Monthly changes in the abundance and biomass of zooplankton and water quality parameters in Kukkarahalli Lake of Mysore, India

Zooplankton abundance and distribution are of ecological importance, as they are very sensitive to change, therefore zooplankton make ideal indicators of aquatic ecosystem. This study carried out on the abundance of rotifer, cladoceran, cyclopoid-copepod and ostracod zooplankton groups and biomass of total zooplankton were studied every month for one year. It is interesting and noteworthy to note that Calanoid and Harpacticoid zooplankton groups and free carbon dioxide were completely absent in all the four sampling sites throughout the study year. About 53% of the variation in the abundance of Cladoceran, 55% of variation in the Cyclopoid-copepod, 39% of variation in the ostracod and 53% of variation in the abundance of total zooplankton were mainly due to pH. Interestingly, negative relationship was found between the total zooplankton and concentration of phosphate as in this lake 67% decrease in wet biomass was mainly because of phosphate, where as 47% of dry biomass of total zooplankton was positively correlated with conductivity.     

Contribution à l'étude du zooplancton des eaux libanaises

A study of zooplankton of the Lebanese coastal waters has been carried out for the first time. Thirty three net samples were taken from the surface and 10 m depth at 8 different stations, using 2 planktonic nets of different sizes. One hundred and ten species and genera of zooplankton were identified and the relative abundance of species was noted. Copepods constitute the major fraction of zooplankton (50% of the total species and about 75% of the total biomass). Most zooplanktonic groups are represented.     

Distribution,biomass and ecology of meso-zooplankton in the Northern Adriatic Sea

Two oceanographic cruises were carried out in the northern Adriatic Sea, from June, 1996 to February, 1997. Samples were collected using a BIONESS electronic multinet (204 samples on 54 stations) along inshore-offshore sections. Zooplankton abundance and biomass were estimated in relation to the variability of temperature, salinity and fluorescence. Spatial and vertical distribution patterns of the most important zooplankton groups were studied. During June, in the northern area, abundance and biomass of 2787 - 1735 r ind m and 29.3 - 26.7 r mg r m, respectively, were reported. The zooplankton community was constituted essentially by copepods and cladocerans. In the southern area, instead, an abundance of 4698 - 5978 r ind r m and a dry weight of 25.4 - 15.3 r mg r m were observed, with a reverse dominance ratio between these groups. In February, in the northern area the zooplankton community (1380 - 595 r ind r m and 19.6 - 9.9 r mg r m) was mainly constituted by copepods, larvae of invertebrates, appendicularians and cladocerans; in the southern area zooplankton average abundance was 969 - 493 r ind r m and 9.9 - 3.2 r mg r m being copepods, cladocerans, appendicularians and larvae of invertebrates. The zooplankton spatial distribution, in this period, did not show the classic inshore-offshore gradient. Spatial distribution and biomass values of zooplankton, in the northern Adriatic Sea, were strongly influenced by hydrological characteristics, allowed up to formulate a preliminary model about distribution, along the water column, of the different associations of species assemblages with regard to different water masses in the neritic system.     

Excretion of ammonia by zooplankton and its potential contribution to nitrogen requirements for primary production in the Catalan Sea (NW Mediterranean)

Excretion of ammonia by mesozooplankton (>200 m zooplankton) and its potential contribution to the nitrogen requirement for phytoplankton growth has been estimated for different hydrographical situations along a transect across the Catalan Sea (Northwestern Mediterranean). The nitrogen excreted as ammonia was estimated from mesozooplankton biomass and specific excretion rates. Nitrogen requirements of phytoplankton were estimated by means of carbon fixation rates and C:N ratios of <200 m particulate organic matter. Minimum C:N ratios and maximum primary production, zooplankton biomass, phytoplankton nitrogen requirements, and nitrogen excretion of zooplankton occurred near the Catalan density front. On average, the nitrogen regenerated by the mesozooplankton accounted for 43% of the nitrogen requirements of the phytoplankton. The specific excretion rates of ammonia and the percentage of phytoplanktonnitrogen requirements supplied by excreted nitrogen were higher at coastal stations. In some coastal and frontal stations, the ammonia excreted exceeded the phytoplanktonnitrogen demand. Bacteria competing for nutrient supply and the possible uncoupling between rate processes and standing stocks of phyto- and zooplankton could explain the apparent excess of regenerated ammonia.     

