1000 resultados para marginal impacts


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It is shown in this paper that the laws of cratering in a thick target under hypervelocity impact by a spherical projectile can be approximately expressed by the so-called iso-deviation law and a 2/3 power law. Moreover, hypervelocity impact should be characterized by the isotropic expansion of a crater. In the special case, when the projectile and target are of the same material, the laws mentioned above reduce to the result of a semi-spherical crater and the energy criterion. Generally speaking, a semi-spherical crater and the energy criterion are both approximations, which only take projectile density and target strength into account, and can be used for a rough estimation on the order of magnitude. The inconsistency in various fitted power laws in the literature was also clarified and explained in the paper.

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The bibliography is to highlight impacts on fisheries and livelihoods attributed to coral reef marine protected areas in Pacific Island countries and territories. Included in this collection is literature that reports various forms of reef area management practiced in Pacific Island countries: reserves, sanctuaries, permanent or temporary closed areas, community and traditional managed areas. (Document contains 36 pages)

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Angler creel surveys and economic impact models were used to evaluate potential expansion of aquatic vegetation in Lakes Murray and Moultrie, South Carolina. (PDF contains 4 pages.)

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Four methods to control the smooth cordgrass Spartina (Spartina alterniflora) and the footwear worn by treatment personnelat several sites in Willapa Bay, Washington were evaluatedto determine the non-target impacts to eelgrass (Zostera japonica). Clone-sized infestations of Spartina were treated bymowing or a single hand-spray application of Rodeo® formulatedat 480 g L-1acid equivalence (ae) of the isopropylaminesalt of glyphosate (Monsanto Agricultural Co., St. Louis, MO;currently Dow AgroSciences, Indianapolis, IN) with the nonionic surfactant LI 700® (2% v/v) or a combination of mowing and hand spraying. An aerial application of Rodeo® with X-77 Spreader® (0.13% v/v) to a 2-ha meadow was also investigated. Monitoring consisted of measuring eelgrass shoot densities and percent cover pre-treatment and 1-yr post-treatment. Impacts to eelgrass adjacent to treated clones were determined 1 m from the clones and compared to a control 5-m away. Impacts from footwear were assessed at 5 equidistant intervals along a 10-m transect on mudflat and an untreated control transect at each of the three clone treatment sites. Impacts from the aerial application were determined by comparing shoot densities and percent cover 1, 3 and 10 m from the edge of the treated Spartina meadow to that at comparable distances from an untreated meadow. Methods utilized to control Spartina clones did not impact surrounding eelgrass at two of three sites. Decreases in shoot densities observed at the third site were consistent across treatments. Most impacts to eelgrass from the footwear worn by treatment personnel were negligible and those that were significant were limited to soft mud substrate. The aerial application of the herbicide was associated with reductions in eelgrass (shoot density and percent cover) at two of the three sampling distances, but reductions on the control plot were greater. We conclude that the unchecked spread of Spartina is a far greater threat to the survival and health of eelgrass than that from any of the control measures we studied. The basis for evaluating control measures for Spartina should be efficacy and logistical constraints and not impacts to eelgrass. PDF is 7 pages.

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In clear water, diquat [6,7-dihydrodipyrido (1,2-1a:2',1'-c) pyrazinediium dibromide] provides excellent submersed Plant control at low concentrations, such as <0.5 mg active ingredient (ai) L-1: however. turbid water conditions can interfere with the activity and effectiveness of this herbicide. Little work has been done to examine what ranges of turbidity caused by different Suspended sediment types affect diquat efficacy against a target species. A growth chamber study was conducted rising diquat against the submersed macrophyte -egeria (Egeria densa Planch.) under a range Of turbid conditions. Two materials were used to create turbid beater conditions: 100% bentonite clay for a "worst-case" scenario and a natural partial-clav (20% clay). Results indicated that a high rate of diquat (2 mg ai L-1) controlled egeria under relatively low levels of turbidity (5-10 NTU) using bentonite clay: however. higher levels (25 to 50 NTU) of turbidity essentially blocked effectiveness of diquat when applied at all rates tested (0.5. 1, 2 mg ai L-1). When using a natural partial-clay sediment, rates of 1 to 2 mg ai L-1 diquat provided good control of egeria in moderately turbid water (15 NTU). Additional evaluations rising different clay types would be useful to determine the effect of inorganic turbidity oil diquat efficacy.

