Bottom Type Research Articles

Spatial and temporal variations of inshore demersal fishes in the Gulf of Gabes (Tunisia, Central Mediterranean Sea)

In the Gulf of Gabes (South-east of Tunisia), the spatial and temporal variations of the demersal fishes communities were examined during two benthic trawl surveys conducted on July 2009 and July 2010 aboard a research fishing vessel. 16 sampling stations were surveyed on inshore bottoms, from 15 to 50 m depth. Seventy-five fish species belonging to two classes were recorded as follows: Elasmobranchii (8 spp.) and Actinopterygii (67 spp.). In the coastal area of the gulf, the inter-annual comparison of the abundance of the demersal fish fauna shows a significant improvement during the summer of 2010 compared to the summer of 2009. This increase is modelled in all surveyed locations especially, in Southern Kerkennah and in Eastern Djerba. This area appeared to be in a good ecological condition hosting an important variety of fish species associated with meadows of Posidonia oceanica and beds of the brown algae Arthrocladia villosa. The species’ compositions of the demersal fish assemblage showed clearly that the spatial and temporal analysis represented the differences of abundance of the fish’s assemblage during these two cruises (summer 2009 and summer 2010). These differences were closely related to peculiar characters of the fauna and biotopes (improving of bottom type and state of vegetation cover community).

After the Fall: Legacy Effects of Biogenic Structure on Wind-Generated Ecosystem Processes Following Mussel Bed Collapse

Blue mussels (Mytilus edulis) are ecosystem engineers with strong effects on species diversity and abundances. Mussel beds appear to be declining in the Gulf of Maine, apparently due to climate change and predation by the invasive green crab, Carcinus maenas. As mussels die, they create a legacy of large expanses of shell biogenic structure. In Maine, USA, we used bottom traps to examine effects of four bottom cover types (i.e., live mussels, whole shells, fragmented shells, bare sediment) and wind condition (i.e., days with high, intermediate, and low values) on flow-related ecosystem processes. Significant differences in transport of sediment, meiofauna, and macrofauna were found among cover types and days, with no significant interaction between the two factors. Wind condition had positive effects on transport. Shell hash, especially fragmented shells, had negative effects, possibly because it acted as bed armor to reduce wind-generated erosion and resuspension. Copepods had the greatest mobility and shortest turnover times (0.15 d), followed by nematodes (1.96 d) and the macrofauna dominant, Tubificoides benedeni (2.35 d). Shell legacy effects may play an important role in soft-bottom system responses to wind-generated ecosystem processes, particularly in collapsed mussel beds, with implications for recolonization, connectivity, and the creation and maintenance of spatial pattern.

The Past and Present of Discharge Capacity Modeling for Spillways—A Swedish Perspective

Most of the hydropower dams in Sweden were built before 1980. The present dam-safety guidelines have resulted in higher design floods than their spillway discharge capacity and the need for structural upgrades. This has led to renewed laboratory model tests. For some dams, even computational fluid dynamics (CFD) simulations are performed. This provides the possibility to compare the spillway discharge data between the model tests performed a few decades apart. The paper presents the hydropower development, the needs for the ongoing dam rehabilitations and the history of physical hydraulic modeling in Sweden. More than 20 spillways, both surface and bottom types, are analyzed to evaluate their discharge modeling accuracy. The past and present model tests are compared with each other and with the CFD results if available. Discrepancies do exist in the discharges between the model tests made a few decades apart. The differences fall within the range −8.3%–+11.2%. The reasons for the discrepancies are sought from several aspects. The primary source of the errors is seemingly the model construction quality and flow measurement method. The machine milling technique and 3D printing reduce the source of construction errors and improve the model quality. Results of the CFD simulations differ, at the maximum, by 3.8% from the physical tests. They are conducted without knowledge of the physical model results in advance. Following the best practice guidelines, CFD should generate results of decent accuracy for discharge prediction.

Position-selective solution phase growth of fullerene crystals

An efficient method for the formation of hexagonal disk shape C60 crystals at desired positions on a solid substrate has been achieved. The detailed growth behavior was studied through in-situ observation and series of control experiments. Our position selective growth technique enabled a fabrication of bottom electrode type C60 single crystal devices which exhibited n-type field-effect transistor behavior and photo response. Moreover, the C60 single crystal devices were further exploited to study alkali metal doped C60 crystal and its superconductivity.