Day-night differences in the emergence of demersal zooplankton from a sand substrate in a kelp forest

Day-night differences in abundance and biomass of demersal zooplankton in the water column were determined by trapping these animals as they emerged from the sand substrate in a kelp forest (Macrocystis pyrifera) ecosystem off Santa Catalina Island, California, USA. The day and night sampling periods of the 24 June 1979 new moon each lasted 12 h. Abundance and biomass of total demersal zooplankton were significantly higher in night samples. A mean of 2,425±1,168 demersal zooplankton m^-2 24 h^-1 migrated over a diel cycle; 97% of these animals were crustaceans. The mean biomass of demersal zooplankton was 94.2±27.6 mg ash-free dry wt m^-2 24 h^-1. No significant differences were found in either the abundance or biomass of demersal zooplanktion collected in low and high traps, suggesting that most animals collected 25 cm off the bottom can sustain swimming to at least 75 cm and that both traps give comparable estimates of the amount of demersal zooplankton available to planktivorous predators.     

Influence des conditions hivernales sur les productions phyto-et zooplanctoniques en Méditerranée Nord-Occidentale. V. Biomasse et production zooplanctonique — relations phyto-zooplancton

The cruise “Mediprod I” of the R.V. “Jean Charcot” covered an area of the Mediterranean Sea situated North of the 40th parallel and West of Corsica; during two 15-day legs, the first when Winter conditions ended, in March, the second in Spring conditions, in April, a 48-station network was surveyed as to primary and secondary production, as well as hydrological conditions. The first survey revealed a higher concentration of zooplankton in hydrologically stable areas, especially in the South-East, although zooplankton values were rather low throughout the whole area surveyed. The total zooplankton per unit surface was lower at the edges of the surveyed area, where phytoplankton was scarce. An increase in zoo-plankton biomass was observed between the two surveys, mostly in the central areas and near the surface. An important difference between both legs is in the proportion of organisms of different sizes collected by the Clarke-Bumpus sampler: the-200 μ:+200 μ organisms ratio, which is around 1 during the first leg, is much lower during the second leg. Two methods were used in estimating the biomass: the +200 μ fraction of a Clarke-Bumpus sample (Cl-B towed with a 50-μ net fitted on the sampler) was collected by sieving the sample through a 200-μ mesh nylon; standard vertical WP 2 hauls were performed (200 μ mesh). Both roughly show the same zooplankton (weight per unit surface) distribution pattern. However, higher estimations of the total biomass of the volume investigated were sometimes provided by the Clarke-Bumpus method during the first leg, probably due to the distribution of the animals according to their size-classes. A graph of chlorophyll versus zooplankton for surface waters suggests that zooplankton has a limiting effect on the development of phytoplankton in April only. Apparent growth rates of cooplankton are less than those for populations in the laboratory or enclosed environments. Values of the mean secondary production vary from 18 mg C.m^-2.day^-1 for the first leg, to 230 mg C.m^-2.day^-1 for the second leg. Estimations of net efficiency for energetic transfer between phyto- and zooplankton lie between 7 and 26%. As far as our hypotheses as regards physiological coefficients are valid, we can assume that the effect of grazing relative to primary production is greater in the border areas than in the central area, thus increasing the contrast between both areas with time. Phosphorus excretion rate by zooplankton seems to be less than that measured in the Atlantic Ocean. We suggest that in Spring zooplankton excretion is not the main phosphorus recycling process. Primary productivity measurements, apparent growth coefficients, and estimated grazing rate have been used to calculate the expected mean biomass per unit area during the second leg. A 7% loss of phyto- and zooplankton from the upper 100-m layer must be assumed to explain the observed biomass variation. Vertical mixing and sinking of surface water on an isopycnal slope are responsible for such loss, which can also affect, to an undetermined degree, the phosphorus stock introduced into the surface layer by the Mediterranean deep-water formation mechanism. We suggest that nearly half the total loss of phytoplankton from March to April is attributable to animal grazing.     

