Santa Rosa Island Research Articles

An Overview of Cadmium, Chromium, and Lead Content in Bivalves Consumed by the Community of Santa Rosa Island (Ecuador) and Its Health Risk Assessment

Santa Rosa Island community members derive their income and livelihoods from bio-aquatic resources, principally bivalves of the genus Anadara, both for subsistence use and commercial purposes. Bivalve mollusks have a sedentary lifestyle and feed by filtering water, meaning they absorb all surrounding substances, including harmful elements like toxic metals. This study aimed to analyze different-sized samples of Anadara tuberculosa and Anadara similis, sediment, and Rhizophora mangle leaves to determine their total amount of cadmium, lead, and chromium as a first approach to the evaluation of the health risk related to the consumption of bivalves. For both species from four sampling sites, the results revealed metal concentrations in the bivalves between 0.211 and 0.948 mg·kg-1, 0.038 and 0.730 mg·kg-1, and 0.067 and 0.923 mg·kg-1 for Cd, Cr, and Pb, respectively. The calculated potential risk (>1) for cadmium, considering all body weights, showed a high health risk for consumers. In the case of lead, the results showed a high health risk in children. There was no risk found for chromium. For sediments, the mean values were 2.14, 29.99, and 12.37 mg·kg-1 and for the Rhizophora mangle leaves were 2.23, 4.22, and 3.35 mg·kg-1 for Cd, Cr, and Pb, respectively. These results did not show a relation with the metal content in bivalves.

An overview of cadmium, chromium, and lead content in bivalves consumed by the community of Santa Rosa Island (Ecuador) and its health risk assessment

Santa Rosa Island community members derive their income and livelihoods from bio-aquatic resources, principally bivalves of the genus Anadara, both for subsistence use and commercial purposes. Bivalve mollusks have a sedentary lifestyle and feed by filtering water, meaning they absorb all surrounding substances, including harmful elements like toxic metals. This study aimed to analyze different-sized samples of Anadara tuberculosa and Anadara similis, sediment, and Rhizophora mangle leaves to determine their total amount of cadmium, lead, and chromium as a first approach to the evaluation of the health risk related to the consumption of bivalves. For both species from four sampling sites, the results revealed metal concentrations in the bivalves between 0.211 and 0.948 mg·kg-1, 0.038 and 0.730 mg·kg-1, and 0.067 and 0.923 mg·kg-1 for Cd, Cr, and Pb, respectively. The calculated potential risk (>1) for cadmium, considering all body weights, showed a high health risk for consumers. In the case of lead, the results showed a high health risk in children. There was no risk found for chromium. For sediments, the mean values were 2.14, 29.99, and 12.37 mg·kg-1 and for the Rhizophora mangle leaves were 2.23, 4.22, and 3.35 mg·kg-1 for Cd, Cr, and Pb, respectively. These results did not show a relation with the metal content in bivalves.

Translocation with targeted vaccination is the most effective strategy to protect an island endemic bird threatened by West Nile virus

AbstractAimInvasive pathogens are a growing conservation challenge and often occur in tandem with rapid environmental transformation, such as climate change, drought and habitat loss. Climate change appears to have facilitated the spread of West Nile virus (WNV), a cause of widespread avian mortality. WNV is considered the primary threat to island scrub‐jays (Aphelocoma insularis), endemic to Santa Cruz Island, California. Two approaches have been proposed to safeguard island scrub‐jays: (a) vaccination and (b) conservation translocation to re‐establish a second population on neighbouring Santa Rosa Island, hypothesized to have a lower risk of WNV. These alternatives operate at regional scales but exemplify global concerns with strategic implications for conservation biogeography and climate adaptation.LocationCalifornia Channel Islands, USA.MethodsWe compared the efficacy of vaccination and translocation strategies at minimizing 25‐year quasi‐extinction risk for island scrub‐jays using a stochastic population model.ResultsUnder current WNV‐free conditions, the predicted quasi‐extinction risk for island scrub‐jays was low (~0%) but increased to ≥22% with simulated WNV outbreaks. Vaccinating ≥60 individuals reduced risk to <5%, but risk doubled if population size declined and further increased with more frequent droughts. Translocation performed best if Santa Rosa Island had a large starting population size and habitat extent, and, more importantly, a low risk of WNV establishment; if Santa Rosa Island was inhospitable to WNV, quasi‐extinction risk dropped to near zero.Main conclusionsTranslocation with targeted vaccination during high‐risk conditions was the most effective strategy to protect island scrub‐jays from West Nile virus. Although vaccination often outperformed translocation, only scenarios that included a Santa Rosa population and vaccinations achieved acceptably low species‐wide extinction risk across all potential future conditions. Our analysis informs strategies to improve the long‐term viability of the most range‐restricted bird species in the continental United States and provides a model for assessing conservation‐translocation proposals for other species and threats.

