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At least 1,153 records · Page 64Linked to original sources
USGS2022

The future of coastal monitoring through satellite remote sensing

Satellite remote sensing is transforming coastal science from a “data-poor” field into a “data-rich” field. Sandy beaches are dynamic landscapes that change in response to long-term pressures, short-term pulses, and anthropogenic interventions. Until recently, the rate and breadth of beach change have outpaced our ability to monitor those changes, due to the spatiotemporal limitations of our observational capacity. Over the past several decades, only a handful of beaches worldwide have been regularly monitored with accurate yet expensive in situ surveys. The long-term coastal-change data of these few well-monitored beaches have led to in-depth understanding of many site-specific coastal processes. However, because the best-monitored beaches are not representative of all beaches, much remains unknown about the processes and fate of the other >99% of unmonitored beaches worldwide. The fleet of Earth-observing satellites has enabled multiscale monitoring of beaches, for the very first time, by providing imagery with global coverage and up to daily frequency. The long-standing and ever-expanding archive of satellite imagery will enable coastal scientists to investigate coastal change at sites vulnerable to future sea-level rise, that is, (almost) everywhere. In the past decade, our capability to observe coastal change from space has grown substantially with computing and algorithmic power. Yet, further advances are needed in automating monitoring using machine learning, deep learning, and computer vision to fully leverage this massive treasure trove of data. Extensive monitoring and investigation of the causes and effects of coastal change at the requisite spatiotemporal scales will provide coastal managers with additional, valuable information to evaluate problems and solutions, addressing the potential for widespread beach loss due to accelerated sea-level rise, development, and reduced sediment supply. Monitoring from Earth-observing satellites is currently the only means of providing seamless data with high spatiotemporal resolution at the global scale of the impending impacts of climate change on coastal systems.

Cambridge Prisms: Coastal Futures↗
USGS2004

Spring onset in the Sierra Nevada: When is snowmelt independent of elevation?

Short-term climate and weather systems can have a strong influence on mountain snowmelt, sometimes overwhelming the effects of elevation and aspect. Although most years exhibit a spring onset that starts first at lowest and moves to highest elevations, in spring 2002, flow in a variety of streams within the Tuolumne and Merced River basins of the southern Sierra Nevada all rose synchronously on 29 March. Flow in streams draining small high-altitude glacial subcatchments rose at the same time as that draining much larger basins gauged at lower altitudes, and streams from north- and south-facing cirques rose and fell together. Historical analysis demonstrates that 2002 was one among only 8 yr with such synchronous flow onsets during the past 87 yr, recognized by having simultaneous onsets of snowmelt at over 70% of snow pillow sites, having discharge in over 70% of monitored streams increase simultaneously, and having temperatures increase over 12°C within a 5-day period. Synchronous springs tend to begin with a low pressure trough over California during late winter, followed by the onset of a strong ridge and unusually warm temperatures. Synchronous springs are characterized by warmer than average winters and cooler than average March temperatures in California. In the most elevation-dependent, nonsynchronous years, periods of little or no storm activity, with warmer than average March temperatures, precede the onset of spring snowmelt, allowing elevation and aspect to influence snowmelt as spring arrives gradually.

Sierra Nevada↗
USGS2021

A Next Generation Lunar Orbiter mission

The Moon is the scientific foundation for our knowledge of the early evolution and impact history of the terrestrial planets. Over the last decades the lunar science community has made significant progress in addressing key lunar science and exploration goals, while defining many new high-priority scientific questions regarding the formation and evolution of the Moon. On a broad scale, the last Planetary Decadal Survey defined three scientific objectives to guide studies of the inner planets and Moon. These objectives address the origins and diversity of terrestrial planets, the evolution of life on terrestrial planets, and climate processes on Earth-like planets [1]. Many of these objectives carry forward into exploration goals of a renewed lunar human exploration program, and urgently addressing these objectives will enable the rapid development of exploration plans. A large (Flagship or New Frontiers class) Next Generation Lunar Orbiter (NGLO) mission would address the last Planetary Decadal Survey objective of understanding the origin and diversity of terrestrial planets by studying the geochemistry and geology of the Moon at an unparalleled resolution compared to other lunar mission datasets. Also, NGLO would address the objective of studying the evolution of life on terrestrial planets by furthering knowledge about the composition and distribution of volatile elements on the lunar surface and better characterizing the past and present-day impact rates in the inner Solar System in order to better understand the original delivery of water to Earth. Key exploration goals, including identifying the nature and distribution of lunar volatiles (i.e., water, ice), mapping and characterizing potentially valuable lunar resources, and establishing a human presence on the Moon, also would be addressed by NGLO.

