Interstitial Sand Research Articles

Investigation of Plant Interactions Across Common Mycorrhizal Networks Using Rotated Cores.

Arbuscular mycorrhizal (AM) fungi influence plant mineral nutrient uptake and growth, hence, they have the potential to influence plant interactions. The power of their influence is in extraradical mycelia that spread beyond nutrient depletion zones found near roots to ultimately interconnect individuals within a common mycorrhizal network (CMN). Most experiments, however, have investigated the role of AM fungi in plant interactions by growing plants with versus without mycorrhizal fungi, a method that fails to explicitly address the role of CMNs. Here, we propose a method that manipulates CMNs to investigate their role in plant interactions. Our method uses modified containers with conical bottoms with a nylon mesh and/or hydrophobic material covering slotted openings, 15N fertilizer, and a nutrient-poor interstitial sand. CMNs are left either intact between interacting individuals, severed by rotation of containers, or prevented from forming by a solid barrier. Our findings suggest that rotating containers is sufficient to disrupt CMNs and prevent their effects on plant interactions across CMNs. Our approach is advantageous because it mimics aspects of nature, such as seedlings tapping into already established CMNs and the use of a suite of AM fungi that may provide diverse benefits. Although our experiment is limited to investigating plants at the seedling stage, plant interactions across CMNs can be detected using our approach which therefore can be applied to investigate biological questions about the functioning of CMNs in ecosystems.

Imaging analysis of biological soil crusts to understand surface heating properties in the Mojave Desert of California

Biological soil crusts (biocrusts) are composed of a combination of cyanobacteria, green algae, lichens, and mosses that can protect arid soil surfaces from erosive forces. The presence of biocrusts in desert regions is influenced by a complex interaction of climatic, edaphic, and topographic variables, but their distribution and coverage densities in southern California deserts are not precisely mapped. Visible satellite bands (red-green-blue; RGB) and infra-red image resolution are generally too coarse to distinguish between biocrusts and their interstitial sand substrates, limiting most remote sensing analysis of these soil biotic assemblages. The purpose of this study was to better understand the relationships between biocrust cover, surface coloration and roughness, and the thermal infra-red (TIR) emission properties of biocrusts to determine if new types of imaging of desert surfaces could be used to more accurately detect biocrust presence. Based on the results from megapixel digital photos and TIR imaging for nearly 130 different, well-developed biocrust surfaces in the Mojave and Lower Colorado Deserts of California, we designed laboratory heating experiments to test the effect of biocrust cover on the heating properties of sandy wash habitats. Biocrust samples collected from the field were subjected to artificial heating and cooling to simulate the Mojave Desert diurnal cycle. We used image segmentation algorithms to separate true-color biocrust images from their sandy substrates, and to map the heating and cooling patterns of these surfaces with different levels of biocrust coloration and roughness. The major findings of this study showed that biocrust patch images in the field had Red texture mean values between digital numbers of 95 and 131 with moderate positive tail shewness levels, indicative of a highly rugose surface of the biocrust cover. Such patches were also well-compacted overall, with moderate skewness toward negative tails. In controlled laboratory temperature experiments to simulate the desert diurnal cycle, surface wetting with a fine mist of water resulted in significantly lower peak surface temperatures of biocrust samples compared to dry biocrust heating results of the same crust and sand samples. The findings of this study can improve future mapping for lichen-dominated biocrust surfaces in the Mojave Desert.

Stachorutes najtae n. sp., a new psammophile species of Collembola from Italy (Neanuridae, Pseudachorutinae)

ABSTRACT Stachorutes najtae n. sp. is described from the interstitial sand dunes of central Italy. It has 4 + 4 eyes with a postantennal organ composed of 7–9 simple vesicles and the furcal dens with six chaetae. Stachorutes najtae n. sp. appears closely related to S. gracilis Smolis & Shvejonkova, 2006 from which it can be separated by the different chaetotaxy of the dens and legs.

