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At least 1,585 records · Page 88Linked to original sources
USGS1999

Puerto Rico, humedales [Puerto Rico, wetlands]

La isla de Puerto Rico, localizada al noreste del Mar Caribe y sus islas principales, Vieques, Culebra e Isla de Mona, poseen humedales en abundancia . El clima subtropical, la lluvia abundante y las complejas formas topográficas y geológicas de estas islas dan origen a los humedales, que varían desde los raros e inusuales bosques cubiertos por nubes en las tierras altas, hasta los extensos manglares, yerbas marinas y arrecifes de coral a lo largo de las costas Norte y Sur. Sin embargo, los humedales en Puerto Rico han disminuido en los últimos siglos como resultado del aumento en el desarrollo agrícola, poblacional y turístico. Algunos tipos de humedales como los bosques de palo de pollo (Pterocarpus officinalis) se han reducido a sólo unos pocos remanentes (figura 1). Biológicamente hablando, los humedales de las islas están entre las áreas más productivas. Los humedales asociados con el bosque pluvial en las tierras altas del interior de Puerto Rico contienen varias plantas raras y especies de animales que no se encuentran en otras partes de la Isla. El agua de escorrentía proveniente de los humedales en las partes altas de la Isla proveen una fuente de agua que utilizan varias ciudades para abasto público. Los humedales costeros como los mangles, los colchones de yerbas marinas y los arrecifes de coral proveen áreas para la reproducción y crianza de varios peces, crustáceos y otras especies en la cadena alimenticia (López y otros, 1988). De esta manera, los humedales costeros contribuyen a la productividad biológica de las aguas llanas del mar alrededor de las islas . Los humedales también estabilizan las costas atrapando y reteniendo sedimentos no consolidados y amortiguan la acción de las olas y de las tormentas que tienen el potencial de causar daños en la zona. El valor de los humedales de Puerto Rico para la vida silvestre está muy bien documentado . Por ejemplo, las salinas de Cabo Rojo, en la costa suroeste, proveen áreas para el descanso y la alimentación de cientos de aves migratorias en ruta entre Norte y Suramérica. Antes del drenaje de los humedales costeros para propósitos agrícolas, pantanos de agua dulce como los de la Laguna Cartagena, Laguna Guánica y Ciénaga El Anegado proveían hábitat a más de 1 00 especies de aves residentes y migratorias . Los humedales de las tierras altas del área central son el último refugio de la cotorra puertorriqueña, una especie en peligro de extinción. Aún los humedales del área metropolitana de San Juan (Laguna La Torrecilla, Torrecilla Baja, Laguna de Piñones hasta Punta Vacía Talega) proveen un hábitat excelente para la vida silvestre, mantienen criaderos de peces de alto valor económico y proveen recreación y oportunidades educativas a la población urbana. Treintiocho especies de vertebrados, moluscos y crustáceos, y 46 especies de aves, algunos raros o en peligro de extinción como la mariquita, el alcatraz, el pato dominicano, el pato silbón y la paloma cabeciblanca han sido observados en el área . También las playas asociadas con estos humedales urbanos proveen sitios de anidaje para las tortugas carey de concha y tinglar, ambas en peligro de extinción (Del Llano y otros, 1986).

Water Supply Paper↗
USGS2024

Infectivity of wild-bird origin Influenza A viruses in Minnesota wetlands across seasons

The environmental tenacity of influenza A viruses (IAVs) in the environment likely plays a role in their transmission; IAVs are able to remain infectious in aquatic habitats and may have the capacity to seed outbreaks when susceptible wild bird hosts utilize these same environments months or even seasons later. Here, we aimed to assess the persistence of low-pathogenicity IAVs from naturally infected ducks in Northwestern Minnesota through a field experiment. Viral infectivity was measured using replicate samples maintained in distilled water in a laboratory setting as well as in filtered water from four natural water bodies maintained in steel perforated drums (hereafter, mesocosms) within the field from autumn 2020 to spring 2021. There was limited evidence for the extended persistence of IAVs held in mesocosms; from 65 initial IAV-positive samples, only six IAVs persisted to at least 202 days in the mesocosms compared to 17 viruses persisting at least this long when held under temperature-controlled laboratory settings in distilled water. When accounting for the initial titer of samples, viruses detected at a higher concentration at the initiation of the experiment persisted longer than those with a lower starting titer. A parallel experimental laboratory model was used to further explore the effects of water type on viral persistence, and the results supported the finding of reduced tenacity of IAVs held in mesocosms compared to distilled water. The results of this investigation provide evidence that many factors, including temperature and physicochemical properties, impact the duration of viral infectivity in natural settings, further extending our understanding of the potential and limitations of environmental-based methodologies to recover infectious IAVs.