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We examined the impacts of mechanical shredding (i.e.. shredding plants and leaving biomass in the system) of the water chestnut (Trapa natans) on water quality and nutrient mobilization in a control and experimental site in Lake Champlain (Vermont-New York). A 1-ha plot was mechanically shredded within 1 h on 26 July, 1999. Broken plant material was initially concentrated on the lake surface of the experimental station after shredding, and was noticeable on the lake surface for 19 d. Over a two week period after shredding. concentrations of total nitrogen (N) and phosphorus (P), and soluble reactive P increased in the lower water column of the experimental station, coinciding with decomposition of water chestnut. Sediments in the control and experimental stations exhibited vet-v low rates of N and P release and could not account for increases in nutrient concentrations in the water column after mechanical shredding. Shredded plant material deployed in mesh bags at the experimental station lost similar to 70% of their total mass, and 42%, N and 70% P within 14 d. indicating Substantial nutrient mobilization via autolysis and decomposition. Chlorophyll a concentrations increased to 35 g/L at the experimental station on day 7 after shredding, compared to a concentration of 4 g/L at the control station. suggesting uptake of mobilized nutrients by phytoplankton. Disruption Of the Surface canopy of water chestnut by shredding was associated with marked increases in turbidity and dissolved oxygen, suggesting increased mixing at the experimental site.

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Foreword [pdf, < 0.1 MB] Acknowledgements PHASE 1 [pdf, 0.2 MB] Summary of the PICES/NPRB Workshop on Forecasting Climate Impacts on Future Production of Commercially Exploited Fish and Shellfish (July 19–20, 2007, Seattle, U.S.A.) Background Links to Other Programs Workshop Format Session I. Status of climate change scenarios in the PICES region Session II. What are the expected impacts of climate change on regional oceanography and what are some scenarios for these drivers for the next 10 years? Session III. Recruitment forecasting Session IV. What models are out there? How is climate linked to the model? Session V. Assumptions regarding future fishing scenarios and enhancement activities Session VI Where do we go from here? References Appendix 1.1 List of Participants PHASE 2 [pdf, 0.7 MB] Summary of the PICES/NPRB Workshop on Forecasting Climate Impacts on Future Production of Commercially Exploited Fish and Shellfish (October 30, 2007, Victoria, Canada) Background Workshop Agenda Forecast Feasibility Format of Information Modeling Approaches Coupled bio-physical models Stock assessment projection models Comparative approaches Similarities in Data Requests Opportunities for Coordination with Other PICES Groups and International Efforts BACKGROUND REPORTS PREPARED FOR THE PHASE 2 WORKSHOP Northern California Current (U.S.) groundfish production by Melissa Haltuch Changes in sablefish (Anoplopoma fimbria) recruitment in relation to oceanographic conditions by Michael J. Schirripa Northern California Current (British Columbia) Pacific cod (Gadus macrocephalus) production by Caihong Fu and Richard Beamish Northern California Current (British Columbia) sablefish (Anoplopoma fimbria) production by Richard Beamish Northern California Current (British Columbia) pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon production by Richard Beamish Northern California Current (British Columbia) ocean shrimp (Pandalus jordani) production by Caihong Fu Alaska salmon production by Anne Hollowed U.S. walleye pollock (Theragra chalcogramma) production in the eastern Bering Sea and Gulf of Alaska by Kevin Bailey and Anne Hollowed U.S. groundfish production in the eastern Bering Sea by Tom Wilderbuer U.S. crab production in the eastern Bering Sea by Gordon H. Kruse Forecasting Japanese commercially exploited species by Shin-ichi Ito, Kazuaki Tadokoro and Yasuhiro Yamanka Russian fish production in the Japan/East Sea by Yury Zuenko, Vladimir Nuzhdin and Natalia Dolganova Chum salmon (Oncorhynchus keta) production in Korea by Sukyung Kang, Suam Kim and Hyunju Seo Jack mackerel (Trachurus japonicus) production in Korea by Jae Bong Lee and Chang-Ik Zhang Chub mackerel (Scomber japonicus) production in Korea by Jae Bong Lee, Sukyung Kang, Suam Kim, Chang-Ik Zhang and Jin Yeong Kim References Appendix 2.1 List of Participants PHASE 3 [pdf, < 0.1 MB] Summary of the PICES Workshop on Linking Global Climate Model Output to (a) Trends in Commercial Species Productivity and (b) Changes in Broader Biological Communities in the World’s Oceans (May 18, 2008, Gijón, Spain) Appendix 3.1 List of Participants Appendix 3.2 Workshop Agenda (Document contains 101 pages)