Zooplankton abundance and grazing at Davies Reef,Great Barrier Reef,Australia

Zooplankton abundance and grazing on autotrophic and heterotrophic particulate matter were measured along a transect across Davis Reef (18°5S; 147°39E) and in the back-reef lagoon over tidal and diel cycles during austral winter (August 1984). Zooplankton entering the reef from the surrounding shelf waters decreased in abundance over the reef flat, presumably because of predation. Within the reef lagoon, maximum daytime densities of pelagic copepods occurred during high water, suggesting an external input. At night, water-column zooplankton biomass increased by a factor of 2 to 3 due to the emergence of demersal reef zooplankton. Zooplankton grazing rates on heterotrophic particulate matter (bacteria + detritus and Protozoa) compared to phytoplankton were higher on the reef flat than on the fore-reef or lagoon. Within the lagoon, zooplankton grazing rates on heterotrophic material were maximum during high water, coincident with maximum tidal concentrations of particulate organic carbon. The combined demersal and pelagic zooplankton community were often able to crop 30% of the daily primary production by >2µm phytoplankton. However, >50% of phytoplankton biomass was in cells <2µm, presumably unavailable to these zooplankton. Our particulate production and ingestion measurements, together with zooplankton carbon demand extrapolated from respiration estimates, suggest that the zooplankton community of Davies Reef derives much of its nutrition from detritus.Joint contribution from the University of Maryland, Center for Environmental and Estuarine Studies (No. 2015), and the Microbial Ecology on a Coral Reef Workshop (MECOR No. 19)     

A comparative study of zooplankton dynamics in two subtropical temporarily open/closed estuaries, South Africa

This study aims at comparing the zooplankton abundance/biomass of two South African estuaries affected to a different degree by sewage pollution. In particular the hypothesis that microzooplankton may increase relative to mesozooplankton, as eutrophication increases, is tested for the first time in African estuaries. The survey was carried out during a whole-year cycle, including both open and closed phases. Results show that zooplankton abundance and biomass are higher in the Mdloti than in the Mhlanga, during both the closed (U=1, P<0.001, U=16, P<0.001) and the open phase (U=101, P<0.05, U=88, P<0.01). There were no significant differences in abundance/biomass between the different reaches of each estuary, during either their open or closed phase (1-way ANOVA, P>0.05). The different levels of dominance of the calanoid copepod Pseudodiaptomus hessei, which accounted for 53–64 and 86–97% of the total abundance in the Mdloti and the Mhlanga, respectively, suggests a shift in the zooplankton community structure. There was a lower microzooplankton abundance/biomass contribution to the total zooplankton in the Mhlanga (59.6–15.8%), compared to the Mdloti (99.1–96.5%). The highest microzooplankton contribution in the Mdloti was observed during the closed phase, while in the Mhlanga this occurred during the open phase. This suggests that eutrophication in the Mhlanga may impact negatively on the microzooplankton community. On the other hand the less affected Mdloti exhibits an opposite trend with an increased microzooplankton component.     

