Short term spatial — temporal distribution patterns of zooplankton in Admiralty Bay (Antarctica)

The present work analyses the abundance and species composition of mesozooplankton in relation to different patterns of wind speed and tides in Admiralty Bay. The plankton was sampled on 12, 13 and 15 March 1989 with a 385 m mesh size conical-cylindrical net by R.V. Barão de Teffé. In Martel Inlet, the zooplankton standing stock reached 25,223 individuals 100 m^–3 during the high tide. Under north-west winds, the abundance of the dominant species Ctenocalanus citer and Fritillaria borealis followed the tidal cycle. Weak south-west winds promoted the input of plankton even during low tide. Throughout the Bay, the highest densities of plankton (446–2,899 individuals 100 m^–3) were observed in surface waters flowing towards the Bransfield Strait. Surface waters flowing through the Bay and the inlets showed different species composition to surface waters flowing towards the Bransfield Strait.     

Vertical distribution and abundance of gymnamoebae (Rhizopoda) in bottom sediments of the brackish water Nivå Bay (Baltic Sea,The Sound)

The sandy sediments of Niv? Bay (Baltic Sea, The Sound, Denmark) are often covered with the mats of sulphur bacteria and are temporarily anoxic. The vertical distribution and abundance of naked amoebae species in three sediment cores from this bay were studied. Amoebae were most abundant and diverse in the upper 1 cm of sediment, and their number and diversity decreased with increasing depth into the sediment. Amoebae were recovered from both upper oxygenated and deep anoxic layers of sediments. The species composition and abundance of amoebae was very heterogeneous, even at spatial scales of several centimeters, suggesting the existence of microhabitats selectively occupied by particular species. All species found were recorded from aerobic cultures and some of these amoebae occur in both the aerobic and anaerobic layers of the sediment. Minimal possible number of amoebae in the sediments, estimated for the first time as areal abundance integrated for depth was: core 1 -597 cm(-2); core 2 -1,110 cm(-2); core 3 -1,430 cm(-2). These abundances are probably best regarded as "potential" abundances of amoebae hidden in the sediments, as the question of the ratio between active and resting amoebae remains open.     

The spatial distribution pattern of the brown planthopperNilaparvata lugens Stål (Homoptera: Delphacidae) in west Java,Indonesia

Spatial distribution pattern of the brown planthopper (BPH) was analyzed at 9 experimental fields in the northern part of West Java during two consecutive rice cropping seasons, i.e., wet and dry seasons. The population of each developmental stage and wing form of BPH at each location showed consistent departure from the random (Poisson) distribution, the variances of the densities in most cases exceeding their means. Namely, the distribution pattern of BPH per hill of rice plant was found to have a general tendency to be aggregated or contagious and to fit fairly well to the negative binomial model. The tendency for aggregation was further confirmed by both the β-values of -m regression being larger than unity and the C_A-values being larger than zero for each developmental stage. Although significant variations in the distribution pattern as measured by β- or C_A-value were observed between different developmental stages, between wing forms and among locations, the degree of aggregation for a given developmental stage at each experimental field remained fairly stable throughout the crop period, despite wide temporal changes in population density. Possible factors to explain these characteristics of the spatial distribution pattern of the BPH in West Java were discussed with reference to the process generating it.     

Spring zooplankton distribution and production of the copepod Euterpina acutifrons in Marennes-Oléron Bay (France)

Short term variations of zooplankton populations were studied during an algal spring bloom in two characteristic areas of the Marennes-Oléron Bay (France). The sampling sites were chosen in the north of the bay, one close to the neritic zone, the other close to the estuarine zone. Five distinct zooplanktonic communities were observed: two typical neritic and estuarine assemblages, two eurytopic groups (linked to neritic or estuarine water masses) and an autochtonous community, widely distributed in the north of the bay. The copepod Euterpina acutifrons dominated the zooplankton community during this period of the year in terms of abundance (up to 83% of the zooplankton community). Its production differed between water masses: the highest production occurred at the estuarine station (3.48 ± 0.65 mg C m^–3 d^–1), where nauplii accounted for a large part of these high values. Its P/B ratio was similar at the two stations (0.196 and 0.209 d^–1).     

Seasonal and vertical distribution of the ciliated protozoa and micrometazoa in Kaštela Bay (central Adriatic)

Seasonal and vertical distribution of tintinnids, non-loricate ciliates and micrometazoa were studied in Kaštela Bay (central Adriatic Sea) throughout 1995. The species composition of tintinnids and copepods were studied as well. This is the first estimation of non-loricate ciliate biomass in the coastal area of the central Adriatic. Non-loricate ciliates were quantitatively the best represented ciliated protozoa, whereas nauplii were the most numerous micrometazoan organisms. Temperature affected the distribution of most micrometazoan components of the zooplankton and that of non-loricate ciliates. The temperature-dependent presence of individual size categories of non-loricate ciliates was also established. Apart from the interaction between microzooplankton groups, the influence of biotic factors, such as phytoplankton, bacteria, non-pigmented nanoflagellates (NNF) and mesozooplankton, was also discussed. The abundance of ciliates was controlled by both food supply (phytoplankton and NNF) and micrometazoan grazing. The results point to very complex trophic relationships within the planktonic community, suggesting that microzooplankton could be an important link between the microbial food web and higher trophic levels. Received in revised form: 8 November 2000 Electronic Publication     

Kin-biased distribution in brown trout: an effect of redd location or kin recognition?

