Spatial and temporal distribution of mesozooplankton in the Gulf of Aqaba and the northern Red Sea in February/March 1999

The distribution pattern, taxonomic composition and communitystructure of mesozooplankton was studied along a transect with10 positions between the Gulf of Aqaba and the northern RedSea. Five positions were resampled two or three times duringa cruise of RV ‘Meteor’ in February/March 1999.In spite of clear differences in the density stratificationbetween the Gulf of Aqaba and the northern Red Sea, the mesozooplanktoncomposition was very similar: Copepods were by far the mostabundant taxon, contributing 76–95% to the total community.The remainder was composed largely of ostracods, chaetognaths,appendicularians and molluscs. The mesozooplankton of the deeplymixed stations was homogeneously distributed, at all other stationsthe bulk of the mesozooplankton (>70%) was concentrated inthe mixed surface layer with peaks of calanoids, cyclopoidsand appendicularians in the vicinity of the chlorophyll a (Chla) maximum layer. Ostracods and poecilostomatoids dominatedthe layers below. Standing stocks within the total water column(550–1200 m) varied between 93 and 431 x 10³ individualsm^–2 for copepods and 5–76 x 10³ individuals m^–2for other mesozooplankton with highest numbers in the northernGulf of Aqaba, where vertical mixing was deep (400–500m) and Chl a and mesozooplankton distributions homogeneous throughoutthe water column. Towards the south, the mixed depth decreasedfrom 300 m in the central Gulf of Aqaba to 50 m in the Red Sea.Cluster analysis separated three distinct groups of stations,compounding the observed differences between the northern Gulfof Aqaba (Position I) and the other positions. The analysisalso revealed temporal differences between the February andMarch sections of the cruise, indicating the winter–springtransition. The stations sampled in March are characterisedby a higher total abundance and by a higher percentage of appendiculariansand ostracods than the stations sampled in February     

Tidal influence upon appendicularian abundance in North Inlet estuary, South Carolina

Tidal influences on appendicularian densities were observedat North Inlet, South Carolina, by sampling along a transectwhich ran from a tidal creek to a station 5 km offshore. Oikopleuradioica was the dominant species in North Inlet, while Oikopleuralongicauda and Appendicularia sicula contributed marginallyto appendicularian numbers during midsummer and fall. A strongtide-dependent density pattern was clear for inshore waters.Low-tide densities of all three species showed a dramatic increasein an offshore direction. At high tide, densities were similarbetween all stations for O. dioica, while O. longicauda andA. sicula showed a less pronounced density gradient than atlow tide. Population densities within the inlet were greateron spring tides than neap tides and tidal influences were generallyconsistent between seasons. Appendicularians enter the estuaryin densities as high as 20 072 animals m^–3, indicatingthat tidal currents may be an important mechanism for exchangeof appendicularian biomass between coastal and estuarine waters. ¹Present address: Allan Hancock Foundation, University of SouthernCalifornia, Los Angeles, CA 90007, USA.     

'St Martin's Summer': the case of an autumn phytoplankton bloom in the Gulf of Naples (Mediterranean Sea)

Phytopiankton abundance. species composition and primary productionof the Gulf of Naples were investigated during an autumn bloomin November 1985. Hydrographic data and surface phytoplanktonsamples were collected during a 3 day cruise, whereas investigationson in situ primary production and phytoplankton vertical distributionwere conducted from a second boat on three different dates.A coast-offshore gradient was recorded for most of the chemicaland biological parameters analysed. At stations closer to thecoast, which were affected by land run-off, phytoplankton populationsattained concentrations of 2.5 10⁶ cells l^–1 with amarked dominance of diatoms belonging to the genera Thalassiosiraand Chaetoceros. The most striking character of the system wasa remarkably high carbon assimilation rate (up to 1.04 g C m^–2day^–2) at stations closer to the coast. The causativemechanism for this bloom appeared to be land-derived nutrientenrichment, possibly enhanced by autumn rains, followed by aperiod of favourable meteorological conditions, which occursrecurrently in the region for a brief period around November,known locally as ‘St Martin's Summer’. We hypothesizethat a similar mechanism can stimulate phytoplankton growthmore than once every year. since high-stability penods followingmeteoro logical perturbations can occur several times in temperateregions of the northern hemisphere in autumn.     

