As mentioned
in the previous blog entry, Middleton Island got the attention of science at a
relatively early point in time. Due to its unique location and well preserved
geological features, over the years the island attracted the attention of many
geological researchers. Middleton Island, located near the margin of the
continental shelf in the northern Gulf of Alaska, has emerged from the sea
during several major episodes of co-seismic uplift of about 7 m, 8 m, 6 m, 9 m
and 7.5 m, which are recorded by marine terraces. These uplifts have been dated
at roughly 4,300, 3,800, 3,100, 2,390 and 1,350 radiocarbon years before
present, respectively. The most recent uplift took place during the 1964 Alaska
Earthquake, when on March 27 the whole island got lifted up another 3.5 m on
average (Plafker & Rubin 1978).
In contrast
with the geological interest the island has received during previous decades,
the number of biological studies conducted on Middleton that have a clear
relationship with the island is relatively small. Thus far the most important
moment in the recorded natural history of Middleton took place in June 1956,
when a field party consisting of Dr. Norman J. Wilimovsky (U.S. Fish and
Wildlife Service), Dr. John H. Thomas (Stanford University) and Robert Rausch (Arctic
Health Research Center, Public Health Service) undertook a biological
reconnaissance of Middleton Island. Their visit had been arranged because of
military activities on the island (at that time there was a large scale Cold
War radar station under construction) were likely going to cause imminent
disruption of the island’s natural relationships. This made it desirable to record
as much as possible of the island’s natural history before the opportunity was
lost. Their work was supported mainly by the Office of Naval Research and the
United States Air Force, but additional support was provided by the Arctic
Research Laboratory, Stanford University and the Arctic Health Research Center.
These studies were aided by a contract between the Office of Naval Research,
Department of the Navy, and the Arctic Institute of North America (Rausch 1958).
As far as I
could see the 1956 biological reconnaissance resulted in three publications.
Robert Rausch described the island’s avifauna in “The Condor” in 1958 and John
Thomas published his story about the island’s vegetation in “Contributions of
the Dudley Herbarium” in 1957. During their stay in 1956, the party also
assembled a small collection of mollusks from the intertidal area, which had
been submitted to the California Academy of Sciences for identification.
Eventually G. Dallas Hanna and Leo George Hertlein identified the marine shells
and these were listed and described in 1959 in “The Nautilus, The Pilsbry
quarterly devoted to the interests of conchologists marine shells”.
During my first
stay on Middleton Island in 2005, however, I noticed that during recent decades
little had been published about the general wildlife of the island and that the
available works about the vegetation and avifauna (Thomas 1957; Rausch 1958)
were largely outdated, especially due to some severe (a-)biotic changes that occurred
during the decades following these publications. For me this was a good reason
to start several studies on Middleton Island’s wildlife, focusing on the development
of both vegetation and avifauna, in particular breeding birds. These studies
started a year later and are keeping me pretty occupied up to the present day.
With this
blog entry, the first of a series of three, I want to focus on the results of
the 1956 biological reconnaissance of Middleton Island and share with you some
of my thoughts on these and maybe present some preliminary results of my own studies
in relation to these.
This first entry,
however, is about a subject I know very little about and I can’t write much
about either: the marine shells of Middleton Island. Now it already took me a
considerable amount of time and effort some years ago finding a copy of Thomas’
1957 vegetation study, I never managed to find a complete copy of Dallas Hanna’s
and Hertlein’s work on the identified marine shells of Middleton Island. Until
yesterday that is! The good news is that the whole edition of The Nautilus is now
freely available online:
Dallas Hanna
and Hertlein write about the collected material: “Twenty-one species are
present in the lot and also one barnacle. To these may be added for reference
purposes, two additional species cited by Dall (1921, pp. 32, 107) from
Middleton Island. Thus the known marine mollusks from this island consist of 5
pelecypods, 14 gastropods, 3 chitons, 1 cephalopod and one barnacle. All, with
one possible exception, are known to occur in waters of this general region at
the present time. However, this one, Littorina
arctica, may have been cited in Alaskan literature under a different name.”
