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1.
Toward assessing the biogeochemical significance of seaweeds in relation to dissolved iodine in seawater, the effect of whole seaweeds (Laminaria digitata and Fucus serratus) upon iodide and iodate, at essentially natural concentrations, has been studied. The weeds were carefully removed from the sub-littoral zone of the Menai Straits and exposed to iodide and iodate at their natural temperature (6 °C), but under continuous illumination. Laminaria digitata was found to decrease the concentration of iodate with an exponential rate constant of 0.008–0.24 h−1. This is a newly discovered process which, if substantiated, will require an entirely new mechanism. Generally, apparent iodide concentration increased except in a run with seawater augmented with iodide, where it first decreased. The rate constant for loss of iodide was 0.014–0.16 h−1. Meanwhile, F. serratus was found not to decrease iodate concentrations, as did L. digitata. Indeed, after ∼30 h iodate concentrations increased, suggesting that the weed may take in iodide before oxidising and releasing it. If substantiated, this finding may offer a way into one of the most elusive of processes within the iodine cycle – iodide oxidation. With both seaweeds sustained long-term increases of apparent iodide concentration are most easily explained as a secretion by the weeds of organic matter which is capable of reducing the Ce(IV) reagent used in determination of total iodine. Modelling of the catalytic method used is provided to support this contention. The possibility of developing this to measure the strain that seaweeds endure in this kind of biogeochemical flux experiment is discussed. A Chemical Oxygen Demand type of approach is applied using Ce(IV) as oxidant. The results of the iodine experiments are contrasted with the several investigations of 131I interaction with seaweeds, which have routinely used discs of weed cut from the frond. It is argued that experiments conducted with stable iodine may measure a different variable to that measured in radio-iodine experiments.  相似文献   

2.
Kelps of the genus Laminaria accumulate iodine at high concentrations, but the iodine retaining capacity can be affected by emersion and physiological stress. In this study, I2 emission into the atmosphere from Laminaria digitata and Laminaria hyperborea was compared under controlled low irradiances and temperatures. The two species exhibited different I2 emission rates as blades of L. digitata emitted I2 at rates five times higher than those from newly-grown blades (current growth season) of L. hyperborea. I2 emission was not detectable from old blades (previous growth season) of L. hyperborea. Additionally, effects of irradiance and temperature on both I2 emission into air and net I− release into seawater where assessed for L. digitata while monitoring photo-physiological parameters as stress indicators. Irradiances between 30 and 120 μmol photons m−2 s−1 had only marginal effects on both I2 emission and I− release rates, but physiological stress, indicated by photoinhibition, was observed. The results suggest that the irradiances applied here were not stressful enough to impact on the iodine release. By contrast, at elevated temperatures (20 °C), photoinhibition was accompanied by an increase in I2 emission rates, but net I− release rates remained similar at 10–20 °C. High I2 emission rates into air and I− release into seawater observed from L. digitata underpin the fundamental function of this kelp as mediator of coastal iodine fluxes.  相似文献   

3.
The present study is the first to compare trophic relationships of several co-occurring phytal harpacticoid species, in their natural habitat, using both δ13C and δ15N signatures. Three phytal harpacticoid species/taxa (Zaus spinatus, Tisbe spp., and Parathalestris cf. intermedia) all collected from the alga Fucus serratus, at different times of the year, were analyzed. The results indicated that the harpacticoids were utilizing food sources differently. Specific food sources of the three species/taxa could not be accurately pinpointed, but there were strong indications that F. serratus and fragments from it did contribute significantly to the diet of P. cf. intermedia and Tisbe spp. Both of these harpacticoid species overlapped in δ13C and δ15N values with some of the macrofaunal species, collected from the same site in Hvassahraun, Iceland, while no overlap was seen for Z. spinatus. The signatures for Z. spinatus indicated that its food sources changed seasonally.  相似文献   