Plankton distribution across a slope current-induced front in the southern Bay of Biscay

Relatively warm (12.50–12.75°C) and high-salinity[<35.640 practical salinity units (PSU)] water flowing eastwardwas detected at the shelf-break during a cruise carried Outin the southern Bay of Biscay in Spring 1987. The slope currentinduced the formation of a convergent front separating well-mixedoceanic waters from haline-stratified coastal waters. Very highconcentrations of dissolved oxygen (295 µmol kg^–1)and chlorophyll a(>4.5 mg m^–3) were found at the outeredge of the frontal boundary. Small autotrophic flagellatesdominated the phytoplankton community. Primary production peakedat the boundary region. Estimated phytoplankton growth ratesindicated that active growth was taking place, with lower turnovertimes integrated over the water column at the frontal station(2.5–5 days) than at coastal (1.5–2.8 days) or oceanic(1.5–3.5 days) stations. The lowest doubling times (1–2days) were calculated for surface frontal populations. Accumulationof zooplankton was also observed associated with the convergentphysical structure, although this relationship was less markedthan for phytoplankton. Copepods, mainly Paracalanus parvus,Acartia clausi and Oithona helgolandica, formed the bulk ofthe mesozooplankton biomass. Compatibility between the sizeof phytoplankton cells and copepod size spectra indicate highfood availability for these animals, particularly in the vicinityof the front. The distribution of fish eggs and fish larvaewas also coupled with the slope current-induced front. Sardinelarvae were more abundant at the coastal side of the front,whereas larval stages of blue whiting reached the highest densitiesat off-shelf stations. Larvae of lamellibranch molluscs andbryozoa were restricted to nearshore waters, as the frontalboundary prevented larval dispersion to the open ocean. Theresults presented in this paper suggest that the Iberian slopecurrent and its associated shelf-break frontal structure werecrucial in controlling phytoplankton primary production, activityof grazers, distribution of larvae of fishes and benthic invertebrates,and ultimately in determining the structure of the pelagic foodweb in the southern Bay of Biscay during the seasonal periodof vertical mixing.     

Effects of temperature and salinity on the growth of the red tide flagellates Heterocapsa circularisquama (Dinophyceae) and Chattonella verruculosa (Raphidophyceae)

Growth responses of the red tide flagellates, Heterocapsa circularisquama(Dinophyceae) and Chattonella verruculosa (Raphidophyceae),were examined with 36 different combinations of temperature(5–30°C) and salinity (10–35 PSU). Heterocapsacircularisquama did not grow at or below a temperature of 10°C.The maximum growth rate of H.circularisquama (1.3 divisionsday^–1) was obtained with a combination of 30°C and30 PSU. In contrast, C. verruculosa did not grow at 10 PSU andat temperatures of 25°C or more. The maximum growth rateof C. verruculosa (1.74 divisions day^–1) was obtainedwith a combination of 15°C and 25 PSU. A significant temperature-salinityinteraction on growth was found by factorial analysis. Basedon the physiological characteristics obtained in the presentstudy, these novel flagellates have a potential for future outbreaksof red tides in pre viously unaffected waters.     

Size-fractionated phytoplankton carboxylase activities in the Indian sector of the Southern Ocean

