Surface Plankton Research Articles

Reproduction, dispersal and settlement of the bathyal ophiuroid Ophiocten gracilis in the NE Atlantic Ocean

Abstract Ophiocten gracilis is an ophiuroid found at bathyal depths in the North Atlantic Ocean. The adults show strong seasonal reproduction, with an ophiopluteus in the surface plankton. Settling postlarvae were collected in sediment traps moored at 1000 and 1400 m depth in the NE Atlantic during Julian Days 142 to 212 (May to July) in 1996. During this period, growth of postlarvae in the traps was linear and the diet consisted of phytodetritus and foraminifera. Experiments suggest that postlarvae sink at rates of up to 500 m dm1, although this may well be slower in the natural environment. The high fecundity, seasonality and high population density resulted in high fertilization success, and many of the offspring were advected outside the normal adult range, where they were able to settle but did not survive to adulthood.

Relationship between CD4 T lymphocyte levels and PPD skin test measurement in adult AIDS (HIV-infected persons) patients with pulmonary tuberculosis

A sustainable semi-intensive pond aquaculture technology including major carp species as cash-crop and small indigenous fish species (SIS) as food for the farmers' families is being optimized in Bangladesh. The inclusion of silver carp (Hypophthalmichthys molitrix), a cheap large species affordable by poor farmers, is now being considered. As part of a study on the effects of this filter feeder on polycultures including the large carps rohu (Labeo rohita), catla (Catla catla) and common carp (Cyprinus carpio) and the SIS punti (Puntius sophore) and mola (Amblypharyngodon mola), an experiment was carried out to test the effects of silver carp and of each SIS species on the growth, survival and yield of the large and small fish and on pond ecology.The ecology of the ponds was dominated by changes in time, strongly related to the development of a surface plankton scum at the beginning of the culture season and weather conditions. The surface scum increased decomposition processes and decreased algal development in the water body, promoted photosynthesis and ammonium release and reduced nitrification. Over those effects, the presence of silver carp in the ponds decreased algal biomass through grazing and promoted nitrification providing and resuspending particles in the water column. These effects were also produced by mola, but were evident only in the absence of silver carp. Punti stirring on the pond bottom increased nutrient flow from the sediments into the water column and promoted nitrification, but were also evident only in the absence of silver carp.The addition of 10 silver carp over the 99 large carps stocked in the 100 m2 fishponds did not affect punti and mola reproduction in the ponds, negatively affected rohu and catla growth and yield by about 20–25% but not their survival, did not affect common carp performance, reduced punti harvested biomass by 10%, reduced mola performance by about 50%, and silver carp's own biomass increased total yield and total income in about 20% each. The addition of 250 mola or punti to the large carp polycultures did not affect the performance of any of the large carps. The decreased income from selling the more expensive large carps was more than compensated by that obtained from silver carp, which increased total income by 13–24% as compared to the corresponding treatments without silver carp. This allows the option to the farmer of selling part of the silver carp to complete the cash income that would have been obtained from large carps only if silver carp would not be stocked, and consume the rest with the family.

Young whale sharks, Rhincodon typus, feeding on a copepod bloom near La Paz, Mexico

Seven small (3.2 to 5.2 m total length) whale sharks were observed suction feeding on patches of surface plankton in the Bay of La Paz within 1 km of shore and 2 km N of the phosphate dock at San Juan de la Costa, on 1–2 November 1993. The sharks were photographed and videotaped from the boat and by snorkelers in the water. When actively feeding the shark turned its head from side to side, part of the head was lifted out of the water, and the mouth opened and closed 7 to 28 times per minute (x=17, N=13). These suction gulps were synchronized with the opening and closing of the gill slits. This feeding behavior occurred only in the patchy areas of densely cloudy water, a layer 10 to 30 cm thick at the surface containing an immense concentration of copepods, 95% of which were identified as Acartia clausi. Remoras accompanying the whale sharks also fed on the plankton bloom.

