Foraminiferan (Protozoa) epizoites on deep-water arcturids (Crustacea,Isopoda)

Foraminiferan (Protozoa) epizoites were examined on two deep-water isopods, Neastacilla sp. and Pleuroprion hystrix (Valvifera, Arcturidae), from the north Atlantic Ocean and the Nordic Seas. Most foraminiferans belonged to genus Cibicides and occurred on 27% of Neastacilla and 23% of Pleuroprion hystrix. The pattern of foraminiferan epibiosis was similar in both species, with a concentration on the dorsal body and on the posterior pereopods. The arcturids showed an increase in number of foraminiferans with increased body size, suggesting that available time span for settling on the younger stages (mancas) was relatively short. There was a trend towards larger numbers of foraminiferans occurring on larger arcturid species, suggesting that available space is the factor that determines the total number of foraminiferans for epibenthic arcturid isopod species.     

Colonisation and bioerosion of experimental substrates by benthic foraminiferans from euphotic to aphotic depths (Kosterfjord, SW Sweden)

In the cold-temperate setting of the Swedish Kosterfjord area, experimental carbonate and PVC substrates were deployed for a 6, 12 and 24-month duration along a transect from euphotic to aphotic depths in order to study bioerosion and carbonate accretion patterns. Among the organisms that contribute to the latter by secreting calcareous skeletons, epibenthic foraminiferans represent a major component, both in terms of diversity (a dozen species) as well as in the number of individuals (exceeding 50,000 individuals per m² at certain depths). The by far dominating species were found to be Cibicides lobatulus and the agglutinating Lituotuba lituiformis, along with smaller numbers of Planorbulina mediterranensis, Tholosina vesicularis and Nubecularia lucifuga. The foraminiferal distribution exhibits a pronounced abundance maximum in shallow waters at 7 and especially 15 m and a maximum in diversity at 15-50 m water depth. Some of the foraminiferans encountered, such as Cibicides lobatulus and the rare Gypsina vesicularis, were found to contribute also to the bioerosion of the calcareous substrates by etching shallow attachment scars. These prominent traces witness the former presence of benthic foraminiferans on fossil to Recent hardgrounds, inferring a potential applicability as an in situ proxy where tests are not preserved. Estimated minimum carbonate production rates for the dominant Cibicides lobatulus reach a maximum of 0.326 g/m²/year with the highest rates occurring at 7 to 30 m water depth. Carbonate production rates are up to two magnitudes higher on the PVC (0-0.326 g/m²/year) than on the carbonate substrates (0-0.010 g/m²/year) and are considerably higher than estimates previously reported from the western Baltic.     

Feeding by larvae of Hypoatherina tropicalis (Pisces: Atherinidae) and its relation to prey availability in One Tree Lagoon,Great Barrier Reef,Australia

Synopsis Feeding of and food availability for larvae of Hypoatherina tropicalis were investigated in One Tree Lagoon, Great Barrier Reef, Australia, during November 1981 and January 1982. These surface-dwelling larvae and their microzooplankton prey were sampled as near to simultaneously as possible on 12 occasions during the daytime. Larvae of all sizes (5–17 mm SL) fed successfully over the observed range of mean prey densities (12–235 per liter), and the overall feeding incidence was 98.9%. Larger larvae consumed greater numbers and more categories of prey than did smaller larvae. Larvae selected copepods of all sizes, and nauplii, gastropods, bivalves, and foraminiferans that were greater than 75 ¢s mm in width. Tintinnids (mostly 37–74 µm in width) were generally avoided by larvae, but were occasionally important in the diets when they constituted more than 60% of the total available prey, regardless of the density of the selected prey categories. Larvae less than 14 mm SL ingested meroplankton (gastropods, bivalves, foraminiferans, and polychaetes) in direct relation to the densities available, and without regard to the densities of copepods available. However, the largest larvae (14–17 mm SL) ingested meroplankton in inverse relation to the density of copepods available, indicating that larvae consumed more meroplankton when the concentration of copepods was low. Such flexibility and opportunism in feeding behavior may increase the larvae's chances of obtaining adequate nutrition during periods of suboptimal feeding conditions.     