Fishing, Subsistence Change, and Foraging Strategies on Western Santa Rosa Island, California

Shifting from shellfish collecting to fishing as a primary coastal foraging strategy can allow hunter-gatherers to obtain more food and settle in larger populations. On California's northern Channel Islands (NCI), after the development of the single-piece shell fishhook around 2500 cal BP, diet expanded from primarily shellfish to include nearshore fishes in greater numbers. During the Medieval Climatic Anomaly (1150–600 cal BP), settlement on the islands condensed to a small number of large coastal villages with high population densities supported largely by nearshore fish species including rockfishes, surfperches, and señoritas. Faunal data from five sites on western Santa Rosa Island (CA-SRI-15, -31, -97, -313, and -333) demonstrate an increase in nearshore fishing through time. We argue that demographic changes that occurred on the northern Channel Islands were accompanied by changes in subsistence strategies that were related in part to risk of failure when attempting to acquire different resources. As population density increased, the low-risk strategy of shellfish harvesting declined in relative importance as a higher-risk strategy of nearshore fishing increased. While multiple simultaneous subsistence strategies are frequently noted among individual hunter-gatherer communities in the ethnographic record, this study provides a framework to observe similar patterns in the archaeological record.

Late Pleistocene estuaries, palaeoecology and humans on North America's Pacific Coast

Abstract

New Species of Flightless Cymatodera Gray, 1832 (Coleoptera: Cleridae: Tillinae) from the California Channel Islands

Two species of flightless Cymatodera Gray are described from the California Channel Islands: Cymatodera insularis Rifkind, new species, from Santa Catalina Island and San Clemente Island; and Cymatodera caterinoi Rifkind and Burke, new species, from Santa Rosa Island, Santa Cruz Island, and Anacapa Island. The new species are compared with Cymatodera vandykei Schaeffer and Cymatodera angustata Spinola, similar flightless species from the California mainland. The origins of Channel Island insect endemism are briefly discussed.

Fluvial sedimentary history of Arlington Canyon, Channel Islands National Park, California

ABSTRACTArlington Canyon, in the northwest part of Santa Rosa Island, Channel Islands National Park, California, has been the setting for important scientific discoveries over the past half century, including the oldest human remains in North America, several vertebrate fossil sites, and purported evidence of a catastrophic extinction event at the end of the Pleistocene. The canyon is filled with alluvial sediments that date to between 16.4 and 1.1 ka (thousands of calibrated years before present), representing accumulation that occurred primarily in response to rising sea levels during the late Pleistocene and Holocene. The deposits are laterally discontinuous, exhibit a high degree of sedimentary complexity, and contain evidence of past climates and environments, including fossil bones, burned plant macrofossils, and invertebrate microfossils. Here, we show that it is critical to view the observations, data, and conclusions of scientific studies conducted in the canyon within this larger context so that localized facets of the spatially and temporally extensive alluvial deposits are not misinterpreted or misrepresented. By improving the baseline understanding of processes and drivers of sediment accumulation in Arlington Canyon, we hope to offer a solid foundation and better underpinning for future archeological, paleontological, and geochemical studies here and throughout the northern Channel Islands. Published 2019. This article is a U.S. Government work and is in the public domain in the USA.

