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 371 毫秒
1.
作者详细观察并记录了中国山东烟台优势种卵圆扁蝼蛄虾鳃虱(Gyge ovalis Shiino,1939)的形态学特征,比较了不同地域该种的形态学差异,应用扫描电镜技术,发现了该物种雄性个体的关键鉴定特征。研究结果表明:中国、日本、韩国的卵圆扁蝼蛄虾鳃虱在形态特征方面雌性个体差异较大,雄性个体差异较小;卵圆扁蝼蛄虾鳃虱的地理分布相对较集中,主要分布在中国山东和台湾两省、韩国、日本,确定其为亚洲特有种;通过扫描电镜,首次发现卵圆扁蝼蛄虾鳃虱的雄性个体中腹突上有呈鳞片状分布的"锯齿"状刚毛。  相似文献   

2.
The Nansei Islands in the southern Japanese Archipelago have 15 taxa of seagrasses from seven genera within three families. Seagrasses in this region grow on coral sands or coral debris in shallow reefs and on sandy or muddy substrata in the shallow areas of bays and inlets. Certain Halophila species grow in deep water off some islands. Enhalus acoroides only reaches to Ishigaki I. with winter sea water temperature (WST) at 23 °C, while Okinawa I. (WST at 21.6 °C) is the northern biogeographic limit for Halophila decipiens, H. okinawensis, H. major and H. gaudichaudii. Amami‐oshima I. (WST at 20.7 °C) is the northern border for Thalassia hemprichii, H. minor, H. ovalis, Cymodocea serrulata, Cymodocea rotundata, Syringodium isoetifolium, Halodule uninervis and Halodule pinifolia. Halophila mikii the sole seagrass collected from Yakushima I. (WST at 19.3 °C), is of volcanic origin. The distribution of tropical seagrasses in the Nansei Islands is clearly associated with the warm Kuroshio Current, WST and habitat availability. Zostera japonica is the only temperate species occurring in the region. Meadows of Z. japonica, H. ovalis and Halodule pinifolia have disappeared from certain localities in the Archipelago, due probably to human activities and natural siltation.  相似文献   

3.
Essential nutrients for seagrass growth may be derived from benthic decomposition of organic matter. To test this idea, cores of Halophila ovalis (seagrass-vegetated) and unvegetated sediment (control) were amended with either particulate organic matter (POM) or dissolved organic matter (DOM) to test whether a positive feed-back loop exists, where increased organic matter results in increased seagrass nutrients. POM was added in the form of seagrass wrack (0, 1, 5, 12 g core−1) and DOM was added with sucrose diffusion tubes at the root zone (0, 0.8, 2.4, 5.2 g core−1). Cores were incubated under saturating light conditions (12 h light/12 h dark) at 18 °C, for 4 weeks. Results suggest a complex balance between positive and negative effects of organic matter enrichment. Whilst leaf molar concentrations of N and P of H. ovalis increased (by 15 and 30% respectively), plant growth declined (up to 50% relative to control) for both DOM and POM enrichments. Phosphate was removed from sediment porewater following POM addition and most likely translocated to the leaves. Stressors other than nutrient limitation (e.g. biogeochemical constraints) reduce growth and affect the nutrient dynamics of the seagrass and should be the focus of future work.  相似文献   

4.
We examined characteristics of the soil environment related to redox in the rhizospheres of three mangrove species that commonly grow in similar hydrogeomorphic settings: Rhizophora apiculata BL, Bruguiera gymnorrhiza (L.) Lamk., and Sonneratia alba J. Redox potential (Eh) values and extractable P concentrations were significantly higher, whereas soluble reactive P (SRP) concentrations were significantly lower in Bruguiera plots than in either Rhizophora or Sonneratia plots. Correlations among Eh, SRP, pyrite and extractable P were significant only at plots with negative Eh values. Sonneratia and Bruguiera plots had significantly different soil redox conditions. Bruguiera plots were characterized by more oxidized soil conditions (ca. 80 mV), lower dissolved P concentrations in porewater (ca. 50%), and higher extractable P concentrations in soil (ca. 25%). Differences in Eh and P reflect real differences among species and appeared not to be associated with hydrology. Species-specific differences may be engendered by the trees themselves, or they may reflect microsite differences that have favored the germination, growth, and survival of particular mangrove species.  相似文献   