Experimental and observational studies of radiolarian physiological ecology, 6. Effects of silicate-supplemented seawater on the longevity and weight gain of spongiose radiolarians Spongaster tetras and Dictyocoryne truncatum

Radiolaria occur abundantly in surface water with low silicate concentrations (ca. 1 μM), yet they construct remarkably robust siliceous skeletons. This indicates they compete very effectively for the available silicate. To examine the effects of variation in silicate concentration on skeletal growth and vitality, two spongiose radiolarians Spongaster tetras and Dictyocoryne truncatum, collected in surface plankton tows near Barbados, West Indies, were maintained in plastic tissue culture dishes, each well of the dishes containing ca. 15 ml seawater emended with additional sodium silicate of 0 μM (control), 50 μM, 100 μM and 150 μM. Their longevity and skeletal weight gain, the latter calculated from equations relating skeletal weight to a linear dimension of the skeleton, are reported with descriptions of their living features. The addition of silicate up to 100 μM had no statistically significant effect on the weight of silicate deposited per shell for either S. tetras or D. truncatum. However, noticeable detrimental effects resulted in earlier death in both S. tetras and D. truncatum at 150 μM. Early death was more frequent in D. truncatum. Spongaster tetras that grew skeletons may survive longer when cultured in 50 μM silicate-enriched seawater compared to 150 μM enriched seawater, but not longer than those cultured in unsupplemented seawater. D. truncatum has the longest longevity in unsupplemented seawater. In addition, scanning electron microscopy of shells collected from individuals that grew in culture revealed no evidence of enhanced skeletal growth or structures with silicate enrichment of the culture medium. These data add further evidence that S. tetras and D. truncatum are capable of competing very effectively for silica in ambient seawater concentrations of approximately 1.0 μM, and also that changes in seawater silicate may not have a dramatic effect on longevity, skeletal size, or weight of some radiolarians. Thus other environmental variables, such as variations in temperature and salinity, may more likely impress a relatively more salient signal in the microfossil record. Daily mean weight gain values at the four treatments ranged from 4.3 ng to 6.3 ng in S. tetras and from 19.7 ng to 27.1 ng in D. truncatum. For the control group, mean total weight gain was 0.035 μg in S. tetras and 0.083 μg in D. truncatum. Compared to the previously published results for S. tetras, using larger glass vials, the weight gain values seem to be significantly smaller. However, estimated silicate consumption ratios with respect to the available amount in the culture vessel by S. tetras agree substantially with each other. This suggests that observed radiolarian skeletal growth in the previous and present experiments was rather substantially affected by other environmental factors, such as available micronutrients, related to the water volume used in the culture vessel.

Subsurface chlorophyll maxima in the Skagerrak-processes and plankton community structure

Subsurface chlorophyll maxima are common phenomena in both the coastal and open ocean. The main objective of this study was to clarify possible differences in the structure and function of the plankton community in subsurface chlorophyll maxima and at the surface. Sampling was performed at seven stations in the Skagerrak, northeast Atlantic, during five cruises in May and August 1992 and April, May and August 1993. Subsurface chlorophyll fluorescence maxima (FM) occurred on 25 out of 32 sampling occasions. The FMs were usually situated below the pycnocline and associated with the nutricline. The ratio of chlorophyll a to particulate carbon and the light-saturated primary production were higher for plankton at the FM than at the surface, although assimilation numbers (primary production rate: chlorophyll a) were not different from surface plankton. The light protective pigment diadinoxanthin occurred in higher concentrations relative to chlorophyll a in surface plankton than in FM plankton. Respiration was higher in the FM than at the surface. This was not related to abundance of bacteria or bacterial production since no differences between surface and FM values were detected for these parameters. FM plankton was characterized by high nutrient uptake rates, but in this study there were no significant differences compared to surface plankton. ‘New’ production was on average 25%, but up to about 50% in the western Skagerrak in spring. The average nitrogen uptake rates were dominated by the regenerated nutrients ammonium and urea, accounting for about 50 and 25%, respectively. The <3 μm size fraction contributed significantly to concentrations of total chlorophyll a, particulate carbon, and nitrogen as well as to nitrogen uptake. Its contribution was highest when total values were low. Microscopical investigations and analysis of pigments specific to algal groups showed that diatoms dominated in the FMs in spring and that peridinin-containing dinoflagellates dominated in FMs in August. Autotrophic nanoplankton was dominated by the Prymnesiophyceae contributing about 50% of total cell numbers. Colonies of Phaeocystis sp. were abundant along the NW Danish coast in April and May 1993. Autotrophic eukaryotic picoplankton occurred in cell numbers up to about 30 × 10 6 cells·dm −3 along the Swedish coast. The highest cell numbers of cyanobacteria of the Synechococcus-type, about 100 × 10 6 cells·dm −3, were found in the central Skagerrak in August and the abundance of Synechococcus was correlated with nitrogen uptake in the <3 μm size fraction.

