Occurrence and use of Compsopogon coeruleus (Rhodophyta: Compsopogonaceae) in Fiji,South Pacific

The rhodophyte Compsopogon coeruleus (Balbis ex C. Agardh) Montagne is newly recorded from Fiji, South Pacific. Plants occur in dense masses in the Wainivesi River in the province of Tailevu. Local villagers collect the plants and use them to cook a “pudding” with tinned fish, very similar to “puddings” prepared by coastal Fijians using marine species such as Gracilaria and Hypnea. This is the first documented account of the use of Compsopogon as a gelling agent in the preparation of human food.     

Composition and thermal inertia of the Mawrth Vallis region of Mars from TES and THEMIS data

Clay mineral-bearing deposits previously discovered on Mars with near infrared (λ=0.3-5 μm) remote sensing data are of major significance for understanding the aqueous history, geological evolution, and past habitability of Mars. In this study, we analyzed the thermal infrared (λ=6-35 μm) surface properties of the most extensive phyllosilicate deposit on Mars: the Mawrth Vallis area. Clay mineral-bearing units, which in visible images appear to be relatively light-toned, layered bedrock, have thermal inertia values ranging from 150 to 460 J m⁻² K⁻¹ s^−1/2. This suggests the deposits are composed of a mixture of rock with sand and dust at 100-meter scales. Dark-toned materials that mantle the clay-bearing surfaces have thermal inertia values ranging from 150 to 800, indicating variable degrees of rockiness or induration of this younger sedimentary or pyroclastic unit. Thermal Emission Spectrometer (TES) spectra of the light-toned rocks were analyzed with a number of techniques, but none of the results shows a large phyllosilicate component as has been detected in the same surfaces with near-infrared data. Instead, TES spectra of light-toned surfaces are best modeled by a combination of plagioclase feldspar, high-silica materials (similar to impure opaline silica or felsic glass), and zeolites. We propose three hypotheses for why the clay minerals are not apparent in thermal infrared data, including effects due to surface roughness, sub-pixel mixing of multiple surface temperatures, and low absolute mineral abundances combined with differences in spatial sampling between instruments. Zeolites modeled in TES spectra could be a previously unrecognized component of the alteration assemblage in the phyllosilicate-bearing rocks of the Mawrth Vallis area. TES spectral index mapping suggests that (Fe/Mg)-clays detected with near infrared data correspond to trioctahedral (Fe²⁺) clay minerals rather than nontronite-like clays. The average mineralogy and geologic context of these complex, interbedded deposits suggests they are either aqueous sedimentary rocks, altered pyroclastic deposits, or a combination of both.     

Phytoplankton and particulate matter in Carlingford Lough, Ireland: An assessment of food availability and the impact of bivalve culture

In an attempt to assess the impact of bivalve culture in Carlingford Lough, Ireland, the seasonal cycles of nutrients, particulate matter, chlorophylla, and phytoplankton in the lough was investigated in 1992. Chlorophyll levels showed an increase in April, corresponding to the annual spring bloom, and levels remained relatively high (2–12 mg m^?3) throughout the summer before dropping to a winter minimum by December. Throughout the summer the phytoplankton community was dominated by diatoms, with microflagellates becoming an increasingly larger fraction of the biomass in autumn and winter. Dinoflagellates were only present on occasion in low numbers during the summer months. Seasonal variations in nitrate, phosphate, and silicate concentrations at all stations showed characteristic winter maxima and summer minima. Nitrate concentrations had reached a minimum undetectable level by June, at a time when the main freshwater input from the Clanrye River had dropped to <0.3 m³ s^?1. Particulate organic carbon (POC) composed approximately 5% of the suspended matter, with highest values in winter due to resuspension. Levels of biologically available POC, as determined by a modified BOD technique, were greatest in summer, and an inverse relationship was observed between total POC and its fraction that was biologically available. Most of the labile fraction was considered to be phytoplankton, and remineralization during the summer is suggested as a mechanism for maintaining high productivity during the summer months. Although the phytoplankton biology was uncoupled with that outside the lough, it is concluded that there is scope for expansion of the local bivalve mariculture industry without altering the ecosystem of the lough. The upper limit on such expansion would be set by practical considerations such as availability of space and site suitability due to water quality.     

