Chlorophyll standing crop and phytoplankton production in the western Irish Sea during 1992 and 1993

Chlorophyll standing crop and phytoplankton production werestudied in the western Irish Sea over a 21 month period during1992 and 1993. For both years, the start of the production seasonwas first observed in Dundalk Bay and occurred progressivelylater in more northerly coastal and offshore waters. Standingcrop and production exhibited marked spatial heterogeneity with12.5- to 19-fold differences in crop observed over distancesof 20–30 km. Distinct regional differences in the lengthof the production season were apparent. The longest season,6–7 months with a production of 194 g C m^–2, occurredin Dundalk Bay. The season lasted 3–4 months in the summerstratified region with a production of 140 g C m^–2. Northerly,offshore mixed waters and coastal waters of Northern Irelandsupported a short (2–3 months) season and production of194 and 140 g C m^–2, respectively. The similarity in seasonalproduction between Dundalk Bay and coastal waters of NorthernIreland, and between the summer stratified and northern mixedregions, is attributed to the intensity of production duringthe summer. Between 59 and 79% of seasonal production in thenorthern mixed region and coastal waters of Northern Irelandtook place during June and July, compared to 29–40% inDundalk Bay and the summer stratified region. Lower summer productionin the latter two may be due to nutrient limitation and thishas implications for the sensitivity of these two regions toanthropogenic nutrient enrichment.     

Copepod abundance in the western Irish Sea: relationship to physical regime, phytoplankton production and standing stock

The distinct patterns of stratification in the North Channeland stratified region of the western Irish Sea influence theseasonal abundance of phytoplankton. The 3–4 month productionseason in the stratified region was characterized by productionand biomass peaks in the spring (up to 2378 mg C m² day^–1and 178.4 mg chlorophyll m^–2) and autumn (up to 1280 mgC m^–2 day^–1 and 101.9 mg chlorophyll m^–2).Phytoplankton in the North Channel exhibited a short, late productionseason with a single summer (June/July) peak in production (4483mg Cm^–2 day^–1) and biomass (–160.6 mg chlorophyllm^–2). These differences have little influence on copepoddynamics. Both regions supported recurrent annual cycles ofcopepod abundance with similar seasonal maxima (182.8–241.810³ind. m^–2) and dominant species (Pseudocalanus elongatusand Acartia clausi). Specific rates of population increase inthe spring were 0.071 and 0.048 day¹ for the North Channel andstratified region, respectively. Increased copepod abundancein the stratified region coincided with the spring bloom, andwas significantly correlated with chlorophyll standing stock.Increased copepod abundance preceded the summer production peakin the North Channel. This increase was not correlated withchlorophyll standing crop, suggesting that a food resource otherthan phytoplankton may be responsible for the onset of copepodproduction prior to the spring bloom. Hetero-trophic microplanktonas an alternative food source, and advection of copepods fromthe stratified region, are proposed as possible explanationsfor copepod abundance increasing in advance of the summer peakin primary production.     

Growth and production of Euphausia lucens in the southern Benguela Current

The growth rate of a population of Euphausia lucens from thewest coast of South Africa was estimated from laboratory studiesand from monthly size-frequency distributions of samples collectedover a 1-year period. Laboratory studies indicated that growthrates ranged from 0.131 (larvae) to 0.047 mm day^–1 (juveniles),while size-frequency distributions suggested a growth rate of{small tilde}0.026 mm day^–1 for the adults. The mean annualbiomass from the inshore, intermediate and offshore regionsranged from 9.75 to 47.29 mg dry wt m^–3 with the highestbiomass being found in the inshore region. Calyptopis larvaewere present for most months of the year, indicating continuousrecrwtment. The relative contribution of flesh, moults and eggsto the total annual production was estimated separately forall three regions. Production due to growth (P_g) was estimatedto be 92.71–185.60 mg dry wt m^–3 year^–1, whileexuviai production (P_e) varied between 60.01 and 281.38 mg drywt m year Production of eggs (P_r) was estimated to range from5.07 to 12.39 mg dry wt m year the lowest value being obtainedin the inshore region. Moult production represented {small tilde}6times the mean biomass in each region, while the P/B ratio forflesh production varied from 3.92 to 8.91, the highest ratiobeing obtained in the offshore region. Total P/B ratios rangedfrom 10.14 to 16.01.     