During the ANTARES 3 cruise in the Indian sector of the SouthernOcean in October–November 1995, the surface waters ofKerguelen Islands plume, and the surface and deeper waters (30–60m) along a transect on 62°E from 48°36'S to the iceedge (58°50'S), were sampled. The phytoplankton communitywas size-fractionated (2 µm) and cell numbers, chlorophyllbiomass and carbon assimilation, through Rubisco and ß-carboxylaseactivities, were characterized. The highest contribution of<2 µm cells to total biomass and total Rubisco activitywas reported in the waters of the Permanent Open Ocean Zone(POOZ) located between 52°S and 55°S along 62°E.In this zone, the picophytoplankton contributed from 26 to 50%of the total chlorophyll (a + b + c) with an average of 0.09± 0.02 µg Chl l^–1 for <2 µm cells.Picophytoplankton also contributed 36 to 64% of the total Rubiscoactivity, with an average of 0.80 ± 0.30 mg C mg Chla^–1 h^–1 for <2 µm cells. The picophytoplanktoncells had a higher ß-carboxylase activity than largercells >2 µm. The mixotrophic capacity of these smallcells is proposed. From sampling stations of the Kerguelen plume,a relationship was observed between the Rubisco activity perpicophytoplankton cell and apparent cell size, which variedwith the sampled water masses. Moreover, a depth-dependent photoperiodicityof Rubisco activity per cell for <2 µm phytoplanktonwas observed during the day/night cycle in the POOZ. In thenear ice zone, a physiological change in picophytoplankton cellsfavouring phosphoenolpyruvate carboxykinase (PEPCK) activitywas reported. A species succession, or an adaptation to unfavourableenvironmental conditions such as low temperature and/or availableirradiance levels, may have provoked this change. The high contributionof picophytoplankton to the total biomass, and its high CO₂fixation capacity via autotrophy and mixotrophy, emphasize thestrong regeneration of organic materials in the euphotic layerin the Southern Ocean.     

Ontogenetic vertical distribution and diel migration of the copepod Eucalanus inermis in the oxygen minimum zone off northern Chile (20-21{degrees} S)

The vertical and ontogenetic distribution, and diel verticalmigration (DVM), of Eucalanus inermis in relation to the strongvertical gradient in oxygen concentration associated with anintense oxygen minimum zone (OMZ) were studied at a coastalarea off northern Chile (20–21° S). A close relationshipbetween the abundance of the whole copepod population and lowoxygen waters was found, with most developmental stages remainingnear the base of the oxycline (30–80 m) and within theupper zone of the OMZ (30–200 m). All stages performedDVM but not at all the stations, mainly between the 30–60and 60–200 m strata; a small fraction (<20%) appearedin the surface layer (0–30 m) mostly at night. This strategyof movement would result in a better utilization of food resourcessince the strong physical and chemical gradients at the baseof the oxycline and upper OMZ boundary might serve as a siteof particle accumulation. A secondary fluorescence peak was,in fact, found at all the stations, coinciding with minimaldissolved oxygen (DO, <1 mL O₂ L^–1) at the base ofthe oxycline or in the upper OMZ boundary. The relevance ofthe biogeochemical flux involved in this diel migration patternwas assessed by calculating the potential active input of carbonand nitrogen from the upper layers into deeper the OMZ.     

Gymnodinium catenatum Graham (Dinophyceae)in Europe: a growing problem?

The microreticulate resting cyst of the potentially toxic, chain-forming,unarmoured neritic dinoflagellate Gymnodinium catenalum Graham1943. the planktonic stage of which is not known from NorthEuropean waters, is reported for the first time from recentGerman coastal sediments of the North Sea and Baltic Sea. Insandy mud sediments of the German Bight, a maximum of 8 5 livingcysts cm^–3 were found. In Kiel Bight sediments G.catenalumwas found in maximum concentrations of 17.0 living cysts cm^–3.In surface waters of the German Bight resuspended G catenatumcysts were observed at concentrations of up to 3.6 cysts l^–1.Successful germination experiments conducted with natural seawatershow that the occurrence of a vegetative form of G.catenatumin northern Europe is very likely. The present study highlightsthat cyst surveys provide an important tool for the evaluationof areas with potential toxicity problems, as they may indicatethe presence of hitherto overlooked species in the water column.     

