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Microbial planktonic communities (i.e. bacteria and protozoa),
phytoplankton, dissolved organic carbon (DOC) and particulate organic
carbon (POC) were seasonally examined at Medes Islands (Northwestern
Mediterranean) to assess their variation in abundance and composition
throughout the year in a near-bottom littoral ecosystem. From October 1995
to November 1996, samples were collected between two and six times per
month at 0.5 m above the bottom. Mean DOC and POC values throughout the
year were 2560 180 (SE) and 387
± 35 g C
l-1, respectively. All year, detrital organic carbon
(detrital=total POC - live carbon) represented the main POC fraction, and
mean live carbon was 24 ± 9 g C
l-1. Winter and spring had maximum values of POC,
and spring and summer had maximum values of DOC. Heterotrophic bacteria,
with a mean abundance of 5.16 ± 0.08 x
105 cells ml-1, were the main
contributor to live carbon (26 ± 7%). During winter,
heterotrophic bacterial biomass decreased 40% due to a decrease in mean
biovolume per cell. Synechococcus sp. and
Prochlorococcus sp. abundance were 2.24 ±
0.09 x 104 and 1.05 ± 0.07 x
104 cells ml-1, respectively.
However, while Synechococcus sp. were present all
year, Prochlorococcus sp. were not observed from April
to July. Mean phytoplankton (i.e. diatoms and dinoflagellates) abundance
was 2.06 ± 0.40 x 104 cells
l-1 with biomass at a maximum during the winter
months, the period with the lowest temperature and the highest nutrient
concentration. The size composition of live carbon showed two clearly
distinct periods: from December to March, live carbon was dominated in
biomass by microplankton, while from April to November, pico- and
nanoplankton cells were dominant. Overall, the dynamics of the near-bottom
planktonic communities was characterized by a low biomass of heterotrophic
and autotrophic bacteria, phytoplankton and ciliates in contrast to
previous water column studies. This pattern and the high temporal
heterogeneity of the different planktonic communities are discussed in
relation to the physical and chemical characteristics of the environment,
as well as to the potential role that benthic communities may be exerting
in the control of the near-bottom planktonic communities.
相似文献
33.
Grupstra Carsten G. B. Coma Rafel Ribes Marta Leydet Karine Posbic Parkinson John Everett McDonald Kelly Catllà Marc Voolstra Christian R. Hellberg Michael E. Coffroth Mary Alice 《Coral reefs (Online)》2017,36(3):981-985
Coral Reefs - Zooxanthellate corals are threatened by climate change but may be able to escape increasing temperatures by colonizing higher latitudes. To determine the effect of host range... 相似文献
34.
Macroalgae is the dominant trophic group on Mediterranean infralittoral rocky bottoms, whereas zooxanthellate corals are extremely rare. However, in recent years, the invasive coral Oculina patagonica appears to be increasing its abundance through unknown means. Here we examine the pattern of variation of this species at a marine reserve between 2002 and 2010 and contribute to the understanding of the mechanisms that allow its current increase. Because indirect interactions between species can play a relevant role in the establishment of species, a parallel assessment of the sea urchin Paracentrotus lividus, the main herbivorous invertebrate in this habitat and thus a key species, was conducted. O. patagonica has shown a 3-fold increase in abundance over the last 8 years and has become the most abundant invertebrate in the shallow waters of the marine reserve, matching some dominant erect macroalgae in abundance. High recruitment played an important role in this increasing coral abundance. The results from this study provide compelling evidence that the increase in sea urchin abundance may be one of the main drivers of the observed increase in coral abundance. Sea urchins overgraze macroalgae and create barren patches in the space-limited macroalgal community that subsequently facilitate coral recruitment. This study indicates that trophic interactions contributed to the success of an invasive coral in the Mediterranean because sea urchins grazing activity indirectly facilitated expansion of the coral. Current coral abundance at the marine reserve has ended the monopolization of algae in rocky infralittoral assemblages, an event that could greatly modify both the underwater seascape and the sources of primary production in the ecosystem. 相似文献
35.