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Environmental studies of power plants have recently shifted their emphasis from examination of the effects of heated discharges to studies of the impacts of entire cooling systems. One of the major impacts arises when planktonic organisms are carried into and through a plant with the cooling water. Because of their relatively immobile, free-floating character, planktonic organisms are highly vulnerable to being "entrained" or passively drawn into the cooling water condenser systems of power plants. More than 70% of estuarine animals have planktonic eggs and larvae. The environmental impact of entrainment is related to the composition and abundance of affected organisms, the numbers of organisms in the adjacent waters, survival rates during entrainment as related to natural survival, the ecological roles of entrained organisms, and their reproductive strategies.

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A study was conducted to assess the status of ecological condition and potential human-health risks in subtidal estuarine waters throughout the North Carolina National Estuarine Research Reserve System (NERRS) (Currituck Sound, Rachel Carson, Masonboro Island, and Zeke’s Island). Field work was conducted in September 2006 and incorporated multiple indicators of ecosystem condition including measures of water quality (dissolved oxygen, salinity, temperature, pH, nutrients and chlorophyll, suspended solids), sediment quality (granulometry, organic matter content, chemical contaminant concentrations), biological condition (diversity and abundances of benthic fauna, fish contaminant levels and pathologies), and human dimensions (fish-tissue contaminant levels relative to human-health consumption limits, various aesthetic properties). A probabilistic sampling design permitted statistical estimation of the spatial extent of degraded versus non-degraded condition across these estuaries relative to specified threshold levels of the various indicators (where possible). With some exceptions, the status of these reserves appeared to be in relatively good to fair ecological condition overall, with the majority of the area (about 54%) having various water quality, sediment quality, and biological (benthic) condition indicators rated in the healthy to intermediate range of corresponding guideline thresholds. Only three stations, representing 10.5% of the area, had one or more of these indicators rated as poor/degraded in all three categories. While such a conclusion is encouraging from a coastal management perspective, it should be viewed with some caution. For example, although co-occurrences of adverse biological and abiotic environmental conditions were limited, at least one indicator of ecological condition rated in the poor/degraded range was observed over a broader area (35.5%) represented by 11 of the 30 stations sampled. In addition, the fish-tissue contaminant data were not included in these overall spatial estimates; however, the majority of samples (77% of fish that were analyzed, from 79%, of stations where fish were caught) contained inorganic arsenic above the consumption limits for human cancer risks, though most likely derived from natural sources. Similarly, aesthetic indicators are not reflected in these spatial estimates of ecological condition, though there was evidence of noxious odors in sediments at many of the stations. Such symptoms reflect a growing realization that North Carolina estuaries are under multiple pressures from a variety of natural and human influences. These data also suggest that, while the current status of overall ecological condition appears to be good to fair, long-term monitoring is warranted to track potential changes in the future. This study establishes an important baseline of overall ecological condition within NC NERRS that can be used to evaluate any such future changes and to trigger appropriate management actions in this rapidly evolving coastal environment. (PDF contains 76 pages)