4.
The intertidal serrated wrack, Fucus serratus L. (Fucales: Phaeophyceae), has become an abundant canopy-forming alga along a ca. 100 km stretch of shore in southwestern Iceland in the last century. Its distribution has not changed noticeably since a survey in 1975/1976. Many experimental studies have shown that canopy-forming algae can have profound effects on the community structure. Although such experiments involving F. serratus are few it was decided to test predictions from these experiments on a geographical scale by comparing community compositions within the area where F. serratus is a dominant algae (since at least 1975/1976) with an adjacent area of similar size where F. serratus is absent (with a single exception without consequences). The work is based on measurements on some 372 stations in the F. serratus area, termed region A, and 227 stations from the F. serratus-free area, termed region B. Percentage cover of algae and sessile invertebrates was estimated on 2 m2 on each station and animals collected from 800 cm2 from each station. The vertical distribution of F. serratus was most similar to that of Fucus distichus and the two species often grew intermingled on the lower part of the shore. F. serratus appeared to have reduced the cover of F. distichus in the lowermost part of the shore, while having little or no effect on other canopy-forming species. The low abundance of Semibalanus balanoides in the F. serratus area (region A) is in line with experiments showing detrimental effect on this barnacle by whiplash of F. serratus. In general algal grazers were more abundant in region A, consistent with the greater attractiveness of F. serratus than other canopy-forming species to grazers, although this may be partly explained by the abundance of understorey algae in region A.  相似文献   

5.
Multiple stable isotope analyses were used to examine the trophic shifts at faunal assemblages within the invading macroalga Caulerpa racemosa in comparison to established communities of Posidonia oceanica seagrass meadows. Sampling of macrobenthic invertebrates and their potential food sources of algal mats and seagrass meadows in Mallorca (NW Mediterranean) showed differences in species composition of faunal and primary producers among seagrass and C. racemosa. Accordingly, changes in food web structure and trophic guilds were observed, not only at species level but also at community level. The carbon and nitrogen isotope signatures of herbivores, detritivores and deposit feeders confirmed that the seagrass provided a small contribution to the macrofaunal organisms. δ13C at the P. oceanica seagrass and at the C. racemosa assemblages differed, ranging from −6.19 to −21.20‰ and −2.67 to −31.41‰, respectively. δ15N at the Caulerpa mats was lower (ranging from 2.64 to 10.45‰) than that at the seagrass meadows (3.51–12. 94‰). Significant differences in isotopic signatures and trophic level among trophic guilds at P. oceanica and C. racemosa were found. N fractionation at trophic guild level considerable differed between seagrass and macroalgae mats, especially for detritivores, deposit feeders, and herbivores. Filter feeders slightly differed with a relatively lower N signal at the seagrass and CR values at community level and at trophic guild level were higher in the C. racemosa invaded habitats indicating an increase in diversity of basal resource pools. C. racemosa did seem to broaden the niche diversity of the P. oceanica meadows it colonised at the base of the food web, may be due to the establishment of a new basal resource. The extent of the effects of invasive species on ecosystem functioning is a fundamental issue in conservation ecology. The observed changes in invertebrate and macrophytic composition, stable isotope signatures of concomitant species and consequent trophic guild and niche breadth shifts at invaded Caulerpa beds increase our understanding of the seagrass systems.  相似文献   

6.
The present study focuses on horizontal spatial variability of benthic macrofauna associated with Patella ferruginea. Thirty-six samples collected at 12 transects belonging to 4 midlittoral sites along the rocky Tunisian coastline, were examined. A total of 44 species belonging to 5 taxa were found. Multivariate analysis applied on gathered data did not show a horizontal spatial variability at small scale (between transects), but at large scale, between sites as well as sectors. Thus, three groups of communities were identified (GI: Korbous and El Haouaria; GIIa: Zembra Island and GIIb: Kelibia). The distribution of species abundance within these groups revealed that crustaceans were the most abundant taxon, due to the overwhelming dominance of Chthamalus stellatus. This substratum appeared to create favourable micro-habitats for the installation of molluscs including gastropods. Regarding the low diversity index (H') and evenness (J), they seemed to reflect a disturbance and a demographic unbalance within these communities. The heterogeneity of substrate surface, created by C. stellatus specimens appeared to be caused by various complex interactions established between the key components of these communities in particular suspension feeders, predators, herbivorous molluscs and macroalgae. Thus, the dynamic status of each of these communities is the result of these complex interactions.  相似文献   

