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1.
Role of Bacteria in the Carbon and Nitrogen Flow between Water-Column and Sediment in a Shallow Marine Bay (Bay of Piran, Northern Adriatic Sea) 总被引：2，自引：0，他引：2
Abstract. The interdependences between phytoplankton standing crop, bacterial biomass and the dissolved organic matter (DOM) pool in the water column were investigated and related to sediment parameters in a shallow marine bay (Bay of Piran, Northern Adriatic Sea) over an annual cycle. Bacterioplankton density varied between 1–10 × 105 cells ml-1 , with lowest density observed in March corresponding to the low Chi a concentrations during this period. Generation times as determined by dialysis incubations ranged between 4h (June) and 82 h (March). Mean bacterial secondary production rates during summer were about 40 mg C m-1 d-1 and 5mg C m-3. d-1 during winter. With a short time lag, DOM concentrations followed the fluctuation in Chi a.
Sediment oxygen demand measurements revealed a mean mineralization rate of about 260 mg C m-2 d-1 during summer and 100–200 mg C m-2 d-1 in winter. Sediment bacterial density varied between 108 - 109 cells g (sediment dry wt)-1 in the top 5 cm sediment layer or, in terms of biomass, 4.3 g C m-l during summer and 0.6 g C m-2 during winter. Highest concentrations of DOM in pore waters were measured in September, coinciding with high rates of sediment oxygen demand. 相似文献
Sediment oxygen demand measurements revealed a mean mineralization rate of about 260 mg C m
2.
M. Mistri 《Marine Ecology》1995,16(3):181-188
Abstract. The gorgonian Lophogorgia ceratophyta thrives in turbid water at Tinetto Rock, La Spezia Gulf, Ligurian Sea. Its age structure suggests that the population is in a steady state; nevertheless, it is difficult to discern whether the main factors controlling this population are biological or event-related. Secondary production was estimated by means of an increment-summation method and yielded 0.54 g ash-free dry weight (AFDW)*m-1 a-1 . This estimate does not take into account biomass losses due to reproductive output and non-lethal predation. Standing stock biomass was 5.44 g AFDW e m-2 . The annual P/B ratio was 0.10 and turnover time about 10a 相似文献
3.
Abstract. The supply of nitrogen (N) often limits the productivity of marine macrophytes. In vitro and in vivo assays of glutamine synthetase (GS) activity were employed to investigate patterns of N assimilation by the Mediterranean seagrass Posidonia oceanica (L.) DELILE. Biomass-specific GS activity wa measured in root tissue, in leaves within a shoot, in shoots collected at two sites during two season and over a depth range of 5–33 m. Root tissue was less important than shoot tissue in assimilating inorganic N in P. oceanica , due both to the small roots' biomass (ca. 3% of total plant biomass and greatly lower (10- to 50-fold) GS activities. While the GS activity and N assimilatory potentia (biomass × GS activity; μmol N-h--1 ) were greatest in leaf 2, leaves 1 and 3–5 assimilated N a significant rates. Shoots from a site characterized by elevated N availability in the winter water column and no significant sediment N reservoir exhibited GS activities that were 9-times higher than shoot from a more oligotrophic site. Shoot GS activities in July increased linearly from 5 to 33 m and wer correlated with light availability as defined by Hsat , (daily period during which photosynthetic reaction are light-saturated). This may represent metabolic compensation by P. oceanica to maintain N influx. Factors contributing to the ecological success of P. oceanica include the ability to assimilate N under conditions of severe light limitation (< 35 μmol photons. m-2 . s-1 ), and metabolic plasticity to ensur the de novo generation of N-containing organic compounds. 相似文献
4.
Abstract. The production of the hymenosomatid crab Elamenopsis kempi was calculated for a period of 18 months from a subtidal area of the Garmat-Ali river, southern Iraq. The highest average individual somatic energy was attained in spring. Maximum population biomass and production were attained by the summer cohort and the minimum values were exhibited by the overwintering cohort. The fluctuations of the average population biomass were followed throughout the sampling period. Average total annual population production was 13.2 g DW · m-2 · a-1 and the P/B ratio was 5.9. These values were compared with those of the most common crustaceans in the region. 相似文献
5.
