Seston composition of the bottom waters of Great Lameshur Bay,St. John,US Virgin Islands

Seston composition [particulate organic carbon (POC), particulate nitrogen (PN), phyto- and microzooplankton numbers and biomass] was investigated in the bottom waters of Great Lameshur Bay, St. John, Virgin Islands (USA), in October, 1970 during Tektite II Mission 17–50. Mean values of 67.4 g POC · I^-1 and 7.2 g PN · I^-1 were determined. A mean phytoplankton carbon content of 42.2 g · I^-1 and zooplankton carbon content of 5.5 g · I^-1 were calculated from counts. The phytoplankton consisted mainly of dinoflagellates 71.2% phytoplankton carbon. Copepods were the dominant zooplankters (61.8% zooplankton carbon), followed by larvaceans (30.9% zooplankton carbon). Organic carbon content of counted zooplankton faecal pellets ranged between 0.4 and 1.6 g · I^-1, and amounted probably to about 15% of the total zooplankton carbon value. Plankton and detritus components as possible food for coral-reef animals are discussed. The ratio carbon: nitrogen of suspended particles is compared to that of sedimented matter.     

Cadmium accumulation,LC50 and oxygen consumption in the tropical marine amphipod Elasmopus rapax

Adult Elasmopus rapax, collected from the eastern coast of Venezuela in 1990, were exposed to seawater containing various CdCl₂ concentrations ranging from 0.25 to 5.5 mol l^-1. The 48-h and 96-h LC₅₀ values obtained were 4.0 and 1.6 mol Cd l^-1, respectively. In amphipods exposed to 1 mol Cd l^-1 for up to 240 h, the apparent rate of cadmium uptake was higher in dead animals (most of which had molted during the preceding 24 to 48 h) than in those which survived throughout the treatments without molting. Thus, whole-body cadmium content reached 1.74 mol g^-1 dry weight (dw) in the former and only 0.85 mol g^-1 dw in the latter; the higher body Cd-load may have caused the increased mortality observed in molters. On exposure to cadmium levels above 0.5 mol l^-1 the oxygen consumption rate of non-molters decreased from 2.2 to about 1.5 ml O₂ g^-1 dw h^-1 over the first 24 h, remaining unchanged thereafter. The results place E. rapax among the most sensitive marine organisms yet studied concerning cadmium toxicity, and emphasize the usefulness of the Amphipoda as bioindicators and research tools for bioassays.     

Physiological ecology of picoplankton in the North Sea

The distribution of cyanobacteria in the surface waters of the North Sea was measured during July 1987. Numbers of cyanobacteria ranged from 2.5x10⁶ to 1.7x10⁸ cells 1^-1. In the majority of stations, cyanobacterial numbers were highest in the near-surface water and a subsurface maximum was found at only one station. The distribution of ¹⁴C among the end-products of photosynthesis was determined for picoplankton (<1 m) and other phytoplankton >1 m throughout the North Sea. The majority of label was found in the protein fraction of both picoplankton and >1 m phytoplankton; incorporation into lipids and polysaccharides plus nucleic acids was much lower. We interpret the large incorporation into protein to be a consequence of nutrient limitation of these natural assemblages. Photosynthetic parameters of the two size fractions were also determined. Assimilation number (P _m ^B ) and initial slope were greater for the picoplankton fraction than for phytoplankton >1 m but there was no evidence of significant photoinhibition of either fraction at irradiances up to 1 000 E m^-2 s^-1.     

Effect of heavy metals (Zn,Hg, Cu,Cd, Pb,Ni) on the length growth of Mytilus edulis

The shortterm (10–22 d) effect of Zn, Hg, Cu, Cd, Pb, and Ni on the length growth of Mytilus edulis is studied. Significant reductions of growth rate was found at 0.3 g Hgl^-1, 3 g Cul^-1, 10 g Znl^-1, and 10 g Cdl^-1 added to the local sea water, while concentrations of up to 200 gl^-1 of Pb and Ni had no effect on the growth. With exposure to Cu and Zn, there was a linear reduction in growth rate with increasing metal concentration up to about 6 g Cul^-1 and 100 g Znl^-1. Above these levels, growth stopped with Cu, while with Zn it was stabilized at about 20% of control growth. When Hg and Cd were added, a curvilinear relationship between growth and metal concentration is indicated. With Hg, growth rate is nearly zero above 3–4 g Hgl^-1, while the growth rate was 50% of control after 10 d of exposure to 100 g Cdl^-1. At 2 g Cdl^-1 there was a significant stimulation of length increase. Observed EC₅₀-values for growth were 0.3–0.4 g Hgl^-1, 3–4 g Cul^-1, 60 g Znl^-1, and 100 g Cdl^-1.     