7.
夏光远  王德祥 《海洋学报》2017,39(4):89-100
海绵动物具备很强的愈伤再生能力。荔枝海绵是海绵动物中比较特殊的类群,它有皮质层细胞（cortex）和领细胞层细胞（choanoderm）的初步分化。本文对荔枝海绵的形态结构进行观察,并通过切割的方法,有针对性地移除荔枝海绵的特定结构,观察其愈伤过程,以期了解海绵愈伤过程的主要变化及各部分在愈伤过程中的作用。结果发现,愈伤过程发生的主要变化为未受创部分的细胞向受创部分迁移导致的细胞重新排布;其身体结构中的领细胞层和皮质层对其生存愈伤是必要的,而骨针核心对其愈伤影响较小。  相似文献   

8.
Macroalgae contribute to intertidal food webs primarily as detritus, with unclear implications for food web studies using stable isotope analysis. We examined differences in the thallus parts of two South African rhodophytes (Gelidium pristoides and Hypnea spicifera) and changes in overall δ13C, δ15N signatures and C:N ratios during degradation in both the field and laboratory. We hypothesized that both degrading macroalgal tissue and macroalgal-derived suspended particulate material (SPM) would show negligible changes in δ13C, but enriched δ15N signatures and lower C:N ratios relative to healthy plants. Only C:N laboratory ratios conformed to predictions, with both species of macroalgae showing decomposition related changes in δ13C and significant depletions in δ15N in both the field and laboratory. In the laboratory, algal tissue and SPM from each species behaved similarly (though some effects were non-significant) but with differing strengths. Gelidium pristoides δ13C increased and C:N ratios decreased over time in tissue and SPM; δ15N became depleted only in SPM. Hypnea spicifera, δ13C, δ15N and C:N ratios all decreased during degradation in both SPM and algae.  相似文献   

9.
This study was performed in order to obtain information on the influence of an acute anoxic event (September, 1997) on distribution and speciation of inorganic iodine in the water column of a small, intensely eutrophicated salt lake. The variations in iodate and iodide depth distributions during the investigated period (1998–2000) were in accord with seasonal changes in redox conditions. During the stratification period (spring and summer), the concentration ratio between iodate and iodide in the upper layers was high, whereas during late summer and autumn, as a result of water column de-stratification and mixing of highly reducing deep water with the oxic layer, lower ratios and more uniform depth distributions were observed.The massive mortality of lake organisms induced by anoxic conditions and sulphide presence throughout the water column was registered by the end of September 1997, when overturn of the lake occurred. The concentrations of iodate in the oxic upper layers were elevated for more than a year after the mass-mortality event (up to 0.55 μmol L−1), whereas iodide concentrations remained high for more than 2 years in deep anoxic water (up to 2.27 μmol L−1). These data suggest that biogeochemical renewal processes affecting the concentrations of inorganic iodine in the lake water are slow compared to those that govern the speciation of iodine. The role of sediment–water interactions and iodine-rich organic species in the production of iodide are discussed.  相似文献   

10.
Characteristic flora and fauna that are highly sensitive to disturbances colonize coastal detritic bottoms in the Mediterranean Sea. In the present study, a comparison of the assemblage composition and colonization by invasive macroalgae was made between two coastal detritic macrophyte assemblages, one dominated by rhodoliths (free-living non-geniculate Corallinales) and the other dominated by fleshy algae, in an area that has been exposed to important levels of anthropogenic disturbance, mainly pollution (including changed sedimentation regimes) in the recent past (bay of Marseilles, France). In comparison with less strongly impacted Mediterranean regions, the macrophyte assemblages in the bay of Marseilles were characteristic in terms of species identity and richness of coastal detritic macrophyte assemblages. However, extremely low species abundance (cover) was observed. As far as invasive species were concerned, Caulerpa racemosa var. cylindracea was only abundant in the rhodolith assemblage whereas the two invasive Rhodophyta Asparagopsis armata and Womersleyella setacea were mainly found in the fleshy algae assemblage. The seasonality observed in the Rhodolith assemblage seemed to be related to the development of C. racemosa var. cylindracea and did not follow the typical pattern of other Mediterranean assemblages. This study represents the first study of coastal detritic assemblages invaded by C. racemosa var. cylindracea.  相似文献   