5.
This study represents the first in situ assessment of seagrasses in the Union of the Comoros. The presence of the following 10 species (ranked in order of abundance) was confirmed: Thalassia hemprichii, Thalassodendron ciliatum, Syringodium isoetifolium, Halodule wrightii, Cymodocea rotundata, Cymodocea serrulata, Halodule uninervis, Halophila ovalis, Zostera capensis and Enhalus acoroides. Seagrasses occurred in large, continuous beds in the shallow waters at the northern and southern tips of Grande Comore Island and around the Bimbini Peninsula on western Anjouan Island, but were sparsely distributed throughout the shallow waters surrounding Mohéli Island.  相似文献   

6.
Egg production rates and/or hatching success in the copepods Acartia clausi, Calanus helgolandicus and Temora longicornis were negatively affected by a late spring (May–June 2003) phytoplankton bloom in the North Adriatic Sea, dominated mainly by the large diatom Cerataulina pelagica. Highest total concentrations of 3.3·104 cells·ml?1 were located in the vicinity of the Po River, which also corresponded to the area where the highest numbers of phaeophorbides were measured (0.779, 0.528 and 0.419 μg·l?1, respectively, compared to an average of the remaining stations of 0.183 ± 0.049 SD), suggesting some grazing on the bloom. Phytoplankton biomass in terms of carbon was dominated by diatoms, representing on average 42% of total phytoplankton carbon and more than 80% at several stations. Cerataulina pelagica, Cyclotella spp., Chaetoceros spp. and small unidentified centric diatoms dominated the diatom community numerically but C. pelagica was by far the dominant diatom in terms of carbon due to its large cell size. This species represented more than 60% of the diatom biomass at nine of the 14 stations sampled, and was absent only at one station, which was the most offshore station sampled during the cruise. Although polyunsaturated aldehydes (PUAs) were not detected, other oxylipins which are hydroxy and keto derivatives of eicosapentaenoic and docosahexaenoic acids that affect copepod reproduction were found in these samples. Hence, we can attribute the negative impact of diatoms not only to PUAs, as previously believed, but also to these compounds. This is the first direct evidence of the presence of oxylipins other than PUAs in marine blooms dominated by diatoms.  相似文献   

7.
Seagrass meadows provide important nursery and feeding grounds for many commercially valuable fish species. Here, we address the paucity of published information on the status of seagrasses in Madagascar by documenting the results from ecological surveys of 11 seagrass beds in Velondriake, a locally managed marine area (LMMA) in south-west Madagascar. The diversity and coverage of meadows was highest in the north of the LMMA with up to 51% coverage, and lowest in the south (26%). Overall, eight seagrass species were recorded: Cymodocea rotundata, C. serrulata, Halodule uninervis, Halophila ovalis, H. stipulacea, Syringodium isoetifolium, Thalassia hemprichii and Thalassodendron ciliatum. We discuss the natural and anthropogenic factors that may account for the observed low diversity of seagrasses in southern Velondriake, including overfishing, beach-seining, cyclones, siltation and mangrove deforestation. Based on these baseline surveys, as well as discussions with local communities, it is recommended that measures should be taken to reinforce efforts to ban beach-seines and that the role of seagrasses as carbon sinks and potential sustainable financing options through blue carbon initiatives should be investigated through further, more detailed surveys.  相似文献   

8.
Some fish and crustacea caught near the northeastern Mediterranean coast of Turkey between 1977 and 1980 have been analysed by the AAS technique for their H Hg, Cd, Pb, Zn, Cu, Fe, Ni, Cr and Mn contents. In the crustacea Portunus pelagicus (crab) and Penaeus keratherus (shrimp), the two essential elements Zn and Cu, showed a linear correlation. Among the bony fish, Upeneus moluccensis (gold band goat fish), a member of the Mullidae family, and Portunus pelagicus showed a much greater tendency to accumulate Hg than other species. Although Cr concentrations in the sediments of the area studied were high, Cr levels in the organisms studied were found to be relatively low. The highly toxic metals Hg, Cd and Pb were found to be present in concentrations lower than those reported from other areas of the Mediterranean.  相似文献   

9.
We evaluated the effectiveness of chemical tagging with the fluorescent marker calcein for two key species of herbivorous sea urchins, Diadema africanum and Paracentrotus lividus, to facilitate medium‐ and long‐term ecological experiments. In total, 98 juveniles of D. africanum and 98 P. lividus were tagged with this fluorescent marker, with 12 combinations of different tagging techniques (chemical bath or injection), concentrations of calcein (2, 10 and 20 mg · l?1), and soaking times (2, 4 and 24 h). Respective control treatments were conducted by means of seawater injection and bathing. The success of tagging was assessed after a month of feeding individuals ad libitum with the algae Dictyota sp. Sea urchins were dissected and their Aristotle's lanterns cleaned with 10% sodium hypochlorite to examine these structures under UV light using a binocular microscope. Each species was evaluated in terms of survival, percentage of tagged individuals and intensity of the resulting tag. The results showed that the method of soaking individuals of both species for 24 h in concentrations of calcein of 10 and 20 mg · l?1 gave the highest percentage survival (100%) and the resulting tags were clearly visible.  相似文献   