Study on rigidity evaluation of composite girder with bottom steel plate type composite slab

Study on rigidity evaluation of composite girder with bottom steel plate type composite slab

Пространственно-временная трансформация грунтового комплекса водохранилищ Волги. Сообщение 6. Донные отложения Куйбышевского водохранилища и их картирование с использованием геоинформационных технологий

The article presents the geo/informational analysis of the spatial/temporal transformation of the Kuybyshev Reservoir soil complex structure and qualitative composition according to the materials of hydrological surveys of 1961, 1983, 2001–2002 and 2015–2017. As a result of the raster images vectorization we obtained three topical geo/information layers, every one of them contained the data sufficient for mapping the appropriate period of the researches. Analysis of the fourth layer in the area of the model Volga-Kama Expansion (F = 1011 km2) characterized by a complicated crest-shallow bottom relief, diverse hydrodynamic processes caused by water input via the Volga and the Kama and a wide spectrum of the windwave activities has shown insignificant changes in the bed structure after 2002. In 2015–2017 analysis of the bottom sediments types’ distribution at 45 control stations has reaffirmed the stability in all 10 orographic stretches (reaches). Increase of the stations’ number will make more complicated the bottom sediments distribution mosaic and will not significantly change their spatial/temporal transformation found during the first years of the reservoir functioning. We have found that at the current stage the reservoir soil complex is represented by coarsegrained deposits (44%), fine-grained sediments (42%), diffused rocks (13%) and waterlogged soils 91%) located near the floodplain islands of the Kazan and Chistopol regions of variable backwater. The organic matter and biogenic elements content is at the level typical for the plain reservoirs’ bottom sediments. The Kuybyshev Reservoir level of heavy metals pollution in the Volga cascade system has been estimated as low.

Analysis of Navigation Safety Regarding Tankers in Narrow Waterways

Sailing of tanker ships in specific navigation areas, such as narrow waterways, is a particularly delicate navigational venture, where one of the greatest related risks is grounding. Grounding of a tanker in a narrow waterway is an event that can cause many adverse consequences, the most important among them being environmental pollution, explosion or onboard fire damaging the ship, injuries and lost lives of crewmembers. Factors affecting the safety of tanker navigation in narrow waterways can be principally divided into geometric, traffic, meteorological and oceanological factors, ship design factors and marine equipment faults as well as human-related factors. With a view to minimizing the possibility of grounding or contact, the assessment of risks is to be considered indispensable and primarily aimed at influencing accident probability and/or consequence factors as its most important objective. The paper analyses the safety of tanker navigation in narrow waterways based on the assessment of risk of grounding. The event influential probability factors that are taken into consideration comprise the narrow waterway category, meteorological and oceanological conditions, traffic density and VTS coverage of the navigable area, while factors such as ship speed, bottom type, hull quality and loading condition are factors related to consequences. Using the risk assessment matrix, estimated values used for evaluation of the safety of tanker navigation in narrow waterways are assigned to probability factors and factors of consequences.

Assessment of empirical algorithms for bathymetry extraction using Sentinel-2 data

ABSTRACTBathymetry estimated from optical satellite imagery has been increasingly implemented as an alternative to traditional bathymetric survey techniques. The availability of new sensors such as Sentinel-2 with improved spatial and temporal resolution, in comparison with previous optical sensors, offers innovative capabilities for bathymetry derivation. This study presents an assessment of the fit between satellite data and the underlying models in the most widely used empirical algorithms: the linear band model and the log-transformed band ratio model using Sentinel-2A data. Both models were tested in two study areas of the Irish coast with different morphological and environmental conditions. Results showed that the linear band model fitted better than the log-transformed band ratio model providing coefficient of determination values, R2, between 0.83 and 0.88 (0 m–10 m) for the five images considered in the study. The closest fit was found in the depth range 2 m–6 m. Atmospheric correction, bottom type influence, and water column conditions proved to be key factors in the bathymetric derivation using these satellite datasets.