Minnesota↗
USGS2022

Deep and machine learning image classification of coastal wetlands using unpiloted aircraft system multispectral images and lidar datasets

The recent developments of new deep learning architectures create opportunities to accurately classify high-resolution unoccupied aerial system (UAS) images of natural coastal systems and mandate continuous evaluation of algorithm performance. We evaluated the performance of the U-Net and DeepLabv3 deep convolutional network architectures and two traditional machine learning techniques (support vector machine (SVM) and random forest (RF)) applied to seventeen coastal land cover types in west Florida using UAS multispectral aerial imagery and canopy height models (CHM). Twelve combinations of spectral bands and CHMs were used. Our results using the spectral bands showed that the U-Net (83.80–85.27% overall accuracy) and the DeepLabV3 (75.20–83.50% overall accuracy) deep learning techniques outperformed the SVM (60.50–71.10% overall accuracy) and the RF (57.40–71.0%) machine learning algorithms. The addition of the CHM to the spectral bands slightly increased the overall accuracy as a whole in the deep learning models, while the addition of a CHM notably improved the SVM and RF results. Similarly, using bands outside the three spectral bands, namely, near-infrared and red edge, increased the performance of the machine learning classifiers but had minimal impact on the deep learning classification results. The difference in the overall accuracies produced by using UAS-based lidar and SfM point clouds, as supplementary geometrical information, in the classification process was minimal across all classification techniques. Our results highlight the advantage of using deep learning networks to classify high-resolution UAS images in highly diverse coastal landscapes. We also found that low-cost, three-visible-band imagery produces results comparable to multispectral imagery that do not risk a significant reduction in classification accuracy when adopting deep learning models.

Florida↗
USGS2026

Modification of rod surface elevation tables for monitoring extreme elevation shifts in wetlands

Rod surface elevation tables (RSETs) are effective tools for measuring changes in ground surface height, but these are not designed to withstand large changes in height (e.g., ±50 cm). After extreme changes in elevation due to erosion or accretion, RSET sites may be deemed unusable; however, this equipment usually can function indefinitely with in-situ modifications. Here, we provide a methodological description for in-situ modifications to RSETs that can be invaluable for long-term monitoring. In a sampling site with a high rate of surface elevation loss, longer pins can be inserted into the RSET arm to continue measurements. In a site with a high rate of accretion, RSETs buried in sediment can be raised by adding rod extensions, which is a particularly effective approach if the surface elevation can be measured before and after the attachment. Any modification to an RSET requires a reconceptualization of the original equations used to estimate change in the surface elevation, and these revised equations are described in this paper. We tested the measurement variability of the RSET before and after modification in West Dongting Lake, China. Results indicated that modification did not compromise data quality or precision and stability of RSET measurements. The reconceptualized equations incorporate offset adjustments that maintain datum consistency, enabling continuous data collection across pre- and postmodification phases with millimeter-scale precision. These RSET modifications can be used to extend the life of long-term RSET monitoring sites if the surface elevation has changed beyond the measurement capacity of the original RSET.