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A study was conducted, in association with the Sapelo Island and North Carolina National Estuarine Research Reserves (NERRs), to evaluate the impacts of coastal development on sentinel habitats (e.g., tidal creek ecosystems), including potential impacts to human health and well-being. Uplands associated with southeastern tidal creeks and the salt marshes they drain are popular locations for building homes, resorts, and recreational facilities because of the high quality of life and mild climate associated with these environments. Tidal creeks form part of the estuarine ecosystem characterized by high biological productivity, great ecological value, complex environmental gradients, and numerous interconnected processes. This research combined a watershed-level study integrating ecological, public health and human dimension attributes with watershed-level land use data. The approach used for this research was based upon a comparative watershed and ecosystem approach that sampled tidal creek networks draining developed watersheds (e.g., suburban, urban, and industrial) as well as undeveloped sites. The primary objective of this work was to clearly define the relationships between coastal development with its concomitant land use changes and non-point source pollution loading and the ecological and human health and well-being status of tidal creek ecosystems. Nineteen tidal creek systems, located along the southeastern United States coast from southern North Carolina to southern Georgia, were sampled during summer (June-August), 2005 and 2006. Within each system, creeks were divided into two primary segments based upon tidal zoning: intertidal (i.e., shallow, narrow headwater sections) and subtidal (i.e., deeper and wider sections), and watersheds were delineated for each segment. In total, we report findings on 24 intertidal and 19 subtidal creeks. Indicators sampled throughout each creek included water quality (e.g., dissolved oxygen concentration, salinity, nutrients, chlorophyll-a levels), sediment quality (e.g., characteristics, contaminants levels including emerging contaminants), pathogen and viral indicators, and abundance and genetic responses of biological resources (e.g., macrobenthic and nektonic communities, shellfish tissue contaminants, oyster microarray responses). For many indicators, the intertidally-dominated or headwater portions of tidal creeks were found to respond differently than the subtidally-dominated or larger and deeper portions of tidal creeks. Study results indicate that the integrity and productivity of headwater tidal creeks were impaired by land use changes and associated non-point source pollution, suggesting these habitats are valuable early warning sentinels of ensuing ecological impacts and potential public health threats. For these headwater creeks, this research has assisted the validation of a previously developed conceptual model for the southeastern US region. This conceptual model identified adverse changes that generally occurred in the physical and chemical environment (e.g., water quality indicators such as indicator bacteria for sewage pollution or sediment chemical contamination) when impervious cover levels in the watershed reach 10-20%. Ecological characteristics responded and were generally impaired when impervious cover levels exceed 20-30%. Estimates of impervious cover levels defining where human uses are impaired are currently being determined, but it appears that shellfish bed closures and the flooding vulnerability of headwater regions become a concern when impervious cover values exceed 10-30%. This information can be used to forecast the impacts of changing land use patterns on tidal creek environmental quality as well as associated human health and well-being. In addition, this study applied tools and technologies that are adaptable, transferable, and repeatable among the high quality NERRS sites as comparable reference entities to other nearby developed coastal watersheds. The findings herein will be of value in addressing local, regional and national needs for understanding multiple stressor (anthropogenic and human impacts) effects upon estuarine ecosystems and response trends in ecosystem condition with changing coastal impacts (i.e., development, climate change). (PDF contaions 88 pages)