Hypotaurine and thiotaurine as indicators of sulfide exposure in bivalves and vestimentiferans from hydrothermal vents and cold seeps

Vesicomyid clams, vestimentiferans, and some bathymodiolin mussels from hydrothermal vents and cold seeps possess thiotrophic endosymbionts, high levels of hypotaurine and, in tissues with symbionts, thiotaurine. The latter, a product of hypotaurine and sulfide, may store and/or transport sulfide non‐toxically, and the ratio to hypotaurine plus thiotaurine (Th/[H + Th]) may reflect an animal's sulfide exposure. To test this, we analyzed seep and vent animals with in situ sulfide measurements. Calyptogena kilmeri clams occur at high‐sulfide seeps in Monterey Canyon, while C. (Vesicomya) pacifica clams occur at seeps with lower levels but take up and metabolize sulfide more effectively. From one seep where they co‐occur, both had gill thiotaurine contents at 22–25 mmol kg⁻¹ wet mass, and while C. (V.) pacifica had a higher blood sulfide level, it had a lower Th/[H + Th] (0.39) than C. kilmeri (0.63). However, these same species from different seeps with lower sulfide exposures had lower ratios. Bathymodiolus thermophilus [East Pacific Rise (EPR 9°50′ N)] from high‐(84 μm ) and a low‐(7 μm ) sulfide vents had gill ratios of 0.40 and 0.12, respectively. Trophosomes of Riftia pachyptila (EPR 9°50′ N) from medium‐(33 μm ) and low‐(4 μm ) sulfide vents had ratios of 0.23 and 0.20, respectively (not significantly different). Ridgeia piscesae vestimentiferans (Juan de Fuca Ridge) have very different phenotypes at high‐ and low‐sulfide sites, and their trophosomes had the greatest differences: 0.81 and 0.04 ratios from high‐ and low‐sulfide sites, respectively. Thus Th/[H + Th] may indicate sulfide exposure levels within species, but not in interspecies comparisons, possibly due to phylogenetic and metabolic differences. Total H + Th was constant within each species (except in R. piscesae); the sum may indicate the maximum potential sulfide load that a species faces.     

Spatial and temporal variations in spectra of storm waves across a barred nearshore

Wave staffs and electromagnetic current meters were deployed on a profile across a two-bar system at Wendake Beach, southern Georgian Bay. This paper examines spatial and temporal changes in the characteristics of wave form, and the spectra of surface elevation and on-offshore current motion, during one storm. Non-linear effects of wave shoaling and breaking across the bars result in the appearance of secondary waves and both the wave and on-offshore current spectra have significant harmonic peaks during most of the storm. Significant low-frequency energy occurs only during the peak of the storm. While the peak frequency remains constant across the bar system, the proportion of energy in the primary peak is greatest in the troughs and lowest over the bar crests and there are similar changes in the proportion of energy in the first harmonic. However, in both surface elevation spectra and on-offshore current spectra, the greatest proportion of energy is found in frequencies related to the incident wind waves.     

Modern saltmarsh diatom distributions of the Outer Banks, North Carolina, and the development of a transfer function for high resolution reconstructions of sea level

We collected modern diatom samples from Currituck Barrier Island, Oregon Inlet and Pea Island marshes, Outer Banks, North Carolina, USA, which have different salinity regimes due to their varying distances from a major barrier island inlet. Multivariate analyses separate the saltmarsh diatom assemblages into distinct elevational zones, dominated by differing abundances of polyhalobous, mesohalobous and oligohalobous taxa, suggesting that the distribution of saltmarsh diatoms is a direct function of elevation, with the most important controlling factors being the duration and frequency of subaerial exposure.We developed the first diatom-based transfer function for the east coast of North America to reconstruct former sea levels based upon the relationship between diatom assemblage and elevation. Results imply that this is possible to a precision of ±0.08 m, superior to most similar studies from temperate, mid-latitude environments. The transfer function is used to construct a relative sea-level curve from fossil assemblages from Salvo, North Carolina. These results suggest a sea-level rise of 0.7 m over the last c. 150 years, at an average of c. 3.7 mm year⁻¹. This is consistent with existing sea-level data, and illustrates the utility of the transfer function approach.