11.
Acid digests of three common marine macroalgae (Fucus serratus, Enteromorpha spp., Porphyra umbilicalis) exhibit substantial mutagenic activity for Salmonella typhimurium strains TA98 and TA100 in the microtire fluctuation test. Although these algae are known to concentrate heavy metals, the mutagen(s) is probably an organic compound(s).Collections of these three marine macroalgae were made along the Gower coast of Wales, Great Britain, at distances between 8·0 and 32·0 km from the industrial center of Swansea-Port Talbot. When tested for mutagenicity with TA98, the acid digests of F. serratus and Enteromorpha spp. showed an inverse relationship between activity and distance from Swansea-Port Talbot. This relationship was not observed with P. umbilicalis or with any of the digests when tested with TA100.These data are consistent with the hypothesis that Swansea-Port Talbot is a point emitter for contaminants which are mutagenic for TA98 and are accumulated by Enteromorpha and Fucus.  相似文献   

12.
Numerous studies suggest that floating macroalgae contribute to population connectivity of the algae themselves as well as of associated organisms. In order to evaluate the importance of floating macroalgae for population connectivity in southern Chile we analysed their spatial and temporal distributions. We estimated the abundance of floating kelp in the Interior Sea of Chiloé and the Los Chonos Archipelago via ship surveys conducted during austral spring (November) and winter (July) of the years 2002–2005. Highest densities of floating kelp (Macrocystis pyrifera and Durvillaea antarctica) were found during spring. Generally, the density of floating kelp was relatively low in areas with high supply of freshwater, and highest abundances were found in large channels opening to the open ocean. We suggest that this pattern is caused by the scarcity of natural kelp beds combined with rapid degradation of floating kelp in the interior fjords and by seaward surface outflow. The maximum densities of floating kelps were found in an area known to be an extensive convergence zone (i.e. estuarine front), which appears to act as a retention zone. In accordance with this distribution pattern, we propose that connectivity between local populations via floating kelp is higher in the outer channels with oceanic influence than in the inner fjords with high freshwater influx.  相似文献   

13.
The abiotic disturbance of urban wastewater discharge and its effects in the population structure, plant morphology, leaf nutrient content, epiphyte load and macroalgae abundance of Zostera noltii meadows were investigated in Ria Formosa coastal lagoon, southern Portugal using both univariate and multivariate analysis. Four sites were assessed, on a seasonal basis, along a gradient from a major Waste Water Treatment Works (WWTW) discharge to a main navigation channel. The wastewater discharge caused an evident environmental disturbance through the nutrient enrichment of the water and sediment, particularly of ammonium. Zostera noltii of the sites closest to the nutrient source showed higher leaf N content, clearly reflecting the nitrogen load. The anthropogenic nutrient enrichment resulted in higher biomass, and higher leaf and internode length, except for the meadow closest to the wastewater discharge (270 m). The high ammonium concentration (158–663 μM) in the water at this site resulted in the decrease of biomass, and both the leaf and internode length, suggesting a toxic effect on Z. noltii. The higher abundance of macroalgae and epiphytes found in the meadow closest to the nutrient source may also affect the species negatively. Shoot density was higher at the nutrient-undisturbed site. Two of the three abiotic processes revealed by Principal Component Analysis were clearly related to the WWTW discharge, a contrast between water column salinity and nutrient concentration and a sediment contrast between both porewater nutrients and temperature and redox potential. A multiple regression analysis showed that these abiotic processes had a significant effect on the biomass-density dynamics of meadows and on the overall size of Z. noltii plants, respectively. Results show that the wastewater discharge is an important source of environmental disturbance and nutrients availability in Ria Formosa lagoon affecting the population structure, morphology and N content of Z. noltii. This impact is spatially restricted to areas up to 600 m distant from the WWTW discharge, probably due to the high water renewal of the lagoon.  相似文献   