10.
对广西沿岸海草优势种日本大叶藻（Zostera japonica）根状茎、幼叶、成熟叶和老叶的灰分含量、干质量热值和去灰分热值进行了初步研究。结果表明, （1） 日本大叶藻叶片从幼叶到成熟叶再到老叶的生长发育过程中, 灰分含量升高, 而干质量热值和去灰分热值下降; （2） 日本大叶藻根状茎的灰分含量和去灰分热值大于叶片...  相似文献   

11.
During the past 20 years, experimental cruises have been conducted around the Canary Islands (North-West Africa) to investigate the biodiversity of the deep-sea ecosystem and to explore new fisheries resources. Although pandalid shrimps were shown to be very abundant in this region, information is lacking regarding the best fishing method for catching the different species of shrimp. Here, two types of traps were tested, a semi-floating shrimp trap and a traditional bottom trap, in an effort to improve the fishing gear effectiveness and to reduce the capture of non-target species. In total, nine species were captured, which were categorised into three main groups based on their depth of capture: Plesionika edwardsii, P. narval and P. holtuisi (100–400 m); P. ensis, P. martia, P. williamsi and Heterocarpus ensifer (400–800 m); and H. grimaldii and H. laevigatus (800–1 300 m). Significant differences were found in the capture of the different species: P. narval, P. ensis, P. edwardsii and H. ensifer were captured more readily using the semi-floating traps, whereas P. martia, P. williamsi, H. grimaldii and H. laevigatus were caught more efficiently with traditional bottom traps. This intra-specific difference in their capture was considered to be due to the differential motility of the species in the water column. There were indications that P. edwardsii and H. ensifer are an unexploited resource that has the potential to support a viable and sustainable fishery using semi-floating shrimp traps. Furthermore, the deeper-dwelling pandalid shrimps, H. laevigatus and H. grimaldi, could be a secondary target species using bottom traps.  相似文献   

12.
The impact of sediment burial and erosion on seagrasses: A review   总被引：1，自引：0，他引：1  
  相似文献   

13.
We measured tissue phosphorus content of high and low intertidal Hormosira banksii to test the hypothesis that tissue phosphorus content would be greater in individuals from the low intertidal because of greater total uptake associated with longer immersion in seawater. Moreover, we predicted that tissue phosphorus would be greater at sites where the seawater contained higher phosphate concentrations. There was a positive, linear relationship between local seawater phosphate concentrations and tissue phosphorus content of H. banksii from high and low intertidal zones at six different sites in winter. However, there were no comparable relationships in summer, even though the range of seawater phosphate concentration was similar in both seasons. The phosphorus contents of low intertidal H. banksii were significantly greater than high intertidal H. banksii in winter, but not in summer. Reasons for these differences may be related to greater access to seawater phosphate in low intertidal algae (than those in the high intertidal) in winter, followed by greater utilisation of the internal phosphorus between winter and summer, due to faster growth rates in the low intertidal.  相似文献   

14.
This study investigated the occurrence of Acartia copepods and their environmental characteristics to identify the existence and survival of foreign species at domestic ports in Korea. Copepods samples were collected seasonally, and temperature, salinity, dissolved oxygen (DO), total suspended solids (TSS), and chlorophyll-a (chl-a) were measured at the seaports Incheon, Gwangyang, and Ulsan from 2007 to 2009. No foreign species was found and all of the Acartia copepods observed had been recorded in Korean waters previously. Acartia omorii, A. hongi, and A. pacifica were found at all three seaports, whereas portspecific species were found at Incheon (A. sinjiensis) and Ulsan (A. steueri, A. negligens, and A. danae). When chl-a and DO were not limited, eurythermal and euryhaline A. hongi, A. omorii, and A. hudsonica occurred at TSS concentrations between 38 and 183 mg·L−1, while warm-water copepods (A. pacifica, A. ohtsukai, A. sinjiensis, and A. erythraea) occurred at TSS concentrations <80 mg·L−1. The seasonal distributions of A. omorii, A. hongi, and A. pacifica at the three seaports were most significantly explained by temperature, salinity, DO, and TSS, and not chl-a. The variation in A. hudsonica and A. sinjiensis at Incheon was explained mainly by temperature, DO, and TSS, whereas A. erythraea at Ulsan was influenced only by chl-a. The occurrence of Acartia copepods showed spatiotemporal variation as a result of species-specific preferences or tolerances in each port environment. Multiple regression analysis indicated that temperature, salinity, DO, and TSS were better predictors of the variation in Acartia species at the seaports during the study than chl-a when food was not limiting. These results indicated that the occurrence of Acartia copepods and related environmental characteristics are crucial information for differentiating foreign species from the native community and predicting the potential for foreign copepods to become established after their introduction to a seaport.  相似文献   