Ecosystem Health and Sustainability↗
USGS2008

Food web dynamics in a seasonally varying wetland

A spatially explicit model is developed to simulate the small fish community and its underlying food web, in the freshwater marshes of the Everglades. The community is simplified to a few small fish species feeding on periphyton and invertebrates. Other compartments are detritus, crayfish, and a piscivorous fish species. This unit food web model is applied to each of the 10,000 spatial cells on a 100 x 100 pixel landscape. Seasonal variation in water level is assumed and rules are assigned for fish movement in response to rising and falling water levels, which can cause many spatial cells to alternate between flooded and dry conditions. It is shown that temporal variations of water level on a spatially heterogeneous landscape can maintain at least three competing fish species. In addition, these environmental factors can strongly affect the temporal variation of the food web caused by top-down control from the piscivorous fish.

Mathematical Biosciences and Engineering↗
USGS2013

Dynamics of mangrove-marsh ecotones in subtropical coastal wetlands: fire, sea-level rise, and water levels

Ecotones are areas of sharp environmental gradients between two or more homogeneous vegetation types. They are a dynamic aspect of all landscapes and are also responsive to climate change. Shifts in the position of an ecotone across a landscape can be an indication of a changing environment. In the coastal Everglades of Florida, USA, a dominant ecotone type is that of mangrove forest and marsh. However, there is a variety of plants that can form the marsh component, including sawgrass (Cladium mariscus [L.] Pohl), needlegrass rush (Juncus roemerianus Scheele), and spikerush (Eleocharis spp.). Environmental factors including water depth, soil type, and occurrence of fires vary across these ecotones, influencing their dynamics. Altered freshwater inflows from upstream and increasing sea level over the past 100 years may have also had an impact. We analyzed a time series of historical aerial photographs for a number of sites in the coastal Everglades and measured change in position of mangrove–marsh ecotones. For three sites, detailed maps were produced and the area of marsh, mangrove, and other habitats was determined for five periods spanning the years 1928 to 2004. Contrary to our initial hypothesis on fire, we found that fire did not prevent mangrove expansion into marsh areas but may in fact assist mangroves to invade some marsh habitats, especially sawgrass. Disparate patterns in mangrove–marsh change were measured at two downstream sites, both of which had multiple fires over from 1948 to 2004. No change in mangrove or marsh area was measured at one site. Mangrove area increased and marsh area decreased at the second of these fire-impacted sites. We measured a significant increase in mangrove area and a decline in marsh area at an upstream site that had little occurrence of fire. At this site, water levels have increased significantly as sea level has risen, and this has probably been a factor in the mangrove expansion.

Florida↗
USGS1984

Persistence of Pasteurella multocida in Nebraska wetlands under epizootic conditions

Gleason Basin, a marsh located in the western part of the Rainwater Basin in Nebraska, was selected during the 1980 spring waterfowl migration as a study site to determine the presence and persistence of virulent Pasteurella multocida . Avian cholera mortality in migratory waterfowl using the Basin increased during a 2-wk period of a die-off beginning the first week of March when 2,409 carcasses were collected from the marsh. Study sites within the marsh were established for sampling water associated with and not associated with intact and scavenged carcasses. Isolations of virulent P. multocida were made from five of six study sites associated with either intact or scavenged carcasses for 3 days and from three of five non-carcass-associated study sites for 2 days. Recovery of these bacteria from this environment suggested a possible source of infection for susceptible waterfowl using the contaminated site.

Nebraska↗
USGS1993

Seasonal prevalence of Clostridium botulinum type C in the sediments of the northern California wetland

The prevalence of Clostridium botulinum type C (% of positive sediment samples) was determined in 10 marshes at Sacramento National Wildlife Refuge (SNWR), located in the Central Valley of California (USA), where avian botulism epizootics occur regularly. Fifty-two percent of 2,200 sediment samples collected over an 18-mo period contained C. botulinum type C (both neurotoxic and aneurotoxic) which was present throughout the year in all 10 marshes. The prevalence of C. botulinum type C was similar in marshes with either high or low botulism losses in the previous 5 yr. Marshes with avian botulism mortality during the study had similar prevalences as marshes with no mortality. However, the prevalence of C. botulinum type C was higher in marshes that remained flooded all year (permanent) compared with marshes that were drained in the spring and reflooded in the fall (seasonal). The prevalence of C. botulinum type C declined in seasonal marshes during the dry period. Similar declines did not occur in the permanently flooded marshes.

California↗