Turbulent Flow and Sand Transport over a Cobble Bed in a Laboratory Flume

AbstractImproving the prediction of sand transport downstream of dams requires characterization of the interaction between turbulent flow and near-surface interstitial sands. The advanced age and impending decommissioning of many dams have brought increased attention to the fate of sediments stored in reservoirs. Sands can be reintroduced to coarse substrates that have available pore space resulting from periods of sediment-starved flow. The roughness and porosity of the coarse substrate are both affected by sand elevation relative to the coarse substrate; therefore, the turbulence characteristics and sediment transport over and through these beds are significantly altered after sediment is reintroduced. Past work by the writers on flow over sand-filled gravel beds revealed that the fine-sediment level controls the volume of material available for transport and the area of sediment exposed to the flow. The present work expands on the gravel-bed experiments by conducting similar measurements of turbulent f...

Gut morphology and relative gut length do not reliably reflect trophic level in gobiids: a comparison of four species from a tropical Indo-Pacific seagrass bed

Trophic level and gut morphology are closely related in fish, and relative gut length (RGL) is a commonly accepted correlate of fish diet (Al-Hussaini, 1947; Geevarghese, 1983; Elliott and Bellwood, 2003; Karachle and Stergiou, 2010). Generally, gut length reflects diet as predators commonly have short and simple guts, while in omnivores and herbivores they are long and complex, reflecting digestibility and nutrient content of a species’ preferred food item (e.g. Al-Hussaini, 1947; Elliott and Bellwood, 2003; Karachle and Stergiou, 2010). Most species of Gobiidae are zoobenthivores, but their diet may also contain algae and organic matter (Stergiou and Karpouzi, 2002; Nakamura et al., 2003; Hernaman et al., 2009; Zander, 2011). This complicates assigning species explicitly to a trophic guild. Nevertheless, species have been attributed to trophic guilds based on food preferences (e.g. Horinouichi and Sano, 2000; Nakamura et al., 2003; Nanjo et al., 2008). Cryptocentrus spp., for example, are microcarnivores (Karplus, 1987; Thacker and Roje, 2011), Amblygobius and Valenciennea spp. feed on detritus and interstitial sand fauna, with A. phalaena additionally feeding on filamentous algae (Nakamura et al., 2003; Nanjo et al., 2008). Austrolethops wardi is the only known gobiid nearly exclusively relying on seagrass (Kneer et al., 2008; Liu et al., 2008). Accordingly, we tentatively expected long guts in the omnivorous A. phalaena and V. sexguttata and herbivorous A. wardi, and short guts in the zoobenthivore C. cinctus. We tried to identify trophic levels in four sympatric Indo-Pacific gobiids (Amblygobius phalaena, Austrolethops wardi, Cryptocentrus cinctus, and Valenciennea sexguttata) by comparing gut morphology and relative gut length sensu Al-Hussaini (RGL; 1947).

Quality or quantity: small-scale patch structure affects patterns of biodiversity in a sublittoral blue mussel community

It is widely accepted that blue mussel Mytilus edulis L. beds support a high macrofaunal diversity. Nonetheless, sublittoral mussel beds on rocky shores have rarely been examined in a patch context to determine the processes creating and maintaining the diversity and assemblages of organ- isms occupying them. Whereas the species-area relationship is a well-established theory in ecology, less is known about its effect on faunal compositions in aquatic habitats. Also, the effect of patch shape and relative patch edge are poorly studied within a rocky shore mussel framework. The pre- sent study examined the effects of blue mussel patch size, patch shape, and the presence of algae and sand in mussel patches on the composition and diversity of associated macrofaunal communities in sublittoral habitats. In line with the species-area relationship, we found that the total number of taxa increased with patch size up to ca. 500 cm 2 , thereafter declining. Small patches largely lacked annelid worms and showed a lower diversity of gastropod species. We also found that the diversity was further enhanced by a high biomass of blue mussels, the presence of algae and the weight of interstitial sand. The shape of the patch had no effect on species richness, but affected the species composition. We conclude that structural components of sublittoral blue mussel habitats, such as patch content and shape, greatly affect the diversity and faunal assemblage. This has important impli- cations in conservation biology, since habitats are becoming more fragmented. Our study demon- strates that not only habitat quantity, but also quality has a large impact on species communities in marine ecosystems.