Planktonic Dispersion of Larval Salmon-Lice,Lepeophtheirus Salmonis, Associated with Cultured Salmon,Salmo Salar, in Western Ireland

Dispersion ofLepeophtheirus salmonisKreyer 1838 (Crustacea: Caligidae) larvae from a single cage and also from a farm system was investigated in Ardmore Bay, west coast of Ireland. Surface plankton tows were taken from within a cage and also at various distances from the farm. Highest densities of larvae (maximum, 66·1 m−3) were consistently recorded within the cage. Less than 10% of the larval density recorded inside the cage was found outside at any one time, indicating a high retention of larvae within the cage throughout the sampling period. This was due to a reduction of water movement inside the cage caused by the physical barrier of the net which was fouled during the sampling period. Highest densities of larvae were consistently found in samples taken at 10 m (maximum, 4·8 m−3) from the last cage on the farm in comparison to those taken further away from it (maximum, at 1 km; 0·4 m−3). Regression analysis of the data from each of the sampling dates showed a significant inverse relationship (P=0·001) between distance and larval numbers. The models produced suggest that few louse larvae would have been recovered in samples (i.e. 100 m plankton surface tows) taken more than 2 km from the last cage on the farm. Although the ratio of copepodids to nauplii increased with distance from the farm, the densities of the copepodids did not increase.

Occurrence in coastal waters and endogenous tidal swimming rhythms of late megalopae of the shore crab Carcinus maenas:implications for onshore recruitment

Previous studies have shown that newly released zoea larvae of the shore crab Carcinus maenas (L.) exhibit ebb-phased tidal vertical migration rhythms of upward swimming associated with transport offshore in ebb tidal flows. This gives rise to the question as to how later larvae of the species return to the intertidal zone. Repeated surface plankton sampling in coastal waters revealed that megalopae, the last larval stage of the crab, swarmed in surface waters mainly during flood tides and particularly at night. It is likely that flood-phased upward swimming ensures onshore transport of the larvae. Employing an infra-red actography system, endogenous circatidal rhythms of swimming activity were detected in constant laboratory conditions in freshly collected megalopae from inshore waters. However, in such conditions, upward swimming occurred at the times of expected ebb, not flood. It is proposed that inshore flood transport of megalopae is driven primarily by exogenous factors, which result in swarming of pre-moult megalopae towards the upper intertidal zone where settlement of first stage juvenile crabs occurs. It is suggested that the ebb-phased endogenous circatidal rhythm of upward swimming is adaptive in reducing the risk of premature stranding of megalopae, permitting them to oscillate between the intertidal and near shore waters until moulting is imminent and a suitable substratum is encountered. Of megalopae collected in inshore coastal waters, and maintained in the laboratory at water temperatures close to those of the field, nearly 60% moulted in 2 d, 95% in 4 d and 100% in 7 d after collection. Since the average development time for C. maenas megalopae is reported to be 13 d, the data provide evidence that only late megalopae return to coastal areas.