Multiple Optimal Depth Predictors Analysis (MODPA) for river bathymetry: Findings from spectroradiometry, simulations, and satellite imagery

Remote mapping of bathymetry can play a key role in gaining spatial and temporal insight into fluvial processes, ranging from hydraulics and morphodynamics to habitat conditions. This research introduces Multiple Optimal Depth Predictors Analysis (MODPA), which combines previously developed depth predictors along with additional predictors derived from the intensity component of the HSI color space transformation. MODPA empirically selects a set of optimal predictors among all candidates utilizing partial least squares (PLS), stepwise, or principal component (PC) regression models. The primary focus of this study was on shallow (<1 m deep) and clearly flowing streams where substrate variability could have a pronounced effect on depth retrieval. Spectroscopic experiments were performed under controlled conditions in a hydraulic laboratory to examine the robustness of bathymetry models with respect to changes in bottom type. Further, simulations from radiative transfer modeling were used to extend the analysis by isolating the effect of inherent optical properties (IOPs) and by investigating the performance of bathymetry models in optically complex and deeper streams. The bathymetry of the Sarca River, a shallow river in the Italian Alps, was mapped using a WorldView-2 (WV-2) image, for which we evaluated the atmospheric compensation (AComp) product. Results indicated the greater robustness of multiple-predictor models particularly MODPA rather than single-predictor models, such as Optimal Band Ratio Analysis (OBRA), with respect to heterogeneity of bottom types, IOPs, and atmospheric effects. The HSI intensity component enhanced the accuracy of depth retrieval, particularly in optically-complex waters and also for low spectral resolution imagery (e.g., GeoEye). Further, the enhanced spectral resolution of WV-2 imagery improved bathymetry retrieval compared to 4-band GeoEye data.

Dynamic occupancy modeling of temperate marine fish in area-based closures.

Species distribution models (SDMs) are commonly used to model the spatial structure of species in the marine environment, however, most fail to account for detectability of the target species. This can result in underestimates of occupancy, where nondetection is conflated with absence. The site occupancy model (SOM) overcomes this failure by treating occupancy as a latent variable of the model and incorporates a detection submodel to account for variability in detection rates. These have rarely been applied in the context of marine fish and never for the multiseason dynamic occupancy model (DOM). In this study, a DOM is developed for a designated species of concern, cusk (Brosme brosme), over a four‐season period. Making novel use of a high‐resolution 3‐dimensional hydrodynamic model, detectability of cusk is considered as a function of current speed and algae cover. Algal cover on the seabed is measured from video surveys to divide the study area into two distinct regions: those with canopy forming species of algae and those without (henceforth bottom types). Modeled estimates of the proportion of sites occupied in each season are 0.88, 0.45, 0.74, and 0.83. These are significantly greater than the proportion of occupied sites measured from underwater video observations which are 0.57, 0.28, 0.43, and 0.57. Individual fish are detected more frequently with increasing current speed in areas lacking canopy and less frequently with increasing current speed in areas with canopy. The results indicate that, where possible, SDM studies for all marine species should take account of detectability to avoid underestimating the proportion of sites occupied at a given study area. Sampling closed areas or areas of conservation often requires the use of nonphysical, low impact sampling methods like camera surveys. These methods inherently result in detection probabilities less than one, an issue compounded by time‐varying features of the environment that are rarely accounted for marine studies. This work highlights the use of modeled hydrodynamics as a tool to correct some of this imbalance.

Why less complexity produces better forecasts: an independent data evaluation of kelp habitat models

Understanding how species are distributed in the environment is increasingly important for natural resource management, particularly for keystone and habitat – forming species, and those of conservation concern. Habitat suitability models are fundamental to developing this understanding; however their use in management continues to be limited due to often‐vague model objectives and inadequate evaluation methods. Along the Northeast Pacific coast, canopy kelps (Macrocystis pyrifera and Nereocystis luetkeana) provide biogenic habitat and considerable primary production to nearshore ecosystems. We investigated the distribution of these species by examining a series of increasingly complex habitat suitability models ranging from process‐based models based on species’ ecology to complex generalised additive models applied to purpose‐collected survey data. Seeking empirical limits to model complexity, we explored the relationship between model complexity and forecast skill, measured using both cross‐validation and independent data evaluation. Our analysis confirmed the importance of predictors used in models of coastal kelp distributions developed elsewhere (i.e. depth, bottom type, bottom slope, and exposure); it also identified additional important factors including salinity, and potential interactions between exposure and salinity, and slope and tidal energy. Comparative results showed how cross‐validation can lead to over‐fitting, while independent data evaluation clearly identified the appropriate model complexity for generating habitat forecasts. Our results also illustrate that, depending on the evaluation data, predictions from simpler models can out‐perform those from more complex models. Collectively, the insights from evaluating multiple models with multiple data sets contribute to the holistic assessment of model forecast skill. The continued development of methods and metrics for evaluating model forecasts with independent data, and the explicit consideration of model objectives and assumptions, promise to increase the utility of model forecasts to decision makers.