The productive and optical status of the oligotrophic waters of the Southern Aegean Sea (Cretan Sea), Eastern Mediterranean

Primary production, pigment concentrations and spectral measurementsof downwelling irradiance were made at four stations in fourseasons (spring, summer, autumn, winter) during 1994 in thewaters of the South Aegean Sea (Cretan Sea), Eastern Mediterranean.Rates of production were determined using in Situ incubationtechniques and included measurements at the surface microlayer.Depth-integrated values averaged over season were 5.66 mg Cm^–2 h^–1 for primary production and the correspondingchlorophyll (Ch1) a and phaeophytin (Phaeo) a values had meansof 4.87 and 1.21 mg m^–3 respectively. The assimilationratio remained very low (mean over season: 1.19 mg C mg^–2Chl a h^–1 as did the Phaeo a/Chl a ratio (mean over season:0.24). The annual production for the area was estimated to yield24.79 g C m^–2 year^–1. Primary production and Chla estimates showed statistically significant seasonal, spatialand depth variations. The spectral values of the attenuationcoefficient Kd (     

Size-fractionated Primary Production in the South Atlantic and Atlantic Sectors of the Southern Ocean

Results are presented from size fractionated chlorophyll a (Chla) and primary production studies along a transect between Antarcticaand southern Africa during the second South African AntarcticMarine Ecosystem Study (SAAMES II), conducted in late australsummer (January to February) 1993. Total integrated Chl a alongthe transect was highest in the vicinity of the Marginal IceZone (MIZ) and Antarctic Polar Front (APF). At these stations,integrated Chl a biomass was always >25 mg Chl a m^–2and was dominated by microphytoplankton. Although nominal increasesinChl a biomass were also associated with the Subantarctic Front(SAF) and Subtropical Convergence (STC), total Chl a biomassin these regions was dominated by nanophytoplankton. Withinthe inter-frontal regions, total integrated Chl a biomass waslower, generally <25 mg Chl a m^–2, and was always dominatedby nanophytoplankton. An exception was found in the AgulhasReturn Current (ARC) where picophytoplankton dominated. Totaldaily integrated production along the transect ranged between60 and 436 mg C m^–2 day^–1. Elevated production rateswere recorded at stations occupied in the vicinity of the MIZand at all the major oceanic frontal systems. The contributionsof the various size fractions to total daily production displayedthe same spatial pattern as integrated biomass, with microphytoplanktonbeing the most important contributor in areas characterizedby elevated phytoplankton biomass. Outside these regions, nanophytoplanktondominated the total phytoplankton production. Again, an exceptionwas found in the ARC north of the STC where picophytoplanktondominated total production. There, the lowest production alongthe entire transect was recorded, with total daily integratedproduction always <90 mg C m^–2 day^–1. The increasedproduction rates recorded in the MIZ appeared to result fromincreased water column stability as indicated by a shallow mixed-layerdepth. Within the inter-frontal regions, the existence of adeep mixed layer appeared to limit phytoplankton production.Low silicate concentrations in the waters north of the APF mayalso have limited the growth of large microphytoplankton.     

Diurnal and seasonal variation in the contributions of autotrophic pico-, nano- and microplankton to the primary production of an upland lake