Growth, summer cohort output, and observations on the reproduction of brook silverside, Labidesthes sicculus (Cope) in the Kawartha Lakes, Ontario

The brook silverside, Labidesthes sicculus (Cope), is unique in Canadian waters, as it completes its life cycle in 1 year. Previous studies based on scale ageing had suggested the species was an “annual,” but we confirmed this for the first time by otolith analysis. Growth rates from both back-calculation, and the Gompertz model, indicated an asymptote near the end of the summer, and average summer growth rates of 0.77 and 0.70 mm/day, respectively. The Gompertz model gave the best fit (n = 201, r = 0.744) with an L∞ of 85.4 mm TL, and instantaneous growth rate, g, of 0.0264. Back-counting daily growth increments allowed us to show that broods of young fish were produced throughout the summer, from late May to mid August, with maximum hatch taking place in mid-July. The species is a “batch” (serial) spawner, with only a fraction of the eggs ripening in the ovary and being released at as yet undetermined intervals. Eggs of the larger immature fish in the first summer developed from 0.05 to 0.21 mm in diameter (preserved) by fall, and in mature fish of the following spring and summer, developed to 1.2 mm in diameter (preserved), 1.4 mm fresh, at spawning. Attached to each egg was a filament averaging 2.0 cm in length, adhesive in nature, and presumably for attachment to vegetation. The egg also had microscopic hairs on its surface. No evidence was found to support temperature-dependant sex determination, nor were embryos or sperm found in the ovaries of spawning females, unlike Labidesthes sicculus vanhyningi, (the southern subspecies) which has internal fertilization. The Canadian species possesses a genital papilla through which the eggs were released, and an apparently much smaller male genital papilla than the southern subspecies.     

Benthic meiofaunal density and community composition in the deep White Sea and their temporal variations

In spite of the fact that shallow-water meiobenthos of the White Sea is a relatively well studied, the information on meiobenthic fauna from the deepest part of this sea is still very scanty. This study represents the first major study of the meiobenthos from the deep White Sea. The composition of the meiobenthic community, density and vertical distribution was studied during four sampling occasions in the deepest part of the Kandalaksha Depression (White Sea) in July 1998, October 1998, May 1999 and November 1999. Samples were collected from a depth of 270?m with the aid of a multicorer. The total density of meiobenthos in 1998 was twice than in 1999 (on average, 2,356 and 1,464 ind./10?cm², respectively). The most abundant meiobenthic group was Foraminifera (59?%), followed by Nematoda (26?%) and Harpacticoida (7?%). These relative and absolute abundance values are comparable with the same depth interval in Arctic and temperate regions. The density of foraminiferans and nematodes was higher in the autumn and lower in the summer. This may be explained by the mass propagation of these animals in the autumn season: the density of juvenile nematodes and small-sized foraminiferans increased significantly in the 1- to 4-cm-deep sediment layers in autumn. The size range of the meiobenthos in the deepest part of the White Sea was also comparable to deep-sea meiobenthos (the 63–125 and 125–250?μm size classes were most dominant).     

Rogerella isp. Infesting the Pore Pairs of Hemipneustes striatoradiatus (Leske) (Echinoidea: Upper Cretaceous,Belgium)

An otherwise well-preserved test of the holasteroid echinoid Hemipneustes striatoradiatus (Leske) from the Emael Member, Maastricht Formation (Maastrichtian, Upper Cretaceous) of Belgium, is infested by encrusting bivalves and foraminiferans and the boring Rogerella isp. In this specimen, Rogerella preferentially infested and modified the ambulacral pore pairs of the echinoid close to the apex. This was not a commensal association. The echinoid test shows no growth deformations in response to this invasion; pore pairs are locally strongly infested; and encrusting invertebrates testify to the long post-mortem residence time of the test on the sea floor. Rather, the pore pairs of the dead echinoid were crannies attractive to settling larvae of acrothoracian barnacles, the producers of Rogerella.     