T. A. Villareal 《Marine Ecology》1995,16(3):259-271
Abstract. Trichodesmium abundance and photosynthetic rates were determined across a transect of the Atlantic Barrier Reef at Carrie Bow Cay, Belize in May 1993 and May-June 1994. A fore reef station receiving oceanic water had a Trichodesmium abundance characteristic of the open Caribbean Sea (≤ 102 colonies m-3 and 104 -- 105 trichomes m-3 ). Several species were present; however, in all cases a sharp decrease in abundance occurred across the reef to the coastal lagoon. At this latter site, virtually no Trichodesmium was present, although a substantial bloom of the diatom Proboscia alata occurred in 1994.
Maximum photosynthetic rates and the initial light-limited slope a were significantly lower in offshore stations than in reef top populations. The increased photosynthetic rates and light-harvesting ability in reef-top populations, as well as the lack of significant photoinhibition, indicated that the Trichodesmium abundance decrease was probably not due to a decline in photosynthetic capacity. Grazing and physical removal rather than a physiological decline were likely mechanisms operating to reduce Trichodesmium abundance in these regions. These data suggest that the Belizean barrier reef is a sink for Trichodesmium transported in from offshore regions. 相似文献
Maximum photosynthetic rates and the initial light-limited slope a were significantly lower in offshore stations than in reef top populations. The increased photosynthetic rates and light-harvesting ability in reef-top populations, as well as the lack of significant photoinhibition, indicated that the Trichodesmium abundance decrease was probably not due to a decline in photosynthetic capacity. Grazing and physical removal rather than a physiological decline were likely mechanisms operating to reduce Trichodesmium abundance in these regions. These data suggest that the Belizean barrier reef is a sink for Trichodesmium transported in from offshore regions. 相似文献
6.
Abstract. Three species of Alvinellidae are found on walls of some hydrothermal chimneys at 13o N on the East Pacific Rise (EPR); numerous epibiotic bacteria were associated with two of these polychaetes, Alvinella pompejana and Alvinella caudata , but not with the third, Paralvinella grasslei. Many studies suggest that chemoautotrophic bacteria play a prominent role in deep-sea hydrothermal vent ecosystems. Particularly important are the intracellular bacteria present in the giant pogonophores and bivalve molluscs.
The abundant epibioses observed on these Alvinella species are unusual and the relationships between these bacteria and the worms are unknown. Previous results, including13 C values, morphological insertion of the bacteria on the epidermis, presence of ribulose biphosphate carboxylase, and fixation of 14 C bicarbonate in some bacteria and in the dorsal epidermis, suggest that a trophic relationship could exist between Alvinella and its epibiotic bacteria. The present study compared the incorporation area of 14 C bicarbonate in the 3 species. Paralvinella , which is devoid of epibiotic bacteria, served as a control. 相似文献
The abundant epibioses observed on these Alvinella species are unusual and the relationships between these bacteria and the worms are unknown. Previous results, including
7.
Abstract. In the water-column of the Gulf of Trieste (Northern Adriatic Sea) flocculent, amorphous aggregates known as marine snow reach maximum density and dimensions up to 20cm in diameter during summer months. Sampling of these fragile macro-aggregates was carried out by SCUBA-divers.
A large detrital component was found to be embedded in an organic matrix together with a large array of intact phytoplankton species. Heterotrophic bacterial density ranged from 2–65 × 108 cells-g-1 (marine snow dry wt) and is therefore of the same order of magnitude as in the surface layer of the sediments of the Gulf. In terms of biomass, bacteria reached only 30–95% of heterotrophic microflagellates.
A mean abundance of marine snow of 5g (marine snow dry wt) m-3 was obtained for the water-column above the pyenolinc. At this boundary layer, however, a mean abundance of about 10g (marine snow dry wt) m-3 led to the formation of a distinct, 10-50cm thick layer. Based on these data and sedimentation rates of marine snow to the pyenoclinc (38 g [marine snow dry wt] m-2 d-1 ) the potential ecological significance of these macro-aggregates for the pelagic system of the Gulf of Trieste is discussed. 相似文献
A large detrital component was found to be embedded in an organic matrix together with a large array of intact phytoplankton species. Heterotrophic bacterial density ranged from 2–65 × 10
A mean abundance of marine snow of 5g (marine snow dry wt) m
8.