Distribution of minor metallic elements within waste incineration bottom ashes defined by WDX/EDX spectrometry

Abstract. A number of metallic elements are inherited from waste during thermal treatment and concentrated in the incineration residues. Because the major part of the incineration residue mass are bottom ashes (BAs), their study is of great importance from the point of view of their environmental impact or resource potential. The general focus of this study was on the minor metallic elements present in BAs. They co-occurred with main phases and often determined the inherited potential of the material. The analysed residues were produced from municipal and industrial waste. The BAs were studied using spectroscopic methods of chemical microanalysis: energy dispersive X-ray spectrometry (EDX) and wavelength dispersive X-ray spectrometry (WDX). Both the main and minor metallic elements were concentrated in metallic components. They were typically present as separate grains and metallic inclusions (commonly in the glass matrix of the grains) ranging in size from several to hundreds of micrometres. Despite Fe-, Al- and Cu-rich occurrences, metallic elements rarely occurred in fragments composed of a single element. Their main forms of occurrence were alloy grains, admixtures in polymetallic occurrences and micro-inclusions in glassy matrix. The content of particular elements in those forms was investigated and described in greater detail. Even though two types of bottom ash were formed from different types of waste and differences in used technologies were present, the obtained materials contained metallic components having similar attributes. Elevated concentrations of not only Fe and Al, but also Ti, Cu and Zn, allow us to consider bottom ash as a promising material from the point of view of metallic elements' recovery (e.g. by the physical concentration of elements through gravity or magnetic methods).

Habitat complexity affects benthic harmful dinoflagellate assemblages in the fringing reef of Rawa Island, Malaysia

Few studies have investigated the effect of fine-scale habitat differences on the dynamics of benthic harmful dinoflagellate assemblages. To determine how these microhabitat differences affect the distribution and abundance of the major benthic harmful dinoflagellate genera in a tropical coral reef ecosystem, a field study was undertaken between April–September 2015 and January 2016 on the shallow reef flat of the fringing reef of Rawa Island, Terengganu, Malaysia. Sampling of benthic dinoflagellates was carried out using an artificial substrate sampling method (fiberglass screens). Benthic microhabitats surrounding the sampling screens were characterized simultaneously from photographs of a 0.25-m2 quadrat based on categories of bottom substrate types. Five taxonomic groups of benthic dinoflagellates, Ostreopsis, Gambierdiscus, Prorocentrum, Amphidinium, and Coolia were identified, and cells were enumerated using a light microscope. The results showed Gambierdiscus was less abundant than other genera throughout the study period, with maximum abundance of 1.2 × 103 cells 100 cm−2. While most taxa were present on reefs with high coral cover, higher cell abundances were observed in reefs with high turf algal cover and coral rubble, with the exception of Ostreopsis, where the abundance reached a maximum of 3.4 × 104 cells 100 cm−2 in habitats with high coral cover. Microhabitat heterogeneity was identified as a key factor governing the benthic harmful dinoflagellate assemblages and may account for much of the observed variability in dominant taxa. This finding has significant implications for the role of variability in the benthic harmful algal bloom (BHAB) outbreaks and the potential in identifying BHAB-related toxin transfer pathways and the key vectors in the food webs.

