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1.
Thermohaline Anomalies in the Spring and Early Summer of 2000 in the Gulf of Trieste 总被引：1，自引：0，他引：1
Abstract. In the framework of the Interreg II Project (July 1998 - June 2001), hydro-logical, chemical and biological data were collected in the Gulf of Trieste.
During spring and summer 2000, some particular thermohaline anomalies were observed in the Gulf of Trieste. Especially in May and June the water body showed: a very strong thermohaline stratification, an increase of advective salt water coming from the south and the presence of sharp pycnoclines. In July the temperature was higher than usual in the whole water column. Moreover, in late May and in June, massive mucilaginous aggregates were observed along the water column and at the surface.
In order to highlight these particular thermohaline features the hydrological data of 16 stations were analysed (Fig. 1). Two stations, in particular, were considered: one offshore (St. AA1, average depth 20 m) and one close to the coast (St. C1, average depth 17 m). For these two stations a best-fit analysis, computed over 11 and 7 years, respectively, was performed on temperature, salinity and density excess data.
Moreover, the hydrological features were compared with the rainfall, air temperature, wind speed data (Istituto Sperimentale Talassografico di Trieste - ISTT) and the Isonzo River's flow rate (Direzione Regionale dell'Ambiente - Regione F. V. G.) collected from January 1998 to December 2000. 相似文献
During spring and summer 2000, some particular thermohaline anomalies were observed in the Gulf of Trieste. Especially in May and June the water body showed: a very strong thermohaline stratification, an increase of advective salt water coming from the south and the presence of sharp pycnoclines. In July the temperature was higher than usual in the whole water column. Moreover, in late May and in June, massive mucilaginous aggregates were observed along the water column and at the surface.
In order to highlight these particular thermohaline features the hydrological data of 16 stations were analysed (Fig. 1). Two stations, in particular, were considered: one offshore (St. AA1, average depth 20 m) and one close to the coast (St. C1, average depth 17 m). For these two stations a best-fit analysis, computed over 11 and 7 years, respectively, was performed on temperature, salinity and density excess data.
Moreover, the hydrological features were compared with the rainfall, air temperature, wind speed data (Istituto Sperimentale Talassografico di Trieste - ISTT) and the Isonzo River's flow rate (Direzione Regionale dell'Ambiente - Regione F. V. G.) collected from January 1998 to December 2000. 相似文献
2.
The Influence of Mucous Aggregates on the Microphytobenthic Community in the Northern Adriatic Sea 总被引：2，自引：0，他引：2
Abstract. An extended reappearance of mumus aggregates in the Northern Adriatic Sea in 1991 gave rise to the hypothesis of a possible influence of the mucus, settled on the bottom, on benthic flora and fauna.
This work investigates the variations in the microphytobenthic community in three stations of the Gulf of Trieste (AA1, AA2, AA3) during 1991, when mucous aggregates were present, and during the two following years, when no such aggregates were observed.
Water samples were collected by N iskin bottle in the bottom layer for nutrient analysis, and sediment samples were collected by divers. The diatom species and cell densities were determined under an inverted microscope. All the data were processed with the aim to evaluate community composition and possible relations with the presence of mucous aggregates in 1991.
The results showed a general decrease of benthic diatoms from 1991 to 1993, both in quality and quantity, for all the investigated sites. Statistical analyses on microphytobenthos, hydrological parameters, and nutrient concentrations indicated differences among the considered years. The microphytobenthic community in summer 1991 appeared to be quite different from those of the other years. The density of benthic diatoms was apparently not correlated with nutrient availability in the bottom layer, but was rather influenced by changes in temperature.