A Paleocoastal Site Complex from Santarosae Island, California

ABSTRACTFour recently identified sites from eastern Santa Rosa Island contain flaked-stone artifacts diagnostic of Paleocoastal occupations between ∼13,000 and 8000 calendar years ago. The largest site (CA-SRI-997/H) contains two discrete loci that have been the subject of recent testing and data recovery excavations reported elsewhere. Three smaller, nearby sites are lithic scatters that produced Paleocoastal stemmed points and/or crescents. When occupied, the sites were located adjacent to a perennial stream ∼3–5 km from the shore of a large embayment named Crescent Bay, which persisted until ∼9000 ± 500 calendar years ago. The Crescent Bay area contained freshwater, estuarine, and marine habitats – as well as terrestrial plant communities rich in geophytes and other edible plant foods. Understanding Paleocoastal settlement patterns and the paleogeography of the area enriches our understanding of early human lifeways on the Channel Islands and may help predict the location of Paleocoastal sites on the submerged, offshore landscapes.

Early Red Abalone Shell Middens, Human Subsistence, and Environmental Change on California's Northern Channel Islands

Red abalone (Haliots rufescens) shell middens, a distinctive site type on the California Coast dating primarily to the Middle Holocene, provide important insight into human-environmental interactions and climatic and environmental change. Despite decades of research and debate about why red abalone middens formed and how they relate to past human behavior and environmental change, significant questions persist about the nature of these sites and how they relate to broader trends in human diet and land use. Here, we present the results of excavation at three red abalone middens on the northern Channel Islands. Two of these middens, CA-SRI-26 on Santa Rosa Island and CA-SMI-692 on San Miguel Island, are among the older reported red abalone middens, at roughly 8000–7300 cal BP, and help fill a significant temporal gap in our understanding of the initial period of intensive red abalone harvest. The third midden, CA-SMI-172, dates to ~6300 cal BP and fills a spatial gap on eastern San Miguel Island. When placed in the context of other Channel Island red abalone middens, our analysis demonstrates that people at some of the earliest red abalone middens harvested more red abalone and larger sized individuals than later in time. These data suggest that people likely placed predation pressure on red abalones across the red abalone midden period (8500–3500 cal BP) and that human activities worked in tandem with other environmental changes to influence the disappearance of the red abalone midden phenomenon ~3500 years ago.

Technological change and interior settlement on western Santa Rosa Island, California

We use data on site distributions, chronology, and artifact assemblages from a large, flat upland landscape on Santa Rosa Island to better understand the relationship between coastal and interior settlement patterns on California’s northern Channel Islands. This region, Pocket Field, was an important hub of occupation during the late Pleistocene/early Holocene (before 7550 cal BP) and throughout the late Holocene (3600–168 cal BP). A radiocarbon chronology for the region suggests that settlement patterns are consistent with what has been observed in coastal locations, with an increase in site density throughout the late Holocene. Groundstone is an important component of the late Holocene archaeological record, although it decreases in importance following the droughts of the Medieval Climatic Anomaly (MCA; 1150–600 cal BP). Olivella biplicata shell bead production at dense midden sites indicates that occupation of the region was not just for access to terrestrial resources. An increase in sites with projectile points during the MCA may reflect an increase in interpersonal violence and indicate that increasing territoriality that occurred on the coast may have extended into the island interior. Our study demonstrates that interior sites were integral components of island settlement and subsistence patterns, even when diet is heavily marine-oriented.

Shellfish, Geophytes, and Sedentism on Early Holocene Santa Rosa Island, Alta California, USA

Archaeobotanical remains recovered from a large ∼8000-year-old-shell midden (CA-SRI-666) on Santa Rosa Island provide the first ancient plant data from this large island, shedding light on ancient patterns of plant use, subsistence, and sedentism. Faunal data from shell midden samples retrieved from three site loci contain evidence for harvesting of rocky intertidal shellfish and estuarine clams and oysters from a paleo-estuary in the vicinity. CA-SRI-666 appears to have been an Early Holocene village site occupied year round. A key to the development of early sedentary societies on the island may have been geophytes, especially Brodiaea-type corms, which provided an abundant source of carbohydrates and calories that complemented marine resources rich in fat and whole animal proteins. Our data demonstrate the value of integrating paleobotanical and zooarchaeological data from island and coastal archaeological sites to help elucidate human social, cultural, and environmental dynamics, including sedentism.