14.
研究了石斑鱼肠道原籍嗜冷杆菌SE6在体外的抑菌特性及对人工胃肠液的耐受特性,在此基础上研究了饲料中添加SE6(108CFU/g)对斜带石斑鱼生长性能和免疫功能的影响。体外试验结果表明:SE6对副溶血弧菌、哈维氏弧菌、梅氏弧菌和金黄色葡萄球菌等常见水产致病菌均有一定的抑制作用。pH为4.0的人工胃液能促进SE6的生长,处理2和4 h存活率分别为110.7%和173.0%;pH为3.0的人工胃液处理2 h后活菌数为1.59×105 CFU/cm3,存活率为1.36%,但SE6不能耐受pH为2.0的人工胃液。经浓度分别为0.1%,0.3%,0.5%和0.7%的胆盐处理3 h后,SE6的存活率分别为89.17%,88.33%,77.17%和12.33%。动物试验结果显示:投喂SE6 60 d后试验组饵料系数(0.95±0.01)显著低于对照组(1.03±0.02)。试验组血清补体C3在试验全期均高于对照组,补体C4含量在投喂SE6 60 d时显著上升。血清IgM含量在投喂30 d时显著上升。总之,嗜冷杆菌SE6能抑制多种常见病原菌的生长,而且对模拟胃肠道环境具有一定的耐受能力,添加到饲料中能显著提高石斑鱼饵料利用率,增强动物的免疫功能。  相似文献   

15.
At regional scales, the distribution of species and the structure of assemblages vary with latitude within many marine and terrestrial systems. The oligotrophic coastal waters of Western Australia (WA) support highly speciose and endemic assemblages, yet spatial patterns in benthic structure are currently poorly known. We examined benthic assemblage composition along a latitudinal gradient of 28.5–33.5°S and a depth gradient of 14–62 m, on subtidal reefs in warm-temperate WA. We surveyed benthos using a remotely triggered digital stills camera. In total, we sampled macroalgae and sessile invertebrates at 201 sites spread across four locations. Percent cover of coarse taxonomic groups and dominant species was estimated from over 2000 photoquadrat samples. We recorded significant differences in benthic assemblage composition between locations, and along depth gradients within each location. However, the magnitude of change with depth was not consistent between locations, and shifts in assemblage composition along the depth gradients were not as pronounced as expected. The percent cover of all dominant benthic groupings differed between locations, and several key taxa, such as the kelp Scytothalia dorycarpa, brown foliose macroalgae, hard corals and sponges, changed predictably along the latitudinal gradient. Our study adopted a coarse taxonomic, but assemblage-wide, approach to describing macrobenthic assemblages, and clear differences between locations and depths were detected. The surveys have provided baseline data on broad scale ecosystem structure against which to detect future ecological change.  相似文献   

16.
Dissolved iodine in waters overlying and in the Orca Basin,Gulf of Mexico   总被引：1，自引：0，他引：1  
The distribution and speciation of iodine, a biophilic redox-sensitive trace element, in waters overlying and in the Orca Basin, Gulf of Mexico, which contains hypersaline, anoxic and yet non-sulfide-bearing brine have been determined. The distribution of iodate and iodide in the oxic waters overlying the anoxic brine are similar to those reported in other oceans. However, in the oxic-anoxic mixing zone, iodate disappears while the concentration of iodide reaches a maximum of 8.1 μM, the highest concentration ever reported in open oceans. There is also a maximum in specific iodine of 30.7 nM‰?1 at this depth. Specific iodine in oxic seawater is only about 10–14 nM ‰?1. These features may be explained by the preferential dissolution of biogenic particles that have accumulated in a strong pycnocline. In the anoxic brine proper, the concentration of iodide is 3.8 μM and can be explained almost entirely by the simultaneous mobilization of chloride and iodide during the dissolution of evaporite beds as the specific iodine of 14.5 nM‰?1 is only slightly higher than those observed in the oxic waters.  相似文献   

17.
The structure and composition of subtidal rocky seaweed assemblages were studied at 69 sites on the Canary Islands (northeastern Atlantic). This group of islands are situated at the southern boundary of the warm temperate region and adjacent to the cold waters from the northwest African coastal upwelling, which creates a difference of almost 2 °C in surface seawater temperature from the eastern to the western islands. This thermal variation allows an examination of the transition between the warm temperate and the tropical regions along this longitudinal gradient together with the hypothesised Fucales-dominated assemblages towards the eastern islands in contrast to the Dictyotales-dominated assemblages towards the western ones. Environmental and biological parameters were considered in order to investigate which were the main factors explaining spatial variation along the gradient in a multi-scaled approach. Although seventy-nine macroalgae were identified, 87.63% of the total mean cover was due to six taxa (Lobophora variegata, nongeniculate corallines, Canistrocarpus cervicornis, Jania adhaerens, Cystoseira abies-marina and Pseudolithoderma adriaticum). At a large scale, sea urchin density explained the highest variation in seaweed assemblages (26.94%), and its pattern of distribution across the islands. The expected pattern of distribution according to the upwelling distance only occurred in restricted areas of the Canarian Archipelago in absence of herbivore pressure and habitat degradation. Spatial variations within islands (medium scale) were mainly related to wave exposure, while at a small scale these were mostly due to the degree of sedimentation.  相似文献   

