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81.
A management proposal aims to partly remove a WWII military causeway at Palmyra Atoll to improve lagoon water circulation and alleviate sedimentation stress on the southeast backreef, an area of high coral cover and diversity. This action could result in a shift in sedimentation across reef sites. To provide management advice, we quantified the proximate environmental factors driving scleractinian coral cover and community patterns at Palmyra. The proportion of fine sedimentation was the optimal predictor of coral cover and changes in community structure, explaining 23.7% and 24.7% of the variation between sites, respectively. Scleractinian coral cover was negatively correlated with increases in fine sedimentation. Removing the causeway could negatively affect the Montipora corals that dominate the western reef terrace, as this genus was negatively correlated with levels of fine sedimentation. The tolerance limits of corals, and sediment re-distribution patterns, should be determined prior to complete removal of the causeway. 相似文献
82.
Sabino R Veríssimo C Cunha MA Wergikoski B Ferreira FC Rodrigues R Parada H Falcão L Rosado L Pinheiro C Paixão E Brandão J 《Marine pollution bulletin》2011,62(7):1506-1511
Whilst the potential impact on beach users from microorganisms in water has received considerable attention, there has been relatively little investigation into microbial contaminants in sand. Thirty three beaches across Portugal were analyzed during a five year period (2006-2010) to determine the presence of yeasts, pathogenic fungi, dermatophytes, total coliforms, Escherichia coli and intestinal enterococci in sand.Our results showed that 60.4% of the samples were positive for fungi and that 25.2% were positive for the bacterial parameters. The most frequent fungal species found were Candida sp. and Aspergillus sp., whereas intestinal enterococci were the most frequently isolated bacteria. Positive associations were detected among analyzed parameters and country-regions but none among those parameters and sampling period.Regarding threshold values, we propose 15 cfu/g for yeasts, 17 cfu/g for potential pathogenic fungi, 8 cfu/g for dermatophytes. Eighty four cfu/g for coliforms, 250 cfu/g for E. coli, and 100 cfu/g for intestinal enterococci. 相似文献
83.
Munari C 《Marine pollution bulletin》2011,62(12):2761-2770
The summer of 2003 was the warmest summer in Europe since the 16th century. Its consequences on the fauna of a transitional ecosystem were studied through biodiversity, functional and ecological indicators, from summer 2002 to winter 2005. The heatwave caused considerable changes in the benthic community structure and relative composition, persisting in 2005. Animal assemblages switched from mollusc- to annelida-dominated. Biodiversity and functional indicators captured changes in community structure and composition, proving to be powerful tools to detect responses related to global warming. Ecological indicators rendered a monotonic response oscillating between bad and poor ecological status across the study period. The resilience of mollusc biocoenosis resulted limited with respect to other taxa, posing concerns about their conservation if, as predicted, the frequency of summers as hot as that of 2003 will progressively increase to become the norm at the end of this century. 相似文献
84.
Paganelli D Forni G Marchini A Mazziotti C Occhipinti-Ambrogi A 《Marine pollution bulletin》2011,62(8):1725-256
According to the European Water Framework Directive, the ecological status (ES) of a water body is determined by comparing observation data with undisturbed Reference Conditions (RCs). Defining RCs is crucial when evaluating the ES of a water body as it strongly affects the final outcome of any index application. Identifying RCs by observing real sites is not feasible in many marine environments, such as the Emilia-Romagna coast (Italy, N-Adriatic Sea). We used a statistical approach on a large dataset to derive RCs for the application of the benthic index M-AMBI in this area. We then applied M-AMBI to samples collected along a gradient of presumed environmental disturbance. The results put 14.8% of the Emilia-Romagna samples in “High” ES, 60.2% in “Good”, 23.0% in “Moderate” and 2.0% in “Poor”, showing a spatial gradient of improving quality. These results are in agreement with the extensive ecological knowledge available for this area. 相似文献
85.
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87.
Changes in ownership of limited entry permits by “local” residents of the region where a fishery occurs may have significant economic and social implications for fishery-dependent regions. This paper examines changes in local permit ownership in Alaska salmon fisheries, for which a long-term decline in rural local permit ownership is an important policy concern. Theoretically, permit markets allocate permits over time to the individuals who are willing to pay the most for them. Any factors that differentially affect what local and non-local residents are willing to pay for permits may affect the equilibrium share of permits held by local residents. For remote rural fisheries in particular, these may include differences between local and non-local residents with respect to access to and costs of financing permits and boats, costs of travel to the fishery, opportunity costs of participation in the fishery, and many other factors. As a fishery increases in profitability, differences between local and non-local residents in access to financing matter more while differences in costs of travel and opportunity costs matter less in the relative ranking of what local and non-local residents are willing to pay for permits. This tends to increase the share of non-local residents among buyers willing to pay the market price for permits, reducing the equilibrium share of permits held by local residents. This leads to a conflict between two important policy goals: increasing fishery profitability and maintaining rural local permit ownership. Consistent with predictions of this theory, the local share of permit ownership in Alaska salmon fisheries is negatively related to permit prices (an indicator of fishery profitability). 相似文献
88.