The presence of a dense microphytobenthic community in 1991 might be explained by a combination of adequate conditions related to the presence of mucous aggregates, including a more undisturbed substratum caused by the interruption of dredging, decreased grazing pressure due to a declined filtering capacity of epifauna, and nutrient-rich sediment for extra nutrient disposal remineralized at the mucus-sediment interface. The mucilage aggregates therefore apparently stimulated the microphytobenthic community, in contrast to the effects on the benthic macrofauna, which were perturbed by the mucus. 相似文献
This work investigates the variations in the microphytobenthic community in three stations of the Gulf of Trieste (AA1, AA2, AA3) during 1991, when mucous aggregates were present, and during the two following years, when no such aggregates were observed.
Water samples were collected by N iskin bottle in the bottom layer for nutrient analysis, and sediment samples were collected by divers. The diatom species and cell densities were determined under an inverted microscope. All the data were processed with the aim to evaluate community composition and possible relations with the presence of mucous aggregates in 1991.
The results showed a general decrease of benthic diatoms from 1991 to 1993, both in quality and quantity, for all the investigated sites. Statistical analyses on microphytobenthos, hydrological parameters, and nutrient concentrations indicated differences among the considered years. The microphytobenthic community in summer 1991 appeared to be quite different from those of the other years. The density of benthic diatoms was apparently not correlated with nutrient availability in the bottom layer, but was rather influenced by changes in temperature.
The presence of a dense microphytobenthic community in 1991 might be explained by a combination of adequate conditions related to the presence of mucous aggregates, including a more undisturbed substratum caused by the interruption of dredging, decreased grazing pressure due to a declined filtering capacity of epifauna, and nutrient-rich sediment for extra nutrient disposal remineralized at the mucus-sediment interface. The mucilage aggregates therefore apparently stimulated the microphytobenthic community, in contrast to the effects on the benthic macrofauna, which were perturbed by the mucus. 相似文献
3.
Based on a hydrodynamic-ecological model, the temperature, salinity, current, phytoplankton(Chl a),zooplankton, and nutrient(dissolved inorganic nitrogen, DIN, and dissolved inorganic phosphorous, DIP)distributions in the Beibu Gulf were simulated and the nutrient budget of 2015 was quantitatively analyzed. The simulated results show that interface processes and monsoons significantly influence the ecological processes in the gulf. The concentrations of DIN, DIP, phytoplankton and zooplankton are generally higher in the eastern and northern gulf than that in the western and southern gulf. The key regions affected by ecological processes are the Qiongzhou Strait in winter and autumn and the estuaries along the Guangxi coast and the Red River in summer.In most of the studied domains, biochemical processes contribute more to the nutrient budget than do physical processes, and the DIN and DIP increase over the year. Phytoplankton plays an important role in the nutrient budget; phytoplankton photosynthetic uptake is the nutrient sink, phytoplankton dead cellular release is the largest source of DIN, and phytoplankton respiration is the largest source of DIP. The nutrient flux in the connected sections of the Beibu Gulf and open South China Sea(SCS) inflows from the east and outflows to the south. There are 113 709 t of DIN and 5 277 t of DIP imported from the open SCS to the gulf year-around. 相似文献
4.
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
5.
北部湾浮游植物粒径分级叶绿素a和初级生产力的分布特征 总被引：19，自引：4，他引：19
1994年5月23B至6月4日现场观测了北部湾浮游植物细胞丰度、叶绿素a浓度和初级生产力的分布.测区平均叶绿素a浓度为0.94±0.45/d3.平均初级生产力(C)为351±172mg/(m2·d),浮游植物细胞丰度为0.97×104-10050×104个/m3,鉴定浮游植物4门56属176种.地理环境和水文状况的差异使上述参数分布具有明显的区域性特征,近岸区高于湾中部,测区北部高干南部;温跃层以下水层叶绿素a浓度高于上层水,周6观测站平均叶绿素a浓度湾北部(0.47±0.15g/dm3)高于湾南部(0.15±0.02dm3).北部湾水域光合浮游生物以微型和微微型细胞(小于20m)占优势,其对总初级生产力的贡献(占91%)高于对总叶绿素a的贡献(占77%). 相似文献
6.
7.
