundance, and potential impacts of climate change on these species will require cetacean-focused research in this region of the Arctic. © 2013 by The Oceanography Society. All rights reserved. Source