Diet and macronutrient niche of Asiatic black bear (Ursus thibetanus) in two regions of Nepal during summer and autumn

Relatively little is known about the nutritional ecology of omnivorous Asiatic black bears (Ursus thibetanus) in Nepal. We characterized the diet of black bears in two seasons (June–July, “summer”; and October–November “autumn”) and two study areas (Dhorpatan Hunting Reserve [DHR]; and Kailash Sacred Landscape [KSL]). We then conducted nutritional analysis of species consumed by black bears in each study area, in combination with nutritional estimates from the literature, to estimate the proportions of macronutrients (i.e., protein [P], lipid [L], and carbohydrate [C]) in the seasonal bear foods and diets, as well as their macronutrient niche breadth. We found that bamboo (Arundinaria spp.) had the highest relative frequency in both study areas and seasons. Ants and termites were found in DHR diets, but not KSL diets. One anthropogenic crop was found in DHR summer diets (Zea mays) and two were found in KSL summer diets (Z. mays; and Kodo millet [Paspalum scrobiculatum]). Other than insects, no animal prey was found in either diet. The proportions of macronutrients in diets (i.e., realized macronutrient niches) were relatively high in carbohydrate for both study areas and seasons: DHR_summer 24.1P:8.7L:67.2C; KSL_summer 16.7P:8.2L:75.1C; DHR_autumn 21.1P:10.5L:68.4C; KSH_autumn 19.0P:11.0L:70.0C. Macronutrient niche breadth was 3.1 × greater in the DHR than KSL during summer, and 4.0 × greater in the autumn, primarily due to the higher proportion of lipid in ants and termites relative to plant foods. Within‐study area differences in niche breadth were greater during summer than autumn; in the KSH the macronutrient breadth was 1.4 × greater in summer, while in the DHR it was 1.1 × greater in summer. Similarity in dietary macronutrient proportions despite differences in foods consumed and niche breadth are suggestive of foraging to reach a preferred macronutrient balance.     

The Nutritional Status and Eating Habits of Shift Workers: A Chronobiological Approach

The eating habits of workers may vary according to the season of the year and corresponding work schedule. A study aiming at verifying the changes in their diet in summer and winter, as well as the nutritional status of those who work fixed shifts, was conducted. The distribution during the 24 h in the quantity of calories and macronutrients ingested and the circadian rhythm of calories consumed were also analyzed. The study was conducted on 28 workers subject to three fixed work (morning, afternoon, and night) shifts at a transport company in the city of São Paulo, Brazil. The mean age of the workers was 32.8 (SD ± 5.3) yrs. Their food intake was ascertained by the use of a 3-day dietary record, and their nutritional status was evaluated by their body mass index (BMI), both in winter and summer. Two-way ANOVA (shift and season) showed food consumption—measured in calories/24 h—was significantly higher in winter than summer (F_(1.25) = 11.7; p < 0.001). No statistically significant differences were found among shifts (F_(2.25) = 0.85; p < 0.44), and the interaction effect between shift and season was also not significant (F_(2.25) = 0.15; p < 0.86). No seasonal difference in BMI was detected (Kruskal-Wallis test). Cosinor analyses showed circadian rhythmicity in calories consumed by morning (p < 0.01) as well as afternoon shift workers (p < 0.001), both in the winter and summer. Circadian rhythmicity in calories consumed by night workers was found only in summer (p < 0.01). The changes observed in the workers’ eating habits from one season to another and during the 24 h period show the need for further studies to help develop educational programs to improve the nutrition of shift employees taking into consideration shift schedule and season of the year when work is performed.     