Endogenous tidal rhythms of vertical migration in field collected zoea-1 larvae of the shore crab Carcinus maenas:implications for ebb tide offshore dispersal

Employing a highly sensitive infra-red light actography system, circatidal rhythms of vertical migration were recorded in first stage zoea larvae of the common shore crab Carcinus maenas (L.), freshly collected from coastal waters. The rhythms persisted in constant conditions in the laboratory for several days, ascent occurring at the times of expected ebb tides at collection sites, and descent during expected flood tides. Timing was identical in larvae sampled at different stage of spring/neap cycle and from sites where different hydrodynamic conditions prevail. These experiments, supported by repeated surface plankton samples which confirmed that zoea-1 larvae of C. maenas were most abundant at the surface during ebb tides, suggest that the vertical migration behaviour might be linked with avoidance of stranding and offshore dispersal of newly released larvae. The fact that tidal migration rhythm was exhibited by larvae collected from different sites implies that the behaviour is probably widespread for the species. So far, endogenous tidal rhythms of vertical migration in plankton have been demonstrated solely in a few estuarine forms, and have been interpreted only as estuarine retention or reinvasion mechanisms. Present results appear to be the first to demonstrate that endogenous tidal rhythms also exist in the planktonic larvae of a coastal invertebrate and suggest that these larvae may have an adaptive mechanism to avoid stranding and enhance offshore dispersal in the open sea.

Build-up and decline of summer phytoplankton biomass in the eastern Weddell Sea, Antarctica

The seasonal development and decline of phytoplankton was investigated in the eastern Weddell Sea during summer and fall 1991. During the first half of the study (15 Jan–13 Feb) in an area off Vestkapp, favourable irradiance/mixing regimes initiated net phytoplankton growth in ice-free waters on the shelf and in stretches of open water over the partially ice-covered deep ocean. Chi a concentrations in the upper water column were moderate (0.2–0.8 μg l−1), but significantly above winter values. Later in the season (16 Feb–11 March), a phytoplankton bloom with surface Chl a concentrations ranging from 1.6–2.3 μg l−1 was encountered in an area further to the east. We suggest that the upper water column must have been stratified in this region for time scales of weeks to faciliate bloom development. Bacterial biomass and productivity generally paralleled the seasonal development of the phytoplankton. Nitrate concentrations in the upper mixed layer were substantially lower than would be expected from the existing phytoplankton standing stock, suggesting that heterotrophic consumption of organic matter by bacteria and zooplankton removed a large fraction of the primary production. The shallow seasonal pycnocline was eventually eroded by the passage of a storm, resulting in a homogeneous distribution of phytoplankton biomass over the entire water column, followed by sedimentation and deposition of phytodetritus on the sea floor. After the storm induced destratification, bacterial productivity was particularly high, amounting to more than half of the primary production (range: 10%–120%) in the upper water column. Subsequently, phytoplankton biomass in the upper water column decreased to values <1 μg Chl a l−1. The combination of low incident irradiances and incessant deep mixing prevented the phytoplankton biomass to increase again. During the last week of the investigation, extensive new-ice formation was observed. A major fraction of the residual surface plankton was incorporated into new sea ice, thus terminating the pelagic growth season of the phytoplankton in the eastern Weddell Sea.

Plankton inhabiting the surface layer of the southern and southwestern lagoon of New Caledonia

In the southern and southwestern coral reef lagoon of New Caledonia and the adjacent oceanic waters, 42 neuston samples were collected from the upper surface layer (0 to 10 cm) along nine transects from the coast to the coral barrier reef and the open ocean immediately beyond the reef, in March and April 1979. There was a progressive numerical decrease in zooplankton densities from the coast to the reef and from the reef to the open sea. Generally, ∼80 to 95% of the surface plankton consisted of holoplankton and ∼5 to 20% of meroplankton. Zooplankton was very abundant in littoral bays with a marked eutrophication. In a few samples collected in very shallow waters close to coral patches, cladocerans were numerous and constituted up to 75% of the total plankton, whilst in other samples collected above greater depths, copepods made up ∼60 to 85% of the total plankton. In the coral reef lagoon of south and southwest New Caledonia, typically hyponeustonic copepods (pontellids) often comprised ∼5% of the total copepod populations.

