How Would The Eruption Effect The Animals In North America?
Introduction
Kasatochi Island, located within the central Aleutian Islands of Alaska, erupted with lilliputian warning on 7–eight August 2008. A modest stratovolcano with no prior historical tape of eruption, the island was home to a rich community of largely marine fauna, consisting primarily of hundreds of thousands of seabirds and hundreds of marine mammals (Byrd et al., 2005). Following the 2008 eruption, Kasatochi was covered by upwards to 30 m of tephra that destroyed or covered almost all the wildlife convenance and foraging habitat on and effectually the island (Scott et al., 2010 [this issue]).
As ane of ix annual ecological monitoring sites in the Alaska Maritime National Wildlife Refuge (AMNWR), Kasatochi was the site of extensive biological surveys prior to the eruption. Bones inventory of wildlife resources at Kasatochi started in the 1980s and included gunkhole-based circumnavigations (e.grand., Bailey and Trapp, 1986) and incidental observations of wild animals during efforts to remove introduced arctic foxes (
Our goal was to examine the effects of the volcanic eruption of Kasatochi on convenance bird and marine mammal populations one twelvemonth after the event and to establish a baseline for quantifying the rate of recovery. Based on a brief helicopter visit and a ship-based offshore survey immediately after the eruption in late August 2008, and supplemented with a serial of satellite images during the winter of 2008–2009, initial impressions suggested all wildlife habitat on the island had been completely devastated. To assess the effects of the eruption, we visited Kasatochi in summertime 2009 to report the abundance and breeding status of wild fauna, evaluate the availability of habitat, and compare weather to those existing prior to the eruption. Specifically, nosotros addressed the following questions: (i) What were the straight and indirect effects on wildlife diversity, populations, and distribution? (2) Did any pre-eruption wild fauna habitat remain? (three) Was any new wildlife habitat created? (four) How would erosion of the overlying mantle of tephra influence the potential for creation of new habitat or recovery of old habitat? (5) If no habitat existed in 2009, how long would wildlife remain in the vicinity of the island?
Study Area and Methods
Written report Surface area AND PRE-ERUPTION CONDITIONS
Located approximately xix km northwest of the westernmost indicate of Atka Island, Kasatochi Island (52.17°Due north, 175.51°W) is a volcanic caldera that, prior to the eruption, encompassed approximately 287 ha and had a diameter of nearly 2.seven km. Until 2008, there were no reliable reports of the island being eruptive in historic times (Coats, 1950), although steam rose from the caldera and the caldera lake disappeared in 1899 (Jaggar, 1927) and bubbles were seen in the caldera lake in 2005–2007 (Drummond and Rehder, 2005; Drummond, 2006; Drummond and Larned, 2007). Recent piece of work suggests the last major eruption occurred between a few centuries and 1000 years agone (Scott et al., 2010 [this upshot]). The rim of the caldera rose to 314 m at its highest point and descended sharply inward to a 0.8-km-broad stagnant lake well-nigh bounding main level (Bailey and Trapp, 1986). At that place were no freshwater streams, ponds, or springs on the island. The southern one-half of the isle consisted mostly of gentle grassy slopes, with a coastline characterized past narrow sand or cobble beaches at the base of clay cliffs upward to 30 m high. The western coast comprised high rocky bluffs rising over boulder beaches, with grassy ravines sloping upwardly from the bluffs to the caldera rim. The northern coastline was dominated by sheer, impassable cliffs interspersed with rock slides and steep vegetated talus slopes.
