首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 328 毫秒
1.
Brackish water ecosystems are often exposed to wide variations in environmental variables, including temperature and salinity, which may cause strong selective pressures on organisms modifying the genetic patterns of species. The aim of this work was to test whether there is a ‘divergence-with-gene flow’ in coastal lagoon populations of white seabream (Diplodus sargus) (Ria Formosa, S Portugal and Mar Menor, SE Spain) respect to four marine populations, by using partial sequences of cyt b mitochondrial gene and information from nine microsatellite loci. Genetic diversity was highest in both coastal lagoons (Mar Menor and Ria Formosa) considering mitochondrial and nuclear markers. Although some of FST population pairwise comparisons were not significant, analyses of molecular variance (AMOVAs) detected differences between groups (coastal lagoon and marine) close to significance. Also, only two haplotypes (Cytb-17 and Cytb-18) were detected in both coastal lagoon sampling sites and these localities (Mar Menor and Ria Formosa) showed the highest number of singletons, some of them with a high number of mutations, as has been already described for other Mar Menor populations (Pomatochistus marmoratus and Holothuria polii). Also, several tests detected significant positive and balancing selection considering mtDNA and microsatellite data. These data support the hypothesis of selection as one of the drivers of the genetic differences found between coastal lagoon and marine populations. The life strategy adopted by Diplodus sargus in coastal lagoons allows it to decrease its mortality rate and improve the heritability of its genes. Also, the increase time spent in coastal lagoons with different temperatures and salinities favours the fitness selection and the maintenance of exclusive haplotypes and genotypes in coastal lagoon inhabitants favouring the ‘divergence-with-gene-flow’.  相似文献   

2.
Two different Cymodocea nodosa (Ucria) Ascherson beds growing in mining-contaminated sediments were compared with two reference beds in the Mar Menor coastal lagoon. The accumulation of Zn, Pb and Cd in different fractions of the plant, the sediment parameters that regulate the availability of metals, the seabed structure and dynamics of each seagrass bed and its associated macroinvertebrate community were studied. C. nodosa accumulates metals from the sediments and reflects their bioavailability for this seagrass. At each station, the metal content of the rhizomes was lower than that of leaves and roots. The concentration of acid-volatile sulfides does not seem to influence the availability of metals to the seagrass, possibly due to oxygen transport to underground tissues. The highest metal concentration in all the contaminated stations was found in the leaf-biofilm, due to the formation of complexes between metals and the extracellular polymeric substances that form the biofilm. All the seagrass beds were seen to be undergoing expansion, those growing in contaminated sediments accumulating great quantities of metals and showing highest photosynthetic leaf surface area and highest leaf biomass. However, these structural parameters were not seen to be responsible for the differences in the faunal composition observed between contaminated and reference beds. Moreover, the multivariate analysis identified the metal content of leaves, biofilm and sediments as important variables that may be responsible for these differences in faunal composition. In this study we have demonstrated that both the seagrass C. nodosa and the biofilm on the plant leaves may be used as environmental tools in the Mar Menor lagoon. The former is an useful indicator of sediment contamination, whereas the latter seems to be a good sentinel of water quality.  相似文献   

3.
The extreme environmental variability of coastal lagoons suggests that physical and ecological factors could contribute to the genetic divergence among populations occurring in lagoon and open‐coast environments. In this study we analysed the genetic variability of lagoon and marine samples of the sand goby, Pomatoschistus marmoratus (Risso, 1810) (Pisces: Gobiidae), on the SW Spain coast. A fragment of mitochondrial DNA control region (570 bp) was sequenced for 196 individuals collected in five localities: Lo Pagan, Los Urrutias and Playa Honda (Mar Menor coastal lagoon), and Veneziola and Mazarrón (Mediterranean Sea). The total haplotype diversity was h = 0.9424 ± 0.0229, and the total nucleotide diversity was π = 0.0108 ± 0.0058. Among‐sample genetic differentiation was not significant and small‐scale patterns in the distribution of haplotypes were not apparent. Gene flow and dispersal‐related life history traits may account for low genetic structure at a small spatial scale. The high genetic diversity found in P. marmoratus increases its potential to adapt to changing conditions of the Mar Menor coastal lagoon.  相似文献   