15.
Samples were collected with a plankton net in the four seasonal cruises during 2006-2007 to study the seasonal variability of the zooplankton community in the southwest part of Huanghai Sea Cold Water Mass (HSCWM, Yellow Sea Cold Water Mass). The spatial and temporal variations of zooplankton species composition, biomass, abundance and biodiversity were examined. A total of 122 zooplankton species and 30 pelagic larvae were identified in the four cruises. Calanus sinicus and Aidanosagitta crassa were the most dominant species, and Themisto gaudichaudi and Euphausia pacifica were widely distributed in the HSCWM area. The spatial patterns of non-gelatinous zooplankton (removing the high water content groups) were similar to those of the total zooplankton biomass in autumn, but different significantly in the other three seasons. The seasonal means of zooplankton biomass in spring and summer were much higher than that in autumn and winter. The total zooplankton abundance averaged 283.5 ind./m~3 in spring (highest), 192.5 ind./m~3 in summer, 165.5 ind./m~3 in autumn and 65.9 ind./m~3 in winter (lowest), and the non-gelatinous groups contributed the most total abundance. Correlation analysis suggests that the non-gelatinous zooplankton biomass and abundance had a significant positive correlation in the whole year, but the relationship was insignificant between the total zooplankton biomass and abundance in spring and summer. The diversity index H of zooplankton community averaged 1.88 in this study, which was somewhat higher than historical results. Relatively low diversity in summer was related to the high dominance of Calanus sinicus, probably due to the strongest effect of the HSCWM in this season.  相似文献   

16.
Distributional characteristics of dinoflagellate cysts in surface sediments were investigated in relation to environmental factors in the eastern part of Geoje Island, Korea. Samples were collected from 10 stations in February of 2004 and water temperature and salinity were measured in February, May, September and November of 2004. Total 30 taxa of dinoflagellate cysts were identified representing 19 genera, 28 species and 2 unidentified species. Among these dinoflagellate cysts,Brigantedinium spp. of which relative proportion in the total dinoflagellate cysts was 23.5%, was the most abundant at all stations except St. 1, and was followed bySpiniferites bulloideus (8.6%),Lingulodinium machaerophorum (8.2%) andDiplopsalis lenticula (6.7%). In addition, ellipsoidal cysts of the genusAlexandrium (Alexandrium catenella - tamarense type) andGymnodinium catenatum, known to be causative organisms for PSP, occurred with high concentrations.Scrippsiella trochoidea was also found; however, its cyst concentration was low. Generally, species composition in the study area was similar to these reported from Jinhae Bay and Busan Harbor and several dinoflagellate cysts reflected the eutrophic condition. Cyst distribution in the eastern part of Geoje Island seems to be influenced by the Tsushima Warm Current flowing from the southwest. The mean water temperature was 12.0°C in February, 14.7°C in May, 20.9°C in September and 17.2°C in November, which was most favorable forAlexandrium spp. growth. The abundances of dinoflagellate cysts ranged from 528 to 2,834 cysts/g dry sediment. Higher concentrations were recognized in sediments of west area of the Jisimdo than at other stations. The cyst composition of this area was closely related to these of Jinhae Bay and Busan Harbor from which currents flow into this area. Higher cyst concentration in the west area of Jisimdo might be due to formation of the gyre.  相似文献   

