Temperature Tolerance of Early Life History Stages of Black Mangrove <Emphasis Type="Italic">Avicennia germinans</Emphasis>: Implications for Range Expansion

Avicennia germinans (L.) L. (black mangrove) grows at its North American latitudinal limit in coastal salt marshes of Louisiana, USA. To assess low-temperature tolerance of A. germinans, we evaluated the survival and developmental progress of three early life history stages (dispersal, stranded, and seedling stages) to three temperatures (5.7°C, 2.5°C, and −6.5°C) of four durations (2, 6, 12, and 24 h). Duration and temperature of exposure decreased mangrove survivorship, particularly 24-h exposure at −6.5°C. Although there was not a significant effect of stage on survivorship overall, both survival analysis and final mortality analysis indicate that dispersal stage had the greatest survivorship. Treatments had little impact on developmental progress of surviving propagules, but propagules exposed to −6.5°C were most susceptible to fungal infection. Greater cold temperature tolerance of the dispersal stage may be a mechanism for northward range expansion in Louisiana.     

Vertical surface water–groundwater exchange processes within a headwater floodplain induced by experimental floods

Restoring hydrologic connectivity between channels and floodplains is common practice in stream and river restoration. Floodplain hydrology and hydrogeology impact stream hydraulics, ecology, biogeochemical processing, and pollutant removal, yet rigorous field evaluations of surface water–groundwater exchange within floodplains during overbank floods are rare. We conducted five sets of experimental floods to mimic floodplain reconnection by pumping stream water onto an existing floodplain swale. Floods were conducted throughout the year to capture seasonal variation and each involved two replicate floods on successive days to test the effect of varying antecedent moisture. Water levels and specific conductance were measured in surface water, soil, and groundwater within the floodplain, along with surface flow into and out of the floodplain. Vegetation density varied seasonally and controlled the volume of surface water storage on the floodplain. By contrast, antecedent moisture conditions controlled storage of water in floodplain soils, with drier antecedent moisture conditions leading to increased subsurface storage and slower flood wave propagation across the floodplain surface. The site experienced spatial heterogeneity in vertical connectivity between surface water and groundwater across the floodplain surface, where propagation of hydrostatic pressure, preferential flow, and bulk Darcy flow were all mechanisms that may have occurred during the five floods. Vertical connectivity also increased with time, suggesting higher frequency of floodplain inundation may increase surface water–groundwater exchange across the floodplain surface. Understanding the variability of floodplain impacts on water quality noted in the literature likely requires better accounting for seasonal variations in floodplain vegetation and antecedent moisture as well as heterogeneous exchange flow mechanisms. Copyright © 2016 John Wiley & Sons, Ltd.     

Climate change, reproductive performance and diet composition of marine birds in the southern California Current system, 1969–1997

We studied the effects of low-frequency climate change on the reproductive performance of 11 species of marine bird in the southern California Current system, 1969–1997. Reproductive performance of Brown Pelican (Pelecanus occidentalis) and Double-crested Cormorant (Phalacrocrax auritus) in southern California demonstrated an increase in the 1970s and early 1980s, attributable to recovery from organochlorine contamination (primarily DDE). Brandt's Cormorant (Phalacrocorax penicillatus) in central California was the only species to demonstrate a secular increase in performance through time, a pattern that remains unexplained. Ashy Storm-petrel (Oceanodroma homochroa) and Pelagic Cormorant (Phalacrocorax pelagicus) demonstrated curvilinear patterns of change, with decreasing reproductive performance in the past decade. All other species including Western Gull (Larus occidentalis), Pigeon Guillemot (Cepphus columba), Xantus's Murrelet (Synthiloboramphus hypoleucus), Common Murre (Uria aalge), Cassin's Auklet (Ptychoramphus aleuticus) and Rhinoceros Auklet (Cerorhinca monocerata) showed diminishing reproductive performance through time. Patterns of change for the murre and auklets were not significant, presumably because of a lack of reproductive variation for these species, which display a conservative breeding effort (i.e. single-egg clutches). Changes in the birds' abilities to provision young and maintain chick survival during May–July each year appeared most closely related to overall changes in reproductive performance. Dietary change indicated a decline in use of juvenile rockfish (Sebastes spp.) by marine birds in central California. There was also significant interannual variability in consumption of juvenile rockfish and the euphausiid Thysanoessa spinifera. Patterns of change in marine bird reproductive performance were generally concordant between southern and central California after considering the period of recovery for Brown Pelican and Double-crested Cormorant. The decline in reproductive performance and changes in diet composition do not appear directly related to the polarity reversal of the Pacific Decadal Oscillation in 1976/1977. Instead, reproductive performance and dietary characteristics indicate substantial change in the late 1980s, suggesting another regime-shift at that time.     

Mental health, ethnography and the body

Summary Covert ethnographic research materials are used to highlight different individuals' embodied configurations of time and space (in this case people with mental health problems). Research relationships that revolve around body presentation and body movement are then examined. The problematic associations between covert ethnography and feminist methodologies are also addressed.     

