Reef microhabitats mediate fish feeding intensity and agonistic interactions at Príncipe Island Biosphere Reserve,Tropical Eastern Atlantic     

Angela Marina Canterle  Lucas Teixeira Nunes  Luisa Fontoura  Hugulay Albuquerque Maia  Sergio Ricardo Floeter 《Marine Ecology》2020,41(5):e12609

The benthic assemblage of reefs provides an important resource of food and habitat for reef fishes. However, how benthic composition mediates reef fishes' biotic interactions at isolated environments such as oceanic islands remains largely unknown. Here, we aimed to investigate the role of four different reef microhabitats over biological interactions of fishes in an understudied oceanic island, Príncipe Island. For that, we recorded a total of 46 Underwater Remote Videos (RUVs) to document benthic composition and fishes' trophic and agonistic interactions. We used benthic cover estimates to group the samples into four microhabitats (dominated by epilithic algal matrix [EAM], sand/rock, corals and sponges), then quantified fishes' trophic and agonistic interactions in each microhabitat. All microhabitats presented a different structure of trophic and agonistic interactions of the fish assemblage. Feeding pressure (FP) and agonistic interactions were higher on the EAM microhabitat and lower in coral microhabitat. Herbivores were the main responsible group for the FP in all microhabitats. Territorial damselfishes used microhabitats differently for both trophic and agonistic interactions. We demonstrated that reef fish diversity and intensity of biotic interactions varied according the spatial distribution of benthic resources, which suggests that benthic composition plays an important role on structuring biological interactions at isolated reef systems.  相似文献   

Spectral properties and mineral compositions of acapulcoite–lodranite clan meteorites: Establishing S‐type asteroid–meteorite connections     

Michael P. Lucas  Joshua P. Emery  Takahiro Hiroi  Harry Y. McSween 《Meteoritics & planetary science》2019,54(1):157-180

Except for asteroid sample return missions, measurements of the spectral properties of both meteorites and asteroids offer the best possibility of linking meteorite groups with their parent asteroid(s). Visible plus near‐infrared spectra reveal distinguishing absorption features controlled mainly by the Fe²⁺ contents and modal abundances of olivine and pyroxene. Meteorite samples provide relationships between spectra and mineralogy. These relationships are useful for estimating the olivine and pyroxene mineralogy of stony (S‐type) asteroid surfaces. Using a suite of 10 samples of the acapulcoite–lodranite clan (ALC), we have developed new correlations between spectral parameters and mafic mineral compositions for partially melted asteroids. A well‐defined relationship exists between Band II center and ferrosilite (Fs) content of orthopyroxene. Furthermore, because Fs in orthopyroxene and fayalite (Fa) content in olivine are well correlated in these meteorites, the derived Fs content can be used to estimate Fa of the coexisting olivine. We derive new equations for determining the mafic silicate compositions of partially melted S‐type asteroid parent bodies. Stony meteorite spectra have previously been used to delineate meteorite analog spectral zones in Band I versus band area ratio (BAR) parameter space for the establishment of asteroid–meteorite connections with S‐type asteroids. However, the spectral parameters of the partially melted ALC overlap with those of ordinary (H) chondrites in this parameter space. We find that Band I versus Band II center parameter space reveals a clear distinction between the ALC and the H chondrites. This work allows the distinction of S‐type asteroids as nebular (ordinary chondrites) or geologically processed (primitive achondrites).  相似文献   

Carbon isotopic fractionation in macroalgae from Cádiz Bay (Southern Spain): Comparison with other bio-geographic regions     

Jesús M. Mercado  Carmen B. de los Santos  J. Lucas Pérez-Lloréns  Juan J. Vergara 《Estuarine, Coastal and Shelf Science》2009

