Potential Kelp Habitat during the Late Pleistocene and Early Holocene in Southwestern
Southeast Alaska: Implications for Marine Mammals
James F. Baichtal, US Forest Service, Tongass National Forest
P.O. Box 19001 Thorne Bay, Alaska 99919
907-828-3248 jbaichtal@fs.fed.us
Susan J. Crockford, Pacific Identifications Inc.
6011 Oldfield Rd., RR 3, Victoria BC V9E 2J4
(250) 721-7296 sjcrock@shaw.ca
During the Last Glacial Maximum (LGM) in southeastern Alaska, a coastal forebulge developed
westward of continental ice. Exposed shell-bearing raised marine strata were used to generate a sea
level curve for southwestern Southeast Alaska from 10,000 RCYBP to the present, defining collapse of
the forebulge. Two points were used to generate a sea level curve from 14,000 to 10,000 RCYBP: 1) A
shoreline at about 14,000 RCYBP represented by a terrace along the paleoshoreline at a depth of -165m
dated by the eruption of a now submerged maar volcano, and 2) The 10,000 RCYBP point, at -70m,
comes from Core EW0408-11JC from the Gulf of Esquibel that shows a change from fresh water to salt
water at 9,997 RCYBP, indicating the time and depth of marine inundation. The sea level curve
generated by these combined data sets was found to be similar to those reported from Haida Gwaii,
British Columbia, Canada. A paleoshoreline model was developed from this sea level curve analyzing
the coastal bathymetry in 1000 year increments. Potential kelp habitat was modeled based on the
knowledge that kelp beds flourish today at depths of 15m or less. The results show a far greater amount
of kelp forest potentially
available in the late LGM than
exists today, habitat critical for a
variety of marine mammals,
including sea otter Enhydra
lutris, harbor seal Phoca vitulina,
and Steller sea lion Eumetopias
jubatus. Evidence from other
studies suggest this potential for
extensive kelp forests was likely
present along rocky shorelines to
various degrees from Yakutat,
AK south to Puget Sound, WA.
Such extensive kelp forests
available early in the deglaciation
period would have greatly aided
rapid re-colonization of the coast
by marine mammals forced south
by the emergence of Beringia and
presence of sea ice in the North
Pacific during the LGM.
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