Annual Variation of Benthic Nutrient Fluxes in Shallow Coastal Waters (Gulf of Trieste, Northern Adriatic Sea) 总被引：5，自引：0，他引：5
Abstract. Benthic fluxes of dissolved N. Si and P nutrients, alkalinity, dissolved inorganic C (DIC), and O2 from sediments in the Gulf of Trieste (northern Adriatic, Italy) were measured monthly for 16 months, using laboratory incubated flux chambers at in siru temperatures in the dark. The annual average fluxes were: 02 = -19.3 ± 8.2, DIC = 13.7 ± 9.6, NO3 = -0.04 ± 0.16, NH4 = 0.3 ± 0.4. PO4= 4.001 ± 0.01, Si = 0.9 ± 0.1 mmol m-2 d-1, with strong temporal fluctuations. The highest effluxes of all nutrients and DIC were observed in the summer. Small effluxes of DIC and NH4 and influxes of Si and PO4 were observed in late winter. Only NH4 (ca. 50%) and Si (ca. 70%) fluxes were significantly correlated with temperature. This correlation suggests that the rate of downward input and the quality of sedimented organic matter (autochthonous and allochthonous) were superimposed on the temperature fluctuations. High DIC, NH4 and Si effluxes observed in May 1993 during low temperature were due to the degradation of sedimentary organic matter produced by an early spring bloom of benthic microalgae which occurred about 6 weeks earlies while the autumn phytoplankton bloom was simultaneously reflected in enhanced benthic fluxes due to higher temperature. The role of benthic biological advection in this transport across the sediment-water interface, evaluated by comparison between measured benthic and calculated diffusive fluxes from nutrient pore water concentrations, was of minor importance. This is probably due to low infaunal activity throughout the year it was localized mostly in the narrow surficial layer. The annual average diffusive fluxes of NH4 and PO4 were higher than those measured, probably due to the presence of nitrificationdenitrifi-cation processes and redox-dependent chemical reactions at the oxic sediment-water interface, respectively. Only during bottom-water hypoxia in September 1993 did strong PO4 effluxes prevail. Calculations based on the Redfield stoichiometry of oxic decomposition of organic N to NH4 and NO3, and differences between diffusive and measured NH4 fluxes showed that denitrifkation averaged 0.8 mmol m-2 d-1. Significant correlations between NH4 and PO4 DIC and Si, and NH4 and Si fluxes suggested their parallel regeneration and utilization at the sediment-water interface. The nutrient fluxes observed were not significantly linked to O2 consumption, suggesting also that anaerobic oxidation processes were important at the sediment-water interface in the gulf. The N, P and Si nutriqnts released from sediment pore waters are probably utilized in benthic microalgal and bottorn-hater primary production. This indicates that pelagic and benthic communities in the central part of the Gulf of Trieste function relatively independently of each other. 相似文献
8.
During June 1997 cruise by R/V Science No.l, observations on temporal and spatialvariations of the size-fractionated phytoplankton standing stock and primary production were carried out in the Bohai Sea. The size-fractionated chlorophyll a (Chl a) and primary production, photosynthet-ically available radiation (PAR), as well as the related physico-oceanographic and zooplanktonic parameters were measured at five time-series observation stations representing sub-areas of the sea. Results obtained show that there were the marked features of spatial zonation of Chl a and primary production in the Bohai Sea. The values in the Laizhou Bay, the Liaodong Gulf and the Bohai Gulf were high and showed close relation with tidal fluctuations, i.e. high Chl a concentration occurred during high tide in the Laizhou Bay, and during low tide in the Liaodong Gulf and the Bohai Gulf. In the strait and the central region of the Bohai Sea, the values were relatively low and no relationship with tidal fluctuation could be foun 相似文献
9.