Seasonal photosynthetic characteristics of Ascoseira mirabilis (Ascoseirales,Phaeophyceae) from King George Island,Antarctica

Monthly variation in photosynthesis, dark respiration, chlorophyll a content and carbon: nitrogen (C:N) ratios in different lamina sections of adult plants of Ascoseira mirabilis Skottsberg from King George Island, Antarctica, was investigated between September 1993 and February 1994. Light saturated net photosynthesis (P _max) showed maximum values in September (12 to 25 mol O₂ g^-1 fr wt h^-1), and decreased towards the summer to values ranging between 2.0 and 5.0 mol O₂ g^-1. In the distal section, however, a second optimum occurred in December (25 mol O₂ g^-1 fr wt h^-1). Dark respiration rates were also highest in October and November and decreased strongly in December to February (6.0 and 1.0 mol O₂ g^-1 fr wt h^-1, respectively). Gross photosynthesis exhibited high values between September and December. Concomitant with the seasonal decrease of photosynthetic efficiency () from mean values of 1.2 mol O₂ g^-1 fr wt h^-1 (mol photons cm^-2 s^-1)^-1 in September to 0.3 mol O₂ g^-1 fr wt h^-1 (mol photons cm^-2 s^-1)^-1 in January, the initial light saturating point (I _k) gradually increased from 19 to 60 mol photons m^-2 s^-1. Likewise C:N ratios were low in spring (12 to 13) and increased in summer (20). In general, the photosynthetic parameters P _max, gross photosynthesis, and Chl a concentrations were significantly higher in the distal section of the thallus. In contrast, C:N ratios were lower in the distal section of the lamina. The results show that photosynthesis obviously strongly supports growth of the alga in late winter to spring, as it does in some morphologically related brown algae from temperate and polar regions. The question whether growth is additionally powered     

Interactions of inorganic nitrogen in the uptake and assimilation by marine phytoplankton

The effect of ambient ammonium concentration on the nitrate uptake rate of marine phytoplankton was investigated. These studies consisted of laboratory experiments using unialgal species and field experiments using natural phytoplankton communities. In laboratory experiments, ammonium suppressed the uptake rates of nitrate and nitrite. Approximately 30 min were required for ammonium to exhibit its fully inhibitory effect on nitrate uptake. At high ammonium concentration (>3 g-at/l), a residual nitrate uptake rate of approximately 0.006 h^-1 was observed. When the ambient ammonium concentration was reduced to a value less than 1 g-at/l, the suppressed nitrate uptake rate subsequently attained a value comparable to that observed before the addition of ammonium. A range of 25 to 60% reduction in the nitrate uptake rate of natural phytoplankton communities was observed at ambient ammonium concentrations of 1.0 g-at/l. A mechanism is proposed for the suppression of nitrate uptake rate by ammonium through feedback control of the nitrate permease system and/or the nitrate reductase enzyme system. The feedback control is postulated to be regulated by the level of total amino acids in the cell.Contribution No. 936 from the Department of Oceanography, University of Washington, Seattle, Washington 98195, USA. This paper represents a portion of a dissertation submitted to the Department of Oceanography, University of Washington, Seattle, in partial fulfillment of the requirements for the Ph.D. degree.     