Quantifying Surface Water on Santa Rosa Island, California, Following a Major Five-Year Drought

Although it is critical for survival of plants and animals, and for understanding prehistory of early humans, little work has been done on the stream hydrology of the California Channel Islands. In September 2014, August 2016, and October 2017, during the driest period of the year, park staff and volunteers mapped surface water on Santa Rosa Island, Channel Islands National Park, by walking drainages (2nd order and higher) and recording the location of surface water using consumer-grade Global Positioning System (GPS) units. In 2014, mappers hiked 293 km (182 miles) of stream channel in 19 major drainage basins and 7 lesser drainage basins. The hiking teams recorded 759 water features (pools and springs) and 67 km (42 miles) of surface water. The 2016 repeat mapping in Verde, Trancion, Arlington, and San Augustin canyons, the 4 wettest drainages in 2014, showed that surface water declined by 10.1%, 21.1%, and 34.2% for the first 3 canyons, respectively; surface water in San Augustin increased by 1.3% between 2014 and 2016. Repeat mapping in 2017 of Verde, Trancion, Arlington, San Augustin, and Water canyons showed an increase from 28.3% to 90.0% in surface water following an above-average rainfall year in 2016–2017. Results have important implications for plant and animal life that depend on water on Santa Rosa Island.

The Influence of Slope on Vegetation Recovery Following Nonnative Grazer Removal on Santa Rosa Island, California

Ecosystem restoration efforts have been ongoing on the Channel Islands of California since the 1980s. Although these island ecosystems evolved without ungulate grazers, large nonnative grazers, including sheep, cattle, feral pigs, deer, and elk, were present on the islands for over 160 years. Intensive grazing led to reductions in the extent of woody vegetation, increases in the area of grassland and bare ground, and widespread landsliding and gully erosion. This study focuses on Santa Rosa Island, the second largest (215.3 km2) island in Channel Islands National Park. After the park was created in 1980, the National Park Service progressively removed nonnative grazers to facilitate the restoration of native vegetation and the wildlife communities they support. We constructed a time series (1989 to 2015) of Landsat TM5 and Landsat 7 ETM+ images to evaluate large-scale and long-term vegetation change in response to grazer removal on Santa Rosa Island. We also evaluated the influence of slope percent, which can be an indicator of past grazing accessibility, on ecosystem recovery. Results indicate that removing nonnative grazers led to passive restoration of 42.1 km2 of scrub, chaparral, and woodland vegetation. In contrast, the area of grassland vegetation decreased by 31.2 km2 and bare ground decreased by 12.0 km2. The extent of scrub and woodland vegetation recovery was greater on gentle and moderate slopes compared to steep slopes, indicating that terrain does influence passive restoration. Despite changes in vegetation cover, 5.4 km2 has remained bare. Much of the bare ground is on ridgelines that were denuded down to the bedrock or regolith. Active restoration will be necessary on bare ridgelines, such as erosion control, fog capture, and oak woodland reforestation.

Regeneration and Expansion of Quercus tomentella (Island Oak) Groves on Santa Rosa Island

Quercus tomentella (island oak) is an endemic species that plays a key functional role in Channel Island ecosystems. Growing in groves on highland ridges, Q. tomentella captures fog and increases water inputs, stabilizes soils, and provides habitat for flora and fauna. This cloud forest system has been impacted by a long history of ranching, and restoration efforts are underway that include erosion control, leaf litter capture, fog capture, and reforestation. To inform retoration efforts, we explored tree regeneration and the potential for Q. tomentella grove expansion on Santa Rosa Island. We delineated current and historic groves at Black Mountain by comparing stand maps from 1989 and aerial photographs from 1994 and 2015. We evaluated regeneration in the outlying areas by recording the location, diameter at breast height, number of trunks, height class, percent crown mortality, nurse plant species (if present), and reproductive status for all 4355 outlying seedlings, saplings, and mature trees. We defined outliers as individuals that were 15 m outside of the canopy of island oak groves. There are 14 groves at Black Mountain, and grove size expanded by an average of 36.9% (SD 18.5%) between 1994 and 2015. Nurse plants correlated positively with outlier tree height and reduced percent crown mortality. This effect is potentially due to increased fog drip from nurse plant species such as Quercus pacifica (island scrub oak), Heteromeles arbutifolia (toyon), and Baccharis pilularis (coyote brush). These results indicate that Q. tomentella is regenerating and that nurse plants can serve as catalysts for ecosystem restoration.