18.
本文记录采自福建省东山湾的底栖介形类真喜萤属一新种:多刺真喜萤Euphilomedes spinulosasp.nov对其进行绘图和详细的描述,并与它的相似种非洲真喜萤Euphilomedes africanus(Klie,1940)进行特征比较,确定其新种地位。多刺真喜萤Euphilomedes spinulosasp.nov鉴别特征:(1)左壳腹缘内侧中部具13束短刺毛束;(2)第1、2、4、6对尾叉爪为主爪且细长,第3、5和7~11对尾叉爪为副爪,其中,第3和第5对爪夹于主爪之间;(3)第7附肢末端的开口下缘仅具1弯刺。  相似文献   

19.
Invasions by non-indigenous species (NIS) have been suggested to alter local, regional and global biota on unprecedented scales. To manage NIS, it is pivotal to identify whether a species is introduced or native, but even today the geographical origin of thousands of species worldwide remain uncertain. Most of these ‘cryptogenic species’ are inconspicuous and rare, but in a few instances, they can also be abundant and conspicuous species, with large impacts on community structure. The identification of cryptogenic species, and summarizing information on their most likely origin, is an important task in invasion biology, and can highlight the need for research and management. Here, we document that the gastropod Batillaria australis in the Swan River estuary (Perth, Western Australia) is a conspicuous species of uncertain origin. A literature review combined with new survey data revealed that all evidence point to a recent human-mediated transfer; for example, it is absent from the fossil record, was first collected in 1954, has a low parasite diversity, has increased its population size dramatically in recent times, is separated by >3000 km from conspecifics, has no long-distance dispersal mechanisms, and existing ocean currents run against a natural range extension. Surprisingly, despite political and scientific focus on NIS hardly any ecological data have been published on this species from Western Australia. We show that B. australis is highly abundant in both seagrass beds (424 ± 29 ind m−2) and on unvegetated sand flats (92 ± 22 ind m−2) being orders of magnitudes more abundant than any native gastropod in the Swan River. Experiments showed that high resistance to predation and environmental stress potentially explains its success. From our survey data, we calculated that >3.6 billion invasive snails today occupy the Swan River. This large snail populations support other organisms; for example, almost 1 billion macroalgae are found attached to living B. australis and >100 million hermit crabs occupy its empty shells. Given Battilaria’s high abundance, wide distribution, large size, persistent shells that support other organisms and bioturbating behavior, it seems inescapable that this potential invader has impacted the ecosystem functioning of the Swan River. We argue that the search for abundant species of uncertain origin should continue, and that these species generally should be treated with the same interest as high status invaders to mitigate impacts in already invaded systems and to avoid secondary spread into neighboring ecosystems.  相似文献   

20.
Tracking and quantifying biological dispersal presents a major challenge in marine systems. Most existing methods for measuring dispersal are limited by poor resolution and/or high cost. Here we use geological data to quantify the frequency of long-distance dispersal in detached bull-kelp (Phaeophyceae: Durvillaea) in southern New Zealand. Geological resolution in this region is enhanced by the presence of a number of distinct and readily-identifiable geological terranes. We sampled 13,815 beach-cast bull-kelp plants across 130 km of coastline. Rocks were found attached to 2639 of the rafted plants, and were assigned to specific geological terranes (source regions) to quantify dispersal frequencies and distances. Although the majority of kelp-associated rock specimens were found to be locally-derived, a substantial number (4%) showed clear geological evidence of long-distance dispersal, several having travelled over 200 km from their original source regions. The proportion of local versus foreign clasts varied considerably between regions. While short-range dispersal clearly predominates, long-distance travel of detached bull-kelp plants is shown to be a common and ongoing process that has potential to connect isolated coastal populations. Geological analyses represent a cost-effective and powerful method for assigning large numbers of drifted macroalgae to their original source regions.  相似文献   

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