Relationship between phytoplankton cell size and the rate of orthophosphate uptake: in situ observations of an estuarine population

Orthophosphate uptake by a natural estuarine phytoplankton population was estimated using two methods: (1) ³²P uptake experiments in which filters of different pore sizes were used to separate plankton size-fractions; (2) ³³P autoradiography of phytoplankton cells. Results of the first method showed that plankton cells larger than 5 m were responsible for 2% of the total orthophosphate uptake rate. 98% of the total uptake rate occurred in plankton composed mostly of bacteria, which passed the 5 m screen and were retained by the 0.45 m pore-size filter. There was no orthophosphate absorption by particulates in a biologically inhibited control containing iodoacetic acid. Orthophosphate uptake rates of individual phytoplankton species were obtained using ³³P autoradiography. The sum of these individual rates was very close to the estimated rate of uptake by particulates larger than 5 m in the ³²P labelling experiment. Generally, smaller cells were found to have a faster uptake rate per m³ biomass than larger cells. Although the nannoplankton constituted only about 21% of the total algal biomass, the rate of phosphate uptake by the nannoplankton was 75% of the total phytoplankton uptake rate. Results of the plankton autoradiography showed that the phosphate uptake rate per unit biomass is a power function of the surface: volume ratio of a cell; the relationship is expressed by the equation Y=2x10^-11 X ^1.7, where Y is gP m^-3 h^-1 and X is the surface: volume ratio. These results lend support to the hypothesis that smaller cells have a competitive advantage by having faster nutrient uptake rates.     

Lead in New Orleans soils: New images of an urban environment

This paper describes a survey of lead in soil and computer generated maps that have been derived for New Orleans, Louisiana. The soil survey included streetside, houseside and open space samples. Because the survey covered every census tract in the metropolitan area it was possible to construct a computer-generated map of the distribution of lead dust in the soils of the urban environment. The data base consists of coordinates, site characteristics and lead analytical results of 3,704 soil samples. The resulting graphics show peaks of lead ranging from 600–1,200 g per g in the streetside soil of the inner-city and a steeply declining slope to the suburban areas of the city where the lead content of streetside soils is less than 75 g/g. In the inner-city, the amount of lead in soils found near building foundations is 10 to 20 times higher than the soils adjacent to streets where the median lead content of soils is over 300 g g^–1. In areas surrounding the city core (mid-city), the amount of lead next to the foundation and adjacent to the street are equivalent with medians of 110 g g^–1. In suburban locations, the median lead content of soil along streetsides is 86 g g^–1. Soils adjacent to surburban foundations has a median Pb content of 50 g g^–1. The lowest median lead content in soil is found in open spaces, ranging from 212 to 40 to 28 g g^–1, respectively, for the inner-city, mid-city, and suburbs. These observations are consistent with the production and consumer use of lead-based paint and leaded-fuels within the modern city.     

Effects of light intensity on nitrate and nitrite uptake and excretion by Chaetoceros curvisetus

Michaelis-Menten uptake kinetics were observed at all light intensities. With constant illumination, the V_max and K₁ in nitrate uptake over the natural light intensity range of 0 to 2000 E were 0.343 g-at NO₃–N(g)^-1 at protein-N h^-1 and 26 E, respectively. Nitrate uptake was inhibited at higher light intensities. The K_s for nitrate uptake did not vary as a function of light intensity remaining relatively constant at 0.62 g-at NO₃–N 1^-1. With intermittent illumination, the V_mzx for light intensity in nitrate uptake over a light intensity range of 0 to 5000 E was 0.341 g-at NO₃–N(g)^-1-at protein-N h^-1. No inhibition of nitrate uptake was observed at higher than natural light intensities. Chaetoceros curvisetus will probably never experience light inhibition of nitrate uptake under natural conditions.     

Lead and cadmium in urban allotment and garden soils and vegetables in the United Kingdom

In order to assess the intake of lead and cadmium by consumers of home grown vegetables in urban areas, replicated experimental plots of uniform size, comprising summer and winter crops, were established in 94 gardens and allotments in nine towns and cities in England.The geometric mean lead and cadmium concentrations for the soils (n = 94) were 217 g g^–1 (ranging from 27 to 1,676 g g^–1) and 0.53 g g^–1 (<0.2–5.9 g g^–1), respectively. Compared with agricultural soils, the garden and allotment soils contained elevated levels of lead but not cadmium.Lead concentrations in the vegetables ranged from <0.25 g g^–1 to 16.7 g g^–1 dry weight and cadmium concentrations ranged from <0.025 g g^–1 to 10.4 g g^–1 dry weight. Lead concentrations were higher than reported background levels, although <1% exceeded the statutory limit for saleable food in the UK (1 g g^–1 fresh weight). Cadmium concentrations were generally similar to background levels.     