Effects of season on sleep and skin temperature in the elderly

The effects of season on sleep and skin temperature (Tsk) in 19 healthy, elderly volunteers were investigated. Measurements were obtained in summer, winter, and fall, and activity levels were monitored using a wrist actigraph system for five consecutive days. The temperature and humidity of the bedrooms of the subjects’ homes were measured continuously for five days. During actigraphic measurement, Tsk during sleep was measured for two nights. The bedroom temperature and humidity significantly increased in summer compared to winter and fall. In summer, the total sleep time decreased (mean ± SE min; summer, 350.8 ± 15.7; winter, 426.5 ± 14.2; fall, 403.2 ± 16.4) and wakefulness increased (P < 0.003) compared to those in fall or winter. The sleep efficiency index that was derived from wrist actigraphy was significantly decreased (P < 0.001) in summer (81.4 ± 2.9%) compared with winter (91.6 ± 1.3%) or fall (90.2 ± 1.2%). The forehead Tsk significantly increased, while the chest and thigh Tsks were decreased in summer compared to those in fall or winter. These results suggest that, in the elderly, sleep is disturbed in summer more than in other seasons, and that this disturbance is related to fluctuations in Tsk.     

Throughfall,stemflow and interception of rainwater in an evergreen broadleaved forest

In order to analyze the dyanmics of heavy metals in a forest ecosystem, throughfall and stemflow were collected for individual rain showers in an evergreen broad-leaved forest dominated byCastanopsis cuspidata. The relation between throughfall (or stemflow) (Px) and gross rainfall (P) was approximated by a linear regression equationPx=a(P-b). The values of coefficient “a” were 0.32–2.02 for throughfall at each sampling point and the mean values for 1976 and 1977–1978 were 0.682 and 0.767, respectively. The stemflow volume differed widely among individual trees, depending mainly on the tree form of each species. In particular, the tree form ofPasania edulis was found to be especially suited to collecting stemflow. OneP. edulis tree collected 64% of the rainwater that fell onto its crown as stemflow. The ratio of stemflow to gross rainfall decreased in summer resulting from an increase in leaf biomass and an increase in air temperature. In fact, the values of coefficient “a” for mean stemflow per unit area were 0.180 for summer and 0.229 for other seasons in 1976, and 0.145 for summer and 0.155 for other seasons in 1977–1978 for different sampled trees.     

Growth and tissue mass cycles in the infaunal bivalve Yoldia eightsi at Signy Island, Antarctica

Shell growth in Yoldia eightsi was measured over an austral summer and winter in 1992. In specimens < 12 mm length, growth was not significantly different between summer and winter periods, and the fastest recorded rate, 6.3 μm day⁻¹ was for 5-mm individuals during the winter. In summer, specimens of all lengths grew significantly, but in winter bivalves > 27 mm length did not increase in length. Tissue dry and ash-free dry mass (AFDM) cycles were assessed at monthly intervals between December 1988 and January 1991. ANCOVA indicated significant interannual and seasonal effects on this cycle. Tissue mass increased in the summer, coinciding with the phytoplankton bloom and the period of maximum sedimentation of organic material from the water column. A standard 20-mm-length animal reached a maximum AFDM of 114 mg in February 1990. The minimum value (68 mg AFDM) throughout the 2 years of measurements was in early December 1988, at the end of the austral winter. Periods of tissue mass increase were, therefore, decoupled from shell growth, at least in juveniles. Tissue mass was significantly higher in 1990 than 1989, which was mainly due to high organic contents in the summer (January to May). This was not consistent with the pattern of organic content in the sediments at the study site, but was in phase with the cycle in sediment chlorophyll a content. Tissue mass increase depended on major resource input during the summer, but Y. eightsi was capable of maintaining winter condition from stocks of benthic microalgae in years of poor ice cover. Tissue mass declined between April and July each year. This was accompanied by large falls in tissue ash content, and coincided with the spawning period in early June. These are the first monthly tissue mass data collected over a 2-year period for an Antarctic mollusc. They are the first such data indicating seasonal variation in tissue mass and showing a decoupling of shell and tissue growth in a polar bivalve. The P/B ratio calculated from these data was 0.106, which is slightly lower than previous values found for this species, but is in line with general values for Antarctic marine benthos. Accepted: 6 December 1999     

Impact of season on antioxidants,nutritional metabolic status,cortisol and heat shock proteins in Hariana and Sahiwal cattle