4.
M. Nagaraj 《Marine Ecology》1992,13(3):233-241
Abstract. Larval development of the crab Liocarcinus puber was studied from hatching to the megalopa stage under 12 different temperature and salinity combinations, 10°C, 15°C, and 20°C (T): 20, 25, 30, and 35% (S), with a view to establishing optimum conditions for zoeal development. High larval mortalities were recorded at 10°C in all the experimental salinities, indicating the sensitivity of the larvae to low temperatures. Highest zoeal survival was obtained in the higher salinity and temperature combinations. First zoeae completed their development in all T-S combinations tested, while successive stages showed increased sensitivity and suffered high mortalities in lower salinities at 15° and 20°C and in all salinities at 10°C. The duration of zoeal development decreased with increasing temperature, whilst the lower salinities delayed development. Q10 values did not differ much at higher salinities, with values ranging from 1.5 to 2.6.  相似文献   

5.
Abstract. The Adriatic brown macroalga Fucus virsoides (DON.) J. Ac (Fucales, Phaeophyceae) was investigated with particular respect to basic physiological features such as photosynthesis, dark carbon fixation, and respiration. Values obtained are expressed in various reference systems. Chemical composition of the fronds and physiological activity (photosynthesis/dark fixation along with the respective carboxytating enzymes (ribulose-1,5-bisphophate carboxylase and phosphoenol-pyruvate carboxykinase) show longitudinal profiles. Temperature characteristics of photosynthesis in long-term adapted specimens indicate reduced productivity at temperatures exceeding 20 °C. Photosynthesis during atmospheric exposure is markedly increased under moderate desiccation. Photosynthetic rates steadily decline under reduced salinity of the incubation medium, while respiration is stimulated. Net primary productivity of a F. virsoides stand at 15 °C ambient average temperature, tidal exposure for maximally 2–3 hours and light-dark regime = 12: 12 is calculated as 4.8-5.4 g C m-2d-1. Culture experiments with polluted incubation media provide evidence that excessive nutrients including nitrate and phosphate as well as high concentrations of heavy metals (Zn, Co, Mn) cause severe growth-rate reduction which may account for the steady decrease of F. virsoides in its natural habitat. The results are discussed with emphasis on the autecology of F. virsoides and its relationships to Atlantic representatives of the genus.  相似文献   

6.
As coastal lagoons serve as nursery areas for some marine and estuarine fish, selective pressures of these brackish or hypersaline lagoons may influence the genetic structure of species and populations. We examined spatial and temporal genetic patterns at eight microsatellite loci in white seabream [Diplodus sargus (Linnaeus 1758)] recruits from the Mar Menor (Southeast Spain) and compared these loci with those in coastal populations from the open sea, observing a high degree of genetic diversity and spatio‐temporal genetic stability. However, the results suggest the presence of subpopulations or genetic substructures in the Mar Menor D. sargus population that could be interpreted as a homogeneous mixture of individuals from three differentiated subpopulations in the Mediterranean and evidence of the Wahlund effect. It also suggests that D. sargus adults return to their original spawning habitat, thus conserving the genetic differences among the respective populations over time. Overall, this study demonstrates the importance of the Mar Menor coastal lagoon as a nursery area for the conservation of genetic diversity of D. sargus populations.  相似文献   

7.
Abstract. Respiration in Holothuria tubulosa was investigated in individuals from the Posidonia oceanica meadow off Lacco Ameno (Ischia Island, Italy). Respiratory rates increase with increasing body weight and increasing sea water temperature. Oxygen consumption of an average individual (7g dw body wall) ranges from 0.409 (14 °C) to 1.300 (26 °C) mg O2· h-1. Data on population density, mean size of individuals, and annual sea water temperature variations allow an assessment of holothuroid production. Values of 45.65 and 13.75 kJ · m-2· y-1 were calculated for shallow (3 to 10 m) and deep (25 to 33 m) areas of the Posidonia meadow, respectively. Holothuroid production shows a bathymetric pattern similar to primary production of the Posidonia -epiphytes complex and the production of Posidonia litter.  相似文献   