Sand and sandbar willow: a feedback loop amplifies environmental sensitivity at the riparian interface

Riparian or streamside zones support dynamic ecosystems with three interacting components: flowing water, alluvia (river-transported sediments), and vegetation. River damming influences all three, and subsequent responses can provide insight into underlying processes. We investigated these components along the 315-km Hells Canyon corridor of the Snake River that included reaches upstream, along, and downstream from three large dams and reservoirs, and along the Salmon River, a free-flowing tributary. Sandbar willow was generally the woody plant at the lowest bank position and was abundant along upstream reaches (53, 45, 67% of transects), sparse along reservoirs (11, 12, 0%), and sparse along the Snake River downstream (11%). It was prolific along the undammed Salmon River (83%) and intermediate along the Snake River below the Salmon inflow (27%), indicating partial recovery with the contribution of water and sediments. Along these rivers, it commonly occurred on sandy substrates, especially on shallow-sloped surfaces, and emerged from interstitial sands between cobbles on steeper surfaces. However, along the Snake River below the dams, sandbars have eroded and willows were sparse on remnant, degrading sand surfaces. We conclude that a feedback loop exists between sands and sandbar willow. Sand favors willow colonization and clonal expansion, and reciprocally the extensively branched willows create slack-water zones that protect and trap sands. This feedback may sustain surface sands and sandbar willows along free-flowing river systems and it amplifies their mutual vulnerability to river damming. Following damming, sediment-depleted water is released downstream, eroding surface sands and reducing willow colonization and expansion. With willow decline, sands are further exposed and eroded, compounding these impacts. From this feedback, we predict the coordinated depletion of surface sands and riparian willows along dammed rivers throughout the Northern Hemisphere.

Library-dependent and library-independent microbial source tracking to identify spatial variation in faecal contamination sources along a Lake Ontario beach (Ontario, Canada)

Multiple microbial source tracking methods were applied to investigate spatial variation in faecal pollution sources impacting a 1.7 km freshwater beach on Lake Ontario (Canada). The highest E. coli concentrations measured in the study area were from interstitial sand pore water at Sunnyside Beach, reaching 2.6 x 10(6) CFU/100 ml. These E. coli concentrations exceeded those in the nearby Humber River and Black Creek, which are impacted by combined sewer overflows containing municipal wastewater and by stormwater conveying washoff from the urban area. Library-independent Bacteroidales HF183 analyses identified the more frequent occurrence of municipal wastewater contamination in the Humber River and at a Sunnyside Beach location closest to the mouth of the river. Library-dependent E. coli antibiotic resistance and rep-PCR DNA fingerprinting analyses identified the more frequent occurrence of bird faecal contamination at Sunnyside Beach locations away from the river mouth. These microbial source tracking results raise caution about managing beaches with multiple sources of contamination as a single entity without considering spatial variability in faecal pollution sources and the need for more localized beach management practices.

Soil development on Late Quaternary river terraces in a high montane valley in Bhutan, Eastern Himalayas

We examined the geochemistry and micromorphology of the soils on a suite of morphologically well-defined and visually distinct fluvial terraces, up to 40 m elevation above the current riverbed, at Thangbi in the upper Bumthang Valley, Bhutan. The alluvia forming each of the terraces are lithologically and structurally similar, with shallow or moderately deep, clast-free sandy loam overbank deposits capping deep clast-supported beds of rounded boulders and interstitial sand. The topsoils on the 40 m terrace have more silt than those on the lower terraces. The soils are interpreted mainly as a monoclinal post-incisive chronosequence. Features that indicate progressive pedogenesis with increasing elevation include subsoil rubefaction, crystallinity of free Fe sesquioxides, and weathering of susceptible primary minerals, such as biotite and hornblende. However other soil attributes show no systematic trends and the overall impression is of limited pedogenesis, even in the soils on the higher terraces. We examine possibilities that the immaturity of the soils is due to pedogenic rejuvenation by post-incision additions to the soil parent materials.