Land Mollusks of the California Channel Islands: An Overview of Diversity, Populations, and Conservation Status

The land snails and slugs have the highest level of endemism among all major animal groups on the California Channel Islands, with nearly 75% of the native terrestrial species confined to one or more of the 8 islands. In spite of this endemism, and in spite of the rarity of some species, the snails and slugs are one of the most poorly known groups. We present the first comprehensive overview of the land mollusk fauna of the Channel Islands, along with the results of recent intensive inventory studies. Surveys on San Clemente Island have increased the number of land mollusk species known from that island by 50%, and a single survey trip to Santa Rosa Island more than doubled the number of species known on that island. More additions to the land snail and slug fauna are certain for the poorly surveyed northern Channel Islands. This new information has provided insight into trends in species diversity and biogeographic patterns, with marked differences in species composition between the northern and southern islands. Our surveys to date suggest a strong link between the recovery of native vegetation on the islands and the population status of land snails and slugs, with substantially larger numbers of native mollusks on those islands that have been free of nonnative mammals the longest. Survey work is continuing, but it is clear that some very rare endemic snails and slugs on the islands merit specific management attention.

The utility of an omni-directional photoelectronic sensor device to measure meso-scale variability in aeolian sediment transport activity

Abstract Electronic sensors (i.e., acoustic, piezoelectric, and photoelectric) have been utilized extensively and effectively in recent years for measuring aeolian transport intensity. The bulk of these studies, however, position the devices in stationary, fixed orientation during field experiments. These practices work fine for shorter, micro-scale field studies; yet, during longer experiments lasting months or even years, a fixed directional orientation is unrealistic due to shifts in wind direction. This issue has ultimately limited the use of electronic sensors for meso-scale aeolian research. In light of this constraint, this paper presents a device to measure aeolian transport activity across a 360-degree azimuthal range. The Rotating Wenglor Device (RWD) was deployed on Santa Rosa Island, Florida for a three-month field study. The data reveal that the prevailing transport activity did not align with the dominant wind direction. The implications of this finding can be further elucidated when analyzing our data using the Fryberger drift potential model. Our findings indicate that the traditional Fryberger method, constructed using our wind data, produced a resultant transport drift towards the northwest; however, the RWD illustrated a resultant transport direction towards the northeast and at a rate three times slower. These finding highlights a major benefit of the RWD as it would produce a more accurate measure of meso-scale transport activity and therefore dune development than models derived strictly from meteorological station data, such as the Fryberger method. An additional advantage of the RWD is that the device operates unattended for extended periods, yet can provide high-resolution data regarding micro-scale transport dynamics.

Hierarchical sensitivity analysis for simulating barrier island geomorphologic responses to future storms and sea-level rise

This paper presents a new application of an advanced hierarchical sensitivity analysis of a new climate model of barrier island geomorphological evolution. The implemented sensitivity analysis in this study integrates a hierarchical uncertainty framework with a variance-based global sensitivity analysis to decompose the different model input uncertainties. The analysis can provide quantitative and accurate measurements for the relative importance of uncertain model input factors while considering their dependence relationships. The climate model used in this research was the barrier island profile (BIP) model, which is a new computer code developed to simulate barrier island morphological evolution over periods ranging from years to decades under the impacts of accelerated future sea-level rise and long-term changes in the storm climate. In the application of the model, the BIP model was used to evaluate the responses of a series of barrier island cross-sections derived for Santa Rosa Island, Florida, to random storm events and five potential accelerated rates of sea-level rise projected over the next century. The uncertain model input factors thus include the scenario uncertainty caused by alternative future sea-level rise scenarios and the parametric uncertainties of random storm parameters and dune characteristics. The study results reveal that the occurrence of storms is the most important factor for the evolution of sand dunes on the barrier island and the impact of sea-level rise is essential to the morphological change of the island backshore environment. The analysis can provide helpful insights for coastal management and planning. This hierarchical sensitivity analysis is mathematically general and rigorous and can be applied to a wide range of climate models.