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
9.
Abstract. Studies on leaf growth and production were performed in two stands, at depths of 5 m and 22m, in the Posidonia oceanica (L.) D elile bed off Lacco Ameno, Ischia (Gulf of Naples). Experiments were carried out in situ from May 1988 to August 1989 at monthly intervals.
Leaf growth and production profiles differed in the two stands investigated. Growth rates were higher at 5 m, with a peak in autumn (5.8 mg · shoot-1 · d-1 ) and another in March (3.8 mg · shoot-1 · d-1 ). At 22 m the maximum rate occurred in May (3.9 mg · shoot-1 · d-1 ). These differential growth rates resulted in a delayed maximum leaf surface and biomass at the deep stand, where lower irradiance values and different temperature patterns were also found. The biomass of epiphytic algae showed trends similar to those of leaves; however, there were remarkable differences in the values between the two stations and for the two investigated years.
The production data of the present study are compared with those of other reports, and it is shown that growth processes are greatly influenced by physical factors. 相似文献
Leaf growth and production profiles differed in the two stands investigated. Growth rates were higher at 5 m, with a peak in autumn (5.8 mg · shoot
The production data of the present study are compared with those of other reports, and it is shown that growth processes are greatly influenced by physical factors. 相似文献
10.
Seasonal Changes in Nitrogen, Free Amino Acids, and C/N Ratio in Mediterranean Seagrasses 总被引：2，自引：0，他引：2
Abstract. Seasonal changes in nitrogen, free amino acids, and carbon were investigated in the three Mediterranean seagrasses Posidonia oceanica, Cymodocea nodosa , and Zostera noltii. Leaves, rhizomes, roots, as well as dead plant material were analysed separately. Highest N-concentrations were obtained in the winter months, regardless of species or plant part. In contrast to the other two species, the N-content in Posidonia was higher in the rhizomes than in the leaves.
In the investigated species, marked differences in the free amino acid (FAA) composition were detected between species: Proline, lacking in Posidonia , was the main component in Cymodocea. In Posidonia , FAA decreased from 320umol g-1 (dry wt) in leaf sheaths to 1.5 umol g-1 (dry wt) in the leaf tips. The function of proline as a possible storage and/or stress metabolite is discussed.
High C/N values in dead P. oceanica and C. nodosa rhizomes as well as in P. oceanica wrack seem to be related to considerable resistance to decomposition. Low C/N ratios did not increase in detached C. nodosa and Z. noltii leaves, which began to decompose shortly after detachment from the plants. 相似文献
In the investigated species, marked differences in the free amino acid (FAA) composition were detected between species: Proline, lacking in Posidonia , was the main component in Cymodocea. In Posidonia , FAA decreased from 320umol g
High C/N values in dead P. oceanica and C. nodosa rhizomes as well as in P. oceanica wrack seem to be related to considerable resistance to decomposition. Low C/N ratios did not increase in detached C. nodosa and Z. noltii leaves, which began to decompose shortly after detachment from the plants. 相似文献
11.
Abstract. Bacterial (direct and heterotrophic counts, heterotrophic potentials) and organic matter (org C, org N) parameters were studied over 2 years in the surface sediments of 3 stations located on the continental shelf (station A: 15m; station B: 35m) and slope (station C: 910m) in the northwestern Mediterranean Basin.
Although logistic constraints did not allow a satisfactory sampling periodicity in the offshore survey, some seasonal trends were still observable at the deepest station. Variations were quantitatively more important in the two shallow sediments (from 3×102 heterotrophic bacteria – ml-1 in December 1984 to 107 heterotrophic bacteria-ml-1 in March 1986). Epifluorcsccncc direct counts were relatively constant (5×108 cells-ml-1 ), while heterotrophic potentials (with 14 C labelled glucose and glutamic acid) showed a succession of very short pulses over the year. Different concentrations of organic matter (from 0.2% orgC at 15m to 0.8% orgC at 35m) appeared to sustain very similar bacterial numbers. Nevertheless, a certain relation between the seasonal evolution of bacterial and organic matter parameters was discernable. Although depth apparently had no measurable effect on maximal spring bacterial densities, it seemed to lessen the summer and winter decreases in the two shallow stations. 相似文献
Although logistic constraints did not allow a satisfactory sampling periodicity in the offshore survey, some seasonal trends were still observable at the deepest station. Variations were quantitatively more important in the two shallow sediments (from 3×10
12.
