Alaska Science Center
Terrestrial Plants and Animals
All of Kasatochi Island is covered with layers of ash and pyroclastic flow material. Most, if not all, bird and marine mammal breeding habitat was covered. Intertidal and nearshore subtidal communities were overrun by hot, fast moving pyroclastic flows and subsequently covered by ash and sand. Due to long-term studies by the Alaska Maritime National Wildlife Refuge the following pre-eruption data are available:
These data are critical for assessing acute impacts of the eruption and the long-term ecological response. Seabirds were the dominant vertebrates on Kasatochi Island prior to the eruption and the most prominent linkage between marine and terrestrial ecosystems. Recolonization of Kasatochi Island by seabirds will depend on the availability of suitable nesting habitat which includes steep terrain for cliff-nesting birds, boulder piles, rubble and talus for auklets, and low-growing vegetated slopes for burrow-nesting murrelets and storm-petrels. Availability of these habitats will depend on erosion of ash and revegetation of the island. Revegetation will depend upon development of suitable soils and source materials for plants.
Stephen S. Talbot, U.S. Fish and Wildlife Service, Region 7
Much of the vegetation of Kasatochi was likely destroyed by temperatures of several hundred degrees before it was buried under up to 10 meters of ash and pyroclastic debris in the 2008 eruption. Lack of vegetation—as well as stability of volcanic substrates— will likely inhibit recolonization of Kasatochi Island by some burrow-nesting seabirds. Our work is focused on monitoring the reestablishment of plants and the development of vegetative communities, and comparing these observations with data collected on vegetative communities prior to the eruption. We are addressing the following questions:
Do any of the vegetative communities that existed prior to the eruption remain on the island?
In 2009, we searched Kasatochi Island for remnant vegetation and signs of revegetation. We also made observations at all pre-established plots. We established additional sampling sites based on geomorphic features that emerged as the result of erosion in concert with investigations of soils and terrestrial arthropods. The areas adjacent to the plots will be searched for vegetation. If any plants are found, cover-abundance will be estimated for all vascular plants, bryophytes, and lichens. Plant nomenclature will follow U.S. Department of Agriculture, Natural Resources Conservation Service.
For example, figure 1 shows a representative plot assigned to the post eruption Leymus mollis bluff ridge vegetation type. This is a species-poor, post eruption type that occurred primarily on bluff ridges that were wave-cut cliffs prior to the eruption. Although the type is considered species-poor, the mean species diversity was generally higher than the other post eruption types, and we consider this type to be a relict of the formerly widespread Lupinus nootkatensis - Festuca rubrameadows that characterized Kasatochi prior to the 2008 eruption. The plot is represented by 11 species, of which 8 are discernable in the photograph: Leymus mollis, Angelica lucida, Conioselinum gmelinii, Ranunculus occidentalis (yellow flowers), Festuca rubra, Achillea millefolium v. borealis, Anemone narcissiflora v. villosissima, and Anaphalis margaritacea.
Figure 2 depicts members of the post-eruption Aleuria aurantia slope barrens vegetation type. This type was characterized by the presence of the bright orange acomycete fungus Aleuria aurantia and the moss Ceratodon purpureus. This plot also included the liverwort Marchantia polymorpha and the vascular plant Lupinus nootkatensis. The fungus and moss species are cosmopolitan species that often occur on bare soil and disturbed sites; it is unknown whether these individuals are post-eruption colonizers to Kasatochi, or survived the eruption. The lupine is likely derived from roots/rhizomes that survived the eruption, and like other legumes are nitrogen fixers and can enrich sterile soils; such plants often dominate early succession communities. Similarly, the moss Ceratodon is known to fix nitrogen; there is also some speculation that cyanobacteria symbionts associated with Marchantia may trap and convert atmospheric nitrogen. The photograph shows all 4 species: Aleuria aurantia, Ceratodon purpureus, Marchantia polymorpha, Lupinus nootkatensis.
Colonization Genetics of Plants Following the Eruption of Kasatochi
Sandra Talbot, USGS, Alaska Science Center
It is well understood that the founding of populations through colonization and spatial spread subsequent to cataclysmic events, such as the 2008 eruption of Kasatochi in the Aleutian Islands, can profoundly influence later population and community structure, and ultimately, the nature and structure of the newly evolving island ecosystem. The habitat newly created by volcanoes can provide ecologists with a large-scale, natural laboratory in which to examine directly the genetic consequences of colonization on communities and their assembly; this is particularly true if genetic patterns are captured soon after founding events. The eruption of Kasatochi destroyed most of the vegetation of the island, as well as animal populations that were unable to escape the event. The goal of this project is to 1) use molecular methods to identify plant founders and their sources, whether from surrounding or more distant islands, or from adult plants that survived the eruption, and 2) provide archival material that will allow researchers to monitor the genetic consequences of successional colonization and community assembly of plants on Kasatochi.