Mytilus edulis planulatus: an “integrator” of cadmium pollution?

Mussels, Mytilus edulis planulatus, were collected from Port Phillip Bay, Victoria, Australia, in February 1984, to test the assumption that they are integrators of cadmium pollution. Groups of mussels were subjected to the same average dose of cadmium (21 g l^-1), administered according to different dosing regimes over 4 wk (Regimes 1, 2, 3, 5); other groups received twice the average dose (42 g l^-1) in half the time (Regime 4). During each regime, the mussels were exposed to the different cadmium concentrations for one week at each concentration. Nominally, the regimes were: (1) 36 g (Wk 1) to 26 g (Wk 2) to 16 g (Wk 3) to 6 g (Wk 4) Cd l^-1; (2) 6 to 16 to 26 to 36 g Cd l^-1; (3) 21 to 21 to 21 to 21 g Cd l^-1; (4) 42 to 42 g Cd l^-1; (5) 42 to 42 g Cd l^-1 to background (<0.5 g) to background. Differences in cadmium accumulation by mussels from Regimes 1 and 4 were not statistically significant, nor were differences in accumulation between mussels from Regimes 2 and 3. However, mussels from Regimes 1 and 4 had accumulated significantly more cadmium than had mussels from Regimes 2 and 3. Accumulation by mussels from Regime 5 was not significantly different from that by mussels from any of the other regimes. These results suggest that, at least for cadmium, the assumption that mussels are integrators of pollution should be treated with caution. They also have implications with regard to the quantitative biological monitoring of pollution. For example, even in a carefully controlled monitoring program, using mussels of standard size and condition, significant differences in cadmium content between mussels need not indicate exposure to different levels of contamination. Rather, these differences could reflect differences in the regime by which the contamination was received.     

Light requirements for growth of six shade-acclimated Mediterranean macroalgae

Six mediterranean macroalgae were cultivated for more than 2 yr under shade culture conditions, after which light requirements for growth were investigated at 16±2°C. The saturation light levels for growth in the logarithmic phase were related to the bathymetric distribution of the algae on the shore. The eulittoral to supralittoral red alga Bangia atropurpurea was saturated at a photon fluence rate of 71 mol photons m^-2 s^-1, the upper sublittoral to eulittoral brown algae Scytosiphon lomentaria, Colpomenia peregrina and Kuckuckia spinosa and the sublittoral brown alga Stictyosiphon soriferus at 39 to 71 mol photons m^-2 s^-1, and the deep-water alga Choristocarpus tenellus at 19 mol photons m^-2 s^-1. The minimum light requirements for growth of B. atropurpurea and C. tenellus were determined by observing length increase for 56 d under limiting light conditions. The compensation and minimum irradiances required for growth of B. atropurpurea were 0.5 and 1 mol photons m^-2 s^-1 respectively. The corresponding values for C. tenellus were 0.15 to 0.28 and 0.5 mol photons m^-2 s^-1 respectively. C. tenellus was the siowest-growing species tested at saturating light conditions, but it grew faster than B. atropurpurea at 1 mol photons m^-2 s^-1. Both B. atropurpurea and C. tenellus were able to survive 56 d in darkness, but only the latter grew under darkness in the first 14 d.     

Effects of nitrogen and phosphorus enrichement on in vivo symbiotic zooxanthellae of Pocillopora damicornis

The reef coral Pocillopora damicornis (Linnaeus) was grown for 8 wk in four nutrient treatments: control, consisting of ambient, unfiltered Kaneohe Bay seawater [dissolved inorganic nitrogen (DIN, 1.0 M) and dissolved inorganic phosphate (DIP, 0.3 M)]; nitrogen enrichment (15 M DIN as ammonium); phosphorus enrichment (1.2 M DIP as inorganic phosphate); and 15 M DIN+1.2 M DIP. Analyses of zooxanthellae for C, N, P and chlorophyll a after the 8 wk experiment indicated that DIN enrichment increased the cellular chlorophyll a and excess nitrogen fraction of the algae, but did not affect C cell^-1. DIP enrichment decreased both C and P cell^-1, but the decrease was proportionally less for C cell^-1. the response of cellular P to both DIN and DIP enrichment appeared to be in the same direction and could not be explained as a primary effect of external nutrient enrichment. The observed response of cellular P might be a consequence of in situ CO₂ limitation. DIN enrichment could increase the CO₂ (aq) demand by increasing the net production per unit area. DIP enrichment could slow down calcification, thus decreasing the availability of CO₂ (aq) in the coral tissue.Hawaii Institute of Marine Biology Contribution No. 920     