A. A. Maximov T. R. Eremina E. K. Lange L. F. Litvinchuk O. B. Maximova 《Oceanology》2014,54(1):46-53
The changes in the concentrations of the mineral nitrogen (nitrates and nitrites) and phosphorus and in the state of the planktic communities in the eastern Gulf of Finland following a large-scale invasion of the polychaete Marenzelleria arctia were analyzed. The bioirrigation and bioturbation of the bottom deposits by polychaetes resulted in a dramatic increase in the nitrogen/phosphorus ratio in the waters of the gulf, thus leading to cascade changes in the plankton. As a result of the decrease in the abundance of colonial nitrogen-fixing cyanobacteria, which cause “blooming” in surface waters, the total biomass of the phytoplankton and chlorophyll a concentration decreased. Because of the disappearance of large colonies of cyanobacteria and the surge of small algae, the food supply for the zooplankton improved and its biomass increased. According to our calculations, the amount of phosphorus deposited in the bottom sediments as a result of the polychaete activity markedly exceeded the external phosphorus load on the Gulf of Finland from the Russian coast. We conclude that the invasion of Marenzelleria arctia resulted in the cardinal reconstruction of the entire ecosystem of the eastern Gulf of Finland. 相似文献
10.
Distribution characteristics of size-fractionated chlorophyll a and primary productivity in Beibu Gulf 总被引：2，自引：1，他引：1
The distribution of the abundance of phytoplankton, chlorophyll a (Chl.a) concentration and primary productivity in the Beibu Gulf were observed from May 23 to June 4, 1994.The results show that there were marked featares of spatial zonation in the survey area due to the differences between the geographic environment and the hydrological conditions.Chlorophyll a and primary productivity were higher in the inshore than in the middle area and higher in the north than in the south of the Beibu Gulf.The average concentration of Chl.a, primary productivity and the abundance of phytoplankton were 0.94±0.45 μg/dm3, 351±172 mg/(m2·d) (C) and 0.97×104-10.050×104 ind./m3 in the area, respectively.There were 176 species belonging to 4 phyla and 56 genera based on microscope identification.The results of the size-fractionation show that the contribution of nanoplankton and picoplankton was 77% to total Chl.a and 91% to total primary productivity, which proved their importance to phytoplankton communities in the Beibu Gulf. 相似文献
11.
Remote sensing of chlorophyll concentration is potentially affected by the presence of inorganic matter in the water column. Seasonal variability of total suspended particulate matter (SPM) concentration and its partition into organic and inorganic fractions was thus measured in the estuary and Gulf of St. Lawrence during five cruises. These measures were made in the surface layer down to the depth of the 0.1% light level. Results indicate that vertical variability was small for the entire study area. Data analysis lead to the definition of two main regions having different SPM characteristics: 1) the estuary zone characterized by a strong spatial variability, intermediate SPM concentrations and a clear spring phytoplankton bloom that is combined to an increased inorganic matter load; 2) the gulf region characterized by a relatively low SPM concentration and phytoplankton blooms in the spring and fall periods. Combined with in situ measurements of remote sensing reflectances, the database was used to validate existing inorganic matter retrieval algorithms and develop a new one better adapted to the low concentrations encountered in the St. Lawrence estuary and Gulf. 相似文献
12.
13.
The Bonnet Carré Spillway, located 28 miles northwest of New Orleans, was constructed in the early 1930s as part of an integrated
flood-control system for the lower Mississippi River system. From 11 April to 8 May 2008, Mississippi River water was diverted
through the spillway into the 629-square-mile Lake Pontchartrain, which is hydraulically connected to the Gulf of Mexico.
On 8 April, prior to the opening of the spillway, water-quality instruments were deployed and recorded hourly measurements
of water temperature, dissolved oxygen, specific conductance, pH, and nitrate. Discrete water-quality and phytoplankton (algae)
samples were collected in Lake Pontchartrain from 8 April to 3 October 2008 to assess the water-quality nutrient enrichment
effects of the diversion on the lake. The maximum influence of river water in the southern portion of the lake was captured
with continuous (hourly) monitoring of nitrate concentrations, and field measurements such as of specific conductance during
the critical period in late April to early May. By late May, the deployed instruments had recorded the arrival, peak, and
decline of selected constituents associated with the freshwater influx from the Mississippi River/Bonnet Carré Spillway diversion.