椒江口春、秋季浮游动物分布特征及与主要环境因子的关系

2009年5月和10月对椒江口(121.35°E～121.85°E,28.50°N～28.80°N)浮游动物进行调查,分析其群落结构、生物量和丰度的时空分布特征及与主要环境因子的关系.结果表明,该海域浮游动物有明显的季节变化,春季鉴定到14大类50种,卡玛拉水母(Malagazzia carolinae)为绝对优势种,秋季鉴定到14大类73种,优势种分别为百陶箭虫(Sagitta bedoti)、双生水母(Diphyes chamissonis)、亚强真哲水蚤(Eucalanus subcrassus)、微刺哲水蚤(Canthocalanus pauper)、中华胸刺水蚤(Centropages sinensis)和肥胖箭虫(Sagitta enflata);多样性指数为秋季(2.59)高于春季(1.82),生物量和丰度为春季(972.66 mg/m3和1 743.54 ind/m3)远高于秋季(65.30 mg/m3和31.94 ind/m3).总生物量和丰度的空间分布由优势种决定,春季高值区出现在咸淡水交汇的出海口处;秋季有沿河口向外递增的趋势.典范对应分析(CCA)表明,营养盐、盐度和溶解氧为影响春秋季椒江口浮游动物分布的环境因子;浮游动物群落存在明显的季节和空间异质性;各物种适宜的生态环境不同.与类似河口的现状相比,椒江口的浮游动物种类丰富,可能与影响该河口的水团多样有关;与历史资料相比,椒江口4、10月份浮游动物的生物量、丰度及优势类群保持相对稳定.图9表6参44     

Temporal variability of deep-sea zooplankton in the Arabian Sea

Mesozooplankton samples from two stations in the Arabian Sea (WAST, 4,050 m, 16°15′N, 60°20′E; CAST, 3,950 m, 14°30′N, 64°30′E) were collected from the surface down to 20 m above bottom during three monsoon periods: the autumn intermonsoon in October 1995, the spring intermonsoon in April 1997, and the NE monsoon in February 1998. The main goal of this study is to enhance our knowledge on the effect of spatial and temporal differences in primary production and particle flux rates on the abundance and distribution of mesozooplankton, with special attention to the deep sea. Literature data indicate episodically high rates of primary production and particle flux in the region during the SW monsoon and the autumn intermonsoon. Set in this context, the zooplankton showed an in-phase coupling in biomass and abundance with the primary production in the surface 150 m. In the mesopelagic realm (150–1,050 m), the seasonal coupling was less clear. In the bathypelagic zone, below 1,050 m, there was no evidence of in-phase coupling, though temporal differences in the distribution of zooplankton abundance and biomass with depth between seasons could be shown by an analysis of covariance and an a posteriori test. The results suggest that the bathypelagic community responds to increased particle flux rates, but with longer time gaps than in the epipelagic zone. This is probably due to longer development and response times of zooplankton in the cold, deep-water environment, independent of possible lateral advection processes.     

Zooplankton: pre-southwest and northeast monsoons of 1993 to 1994, from the North Arabian Sea

Zooplankton samples from the North Arabian Sea Environment and Ecosystem Research (NASEER) cruises were analyzed to determine the basic taxonomic composition, biomass (standing stock) and the total and copepod numeric abundance; these characteristics are discussed with reference to the different monsoon periods. Cruises carried out during March 1993 and May 1994, categorized as pre-southwest monsoon periods, and a cruise in December 1994, categorized as a northeast monsoon period, are discussed in detail. The biomass of January 1992 versus August 1992 and August 1992 versus March 1993 differed significantly (F = 6.44, P≤ 0.05). Ranges of highest and lowest biomass from each cruise are also given. Distinct “high” and “low” production areas of statistically significant difference (F = 12.67, P≤ 0.05) were observed. The “high” and “low” production areas were mobile and followed the surface wind circulation patterns (wind reversal pattern) during the northeast and southwest monsoon periods. Overall zooplankton showed a patchy distribution. The overall zooplankton abundance and total copepod counts differed significantly between the Cruises 3 versus 4 and 4 versus 5 (F = 15.67, P≤ 0.05 and F = 34.39, P≤ 0.05, respectively). There was no significant difference (P≥ 0.05) in biomass, between eutrophic and oligotrophic stations, suggesting no difference between near shore and offshore waters. Thirty-eight taxonomic groups were identified from the samples, with copepods being the most dominant group, followed by chaetognaths and siphonophores. Copepods constitute an average of 52.50 to 74.93% of the total zooplankton count and reach maxima of 92.14% of the total zooplankton count at the outset of the southwest monsoon (March 1993) and 91.39% at the outset of the active northeast monsoon (December 1994). Received: 27 February 1998 / Accepted: 8 October 1999     