The ¹³C signature of forty-five macroalgal species from intertidal zones at Cádiz Bay was analysed in order to research the extension of diffusive vs. non-diffusive utilisation of dissolved inorganic carbon (DIC) and to perform a comparison with data published for other bio-geographic regions. The ∂¹³C values ranged from −6.8‰ to −33‰, although the span of variation was different depending on the taxa. Thus, ∂¹³C for Chlorophyta varied from −7‰ (Codium adhaerens) to −29.6‰ (Flabellia petiolata), while all the Phaeophyceae (excepting Padina pavonica with ∂¹³C higher than −10‰) had values between −10‰, and −20‰. The widest variation range was recorded in Rhodophyta, from values above −10‰ (Liagora viscida) to values lower than −30‰ obtained in three species belonging to the subclass Rhodymeniophycidae. Accordingly, the mean ∂¹³C value calculated for red algae (−20.2‰) was significantly lower than that for brown (−15.9‰) and green algae (−15.6‰). Most of the analysed red algae were species inhabiting crevices and the low intertidal fringe which explains that, on average, the shaded-habitat species had a ∂¹³C value lower than those growing fully exposed to sun (i.e. in rockpools or at the upper intertidal zone). The comparison between the capacity for non-diffusive use of DIC (i.e. active or facilitated transport of HCO₃⁻ and/or CO₂) and the ∂¹³C values reveals that values more negative than −30‰ indicate that photosynthesis is dependent on CO₂ diffusive entry, whereas values above this threshold would not indicate necessary the operation of a non-diffusive DIC transport mechanism. Furthermore, external carbonic anhydrase activity (_extCA) and ∂¹³C values were negatively correlated indicating that the higher the dependence of the photosynthesis on the CO₂ supplied from HCO₃⁻ via _extCA, the lower the ∂¹³C in the algal material. The comparison between the ∂¹³C values obtained for the analysed species and those published for species inhabiting other bio-geographic areas (warm-temperate, cold and polar) suggests that globally (at least for the red and brown algae) the non-diffusive entry of DIC is more widely spread among the species from Cádiz Bay than among those of polar regions. If it is assumed that non-diffusive use of DIC implies saturation of photosynthesis at the present-day CO₂ concentration in seawater, our data indicate that the potential impact of the acidification on photosynthesis in the seaweed communities will be different depending on the latitude.  相似文献   

Pyrite as a proxy for the identification of former coastal lagoons in semiarid NE Brazil     

Tiago O. Ferreira  Gabriel N. Nóbrega  Antonia G. B. M. Albuquerque  Lucas R. Sartor  Irlene S. Gomes  Adriana G. Artur  Xosé L. Otero 《Geo-Marine Letters》2015,35(5):355-366

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Recent snow cover changes over central European low mountain ranges     

Chunyu Dong  Lucas Menzel 《水文研究》2020,34(2):321-338

In this study, we simulated the snow water equivalent (SWE), rain-on-snow (ROS) events, evapotranspiration, and run-off for the period 1961–2016 in a central European region covered by low mountain ranges (<820 m a.s.l.) using a distributed hydrological model TRAnspiration and INterception evaporation model (TRAIN). We utilized improved cloud-free Moderate Resolution Imaging Spectroradiometer (MODIS) snow cover products to evaluate the modelled snow-covered area, indicating a good performance of the snow modelling. We analysed the intra- and inter-annual variations of the simulated hydrological variables and the synchronous climate variables (air temperature and precipitation). Trend detection indicates a significant SWE decline throughout the snow season, but principally at the high elevations; the most severe warming occurred in early spring (March), whereas precipitation showed a slight increase in January and February. The snowpack in February has displayed the most striking reduction during the past 56 years, which is likely related to both the highest susceptibility of snow to warming and the increased ROS occurrence in February since the early 1990s. The increased combination of high temperatures and extreme rainfalls, as well as the earlier snowmelt, has resulted in a run-off increase during the earlier winter but a decrease in March. The expected changing climate towards warmer and wetter winters will probably exacerbate winter flooding in the future.  相似文献   

Experimental Design for the Laboratory Simulation of Magnetized Astrophysical Jets     

Radu Presura  Stephan Neff  Lucas Wanex 《Astrophysics and Space Science》2007,307(1-3):93-98

Concepts of several experimental configurations for the investigation of magnetized jets and their interaction with magnetized environments are presented. In the planned experiments, the plasma jets will be created by laser ablation of shaped targets, while magnetic and electric fields with the required configurations will be produced independently by a pulsed power generator. In particular, the recently coupled Terawatt laser Tomcat and Terawatt pulsed power generator Zebra will be used for experiments.  相似文献