Kasatochi'southward various terrain provided convenance habitat for a wide range of bird species: auklets (
PRE- AND Mail service-ERUPTION SURVEY METHODS
Pre-eruption data on abundance and breeding status are based primarily on observations nerveless from 1996 to 2008 as part of the long-term biological monitoring programme by AMNWR (Byrd, 2007; Drummond and Larned, 2007). From late May until late August or early September, survey crews annually collected data on population affluence, productivity, adult survival, and diet on a suite of species, including seabirds, shorebirds, raptors, passerines, and marine mammals. Population-survey techniques consisted of a multifariousness of methods, including nearshore circumnavigation surveys by inflatable skiff, country-based counts forth transects or on other plots, bespeak-counts, and records of daily wildlife observations (Williams et al., 2002). From these methods, we generated our best estimates of pre-eruption abundance. For many species, accurate isle-wide counts did not exist, and so we extrapolated from plot counts, based on our knowledge of distribution and the amount of available breeding habitat. For species with evidently stable populations over the by decade, we used data from all years (1996–2008) to generate abundance estimates. For species that had undergone a distinct change in population size over that flow (e.thousand., a steady decline in murres and an increase in sea lions), we used only data from recent years to judge pre-eruption abundance.
Following a cursory postal service-eruption offshore reconnaissance from the send M/5
We also recorded activity of colonial seabirds when nosotros were non on the island using two audio-visual recording devices (Vocal Meter model SM-1 with Firmware v1.6.0, Wildlife Acoustics, Inc., Concord, Massachusetts) to document vocalizations. Although no pre-eruption information exist for comparison, the song meters functioned every bit indicators of post-eruption species presence, specially for nocturnal species that we could not detect during daytime surveys. We deployed i song meter at Troll Talus (52.16889°N, 175.52423°W), the site of one of the larger nocturnal seabird colonies on the island before the eruption, and the second at Tundering Talus (52.17870°N, 175.52452°W), the location of the former large least and crested auklet (
In both pre- and postal service-eruption periods, population estimates were easier to attain and have higher precision for species that were easily counted. These species include those that were nowadays in low numbers with hands observed nest sites (e.g., raptors, shorebirds, cormorants) or that were restricted to one or a few singled-out, easily viewed convenance areas (e.g., sea lions concentrated at the northern rookery, glaucous-winged gulls [
We used differences in pre- and post-eruption population estimates and general noesis of wildlife behavior on the island to gauge percentage of adult mortality during the eruption. Nosotros quantified chick mortality based on the proportion of chicks still remaining in nests at the time of the eruption using timing of breeding data in 2008 and dates of showtime fledging observations from 1996 to 2008 (Buchheit and Ford, 2008). We identified postal service-eruption breeding attempts equally any observation of reproductive behavior (mating displays, mate allure vocalizations, copulation, or nest building activity) or eggs.
Results
SPECIES RICHNESS AND DIVERSITY
In 2009, we recorded 18 bird (murres [
Table 1 Detection of birds and marine mammals during post-eruption surveys at Kasatochi Island, Alaska, in 2009.
Earlier the eruption, between 1996 and 2008, 24 bird and two marine mammal species were confirmed as convenance at Kasatochi in at to the lowest degree one twelvemonth (Table ii). During the 2008 convenance season when the eruption occurred, ruby-red-faced cormorants (
Tabular array ii Furnishings of the August 2008 eruption on historically convenance birds and marine mammals at Kasatochi Island. Listing includes all historic confirmed breeders at Kasatochi, 1996–2008; most species bred every year, just crimson-faced cormorants, thick-billed murres, and common murres did non nest at Kasatochi during the 2008 breeding season even though adult birds were nowadays.
SPECIES ACCOUNTS
Diurnal Crevice-Nesting Auklet Species: Crested, To the lowest degree, and Parakeet Auklets
Crested, least, and, to a lesser extent, parakeet auklets (
Distribution of all three species in nearshore waters in June was concentrated just offshore from talus slopes, cliffs, and rocky beaches where they had nested earlier the eruption. On land, auklets landed and socialized on the surface of the former colony sites, and vocalizations of both crested and to the lowest degree auklets were recorded on the song meter at the Tundering Talus colony daily until the device malfunctioned on two July. Like to before the eruption, a pocket-sized number of auklets was seen flying within the caldera. Large numbers of auklets also explored, landed, and socialized on inland areas that did non take breeding habitat before the eruption, virtually notably on the southern portion of the isle.