The functions of octopine dehydrogenase and D-lactate dehydrogenase in the pedal retractor muscle of thedog whelk Nassarius coronatus (Gastropoda: Nassariidae)

The pedal retractor muscle of Nassarius coronatus, unlike most mollusc muscles, contains high activities of both octopine dehydrogenase (159 IU g^-1 wet wt muscle) and D-lactate dehydrogenase (40 IU g^-1 wet wt muscle). Pedal retractor muscles show accumulation of octopine (increase of 4.7 mol g^-1 wet wt muscle), and a fall in arginine phosphate concentration (decrease of 4.1 mol g^-1 wet wt musscle) after exercise. During recovery from exercise, octopine returns to resting levels after about 120 min, D-lactate accumulates (5.1 mol g^-1 wet wt muscle), and arginine phosphate returns to resting levels within 30 min. D-lactate (2.0 mol g^-1 wet wt muscle) accumulates during long-term exposure to air. The results show that octopine dehydrogenase and D-lactate dehydrogenase can function to catalyze the terminal step of glycolysis during muscle anoxia associated with these different physiological states.     

Concentrations of Mn,Fe, Cu,Zn and Cd in the mesopelagic decapod Systellaspis debilis from the East Atlantic Ocean

Specimens of the oceanic decapod Systellaspis debilis were collected from six sites in the East Atlantic Ocean between 1970 and 1984, and were analysed for Mn, Fe, Cu, Zn and Cd. The data confirm that there are small but significant differences in mean metal concentrations from some sites which showed no obvious pattern in relation to geographic location of the samples. As a result, ranges of site means are quoted as baseline levels for each metal (g g^-1 dry wt): 2.3 to 2.9 g Mn g^-1, 31.2 to 77.8 g Fe g^-1, 25.9 to 83.4 g Cu g^-1, 41.9 to 92.9 gZn g^-1, 11.1 to 31.8 g Cd g^-1. The concentration of cadmium in S. debilis from all sites was raised relative to cadmium concentrations reported for coastal decapods, perhaps as a result of dietary enrichment. Metal accumulation may provide useful information for understanding the complex feeding behaviour of many oceanic animals.     

Fractionated phytoplankton primary production,exudate release and bacterial production in a Baltic eutrophication gradient

The distribution of phytoplankton primary production into four size fractions (>10 m, 10-3 m, 3-0.2 m and <0.2 m), the utilization of algal exudates by bacteria and the bacterial production were studied in a eutrophication gradient in the northern Baltic proper. The polluted area exhibits substantially increased nutrient, especially nitrogen, levels while only minor differences occur in salinity and temperature regimes. Total primary production was 160 g C · m^-2 · yr^-1 at the control station and about 275 g C · m^-2 · yr^-1 at the eutrophicated stations. The estimated total exudate release was 16% of the totally fixed ¹⁴CO₂ in the control area and 12% in the eutrophicated area (including the estimated bacterial uptake of exudates). The difference in¹⁴CO₂ uptake rates between incubation of previously filtered water (<3, <2, <1 m) and unfiltered water was used to estimate bacterial uptake of phytoplankton exudates which were found to contribute about half of the estimated bacterial carbon requirement in both areas. Bacterial production was estimated by the frequency of dividing cells (FDC) method as being 38 g C · m^-2 · yr^-1 at the control station and 50 g C · m^-2 · yr^-1 at the eutrophicated stations. To estimate the mean in situ bacterial cell volume a correlation between FDC and cell volume was used. The increased annual primary production in the eutrophicated area was due mainly to higher production during spring and autumn, largely by phytoplankton cells (mainly diatoms) retained by a 10 m filter. Primary production duringsummer was similarin the two areas, as was the distribution on different size fractions. This could possibly explain the similar bacterial production in the trophic layers at all stations since the bulk of bacterial production occurs during summer. It was demonstrated that selective filtration does not quantitatively separate photoautotrophs and bacteria. A substantial fraction of the primary production occurs in the size fraction <3 m. The primary production encountered in the 3-0.2 m fraction was due to abundant picoplankton (0.5 to 8 · 10⁷ ind · l^-1), easily passing a 3 m filter. The picoplankton was estimated to constitute up to 25% of the total phytoplankton biomass in the control area and up to 10% in the eutrophicated area.     