8.
Clearance rates, respiration rates and food absorption efficiencies of the commercially interesting subtidal bivalve Modiolus barbatus were measured at different temperatures under laboratory conditions and scope for growth calculated. Clearance rates were highest at temperatures from 20 °C to 28 °C, whereas respiration rate was maximal at 9 °C and minimal at 26 °C. Highest mean values of absorbed energy occurred at 20 °C and 26 °C. Scope for growth trend had negative values at 9 °C, 15 °C and 28 °C and positive values at temperatures 20 °C and 26 °C. The profitable thermal window for M. barbatus to have energy sufficient for growth and reproduction corresponded to <5 months per year. Seawater temperature increases will potentially impact the eco-physiological responses of subtidal M. barbatus causing life history traits to change with important repercussions for subtidal biodiversity in the Mediterranean.  相似文献   

9.
Abstract. Dark respiration rates, dissolved inorganic nitrogen (DIN) fluxes and nitrification rates were measured at two sites in the microtidal Sacca di Goro lagoon in September 2000. DIN fluxes correlated with the biomass of the dominant macrofauna species (the amphipod Corophium spp. at station Giralda and the polychaete Neanthes spp. at station Faro). Respiration (> 6 mmol O2 m−2h−1) and ammonium fluxes (> 80μmol N m−2h−1) were higher at station Giralda despite the lower organic matter content (4.5 %) and lower macrofauna biomass (4 g AFDW m−2). At both sites ammonium fluxes were significantly correlated with the biomass of the benthic infauna, but Corophium stimulated ammonium NH4+ fluxes 3-fold compared to Neanthes. The amphipod also enhanced nitrification rates (> 300 μmol N m−2h−1) due to the high density of its burrows, the higher NH4+ regeneration rates and the enhanced oxygen supply to the bacteria.  相似文献   

10.
Although benthic macrophytes must be considered in monitoring programs to establish the ecological status of transitional and coastal waters in the European Union, the patterns of variability in species composition of macrophyte assemblages in Mediterranean coastal lagoons has scarcely been studied. In this work the spatial (both vertical and horizontal) and seasonal dynamics of macrophyte assemblages in a coastal lagoon (Mar Menor) are compared with those of open coastal assemblages in the SW Mediterranean to analyze any biological variability in lagoon assemblages and the factors that determine such variability. Different assemblages, characterized by well defined groups of species, can be described according to their isolation from the open sea and the type of substratum; at the same time, a vertical zonation pattern, similar to that found in all marine communities but more compressed, exists. This implies that when applying the EU Water Framework Directive or assessing environmental impact, a lagoon should not be considered spatially uniform and unique unit but as a mosaic of assemblages.  相似文献   

11.
The reproduction and sexual cycles of Donax venustus Poli 1795, Donax semistriatus Poli 1795, and individuals with intermediate shell morphotypes were studied in the littoral of Málaga (Southern Spain) from February 1990 to January 1991, using histology and analysing the changes in flesh dry weight. The littoral of Málaga has mild seawater temperatures and several upwellings with high levels of chlorophyll a. Due to these environmental conditions, the reproductive periods of these bivalve species are very extensive, from February to November. The histological study shows asynchronous sexual cycles, with continuous but partial individual spawnings from April to November in about 50% of the D. semistriatus population, and percentages higher than 40% of the sample in most months for D. venustus. An important decrease in the ratio flesh dry weight/length3 was noted from June to August in the three populations; this is apparently related with peaks of spawning. Based on the macroscopic observation of the gonads, on the flesh dry weight study and on histological data, the sexual cycle of the intermediate morphotypes is simultaneous and similar throughout the year with those of D. venustus and D. semistriatus .  相似文献   

12.
Abstract. An experiment to test C have's hypothesis on temperature dependent MgCO3 concentrations in marine calcareous skeletons was undertaken by transplanting colonies of Heliopora coerulea. The corals were transferred from a shallow lagoon with high average temperatures to the outer bottom of a fringing reef, 16 m depth, with low average temperatures. Against expectation, a statistically significant increase of average mol % concentrations from 0.48 to 0.54 % for upper growth regions and from 0.49 to 0.62% for lower growth regions was obtained. Temperature records during the experimentation period and the above data indicate that the mol% MgCO3 concentration in the skeleton of living Heliopora colonies increases when transplanted to an environment with a lower temperature average than that of their original growth site, and with seasonal temperature fluctuations which are smaller in the experimental site than in the control site. Temperature fluctuations at the control site were up to 2.5 times greater than at the experimental site for most of the observation months. This supports the conclusion that the parameters a) minimum temperature and b) temperature stability of the environment are essential for the incorporation of Mg into the carbonate skeleton matrix of marine organisms. Within this study the results of a quantitative chemical analysis of the carbonate skeleton of H. coerulea are presented and growth data of transplanted colonies compared with those from the control site.  相似文献   