Auklets tried to brood at Kasatochi in 2009, copulating on the water and socializing in pairs and larger groups on the water and the surface of the sometime colony. Almost all former auklet nesting crevices in talus slopes and beach boulders were entirely covered by tephra many meters thick (Fig. i), and we found hundreds of broken, not-predated auklet eggs out in the open on the arid surface of the old Tundering Talus colony. In addition, four crested auklet eggs were constitute past divers in small underwater plots immediately offshore (Jewett et al., 2010 [this event]), suggesting that auklets also were depositing their eggs in the water.
Initial Effects of the August 2008 Volcanic Eruption on Convenance Birds and Marine Mammals at Kasatochi Island, Alaska
Published online:
17 January 2018
Figure 1 Auklets on the colony surface at Kasatochi Island (a) before (June 2004; photograph by Brie Drummond) and (b) after the 2008 eruption (June 2009; photo past Gary Drew). Photos taken from approximately the aforementioned location.
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No new nesting habitat was created by the eruption itself, and little former nesting habitat buried in the eruption had been re-exposed by the 2009 breeding season. Throughout extensive land surveys in June, nosotros found but three small potential auklet breeding sites. First, along the northern shore of the island, a small rock pile (four m × 4 thou) formed by a collapsing cliff independent numerous calling birds, including a single crested auklet incubating an egg near numerous broken eggs. 2nd, at the top of Tundering Talus, a single crevice showed visible evidence of auklet apply (feathers, claw-marks in debris) and contained numerous arthropods normally associated with auklets (Sikes and Slowik, 2010 [this issue]). Finally, at the base of operations of Tundering Talus, wave-washed boulders were explored continuously past prospecting birds. By Baronial, no sites showed evidence of successful breeding, and the minor rock pile had been destroyed by erosion.
Nocturnal Crevice- and Burrow-Nesting Seabird Species: Fork-Tailed and Leach's Storm-Petrels, Ancient Murrelets, and Cassin's and Whiskered Auklets
Of nocturnal species that bred at Kasatochi earlier the eruption, we saw only four ancient murrelets and ane Leach'south storm-petrel (
On the isle, all erstwhile breeding habitat for nocturnal species (rock crevices or soil for burrowing) was buried nether the thick layer of tephra, and no visual show of nest digging or egg laying was constitute. The song meter at the one-time Troll Talus breeding colony, however, recorded the nocturnal presence of all 4 species that historically had nested there (fork-tailed and Leach's storm-petrels, ancient murrelets, and whiskered auklets). Fork-tailed tempest-petrels were heard near frequently, with 500–1400 flight and male calls recorded nightly between 16 June and xi August, when the song meter was retrieved. This high level of activity was comparable, and on some nights surpassed, the number of calls heard at the undisturbed storm-petrel colony at Buldir Island in the western Aleutian Islands (R. Buxton, unpublished information). High levels of aboriginal murrelet chirrup and song calls were also recorded every nighttime until 25 July. Whiskered auklets calls were recorded until 29 July at lower levels, with the near activity towards the end of each nightly recording period (0400–0415 h HAST). Leach's tempest-petrel chuckle calls were recorded only xiv times throughout the season (on iii, xviii, 26–29 July and 1 August). No chick calls of whatever nocturnal species were recorded.
Other Crevice- and Cliff-Nesting Species: Puffins, Cormorants, Pigeon Guillemots, Murres, and Raptors
We saw over 100 dove guillemots (
Ground-Nesting Species: Gulls, Shorebirds, and Passerines
We recorded no black oystercatchers (
We encountered four gull nests (containing 0, 0, 2, and iii eggs) outside of the caldera in June. Nests were constructed of expressionless
Marine Mammals
Simply two weeks after the 2008 eruption, over 100 Steller's sea lions were hauled out on newly created sandy beaches on the southern side of the isle. Similarly, in 2009, we saw sea lions on country and in nearshore waters in both June and August (Tabular array one). An aeriform survey conducted by National Marine Mammal Laboratory personnel on 4 July 2009 photographed 611 developed and subadult sea lions and 394 pups. Although the former rookery on a sloping rocky outcrop on the northern portion of the island had been completely covered past 30 k of tephra in August 2008, wave action had eroded the coastline by leap, and the rookery site was re-exposed for the 2009 breeding flavor. We encountered no harbor seals during mail-eruption surveys simply observed 2 orcas in June 2009 off the northeastern coast of the island, an surface area where they had been observed occasionally prior to the eruption.