The aim of this study was to evaluate the effects of summer and winter seasons on antioxidant status, body reserve mobilization and biomarkers of stress in Hariana and Sahiwal cows. Twelve lactating cows (six of each Hariana and Sahiwal cows) were included in summer (May to July) and winter season (November to January) study. Microclimatic observations were recorded on daily basis during the experimental period. In both seasons, blood samples were collected at fortnightly intervals for analysis of total antioxidant activity, non-esterified fatty acids (NEFA), β-Hydroxybutyric acid (BHBA), heat shock protein 70 and 90 (HSP70 and HSP90). Antioxidant activity reduced significantly (p < 0.05) in Hariana cattle during summers as compared to winters; whereas, seasonal variation exerts no effect on antioxidant activity in Sahiwal. Blood NEFA concentration was similar among both the breeds over both the seasons but reduced significantly (p < 0.05) during summer season as compared to winters in both the breeds. BHBA concentration was significantly higher (p < 0.05) in Hariana cows than Sahiwal cows during winters, however, no effect on BHBA level was observed during summer season in both the breeds. Significantly, lower plasma cortisol level (p < 0.05) was found during winter season in Sahiwal as well as Hariana cows. Further, Sahiwal exhibited lower plasma cortisol as compared to Hariana in both the seasons. HSP 70 and 90 showed non-significant differences between breeds within both the seasons. However, significantly, lower plasma HSP 70 levels (p < 0.05) were reported during winter season in Sahiwal as well as in Hariana cows. Results of present study revealed that indigenous Sahiwal is more heat tolerant as compared to Hariana breed.     

Hindgut microbes, fermentation and their seasonal variations in Hokkaido native horses compared to light horses

Fecal bacteria and protozoa of Hokkaido native horses and light horses were enumerated to compare seasonal variation in hindgut microbes and fermentation between the two breeds. Fecal samples were collected in winter and summer from eight horses (four for each breed) that had been reared together under the same conditions after birth (on woodland pasture in winter and on grassland pasture for the rest of the year). Total fecal bacteria counts for both breeds showed temporal variation, with the highest levels occurring in summer (P<0.05). For both breeds, Gram-negative rods were the major constituents (58–69%) and showed higher counts in winter (P<0.05) than in summer. Total protozoa counts in both breeds were lower in winter than in summer (P<0.05). The proportion of large cellulolytic protozoa such as Cochliatoxum periachtum was increased (P<0.05) in winter, and this tended to be more pronounced in native horses. Although total volatile fatty acids (VFA) in feces were lower in winter (P<0.05), the reduction was smaller in native horses (P<0.05). Fecal VFA pattern showed a shift toward more acetate and less propionate production in winter regardless of the horse breed. Evaluation of digestive tract organs in 12 animals showed that the relative weight of the colon in body weight or total digestive tract weight is larger in native horses than in light horses (P<0.05). The present results suggest that hindgut microbial adaptation to winter diets occurs to a greater extent in native horses, as partly characterized by advantages in anatomy.     

Seasonal variation in hematocrit levels of Amethyst Sunbirds (Chalcomitra amethystina) over an altitudinal gradient

The distribution range of Amethyst Sunbirds (Chalcomitra amethystina) within southern Africa includes an altitudinal gradient from the Drakensberg to the coast of KwaZulu-Natal. We expected that, over this altitudinal gradient, Amethyst Sunbirds would exhibit variation in hematocrit levels pre- and post-acclimation, as well as seasonally. Sunbirds from three locations; Underberg (1,553 m asl), Howick (1,075 m asl) and Oribi Gorge (541 m asl) were used for this study. Birds were then acclimated at 25°C for 6 weeks on a 12L:12D cycle. Hematocrit levels were taken pre-acclimation and pre-release. We found significant variation in hematocrit levels during summer, but surprisingly little variation during winter. Season and location had a significant combined effect on pre-acclimation hematocrit levels of Amethyst Sunbirds. Underberg and Howick had greater values in summer compared with winter whereas the converse was found in Oribi Gorge. In contrast, season and location had no significant combined effect on post-acclimation hematocrit levels of Amethyst Sunbirds, with post-acclimation levels similar for the three sites irrespective of season. This study emphasizes the need to understand flexibility in hematocrit levels and acknowledge seasonal and altitudinal differences within a species.     