Organic Matter, Textures, and Pore Attributes of Hypersaline Lacustrine Microbial Deposits (Holocene, Bahamas)

Research Article| July 31, 2018 Organic Matter, Textures, and Pore Attributes of Hypersaline Lacustrine Microbial Deposits (Holocene, Bahamas) Hannah L. Hubert; Hannah L. Hubert Kansas Interdisciplinary Carbonates Consortium, Department of Geology, University of Kansas, Lawrence, Kansas 66045, U.S.A. Search for other works by this author on: GSW Google Scholar Eugene C. Rankey; Eugene C. Rankey Kansas Interdisciplinary Carbonates Consortium, Department of Geology, University of Kansas, Lawrence, Kansas 66045, U.S.A. Search for other works by this author on: GSW Google Scholar Christopher Omelon Christopher Omelon Kansas Interdisciplinary Carbonates Consortium, Department of Geology, University of Kansas, Lawrence, Kansas 66045, U.S.A. Search for other works by this author on: GSW Google Scholar Journal of Sedimentary Research (2018) 88 (7): 827–849. https://doi.org/10.2110/jsr.2018.42 Article history first online: 31 Jul 2018 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Tools Icon Tools Get Permissions Search Site Citation Hannah L. Hubert, Eugene C. Rankey, Christopher Omelon; Organic Matter, Textures, and Pore Attributes of Hypersaline Lacustrine Microbial Deposits (Holocene, Bahamas). Journal of Sedimentary Research 2018;; 88 (7): 827–849. doi: https://doi.org/10.2110/jsr.2018.42 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search nav search search input Search input auto suggest search filter All ContentBy SocietyJournal of Sedimentary Research Search Advanced Search Abstract Discovery of lacustrine microbialite reservoirs in South Atlantic pre-salt has motivated the search for analogs for perspectives on their deposition and initial porosity. Although previous efforts mapped spatial patterns and produced facies models of large microbial lacustrine systems, details of the origins of microbialite fabrics are less well constrained. To address these unknowns, this study evaluates the influence of organic-matter source, abundance, and growth habit on Holocene microbialite fabrics. Integrated multi-scale analyses characterize fabrics of Holocene microbialites in a small (< 1 km2), shallow (< 1 m), hypersaline, alkaline lake on Crooked–Acklins Platform in the southern Bahamas. The results of analyses indicate systematic distribution of surface sediment across the lake, from various types of unlithified microbial mats to calcareous microbialites; bottom type relates to water depth. Spherules with laminae of radial aragonite are common in organic-rich mats, and can have competitive growth boundaries. Calcareous microbialites in the lake center can reach up to 60 cm tall and 2+ m across, and include macrofabrics and microfabrics that vary considerably, across micrometer to meter scales. Porosity varies from 43 to 59%, in pore types ranging from intra-fibrous (IF), breccia (BR), vuggy (VUG), intra- (WL) and inter-laminar (IL), digitate (DG), to branching (BRA). Microfabrics are not unique to individual macrofabrics, and organic-matter source is similar among fabrics. The abundance of organic matter and growth habit of organics on the outer parts of microbialites varies markedly among fabrics, suggesting that these parameters may control rock fabric. The occurrence of Mg silicates in association with these microbialites may favor preservation of the depositional pores. Although ultimate preservation is unknown, understanding the genesis of primary fabrics may provide insights into possible pore evolution in reservoir analogs. You do not currently have access to this article.

Coral reef applications of Sentinel-2: Coverage, characteristics, bathymetry and benthic mapping with comparison to Landsat 8