Trophic structure of the Lower Oxford Clay

Conventional palaeontological methodology over the last one hundred years has revealed a complex and intricate food web in the Jurassic Lower Oxford Clay of central England; we are able to identify the top carnivores (pliosaurs) down to the primary producers (coccolithophoroids) within the water column. In some cases it is even possible to identify individual prey preferences for different taxa.What conventional palaeontology cannot do satisfactorily is determine the quantities of food processed through the food web, the source of the nutrients, and how much and where recycling of nutrients took place. Consequently we here combine the results of extensive fossil collecting, begun in the 1890s, with data obtained from organic geochemical analysis and isotopic analysis of Oxford Clay sediment and its preserved biota (shells and bones). Examples follow:Palaeotemperatures derived from vertebrates show that ichthyosaurs, plesiosaurs and crocodiles were calcifying in waters with temperatures in the range (190 – 220). In addition, the giant filter feeding fish Leedsichthys also yields palaeotemperatures in this range, suggesting that it was a pelagic filter feeder exploiting a rich surface plankton source.Direct evidence for tetrapod diet in the form of preserved stomach contents indicates that hookleted cephalopods formed an important food source for macrovertebrates (Martill 1986). Isotopic data indicate that belemnites (believed to have been hookleted) were living in the lower water column (T = 150). We suggest that perhaps belemnites migrated to surface waters for feeding (probably at night) where they were predated upon by marine reptiles.Duff (1978) suggested that the bivalves Bositra and Meleagrinella lived attached to seaweed rather than living directly on a dysoxic, probably soupy, sea floor. Isotopic data gives palaeotemperatures from these bivalves in the range 16-18 C, comparable with the range 15-18 C derived from the definitely benthic bivalve Gryphaea. Clearly if Meleaqrinella and Bositra lived attached to seaweed then the bottom of the Oxford Clay Sea lay within the photic zone. Organic geochemical analysis indicates high nutrient input, and this is reflected in an extremely high abundance, and diversity peak, for Boreal Jurassic nannofossils.

The plankton in Lake Nojiri

Samples of surface plankton in Lake Nojiri were collected monthly from July 1988 to October 1991.In zooplankton 26 species were found and 25 species in phytoplankton. The seasonal succession of main species was as follows.Bosmina longirostrisobserved through the year, but dicreased in winter.Diaphanosoma brachyrum, Bosminopsis deitersi, Daphnia galeata, Eodiaptomus japonicusandPolyphemus pediculus appearedfrom summer to autamn, andThermocyclops hyalinusfrom spring to summer. On the other hand, Kellicottia longispina, Polyarthra vulgarisand Keratella quadratawere found from winter to spring.Ceratium hirundinella, Melosira italics, Cyclotella comtaandFragilaria crotonensiswere obsreved through the year.Asterionella formosaappeared three season except in autumnThe prevalent species wereKeratella quadratain autumn, Ceratium hirundinellafrom spring to autumn, Dinobryon cylindricumin spring, Fragilaria crotonensisfrom autumn to early winter, Melosira italicaandAsterionella formosain winter.In this Lake, Uroglenainduced a fresh water red tide from June to July in 1989. but never appeared again.Uroglena americanaobserved twice in a year from the middle of spring to the middle of summer and from the middle of autumn to winter.

La Migration Nocturne De Eurydice Truncata Norman, 1868 (Isopoda, Cirolanidae) Au Dessus Du Plateau Continental Et De La Marge

Nightly vertical migrations of Eurydice truncata Norman in the whole water column were studied in the N.W. Mediterranean Sea, at 4 stations of the continental shelf and slope above depths of 10, 30, 70 and 1250 m. An accumulation of specimens in the surface layer occurred at dusk at all the stations. This species exhibit a hyponeustonic distribution throughout the night. The upward migration in the evening and the downward migration in the morning were very fast, only few animals were collected in the deep layers during the night. None were caught in the upper layers during diurnal catches. Series of surface plankton hauls sampled in the axis and on both sides of submarine canyons, above depths from 50 to 2000 m, show that E. truncata may perform vertical migrations that are much greater than 500 m.