An investigation of the diurnal variation in productivity andcontribution to production of populations of autotrophic picoplankton(0.2–2.0 µm), nanoplankton (>2 <20 µm)and microplankton (>20 µm) was carried out at monthlyintervals, from May to October 1989, in Llyn Padarn a mesotrophicupland lake in North Wales. Maximum rates and contributionsto production of the lake by autotrophic picoplankton occurredduring mid-late summer, with the highest average daily contributionfrom picoplankton (64%) recorded in September at 4 m depth.Diurnal variation in contributions from picoplankton was pronounced,with greatest input, recorded at the end of the day, duringthe period of picoplankton dominance in mid-late summer. Maximumcontribution from picoplantkon (86% of total, 9.2 mg C m^–3h^–1) was recorded in September. Nanoplankton primary productionwas of greatest significance in June and July, although levelswere lower than for picoplankton in subsequent months. Contributionsvia nanoplankton increased with depth in the lake at this time,reaching a maximum of 78% of the total at the end of the dayat 9 m depth in early July. At this time, diurnal variationin contributions via nanoplankton was considerable, with maximumphotosynthesis generally at the end of the photoperiod at depthsof 4 and 9 m. Microplankton made the greatest impact on primaryproduction during the mixed water conditions of spring and autumn,and at these times did variation in production was less thanthose of both pico and nanoplankton during summer thermal stratification.Photosynthetic capacity was lower for picoplankton than fornanoplankton and microplankton; the highest values were 5, 33and 51 mg C (mg chl a)^–1) h^–1) for pico-, nano-and microplankton, respectively. The photosynthetic efficiencyof all three size categories of phytoplankton increased withdepth. Maximum values were similar for all phytoplankton groups,between 75 and 131 mg C (mg chl a)^–1) E^–1) m² butmean levels of photosynthetic efficiency for the 6 months werelower for picoplankton than for nano- or microplankton. Ratesof carbon fixation per cell for picoplankton spanned three ordersof magnitude, varied considerably diurnally and reached maximumvalues of 484 fg C(cell)^–1) h^–1) in the afternoonin near-surface waters in the early stages of exponential populationgrowth in July. During the population maximum of picoplanktonin August and September, maximum daily values of carbon fixationper cell, assimilation number and photosynthetic efficiencywere all recorded at the end of the day. The seasonal and diurnalpatterns of production of the three size categories of planktonicalgae in Llyn Padarn were distinct. During spring, microplankton(mainly diatoms) were the dominant primary producers. As thermalstratification developed, nanoplankton were the major contributorsto phytoplanktonic production, particularly in the deeper regionsof the euphotic zone. Picoplankton made the greatest contributionto production in August and September, exhibiting maximum inputtowards the end of the light cycle. Diatoms became the majorphotosynthetic plankton in the mixed water conditions prevalentin Uyn Padarn in October.     

Production of Oikopleura longicauda (Tunicata: Appendicularia) in Toyama Bay, southern Japan Sea

Oikopleura longicauda occurred throughout the year in ToyamaBay, southern Japan Sea, and analysis of its size compositionand maturity revealed that reproduction was continuous overtheyear. Somatic growth production (P_g) varied with season from0.03 to 103 mg carbon (C) m^–2day^–1 (annual P_g 4.5g C m^–2), and house production (P_e) from 0.11 to 266 mgC m^–2 day^–1 (annualP_e 11.3 g C m^–2). The annualP_g/B ratio was 176. Compared with production data of some predominantzooplankton species in Toyama Bay, it is suggested that despitetheir smaller biomass, appendicularians are an important secondaryproducer.     

Zooplankton research in the North Sea

Summary Water types of the North Sea with different plankton are the thermally stratified northern and central regions with a relatively nutrient rich inflow of Atlantic water, a mixed region in the southern North Sea with a poor inflow of Channel water, and turbid narrow coastal zones with inflow of nutrient rich river water. Plankton studies reveal that the primary production starts early, in February, in the southern region, but is delayed in the coastal zones by turbidity. In stratified areas the algal spring bloom is delayed by mixing towards the greater depth and usually starts with the onset of thermal stratification. The spring bloom soon declines and the algae remain on a low density level in summer, presumably due to depletion of nutrients in the euphotic zone. The coastal zones and the frontal zones between mixed and stratified water have a relatively high summer primary production.The herbivores (mainly planktonic copepodes and the tunicateOikopleura dioica) grow and increase in number when the temperature rises and food is available. There is a considerable mismatch with the algal spring bloom, which comes too early and is too short in most regions. The best coincidence occurs in the coastal zones and maybe the frontal zones. Carnivores build high biomasses in late summer and fall in the coastal regions and compete with fish larvae for food and also kill many fish larvae. The large scyphomedusae are most important in this respect.The overall yearly primary production of the North Sea is estimated to be about 100 mg C.m^–2. The estimates for herbivores and fish are 20 and 1 mg C.m^–2. Considering a growth efficiency of 20%, the herbivores must consume all algae produced. The indication of a low consumption due to bad phenological coincidence in most regions leads to the assumption, that either primary production is underestimated or there is a considerable influx of organic matter from the Atlantic Ocean. During June–July 1979 the carnivore consumption was estimated in the coastal zone of the Southern Bight to be 39 mg C.m^–2.d^–1 at a copepod production of 20 mg C.m^–2.d^–1. Consumption by fish larvae and large jellyfish (Cyanea lamarckii) was 15% and 74%, respectively.It seems clear that the productivity of the North Sea depends highly on coastal and frontal zones, where herbivores find sufficient food at optimal growth conditions. Most organic matter will at the end be consumed by invertebrate carnivores, which urge fish populations to reproduce early in spring or to recruit at remote places.     