Thalassiosira scotia, sp. nov.: observations on a phytoplankton increase in Early Austral Spring North of the Scotia Ridge

The dominant species in an early spring phytoplankton increasein characteristically antarctic waters north of South GeorgiaIsland is described as Thalassiosira scotia G. Fryx. et Hobanand compared to related species in the South Atlantic, suchas T. antarctica Comber and T. austratis Peragallo. Found ona cooperative US-Argentine cruise of the ISLAS ORCADAS 17–78,T. scotia dominated the phytoplankton in the well-mixed watercolumns of two stations more than 100 km apart. The maximumabu dance of the new species recorded in a discrete water samplewas about 315,000 cells/liter, with up to 18.4 x 10⁹ cells undera m² in the top 100 m, in spite of the fact that there was nowell-marked thennocline to aid in maintaining one water massand thus netaining the population in the euphotic zone. A fewresting spores were noted in one station. The water temperaturein the area was about 1°C, and the salinity 33.9 o/oo.     

Size-fractionated primary production studies in the vicinity of the Subtropical Front and an adjacent warm-core eddy south of Africa in austral winter

Results are presented of size-fractionated primary productionstudies conducted in the vicinity of the Subtropical Front (STF),an adjacent warm-core eddy, and in Sub-antarctic waters duringthe third South African Antarctic Marine Ecosystem Study (SAAMESIII) in austral winter (June/July) 1993. Throughout the investigation,total chlorophyll (Chl a) biomass and production were dominatedby small nano- and picophytoplankton. No distinct patterns intotal Chl a were evident. At stations (n = 7) occupied in thevicinity of the STF, total integrated biomass values rangedfrom 31 to 53 mg Chl a m^–2. In the vicinity of the eddy,integrated biomass at the eddy edge (n = 3) ranged from 24 to54 mg Chl a m^–2 and from 32 to 43 mg Chl a m^–2 inthe eddy (n = 2). At the station occupied in the Sub-antarcticwaters, total integrated biomass was 43 mg Chl a m^–2.Total daily integrated production was highest at stations occupiedin the vicinity of the STF and at the eddy edge. Here, totalintegrated production ranged from 150 to 423 mg C m^–2day^–1 and from 244 to 326mg C m^–2 day^–1, respectively.In the eddy centre, total integrated production varied between134 and 156 mg C m^–2 day^–1. At the station occupiedin the Sub-antarctic waters, the lowest integrated production(141 mg C m^–2 day^–1) during the entire survey wasrecorded. Availability of macronutrients did not appear to limittotal production. However, the low silicate concentrations duringthe survey may account for the predominance of small nano- andpicophytoplankton. Differences in production rates between theeddy edge and eddy core were related to water column stability.In contrast, at stations occupied in the vicinity of the STF,the control of phytoplankton production appears to be relatedto several processes, including water column stability and,possibly, iron availability.     

Diel variations in gut pigment content, diel vertical migration and estimates of grazing impact for copepods in the southern Benguela upwelling region in October 1987

The gut fluorescence technique was used to estimate ingestionand filtration rates of the adult female copepods Paracalanusparvus, Cenlropages brachiatus and Calanus austrails, and copepoditestages 3, 4 and 5 of C.australis in the southern Benguela upwellingregion. During the study period chlorophyll concentrations withinthe upper 20 m of the water column were high, 5 µg I^–1in mid-shelf waters and 15–30 µg I^–1 in innershelf waters. Copepod gut pigment content was low and constantduring the day then increased sharply during the first 2 h aftersunset. Gut pigment content was 2–6 times higher duringthe night compared with daytime values. Small non-migratingcopepods (Paracalanus parvus) showed the smallest diel differencein gut pigment content and large migrating copepods (Centropagesbrachiatus and Calanus australis) the largest difference. Eggproduction rates were 20 and 50% of maximum at the mid-shelfand inner shelf stations respectively, suggesting food-limitation.Comparison of ingestion rates calculated from egg productiondata with ingestion rates calculated from gut pigment data suggestedthat the copepods were feeding omnivorously at the inner shelfstations but herbivorously at the mid-shelf stations. Assumingthat all of the phytoplankton was available as food, the nearshorecopepod assemblage grazed {small tilde}1% of the standing cropeach day, and the mid-shelf assemblage grazed 5% day^–1.Because of errors and uncertainties associated with the gutfluorescence technique, the feeding impact could be underestimatedby 2–4-fold. We discuss several approaches which couldlead to more precise estimates of feeding rates. ³Present address: Marine Sciences, SUNY, Stony Brook, NY, 11794-5000,USA     