Abstract. The gastric evacuation (at 11 o C and 19 o C) and the relation between prey size and fish size of juveniles of Buglossidium luteum and Arnoglossus thori (Pisces, Heterosomata) are studied. The fish were collected at 20 m depth in the Banyuls Bay (France, Western Mediterranean). B. luteum showed a very rapid evacuation rate at 19 o C (2h to 4h for a IgDW meal) and a slower one at 11o C (9h 30min for a IgDW meal). A. thori showed similar rates at both temperatures (6h 20min to 7 h 30 min for a IgDW meal). The relationship between prey size and predator size showed that A. thori always took larger prey than B. luteum. The diet of the latter changes only slightly with the increasing size of the fish. In contrast, the diet of A. thori changes more rapidly towards larger prey. A hypothesis explaining the contradictory evidence concerning the effect of fish and meal size on gastric evacuation is proposed. 相似文献
13.
Abstract. Peyssonnelia bed distribution on continental shelf bottoms of the Balearic Islands (Western Mediterranean) ranges from 40 to 90 m depth. Different species of Peyssonnelia dominate these bottoms and, according to multivariate techniques, two main assemblages have been distinguished: the Peyssonnelia rosa-marina beds and the Peyssonnelia sp. beds, together with some transition samples between Peyssonnelia and maërl beds. Erect red algae are always abundant. Although average yearly irradiance reaching these beds is only 6.4-0.3% of subsurface irradiance, the species richness averages 45 species per sample (1600 cm2 ) and mean biomass is 2835 g dw. m-2 . The high carbonate content of the living algae of these bottoms suggests that they are important contributors to the production of sediments in the Balearic continental shelf. 相似文献
14.
Abstract. seasonal sampling of three stations in Gulbahce Bay Aegean Sea for the zoobenthic organisms associated with a Zostera marina bed was carried out during 1993–94. Temperature, salinity and oxygen were recorded each sampling period. A total of 7 taxonomic groups were determined: Polychaeta was the dominant group comprising 77 % of the total taxa and individuals, followed by Crustacea, Bivalvia and other groups such as Nemertea. Sipuncula, Turbellaria and Phoronida. Of the 108 taxa encountered, the polychaetes Notomastus latericeus and Caulleriella alata accounted for 49 % of the total populations. The species abundance did not show major changes among seasons, with highest values in fall 982 indiv. ·m-2 and lowest in spring 754 indiv. ·m-2 . Diversity and evenness of the samples were relatively high and fairly constant, and were affected by the dominance levels of the species. 相似文献
15.
Stock Evaluation of Three Littoral Echinoid Species on the Catalan Coast North-Western Mediterranean 总被引：2，自引：0，他引：2
Cruz Palacín Xavier Turon Manuel Ballesteros Gonzalo Giribet Salvador López 《Marine Ecology》1998,19(3):163-177
Abstract. We estimated the abundances of the three common littoral echinoid species Paracentrotus lividus, Arbacia lixula and Sphaerechinus granularis in a littoral zone between 0 and 10m depth on the Catalan shores NE Spain. Densities of each species were estimated from a total number of 11 571× 1 m2 sampling units deployed at 152 sites along the 13 zones into which the coast was divided. The surface area available in each of these zones was estimated at the scale of the sampling unit 1 m2 taking into account the fractal dimension of the shore. The stocks individuals > 2cm test diameter of these species for the whole Catalan shore ≅ 300 km, straight-line distance were estimated to be about 279.1 × 106 individuals for P. lividus , 28.9 × 106 individuals for A. lixula and 10.9 × 106 individuals for S. granularis. These sea-urchins are key species in the regulation of algal communities and some of them P. lividus. S. granularis are of commercial interest. This information will provide a tool for the future monitoring and management of this resource, which now faces diverse pressures of human origin. 相似文献
16.