Vertical gradational variability of fines deposited in a gravel framework

AbstractVertical gradational structures develop as sand infiltrates into static gravel beds. Understanding the vertical distribution of interstitial sand deposits will improve predictions of ecological suitability and hyporheic hydrodynamics. A series of flume experiments was performed to investigate fine infiltration processes. Four sand distributions were introduced into flows over gravel beds. After each experiment, bed cores were extracted and analysed in vertical layers to examine the gradational trends with depth. Vertical trends of fine content were highly sensitive to the relative grain‐size distributions of the gravel bed and the introduced sand. For experiments with d15gravel/d85sand ratios 15·4 and larger unimpeded static percolation was observed, where sand filled the voids relatively uniformly from the bottom of the gravel layer to the top. Experiments with ratios 10·6 and smaller bridged. Sand clogged a thin layer of gravel pores near the bed surface, precluding subsequent infiltration. Interstitial sand deposits fined with depth of penetration for all experiments which was the result of three distinct but overlapping processes. (i) Granular sorting: As particles fell through the substrate, smaller material preferentially passed through the voids deeper into the gravel. (ii) Bed‐load sorting: Size segregation occurs in the wake of the leading bed form as smaller particles saltate further and settle first. (iii) Hydraulic sorting: Smaller sand was transported preferentially as suspended load filling the deep voids of the furthest flume positions downstream. Finally, when the experiments that formed a bridge layer were replicated with higher bed shear stresses, less interstitial sand deposition was observed. Higher shear stresses transported coarse particles downstream more efficiently causing bridge layers to form earlier and allowing less time for suspended load to settle into the deeper substrate pores before the pathways were closed.

Equilibrium entrainment of fine sediment over a coarse immobile bed

The transported load in most fluvial systems, including gravel‐bedded rivers, includes fine‐grained sediment. Models for suspended sediment transport have focused on sand‐covered beds, rendering incomplete the theoretical and empirical framework for predicting fine sediment transport and routing. We conducted laboratory experiments involving sand transport over large immobile grains. The experiments were scaled such that immobile particles were much larger than the mobile sediment, but less than 10% of flow depth, and that bed shear stresses, scaled by the size of the mobile sediment, were indicative of transport in suspension. The experiments were conducted in equilibrium transport and included measurements of near‐bed sediment concentration and interstitial sand storage for a range of flow and transport rates. Partial filling of grain interstices occurred over a narrow range of flow and transport rates, indicating a sharp threshold between no interstitial sand storage and a sand‐covered bed. Less sand coverage on the bed resulted in higher near‐bed sand concentrations per unit area of sand than runs with greater sand coverage. As sand bed elevation decreased relative to the coarse grains, turbulent wakes shed by the large grains appeared to enhance grain entrainment more than the corresponding decrease in bed area covered by sand resulted in decreased entrainment. Elevated concentrations were maintained until the bed was depleted of fine sediment. These results are formalized in a proposed sand elevation correction function that scales the entrainment rate for a bed partially covered by sand to the entrainment rate that would be predicted for a sand‐covered bed.

New and Noteworthy Venezuelan Glanapterygine Catfishes (Siluriformes, Trichomycteridae), with Discussion of Their Biogeography and Psammophily