Composition and community structure of the coralline algal reefs from Atol das Rocas, South Atlantic, Brazil

 Coralline-algal frameworks from Atol das Rocas reefs were sampled along windward and leeward transects, and multivariate statistical analysis was used to investigate the composition and community structure of the encrusting community. The following components of the reefs were identified in slabbed and polished reef blocks sampled along each transect: encrusting coralline algae dominated by Porolithon cf. pachydermum, vermetid gastropods, Homotrema rubrum, acervulinid foraminiferans, molluscs, corals, polychaete tubes, clionid sponge borings, polychaete/sipunculid borings, cemented sediments, and growth cavities. Q-mode cluster analysis correctly classified 78% of all windward samples and 69% of all leeward samples, and R-mode separated reef components adapted to high wave energy environments from those adapted to low wave energy. Separate classification and ordination of samples from each transect indicate that seriation breakdown occurs in the windward reef between 25 and 45 m from the reef front. In the leeward reef between 75 and 90 m from the leeward reef front, seriation breakdown was not found to be significant. These results confirm that seriation (zonation) is best developed in the windward reef, as has been documented in coral-dominated reefs. Accepted: 28 February 2000     

The response of meiofauna to sediment disturbance

The meiobenthos inhabiting an intertidal mud bar were disturbed by hand-turning the sediment of a 9-m² area with a shovel and monitoring the subsequent recolonization process.The immediate impact of the disturbance on this community dominated by Nematoda (91%), Copepoda (4%) and Foraminifera (4%), was to remove more than 70% of the meiofauna. However, after only one tidal cycle, total numbers of nematodes, copepods, foraminiferans and other meiofauna taxa were at predisturbance and control (similar 9-m² site on the same flat) density values. Nematode species assemblages rapidly adapted to the disturbance and changed little over time. Foraminifera showed insignificant fluidized flocculent upper layer of sediment was probably the major dispersal mechanism in this community, and foraminiferans seem to be the least able to use this mechanism.The meiobenthos of this habitat is described as a well-dispersed and dynamic community able to rapidly adjust to small-scale disturbances. However, the meiobenthos may not recover from all disturbances, because resilience was only determined for a limited physical disturbance.     

Integrating sub-lethal heating with Brassica amendments and summer irrigation for control of Macrophomina phaseolina

Effects of varying intensities of sub-lethal heating were ascertained in improving the efficiency of Brassica amendments and summer irrigation on survival of Macrophomina phaseolina, a dry root rot pathogen. Sub-lethal heating (45–55°C) of M. phaseolina infested dry soil reduced the viable propagules by only 12.8% in a period of 90 days. One summer irrigation without sub-lethal heating caused 33.9% reduction in M. phaseolinapropagules, which improved to 43.3% when it was combined with 60 days of sub-lethal heating. Addition of the Brassicaamendments to irrigated soil resulted in significant reduction (60.4–71.6%) in counts of M. phaseolinabut this reduction improved (89.4–96.1%) when sub-lethal heating was combined with amendments. Mustard oil-cake (0.18% w/w) was found to be the most effective with reduction but a 94% inoculum reduction by mustard pod straw (0.36% w/w) was also achieved at 0–30 cm soil depth under similar conditions. Moderate heat level could not exert detectable weakening effect on M. phaseolinapropagules. These results suggest a practical cultural control of soil-borne pathogens by combining sub-lethal heating, Brassica amendments with one summer irrigation.     

Differences in larval dynamics of golden mussel <Emphasis Type="Italic">Limnoperna fortunei</Emphasis> between dam reservoirs with and without an aeration system