Discussion
The eruption of Kasatochi volcano in 2008 had significant effects, both direct and indirect, on local marine wildlife. Fix in a broader context, however, this disturbance event took identify inside the volcanically active Aleutian Islands ecosystem and is illustrative of the type of disturbance that wild animals in the region have responded to for millennia (Byrd et al., 1980). Our surveys one year after the eruption suggest that wild animals was afflicted by and responded to the eruption in dissimilar means based on differences in life-history traits and habitat requirements.
DIRECT Effects
Direct effects of the eruption on wild fauna at Kasatochi consisted of mortality to both adults and immature. Our mail-eruption population estimates for most seabird and marine mammal species were similar to those earlier the eruption (Tabular array 2), suggesting that well-nigh adults survived the eruption. Such low adult mortality during the eruption itself was probably due to several factors. Beginning, the eruption took place in August, subsequently or toward the end of the breeding season for most species (Drummond and Larned, 2007), when colony attendance was becoming irregular and virtually adults were non tied strongly to nests. Second, the eruption occurred during the day, when nigh nocturnal tempest-petrel adults, who were all still attending nest sites, were away from the island on foraging trips. Finally, the eruption consisted of multiple eruptive events, with the first two poor in ash but high in gas emission and later events producing the meaning pyroclastic surge and flow cloth that blanketed the island (Scott et al., 2010 [this issue]). This eruption pattern could have allowed adults that could fly or swim abroad the time to escape the isle before the third, more than massive, eruption occurred. At that place undoubtedly was some pocket-size amount of incidental mortality, in that a minor number of birds still attention nests in crevices were likely entombed during the many earthquakes and landslides leading upwards to the offset eruption. In addition, glaucous-winged gulls and horned (
Despite relatively few visits to Kasatochi in 2009, our observations probably documented accurately the presence of formerly breeding species that returned to Kasatochi after the eruption due to the small size of the island and our all-encompassing familiarity with pre-eruption species distribution. Mail-eruption population estimates, however, may accept been inflated by an influx of additional birds in 2009. In many seabird populations, nesting habitat is limited and a large pool of non-breeders exists to make full sites as they go available (e.g., Porter and Coulson, 1987; Klomp and Furness, 1992). If these not-breeders returned to Kasatochi in 2009 and replaced breeding birds that perished in the eruption, we would not have detected a alter in population size. In improver, an explosion of food resources tin can attract predators from surrounding areas (Sherrod et al., 1976). The superabundance of auklet eggs and disoriented birds at Kasatochi in 2009 could accept brought in boosted gulls from nearby islands. Both furnishings could have caused us to underestimate adult seabird mortality.
In dissimilarity to seabirds, many state birds nigh certainly suffered loftier adult mortality. Nosotros failed to notice a single passerine or shorebird during all surveys in 2009, despite large pre-eruption convenance populations (Table ii). This absence suggests these birds may have perished in the eruption, similar to resident song birds in the Mt. St. Helens eruption of 1980 (Andersen and MacMahon, 1986; Manuwal et al., 1987; Crissafulli et al., 2005). At Kasatochi, this mortality probably occurred because passerines and shorebirds, more than strongly tied to the terrestrial environment than marine birds and mammals, did not fly away during the eruption. Many of these species were non-migratory (Gibson and Byrd, 2007), and those that do disperse at the cease of the season, such every bit Lapland longspurs (
Chick mortality was a major directly result of the Kasatochi eruption for both seabird and land bird species. At the time of the eruption in early August, all tempest-petrel, cormorant, and puffin chicks, nearly dove guillemot chicks, and many crested, least, and parakeet auklet chicks would have been too immature to exit the nest (Drummond and Larned, 2007; Buchheit and Ford, 2008) and, therefore, perished (Table 2). Nigh glaucous-winged gull chicks were incapable of flight at that time (Drummond and Larned, 2007) and given about nests were inside the caldera, probably died (Tabular array 2). Finally, except for fledgling baldheaded eagles and peregrine falcons, immature of about land birds were either too modest for long flights when the eruption occurred (due east.one thousand., black oystercatchers) or unlikely to disperse (due east.yard., not-migratory passerines). Based on pre-eruption population estimates (Table 2), boilerplate reproductive functioning at Kasatochi (Drummond and Larned, 2007) or nearby sites (e.g., Ewins, 1993; Hejl et al., 2002), and projections of eruption-induced chick mortality (Table 2), we estimate that approximately 20,000 to 40,000 chicks died during the eruption.