Patterns of sarcodine feeding in epipelagic oceanic plankton

The range of in situ prey composition was determined in marine planktonic acanthana, foraminifera and radiolana collected by divers, and quantitatively compared with the prey available, as determined by surface plankton hauls on cruises in the Florida Current, Gulf Stream and Sargasso Sea. A relatively large percentage of the sarcodines (60% of acantharia, 48% of foraminifera and 46% of radiolana) had no detectable prey Of those which had fed on identifiable prey, there was considerable overlap between sarcodine species m the types of prey captured. Nevertheless, some partitioning of food resources was evident Foraminifera consumed greater numbers of diatoms and copepods than other prey types, radiolana consumed more untinnids and mollusc larvae, and acantharia consumed mostly tintinnids. Copepods and their naupln dominated the biomass consumed for all three groups, though mollusc larvae were significant for both acantharia and radiolana. The results of parameters univariate statistical analyses earned out on each major predator group and multivariate analysis on a species-by-speaes basis confirmed that there was evidence for some partitioning of prey resources among the major sarcodine predators. The partitioning appeared to follow pnmanly morphological rather than taxonomic cnteria, however, and may have been at least partially a mechanical effect. Introduction There are three major groups of planktonic marine sarcodines: the acantharia (class Acantharea), the foraminifera (class Granuloreticulosea, order Foraminiferida) and the radiolana (classes Phaeodarea and Polycystinea). All three groups include organisms which are fascinating and unique in a variety of ways, not the least of which is that most of the members of each group construct some form of skeleton or shell (composed of celestite, calcite and opal respectively). Indeed, the composition, structure and diversity of these skeletons has been one of the major characters studied, and their biomineralization remains one of the main focuses of research on each of these groups of organisms. In general, because of their different skeletal structures, these groups have not lent themselves well to joint studies: the CaCO3 tests of foraminifera dissolve in most preparations for radiolana, the SiO2 skeletons of which are commonly cleaned with acid. For their part, the SrSO4 spines of Acantharia dissolve in most commonly used preservatives, confounding the identification of these species. Additionally, the taxonomy of the radiolaria is notoriously difficult, there being well over a thousand species. As a result, most investigations of sarcodines have been fairly narrowly focused taxonomically, in spite of the fact that the organisms appear to be very similar in terms of their general trophic status and gross morphology. Several studies have investigated the basic trophic biology of representatives of each of the various sarcodine groups, and these studies have indicated an important and complex role for sarcodines in planktonic ecosystems. Some

Hydrographic and plankton variability in the Saronikos Gulf

Five stations in the Saronikos Gulf were studied during 1983–1984. One located in Elefsis Bay an industrial area, and the others, located at a distance where the effects of effluents were minimized. A differential discharge of untreated urban wastes and industrial effluents adds to the distinctiveness of the two parts. Various physical, chemical and biological (Chlorophyll‐a, phytoplankton, Zooplankton) factors were measured seasonally. Temporal and spatial distribution of surface temperature, salinity, nutrients (N, P, Si), chlorophyll‐a, and plankton were reported and the areas exposed to local eutrophication identified. Significant correlations between phytoplankton standing crop, chlorophyll‐a Zooplankton and various environmental parameters were demonstrated.

The Association of Vibrio parahaemolyticus Serotypes with Zooplankton and its Relationship with Bacterial Indicators of Pollution

Summary The role of Zooplankton in the seasonal distribution of Vibrio parahaemolyticus and the significance of bacterial indicators of pollution in the incidence of this halophile were examined. Most probable number procedures were employed for the enumeration of both bacterial indicators of pollution and V. parahaemolyticus in surface waters and plankton samples from the Fukuyama coastal area over a period of one year. In the Fukuyama port samples the highest counts of this bacterium occurred in the autumn although it was found in these waters throughout the period of study. In general, plankton samples were found to yield higher populations of V. parahaemolyticus than did water bodies from the same area. Serological studies revealed that the same serovar, first detected in plankton samples, appeared in the water column in either the same month or in the succeeding month. Statistical analysis revealed that the presence of this autochthonous pathogen was significantly correlated with total coliforms and faecal coliforms. Analyses of variance demonstrated that V. parahaemolyticus was distributed homogeneously in the Fukuyama port area and was found to be isolated with plankton samples. All 444 strains isolated were Kanagawa phenomenon negative.

Geographical distribution of living planktonic foraminifera (Protozoa) off the east coast of Australia.