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Summary: The offshore shelf and canyon habitats of the OCNMS (Fig. 1) are areas of high primary productivity and biodiversity that support extensive groundfish fisheries. Recent acoustic surveys conducted in these waters have indicated the presence of hard-bottom substrates believed to harbor unique deep-sea coral and sponge assemblages. Such fauna are often associated with shallow tropical waters, however an increasing number of studies around the world have recorded them in deeper, cold-water habitats in both northern and southern latitudes. These habitats are of tremendous value as sites of recruitment for commercially important fishes. Yet, ironically, studies have shown how the gear used in offshore demersal fishing, as well as other commercial operations on the seafloor, can cause severe physical disturbances to resident benthic fauna. Due to their exposed structure, slow growth and recruitment rates, and long life spans, deep-sea corals and sponges may be especially vulnerable to such disturbances, requiring very long periods to recover. Potential effects of fishing and other commercial operations in such critical habitats, and the need to define appropriate strategies for the protection of these resources, have been identified as a high-priority management issue for the sanctuary. To begin addressing this issue, an initial pilot survey was conducted June 1-12, 2004 at six sites in offshore waters of the OCNMS (Fig. 2, average depths of 147-265 m) to explore for the presence of deep-sea coral/sponge assemblages and to look for evidence of potential anthropogenic impacts in these critical habitats. The survey was conducted on the NOAA Ship McARTHUR-II using the Navy’s Phantom DHD2+2 remotely operated vehicle (ROV), which was equipped with a video camera, lasers, and a manipulator arm for the collection of voucher specimens. At each site, a 0.1-m2 grab sampler also was used to collect samples of sediments for the analysis of macroinfauna (> 1.0 mm), total organic carbon (TOC), grain size, and chemical contaminants. Vertical profiles of salinity, dissolved oxygen (DO), temperature, and pressure were recorded at each site with a small SeaCat conductivity-temperature-depth (CTD) profiler. Niskin bottles attached to the CTD also obtained near-bottom water samples in support of a companion study of microbial indicators of coral health and general ecological condition across these sites. All samples except the sediment-contaminant samples are being analyzed with present project funds. Original cruise plans included a total of 12 candidate stations to investigate (Fig. 3). However, inclement weather and equipment failures restricted the sampling to half of these sites. In spite of the limited sampling, the work completed was sufficient to address key project objectives and included several significant scientific observations. Foremost, the cruise was successful in demonstrating the presence of target deepwater coral species in these waters. Patches of the rare stony coral Lophelia pertusa, more characteristic of deepwater coral/sponge assemblages in the North Atlantic, were observed for the first time in OCNMS at a site in 271 meters of water. A large proportion of these corals consisted of dead and broken skeletal remains, and a broken gorgonian (soft coral) also was observed nearby. The source of these disturbances is not known. However, observations from several sites included evidence of bottom trawl marks in the sediment and derelict fishing gear (long lines). Preliminary results also support the view that these areas are important reservoirs of marine biodiversity and of value as habitat for demersal fishes. For example, onboard examination of 18 bottom-sediment grabs revealed benthic infaunal species representative of 14 different invertebrate phyla. Twenty-eight species of fishes from 11 families, including 11 (possibly 12) species of ommercially important rockfishes, also were identified from ROV video footage. These initial discoveries have sparked considerable interests in follow-up studies to learn more about the spatial extent of these assemblages and magnitude of potential impacts from commercial-fishing and other anthropogenic activities in the area. It is essential to expand our knowledge of these deep-sea communities and their vulnerability to potential environmental risks in order to determine the most appropriate management strategies. The survey was conducted under a partnership between NOAA’s National Centers for Coastal Ocean Science (NCCOS) and National Marine Sanctuary Program (NMSP) and included scientists from NCCOS, OCNMS, and several other west-coast State, academic, private, and tribal research institutions (see Section 4 for a complete listing of participating scientists). (PDF contains 20 pages)

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As more people discover coastal and marine protected areas as destinations for leisure-time pursuits, the task of managing coastal resources while providing opportunities for high quality visitor experiences becomes more challenging. Many human impacts occur at these sites; some are caused by recreation and leisure activities on-site, and others by activities such as agriculture, aquaculture, or residential and economic development in surrounding areas. Coastal management professionals are continually looking for effective ways to prevent or mitigate negative impacts of visitor use. (PDF contains 8 pages) Most coastal and marine protected area managers are challenged with balancing two competing goals—protection of natural and cultural resources and provision of opportunities for public use. In most cases, some level of compromise between the goals is necessary, where one goal constrains or “outweighs” the other. Often there is a lack of clear agreement about the priority of these competing goals. Consequently, while natural resource decisions should ultimately be science-based and objective, such decisions are frequently made under uncertainty, relying heavily upon professional judgment. These decisions are subject to a complex array of formal and informal drivers and constraints—data availability, timing, legal mandate, political will, diverse public opinion, and physical, human, and social capital. This paper highlights assessment, monitoring, and planning approaches useful to gauge existing resource and social conditions, determine feasibility of management actions, and record decision process steps to enhance defensibility. Examples are presented from pilot efforts conducted at the Rookery Bay National Estuarine Research Reserve (NERR) and Ten Thousand Islands National Wildlife Refuge (NWR) in South Florida.