The continuous monitoring data showed the short-term interactions of high-nitrate, low-specific conductance river water and
low-nitrate, high-specific conductance lake water. The phytoplankton community composition, as an indicator of water quality,
illustrated an extended response from the river water evident even after the continuous and discrete samples indicated that
the lake had returned to pre-diversion conditions. The initial phytoplankton community response to nutrient increases was
related to accumulations of diatoms. During periods of low nutrient concentrations, accumulations of blue-greens occurred
by July and August. As blue-green algae cell densities and biovolumes increased in the summer, so did the species richness
of blue-green algae, particularly the harmful algae bloom taxa. Cell densities and biovolume of the phytoplankton lake indicator
taxa Skeletonema costatum, Anabaena sp., and Cylindrospermopsis raciborskii were highest and dominated the diatom and blue-green algae communities during the period of most river water influence on
the lake and immediately following the freshwater inflows. The dominance and recession of these indictor taxa reflect the
dramatic changes that occurred in the phytoplankton community in response to an increase in nutrient-rich freshwater from
the diversion into the lake, and not normal seasonal phytoplankton compositional differences. Water-quality data indicated
a gradual reversion to pre-diversion lake conditions by June to July, but shifts in the phytoplankton composition were still
evident through August 2008. Observations from this study were similar to results from previous studies of Mississippi River/Bonnet
Carré Spillway diversion opening in 1997. 相似文献
14.
Megan Young 《新西兰海洋与淡水研究杂志》2013,47(3):167-175
The potential threat of plastic pollution to seabirds within the Hauraki Gulf was assessed by determining its abundance and distribution at two different spatial scales and assessing the community of resident seabirds during July to September 2008. Samples of floating plastics within the gulf were taken during 66 trawls from the surface of the water in three regions within the inner gulf and Waitamata harbour. Within each of these regions, samples were taken in and outside of visually identified natural slick lines that are surface manifestations of small-scale convergence zones. During each trawl, the identity and abundance of seabirds were assessed. Plastic debris was recorded in all three regions sampled with the greatest abundance being recorded in the harbour. Plastics and debris were also significantly more concentrated within natural slick lines. Both user and industrial plastics were identified and consisted of colours and lengths likely to be mistaken as food items for small to medium seabirds. Surface or near-surface feeding seabirds in the gulf most likely mistakenly to consume plastics were fluttering shearwaters, Cape pigeons and Buller's shearwaters. However, these birds were most abundant in the area of the gulf where abundance of plastic pollution was lowest. The Hauraki Gulf is considered significantly less polluted by plastic debris than other severely polluted areas cited in literature. 相似文献
15.