Bacterial growth and grazing loss in contrasting areas of North and South Atlantic

Samples were collected from the top 200 m of the water columnat 50 stations during two cruises in different, near equinoctialseasons on an Atlantic transect near the 20°W meridian between50°N and 50°S. These samples were analysed to determinecharacteristics of the heterotrophic bacterial populations.Flow cytometry was used to enumerate these bacteria and determinetheir average size so as to calculate their biomass. Heterotrophicbacterial production, and the rate of grazing of these bacteriaby heterotrophic nanoplankton in the main depth layers, weredetermined using ³H thymidine and ¹⁴C leucine techniques. Thebiomass of heterotrophic nanoplankton in these layers was determinedusing a glucosaminidase assay. Five provinces were distinguishedalong the transect and characterized by average values of allmeasured parameters. The relative composition and activity ofthe microbial community in the water columns within each provincechanged little between the two cruises. Lowest heterotrophicbacterial biomass of 1–2 mg C m^–3 and productionof 0.1–0.2 mg C m^–3 day^–1 were found in thenorthern and southern Atlantic gyres, and were relatively similarin both seasons. Biomass and production were 2–4 timeshigher in the northern and southern temperate waters, and inequatorial waters, than in the gyres and tended to show moreseasonal variation. Production and biomass in the layer belowthe pycnocline were lower by 10–30% and about 50%, respectively,than values determined in the surface mixed layer, and variedless with latitude. Depth-integrated values of these two parameterswere generally of similar size in the mixed water layer andthe layer of the chlorophyll maximum and pycnocline, and tendedto vary with season. The specific growth rate of heterotrophicbacteria was in the range 0.05 to 0.12 day^–1 in the topmixed layer at all latitudes. In spite of the elevated temperatures,bacterial growth appears to be restricted by a shortage of nutrientsso that the microbial community cycles very slowly, with a turnovertime of the order of 1 week or more. The depth-integrated biomassof heterotrophic nanoplankton was generally about 100% of theheterotrophic bacterial biomass in the same water. Grazing bythese nanoplankton at the rate measured could consume all ofthe new production of heterotrophic bacteria in all waters,and they probably control the populations of both heterotrophicand phototrophic bacteria.     

Productivity of Daphnia longispina in a highly humic boreal lake

The development of the Daphnia longispina (O. F. Müller)population in a highly humic boreal lake was followed throughoutone growing season, and the amount of secondary production wasestimated in relation to primary production and available foodresources. The growth rate method was applied in the secondaryproduction measurements. Daphnia longispina did not appear inthe water column until 16 May, after which the animals werepresent throughout the growing season. The population showedthree density peaks; the first appeared in early June, and thesecond and third in mid-July and at the beginning of September,respectively. Somatic production followed a seasonal pattern,with highest production rates in midsummer. The maximum valueof 127 mg C m^–2day^–1 was recorded at the beginningof July. The total annual net production of D. longispina was7.9 g C m^–2. During most of the growing season, the primaryproductivity in the lake was well below 100 mg C m^–2 day^–1and the total annual productivity of photosynthetic algae was5.0 g C m^–2. We conclude that in this lake the zooplanktonpopulation did not rely on phytoplankton primary productionas a sole carbon source, but that most of the carbon must haveoriginated from bacterial production either directly or througha microbial loop.     

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.     