13.
Abstract. Hg, Cd, Pb and Zn concentrations were determined in sediment and in tissues of five species of soft-bottom marine macrophytes ( Posidonia oceanica, Cymodocea nodosa, Zostera noltii, Ruppia cirrhosa and Caulerpa prolifera ) along the Spanish Mediterranean coast. Levels of metals were low in most of the sampling stations and similar to those found by other authors in uncontaminated zones. Certain locations, however, showed some degree of contamination (Cambrils, Almassora, Alacant, Mar Menor and El Portús). In Santa Pola we found high contents of metals in one sample of sediment due to the high proportion of the fine fraction (particules < 63µm) and organic matter, but not in the seagrass species. Mercury and zinc concentrations in the sediment are correlated to those in at least some anatomic fractions of Posidonia oceanica, Cymodocea nodosa and Caulerpa prolifera , suggesting that these species reflect the levels of these metals in the environment. Lead contents in the alga Caulerpa prolifera are also correlated to those in the sediment, while no significant correlations were obtained for cadmium. Among the species studied, Posidonia oceanica and Cymodocea nodosa seem to be better biomonitors than Caulerpa prolifera .  相似文献   

14.
In the framework of the VECTOR DIVCOST Project, a 2-year investigation was started in 2006, with the aim of testing the sensibility of microbial parameters to environmental changes and of assessing whether they can provide information about functional changes in the carbon cycle. The investigation was performed in the surface waters of two small brackish ponds (Ganzirri and Faro), located in the Cape Peloro transitional area (Sicily, Italy). The seasonal changes in both the microbial compartment [bacterioplankton, vibrios, exoenzymatic hydrolysis of proteins and polysaccharides, bacterial secondary production (HBP) and community respiration] and the trophic state of suspended matter [total suspended matter (TSM), particulate organic carbon (POC), particulate organic nitrogen (PON), C/N] were analysed in relation to the hydrological characteristics [temperature, salinity, oxygen, fluorescence, NH4, NO2, NO3, PO4]. Despite marked differences in the nutritional input and the diversification in both carbon budget and trophic level, the two ponds show similar trends in many of the investigated factors, hardly influenced by seasonal variations. Temporally coupled trends were observed for some parameters (enzyme activities, vibrios abundances, respiratory activity), whereas others (POC, PON, heterotrophic bacterial production, bacterioplankton) showed a seasonal shift between the two lakes. The different behaviour found for the some biotic parameters suggests that their response to environmental conditions may be modulated differently between the two lakes, which, despite their spatial proximity and reciprocal connection, do not always show contemporaneous functional processes.  相似文献   

15.
A modelling approach is proposed to evaluate the environmental dynamics of coastal lagoons. The water, heat and salt balances are addressed simultaneously, providing a better estimation of evaporation and water exchanges. Compared to traditional approaches, the model presented accounts for the effects of water salinity, heat storage and net energy advected in the water body. The model was applied daily to the Mar Menor coastal lagoon (SE Spain) from 2003 through 2006. Water exchanges with the Mediterranean Sea were estimated based on the monthly trend of the lagoon salinity and were correlated with monthly averages of wind speed. The mean daily water exchange with the sea was 1.77 hm3 d−1. This exchange accounted for only 1% of the heat losses in the lagoon heat balance, and it is the most important flow in the water balance. The mean annual evaporation flux amounted to 101.3 W m−2 (3.55 mm d−1), while the sensible heat flux amounted to 19.7 W m−2, leading to an annual Bowen ratio on the order of 0.19. To validate the model, daily water temperatures were predicted based on the daily heat balance of the water body and were compared with remote sensing data from water surface standard products.  相似文献   

