Reproductive Ecology of Black Mangrove (<Emphasis Type="Italic">Avicennia germinans</Emphasis>) Along the Louisiana Coast: Propagule Production Cycles,Dispersal Limitations,and Establishment Elevations

Black mangrove (Avicennia germinans) reproduces by producing propagules through the process of cryptovivipary, which requires a significant energy investment. We conducted a series of field and greenhouse studies to track propagule production in years of high and low disturbances (i.e., hurricanes), the effects of time and salinity on propagule dispersal potential, and the relationship between hydrology and propagule establishment elevations. Trees tended to produce greater numbers of propagules in years after hurricanes, and individual trees alternated the amount of energy they invested in reproduction in consecutive years. In the greenhouse, propagule buoyancy was affected by salinity with propagules in 36 remaining buoyant for over 110 days and establishment success decreasing with dispersal period length. Finally, a field survey across five sites in southeastern Louisiana revealed that the 2009 cohort of propagules established at significantly lower elevations than mature trees occurred. These findings elucidate some salient features of black mangrove reproductive biology in the northern portion of its North American distribution.     

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.     

The Thermodynamic Structure of Arctic Coastal Fog Occurring During the Melt Season over East Greenland

An automated method to classify Arctic fog into distinct thermodynamic profiles using historic in-situ surface and upper-air observations is presented. This classification is applied to low-resolution Integrated Global Radiosonde Archive (IGRA) soundings and high-resolution Arctic Summer Cloud Ocean Study (ASCOS) soundings in low- and high-Arctic coastal and pack-ice environments. Results allow investigation of fog macrophysical properties and processes in coastal East Greenland during melt seasons 1980–2012. Integrated with fog observations from three synoptic weather stations, 422 IGRA soundings are classified into six fog thermodynamic types based on surface saturation ratio, type of temperature inversion, fog-top height relative to inversion-base height and stability using the virtual potential temperature gradient. Between 65–80% of fog observations occur with a low-level inversion, and statically neutral or unstable surface layers occur frequently. Thermodynamic classification is sensitive to the assigned dew-point depression threshold, but categorization is robust. Despite differences in the vertical resolution of radiosonde observations, IGRA and ASCOS soundings yield the same six fog classes, with fog-class distribution varying with latitude and environmental conditions. High-Arctic fog frequently resides within an elevated inversion layer, whereas low-Arctic fog is more often restricted to the mixed layer. Using supplementary time-lapse images, ASCOS microwave radiometer retrievals and airmass back-trajectories, we hypothesize that the thermodynamic classes represent different stages of advection fog formation, development, and dissipation, including stratus-base lowering and fog lifting. This automated extraction of thermodynamic boundary-layer and inversion structure can be applied to radiosonde observations worldwide to better evaluate fog conditions that affect transportation and lead to improvements in numerical models.     

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.     

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.     

EUREKA industrial R&D projects for an improved environment

International collaboration is increasingly necessary in the field of environmental protection in relation to industrial research and development. The EUREKA initiative, launched in 1985, aims to increase industrial productivity and competitiveness in Europe by encouraging cross-border high technology research and development. The programme encompasses a number of ‘umbrella’ projects—EUROMAR, EUROCARE, EUROENVIRON, EUROTRAC and ENVINET. Each of these is designed to generate and support research and development projects. The paper gives examples of the projects and discusses the value of such large-scale international collaboration.     

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.     

The probable industrial origin of archaeological daub at an Iron Age site in Northeast Thailand*

Determining probable firing temperatures of daub recovered from archaeological sites provides opportunities to interpret the design and/or function of prehistoric structures. This paper critiques some of the methods for determining firing temperatures of daub, and presents a case study using samples from a secure depositional context at the Iron Age archaeological site of Noen U‐Loke, in northeast Thailand. Adopting a multimethod approach, the paper examines relationships between color, micro‐ and macro‐inclusions, elemental and mineralogical composition, physical form, and temperature, through the application of ICP‐MS, XRD analysis, magnetic susceptibility, and light microscopy. The important methodological point here is that the combined interpretation of independent measures provides a better estimate of the original firing temperatures of the archaeological material than has hitherto been possible. Initial examination implied that our samples were fired, in antiquity, at low temperatures, and concluded a nonindustrial source for the daub. We suggest that determining maximum temperatures for this original firing will provide the clearest discrimination between possible types of features (e.g., housing, kiln/furnace) from which the daub originally came. The results of our study indicate that the archaeological daub samples have been exposed to a range of temperatures from 200°C to 1000°C. It seems highly likely, therefore, that the daub was derived from a spatially complex structure, such as an industrial kiln or furnace, which has experienced a range of firing temperatures. © 2002 Wiley Periodicals, Inc.     

Ecological assessment to detect imminent change in coral reefs of Admiral Cockburn Land and Sea National Park,Turks and Caicos Islands

Coral reefs of the Turks and Caicos Islands (TCIs) (Caribbean Sea) constitute some of the few pristine coral reef systems in the world and play a crucial role in the islands’ economy because they support rich fisheries catches and tourism development. Ambitious development plans involving increase in fishing and tourism pressures are about to bring changes in coastal zone resources of the TCIs associated with increased sediments and nutrients and reduced predation by herbivorous fish on coral reefs. Understanding change is critical when attempting to protect the resources that these coral reefs support and to adopt proper management strategies. Yet, an environmental assessment program to detect imminent human‐induced changes on the surrounding reefs of the TCIs is lacking. Thus, (i) we obtained baseline data on benthic composition and coral community structure at seven reef sites of representative reefs of the TCIs within the Admiral Cockburn Land and Sea National Park (ACLSNP) of South Caicos Island and (ii) performed a priori statistical power analysis to calculate replication requirements for safely and confidently detecting small (δ = 0.1), medium (δ = 0.3), and large (δ = 0.5) effect sizes for a number of relevant to anticipated changes, univariate, benthic indices and for power β = 0.95. The platforms of the margin reefs studied (9–12 m depth) appeared rather variable regarding benthic composition but quite homogeneous regarding hard coral community structure. Mean percent cover of algal functional groups was 0.1 ± 0.3 (mean ± sd) percent for coralline algae and Halimeda, 0.1 ± 0.6 (mean ± sd) percent for macroalgae, 21.7 ± 33 (mean ± sd) percent for turf algae and 4.8 ± 4.0 (mean ± sd) percent for hard coral cover. The dominant benthic component, however, was carbonate substrate (mean ± sd = 30.4 ± 34.3), thus indicating an accreting reef framework. Mean hard coral density, colony size and recruit density were 5.5 ± 1.8 (mean ± sd) corals per 20‐m line transect, 13.0 ± 2.3 (mean ± sd) cm maximum colony diameter, and 1.3 ± 1.4 (mean ± sd) recruits per square foot, respectively. Due to high natural variance, hard coral colony size and density were practically the most sensitive indices in detecting even small size changes on benthos. Also, the geometric mean of log‐transformed colony size‐frequency distributions of the most abundant hard coral taxa, i.e. Montastrea annularis, Agaricia spp., Siderastrea spp. and Porites asteroides were practically sensitive for the same purpose. We hope that the study will optimize the spatial component of a necessary environmental impact assessment program on coral reefs of the TCIs once the natural spatial variability of the system has been assessed and sensitive, benthic, univariate indices have been identified for representative reference coral reef sites of the TCIs.