Feeding,growth and bioluminescence of the heterotrophic dinoflagellate Protoperidinium huberi

Feeding, growth and bioluminescence of the thecate heterotrophic dinoflagellate Protoperidinium huberi were measured as a function of food concentration for laboratory cultures grown on the diatom Ditylum brightwellii. Ingestion of food increased with food concentration. Maximum ingestion rates were measured at food concentrations of 600 g C l^-1 and were 0.7 g C individual^-1 h^-1 (1.8 D. brightwelli cells individual^-1 h^-1). Clearance rates decreased asymptotically with increasing food concentration. Maximum clearance rates at low food concentration were ca. 23 l ind^-1 h^-1, which corresponds to a volume-specific clearance rate of 5.9x10⁵ h^-1. Cell size of P huberi was highly variable, with a mean diameter of 42 m, but no clear relationship between cell size and food concentration was evident. Specific growth rates increased with food concentration until maximum growth rates of 0.7 d^-1 were reached at a food concentration of 400 g C l^-1 (1000 cells ml^-1). Food concentrations as low as 10 g C l^-1 of D. brightwellii (25 cells ml^-1) were able to support growth of P. huberi. The bioluminescence of P. huberi varied with its nutritional condition and growth rate. Cells held without food lost their bioluminescence capacity in a matter of days. P. huberi raised at different food concentrations showed increased bioluminescence capacity, up to food concentration that supported maximum growth rates. The bioluminescence of P. huberi varied over a diel cycle, and these rhythmic changes persisted during 48 h of continuous darkness, indicating that the rhythm was under endogenous control.     

Diurnal patterns in photosynthetic capacity and depth-dependent photosynthesis-irradiance relationships inSynechococcus spp. and larger phytoplankton in three water masses in the Northwest Atlantic Ocean

The photosynthetic characteristics of prokaryotic phycoerythrin-rich populations of cyanobacteriaSynechococcus spp. and larger eukaryotic algae were compared at a neritic frontal station (Pl), in a warm-core eddy (P2), and at Wilkinson's Basin (P3) during a cruise in the Northwest Atlantic Ocean in the summer of 1984.Synechococcus spp. numerically dominated the 0.6 to 1 m fraction, and to a lesser extent the 1 to 5 m size fractions, at most depths at all stations. At P2 and P3, all three size categories of phytoplankton (0.6 to 1 m, 1 to 5 m, and >5 m) exhibited similar depth-dependent chages in both the timing and amplitude of diurnal periodicities of chlorophyllbased and cell-based photosynthetic capacity. Midday maxima in photosynthesis were observed in the upper watercolumn which damped-out in all size fractions sampled just below the thermocline. For all size fractions sampled near the bottom of the euphotic zone, the highest photosynthetic capacity was observed at dawn. At all depths, theSynechococcus spp.-dominated size fractions had lower assimilation rates than larger phytoplankton size fractions. This observation takes exception with the view that there is an inverse size-dependency in algal photosynthesis. Results also indicated that the size-specific contribution to potential primary production in surface waters did not vary appreciably over the day. However, estimates of the percent contribution ofSynechococcus spp. to total primary productivity in surface waters at the neritic front were significantly higher when derived from short-term incubator measurements of photosynthetic capacity rather than from dawn-to-duskin situ measurements of carbon fixation. The discrepancy was not due to photoinhibitory effects on photosynthesis, but appeared to reflect increased selective grazing pressure onSynechococcus spp. in dawn-to-dusk samples. Low-light photoadaptation was evident in analyses of the depth-dependency ofP-I parameters (photosynthetic capacity,P _max; light-limited slope, alpha;P _max alpha,I _k ; light-intensity beyond which photoinhibition occurs,I _b ) of the > 0.6 m communities at all three stations and was attributable to stratification of the water column. There was a decrease in assimilation rates andI _k with depth that was associated with increases in light-limited rates of photosynthesis. No midday photoinhibition ofP _max orI _b was observed in any surface station. Marked photoinhibition was detected only in the chlorophyll maximum at the neritic front and below the surface mixed-layer at Wilkinson's Basin, where susceptibility to photoinhibition increased with the depth of the collected sample. The 0.6 to 1 m fraction always had lower light requirements for light-saturated photosynthesis than the > 5 m size fraction within the same sample. Saturation intensities for the 1 to 5 m and 0.6 to 1 m size fractions were more similar whenSynechococcus spp. abundances were high in the 1 to 5 m fraction. The > 5 m fraction appeared to be the prime contributor to photoinhibitory features displayed in mixed samples (> 0.6 m) taken from the chlorophyll maxima. InSynechococcus spp.-dominated 0.6 to 1 and 1 to 5 m size fractions, cellular chlorophylla content increased 50- to 100-fold with depth and could be related to increases in maximum daytime rates of cellularP _max at the base of the euphotic zone. Furthermore, the 0.6 to 1 m and > 5 m fractions sampled at the chlorophyll maximum in the warm-core eddy had lower light requirements for photosynthesis than comparable surface samples from the same station. Results suggest that photoadaptation in natural populations ofSynechococcus spp. is accomplished primarily by changing photosynthetic unit number, occuring in conjuction with other accommodations in the efficiency of photosynthetic light reactions.     