Four new species of the trichomycterid subfamily Glanapteryginae are described from the Río Orinoco basin of Venezuela. Two new species each in Pygidianops Myers 1944 and Typhlobelus Myers 1944 represent the first documented occurrence of these genera in Venezuela, and for Pygidianops the first occurrence outside the Río Negro basin. The new species were captured from sand-bottom habitats in two disparate locations in the Orinoco River basin and display a remarkable suite of reductive features, such as loss of eyes, fins, and pigment, and reductions or absence of laterosensory canals and odontodes. Pygidianops cuao, n.sp. from the Río Cuao, a clear-water tributary of the upper Orinoco River, is diagnosed from its congeners by the presence of diminutive eyes and a triangular skin flap at the corner of the mouth. Pygidianops magoi, n.sp., known from near the delta of the Orinoco River, is diagnosed from its congeners by the absence of pectoral and anal fins, presence of four laterosensory pores, and nine or ten caudal-fin rays. Typhlobelus guacamaya, n.sp. from the Río Cuao is diagnosed relative to its congeners by the presence of three branchiostegal rays, posterior naris absent, lack of pleural ribs, and is further distinguished from both T. ternetzi and T. macromycterus by the absence of eyes and from T. lundbergi by the presence of three laterosensory canal pores. Typhlobelus lundbergi, n.sp. from the lower Orinoco is diagnosed by the presence of four laterosensory canal pores and further distinguished from T. ternetzi and T. macromycterus by the absence of eyes. We review the characters useful in diagnoses of Pygidianops and Typhlobelus among trichomycterid catfishes and discuss morphological patterns in the diversification of the Glanapteryginae. Species of Pygidianops and Typhlobelus are known only from the rivers draining the Guyana and Brazilian shields, yet within these areas they occupy all major water types. Such broad ecological range suggests that the geographic distribution of species of these two genera are not limited by water type. That observation, plus their common occurrence in the ubiquitous shallow sand-bottom habitats of the larger rivers of the shield regions of northern South America, indicate that species of Pygidianops and Typhlobelus may be expected to occur throughout the entire Amazon and Orinoco basins. The evolution of habitat preference in glanapterygines seems to follow a trend toward increased specialization for interstitial environments. The degree of psammophilic adaptation in species of Pygidianops and Typhlobelus is remarkable, without parallel in siluriforms and perhaps in any other freshwater fishes. We describe the physical characteristics of the sand and review the suite of morphological specializations for life in interstitial sand that are shared by these species, such as loss or reduction of certain structures and presence in these species of paired metapleural keels along the ventral edges of the abdomen formed by a long ridge of stiffened integument, underlain by well-differentiated medial infracarinalis muscles, that are superficially similar to the metapleural folds of sand-dwelling cephalochordates and other interstitial organisms.

Three New Species of Saccocirrus (Polychaeta: Saccocirridae) from Hawai'i

Three new species of saccocirrids from interstitial sand habitats off O‘ahu, Hawai‘i, are described. Two are from subtidal depths, 9–33 m, and the third is from the intertidal to 3.5 m deep on a fringing reef and at Hanauma Bay, the Marine Life Conservation District and public park. The two deeper-water species, Saccocirrus oahuensis, n. sp. and S. waianaensis, n. sp., have 76–119 and 157–210 segments, respectively; they also have bilateral gonads but lack a pharyngeal pad. The third, S. alanhongi, n. sp., has 35–47 segments, unilateral gonads, and a muscular pharyngeal pad. These species are distinguished from 18 known Saccocirrus spp. by their unique chaetation, number of segments, presence or absence of ventral cilia, and pygidial adhesive structures. Saccocirrus oahuensis consumes foraminiferans, and S. alanhongi contained diatoms, unicellular algae, and ostracods. These species add to the interstitial fauna of O‘ahu and cooccur with polychaetes Nerilla antennata (Nerillidae) and protodrilids (Protodrilidae), and Kinorhyncha. Saccocirrus alanhongi withstands almost daily disturbance by 600–1200 bathers per day entering the sandy swimming holes in the reef at Hanauma Bay.

Characteristics and Depositional Processes of Large-scale Gravelly Gilbert-Type Foresets in the Miocene Doumsan Fan Delta, Pohang Basin, Se Korea