Microplankton and primary production in the Sea of Okhotsk in summer 1994

Phytoplankton composition, density, vertical distribution andprimary production were investigated in the Sea of Okhotsk andin the adjacent northern north Pacific in July–August1994, together with measurements of density and distributionof planktonic microheterotrophs: bacteria, nanoheterotrophsand ciliates. Different phases of phytoplankton seasonal successionwere encountered during the period of investigation in variousregions of this sea. Primary production measured at 144 stationswas found to be greatest (1.5–4 g C m^-2day^-1) in areasof spring-phase succession along the Sakhalin shelf and theKashevarov bank. Periodic relapses of the spring blooms of ‘heavy’diatoms during the whole growth season were recorded over thisbank. The summer phase of the phytoplankton minimum prevailedin the central and eastern parts of the sea, manifested by thedominance of nanoflagellates in terms of phytoplankton biomass.Primary production was 0.5–1 g C m^-2 day^-1. The earlyautumn phase of succession was typical of the Kurile straitarea and the adjacent north Pacific. Primary production therevaried from 0.7 to 2 g C m^-2 day^-1. The integrated phytoplanktonbiomass in the water column varied from 9–12 g m^-2 inzones supporting the summer minimum assemblage to 15–20g m^-2 in zones of early autumn recovery of phytoplankton growth,and up to 40–70 g m^-2 in areas of remnant or relapseddiatom blooms. The numerical density of bacterioplankton wasbetween 1 x 10⁶ and 3 x 10⁶ cells ml^-1 and its wet biomass wasbetween 100 and 370 mg m^-3. In deep waters it was 8–15mg m^-3. The integrated bacterioplankton biomass in the upperwater column varied from 6 to 29 g m^-2. The numerical densityof zooflagellates varied in the upper layer between 0.8 x 10⁶and 4 x 10⁶ l^-1 and their biomass was between 20 and 50 mg m^-3.In deep waters they were still present at a density of 0.05x 10⁶ to 0.2 x 10⁶ cells l^-1. The biomass of planktonic ciliatesvaried between stations from 20 to 100 mg m^-3. The joint biomassof planktonic protozoa in the water column was between 3 and12 g m^-3 at most of the stations.     

Algal production in the west-central North Sea

In 1976, 13 cruises were used for a plankton survey of an areaapproximately 300 x 150 km off the north-east coast of Englandfrom March to November. Results are presented of integratedzooplankton samples, surface measured nitrate, phosphate, silicateand chlorophyll, as well as other environmental characteristics.They show that the spring bloom started from near the DoggerBank and spread to most of the area by the end of April; thisdeclined and a nearshore production zone was seen in summer.This eventually disappeared and an offshore autumnal peak wasfound. The data are interpreted with use of a vertically integratedtwo-dimensional model. The model adequately explains the amplitudeand timing of the two-dimensional distributions of algal standingstock for the first half of the year but provides a poor representationafter that. It is inferred that annual primary production inthis region is low, about 40 g C.m^–2. This is due to lowoverwinter levels of nutrients and a shallow mixed layer depthof water. Pelagic fish are considered to have an ecologicalefficiency of 7–10% and demersal fish of about 4%. Thelatter figure may be due to underexploitation of demersal biomass.     

The contribution of ammonia excreted by zooplankton to phytoplankton production in Narragansett Bay

Ammonia excreted by mixed zooplankton populations over an annual(1972–1973) cycle in Narragansett Bay varied from 0.04to 3.21 µg at NH₃-N dry wt^–1 day^–1, exclusiveof two exceptional rates measured one year apart: 11.74 and18.39 µg at NH³-N mg dry wt^–1 day^–1. Grossphytoplankton production integrated over the year (1972–1973)averaged 151 mg C m^–3 day^–1 for an 8 m water column;peaks of 332 and 905 mg C m^–3 day^–1 occurred duringthe winter-spring and summer blooms, respectively. Excretedammonia, integrated seasonally and annually, contributed only0.2% and 4.9% of the nitrogen required for observed gross productionduring the winter-spring and summer blooms, respectively, and4.4% annually. However, excreted ammonia may be an importantsource of the nitrogen required by Skeletonema costatum, thedominant diatom in Narragansett Bay, during the post-bloom periodwhen 186% of the nitrogen required for its net production wasmet by ammonia excretion. A combination of zooplankton ammoniaexcretion and benthic ammonia flux contributed 22% of the nitrogenrequired for the annual gross production (440 g C m^–2)while 51% of the nitrogen required for the net production ofSkeletonema was accounted for by regenerated nitrogen. ¹This research was supported by NSF grant GA 31319X awardedto Dr.T.J.Smayda.     

Growth of Ceratium hirundinella in a subtropical Australian reservoir: the role of vertical migration

A study into the photophysiology, growth and migration of Ceratiumhirundinella in Chaffey Reservoir in subtropical northern NewSouth Wales, Australia, revealed that a proportion of cellsformed subsurface accumulations at depths that optimized lightintensity (212–552 µmol photons m^–2 s^–1)for photosynthesis and cell growth. At high incident irradiance,Ceratium migrated downwards from the near-surface waters, avoidinghigh-light-induced, slow-recovering non-photochemical quenchingof photosystem II. Overnight deepening of the surface mixedlayer by convective cooling produced homogeneous distributionsof Ceratium with a significant proportion of the populationbelow the depth where light saturation of photosynthesis occurred.Ceratium migrated towards the surface from suboptimal lightintensities, at a velocity of 1.6–2.7 x 10^–4 m s^–1.Subsurface accumulations occurred under a variety of turbulenceintensities; however, accumulation was significantly reducedwhen the turbulent velocity scale in the mixed layer was >5x 10^–3 m s^–1, beyond which turbulent diffusion dominatedadvection by swimming. The formation of subsurface accumulationswith increased computed water column integral photosynthesisby 35% compared to a uniform cell distribution.     