This research will serve as an initial phase for other studies to address two long-term objectives, both of which require annual monitoring of primary plant succession. The primary long-term objective is to develop a genetic database for contemporary current-dispersed (hydrochores), wind-dispersed (anemochores), and animal-transported (zoochores) plant species collected from islands in the vicinity of Kasatochi, elsewhere along the Aleutian chain, as well as Kasatochi itself (given survival of adult plants) so that we may be able to track, and attempt to understand, natural processes of species colonization, biotic assembly, and succession that characterizes the creation of functioning communities. This research will therefore clarify the role of founder group formation on volcanic islands, which often lacks clarity because most studies were not performed immediately after the colonization event, and rarely are potential source populations screened for genetic characteristics prior to colonization.
The second long-term objective is to collect and archive tissue samples from a larger suite of plant species, less likely to be primary colonizers but likely to colonize Kasatochi in the future, from other islands. This will allow the eventual assignment of intermediate successors, which can contribute to the vegetation community up to several hundreds of years post-eruption. Archival of samples collected from other islands soon after the eruption will provide valuable investigation tools for future research and monitoring efforts.
Jeff Williams, U.S. Fish and Wildlife Service
Birds have been studied on Kasatochi by the U.S. Fish and Wildlife Service continually since 1996 providing precise data from which to evaluate acute impacts and ecosystem recovery. The pre-eruption avifauna on Kasatochi was dominated by massive numbers of crested and least auklets – perhaps a couple hundred thousand in total. Auklets nested in interstitial spaces in beach boulders and talus fields. Most, if not all of this auklet nesting habitat was covered by the eruption in 2008. Although many birds, particularly unfledged young, were likely killed during the eruptions, we assume that most adult birds escaped the explosion and some species may already be using the island for roosting.
We have many questions about the impact of this event on auklets. Will auklets try to reestablish colonies on the island? Does any habitat remain or are former beach boulders and talus slopes completely covered for the foreseeable future? Was new nesting habitat created? Given the erosion of coastline that is expected, what is the potential for creation of new habitat? Where specifically will these auklets choose to nest in the future? Since auklet breeding colonies are concentrated in relatively few locations worldwide (most on volcanic islands), the loss of one colony has significant ramifications. If volcanic activity is a natural and frequent event on a geologic time scale, how do auklet colonies typically respond to this perturbation?
In order to study the response of auklets and other birds to the loss of their nesting habitat on the island, all pre-eruption data on distribution and abundance were summarized to provide a “before” status. This includes GPS coordinates of historic plots and GIS layers of known distribution for as many species as possible on the island and in nearshore marine waters. Sampling was conducted in 2009 of all historic plots and transects to document abundance “after” the eruption.
Crested and Least Auklets: We will determine if birds continue to attend the site of their former colony despite the expected complete lack of breeding habitat. In northern auklet colonies, snow cover can persist late into the traditional breeding period. When this happens, birds stand around on the surface of the colony above their traditional nesting sites waiting for the snow to melt so that they may begin breeding. It is possible that returning auklets which escaped the direct effects of the eruption might act as if the ash was continuous snow cover for some period of time. Therefore we will count and photograph birds during site visits, and assess how long they remain at the colony before abandoning. To determine reuse and prospecting of the site, automated recording cameras or song meters will be set up at former colony locations to record vocalizations. Cameras and song meters will be programmed to record during traditional periods of colony attendance (e.g., early morning) to determine if birds use or continue to visit historic breeding sites.
Nocturnal seabirds (Fork-tailed and Leach’s Storm-petrel, Whiskered Auklet, Ancient Murrelet): Our monitoring studies showed that these species were in the early process of recovery from predation of introduced arctic foxes, which were removed from the island in 1985. To determine reuse and prospecting of former breeding sites, we set up automated recording devices or song meters to record vocalizations and flyovers. Song meters were programmed to record during traditional periods of colony attendance to determine if birds use or continue to visit historic breeding sites. As most of these nocturnal species burrow into the ground, we examined terrestrial habitat for signs of burrows.
Roosting seabirds (e.g. gulls, guillemots, cormorants): Direct counts were made of all roosting birds and locations of groups were delineated with GPS during foot surveys over the island and during nearshore boat surveys around the coastline of the island.
Raptors: Because of the large numbers of breeding seabirds present on the island prior to the eruption, healthy populations of breeding raptors were present on this small island. Normally 2 pairs of bald eagles and up to 5 pairs of peregrine falcons nested and hunted on the island. At least 1 falcon was seen after the eruption, but it is unknown if others survived. Will these top predators leave this location if large numbers of birds do not return? Are nearby colonies of seabirds close enough to continue to support this high density of raptors? We counted and record locations of raptors during our visit to Kasatochi for comparison.
Passerines: We resurveyed the established point count route based on GPS coordinates of the center stakes. Habitat and birds were documented with standard point count forms.
Previous to the eruption, approximately 1,000 Steller sea lions traditionally occupied a rookery at the north side of Kasatochi. That area is now covered with ash. Numbers and locations of sea lions will be determined whether this endangered species still occupies and breeds on Kasatochi in 2009.