Erosion of Coastal Archaeological Sites on Santa Rosa Island, California

The damage and loss of coastal archaeological sites from shoreline transgression and other near-coastal processes is common around the world. It negatively impacts our ability to address important research questions including those about the colonization of the New World, which likely occurred along the Pacific Coast. Differences in geomorphic context, annual weather patterns, topography, vegetation, bedrock, and land-use history lead to distinct localized patterns of erosion even within small geographic regions. We assessed near-coastal erosion on Santa Rosa Island, California, by monitoring annual change at 16 controlled points on 11 archaeological sites from 2013 to 2017 and by comparing it to the local geomorphic context and annual weather patterns. Overall, erosion through this period was greatest on the northwest coast of the island, which is directly in the path of prevailing winds and most winter storms, and least on the more protected west and south coasts. The 2016–2017 winter was the rainiest and had the most annual erosion in general; however, erosion at sites along gulley walls was lowest that year. By monitoring annual erosion and weather and associating them with variations in erosional processes, we can better understand threats to valuable cultural resources and take appropriate steps for mitigating their losses and the loss of archaeological data.

Terminal Pleistocene–Holocene Avifauna of San Miguel and Santa Rosa Islands: Identifications of Previously Unidentified Avian Remains Recovered from Fossil Sites and Prehistoric Cave Deposits

We provide an update to the fossil avifauna of San Miguel and Santa Rosa Islands based on the identification of 3509 small bird bones recovered from fossil sites on Santa Rosa and from 3 archaeological-paleontological cave deposits and 20 fossil sites on San Miguel. This work adds 64 species to the fossil avian community of these 2 islands, increasing the previous total from 83 to 147 species, making this the richest Late Pleistocene–Holocene coastal avifaunal assemblage recorded for California. Of the 64 newly identified species, 62 are new additions to the Channel Islands fossil avifauna and 40 are new to the fossil avifauna of California. Twenty-two species were confirmed to have nested on San Miguel Island during the Holocene based on the identification of juvenile/immature bones. At least 4 land birds (Burrowing Owl [Athene cunicularia], Island Scrub-Jay [Aphelocoma insularis], Bewick's Wren [Thryomanes bewickii], and Spotted Towhee [Pipilo maculatus]) that nested prehistorically on San Miguel have disappeared from the modern record there. Island Scrub-Jay bones were identified from 3 fossil sites on San Miguel and 1 site on Santa Rosa, providing the first confirmation that this species lived on both islands during the Pleistocene and Holocene. Island Scrub-Jays disappeared from San Miguel Island sometime in the Late Holocene, but a small population may have lingered on Santa Rosa Island into historic times before dying out. Destruction of island scrub and woodland habitats following the introduction of livestock in the mid-19th century probably caused the extirpation of resident breeding populations of Bewick's Wren and Spotted Towhee from San Miguel Island and Island Scrub-Jay from Santa Rosa Island.

Marine Debris Trends: 30 Years of Change on Ventura County and Channel Island Beaches

The persistence of plastics in marine ecosystems and the physical hazards marine debris pose to wildlife have become issues of global concern. The Santa Barbara Channel is home to a number of important marine and coastal ecosystems, including the 5 islands of Channel Islands National Park, and has a variety of factors that influence marine debris accumulation. We examined the spatial variation of marine debris density and composition across the Santa Barbara Channel by quantifying marine debris on beaches of Santa Rosa and Santa Cruz Islands and the Ventura County mainland. Debris from surveyed beaches was cataloged, weighed, and measured to compare differences in island and mainland marine debris abundance, density, and composition. Derelict fishing gear accounted for a higher proportion of marine debris on island beaches compared to mainland beaches, and marine debris items on island beaches were significantly heavier compared to debris items on mainland beaches. The majority of debris on mainland beaches comprised smaller plastic fragments and single-use plastic items, and debris accumulation rates varied by season and location. Microplastics (plastic fibers and particles 25 mm) that were collected during marine debris cleanups. We compared our data from 2015 and 2016 with historical surveys performed from 1989 to 1994 to examine the temporal variation of marine debris on Santa Rosa Island. We found that there has been a significant increase in the amount of derelict fishing gear found on Santa Rosa Island over the past 27 years, which mirrors expansion of the California spiny lobster (Panulirus interruptus) fishery. This study highlights the importance of marine debris monitoring, as local changes in policy, fisheries, and consumer culture are reflected in accumulations of marine debris found on the California mainland and the uninhabited Channel Islands. Monitoring marine debris can provide insight into anthropogenic impacts and is a useful mechanism in monitoring the health of coastal and marine ecosystems.