Bulletin of the AAS↗
USGS2017

Glacierized headwater streams as aquifer recharge corridors, subarctic Alaska

Arctic river discharge has increased in recent decades although sources and mechanisms remain debated. Abundant literature documents permafrost thaw and mountain glacier shrinkage over the past decades. Here we link glacier runoff to aquifer recharge via a losing headwater stream in subarctic Interior Alaska. Field measurements in Jarvis Creek (634 km 2 ), a subbasin of the Tanana and Yukon Rivers, show glacier meltwater runoff as a large component (15–28%) of total annual streamflow despite low glacier cover (3%). About half of annual headwater streamflow is lost to the aquifer (38 to 56%). The estimated long-term change in glacier-derived aquifer recharge exceeds the observed increase in Tanana River base flow. Our findings suggest a linkage between glacier wastage, aquifer recharge along the headwater stream corridor, and lowland winter discharge. Accordingly, glacierized headwater streambeds may serve as major aquifer recharge zones in semiarid climates and therefore contributing to year-round base flow of lowland rivers.

Alaska↗
USGS2012

Glacier variability in the conterminous United States during the twentieth century

Glaciers of the conterminous United States have been receding for the past century. Since 1900 the recession has varied from a 24 % loss in area (Mt. Rainier, Washington) to a 66 % loss in the Lewis Range of Montana. The rates of retreat are generally similar with a rapid loss in the early decades of the 20th century, slowing in the 1950s–1970s, and a resumption of rapid retreat starting in the 1990s. Decadal estimates of changes in glacier area for a subset of 31 glaciers from 1900 to 2000 are used to test a snow water equivalent model that is subsequently employed to examine the effects of temperature and precipitation variability on annual glacier area changes for these glaciers. Model results indicate that both winter precipitation and winter temperature have been important climatic factors affecting the variability of glacier variability during the 20th Century. Most of the glaciers analyzed appear to be more sensitive to temperature variability than to precipitation variability. However, precipitation variability is important, especially for high elevation glaciers. Additionally, glaciers with areas greater than 1 km 2 are highly sensitive to variability in temperature.

Climate Change↗
USGS2022

Wetlands under global change

Wetlands are among the ecosystem types most threatened by global change, including both climate change and other anthropogenic factors such as sea level rise, urban development, deforestation, agricultural land use, drainage, levees, tidal flow restrictions, pollution, eutrophication, and fires. Wetlands not only store disproportionate amounts of carbon compared to other terrestrial ecosystems, but they lie at the terrestrial-aquatic interface crucial to understanding landscape and global scale biogeochemical cycles. In this chapter, we focus on the major global change factors affecting wetlands and the responses of different wetland types to those global change factors. Special attention is given to direct responses to increasing atmospheric carbon dioxide levels. Because of their hydrological connections and placement at the terrestrial-aquatic interface, the conservation of wetlands involves accounting for uncertainties related to interacting stressors. While the past decades have seen many important experimental and observational studies of wetland responses to global change factors, large uncertainties remain, especially within tropical regions where even the basic extent of wetland ecosystems is not well documented.

