PHYSICAL–BIOLOGICAL COUPLING ON OYSTER REEFS: HOW HABITAT STRUCTURE INFLUENCES INDIVIDUAL PERFORMANCE

A large-scale field experiment was conducted to test whether the physical structure of biogenic reef habitat controls physical conditions (hydrodynamics and hydrographics) with subsequent influence on the performance (recruitment, growth, and survival) of a benthic suspension feeder. The experimental system consisted of restored subtidal oyster reefs inhabited by the eastern oyster Crassostrea virginica. To determine whether the size of reefs influences the flow environment and oyster performance, reefs of four heights-tall (2 m), short (1 m), dredged (0.6 m), and low (0.1 m)-were constructed at 3-m water depth in the Neuse River estuary, North Carolina, USA. To test whether oyster performance varies with water depth and hydrographic conditions, tall and short reefs were also constructed at 6-m water depth. Flow speed, sedimentation, temperature, salinity, dissolved oxygen, and the performance of oysters were measured as a function of reef height, position on reef, and water depth over a 10-mo period. Flow speed was found to increase on reefs with reef height and elevation on reefs. Rates of sediment deposition were seasonally highest where flow speed was lowest, at the bases of reefs, and seasonally decreased with increasing water depth. More than 90% of the surface area of low reefs was buried after only 16 mo of exposure in the estuary, indicating that reef height controls habitat quality (and quantity) indirectly through its effect on flow. Short reefs and the bases of tall reefs at 6-m depth were exposed to a total of 26 d of hypoxia/anoxia. No other reef treatment was exposed to >5 d of hypoxia. Physical conditions on experimental reefs had a profound influence on the performance of oysters as the flow environment alone explained 81% of variability in oyster growth and mortality. Recruitment of oysters over a 2-mo period was slightly higher on the front bases than the crests of reefs, but did not vary with reef height or water depth. After 10 mo, the shell growth and condition index of genetically similar, hatchery-raised oysters were greatest on the crests of tall and short reefs, where flow speed and quality of suspended food material were highest, and sediment deposition was lowest. Growth was greatest overall at the crests of tall reefs located at 6-m water depth where flow speed was high, and the numbers of days exposed to hypoxia/anoxia and variation in salinity were lowest. Total percentage mortality of oysters after 10 mo was greater on low reefs located at 3-m depth than on all other reef types and was greater on the bases than crests of tall, short, and dredged reefs. Predation by crabs and fishes accounted for 4-20% of total oyster mortality and showed no pattern across reef treatments. Results of this experiment indicate (1) that the physical structure and location of biogenic habitat controls local physical variables and (2) that, in turn, physical variables, especially flow speed, have a profound influence on the performance of a resident species. Realization that an ecological function of habitat is to indirectly control local population production through physical-biological coupling should improve our ability to conserve, restore, and manage habitat and associated species diversity. Better ecological engineering of restored oyster reef habitat is likely to improve fishery production and help maintain estuarine biodiversity

Conserving oyster reef habitat by switching from dredging and tonging to diver-harvesting

A major cause of the steep declines of American oyster (Crassostrea virginica) fisheries is the loss of oyster habitat through the use of dredges that have mined the reef substrata during a century of intense harvest. Experiments comparing the efficiency and habitat impacts of three alternative gears for harvesting oysters revealed differences among gear types that might be used to help improve the sustainability of commercial oyster fisheries. Hand harvesting by divers produced 25−32% more oysters per unit of time of fishing than traditional dredging and tonging, although the dive operation required two fishermen, rather than one. Per capita returns for dive operations may nonetheless be competitive with returns for other gears even in the short term if one person culling on deck can serve two or three divers. Dredging reduced the height of reef habitat by 34%, significantly more than the 23% reduction caused by tonging, both of which were greater than the 6% reduction induced by diver hand-harvesting. Thus, conservation of the essential habitat and sustainability of the subtidal oyster fishery can be enhanced by switching to diver hand-harvesting. Management schemes must intervene to drive the change in harvest methods because fishermen will face relatively high costs in making the switch and will not necessarily realize the long-term ecological benefits

Assessing Withering Syndrome Resistance in California Black Abalone: Implications for Conservation and Restoration

Our overall research objectives were to (1) assess population trends along San Nicolas Island and in Monterey County; (2) optimize black abalone spawning methods; (3) develop and validate a real-time PCR assay for quantification of RLP loads (infection intensity); and (4) examine if progeny of surviving black abalone along the California islands are more resistant to WS than are animals without this disease pressure. At UCSB we were focused primarily on objective (2). We tested the following hypotheses to fulfill our objectives.Hypothesis 1: Black abalone spawning requires environmental conditions similar to their intertidal and shallow subtidal habitat, and not standard methods that were developed for subtidal species. Hypothesis 2: Quantitative real-time PCR can be used to quantify loads of the WS rickettsial bacterium (infection intensity) in abalone. Hypothesis 3: Juvenile black abalone recruiting along the California Channel Islands are more resistant to WS than are black abalone in northern Central California that have not experienced high disease (WS) selection pressure