A wide range of animals have been reported to show kin-biased behaviours, such as reduced aggressiveness and increased food sharing among relatives. However, less is known about whether wild animals also associate with relatives under natural conditions, which is a prerequisite to facilitate kin-biased behaviours and hence kin selection. We tested, by means of microsatellite polymorphism, correlations between pair-wise relatedness and pair-wise metric distance in wild brown trout (Salmo trutta L.) under natural conditions in two streams. Our data show that young-of-the-year as well as older trout found close together also had a higher genetic relatedness in one of the two streams, whereas no relationship was found in the other stream. Very few half and full siblings were found in the second stream and under these conditions it is unlikely that kin-biased behaviours will receive positive selection. We discuss the underlying mechanisms for the observed structure and we specifically address the issue of whether the grouping of related individuals could reflect dispersal from the same spawning redds, or if it reflects active association with relatives, possibly conferring kin-selected advantages.     

Ecological impact of a fresh-water “reef kill” in Kaneohe Bay,Oahu, Hawaii

Storm floods on the night of December 31, 1987 reduced salinity to 15 in the surface waters of Kaneohe Bay, resulting in massive mortality of coral reef organisms in shallow water. A spectacular phytoplankton bloom occurred in the following weeks. Phytoplankton growth was stimulated by high concentrations of plant nutrients derived partially from dissolved material transported into the bay by flood runoff and partially by decomposition of marine organisms killed by the flood. Within two weeks of the storm, chlorophyll a concentrations reached 40 mg m^-3, one of the highest values ever reported. The extremely rapid growth rate of phytoplankton depleted dissolved plant nutrients, leading to a dramatic decline or crash of the phytoplankton population. Water quality parameters returned to values approaching the long-term average within 2 to 3 months. Corals, echinoderms, crustaceans and other creatures suffered extremely high rates of mortality in shallow water. Virtually all coral was killed to depths of 1–2m in the western and southern portions of the bay. Elimination of coral species intolerant to lowered salinity during these rare flood events leads to dominance by the coral Porites compressa. After a reef kill, this species can eventually regenerate new colonies from undifferentiated tissues within the dead perforate skeleton. Catastrophic flood disturbances in Kaneohe Bay are infrequent, probably occurring once every 20 to 50 years, but play an important role in determination of coral community structure. The last major fresh water reef kill occurred in 1965 when sewage was being discharged into Kaneohe Bay. Coral communities did not recover until after sewage abatement in 1979. Comparison between recovery rate after the two flood events suggests that coral reefs can recover quickly from natural disturbances, but not under polluted conditions.     

A “Bloom” in the Water of Amursky Bay (Sea of Japan) Caused by the Dinoflagellate Oxyrrhis marina Dujardin, 1841

A bloom in the water of Amursky Bay (Sea of Japan) caused by the dinoflagellate Oxyrrhis marina Dujardin, 1841 was recorded for the first time. The highest density of this species in the bloom area was 443.3 million cells/liter. The abundant development of microalga was observed from July to September 2002 at a water temperature of 17–24.5°C and a salinity of 7–18. Changes in the density of O. marina and other species of phytoplankton during the bloom period are analyzed. Possible reasons for the blooms of O. marina in Amursky Bay are discussed.     

Leaf-consumption levels in subtropical mangroves of Paranaguá Bay (SE Brazil)

The objective of this study was to measure leaf consumption levels, mainly by insect herbivores and the tree-dwelling crab Aratus pisonii (H. Milne Edwards, 1837), in mangrove forests of a large subtropical estuarine system in the South Atlantic Ocean, to determine if patterns of herbivory varied with forest structure, tree species and marked seasonal differences in rainfall and temperature. We analyzed three structurally different mangroves located in the euhaline high-energy sector of Paranaguá Bay, all of them with known values of annual litter fall. Consumption levels varied from 2.2–5.4% of total leaf area considering each site as a whole, and from 2.0–6.0% considering each tree species separately. No significant differences in consumption levels were found between summer and winter samples, but significant differences were found among sites and among tree species. Leaves from Laguncularia racemosa were most consumed. The site with lower consumption levels was the one covered with dwarf trees, a condition usually caused by low nutrient availability in the soil. Analysis of nitrogen and phosphorus levels revealed lower amounts of both nutrients in soils and of phosphorus in leaves from this site when compared to the ones containing more developed trees. This result suggests a relationship between herbivory and nutrient availability in the plants.     