Book chapter↗
USGS2014

The Pacific Islands Climate Science Center five-year science agenda, 2014-2018

From the heights of Mauna Kea on Hawaiʻi Island to the depths of the Mariana Trench, from densely populated cities to sparse rural indigenous communities and uninhabited sandy atolls, the Pacific region encompasses diverse associations of peoples and places that are directly affected by changes to the atmosphere, ocean, and land. The peoples of the Pacific are among the first to observe and experience the effects of global climatic changes. Because the Pacific region is predominantly composed of vast ocean expanses punctuated only by small, isolated emergent islands and atolls, marine processes are critical factors in the region’s climate systems, and their impacts occur here to a greater degree than in continental regions. Rates of sea-level rise in the region during the modern altimetry period exceed the global rate, with the highest increases occurring in the western North Pacific (Cazenave and Llovel, 2010; Nerem and others, 2010; Timmermann and others, 2010). The ocean has also warmed during this period. Since the 1970s, sea-surface temperature has increased at a rate of 0.13 to 0.41 °F (0.07 to 0.23 °C) per decade, depending on the location (Keener and others, 2012a). Ocean chemistry has changed during this period as well, with surface pH having dropped by 0.1 pH units (Feely and others, 2009; Doney and others, 2012). Over the past century, air temperature has increased throughout the Pacific region. In Hawaiʻi, average temperatures increased by 0.08 °F per decade during the period 1919 to 2006, and in recent years, the rate of increase has been accelerating, particularly at high elevations (Giambelluca and others, 2008). In the western North Pacific, temperatures also increased over the past 60 years (Lander and Guard, 2003; Lander, 2004; Lander and Khosrowpanah, 2004; Kruk and others, 2013), with a concurrent warming trend in the central South Pacific since the 1950s (Australian Bureau of Meteorology and CSIRO, 2011).

Hawai'i↗
USGS2007

Hydrology of Polk County, Florida

Local water managers usually rely on information produced at the State and regional scale to make water-resource management decisions. Current assessments of hydrologic and water-quality conditions in Polk County, Florida, commonly end at the boundaries of two water management districts (South Florida Water Management District and the Southwest Florida Water Management District), which makes it difficult for managers to determine conditions throughout the county. The last comprehensive water-resources assessment of Polk County was published almost 40 years ago. To address the need for current countywide information, the U.S. Geological Survey began a 3?-year study in 2002 to update information about hydrologic and water-quality conditions in Polk County and identify changes that have occurred. Ground-water use in Polk County has decreased substantially since 1965. In 1965, total ground-water withdrawals in the county were about 350 million gallons per day. In 2002, withdrawals totaled about 285 million gallons per day, of which nearly 95 percent was from the Floridan aquifer system. Water-conservation practices mainly related to the phosphate-mining industry as well as the decrease in the number of mines in operation in Polk County have reduced total water use by about 65 million gallons per day since 1965. Polk County is underlain by three principal hydrogeologic units. The uppermost water-bearing unit is the surficial aquifer system, which is unconfined and composed primarily of clastic deposits. The surficial aquifer system is underlain by the intermediate confining unit, which grades into the intermediate aquifer system and consists of up to two water-bearing zones composed of interbedded clastic and carbonate rocks. The lowermost hydrogeologic unit is the Floridan aquifer system. The Floridan aquifer system, a thick sequence of permeable limestone and dolostone, consists of the Upper Floridan aquifer, a middle semiconfining unit, a middle confining unit, and the Lower Floridan aquifer. The Upper Floridan aquifer provides most of the water required to meet demand in Polk County. Data from about 300 geophysical and geologic logs were used to construct hydrogeologic maps showing the tops and thicknesses of the aquifers and confining units within Polk County. Thickness of the surficial aquifer system ranges from several feet thick or less in the extreme northwestern part of the county and along parts of the Peace River south of Bartow to more than 200 feet along the southern part of the Lake Wales Ridge in eastern Polk County. Thickness of the intermediate aquifer system/intermediate confining unit is highly variable throughout the county because of past erosional processes and sinkhole formation. Thickness of the unit ranges from less than 25 feet in the extreme northwestern part of the county to more than 300 feet in southwestern Polk County. The altitude of the top of the Upper Floridan aquifer in the county ranges from about 50 feet above National Geodetic Vertical Datum of 1929 (NGVD 29) in the northwestern part to more than 250 feet below NGVD 29 in the southern part. Water levels in the Upper Floridan aquifer fluctuate seasonally, increasing during the wet season (June through September) and decreasing during the rest of the year. Water levels in the Upper Floridan aquifer also can change from year to year, depending on such factors as pumpage and climatic variations. In the southwestern part of the county, fluctuations in water use related to phosphate mining have had a major impact on ground-water levels. Hydrographs of selected wells in southwestern Polk County show a general decline in water levels that ended in the mid-1970s. This water-level decline coincides with an increase in water use associated with phosphate mining. A substantial increase in water levels that began in the mid-1970s coincides with a period of decreasing water use in the county. Despite reductions in water use since 1970, howev