Planktonic ciliates in Southampton Water: abundance,biomass, production,and role in pelagic carbon flow

The abundance and biomass of marine planktonic ciliates were determined at monthly intervals at two stations in Southampton Water between June 1986 and June 1987. The two stations, an outer one at Calshot and an inner one at N. W. Netley, were subject to differing marine and terrestrial influences. The potential ciliate production at cach station on each visit was estimated from these data. Enumeration of ciliates and measurements of biovolume were performed on Lugol's iodinepreserved samples and potential production was calculated using a predictive relationship based on temperature and cell volume. Heterotrophic ciliate abundance and biomass were greatest at both stations during spring and summer months, with respective maxima of 16x10³ organisms 1^-1 and 219 g Cl^-1 recorded at N. W. Netley. Estimates of the potential production of the ciliate community ranged from <1 to 18 g Cl^-1 d^-1 at Calshot and <1 to 141 g Cl^-1 at N. W. Netley, with annual values of 2 and 9 mg Cl^-1 yr^-1, respectively. Abundances, biomass and potential production estimates were generally greater at N. W. Netley than at Calshot. Carbon flow through the ciliate community was assessed using annual production values from both this study and the literature. The annual ciliate carbon requirement was equivalent to 9 and 11% of annual primary production at Calshot and N. W. Netley, and potential annual ciliate production was equivalent to 34% and >100% of the energy requirements of metazoan zooplankton at these locations, although comprising only 8 and 10% of their available food.     

Local changes in the composition and community structure of suprabenthic peracarid crustaceans on the bathyal Mediterranean: influence of environmental factors

Deep-water assemblages of suprabenthic peracarids were analyzed in the SW Balearic Islands (Algerian Basin, southwestern Mediterranean) between 249 and 1,622 m depth; the patterns of species composition, possible zonation, and trophic structure found in this area were compared with those exhibited by peracarids in the mainland side of the Catalan Sea slope (northwestern Mediterranean). One hundred and four peracarid species (plus one leptostracan) were identified on the Balearic Islands slope, amphipods being the most diversified taxon (45 species). On the Balearic slope, two distinct depth assemblages were distinguished: one at the upper slope (US), between 249 and 402 m depth and the second at the deep slope, between 543 and 1,620 m depth. A remarkable species substitution occurred at depths between 402 and 638 m. In the Catalan Sea, in addition to the US assemblage occupying depths between 208 and 408 m, a second boundary of faunal change was found around 1,250 m. Suprabenthos biomass increased from 242 to approximately 500 m. Suprabenthos attained the highest biomass values (100 g wet weight/10,000 m²) at intermediate depths between 504 and 1,211 m, as also occurred with the associated zooplankton collected with suprabenthos (peak biomass between 502 m and 898 m). Suprabenthos biomass did not show any significant correlation with any environmental water-column variable. In contrast, zooplankton (especially small fish and decapod crustaceans) showed a significant positive correlation with fluorometry and turbidity at different levels of the water column. The feeding guilds of species showed important differences between the two areas only on the US, with a higher abundance of deposit feeders in the Catalan Sea (20.4%) than in the Balearic Islands (4.2%). The low contribution of deposit feeders in the SW Balearic Islands may ultimately be a consequence of the lack of river discharges in this area.Communicated by S.A. Poulet, Roscoff     