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Didemnum sp. A is a colonial ascidian or “sea squirt” of unknown geographic origin. Colonies of Didemnum sp. A were first documented in U.S. waters in 1993 at Damariscotta River, Maine and San Francisco Bay, California. An alarming number of colonies have since been found at several locations in New England and along the West Coast of the contiguous continental United States. Originally believed to be restricted to artificial structures in nearshore habitats, such as ports and marinas, colonies of Didemnum sp. A have also been discovered on a gravel-pavement habitat on Georges Bank at depths of 40-65m. The wide distribution of Didemnum sp. A, the presence of colonies on an important offshore fishing ground, and the negative economic impacts that other species of noninidigenous ascidians have had on aquaculture operations have raised concerns about the potential impacts of Didemnum sp. A. We reviewed the available information on the biology and ecology of Didemnum sp. A and potentially closely related species to examine the environmental and socioeconomic factors that may have influenced the introduction, establishment and spread of Didemnum sp. A in U.S. waters, the potential impacts of this colonial ascidian on other organisms, aquaculture, and marine fisheries, and the possibility that it will spread to other U.S. waters. In addition, we present and discuss potential management objectives for minimizing the impacts and spread of Didemnum sp. A. Concern over the potential for Didemnum sp. A to become invasive stems from ecological traits that it shares with other invasive species, including the ability to overgrow benthic organisms, high reproductive and population growth rates, ability to spread by colony fragmentation, tolerance to a wide range of environmental conditions, apparent scarcity of predators, and the ability to survive in human dominated habitats. At relatively small spatial scales, species of Didemnum and other nonindigenous ascidians have been shown to alter the abundance and composition of benthic assemblages. In addition, the Canadian aquaculture industry has reported that heavy infestations of nonindigenous ascidians result in increased handling and processing costs. Offshore fisheries may also suffer where high densities of Didemnum sp. A may alter the access of commercially important fish species to critical spawning grounds, prey items, and refugia. Because colonial ascidian larvae remain viable for only 12–24hrs, the introduction and spread of Didemnum sp. A across large distances is thought to be predominantly human mediated; hull fouling, aquaculture, and ballast water. Recent studies suggest that colony growth rates decline when temperatures exceed 21 ºC for 7 consecutive days. Similarly, water temperatures above 8 to 10 ºC are necessary for colony growth; however, colonies can survive extended periods of time below this temperature threshold as an unidentified overwintering form. A qualitative analysis of monthly mean nearshore water temperatures suggest that new colonies of Didemnum will continue to be found in the Northeast U.S., California Current, and Gulf of Alaska LMEs. In contrast, water temperatures become less favorable for colony establishment in subarctic, subtropical, and tropical areas to the north and south of Didemnum’s current distribution in cool temperate habitats. We recommend that the Aquatic Nuisance Species Task Force serve as the central management authority to coordinate State and Federal management activities. Five objectives for a Didemnum sp. A management and control program focusing on preventing the spread of Didemnum sp. A to new areas and limiting the impacts of existing populations are discussed. Given the difficulty of eradicating large populations of Didemnum sp. A, developing strategies for limiting the access of Didemnum sp. A to transport vectors and locating newly established colonies are emphasized. (PDF contains 70 pages)

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Few issues confronting coastal resource managers are as divisive or difficult to manage as regulating the construction of private recreational docks and piers associated with residential development. State resource managers face a growing population intent on living on or near the coast, coupled with an increasing desire to have immediate access to the water by private docks or piers. (PDF contains 69 pages)