The Sentinel-2A and 2B Multi-Spectral Instrument (MSI) offers a specification of potential value toward a number of objectives in remote sensing of coral reefs. Coral reefs represent a unique challenge for remote sensing, being highly heterogeneous at metre scales and occurring at variable depths and water clarity regimes. However, conservation initiatives, such as the United Nations Sustainable Development Goals, add urgency to the need for the large scale environmental monitoring information that remote sensing can provide. In the quest to meet this challenge a range of satellite instruments have been leveraged, from Landsat to high spatial resolution sensors such as WorldView-2, toward objectives such as: mapping of bottom types, bathymetry, change detection, and detection of coral bleaching events. Sentinel-2A and 2B offer a new paradigm of available instruments, with a 5-day revisit, 10 m multispectral spatial resolution and freely available data. Pre-launch simulation analyses by several of the authors suggested Sentinel-2 would have good performance for reef applications, in this paper we follow up on this study by reviewing the potential based on the substantial archive of actual data now available.First we determine to what extent the World's reefs are covered by Sentinel-2, since the mission requirements do not by default include all reefs. Secondly we review how a 5-day revisit translates to a usable acquisition rate of clear images, given that cloud and surface glint are common confounding factors. The usable acquisition rate is the real determinant of the objectives to which the data can be applied. Finally we apply current processing algorithms to Sentinel-2 data of several sites over the Great Barrier Reef, including physics-based bathymetry inversion and object-orientated benthic mapping. Landsat 8 OLI is most comparable current sensor to Sentinel-2 MSI, so direct comparisons and the possibilities for data synthesis are explored.Our findings confirm that Sentinel-2 has excellent performance for meeting several essential coral reef scientific and monitoring objectives. Taking into account cloud and sun glint, the usable acquisition rate for a large proportion of reefs is likely to be around 20 clear images a year on average, giving a new potential for evaluation of short time-scale disturbances and impacts. The spatial resolution of 10 m is a key threshold for delineating benthic features of interest such as coral structures, and there is evidence from image and field data that bleaching is detectable. Radiometrically Sentinel-2 data can support good results in physics-based methods, such as bathymetric mapping, comparable to Landsat 8 and WorldView-2. In addition the large scale acquisition area, provided by the 290 km wide swath, offers advantages over high spatial resolution imagery for mapping at multi-reef scales.Sentinel-2 data can be immediately leveraged with existing methods, to provide a new level of reef monitoring information compared to that previously available by remote sensing. Combined with Landsat 8 and the historical Landsat archive, the data collected today will be invaluable for decades or even centuries to come. In this context, the main downside of the Sentinel-2 mission is that approximately 12% of the World's reefs currently lie outside the acquisition plan and are not imaged. Surprisingly, for a European initiative, coral reefs in European governed territories are among the worst served globally. These omissions, approximately only 1/200th of the currently imaged area, limit the global scope which otherwise would be one of Sentinel-2's greatest strengths.

Spatio-Temporal Assessment of Gully Erosion in the Zone of Intensive Agriculture in the European Part of Russia

Using the method of mapping by high resolution satellite imagery mapping, a study was made of the key areas which are located in the southern part of the forest, forest-steppe and steppe zones of Tatarstan and of Orenburg, Saratov and Voronezh oblasts. Two key indicators were determined: the gully length density and gully head density within the basins; results of the investigation were used in compiling respective maps in vector format. It is established that the density of the gully length in the basins varies over the range from 0 to 0.5 km/km2 (from the absence of gullies to strong gully erosion), and the density of gully heads from 0 to 3 units/km2. The slope type of gullies is dominant in all basins (about 80%), while the coastal and bottom types have approximately the same proportion (14 and 10%, respectively). Using methods of mathematical statistics we determined a high directly proportional dependence of the indicators of the contemporary gully network on the level of ploughness of the basins and the mean annual precipitation amount, and an indirectly proportional dependence on the level of sodding. An abrupt reduction in gullying indicators was determined. It was found that among the chief reasons behind an abrupt reduction in the gullies to date is a decrease of the rate of agricultural development, with an additional factor, namely, a dramatic decrease in surface runoff down the arable slopes during spring snowmelt caused by climate warming. It is concluded that that a significant part of the gully forms in the study area is currently inactive and massively passes into the balka stage.

Deriving Bathymetric Maps of the Shallow Coastal Water of the Gaza Strip Coastal Zone Using Passive Remotely Sensed Imagery

Bathymetry, the mapping of the shape of the surface of the seafloor, is a necessary science for coastal populations that rely heavily on the marine ecosystem for their survival and prosperity. Bathymetric maps are typically derived through a sound or light remote sensing system that is mounted on a boat or airplane that sweeps the designated study area. However, in regions with political constraints or logistical difficulties, reaching the study area and conducting in situ measurements can be difficult or impossible. Thus, using passive satellite imaging can be an alternative approach to traditional hydrographic surveying methods. As bathymetric maps are influenced by the local sea water conditions, the bottom type, and the water constituents, choosing a derivation algorithm for the satellite images which results in a robust and accurate map is very important. In this study, QuickBird imagery was selected to investigate the functionality and the accuracy of two different bathymetric derivation algorithms to obtain robust and reliable maps of the Gaza Strip coastal zone. Despite the high pollution level in the seawater of the investigated area, the findings confirmed the feasibility of obtaining reasonable accurate bathymetric maps.