Scientific Investigations Report↗
USGS2020

Quantitative paleoflood hydrology

This chapter reviews the paleohydrologic techniques and approaches used to reconstruct the magnitude and frequency of past floods using geological evidence. Quantitative paleoflood hydrology typically leads to two phases of analysis: (1) documentation and assessment of flood physical evidence (paleostage indicators), and (2) relating identified flood evidence to flood discharge, based on hydraulic calculations. Most paleoflood studies rely on stratigraphic sequences of fine-grained flood deposits found in slack-water and eddy environments in bedrock rivers to enable the estimates of paleodischarges for floods of past few centuries or millennia. Geochronology, commonly based on techniques such as optically stimulated luminescence (OSL) and radiocarbon, enable paleoflood age estimates. Such paleoflood discharge and age information can vastly improve flood frequency estimates, particularly for large and rare floods for which quantile estimates are typically poorly constrained by short historical records. The inclusion of such physical evidence of flooding into flood frequency assessments has been aided by new techniques of frequency analysis that can efficiently employ such data. Consequently, paleoflood analysis is supporting probability risk management of critical infrastructure such as nuclear facilities, dams, or bridges. Paleoflood studies also support understanding of the recurrence of geomorphically effective flows and assessment of non-stationarity in the frequency of large floods due to climate, land-use, or other environmental changes.

Llobregat River↗
USGS2005

The role of abiotic conditions in shaping the long-term patterns of a high-elevation Argentine ant invasion

Analysis of long-term patterns of invasion can reveal the importance of abiotic factors in influencing invasion dynamics, and can help predict future patterns of spread. In the case of the invasive Argentine ant (Linepithema humile), most prior studies have investigated this species' limitations in hot and dry climates. However, spatial and temporal patterns of spread involving two ant populations over the course of 30 years at a high elevation site in Hawaii suggest that cold and wet conditions have influenced both the ant's distribution and its rate of invasion. In Haleakala National Park on Maui, we found that a population invading at lower elevation is limited by increasing rainfall and presumably by associated decreasing temperatures. A second, higher elevation population has spread outward in all directions, but rates of spread in different directions appear to have been strongly influenced by differences in elevation and temperature. Patterns of foraging activity were strongly tied to soil temperatures, supporting the hypothesis that variation in temperature can influence rates of spread. Based on past patterns of spread, we predicted a total potential range that covers nearly 50% of the park and 75% of the park's subalpine habitats. We compared this rough estimate with point predictions derived from a degree-day model for Argentine ant colony reproduction, and found that the two independent predictions match closely when soil temperatures are used in the model. The cold, wet conditions that have influenced Argentine ant invasion at this site are likely to be influential at other locations in this species' current and future worldwide distribution.