Biomass and size structure of the scyphomedusa Aurelia aurita in the northwestern Black Sea during spring and summer

The abundance, biomass and size structure of the scyphomedusa,Aurelia aurita, was measured during two research cruises tothe northwestern Black Sea (July–August 1995 and April–May1997). Average biomass of Aurelia was relatively constant (132–179g wwt m^–2) throughout the investigation period and similarto previous years. Abundance and biomass at individual stationsappeared to be unrelated to temperature and salinity when thelatter exceeded ~13. Biomass was low at coastal stations inthe plume of the Danube where depth was <20 m and salinitydropped to <11. The spring cruise (April–May) coincidedwith, or just followed the peak of strobilation. The summercruise (July–August) took place near the beginning ofplanulae larvae release. The population size structure was dominatedby small individuals in spring, while large medusae prevailedmainly in late summer. Aurelia was, on average, larger at deepwater stations during summer, suggesting that per capita foodsupply was higher further offshore. The individual body massincreased from spring through summer. Accordingly, the volume(wet wt) to length (bell diameter) relation changed significantly.If all medusae measured throughout the seasons were pooled,volume (V, in cm³) was related to length (L, in cm) accordingto V = 0.08 L^2.71, which is similar to measurements conductedin other coastal areas. In contrast to the common conjecture,we did not find inverse relations between biomasses of Aureliaand the combjelly Mnemiopsis leidyi. Preliminary feeding experimentsindicate that Aurelia may feed upon small Mnemiopsis. The significanceof indirect trophic relations and direct feeding interactionsamong the gelatinous zooplankton in the Black Sea has importantconsequences for the energy flow along the food web and, therefore,needs further study.     

The use of high-spectral-resolution radiometer data for detection of low chlorophyll concentrations in Lake Kinneret

Chlorophyll distribution in Lake Kinneret was estimated in aperiod of low chlorophyll-a concentrations (3–7 mg m^–3)using remotely sensed data. The data set included high-spectral-resolutionradiometric measurements in the range 400–750 nm, chlorophylland suspended matter concentrations, Secchi disk transparencyand vertical attenuation coefficients at 20 stations. The spectroradiometricdata were used to create the algorithms suitable for quantitativedetermination of chlorophyll content. The present paper presentsexperimental field evidence showing that fluorescence can besuccessfully used for remote monitoring of chlorophyll-a content(with an estimation error <0.5 mg m^–3) in productiveinland waters with a background of variable and relatively highsuspended matter concentration.     

Density and distribution of bacterioplankton and planktonic ciliates in the Bering Sea and North Pacific

The total number of planktonic bacteria in the upper mixed layerof the Bering Sea during the late spring-early summer periodranged between 1 and {small tilde}4 x 10⁶ ml^–1 (biomass10–40mg C m^–3). In the northern Pacific, along 47–52⁶N,the corresponding characteristics of the bacterioplankton densityin the upper mixed water layer were: total number 1–2x 10⁶ cells ml^–1 and biomass 15–46mg C m^–3Below the thermocline at 50–100 m, the density of bacterioplanktonrapidly decreased. At 300 m depth, it stabilized at 0.1–0.2x 106 cells ml^–1. The integrated biomass of bacterioplanktonin the open Bering Sea ranged between 1.2 and 3.6 g C m^–2(wet biomass 6–18 g m^–2) Its production per dayvaried from 2 to 23 mg C m^–3 days^–1 in the upper0–100 m. The numerical abundance of planktonic ciliatesin this layer was estimated to be from 3 to l0 x 10³ cells l^–1,and in the northern Pacific from 0.4 to 4.5 x 10³ l^–2.Their populations were dominated by naked forms of Strombidium,Strombilidium and Tontonia. In some shelf areas, up to 40% ofthe total ciliate population was represented by the symbioticciliate Mesodinium rubrum. The data on the integrated biomassof basic groups of planktonic microheterotrophs are also presented,and their importance in the trophic relationships in pelagiccommunities of subarctic seas is discussed.     