Epipelagic mesozooplankton succession and community structure over a marine ouffall area in the northeastern South China Sea

This study analyses distribution and abundance patterns of mesozooplankton communities at 13 stations in the coastal waters over a marine outfall area in the northeastern South China Sea. Cruises were conducted in March, June and September 2002, and plankton samples were collected with a 333 microm North Pacific net. The Mesozooplankton was dominated by calanoid Copepods, Cladocera, Chaetognatha and Pteropoda. Stations located near the entrance of the harbor provided a relatively higher abundance of Noctilucales and Radiolarians. In total, 20 zooplankton groups were identified in which, Calanoida, Cladocera, Chaetognatha, Pteropoda, Poecilostomatoida and Appendicularia comprised 92.77% of the total zooplankton abundance. Copepoda dominated in all three cruises, comprising 65.32% of the total mesozooplankton abundance. Samples collected in June recorded higher mesozooplankton abundance than March and September samples. Onshore stations recorded higher BOD values, higher abundance of Noctilucales and Radiolarians and a relativelylower abundance of the overall mesozooplankton. Total mesozooplankton abundance did not correlate significantly with temperature, pH, or dissolved oxygen, but correlated negatively with BOD.     

Spatio-temporal variations in megabenthos abundance in three different habitats of the Catalan deep-sea (Western Mediterranean)

The spatio-temporal variations in the megafauna (fishes, crustaceans, and other invertebrates) in three different habitats on the slope in the Western Mediterranean (Catalan coast off Barcelona) have been investigated. Samples were collected at two fixed stations during 1991 and 1992, one inside and one outside a submarine canyon (at depths between 450 and 600 m) and additional samples were collected at another station on the lower slope (at a depth of 1200 m) in each season of the year. Three replicates of each sample were taken at each station. Differences observed between habitats, seasons, and zoological groupings were verified statistically by factorial ANOVA. The habitat appeared to be the main factor responsible for the differences observed in biomass and abundance values for the zoological groupings considered. Decapod crustacean biomass was higher in the submarine canyon than in neighbouring zones, and smaller species and juveniles were more abundant inside the canyon in the case of both fishes and crustaceans. Fish biomass was most abundant in the lower slope. Seasonality was also a factor, although to a lesser extent. Seasonal variations in biomass, especially fish biomass, were recorded in the deepest zone (1200 m). Crustaceans displayed lower sensitivity to seasonal factors, whereas other invertebrates did not, on the whole, exhibit seasonal variations.     

Research On Zooplankton in the Gulf of Rapallo

Zooplankton samples, collected in autumn 1996 from two stations in the Gulf of Rapallo, Ligurian Sea (Rapallo Harbour and Prelo Bay, which is a more open site with lower human impacts) were analysed. at both stations, the community was dominated by copepods (mainly juveniles and adults of different species of Acartia and Oithona) and meroplankton (mainly polychaete larvae). Total zooplankton abundance in the harbour waters was significantly higher than in the nearby bay. the occurrence of Acartia grani in Rapallo Harbour and Pteriacartia josephinae in Prelo Bay is noteworthy, as they are reported for the first time in the Ligurian Sea, and A. grani has not previously been recorded to the Italian coastline. A three-day benthic chamber experiment aimed to quantify nutrient fluxes between the sediment and water column was performed in the Rapallo Harbour: the profound effects of confinement on the composition and abundance of zooplankton within the incubation chamber are discussed.     