ABSTRACT The Doumsan fan delta in the Miocene Pohang Basin (SE Korea) includes large-scale gravelly Gilbert-type foresets that are more than 150 m high and dip at about 20°. The foresets consist of six sedimentary facies: medium- to thick-bedded sandy gravel deposits with variable grading patterns and bed geometries (Facies A), thin- to medium-bedded, commonly inversely graded sandy gravel deposits (Facies B), sheet-like layers, a few grains thick, of pebble gravel (gravel sheets; Facies C), lensoidal layers, a few grains thick, of cobble to boulder gravel (gravel lenses; Facies D), thin-bedded sand with outsized clasts (Facies E), and very thick-bedded (> 10 m thick) disorganized gravel deposits in the toeset area (Facies F). These facies are indicative of deposition from cohesionless ebris flows (Facies A and B), debris falls (Facies C and D), turbulent flows (Facies E), and very thick debris flows that are related to large-scale foreset failure (Facies F). These facies are in close association with one another, except for Facies F, and are either vertically superposed or laterally juxtaposed within single sedimentation units. This suggests that these facies originated from a series of evolving sediment gravity flows. A cohesionless debris flow generated at the topset-foreset boundary or on the middle of the foreset slope segregated its sediments into a pebble-rich lower division and a sandy upper division with sparse cobble-to-boulder clasts by preferential upward drift of large clasts and surface transformation of fine-grained material. The pebbly lower division was emplaced by frictional freezing, forming Facies A beds. On the other hand, the sediments in the upper division continued to move as a sandy turbulent flow and bouldery debris fall, resulting in Facies E and D deposits downslope. The cohesionless debris flow occasionally transformed into a series of thinner flows by development of roll waves along the top of the flow, producing Facies B layers on the margin of a Facies A bed. Otherwise the cohesionless debris flow transformed into grain-assemblage debris fall and single-grain debris fall consecutively by removal of interstitial sand via downward percolation and stripping into ambient water. The debris falls produced gravel sheets (Facies C) and gravel lenses (Facies D). During this flow transformation, cobble- to boulder-size clasts and sandy material were selectively transported farther downslope, resulting in prominent textural bimodality of the prodelta deposits, which comprise isolated large clasts and lensoidal deposits of cobble-to-boulder gravel set in sandy background material.

Preliminary data on rotifers in the interstitial of the Ninnescah river, Kansas, USA

One-hundred five rotifer species were identified from a sandy, plains river in Kansas, USA (the Ninnescah river). Of those rotifers identified, eighty occurred only in the interstitial sand, fifty-six in only the flow as plankton, and thirty-one from both habitats. Most species can be characterized as being more commonly found in littoral habitats, and not the interstitial or plankton. Lecane inermis (Bryce, 1892) had the highest density in the hygropsammon interstitial with an average 401 ind. 10 cm−3 at 1–3 cm depth in September 1993. New records for the US include Encentrum wiszniewski Wulfert (1939), E. longidens Donner (1943) ant E. (Parencentrum) longipes Wulfert (1960). A small form of Lecane levistyla Olofsson (1917) is further examined and discussed.

Rotifer Look-Alikes: Two Species of Colurella Are Ciliated Protozoans

Some 19 valid species of in the genus Colurella have been described from all parts of the world, mostly from littoral or interstitial habitats of fresh and salt waters. Colurella monodactylos and C. althausae, described from marine interstitial sands of the Black Sea and Caribbean, respectively, are significantly different from their congeners. Although no type specimens were deposited for either species, published drawings or photographs provide enough evidence to conclude that both of these rotifers are in fact ciliated protists of the family Dysteriidae, probably of the genus Dysteria. Additional key words: protist, interstitial, benthic Rotifers of the genus Colurella BORY DE ST. VINCENT 1824 are small, mostly littoral or benthic animals belonging to the class Monogononta. Their morphology features a single-piece lorica, oval or rounded, laterally flattened, dorso-ventrally folded (as in a cladoceran), with internal ventral membrane (sulcus) between the lateral edges of the lorica. They have an anterior head, and a threeor four-segmented foot and two moderately long toes protruding postero-ventrally. Their corona has a membranous cap (Fig. la-d). At least 19 different species of Colurella have been described to date (Koste 1978; Kutikova & Arov 1985). Althaus (1957) described and figured an inhabitant of the psammon of the Black Sea with similar lorica shape, body dimensions, and apparent habitat as a rotifer of the genus Colurella. Its foot was obscured and the putative single toe protruded postero-ventrally as expected from a Colurella rotifer. No species of Colurella to that date had been described with a single

