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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.
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
3.
Feeding of the Sparid Fish Sarpa salpa in a Seagrass Ecosystem: Diet and Carbon Flux 总被引：1，自引：0，他引：1
Abstract. In Revellata Bay Gulf of Calvi, Corsica, France, the sparid fish Sarpa salpa L. is the main macro-consumer of Posidonia oceanica L. D elile leaf. Stomach contents were analysed and 13 C/12 C isotopic ratios were measured in fish muscle and potential food sources algae, P. oceanica leaf and its epiphytes to determine their relative contribution to the fish diet. S. salpa has an age-related mixed diet: juveniles are plankton feeders, young, sub-adults and adults are herbivorous, and, the older the individuals, the higher the relative contribution of P. oceanica to the diet. Our results and former studies of carbon stocks and fluxes in the P. oceanica bed of Revellata Bay have enabled an estimation of the general impact of S. salpa grazing on infralittoral communities: the studied species consumes 24 g C.m-2 -a-1 from P. oceanica leaf, 4.8 from epiphytes and 13 from epilithic algae. The fish net production and biomass turnover in that zone have been estimated to be 1.2gC.m-2 .a-1 and 1.5 a-1 , respectively. 相似文献
4.
Abstract. The influence of corallivores on coral community structure of eastern Pacific reefs has been considered less important then that of abiotic oceanographic factors. The data that support this assumption, however, are only available for Central American reefs. To assess the role of predation on hermatypic corals in a different regional reef environment, the abundance, spatial distribution and consumption rate of three corallivores: the echinoid Eucidaris thouarsii (Valenciennes), the asteroid Acanthaster planci (Linnaeus) and the teleostean fish Arothron meleagris (Bloch & Schneider), were estimated at Cabo Pulmo reef, Gulf of California, México (23°25' N, 109°25' W). Statistically, the abundances of the species did not change in any sections of the reef (mean values: E. thouarsii , 0.17 indiv. · m−2 ; A. planci , 1.9 indiv. · m−2 ; A. meleagris , 39 indiv. · ha−1 ). The average daily individual consumption rates of coral were calculated at 1.83 g CaCO3 · m−2 for E. thouarsii , 118.4 cm2 for A. planci , and 16.38 g CaCO3 · m−2 for A. meleagris , and were lower than those reported for Central American reefs. Considering the mean estimated carbonate production (7.9 kg CaCO3 · m−2 · a−1 ), corallivores eliminate less than 4% of the coral standing stock of Cabo Pulmo reef. The low corallivore population density and consumption rates, together with high local coral cover, indicate that corallivores are not key factors determining scleractinian abundance in this marginal reef. 相似文献
5.
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
6.
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
7.
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
8.
Description of the Phytoplanktonic Community of the Oligotrophic Waters of the SE Aegean Sea (Mediterranean) 总被引：2，自引：0，他引：2
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
9.
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
10.
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
11.
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
12.
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
13.
The use of taxonomic distinctness indices in assessing patterns of biodiversity in modular organisms 总被引：1，自引：0，他引：1
Stanislao Bevilacqua Simonetta Fraschetti Antonio Terlizzi & Ferdinando Boero 《Marine Ecology》2009,30(2):151-163
Estimating diversity of modular organisms may be problematic due to actual difficulties in discriminating between 'individuals' and quantifying their abundances. Quantitative data, when available, are collected through methods that could preclude the application of classical diversity indices, making comparisons among studies difficult. Taxonomic distinctness indices, such as the 'Average Taxonomic Distinctness' (Δ+ ) and the 'Variation in Taxonomic Distinctness' (Λ+ ) may represent suitable tools in investigating diversity beyond the simple species number. The potential usefulness of such indices has been explored almost exclusively on unitary organisms, neglecting modular ones. In this study, we employed Δ+ and Λ+ to analyse patterns of diversity of epiphytic hydroid assemblages living on Cystoseira seaweeds at a hierarchy of spatial scales, along 800 km of rocky coast (SE Italy). ANOVA on species richness and Λ+ showed no significant difference in sample diversity at the investigated spatial scales. In contrast, there were significant differences at the scale of 10s of km in Δ+ . Analyses based on simulations detected significant variations at all spatial scales in Δ+ . Such findings underline the potential of Δ+ in highlighting relevant spatial scales of variation in patterns of hydroid diversity. Our results also suggest that the interplay between natural environmental variations and the complex ecological traits of modular organisms might affect taxonomic distinctness indices. We stress the need for further investigations focusing on modular organisms before any generalizations on the use of taxonomic relatedness measures in examining marine biodiversity can be made. 相似文献
14.
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
15.