Phytoplankton of the western Arctic in the spring and summer of 2002: Structure and seasonal changes
《Deep Sea Research Part II: Topical Studies in Oceanography》2009,56(17):1223-1236
We analyzed the taxonomic structure and spatial variability of phytoplankton abundance and biomass in the Chukchi and Beaufort Seas during spring and summer seasons of the SBI program. Phytoplankton samples were collected during two surveys from May 10 to June 13 and from July 19 to August 21 of 2002. In May and June, ice cover exceeded 80% over most of the study area and there was no vertical stratification, indicating that the successional state of the phytoplankton corresponded to the end of the winter biological season. The phytoplankton abundance ranged from a few tens to a few thousands of cells per liter, while biomass varied from 0.1 to 3.0 mg C m−3. Small areas of high phytoplankton abundance (0.13–1.3×106 cells L−1) and biomass (22–536 mg C m−3), dominated by early spring diatoms Pauliella taeniata and Fragilariopsis oceanica in the surface waters, which indicated the beginning of the spring bloom, were observed only in the southeastern part of the Chukchi shelf and off Point Barrow. In July and August summer period, more than a half of the study area had <50% ice cover and the water column was stratified by temperature and salinity. Over the Chukchi shelf and continental slope of the Beaufort Sea, the phytoplankton abundance and biomass were an order of magnitude higher in July–August than in May–June. The taxonomic diversity of algae also increased due to the appearance of late-spring and summer diatoms, dinoflagellates, and coccolithophorids (Emiliania huxleyi). Interestingly, the seasonal differences between phytoplankton abundance and taxonomic composition in the spring and summer periods varied the least over the Chukchi Sea slope and in the deep-water area of the Arctic Ocean. High algae concentrations in summer were located in the lower layers of the euphotic zone, suggesting that the spring bloom on both the Chukchi shelf and in the western part of the Beaufort Sea occurred in late June/early July. In the spring and summer, the microalgal community was characterized by a high abundance of 4–10 μm flagellates, which exceeded the abundance of all other taxonomic groups. In both seasons studied, phytoplankton reached its maximum abundance within restricted areas in the southern part of the Chukchi Sea southwest of Point Hope, in the northern part of the Chukchi shelf between the 50- and 100-m isobaths, on the shelf northwest of Point Barrow, and over the continental slope in the Beaufort Sea. The pronounced spatial difference in the seasonal state was a characteristic feature of the phytoplankton community in the western Arctic. 相似文献
16.
Ana I. Dittel C.E. Epifanio Juan Bautista Chavarria 《Estuarine, Coastal and Shelf Science》1985,20(5):593-602
Tropical blue crabs Callinectes arcuatus were collected by trawling in the Gulf of Nicoya on the Pacific coast of Costa Rica, Central America. The gulf population was generally dominated by females. Adult females were common in the upper, more estuarine regions of the gulf during rainy season, but appeared to migrate to the lower gulf during dry season for spawning. Biomass varied with seasonal changes in abundance, but was generally similar to biomass of C. sapidus in Chesapeake Bay. Analysis of size frequency indicated that the population is numerically dominated by adults during January and February and that juveniles are common during the remainder of the year. Extrapolation of available data suggests that female crabs reach maturity in approximately one year after hatching. 相似文献
17.
Z.-P. Mei L. Legendre J.-. Tremblay L.A. Miller Y. Gratton C. Lovejoy P.L. Yager M. Gosselin 《Deep Sea Research Part I: Oceanographic Research Papers》2005,52(12):2301-2314
The carbon to nitrogen (C:N) stoichiometry of phytoplankton production varied significantly during the spring–summer bloom in the North Water Polynya (NOW), from April through July 1998. The molar ratio of particulate organic carbon (POC) to nitrogen (PON) production by phytoplankton (ΔPOC:ΔPON) increased from 5.8 during April through early June to 8.9 in late June and July. The molar dissolved inorganic carbon (DIC) to nitrate+nitrite (NO3) drawdown ratio (ΔDIC: ΔNO3) increased from 6.7 in April and May, to 11.9 in June (no estimate for July because of ice melting). The discrepancy between ΔPOC:ΔPON and ΔDIC:ΔNO3 was likely due to dissolved organic carbon (DOC) production. Increased ΔPOC:ΔPON of phytoplankton and surface water ΔDIC:ΔNO3 throughout the phytoplankton blooms resulted from changes in physical properties of the upper water column, such as reduced thickness of the surface mixed layer that exposed phytoplankton to increased photosynthetically available radiation (PAR), accompanied by NO3 depletion. This is expected to have significant effects on the cycling of carbon (C) and nitrogen (N) in pelagic ecosystems, as the increased C:N ratio of organic matter decreases its quality as substrate for grazers and microbial communities. Based on ΔPOC:ΔPON, the ratio of POC to chlorophyll a (Chl) production (ΔPOC:ΔChl) and the relationship between Chl yields and NO3 depletion, we estimate that 71±17% and 46±20% of the depleted NO3 went to PON production in the euphotic zone over the polynya from April to early June, and late June to July, respectively. The remaining NO3 was likely channelled to dissolved organic nitrogen (DON) and heterotrophic bacteria, which were not returned to the dissolved inorganic nitrogen (DIN) pool through recycling during the course of the study. Hence, the autotrophic production of organic N and its recycling by the microbial food web were not coupled temporally. 相似文献
18.