Laura Navarro Enric Ballesteros Cristina Linares Bernat Hereu 《Estuarine, Coastal and Shelf Science》2011
There are deep-water populations of the endemic and threatened Mediterranean brown alga Cystoseira zosteroides in the Medes Islands Marine Reserve (NW Mediterranean). Here, the distribution, population structure, individual growth, mortality and recruitment rates of this species over two years are described in relation to the effects of an exceptional storm. We found a high spatial variability in the structure and dynamics of C. zosteroides populations at small geographical scales, suggesting that environmental factors acting at the population level display a key role in population size structure, mortality and recruitment. The elevated mortality rates recorded at some locations (almost 80%) is amongst the highest recorded for perennial algae as a consequence of a single storm, emphasizing the importance of episodic catastrophic events in the maintenance of these deep-water, slow-growing populations. These findings are of particular importance not only to fully understand the ecology of C. zosteroides, but also for its conservation. 相似文献
89.
Lisa E. Collins William BerelsonDouglas E. Hammond Angela Knapp Richard SchwartzDoug Capone 《Deep Sea Research Part I: Oceanographic Research Papers》2011,58(8):898-914
Moored sediment traps were deployed from January 2004 through December 2007 at depths of 550 and 800 m in San Pedro Basin (SPB), CA (33°33.0′N, 118°26.5′W). Additionally, floating sediment traps were deployed at 100 and 200 m for periods of 12-24 h during spring 2005, fall 2007, and spring 2008. Average annual fluxes of mass, particulate organic carbon (POC), ??13Corg, particulate organic nitrogen (PON), ??15N-PON, biogenic silica (bSiO2), calcium carbonate (CaCO3), and detrital material (non-biogenic) were coupled with climate records and used to examine sedimentation patterns, vertical flux variability, and organic matter sources to this coastal region. Annual average flux values were determined by binning data by month and averaging the monthly averages. The average annual fluxes to 550 m were 516±42 mg/m2 d for mass (sdom of the monthly averages, n=117), 3.18±0.26 mmol C/m2 d for POC (n=111), 0.70±0.05 mmol/m2 d for CaCO3 (n=110), 1.31±0.21 mmol/m2 d for bSiO2 (n=115), and 0.35±0.03 mmol/m2 d for PON (n=111). Fluxes to 800 and to 550 m were similar, within 10%. Annual average values of ??13Corg at 550 m were −21.8±0.2‰ (n=108), and ??15N averages were 8.9±0.2‰ (n=95). The timing of both high and low flux particle collection was synchronous between the two traps. Given the frequency of trap cup rotation (4-11 days), this argues for particle settling rates ≥83 m/d for both high and low flux periods. The moored traps were deployed over one of the wettest (2004-2005, 74.6 cm rainfall) and driest (2006-2007, 6.6 cm) rain years on record. There was poor correlation (Pearson's correlation coefficient, 95% confidence interval) of detrital mass flux with: Corg/N ratio (r=0.10, p=0.16); ??15N (r=−0.19, p=0.02); and rainfall (r=0.5, p=0.43), suggesting that runoff does not immediately cause increases in particle fluxes 15 km offshore. ??13Corg values suggest that most POC falling to the basin floor is marine derived. Coherence between satellite-derived chlorophyll a records from the trap location (±9 km2 resolution) and SST data indicates that productivity and export occurs within a few days of upwelling and both of these parameters are reasonable predictors of POC export, with a time lag of a few days to 2 weeks (with no time lag—SeaWiFS chlorophyll a and POC flux, r=0.25, p=0.0014; chlorophyll a and bSiO2 flux, r=0.28, p=0.0002). 相似文献
90.
Michelangelo Formisano Costanzo Federico Diego Turrini Angioletta Coradini Fabrizio Capaccioni Maria Cristina De Sanctis Cristina Pauselli 《Meteoritics & planetary science》2013,48(11):2316-2332
In this work, we study the link between the evolution of the internal structure of Vesta and thermal heating due to 26Al and 60Fe and long‐lived radionuclides, taking into account the chemical differentiation of the body and the affinity of 26Al with silicates. We explored several thermal and structural scenarios differing in the available strength of energy due to the radiogenic heating and in the postsintering macroporosity. By comparing them with the data supplied by the HEDs and the Dawn NASA mission, we use our results to constrain the accretion and differentiation time as well as the physical properties of the core. Differentiation takes place in all scenarios in which Vesta completes its accretion in <1.4 Ma after the injection of 26Al into the solar nebula. In all those scenarios where Vesta completes its formation in <1 Ma from the injection of 26Al, the degree of silicate melting reaches 100 vol% throughout the whole asteroid. If Vesta completed its formation between 1 and 1.4 Ma after 26Al injection, the degree of silicate melting exceeds 50 vol% over the whole asteroid, but reaches 100 vol% only in the hottest, outermost part of the mantle in all scenarios where the porosity is lower than 5 vol%. If the formation of Vesta occurred later than 1.5 Ma after the injection of 26Al, the degree of silicate melting is always lower than 50 vol% and is limited only to a small region of the asteroid. The radiation at the surface dominates the evolution of the crust, which ranges in thickness from 8 to about 30 km after 5 Ma: a layer about 3–20 km thick is composed of primitive unmelted chondritic material, while a layer of about 5–10 km is eucritic. 相似文献