(Dallas Hanna and Hertlein 1959)
Now does
this mean that the subject has been studied enough by now? Certainly not!
Dallas Hanna and Hertlein already give two reasons why further study of the molluscan
fauna could be very interesting:
“A
geological investigation of the islands has been made by Don. J. Miller (1953),
of the U. S. Geological Survey. During the course of his work he obtained 20
species of mollusks (identified by F. Stearns MacNeil) from Pleistocene
sedimentary beds. Oddly enough, none of these species was found in the collection
being considered here. It is practically certain that the lists of both fossil
and recent species represent only a small portion of the total molluscan fauna
of the island and adjacent waters.” (Dallas Hanna and Hertlein 1959)
Now I can
come up with several more reasons to show some interest in the intertidal life
around Middleton Island:
- After the 1956 biological reconnaissance the
1964 Earthquake lifted up the whole island about 3.5 m on average, creating a
new and more extensive intertidal zone around the island. This meant that the area
that had initially been inspected by the 1956 field party currently makes up a
permanent part of the island and does not contain live marine mollusks anymore.
How did the new intertidal zone develop?
Intertidal area at the island's south end in 1960 (photo: Armand Biron)
Intertidal
area in the upper east part of the island in 2005. No clear intertidal zone
could be identified here before the 1964 Earthquake (photo: T. van Nus).
- The island
remains under constant influence of seismic activity in the area, resulting in
a small but continuing uplift or tilt (Prescott, W.H. and Lisowski, M. 1977;
personal observations). It would be interesting to find out how over time this
uplift affects the occurrence of mollusk species in the area
- Personal
observations of the current intertidal zone indicate that this area can make up
about half of the total size of the island itself (which is about 2 x 7.5 km).
The new intertidal zone has become a majorly important foraging area for both
breeding birds as well as a large number of spring and fall migrants, in particular shore birds. Very
little is known what these birds find there and whether the availability of
food is a limiting factor for them.
- Personal
observations also suggest that intertidal life can be diverse but there are
large annual changes occurring; in example the growth of kelp sp. varies a lot
among years. Sea Otters (Enhydra lutris) established themselves for the first time in recorded
history in the winter of 2008/2009 (van Nus, personal records). What is going
on here?
Sea Urchins
were very common during my first visits to Middleton in 2005 but were not
seen often during
later visits. At the same time growth of Kelp appeared to increase
(photo:
T. van Nus).
Now I never
managed to find enough time to put effort into a study of the
intertidal life around Middleton Island and I believe the challenge is still
there, but it better needs to be done soon before another opportunity is lost..!
Literature
Miller, D. J. 1953. Late cenozoic marine glacial sediments and marine terraces of Middleton Island, Alaska Journal of Geology, 61:17-40.
Plafker, George, and Rubin, Meyer, 1978, Uplift history and earthquake recurrence as deduced from marine terraces on Middleton Island, Alaska, in Proceedings of Conference VI, Methodology for identifying seismic gaps and soon-to-break gaps: U.S. Geological Survey Open-File Report 78-943, p. 687-721.
Prescott, W.H. and Lisowski, M. 1977. Deformation at
Middleton Island, Alaska, during the decade after the Alaska earthquake of 1964
Bulletin of the Seismological Society of America June 1977 67:579-586
Rausch R.
1958. The occurrence and distribution of birds on Middleton Island, Alaska. The
Condor 60: 227-241.
Shepard
Oldroyd, I. 1924 – 1927. The Marine Shells of the West Coast of North America.
Four Volumes. Stanford, California. Stanford University. 1520 pp. illus. ISBN: 9780804709873
Four Volumes. Stanford, California. Stanford University. 1520 pp. illus. ISBN: 9780804709873
Thomas, J.
H. 1957. The vascular flora of Middleton Island, Alaska. Contrib. Dudley
Herbarium, 5:39-56.
Scattered boulders along the western shoreline (T. van Nus).