Factors influencing the variation in GMS prescribing expenditure in Ireland

Background Pharmaceutical expenditure growth is a familiar feature in many Western health systems and is a real concern for policymakers. A state funded General Medical Services (GMS) scheme in Ireland experienced an increase in prescription expenditure of 414 % between 1998 and 2012. This paper seeks to explore the rationale for this growth by investigating the composition (Anatomical Therapeutic Chemical (ATC) Group level 1 & 5) and drivers of GMS drug expenditure in Ireland in 2012. Methods A cross-sectional study was carried out on the Health Service Executive-Primary Care Reimbursement Service (HSE-PCRS) population prescribing database (n = 1,630,775). Three models were applied to test the association between annual expenditure per claimant whilst controlling for age, sex, region, and the pharmacology of the drugs as represented by the main ATC groups. Results The mean annual cost per claimant was €751 (median = €211; SD = €1323.10; range = €3.27–€298,670). Age, sex, and regions were all significant contributory factors of expenditure, with gender having the greatest impact (β = 0.107). Those aged over 75 (β =1.195) were the greatest contributors to annual GMS prescribing costs. As regards regions, the South has the greatest cost increasing impact. When the ATC groups were included the impact of gender is diluted by the pharmacology of the products, with cardiovascular prescribing (ATC ‘C’) most influential (β = 1.229) and the explanatory power of the model increased from 40 % to 60 %. Conclusion Whilst policies aimed at cost containment (co-payment charges; generic substitution; reference pricing; adjustments to GMS eligibility) can be used to curtail expenditure, health promotional programs and educational interventions should be given equal emphasis. Also policies intended to affect physicians’ prescribing behaviour include guidelines, information (about price and less expensive alternatives) and feedback, and the use of budgetary restrictions could yield savings in Ireland and can be easily translated to the international context

A REVIEW OF 3D GIS FOR USE IN CREATING VIRTUAL HISTORIC DUBLIN

This paper illustrates how BIM integration with GIS is approached as part of the workflow in creating Virtual Historic Dublin. A design for a WEB based interactive 3D model of historic buildings and centres in Dublin City (Virtual Historic Dublin City) paralleling smart city initiates is now under construction and led by the National Monuments at the Office of Public Works in Ireland. The aim is to facilitate the conservation and maintenance of historic infrastructure and fabric and the dissemination of knowledge for education and cultural tourism using an extensive Historic Building Information Model. Remote sensing data is now processed with greater ease to create 3D intelligent models in Historic BIM. While the use of remote sensing, HBIM and game engine platforms are the main applications used at present, 3D GIS has potential to form part of the workflow for developing the Virtual Historic City. 2D GIS is now being replaced by 3D spatial data allowing more complex analysis to be carried out, 3D GIS can define and depict buildings, urban rural centres in relation to their geometry topological, semantic and visualisation properties. The addition of semantic attributes allows complex analysis and 3D spatial queries for modelling city and urban elements. This analysis includes fabric and structural elements of buildings, relief, vegetation, transportation, water bodies, city furniture and land use

HOW HABITAT DEGRADATION THROUGH FISHERY DISTURBANCE ENHANCES IMPACTS OF HYPOXIA ON OYSTER REEFS

Oysters are ecosystem engineers that create biogenic reef habitat important to estuarine biodiversity, benthic-pelagic coupling, and fishery production. Prevailing explanations for the dramatic decline of eastern oysters (Crassostrea virginica) during the last century overlook ecosystem complexity by ignoring interactions among multiple environmental disturbances. To explain oyster loss, we tested whether (1) mortality of oysters on natural oyster reefs varies with water depth (3 m vs. 6 m), (2) harvesting by oyster dredges reduces the height of oyster reefs, and (3) bottom-water hypoxia/anoxia and reduction in reef height through fishery disturbance interact to enhance mortality of oysters in the Neuse River estuary, North Carolina, USA. The percentage of oysters found dead (mean ± 1 SD) during a survey of natural reefs in May 1993 was significantly greater at 6-m (92 ± 10%) than at 3-m (28 ± 9%) water depth. Less than one scason's worth of oyster dredging reduced the height of restored oyster reefs by ∼30%. During stratification of the water column in summer, oxygen depletion near the seafloor at 6 m caused mass mortality of oysters, other invertebrates, and fishes on short, deep experimental reefs, while oysters and other reef associates elevated into the surface layer by sufficient reef height or by location in shallow water survived. Highly mobile blue crabs (Callinectes sapidus) abandoned burrows located in hypoxic/anoxic bottom waters but remained alive in shallow water. Our results indicate that interaction of reef habitat degradation (height reduction) through fishery disturbance and extended bottom-water hypoxia/anoxia caused the pattern of oyster mortality observed on natural reefs and influences the abundance and distribution of fish and invertebrate species that utilize this temperate reef habitat. Interactions among environmental disturbances imply a need for the integrative approaches of ecosystem management to restore and sustain estuarine habitat

AN INITIAL DESIGN FRAMEWORK FOR VIRTUAL HISTORIC DUBLIN

As a single coherent model, the proposed Virtual Historic Dublin City will improve the current approaches for planning, conserving, presenting and interpreting cultural heritage buildings and their environments. The combination of digital recording, modelling and data management systems enable the interaction with complex, interlinked three-dimensional structures containing rich and diverse underlying data. End users can encompass architectural and engineering conservation, education and research, in addition to public engagement and cultural tourism. In this paper a digital design framework is presented, based on state of the art current approaches for recording, modelling and presenting Virtual Historic Dublin. The modelling sites and structures is based on remotely sensed survey data which is processed and modelled in Historic BIM or GIS allowing the addition of semantic attributes. Archiving and storage of both models and knowledge and information attributes requires open systems and server data base capable of handling vector and point cloud information in addition to other digital data. The dissemination and interaction with the models and attached knowledge attributions is based on combining game engine platforms, Historic BIM, Historic GIS and access to compatible storage and data base

Single quantum dot states measured by optical modulation spectroscopy

Using optical modulation spectroscopy, we report the direct observation of absorption lines from excitons localized in GaAs single quantum dot potentials. The data provide a measurement of the linewidth, resonance energy, and oscillator strength of the transitions, and show that states which decay primarily by nonradiative processes can be directly probed using this technique. The experiments establish this technique for the characterization of single quantum dot transitions, thereby complementing luminescence studies. © 1999 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70527/2/APPLAB-75-19-2933-1.pd