Physical factors controlling abundance of meiofauna on tidal and atidal beaches

Quantitative samples of interstitial sand beach meiofauna were collected from Morocco along the North African coast (Algeria and Tunisia) and northwards to Lebanon, Turkey and Cyprus. Data on the sediment median diameter, sorting coefficient and beach temperature were used to construct multiple-regression equations relating these factors to the total meiofaunal numbers. Curvilinear regression was found to give a significantly better fit than linear regression in all cases but one. Treating the whole Mediterranean data, the equation explained 9.3% of the variance in meiofaunal abundance. Within narrower geographical areas, however, the equations explained significantly more of the variance: 56.70% of Moroccan tidal beach data, 75.60% of South Tunisian tidal beach data, and 62.3% of South Tunisian atidal beach data. For the tidal beach equations sorting was the most important factor, followed by temperature and median diameter. It is suggested that the factors controlling meiofaunal abundance on these beaches are likely to be wave, tide and current action which also control sorting. The lack of fit of most atidal beach data suggests that here biological interactions such as competition and predation may control meiofaunal abundance. The detection of beaches affected by pollutants may also be possible using regression techniques. Beaches having a significantly enriched population (sewage-induced) or depleted population (pollutant-induced) can be readily detected.

Some notes on Tubiluchus corallicola (Priapulida) from Barbados, West Indies

The occurrence of Tubiluchus corallicola (van der Land) in a lagoon on the East coast of Barbados, West Indies, is reported. 23 adult and 2 larval specimens were found in a sample taken from a subtidal stromatolite on which the animals presumably inhabited the algal surface layer. A comparison with data from earlier findings shows that the species is not confined to a particular type of substratum, yet morphologically it seems to be well adapted for a life in the interstitial sand habita. For the first time, living animals were observed and photographed. Their behavior and movements are briefly described and an account of morphological and histological details, as seen in squeezing preparations and photomicrographs, is presented.

An interstitial fauna transect of a Solomon Islands sandy beach

Surface sand samples were collected from a number of stations arranged down a transect of the beach at Komimbo Bay, west Guadalcanal. The included interstitial sand animals have been identified to generic level and their distribution and relative numbers are described. The transect was surveyed and the sand samples have been subjected to a particle size analysis.

Synorogenic Quartz Sandstone in the Jurassic Mobile Belt of Western Nevada: Boyer Ranch Formation

The province of Lower Mesozoic layered rocks in western Nevada contains a diversity of marine lithologies whose deposition continued locally as late as Middle Jurassic time. At places in the province, mature quartz sandstone constitutes all or part of the highest stratigraphic units in sections of non-volcanic rocks and is believed to record the last deposition of terrigenous sediments before complete effacement of the marine basin by widespread orogeny. The sandstone was deposited early in the erogenic episode and at least locally in troughs created by folding of subjacent rocks. The sands are anomalously mature with respect to co-deposited clastic components and to coarse detrital materials in nearly all earlier Mesozoic rocks of the province. The problems are the source of the quartz sand and the reasons the sand was deposited synorogenically. The name, Boyer Ranch Formation, is formally proposed for a lithesome of homogeneous Jurassic quartz sandstone and basal conglomerate and limestone in the Dixie Valley region which is approximately in the northern third of the outcrop area of Jurassic quartz sandstone in western Nevada. The Boyer Ranch Formation contains up to 500 ft of sandstone, largely fine-grained calcareous quartz arenite, whose granulometric properties suggest eolian sorting, but whose bedding indicates quiet-water deposition. The sandstone lies above limestone and carbonate-pebble conglomerate with interstitial quartz sand. The inferred early Mesozoic geographic and tectonic histories in the Dixie Valley region suggest that the sands of the Boyer Ranch Formation accumulated at the eastern shoreline of the Mesozoic basin in western Nevada in late Early or Middle Jurassic time. Until the onset of orogeny, the sands remained unlithified, probably owing to eolian saltation, and followed a generally westerly regression of the shoreline. Postulated strong wave action prevented seaward movement of the sand. The late Early Jurassic or Middle Jurassic (or both) orogeny created local troughs which the sea reinvaded and provided an irregularly configured and low-energy shoreline environment such that movement of the sand into the water was no longer impeded. The sands may have evolved locally through the action of water and wind at the beach of the Early Mesozoic sea in western Nevada, or they may have been largely co-derived from a distant source with sands in Jurassic rocks of the eastern Cordillera and the Colorado Plateau.