Marta Herreros-Villanueva Maximiliano Rodrigo Manuel Claver Pilar Muñiz Enrique Lastra Carlos García-Girón Maria Jesus Coma del Corral 《Molecular biology reports》2011,38(2):1315-1320
To evaluate the KRAS, BRAF, EGFR, and HER2 gene status in colorectal cancer by novel techniques and evaluate whether anti-HER2 therapies could be offered in the treatment
of these patients. There are conflicting data on the prevalence of BRAF mutations and EGFR and HER2 gene amplification in colorectal KRAS wild type patients. In our study we tried to evaluate these expressions and their relationship to future treatment assays.
Clinical–pathological data and paraffin-embedded specimens were collected from 186 patients who underwent colorectal resections
at General Yagüe Hospital in Burgos, Spain. KRAS and BRAF status was analyzed by real-time PCR in all patients. EGFR and HER2/NEU gene amplification was detected using fluorescent in situ hybridisation technique (FISH) in 38 KRAS and BRAF wild type patients. KRAS mutations were present in 48% of the colorectal cancer patients. BRAF mutations were present in 6.25% of the KRAS wild type patients. EGFR and HER2 gene amplification was observed in 5.3% and 26.3%, respectively, of KRAS and BRAF wild type colorectal cancer patients. HER2, but not EGFR gene amplification, was frequently observed in KRAS and BRAF wild type colorectal cancer patients. These data indicate that HER2 amplification could be one of the genes to be considered in the therapeutic management of colorectal cancer. 相似文献
36.
Clearance of amyloid-beta by circulating lipoprotein receptors 总被引:7,自引:0,他引:7
Sagare A Deane R Bell RD Johnson B Hamm K Pendu R Marky A Lenting PJ Wu Z Zarcone T Goate A Mayo K Perlmutter D Coma M Zhong Z Zlokovic BV 《Nature medicine》2007,13(9):1029-1031
Low-density lipoprotein receptor-related protein-1 (LRP) on brain capillaries clears amyloid beta-peptide (Abeta) from brain. Here, we show that soluble circulating LRP (sLRP) provides key endogenous peripheral 'sink' activity for Abeta in humans. Recombinant LRP cluster IV (LRP-IV) bound Abeta in plasma in mice and Alzheimer's disease-affected humans with compromised sLRP-mediated Abeta binding, and reduced Abeta-related pathology and dysfunction in a mouse model of Alzheimer disease, suggesting that LRP-IV can effectively replace native sLRP and clear Abeta. 相似文献
37.
Imma Llobet Rafel Coma Mikel Zabala Josep-Maria Gili R. G. Hughes 《Journal of experimental marine biology and ecology》1991,150(2):283-292
O. crenata on the alga Halimeda tuna were sampled every 2 wk for a year off Tossa de Mar, northeastern Spain. The hydroids were most abundant from November to April when three cohorts, identified by size frequency, were present. From April to October the population consisted of two cohorts, except in June and July when the population density was low and only one cohort, of young hydroids, was identifiable. The paucity of O. crenata in summer was attributed to the high rate of turnover of host thalli, interspecifuc competition with other epiphytes, and a possible shortage of suitable planktonic prey. Recruitment was predominantly asexual, by stolons, and occurred throughout the year. Gonozoids were found only from late October to early December when recruitment by planula larvae also occurred. In winter, when the cohorts lived for the maximum of ≈6 wk, colony sizes quintuplicated and triplicated in successive 15-day periods. Although colonies (ramets) of O. cretana on H. tuna have a short life span reproduction and dispersal to other thalli by stolons means that the genets can survive beyond the life of a host, and perhaps indefinitely. 相似文献
38.