16.
The macroalga Caulerpa prolifera colonized the Mar Menor coastal lagoon after the enlargement of the main inlet in 1972, coexisting now with the previous Cymodocea nodosa meadows. The physiological response and the photoacclimation capacity of both species were studied. For this purpose in vivo chlorophyll a fluorescence, photoprotective mechanisms and oxidative stress were measured in both species in summer 2010 and exposure-recovery experiments were conducted to determine the acclimation capacity of both species. The results suggest that C. prolifera behaves as a shade-adapted species with a low photoprotective capacity, light being one of the main factors governing its distribution in the lagoon. The high photosynthetic capacity and lack of photoinhibition found in C. nodosa suggest that this species is highly photoprotected. It also possesses a high concentration of lutein and a high de-epoxidation degree, related to a much higher NPQmax value.  相似文献   

17.
Abstract. A seasonal sampling program of five stations off the Island of Rhodes (SE Aegean Sea) was carried out in 1983–1984. Temperature, salinity, Secchi disk transparency, P-PO4, N-NO3, N-NO2, N-NH3, Si-SiO2, and chl a were measured and phytoplankton species recorded. Cell concentrations and chl a varied seasonally. with the highest values in summer (l.2 times 104 -1--1 total mean cells; 0.13 mgam-3 total mean chl a ) and the lowest in winter (2.3 times 103, 1--1 total mean cells; 0.06 mg.m-- total mean chl a ). A variation in cell abundance among stations was also noted. Quantitative relationships among the recorded taxa showed that diatoms and dinoflagellates were richer in species composition (88 and 58 total species, respectively) than coccolithophores (8 species) and other flagellates (8 species). Comparison of phytoplankton samples from different depths and stations by cluster analysis showed an irregularity or discontinuity in species associations. The SE Aegean Sea was characterized as oligotrophic on the basis of the estimated nutrient and phytoplankton concentration levels.  相似文献   

18.
In recent decades wetlands associated with the Mar Menor lagoon (SE Spain) have undergone several hydrological and biological changes as a consequence of increased water inputs from agricultural drainage off the watershed. Changes in the vegetal communities were studied by means of supervised classification of Landsat images, and TM and ETM+ sensors during the period 1984–2000, and a series of land cover maps was created. Changes in the wetland area during this period were analysed and a good fit was found with the total area of irrigated lands in the watershed. The series of land cover maps also allowed the study of the internal composition of the vegetal communities in each wetland. Important changes were detected, with an expansion of reedbeds and a significant reduction in the area occupied by priority habitats according to the Habitats Directive.  相似文献   

19.
尖刀蛏的生殖周期   总被引：7，自引：0，他引：7  
本文是尖刀蛏Ｃｕｌｔｅｌｌｕｍ ｓｃａｌｐｒｕｍ（Ｇｏｕｌｄ）生物学系列研究之一，报告了１９８５年２月至１９８６年２月福宁湾尖刀蛏生殖腺周年发育和组织学观察的初步结果。性腺发育分４期：增殖期、成熟期、排放期、耗尽期。存在着雌雄同体和性变现象。雌雄性比和性变与贝龄有一定关系。  相似文献   

20.
Inka  Dor Aline  Ehruch 《Marine Ecology》1987,8(2):193-205
Abstract. Several species of cyanobacteria, diatoms and one euglenid alga populated the littoral zone of hypersaline solar ponds investigated over a period of three years. The composition of the microalgae community changed with salinity and temperature. In the shallow marginal zone the diatoms predominated in winter and spring, at salinities of 30–72 g-1-1 and at temperatures not exceeding 30o°C, whereas in summer, cyanobacteria were the most abundant. In the deeper zone, at higher salinities and temperatures, cyanobacteria predominated throughout the year. The depth limit of algal growth was 60-80cm, where salinity and temperature exceeded 211 g-1-1 and 48°C.
The most euryhaline and eurythermal among cyanobacteria were Aphanolhece halophytica F remy and Phormidium hypolimneticum C ampbell , among diatoms Nitzschia sp. aff. N. rostellata H ustedt , Amphora coffeaeformis (A gardh ) K utzing , and Navicula massadaea E hrlich .  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号