Major water masses found off eastern Australia can be identified by their planktonic foraminiferal faunas. A total of 83 surface and oblique plankton samples from two cruises, in spring (October) and summer (January), between Hobart at 44� S. and Townsville at 18� S. yielded 27 species belonging to four distinct faunas: 'tropical', 'warm subtropical', 'cool subtropical' and 'transitional'. The tropical fauna is characterized by Globigerinoides sacculifer at an abundance greater than 42% and the co- dominance of Globigerinoides conglobatus, and is associated with Coral Sea water of equatorial origin. The subtropical fauna can be subdivided into warm and cool elements. The warm-subtropical fauna, with G. sacculifer more abundant than Globigerinoides ruber, inhabits Coral and Tasman Sea waters. The cool-subtropical fauna is a mixture of the warm subtropical and the transitional faunas. The transitional fauna is dominated by Globorotalia inflata and Globigerina bulloides in the south Tasman Sea subantarctic waters. It characterizes the South West Tasman water as defined by Rochford (1957). These water masses can be clearly separated, and the extent of mixing determined by their foraminiferal fauna. The shifts in the boundaries between the faunal zones was evident between spring and summer. The boundary between the tropical and subtropical water corresponds to the tropical convergence and the subtropical/transitional boundary is the Tasman Front. During the spring cruise, a warm core eddy was identified by its warm subtropical foraminiferal fauna surrounded by a transitional fauna to the south and cool subtropical fauna to the north. This water body was near 32� S., which is consistent with the reported positions of eddies shed by the East Australian Current. The distribution patterns of individual species are discussed.

The biology of Physematium muelleri: trophic activity

Physematium muelleri is a common component of the oceanic surface plankton in oligotrophic regions of the North Atlantic. In laboratory experiments, the symbionts in one population of this spumellarian had an average of 19 ng Chl a per radiolarian, and incorporated a mean of 2.5 mg C mg Chl a h −1. P max was 3.4 mg C mg Chl a h −1 at 23°C, and the average incorporation per radiolarian was 50 ng C h −1. Respiration measurements indicate that the organisms respired 9 nmoles O 2 h −1 at 28°C. Photosynthesis by the symbionts fixed insufficient carbon to fuel this respiration. Of the Radiolaria collected, 84% of the Caribbean samples, and 98% of the Sargasso Sea samples contained microscopic prey, but most of the prey carbon was in occasional copepods. The average radiolarian had captured 35 ng C in prey in the Sargasso Sea and 40 ng in the Caribbean.

The distribution and morphology of tintinnids (ciliate protozoans) from the coastal waters around New Zealand

Abstract Tintinnids from the surface plankton of New Zealand coastal waters are illustrated with scanning electron micrographs. Brief notes are given on their taxonomy, and their use of silica grains, diatom valves, and coccoliths in construction of the lorica is discussed. Distributional data are given for each species and these are related to the hydrological regime.

Biogeochemical processes affecting the distribution and vertical transport of hydrocarbon residues in the coastal Mediterranean

Sediments, sediment trap material, dominant surface plankton and collected fecal material were sampled concurrently with surface seawater in a coastal Mediterranean ecosystem and analyzed for non-volatile hydrocarbons and chlorinated hydrocarbons. Results showed consistent partitioning of hydrocarbon classes between dissolved and particulate phases of surface waters which appeared to be related to component solubility and particle availability. Analysis of biological materials showed the biota were important not only in packaging residues into large, fast sinking particles, but also in modifying the composition of components through metabolism and selective incorporation into body tissues and feces. Apparent sedimentation rate was calculated by analysis of 210Pb in sediment core samples and used to estimate average deposition rates of organics to the sea/sediment interface. The flux of particles through 100 m, as measured in the trap material in this sampling interval, was sufficient to balance most of the petroleum input to the sediments but accounted for only 17% of the average flux of PCBs to the sediments, and virtually none of the more soluble chlorinated hydrocarbon flux. Vertical transport via large fecal material compared to average background particles was seasonally low corresponding to a seasonal minimum in plankton biomass in late summer. Results show that hydrocarbon residues transported long distances away from input sources are highly modified, pointing to the geochemical significance of physical-chemical partitioning between seawater phases, incorporation into organisms and fecal material and biological/chemical degradation.