INDIRECT EFFECTS
Indirect effects of the Kasatochi eruption on wild fauna consisted primarily of the loss of breeding and foraging habitat. The near-complete loss of almost all types of breeding habitat following the eruption had a substantial impact on post-eruption nesting attempts and success of species that formerly bred on the island (Tabular array 2). Much of the wildlife at Kasatochi is strongly marine in graphic symbol and used the isle primarily as a nesting location. Nearly all the former convenance sites were destroyed when the eruption covered the island in up to 30 k of ash (Scott et al., 2010 [this issue]). Steller'southward bounding main lions were the merely species for which substantial re-exposure of breeding habitat occurred by 2009 and, every bit such, the only species to breed successfully at Kasatochi one twelvemonth afterwards the eruption.
Loss of foraging habitat following the eruption also impacted a number of species at Kasatochi (Tabular array 2), although to a bottom extent than loss of breeding habitat. Most marine birds at Kasatochi are fully dependent on the offshore marine environs away from the island for food (Drew et al., 2003, 2010 [this issue]; Dragoo, 2007), and then their foraging grounds were probably minimally affected by the eruption. The isle'south interior, beaches, and nearshore kelp community out to about the 20 m isobaths, however, were buried nether extensive droppings (Jewett et al., 2010 [this upshot]; Scott et al., 2010 [this issue]). Therefore, species that foraged in terrestrial vegetation or intertidal and nearshore-subtidal areas were impacted (Table 2), with the degree of bear on depending on the flexibility of their foraging strategies. For instance, black oystercatchers forage primarily in the intertidal zone (Andres and Falxa, 1995) and, thus, would have suffered a complete loss of foraging habitat. Glaucous-winged gulls, in contrast, historically fed on a mix of intertidal invertebrates and auklets at Kasatochi (Drummond and Larned, 2007) and were able to shift and feed exclusively on auklets and eggs for part of the 2009 convenance season.
POST-ERUPTION RESPONSE OF Wild animals
As indicated, many convenance species survived the 2008 eruption and returned to the island in comparable numbers, either immediately following the eruption (gulls and ocean lions) or for the 2009 breeding season (most other species; Table 2). Individuals generally exhibited strong site fidelity, returning to former breeding locations and distributing themselves in nearshore waters in like patterns as before the eruption. With the exception of ocean lions, nigh species were unable to access their previous breeding sites and, despite diverse attempts to reproduce, were not successful. Eventually, most birds abandoned convenance attempts and left the island; by Baronial 2009, only ocean lions and a few bird species remained (Table 1).