What happens after mussels die? Biogenic legacy effects on community structure and ecosystem processes

Mussels are well-known ecosystem engineers in soft-bottom systems. Mytilus edulis beds have myriad effects on sediment, benthic organisms, and ecosystem processes such as hydrodynamic transport of sediment and animals. When mussels die, they may leave behind massive amounts of whole (empty) and fragmented shells. The legacy effects of this long-lasting biogenic material (i.e., shell hash) on benthic systems are poorly understood. We measured percent cover values of 4 bottom cover types, i.e., live mussels, whole shells, fragmented shells, and bare sediment, at the mussel bed in Carrying Place Cove, Harrington, Maine, USA, and examined their effects on sediment characteristics, community structure of macrofauna and meiofauna, and ecosystem processes of sediment flux and dispersal of postlarval macrofauna and meiofauna. We predicted that live mussels are the cover type with the greatest effects compared to bare sediment, followed by fragmented shells and then whole shells. We discovered mostly bare sediment, substantial cover of whole and fragmented shells, and almost no live mussels in what had in past years been a robust bed. We found significant univariate and multivariate differences in sediment and animals across cover types, especially for meiofauna. Fragmented shell material in particular may be an important driver in this system. Our results are the first to quantify the 4 mussel bed cover types and demonstrate their effects. Mussel beds in the Gulf of Maine have experienced severe declines in the past two decades, attributed primarily to climate change and the invasive green crab, Carcinus maenas. Our results may be useful in predicting the responses of soft-bottom systems as intact mussel beds die off, leaving large areas of bare sediment and shell hash.

Effect of IrO2/Pt, IrO2, and Pt bottom electrodes on the structure and electrical properties of PZT based piezoelectric microelectromechanical system devices

In piezoelectric microelectromechanical system devices with PbZr x Ti1−xO3 as the ferroelectric, the bottom electrode can provide a template for oriented PbZr x Ti1−xO3 growth. IrO2/Pt, IrO2, and Pt bottom electrode layers were sputter deposited onto TiO2 and were used as growth templates for oriented PbZr0.52Ti0.48O3 growth. The IrO2 and Pt were found to be {100}- and {111}-oriented, respectively, by X-ray diffraction. Scanning/transmission electron microscopy results indicate that the bottom electrodes are textured; however, the PbZr0.52Ti0.48O3 layer is partially textured. The impact of the bottom electrode type on the electrical properties is investigated by dielectric, ferroelectric, and piezoelectric measurements on circular capacitors formed on blanket PbZr0.52Ti0.48O3 films and unimorph cantilevers. For devices with PbZr0.52Ti0.48O3 on IrO2/Pt bottom electrodes, values for the dielectric constant of 1103 ± 28, loss tangent of 0.070 ± 0.004, maximum polarization of 0.399 ± 0.003 C/m2 at 38 MV/m, and leakage current of 5.4 ± 5.8 nA at 20 MV/m were obtained. Values of normalized strain of 0.0030 ± 0.0001 at 20 MV/m, and effective piezoelectric coefficient, d31,f, of 100 ± 25 pm/V at 15 MV/m were obtained on cantilever unimorphs with electrode area 16 µm × 123 µm and PZT area 16 µm × 125 µm. These values are comparable to results obtained for PbZr0.52Ti0.48O3 on 100 nm thick Pt-only bottom electrodes.

NOTES ON THE DISTRIBUTION OF RED ALGAE (RHODOPHYTA) ON THE CORAL REEF OF PARI ISLANDS, SERIBU ISLANDS

Many species of red algae are economically important for their carrageenan contents. Since May 1974 to June 1975 an intensive survey on their distributions have been carried out on the fringing reef of Pari Islands, Seribu Islands. Thirty five species of Rhodophyta have been identified and their species composition and relative importance as compared to Phaeophyta and Chlorophyta have been studied. Environmental factors, such as bottom type and seasonal influence on their distribution, emphasized in the discussion. Further studies on inventory and the distribution of these algae will be continued particularly in support of the culture experiments for some of the species.