Hawaii↗
USGS2011

Simulation of groundwater flow in a volatile organic compound-contaminated area near Bethpage, Nassau County, New York: A discussion of modeling considerations

The 2010 Bethpage groundwater-flow model (ARCADIS, 2010) was based on a steady state assumption. Although it is widely acknowledged that significant water-level changes have occurred in the past, the reviewed model does not represent changing water levels. The steady state approach limits the effectiveness of the following: 1. identification of sources of contamination, 2. analysis of model accuracy, 3. model calibration, and 4. simulations of future scenarios. Future plume movement was simulated in an incomplete manner through an unchanging groundwater-flow field. Available time-series information on temporal variation of factors affecting groundwater-flow dynamics includes: 1. public-supply pumping, 2. groundwater discharges from systems remediating volatile organic compound (VOC) plumes, 3. recharge and precipitation rates, and 4. water levels and streamflows. Transient phenomena that might be useful in future hypothetical simulations include pumping variations, redirection of containment-system waters for industrial use, and climate-change scenarios. Public-domain computer programs, U.S. Geological Survey guidance reports on transient-state calibration and uncertainty methods (Doherty and Hunt, 2010), and additional local and regional datasets are available to provide additional confidence in model evaluations and allow better evaluation of their limitations.

New York↗
USGS2024

Limited preservation of strike-slip surface displacement in the geomorphic record

Offset geomorphic markers are commonly used to interpret slip history of strike-slip faults and have played an important role in forming earthquake recurrence models. These data sets are typically analyzed using cumulative probability methods to interpret average amounts of slip in past earthquakes. However, interpretation of the geomorphic record to infer surface slip history is complicated by slip variability, measurement uncertainty, and modification of offset features in the landscape. To investigate how well geomorphic data record surface slip, we use offset measurements from recent strike-slip surface ruptures ( n = 39), faults with geomorphic evidence of multiple strike-slip earthquakes ( n = 29), and synthetic slip distributions with added noise ( n > 10,000) to examine the constraints of the geomorphic record and the underlying assumptions of the cumulative offset probability distribution analysis method. We find that the geomorphic record is unlikely to resolve more than two paleo-slip distributions, except in specific cases with low slip variability, high slip-per-event, and semiarid climate. In cases where site-specific conditions allow for interpretation of more than two earthquakes, lateral extrapolation along a fault is not straightforward because on-fault displacement and distributed deformation may be spatially variable in each earthquake. We also find that average slip in modern earthquakes is adequately recovered by probability methods, but the reported prevalence of strike-slip faults with characteristic slip history is not supported by geomorphic data. We also propose updated methods to interpret slip history and construct uncertainty bounds for paleo-slip distributions.

Journal of Geophysical Research: Solid Earth↗
USGS2001

Biomes of western North America at 18,000, 6000 and 0 14C yr BP reconstructed from pollen and packrat midden data

A new compilation of pollen and packrat midden data from western North America provides a refined reconstruction of the composition and distribution of biomes in western North America for today and for 6000 and 18,000 radiocarbon years before present (14C yr BP). Modern biomes in western North America are adequately portrayed by pollen assemblages from lakes and bogs. Forest biomes in western North America share many taxa in their pollen spectra and it can be difficult to discriminate among these biomes. Plant macrofossils from packrat middens provide reliable identification of modern biomes from arid and semiarid regions, and this may also be true in similar environments in other parts of the world. However, a weighting factor for trees and shrubs must be used to reliably reconstruct modern biomes from plant macrofossils. A new biome, open conifer woodland, which includes eurythermic conifers and steppe plants, was defined to categorize much of the current and past vegetation of the semiarid interior of western North America. At 6000 14C yr BP, the forest biomes of the coastal Pacific North-west and the desert biomes of the South-west were in near-modern positions. Biomes in the interior Pacific North-west differed from those of today in that taiga prevailed in modern cool/cold mixed forests. Steppe was present in areas occupied today by open conifer woodland in the northern Great Basin, while in the central and southern Rocky Mountains forests grew where steppe grows today. During the mid-Holocene, cool conifer forests were expanded in the Rocky Mountains (relative to today) but contracted in the Sierra Nevada. These differences from the forests of today imply different climatic histories in these two regions between 6000 14C yr BP and today. At 18,000 14C yr BP, deserts were absent from the South-west and the coverage of open conifer woodland was greatly expanded relative to today. Steppe and tundra were present in much of the region now covered by forests in the Pacific North-west.