Midwater and epibenthic behaviors of Mysis relicta Loven: observations from the Johnson-Sea-Link II submersible in Lake Superior and from a remotely operated vehicle in northern Lake Michigan

Submersible dives provided an opportunity to observe the opossumshrimp. Mysis relicta, in Lake Superior (64°54'N, 67°09'W,depth = 280 m). Observations included probable mating, midwaterand benthic responses, and several swimming modes. While matingthe male and female were joined in a ventral to ventral positionby interlaced thoracic appendages. During the evening ascentor predawn descent mysids actively swam vertically upwards anddownwards using their thoracic appendages which beat metachronally.When escaping from the bottom, mysids thrust their abdomensdownwards and rapidly accelerate directly forwards. The midwaterresponse, significantly slower than the benthic response, wasa jerky laterally undulatory movement which propelled the animalat a 45° angle from the forward motion. In a cruising modeMysis swims with its periopods, parallel to the bottom, at approximatespeeds of 2–5 cm^–1. A remotely operated vehiclewas employed to observe mysids at close range at the sediment–waterinterface at deep-water and nearshore stations in northern LakeMichigan (44°34'N, 87°7'W, depth = 100 m, Algoma, Wisconsinharbor, depth = 20 m) during May 23–25, 1987. At the 20m inshore station mysids occurred in significant numbers duringthe day in very bright light. Mysid swimming behavior on thebottom at deep-water stations significantly fashioned the sedimentlandscape, a potentially important form of superficial bioturbation.     

Organisms associated with stimulated epipelagic bioluminescence in the Sargasso Sea and the Gulf Stream

On three cruises, vertical profiles of stimulated bioluminescencewere measured during the late evening in the upper 200 m ofthe Sargasso Sea using a submarine photometer. On one cruise,organisms were collected in a 25 µm porosity net afterpassing through the photometer where the intensity and lightcontent of their bioluminescence were recorded. Correlationsof bioluminescence and organisms suggested that the majorityof the stimulated bioluminescence produced in the Sargasso Seawas from zooplankton: crustaceans (ostracods, copepods, copepodlarvae, euphausid larvae), larvaceans and colonial radiolarians.In addition, the photosynthetic dinoflagellate Pyrocystis noctilucaappeared to produce 5–30% of the measured bioluminescenceat some stations. Other dinoflagellates, although numerous,were dim and thus produced less than a few percent of the stimulatedbioluminescent light. The subsurface peaks in the Gulf Streamand northern Sargasso Sea were due primarily to ostracods andlarvaceans. In the Anegada Passage in October, and in the northernSargasso Sea and the Gulf Stream in August, there were pronouncedsubsurface peaks in bioluminescence associated with the thermocline.In Anegada Passage and the Sargasso Sea just north of PuertoRico in October, and in the Gulf Stream in August, the subsurfacebioluminescence peak was in or slightly above the chlorophyllmaximum. However, at the Sargasso Sea stations in August, itwas 10–40 m above the depth of the chlorophyll maximum.     

Dynamics of herbivorous grazing by the heterotrophic dinoflagellate oxyrrhis marina

In a series of batch experiments in the dark the heterotrophicdinoflagellate Oxyrrhis marina grazed three phytoplankton prey(Phaeodactylun tricornutum, Isochrysis galbana and Dunaliellateriolecta) with equal efficiency. Growth rates of the dinoflagellateranged between 0.8 and 1.3 day–1 Maximum observed ingestionrates on a cell basis varied according to the size of the preyfrom about 50 cells flagellate^–1 day^–1 when D.tertiolectawas the prey to 250–350 cells fiagellate^–1 day^–1when the other species were eaten. However, when compared ona nitrogen basis, ingestion rates were independent of prey type.Both ingestion and growth ceased when prey cell concentrationsfell below a threshold concentration of about 10⁵ cells ml^–1.Maximum specific clearance rates were 0.8x10⁴0ndash;5.7x10⁴it day which is considerably lower than that found for heterotrophicdinoflagellates in oceanic waters and may explain why O.marinagenerally thrives only in productive waters. The timing of NHregeneration was linked to the C:N ratio of the prey at thestart of grazing. Regeneration efficiencies for NH₄. never exceeded7%; during the exponential phase and were 45% well into thestationary phase. These results are comparable to those obtainedwith heterotrophic flagellates and demonstrate that the bioenergeticpatterns of grazing and nutrient cycling by different protozoaare very similar. Moreover, they support the notion that toachieve 90+% nutrient regeneration in the open ocean, as iscurrently believed, the microbial food loop must consist ofmultiple feeding steps. Alternatively, nutrient regenerationefficiencies may be considerably lower than 90%.     