Abstract. The oceanic diatom Rhizosolenia clevei and its cyanobactcrial symbiont Richelia intracel-luluris were isolated into laboratory culture and their biology and growth dynamics examined. Nitrogen-fixation by the symbiont could sustain the symbiosis. Growth and nitrogenase activity demonstrated light saturation kinetics, with no photoinhibition up to 315 μE m-1 s-1 for growth and 780μE m-1 s-1 for nitrogen fixation. The symbiosis is not obligate for Rhizosolenia , which is capable of growth independent of the symbiont if a nitrogen source is available. The symbiont is contained in the pcriplasmic space between the Rhizosolenia plasmalcmma and frustulc, and preliminary evidence suggests excretion of fixed nitrogen into the medium may be occurring. 相似文献
17.
P. Francour 《Marine Ecology》1997,18(2):157-173
Abstract. Observations of the fish fauna of Posidonia oceanica (L.) DELILE seagrass beds were undertaken in two shallow stations and one deeper station in Port-Cros National Park, between November 1984 and September 1987. Demographic structure, density and biomass of the 19 most abundant species or taxa were assessed by several non-destructive sampling methods. The fish assemblages studied were dominated in number and biomass by a small number of species (Labridae: Symphodus ocellatus and S. tinca ; Sparidae: Diplodus annularis and Sarpa salpa ). Large individuals were infrequent and small size class fish were dominant especially in sheltered shallow areas. Recruitment and migrations (shortor long-term) have been identified as the most important causes of abundance variations over the year. The four trophic categories were sampled only in the sheltered shallow zone, where the herbivore Sarpa salpa represents a strong proportion of the fish fauna (40–70%) during summer. The fish assemblages differ between the three seagrass beds, and the depth appears as the most important factor affecting the fish assemblages in P. oceanica . The functional difference between shallow and deeper seagrass beds is therefore discussed. 相似文献
18.
Antonella Penna Maria Grazia Giacobbe Nunzio Penna Francesca Andreoni Mauro Magnani 《Marine Ecology》2002,23(S1):320-328
Abstract. High-biomass blooms of A. taylori Balech have recently been spreading over new Mediterranean areas, with evident adverse effects on the marine ecosystem. In 1999–2000, a new Mediterranean locality was affected by blooms of A. taylori: the West Bay of Vulcano (Aeolian Islands, Tyrrhenian Sea), with maximum cell densities of 1.2 × 107 cells 1−1 in August 1999 and 4.0 × 106 cells 1−1 in August 2000 observed together with yellowish water discoloration. The seawater samples contained high concentrations of nutrients as DIN (Dissolved Inorganic Nitrogen), especially NH3 -N with values of 14.4 μM and TOT-P (Total Phosphorus) with values of 3.2 μM due to the anthropic presence and discharge of untreated sewage. The climatic conditions also seem to influence the occurrence and spreading of the A. taylori blooms in the Vulcano Bay. Clonal cultures of A. taylori , established from Italian and Spanish seawater samples, were used for the sequence analyses of the 5.8S rDNA gene and ITS regions in order to study the genetic variability of different geographical populations of Alexandrium species in the Mediterranean area and to further develop the molecular markers for HAB key-species. 相似文献
19.
Abstract. ω13 C and ω15 N of organic matter sources and consumers were employed to analyse trophic differentiation between a benthic consumer, Gobius niger (L., 1758) (Pisces, Osteichthyes), and a pelagic consumer, Atherina boyeri (Risso, 1810) (Pisces, Osteichthyes) in a Mediterranean coastal lagoon (Lake of Sabaudia) in winter and summer 1999. Trophic differences between the two species throughout the two sampling periods were related to the environmental trophic condition (i. e. nutrient and phytopigment concentrations). Although these two fish have different habitats, they both exploited benthic organisms, above all in summer. When the nutrient and phytopigment concentrations were higher (summer), the most abundant benthic organisms were the main food sources for both species. In winter A. boyeri apparently shifted its feeding preferences to include zooplankton, confirming its opportunistic feeding strategy. Par-ticulate organic matter and algae seemed to play the main trophic role in the food web structure. Benthic invertebrates used both sources, while zooplankton seemed to rely exclusively on the particulate fraction. The overlapping and very depleted signatures of sedimentary and particulate organic matter highlights a strong link between sediments and water column, rarely observed in other aquatic ecosystems using stable isotopes. Such a finding further substantiates the importance of particulate organic matter as a food source in the study area. 相似文献