Journal of Biogeography↗
USGS2018

Iterative near-term ecological forecasting: Needs, opportunities, and challenges

Two foundational questions about sustainability are “How are ecosystems and the services they provide going to change in the future?” and “How do human decisions affect these trajectories?” Answering these questions requires an ability to forecast ecological processes. Unfortunately, most ecological forecasts focus on centennial-scale climate responses, therefore neither meeting the needs of near-term (daily to decadal) environmental decision-making nor allowing comparison of specific, quantitative predictions to new observational data, one of the strongest tests of scientific theory. Near-term forecasts provide the opportunity to iteratively cycle between performing analyses and updating predictions in light of new evidence. This iterative process of gaining feedback, building experience, and correcting models and methods is critical for improving forecasts. Iterative, near-term forecasting will accelerate ecological research, make it more relevant to society, and inform sustainable decision-making under high uncertainty and adaptive management. Here, we identify the immediate scientific and societal needs, opportunities, and challenges for iterative near-term ecological forecasting. Over the past decade, data volume, variety, and accessibility have greatly increased, but challenges remain in interoperability, latency, and uncertainty quantification. Similarly, ecologists have made considerable advances in applying computational, informatic, and statistical methods, but opportunities exist for improving forecast-specific theory, methods, and cyberinfrastructure. Effective forecasting will also require changes in scientific training, culture, and institutions. The need to start forecasting is now; the time for making ecology more predictive is here, and learning by doing is the fastest route to drive the science forward.

Proceedings of the National Academy of Sciences of↗
USGS2014

Temporal variability of carbon and nutrient burial, sediment accretion, and mass accumulation over the past century in a carbonate platform mangrove forest of the Florida Everglades.

The objective of this research was to measure temporal variability in accretion and mass sedimentation rates (including organic carbon (OC), total nitrogen (TN), and total phosphorous (TP)) from the past century in a mangrove forest on the Shark River in Everglades National Park, USA. The 210 Pb Constant Rate of Supply model was applied to six soil cores to calculate annual rates over the most recent 10, 50, and 100 year time spans. Our results show that rates integrated over longer timeframes are lower than those for shorter, recent periods of observation. Additionally, the substantial spatial variability between cores over the 10 year period is diminished over the 100 year record, raising two important implications. First, a multiple-decade assessment of soil accretion and OC burial provides a more conservative estimate and is likely to be most relevant for forecasting these rates relative to long-term processes of sea level rise and climate change mitigation. Second, a small number of sampling locations are better able to account for spatial variability over the longer periods than for the shorter periods. The site average 100 year OC burial rate, 123 ± 19 (standard deviation) g m -2 yr -1 , is low compared with global mangrove values. High TN and TP burial rates in recent decades may lead to increased soil carbon remineralization, contributing to the low carbon burial rates. Finally, the strong correlation between OC burial and accretion across this site signals the substantial contribution of OC to soil building in addition to the ecosystem service of CO 2 sequestration.

Florida↗
USGS2014

Trends in conservation research and management in Hawai‘i over the past 20 years

Hawaiʻi, an archipelago of the most isolated inhabited islands on the planet, faces unique and extreme challenges to its biodiversity. We examined how the conservation community has responded to these challenges and how the responses have changed over time, using twenty years of abstracts from the Hawaiʻi Conservation Conference, a yearly gathering of the majority of scientists, managers and the public in Hawaiʻi. Of the 2145 abstracts considered, 60% percent reported research results; 40.0% reported information on conservation and resource management programmes and institutions (i.e., non-research abstracts). Initially, applied research abstracts predominated, but in recent years the number of basic research abstracts has become similar. Across taxonomic groups, terrestrial plants, mammals and birds were the dominant research subjects, fish, algae and fungi were noticeably less studied relative to their diversity in Hawaiʻi. Bird and fish species studied were mostly native; research on most other taxa was evenly divided between native and non-native species. Topics have oscillated in frequency over the years, but there have been no dramatic trends, with the exception of climate change and Local Ecological Knowledge (LEK). Although there is an increasing trend in LEK and cross-disciplinary studies, the number of related abstracts have remained uncommon through the period, accounting for less than 5.0% of total research abstracts analyzed. Our results offer an oportunity for the conservation community to take a closer look at reported effort to better address key conservation questions for Hawaiʻi.