Seasonal and fine-scale spatial variations in egg production and triacylglycerol content of the copepod Acartia tonsa in a river-dominated estuary and its coastal plume

We measured egg production rates of the estuarine calanoid copepodAcartia tonsa in Mobile Bay, an estuary in the northern Gulfof Mexico. Two stations were sampled approximately monthly,one at the mouth of the bay and the other just beyond the mouthin the salinity front between bay and coastal waters. Over thewhole year, temperature was the most important environmentalvariable controlling egg production. Rates increased with temperatureup to 30°C and 140 eggs female^–1 day^–1. We foundno evidence of food limitation. There was no correlation betweenegg production and phytoplankton abundance, nor increased eggproduction in response to supplements of phytoplankton addedto natural food, suggesting that non-phytoplankton food wasimportant in the diet. At the highest egg production rates,the amount of the storage lipid triacylglycerol (TAG) in adultfemales was greatly diminished, to <50 ng female^–1.This suggests that lipids in the diet can be very tightly coupledto egg production. Both egg production and TAG content of femalesshowed significant variability on spatial scales of 3–15km, especially in relation to the salinity front separat ingwater outwelling from the bay from open coastal water. For organismsthat are using copepods and their eggs as food, this variabilitywould result in a heterogeneous food environment, both in termsof the abundance of food and its nutritional content.     

Productivity of picoplankton compared with that of larger phytoplankton in the subarctic region

We determined the productivity (µg C µg^–1Chi a h^–1) of size-fractionated phytoplankton in the northernNorth Pacific and the Bering Sea in summer and winter. Picoplankton(<2 µm) were more productive than larger sized phytoplankton(2–10 and 10–200 µm) in the subtropical region,where the in situ temperature was >10°C; whereas picoplanktonin the subarctic region were similar in productivity or lessproductive than larger sized plankton, where the in situ temperaturewas <10°C. The result from the subtropical region inthis study agrees with previous results from tropical and subtropical waters, which indicate that phytoplankton productivitytends to decrease with increasing cell size. The result fromthe subarctic region, however, differs from previous results.We observed a positive linear regression for in situ temperatureand picoplankton productivity, but this trend was not seen inthe larger sized phytoplankton. The results show that the productivityof picoplankton is markedly influenced by in situ temperaturecompared with that of larger sized plankton. Low tem peratureappears to account largely for the observation that the productivityof picoplankton is not significantly higher than that of largersized phytoplankton in the subarctic region.     

Atlantis II Cruise: uniformity of deep copepod assemblages in the Mediterranean Sea

Studies of the community structure and biomass of deep copepodsbelow 500 m from R/V Atlantis II cruises AII49 and AII59 inMay–June 1969 and September–October 1970 denoteuniformity in deep assemblages among all major Mediterraneansubregions. Of the 65 copepod species recorded from 600–2500m, 45 were common for both Western and Eastern basins Eightof these species were dominant for all deep Mediterranean waters,comprising 77% of the deep plankton population The uniformityof deep copepod assemblages was confirmed by the Mantel testapplied to a simulated sampling procedure Only in terms of biomassdid Western and Eastern basins show appreciable regional differenceswith highest values for density and volume characterizing Westernstations ¹Died tragically at sea during the course of a cruise on December15, 1988