Background levels of soil beryllium in several countries

Beryllium and aluminium contents in uncontaminated soils from six countries are reported. The means and ranges of beryllium in the surface soils were as follows: 1.43(0.20–5.50)g g^–1 in Thailand (n=28), 0.7 (0.31–1.03) g g^–1 in Indonesia (n=12), 0.99(0.82–1.32) g g^–1 in New Zealand (n=3), 0.58(0.08-1.68)g g^–1 in Brazil (n=16), 3.52(2.49–4.97)g g^–1 in the former Yugoslavia (n=10), and 1.56(1.01–2.73) g g^–1 in the former USSR (n=8). The mean and range of beryllium contents of the surface soils in Japan (1.17(0.27–1.95)g g^–1 n=27) are situated within the values of the soils from these countries except for the Yugoslav soils derived from limestones. The mean of the mean beryllium contents of the surface soils in all these countries is 1.42 g g^–1 which will be used as a tentative average content of beryllium in uncontaminated surface soils, except for the soils derived from parent materials high in beryllium content. The beryllium contents of the subsoils were higher than those of the surface soils in New Zealand and Yugoslavia as is the case with Japan. The correlation coefficient between the contents of beryllium and aluminium in all the soil samples (n=113) including surface soils and subsoils was 0.505 (p < 0.001).     

Grazing and ingestion rates of nauplii,copepodids and adults of the marine planktonic copepod Calanus helgolandicus

The average grazing and ingestion rates of all stages of the marine planktonic copepod Calanus helgolandicus (Calanoida) from nauplius stage IV to adults were measured experimentally at 15°C in agitated cultures. The chain-forming diatom Lauderia borealis and the unarmoured dinoflagellate Gymnodinium splendens were offered as food. The food concentrations were close to natural conditions and ranged from 36 to 101 g of organic carbon per liter. The medium body weights expressed in g of organic carbon of almost all larval stages raised at 49 g C/1 were identical with the weight of the same stages caught in the Pacific Ocean off La Jolla, California, USA. In a log-log system, grazing and ingestion rates increased almost linearly with increasing body weight. Grazing rates ranged from 4 to 21 ml/day/nauplius stage IV to 286 ml to 773 ml/day/female. Ingestion rates increased from 0.2 g to 0.8 g C/day/nauplius stage IV to 18 g to 69 g C/day/female. Grazing and ingestion rates per unit body weight decreased gradually with increasing body weight. The daily ingested amount of food decreased from 292 to 481% of the body weight (g C) of nauplius stage V to 28–85% of the body weight of adult females. Grazing and ingestion performances of all stages increased with increasing particle size. Grazing rates decreased and ingestion rates increased with increasing food concentrations. The published data on food intake of the different age groups of C. helgolandicus show that the young stages of herbivorous planktonic copepods can play a major part in the consumption of phytoplankton in the sea due to their high grazing and ingestion rates.