Abstract. The abundance and taxonomic diversity of phytoplankton have been studied in relation to certain environmental factors in the South Euboikos Gulf, a restricted tidal embayment on the eastern coast of Greece. The northern part of the gulf with higher tidal current, influenced by sewage and industrial effluents, showed high concentrations of nutrients, a greater total density of phytoplankton, relatively high chlorophyll a content, and a lower taxonomic diversity when compared with the southern part. The phytoplankton cycle was largely due to changes in diatom concentration. A slight variation in the occurrence of species and dominance could be observed along the salinity gradients. 相似文献
19.
Temporal variability of Centropages typicus in the Mediterranean Sea over seasonal-to-decadal scales
《Progress in Oceanography》2007,72(2-3):214-232
Centropages typicus is one of the most common, abundant and best studied calanoid copepods in neritic waters of the Mediterranean Sea, which means it can provide useful information about the long-term dynamics of the Mediterranean epipelagic ecosystem. This paper presents the first comparative overview of the seasonal and long-term variability of C. typicus in different Mediterranean regions. This review is based on quantitative information from the published literature and novel data from five ongoing zooplankton time-series carried out in the Mallorca Island (Balearic Sea), the Bay of Villefranche (Ligurian Sea), the Gulf of Naples (Tyrrhenian Sea), the Gulf of Trieste (North Adriatic Sea), and the Saronikos Gulf (Aegean Sea). In most Mediterranean regions, C. typicus has a perennial occurrence, with peaks of abundance that reflect the succession of different generations. Throughout the Mediterranean, the annual cycle of C. typicus is characterized by minima in winter and major peaks in April–June, which is earlier than those observed in European Atlantic waters, where the peaks are more frequently recorded in summer and fall. In the regions investigated, the annual cycle shows remarkable similarities in terms of timing, but notable differences in the peak height; populations are far more abundant in coastal north-western regions and less abundant in the eastern basin. In the long-term, changes in C. typicus phenology observed in the Bay of Villefranche and in the Gulf of Naples are related to the North Atlantic Oscillation (NAO) index. In these two regions, the species responds to climate forcing similarly in terms of average seasonal patterns (bi-modal patterns in years of positive NAO, unimodal patterns in years of negative NAO) but oppositely in terms of quantity, indicating different influence of the NAO on the two regions. At decadal scales, C. typicus populations show high interannual variability with marked geographical differences. In some areas, the patterns are clearly characterized by alternate phases of higher and lower annual abundances, at higher frequency (mainly 1–2 years) in the Gulf of Naples, and lower frequency in the Saronikos Gulf (mainly 4–5 years) and in the Gulf of Trieste (mainly 5–6 years). Synchronous phases of increasing or decreasing abundance are discernable only for a few sites and short periods, for example from 1998 to 2000 in the Gulf of Naples, Gulf of Trieste and Saronikos Gulf. The regional differences observed in the long-term patterns of C. typicus populations suggest that the temporal dynamics of this species are significantly more affected by local conditions than by any possible common driving force acting at basin scale through teleconnections. 相似文献
20.
Abstract. The diet of the copepod Anomalocera ornata was examined by comparing contents of fecal pellets produced on natural diets with assemblages of available phytoplankton. Samples were collected in continental shelf and slope waters of the northern Gulf of Mexico. A wide size and taxonomic array of phytoplankters was ingested, and remains of phytoplankton taxa in fecal pellets reflected the composition of phytoplankton assemblages in the water. Absence of crustacean remains in fecal pellets suggests that A. ornata feeds primarily as an opportunistic grazer. 相似文献