Three recurring regional patterns of extratropical baroclinic development associated with synoptic‐scale collapses of Northern Hemisphere available potential energy (APE) are identified using a 1979–95 time series derived from the National Centers for Environmental Prediction (NCEP) reanalysis. A time series of the intraseasonal signal (from 1.6 to 180 days) of APE is used to discern an average cycle of approximately 3 days in the APE generation rate d A /d t (referred to as APE depletion rate if negative). An APE depletion event is defined as a fall and subsequent rise in the time series of d A /d t associated with this cycle. We define synoptic‐scale APE collapses as APE depletion events with maximum depletion rates (d A /d t min ) and maximum APE falls (Δ A min ) of less than −0.145× 106 J m−2 day−1 and −0.280×106 J m−2 , respectively. All are cold season (15 October–15 April) events. APE collapses were classified based on the evolution of regional synoptic patterns during the 2 days centered at the time of d A /d t min . All are accompanied by deep tropospheric warming. The west Pacific warm surge (Type A) is driven by cyclogenesis over Japan and anticyclogenesis over the west‐central North Pacific. The Bering warm surge (Type B) is associated with an intense southerly flow across the Bering Strait brought on by cyclogenesis near the Kamchatka Peninsula and an intense anticyclone over Alaska. The Atlantic Canada warm surge (Type C) is characterized by an onshore flow of warm air ahead of a continental storm track over eastern North America. 相似文献
16.
Chlorophyll in Copepod Faecal Pellets: Changes in Pellet Numbers and Pigment Content during a Declining Baltic Spring Bloom 总被引：2，自引：0，他引：2
Abstract. Zooplankton stock as well as faecal pellet numbers were monitored over 2 weeks during May in the central Baltic. Considerable changes in concentrations of chlorophyll and its derivates in copepod faecal pellets as well as in surface sediments were found during this period. The maximum concentration of 1.05 ngchl. a faecal pellet-1 , measured on 12 May, decreased by the end of the month to 0.08 ngchl. a faecal pellet-1 . This decrease was positively correlated with the disappearance of intact diatoms inside faeces. A flux of 1.53mgchl. a -m-2 -day-1 via faecal pellets was calculated for the deep water layer (60–80 m) in mid May. This decreased to 0.005mgchl. a m-2 day-1 by the end of May. Chi. a accounted for up to 10 % of total pigments in samples from the top centimetre of the sediment surface. The means of transportation of faecal pellets as well as their function as a food supply to deeper ecosystems are discussed. 相似文献
17.
Abstract. Nitzschia sicula (C astr .) H ust ., a planktonic pennate diatom, dominated the microphytoplankton (104 -5 times 104 cells. 1-1 ) in the central, oligotrophic Southern Adriatic Pit waters (20-50m layer) in May 1990. Nauplii dominated the microzooplankton (3 indiv. 1-1 in the 0-50m layer, 130 μm mean body length) and produced a considerable amount of faecal (mini)pellets (1900. 1-1 at 50m, mean diameter 47μm), which were compactly filled with N. sicula frustules. The subsurface accumulation of diatoms and nauplii was probably the result of both productive activity under specific hydrographic conditions and the convergence in a relatively strong southern Adriatic cyclonic gyre; the advective transport of populations along the shear zone, at the boundary between water masses of different thermo-haline characteristics may also have played a role. The amount of minipellets was high if compared with the data available from other seas. This was probably due to high production of minipellets, their slow sinking rate, and/or an absence of manipulation of the faecal material by zooplankton. 相似文献
18.
19.
Sevim Polat 《Marine Ecology》2002,23(2):115-126
Abstract. The monthly changes in chlorophyll a , phytoplankton abundance and nutrient concentrations at two stations, one at the inshore and the other at the deep waters of the northern part of İskenderun Bay, were investigated between 1994 – 1995. The vertical distribution of nutrients and phytoplankton biomass were also studied at the deep station. The concentrations of NO3 +NO2 -N, PO4 -P and SiO4 -Si of surface water at both stations were 0.31 – 1.63 µg-at · l-1 , 0.08 – 0.60 µg-at · l-1 and 0.50 – 2.7 µg-at · l-1 , respectively. The highest concentrations were measured at the inshore station and clear differences were found between the inshore and deep-water stations. Chlorophyll a concentrations ranged from 0.17 to 2.78 µg · l-1 and the highest value was measured in March. At the inshore station, which was affected by land run-off, phytoplankton abundance reached the highest value (21,308 cells · l-1 ) in October 1995, with a marked dominance of Pseudonitzschia pungens (20,200 cells · l-1 ). The nutrient and chlorophyll a concentrations at the inshore station were higher than those at the deep station. One reason for this is the land-based nutrient input into the coastal area here. In spite of these effects, the bay is not eutrophicated because of circulation events in the northeastern Mediterranean. 相似文献
20.
Abstract. Thirteen sampling cruises were conducted at weekly intervals in the inner part of the Gulf of Naples in the summer of 1983 to investigate the effects of excess nutrient inputs on phytoplankton communities. High surface phytoplankton concentrations (up to 1.15 ×108 cells 1-1 ) were recorded, particularly near Naples harbour and along the eastern coast, two locations that receive most of the area's sewage and industrial discharge. Phytoplankton populations were generally dominated by small species, mainly diatoms, which were associated with small phytoflagcllatcs. Species diversity values were relatively high (H'≤ 3.62) in most samples. Throughout the sampling period a high spatial and temporal variability for phytoplankton abundances and species composition was observed. 相似文献