Polychaeta “Sedentaria” of Terra Nova Bay (Ross Sea,Antarctica): Capitellidae to Serpulidae

Capitellidae, Maldanidae, Trichobranchidae, Terebllidae, Sabellidae, Serpulidae and Spirorbidae found in Terra Nova Bay (Ross Sea, Antarctica) have been studied. Thirty-one species have been identified, one of which, Praxillella praetermissa antantica is a new subspecies. About 75% of the species are endemic to Antarctica or sub-Antarctica. The geographic distribution of some species has been extended.     

Particulate matter composition and bacterial distribution in Terra Nova Bay (Antarctica) during summer 1989–1990

Spatial distributions of particulate organic matter (POM) and microbes were investigated during the summer of 1989–1990 in the coastal waters of Terra Nova Bay (Antarctica). The elemental (organic carbon and nitrogen) and biochemical (lipids, proteins, carbohydrates, DNA and RNA) composition of organic matter was related to bacterioplankton abundance, and pico-phytoplankton density. The ATP concentrations were also measured to gather information about the relationships between particulate matter composition and microbial distribution in Antarctic waters. Total seston was characterized by little spatial variation and was unrelated to the distance from the coast. Suspended particulate matter included some terrestrial components but was mostly composed of autochthonous material. POM was characterized by a uniform distribution and homogeneous composition (mostly of phytoplanktonic origin), and was associated with a relatively scarce microbial community characterized at the surface by high picophytoplankton density. The increase with depth of the living carbon fraction suggested an increase in the microheterotrophic community in the deeper water layers. A significant positive relationship between total bacterioplankton density, and carbohydrate and RNA concentrations was found. Similar significant relationships between pico-phytoplankton abundance and lipids, proteins, carbohydrates and nucleic acids were observed. On the basis of the close coupling found between microbiological and chemical compartments, it seems that, in Terra Nova Bay, bacterial distribution depends on suspended matter and in particular to the labile fraction of the organic detritus.     

Reproductive biology of anadromous arctic char,Salvelinus alpinus (L.)? in the Cumberland Sound area of Baffin Island

The ovaries of anadromous arctic char, Salvelinus alpinus (L.), captured during 1973 from four high arctic rivers on Baffin Island started to increase in weight early in July and were at their heaviest in mid-September just before spawning. At this time, 40 cm (615 g) char from two rivers contained ovaries weighing 17.0 g (dry) which differed significantly from the 22.5 g gonads of comparable char from the other two areas. Gonadal development in male fish began in June and the diameter of testes at full maturity (3.0–4.0 cm) was similar regardless of river system. Fecundity of comparable fish varied significantly among the rivers with char 40 cm in length containing 1400–2400 eggs while the corresponding values for 60 cm (i.e. 2050 g) char ranged from 4000–5500. The diameter of both immature and mature eggs was similar regardless of system. Values for immature eggs averaged 0.64 mm in 40 cm fish and 1.60 mm in 60 cm specimens. Diameter of mature eggs, on the other hand, was considerably greater (3.2 and 4.3 mm, respectively). Maturity was first reached at age 10 (i.e. 35 cm) in both males and females and maturing fish of both sexes were not always restricted to fresh water. Redd construction occurred at a depth of one to at least 11 m at a temperature of 0.5–4.0° C. The percentage of eggs retained in the body cavity after spawning varied from 0.22–1.50 and the mortality rate of spawned eggs was extremely low.     

Controlling factors of spring–summer phytoplankton succession in Lake Taihu (Meiliang Bay,China)

The spring–summer successions of phytoplankton and crustacean zooplankton were examined weekly in Meiliang Bay of the subtropical Lake Taihu in 2004 and 2005. During the study period, the ecosystem of Meiliang Bay was characterized by (i) clearly declined nitrogen compounds (nitrate, TN, and ammonium) and slowly increased phosphorus compounds (TP and SRP), (ii) increased total phytoplankton density and rapid replacement of chlorophyta (mainly Ulothrix) by cyanobacteria (mainly Microcystis), and (iii) rapid replacement of large-sized crustaceans (Daphnia and Moina) by small-sized ones (Bosmina, Limnoithona, and Ceriodaphnia). Results from the CCA and correlation analysis indicate that the spring-summer phytoplankton succession was primarily controlled by abiotic factors. Cyanobacteria were mainly promoted by increased temperature and decreased concentrations of nitrogen compounds. The pure contribution of crustacean was low for the variation of phytoplankton suggesting a weak top-down control by crustacean zooplankton in the subtropical Lake Taihu. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users. Handling editor: L. Naselli-Flores