Prey capture by a benthic coral reef hydrozoan 总被引:1,自引:0,他引:1
The natural diet and prey abundance of the benthic coral reef hydrozoan Nemalecium lighti, a common tropical species, were studied by analysing the gastrovascular contents of polyps. Prey capture was estimated from
10 samples collected at 3-h intervals during a single diel cycle (1–2 September, 1995) in the San Blas Islands (Panamá). Prey
size ranged from 5 to 550 μm, with invertebrate larvae being the main contributor to the diet of the species. Prey items were
found in 56–88% of the polyps over the entire diel cycle. Gastrovascular contents varied between 0.93 and 2.13 prey items
per polyp. These capture incidences are among the highest reported for cnidarian species. Such rates would allow for high
production rates for Nemalecium lighti, consistent with reports of the species’ fast growth and high reproduction rates. The observations suggest that some hydrozoans
may be active heterotrophic components in coral reef ecosystems.
Accepted: 3 January 1999 相似文献
39.
Seasonal energetic constraints in Mediterranean benthic suspension feeders: effects at different levels of ecological organization 总被引:6,自引:0,他引:6
The aim of this work is to examine the role of food as a constraining factor at different levels of ecological organization in benthic littoral ecosystems. In the search for patterns in ecological systems, it has recently been documented that seasonality in the dynamics of benthic suspension feeders (BSF) in the Mediterranean Sea is characterized by summer dormancy. We review recent studies on seston availability in the water column and feeding and respiration by BSF in the Mediterranean. The objective is to assess whether a pattern across particular studies exists that could provide evidence of food as a constraining factor. A pattern emerges from these organism‐level studies, one which indicates the seasonal occurrence of an energy shortage in the taxa exhibiting summer dormancy. This energy shortage is closely related to low food availability and suggests that an energetic constraint underlie the summer dormancy phenomenon. The seasonal occurrence of summer energy shortage also appears to affect the dynamics of BSF at population and community level. In this sense, in late summer 1999, a mass mortality event of BSF affected several hundreds of kilometers in the Ligurian Sea (NW Mediterranean). The fact that the mass mortality event occurred in late summer and especially affected the taxa that exhibit energy shortage – such as anthozoans and sponges – suggests, that energetic constraints may contribute to the understanding of the mass mortality event. The energy shortage phenomenon may provide a mechanism to understand how the occurrence of anomalous climatic conditions may have induced the mass mortality of some BSF taxa. This review points out the existence of a common energy shortage phenomenon mainly related to low food availability as an important determinant of the dynamics of most BSF taxa at organism level in the Mediterranean. But this determinant also affects the dynamics of BSF at population and community level. Therefore, the extant data point up the crucial role of food as a constraining factor for benthic littoral ecosystems in oligotrophic areas like the Mediterranean, with important seasonal variations in seston abundance and composition. 相似文献
40.
Global warming has many biological effects on corals and plays a central role in the regression of tropical coral reefs; therefore, there is an urgent need to understand how some coral species have adapted to environmental conditions at higher latitudes. We examined the effects of temperature and light on the growth of the zooxanthellate coral Oculina patagonica (Scleractinia, Oculinidae) at the northern limit of its distribution in the eastern Iberian Peninsula (western Mediterranean) by transplanting colonies onto plates and excluding them from space competition over a ~4-yr period. Each year, most of the colonies (~70%) exhibited denuded skeletons with isolated polyps persisting on approximately half of the coral surface area. These recurrent episodes of partial coral mortality occurred in winter, and their severity appeared to be related to colony exposure to cold but not to light. Although O. patagonica exhibited high resistance to stress, coral linear extension did not resume until the coenosarc regenerated. The resumption of linear extension was related to the dissociation of the polyps from the coenosarc and the outstanding regenerative capacity of this species (10.3 mm2 d?1). These biological characteristics allow the species to survive at high latitudes. However, the recurrent and severe pattern of denuded skeletons greatly affects the dynamics of the species and may constrain population growth at high latitudes in the Mediterranean. 相似文献