The effects of seston food quality on planktonic food web patterns

In planktonic food webs, the conversion rate of plant material to herbivore biomass is determined by a variety of factors such as seston biochemical/elemental composition, phytoplankton cell morphology, and colony architecture. Despite the overwhelming heterogeneity characterizing the plant–animal interface, plankton population models usually misrepresent the food quality constraints imposed on zooplankton growth. In this study, we reformulate the zooplankton grazing term to include seston food quality effects on zooplankton assimilation efficiency and examine its ramifications on system stability. Using different phytoplankton parameterizations with regards to growth strategies, light requirements, sinking rates, and food quality, we examined the dynamics induced in planktonic systems under varying zooplankton mortality/fish predation, light conditions, nutrient availability, and detritus food quality levels. In general, our analysis suggests that high food quality tends to stabilize the planktonic systems, whereas unforced oscillations (limit cycles) emerge with lower seston food quality. For a given phytoplankton specification and resource availability, the amplitude of the plankton oscillations is primarily modulated from zooplankton mortality and secondarily from the nutritional quality of the alternative food source (i.e., detritus). When the phytoplankton community is parameterized as a cyanobacterium-like species, conditions of high nutrient availability combined with high zooplankton mortality led to phytoplankton biomass accumulation, whereas a diatom-like parameterization resulted in relatively low phytoplankton to zooplankton biomass ratios highlighting the notion that high phytoplankton food quality allows the zooplankton community to sustain relatively high biomass and to suppress phytoplankton biomass to low levels. During nutrient and light enrichment conditions, both phytoplankton and detritus food quality determine the extent of the limit cycle region, whereas high algal food quality increases system resilience by shifting the oscillatory region towards lower light attenuation levels. Detritus food quality seems to regulate the amplitude of the dynamic oscillations following enrichment, when algal food quality is low. These results highlight the profitability of the alternative food sources for the grazer as an important predictor for the dynamic behavior of primary producer–grazer interactions in nature.     

深圳湾浮游动物的群落结构及季节变化

2008年2月、5月、8月和11月分别对深圳湾浮游动物进行了周年的季节调查,结果共检出浮游动物38种和浮游幼体13类,其中原生动物2种,腔肠动物4种,介形类1种,桡足类22种,软甲类3种,毛颚类3种,被囊类1种,多毛类2种,浮游幼体（包括仔鱼）13类。年均丰度和生物量分别为406.7 ind.m-3和764.0 mg.m-3,高峰均位于夏季,低谷分别位于冬、春季。种类数（包括浮游幼虫）秋季最多为43种,夏季次之为30种,冬季最少仅23种。主要优势种为太平洋纺锤水蚤Acartia pacifica、刺尾纺锤水蚤Acartia spinicauda、短角长腹剑水蚤Oithona brevicornis、双生水母Diphyes chamissonis、卡玛拉水母Malagazzia carolinae、蔓足类幼体和桡足幼体等。多样性指数和均匀度年均值分别为2.568和0.526。回归分析表明浮游动物丰度和生物量与各环境因子之间存在明显的相关性,但有季节变化。     

Analysis of the biological cycle of Acartia clausi (Copepoda) in a meso-oligotrophic coastal area of the eastern Mediterranean Sea using time-series analysis

We evaluated the duration of Copepodite Stages C1 to C6, the biological cycle and the number of annual generations of the planktonic copepod Acartia clausi in a meso-oligotrophic area of the eastern Mediterranean Sea (Saronikos Gulf, Greece). The results were based on 95 zooplankton samples collected during the period November 1988 through June 1990, at intervals of 1, 2, 7 and 15 d, the sampling intervals being dependent on the abundance of A. clausi. Time-series analysis (cross-correlation) of fluctuations in the comparative abundance (percentages) of the copepodite stages present was used to determine the duration of the development stages and generation length. This methodology could significantly contribute to the identification of cohorts, and hence to the estimation of stage duration, from field data for a given copepod species. The development of A. clausi stages was not isochronal; duration of the first copepodite stage was shorter than that of the last three stages. The mean generation length estimated (28.6 d) is among the highest recorded in the literature for A. clausi at the range of temperatures prevailing in the area (13 to 25°C). Throughout the year there were four or five generations. The possible limiting role of food availability on the duration of each stage and hence on generation length is also discussed.