Specific responses of different species varied depending on life-history traits and availability of habitat. We categorized four different response levels (see Table 2). (1) Successful breeders. Steller'southward sea lions were the only species to render later the eruption and detect their convenance habitat comparable to pre-eruption conditions. During the wintertime, the tephra droppings fan that had originally covered the sea king of beasts rookery to a depth of 30 m and extended hundreds of meters offshore had eroded away by wave action. With their breeding habitat re-exposed, their foraging habitat not completely destroyed, and low direct adult mortality from the eruption, sea lions bred successfully in 2009 with numbers of pups higher than in recent years (National Marine Fisheries Service, unpublished data). (2) Unsuccessful breeders. These species fabricated some attempt to breed, with various levels of try. Aboriginal murrelets and tempest-petrels returned to quondam colony sites throughout the duration of what would have been their normal convenance season and were recorded ad for potential mates, merely did non announced to lay eggs or have chicks. Crested, least, and parakeet auklets exhibited ritualized pair behavior and copulated successfully but, with almost no nest sites available, they simply dropped eggs in the water and on the barren surface of their previous colonies, like to observations at St. Lawrence Isle when crevices were buried under deep snow (Sealy, 1975). Glaucous-winged gulls congenital a minor number of nests and laid and incubated eggs, but all eventually failed. (3) Did not try to breed. These species, including raptors and several seabird species, were seen only offshore or were non-territorial when on land, showing no indication of whatsoever convenance attempts. Given the abundance of readily available auklet prey in 2009, the failure of bald eagles and peregrine falcons to attempt to breed at Kasatochi afterward the eruption is specially surprising and may exist because of lack of suitable nest sites. (four) Did not return. These species, including passerines and shorebirds, either did non return to the isle or presumably died in the eruption.
THE Hereafter FOR Wildlife ON KASATOCHI
The future for wildlife at Kasatochi depends on when and how much convenance habitat becomes available and the return of sometime breeders. Although highly marine in nature for much of the year, seabirds and marine mammals at Kasatochi need the terrestrial surroundings for convenance sites and will be unable to re-establish on the isle without it. Steller'due south sea lions take already re-established successfully with the exposure of their breeding habitat, but seabird species require farther erosion of the thick tephra layer roofing the island's surface to re-expose potential nest sites. Since the eruption, Kasatochi has been undergoing a continual secondary disturbance of erosion that eventually will betrayal one-time habitat, as the sea removes unconsolidated droppings material and exposes rocky coastline while precipitation and current of air erode the island'due south surface (Scott et al., 2010 [this upshot]). The speed at which this erosion continues will determine the rate at which seabird populations can re-plant. With timely re-exposure of breeding habitat, recovery could occur quickly because Aleutian wildlife is adjusted to rapid exploitation of newly bachelor habitat in their geologically active surroundings. At Kiska Island, for example, crested and to the lowest degree auklets colonized a new lava flow and numbered in the millions just 10 years later the eruption (Twenty-four hours et al., 1979; Major et al., 2006). Seabird populations at Bogoslof Island responded similarly to changes in nesting habitat following eruptive events (Byrd et al., 1980). Given that seabirds are generally long-lived and faithful to breeding sites, information technology is likely that onetime breeders volition continue to render to Kasatochi in the near hereafter, ready to use habitat as before long equally it becomes available. Over time, if erosion is slow and nest sites do not reappear, the birds which survived the eruption will either motion to other colonies, constitute a new colony elsewhere, or perish.
The recovery of species that were killed in the eruption and that rely on the terrestrial environment for foraging and breeding will likely be much slower to re-establish populations (Petersen, 2009). Recolonization of passerines and shorebirds volition depend on the recovery of terrestrial establish and intertidal communities and new birds arriving from nearby islands. On tiny Bogoslof Island, early-successional-phase vegetation took nearly 50 years to become abundant and widely dispersed (Byrd et al., 1980) and it may take longer on the larger island of Kasatochi (Petersen, 2009; Talbot et al., 2010 [this issue]).
The recolonization of wildlife at Kasatochi will influence, in turn, the hereafter pace and pattern of recovery and ecological succession of the greater terrestrial ecosystem on the isle (Crissafulli et al., 2005). Much of the surviving biota, or biological legacy, is comprised of marine birds, which are constructive vectors for transport of marine-derived nutrients (Stempniewicz, 1990; Maron et al., 2006) and plant cloth (Magnusson and Magnusson, 2000) to the terrestrial organisation. Therefore, seabirds can strongly bear upon the other land-based communities effectually their colonies (Petersen, 2009; Sigurdsson and Magnusson, 2009) and, thus, the recovery of convenance seabird colonies at Kasatochi could accelerate and shape the recovery of other isle biota.
Source: https://www.tandfonline.com/doi/full/10.1657/1938-4246-42.3.306
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