17.
Fauna species living in seagrass meadows depend on different food sources, with seagrasses often being marginally important for higher trophic levels. To determine the food web of a mixed-species tropical seagrass meadow in Sulawesi, Indonesia, we analyzed the stable isotope (δ13C and δ15N) signatures of primary producers, particulate organic matter (POM) and fauna species. In addition invertebrates, both infauna and macrobenthic, and fish densities were examined to identify the important species in the meadow. The aims of this study were to identify the main food sources of fauna species by comparing isotopic signatures of different primary producers and fauna, and to estimate qualitatively the importance of seagrass material in the food web. Phytoplankton and water column POM were the most depleted primary food sources for δ13C (range −23.1 to −19.6‰), but no fauna species depended only on these sources for carbon. Epiphytes and Sargassum sp. had intermediate δ13C values (−14.2 to −11.9‰). Sea urchins, gastropods and certain fish species were the main species assimilating this material. Seagrasses and sedimentary POM had the least depleted values (−11.5 to −5.7‰). Between the five seagrass species significant differences in δ13C were measured. The small species Halophila ovalis and Halodule uninervis were most depleted, the largest species Enhalus acoroides was least depleted, while Thalassia hemprichii and Cymodocea rotundata had intermediate values. Fourteen fauna species, accounting for 10% of the total fauna density, were shown to assimilate predominantly (>50%) seagrass material, either directly or indirectly by feeding on seagrass consumers. These species ranged from amphipods up to the benthic top predator Taeniura lymma. Besides these species, about half of the 55 fauna species analyzed had δ13C values higher than the least depleted non-seagrass source, indicating they depended at least partly for their food on seagrass material. This study shows that seagrass material is consumed by a large number of fauna species and is important for a large portion of the food web in tropical seagrass meadows.  相似文献   

18.
In the coastal waters of Johor Straits, Peninsular Malaysia, the dugongs occur and their habitat suitability model has yet not been attempted, while it could be critical information for developing their conservation strategies. This study derived spatially explicit dugong population information on the abundance and distribution of dugongs based on fisher surveys. The survey revealed the highest dugong abundance around eastern areas, followed by southern areas of Johor Straits. Degradation of seagrass habitat, which dugong uses as feeding ground, could be the main reason for reducing dugong sighting around western areas. A habitat suitability map was produced based on dugong presence and interacting environmental factors such as seagrass biomass, distance from shoreline, and water depth. Using ArcGIS mapping capability, the data layers on those environmental factors were fied into MaxEnt. The MaxEnt model output showed seagrass biomass as the highest contributing factor to the likelihood of dugong presence. The model also estimated 20 kg/m2 of seagrass biomass, 3 km distance from shoreline and a water depth of 25 m as the optimum habitat condition for dugong population. The combination of fisher interview, habitat suitability, and risk modeling has the ability to provide adequate information required for monitoring and developing policy strategies for sustainable management and conservation of marine mammals.  相似文献   

19.
Abstract

Common native fish species that are rare in New Zealand rivers with high suspended solids (SS) concentrations were identified to determine which species were likely to be most affected by high SS concentrations. Mortality rates for the three most sensitive species (banded kokopu Galaxias fasciatus, redfin bully Gobiomorphus huttoni, common smelt Retropinna retropinnd) were measured over a range of SS concentrations to identify lethal concentrations. The survival of banded kokopu and redfin bully was not reduced by SS concentrations up to 43 000 g m?3; however, the 24‐h survival of common smelt was reduced by SS concentrations over 1000 g m?3, and its median lethal concentration (LC50) was close to 3000 g m?3. SS concentrations over 3000 g m?3 for more than 24 h will therefore reduce smelt but not affect the mortality of most other common native fish species. Although mortality from high concentrations of SS can account for the scarcity of smelt in rivers with high SS concentrations, mortality from high SS does not explain the scarcity of banded kokopu or redfin bully in such rivers. High turbidity (>20 nephelometric turbidity units) is known to limit the upstream migration and recruitment of juvenile banded kokopu in rivers with increased SS concentrations. Banded kokopu is therefore affected by increased turbidity from SS rather than lethal SS concentrations. As redfin bully were not affected by either high turbidity levels or high SS concentrations, the low abundance of this species in rivers with high SS concentrations is likely to be related to the siltation of benthic habitats.  相似文献   

20.
Parameters of community structure (species composition and relative abundance, number of taxa, diversity, evenness, and cell density) were measured for a mudflat diatom community in the Avon‐Heathcote estuary, New Zealand. Fifty three diatom species were identified: 25 taxa (species and varieties) are new New Zealand records. The Shannon‐Wiener information index (H') was 3.46, indicating high diversity. Evenness (J') ranged from 0.57–0.67. The association between the biomass of the pulmonate gastropod, Amphibola crenata, and benthic diatom community structure was studied using large open enclosures (4.0 m2) to manipulate snail biomass. Community structure was compared at 0, 5 (natural biomass), and 10 g A. crenata dry weight per m. A similarity index (SIMI=0.88–0.95), as well as H’ and J’ indicated close similarity between the diatom assemblages within all enclosures, but number of taxa increased from 33 to 49 with increasing snail biomass. Cell densities were significantly lower at high snail biomass (6088 valves per mm2) compared to enclosures with no snails (10 110 valves per mm ). A. crenata had a higher ratio of diatom fragments to whole diatom valves in its faeces (2.42) than in its crop (0.55), indicating that it is capable of fragmenting diatoms.  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