The golden mussel Limnoperna fortunei is a freshwater bivalve that adheres to water intake facilities, leading to problems of several kinds. Biofouling problems have been increasing recently in East Asia and South America, and the planktonic stage of this species is considered to play an important role in its dispersal. We investigated the larval dynamics of L. fortunei in two reservoirs, Lake Ohshio and Lake Takenuma, which are connected by a headrace channel. An aeration system for water quality conservation was present in the former reservoir but not in the latter. Larval density in Lake Ohshio was more than 10,000 individuals/m³ with a maximum of 80,000 individuals/m³ in summer. The density in Lake Takenuma was much lower, with a maximum of around 200 individuals/m³. Water temperature (WT) and dissolved oxygen (DO) concentration were almost uniform regardless of water depth in Lake Ohshio because of destratification due to continuous aeration. Summer WT and DO in the lake were considered to be suitable for survival and reproduction of L. fortunei. On the other hand, stratification was found for WT and DO in Lake Takenuma throughout the summer. The low WT and DO found in the deep areas of the lake in summer were considered to be not suitable for survival and reproduction of this species. Thus, the population of L. fortunei larvae differed widely even in two adjoining lakes, and WT and DO are considered to be critical factors, especially for reproduction.     

Distribution and summer diapause of Canthocamptus staphylinus (Jurine) (Copepoda: Harpacticoida) in Lake Ladoga

The spatial distribution of Canthocamptus staphylinus (Jurine) in Lake Ladoga was examined. C. staphylinus is one of the most numerous species of harpacticoids in the lake. It can dwell in almost all littoral biotopes. In profundal biotopes strongly exposed to anthropogenic influence (pollution and eutrophication) only this species of harpacticoid was found. A peculiarity of C. staphylinus biology is that in summer individuals are in the resting stage as cysts. In summer active individuals were found in littoral habitats at a water temperature of 20 °C, but their number was small in comparison with cold periods of the year. In the littoral zone the relative number of individuals in cysts was clearly related to water temperature. Twelve degrees temperature appears to be critical for development of littoral populations of C. staphylinus.     

东海低氧区及邻近水域浮游植物的季节变化

根据2011年5月、8月、11月在东海低氧区及邻近水域(25°00'—33°30'N,120°00'—127°30'E)进行的多学科综合调查,对东海低氧区及邻近水域浮游植物群落结构特征及季节变化进行了相关研究。经Utermhl方法初步分析共鉴定出浮游植物4门74属248种(含变种、变型,不含未定种),主要由硅藻和甲藻组成,此外还有少量的金藻和蓝藻。春季优势种主要为具齿原甲藻(Prorocentrum dentatum)、柔弱伪菱形藻(Pseudo-nitzschia delicatissim)、骨条藻(Skeletonema sp.)和具槽帕拉藻(Paralia sulcata);夏季主要是中肋骨条藻(Skeletonema costatum)和海链藻(Thalassiosira sp.);秋季主要是具槽帕拉藻、圆筛藻(Coscinodiscus sp.)和柔弱伪菱形藻。调查区浮游植物平均细胞丰度在夏季最高,达到85.002×103个/L,春季次之,秋季最低。在水平方向上,春、夏两季,表层浮游植物细胞丰度在近岸出现高值,由近岸到外海细胞丰度逐渐降低;而在秋季则相反,在调查海域的东北部出现高值,随离岸距离的增加细胞丰度逐渐增加。在垂直方向上,春、夏两季,浮游植物细胞丰度在表层出现最大值,随着深度的增加细胞丰度逐渐降低;而在秋季细胞丰度分布比较均匀,随水深变化不明显。调查区表层浮游植物ShannonWiener多样性指数和Pielou均匀度指数的平面分布基本一致,并且与细胞丰度的分布大致呈镶嵌分布。调查浮游植物群落的演替规律是:从春季的甲藻(具齿原甲藻、微小原甲藻(Prorocentrum minimum)等)为主,硅藻(柔弱伪菱形藻、骨条藻等)为辅;演替至夏季的硅藻(中肋骨条藻、海链藻等)为主,甲藻(主要是梭状角藻(Ceratium fusus)和叉状角藻(Ceratium furca))为辅,到秋季进一步演替为硅藻(具槽帕拉藻、圆筛藻、柔弱伪菱形藻等)为主,铁氏束毛藻(Trichodesmium thiebaultii)为辅。浮游植物物种组成、优势种、细胞丰度及多样性指数均表现出明显的时空变化。低氧区与非低氧区浮游植物群集存在明显差异。