Zooplankton in the Vasikkalampi pond, a warm water effluent recipient in Central Finland

Seasonal and vertical fluctuations of zooplankton species composition,biomass, and production were monitored by weekly sampling duringa two year period in one eutrophic pond in Central Finland.The study was one part of a more comprehensive study programto investigate the effects of warm water effluents from onesmall thermal power plant (35 MW) on the pond ecosystem. Becauseof the circulation of the pond water through the pumps in thepower plant the crustacean populations were very sparse in planktonduring the seasons the power plant was in operation (late Augustto May). During that time rotifers were dominant and some speciesreached very high densities (e.g., Keratella cochlearis s.l.ca. 15 000 ind. l^–1 in sping). In summer months Asplanchnapriodonta, Ceriodaphnia quadrangula, Bosmina longirostris, Mesocyclopsleuckarti and Thermocyclops oithonoides were dominant. A totalof 96 planktonic and meroplanktonic taxa were identified (26ciliates, 46 rotifers, 21 cladocerans and 3 copepods). The dryweight biomass of total zooplankton was 10 mg m^–3 in wintermonths, 10–100 mg m^–3 in spring and 300–1000mg m^–3 in summer. The total yearly production of zooplanktonwas 8552 mg dry wt m^–3 a^–1 in 1979 and 8440 mg drywt m^–3 a^–1 in 1980, from which the proportion ofrotifers was 33–39%, cladocerans 52–58% and copepods8.6 –9.4%. The winter production was 0.2–0.5% ofthe total yearly production, that of spring and autumn togetherwas 8.1–10.4% and the remainder (89–91%) was summerproduction.     

Size-fractionated biomass, photosynthesis and dark CO2 fixation in a tropical oceanic environment

This study examines the spatial distribution and size structureof phytoplankton biomass and productivity in relation to thevertical structrure of the Andaman Sea (northeastern IndianOcean). This region was characterized by low concentrationsof nutrients and high levels of insolation. Nitrogen availabilityappeared to control overall productivity with nitrate-based‘new’ production accounting for 8–24% of thetotal primary production. Euphotic column chlorophyll (chl a)averaged 52.5 mg m^–2 of which a major portion was locatedas a subsurface chl a maximum (SCM) at     

Age, Fluence Rate, and Anthocyanin Production in Zea mays Seedlings

Increase in fluence rates of white light over the range of 5to 80 µmol m^–2 s^–1 brought about a correspondingincrease in amounts of anthocyanin production in shoots of Zeamays L. seedlings. Roots also exhibited a similar relationshipbetween increased fluence rate and increased anthocyanin productionover the range of 5 to 40 µmol m^–2 s^–1 whereasfluence rates above 40 µmol m^–2 s^–1 broughtabout decreases in anthocyanin production. Rates of productionand amounts of accumulation of anthocyanin in both shoots androots were found to vary with the age of the seedlings at thetime of exposure to light. Age, fluence rates, anthocyanin, seedlings, Zea mays     

Particulate and dissolved phytoplankton production of the Patos Lagoon estuary, southern Brazil: comparison of methods and influencing factors

Uptake rates of ¹⁴C (filtration and the acidification-bubblingmethod—ABM) were measured weekly in a shallow region ofthe Patos Lagoon estuary (3207'S, 5206'W) between March 1989and March 1990. Phytoplankton production varied seasonally,the lowest values occurring in the austral winter (June–August1989) and the highest rates during spring and summer (March1989; September 1989–March 1990). Particulate carbon productionvaried between 0.65 and 70.6 mg C m^–3 h^–1 and wasmostly associated with organisms <20 µm (mean = 73.4%).Dissolved organic carbon (DOC) released by phytoplankton variedbetween 0.1 and 89.3 mg C m^–3 h^–1 representing