A Case Study of Soil-Gas Sampling in Silt and Clay-Rich (Low-Permeability) Soils

Soil-gas sampling and analysis is a common tool used in vapor intrusion assessments; however, sample collection becomes more difficult in fine-grained, low-permeability soils because of limitations on the flow rate that can be sustained during purging and sampling. This affects the time required to extract sufficient volume to satisfy purging and sampling requirements. The soil-gas probe tubing or pipe and sandpack around the probe screen should generally be purged prior to sampling. After purging, additional soil gas must be extracted for chemical analysis, which may include field screening, laboratory analysis, occasional duplicate samples, or analysis for more than one analytical method (e.g., volatile organic compounds and semivolatile organic compounds). At present, most regulatory guidance documents do not distinguish between soil-gas sampling methods that are appropriate for high- or low-permeability soils. This paper discusses permeability influences on soil-gas sample collection and reports data from a case study involving soil-gas sampling from silt and clay-rich soils with moderate to extremely low gas permeability to identify a sampling approach that yields reproducible samples with data quality appropriate for vapor intrusion investigations for a wide range of gas-permeability conditions.     

Studies of a wind mechanism influencing the recruitment of blue crabs in the Middle Atlantic Bight

This report forms part of an on-going effort to understand the large yearly variations in blue crab harvest of Chesapeake Bay. Recent sampling programs have indicated that the larvae are transported out of the bay immediately after being spawned, and spend their first month offshore at the sea surface. Although it is well established that a mid and outer shelf southward flow occurs during all seasons in the Middle Atlantic Bight, very little is known of the nearshore currents. This study constitutes an effort to determine if the characteristically light, but northward, wind stress during the critical summer months is sufficient to drive northward counter flow at the surface and, hence, to reduce the chances that the larvae are being advected south and lost from the area of Chesapeake Bay.We investigate a local model of wind-driven currents on the continental shelf with vertical decoupling at the pycnocline. Additional driving forces include an alongshore sea surface slope and horizontal pressure gradients. With characteristic forcing values, it is found that the wind stress is indeed sufficient to drive a light northward flow within 25 to 50 km of the shoreline. We expect, then, that blue crab larval recruitment back to Chesapeake Bay may be partially dependent on summer wind stress. A comparison between a wind index time series and harvest several years later is strongly suggestive of such a dependency.     

Raman spectroscopic measurements of synthetic gas hydrates in the ocean

A Raman spectrometer extensively modified for deep ocean use was used to measure synthetic hydrates formed in an ocean environment. This was the first time hydrates formed in the ocean have been measured in situ using Raman spectroscopy. Gas hydrates were formed in situ in the Monterey Bay by pressurizing a Pyrex cell with various gas mixtures. Raman spectra were obtained for sI methane hydrate and sII methane + ethane hydrate. Gas occlusion resulting from rapid gas growth of methane hydrate was measured immediately after formation. The Raman shift for methane free gas was coincident with that of methane in the small 5¹² hydrate cage. The methane Raman peak widths were used to discriminate between methane in the free gas and hydrate phase. Methane + ethane sII hydrate was formed for 43 days on the seafloor. In this case, gas occlusion was not measured when the gas hydrates were allowed to form over an extended time period. Equivalent Raman spectra were obtained for the in situ and laboratory-formed sII methane + ethane hydrates, under similar p, T, and x conditions. With the Raman spectrometer operating in the ocean, seawater contributes to the Raman spectra obtained. Both the Raman bands for the sulfate ion and water were used to qualitatively determine the distribution of water phases measured (hydrate, seawater) in the Raman spectra.     

Significance of sedimentological studies to man's use of transitory coastal areas

A beach-ridge complex is a migrating sediment body constructed and kept in motion by high-energy processes, and the same processes that construct these features will, in time, partially or completely destroy them. The beach-ridge complex along the shore of southwestern Lake Michigan serves as an example. This body of sediment, approximately 17 by 3 km has undergone considerable change in the last 3,000 years, moving about 13 km along the shore as a result of forces generated by the Lake Michigan system — erosion at the northern end, deposition of the displaced sediment at the southern end of the complex. Sedimentological analysis of the beach-ridge complex demonstrates that each major modern environment can be characterized by a unique range in grain sizes, which make it possible to determine the environment in which the subsurface sediments were deposited. Lateral and thickness distribution of textural types can then be predicted. Erosion has been an important natural geologic process in the development of the beach-ridge complex, but it has become a problem only since man has occupied the nearshore areas. It will continue to be a problem, particularly at times of high lake level. Man's attempts to protect these areas by trying to alter the natural processes frequently have upset the delicate natural balance, unintentionally accelerating destruction in other areas. Beach replenishment is one method that would adapt well to this coast because there is an adequate supply of sand in the subsurface of the beach ridge complex whose grain size matches that of the modern beach sand.     

Classification of mesoscale features in the Brazil-Falkland Current confluence zone

The south-western Atlantic region, 30–46°S, 35–55°W is noted for the confluence of the warm Brazil Current and the cold Falkland Current, as well as the eddies created from the two systems. Previous studies of the Brazil-Falkland Current confluence have concentrated on the formation of eddies south of 35°S. However, in situ measurements and TOPEX/POSEIDON imagery of the region reveal eddies developing as far north as 32°S. These features are not evident in the coincident AVHRR (Advanced Very High Resolution Radiometer) imagery. In this study, the origin of the eddies identified are discussed with reference to the contemporary in situ measurements of temperature and salinity. Using the combination of satellite imagery and in situ data, it can be determined that the surface waters of the eddies north of 36°S are influenced by water from an estuarine source. TOPEX imagery enables the movements and variability of the regions water masses: estuarine outflow, Falkland and Brazil currents, to be monitored synoptically. The combination of satellite imagery and the higher resolution of in situ AMT measurements enables these water masses to be better identified.