Hawaiʻi↗
USGS2009

Climatic and limnologic setting of Bear Lake, Utah and Idaho

Bear Lake is a large alkaline lake on a high plateau on the Utah-Idaho border. The Bear River was partly diverted into the lake in the early twentieth century so that Bear Lake could serve as a reservoir to supply water for hydropower and irrigation downstream, which continues today. The northern Rocky Mountain region is within the belt of the strongest of the westerly winds that transport moisture during the winter and spring over coastal mountain ranges and into the Great Basin and Rocky Mountains. As a result of this dominant winter precipitation pattern, most of the water entering the lake is from snowmelt, but with net evaporation. The dominant solutes in the lake water are Ca 2+ , Mg 2+ , and HCO 3 2- , derived from Paleozoic carbonate rocks in the Bear River Range west of the lake. The lake is saturated with calcite, aragonite, and dolomite at all depths, and produces vast amounts of carbonate minerals. The chemistry of the lake has changed considerably over the past 100 years as a result of the diversion of Bear River. The net effect of the diversion was to dilute the lake water, especially the Mg 2+ concentration. Bear Lake is oligotrophic and coprecipitation of phosphate with CaCO 3 helps to keep productivity low. However, algal growth is colimited by nitrogen availability. Phytoplankton densities are low, with a mean summer chlorophyll a concentration of 0.4 mg L -1 . Phytoplankton are dominated by diatoms, but they have not been studied extensively (but see Moser and Kimball, this volume). Zooplankton densities usually are low (<10 L -1 ) and highly seasonal, dominated by calanoid copepods and cladocera. Benthic invertebrate densities are extremely low; chironomid larvae are dominant at depths <30 m, and are partially replaced with ostracodes and oligochaetes in deeper water. The ostracode species in water depths >10 m are all endemic. Bear Lake has 13 species of fi sh, four of which are endemic. Copyright ?? 2009 The Geological Society of America.

Special Paper of the Geological Society of America↗
USGS2020

Loss of coastal islands along Florida’s Big Bend region: Implications for breeding American oystercatchers

Many coastal-dependent species have undergone large-scale population declines due to impacts from habitat loss, including American oystercatchers ( Haematopus palliatus ). Islands along the Big Bend region of Florida’s Gulf Coast provide important nesting habitat for oystercatchers, but reproductive success here is low and habitat degradation and loss are a major concern. To determine rates and characteristics of habitat loss, we quantified changes in island sizes within two major breeding areas of the Big Bend: the Barge Canal spoil islands and natural islands at Cedar Key. We digitized aerial photographs from the past ~ 40 years, measured area and shoreline retreat of nesting islands, and identified trends over time by fitting linear mixed effects models. The total area of the ten Barge Canal spoil islands decreased by 55% between 1979 and 2016. At Cedar Key, the total area of the six islands measured decreased by 39% between 1974 and 2016, 85% of which occurred after 1995, indicating an increase in erosion rates correlated with oyster reef declines. Changes in available nesting habitat varied between the Barge Canal and Cedar Key islands due to differences in physical attributes; however, all islands significantly decreased in size over time. Given the long life and high site fidelity of American oystercatchers, these islands may currently be acting as an ecological trap for this species. Climate change, sea-level rise, and loss of oyster reefs are likely to continue to drive oystercatcher habitat loss throughout their range; thus, creation and restoration of oyster reefs and nesting islands will become increasingly important.

Florida↗