Comparison of bacterial and algal utilization of orthophosphate in an estuarine environment

Bacterial utilization of orthophosphate in an estuarine environment has been differentiated from algal utilization by using flow-filters of 5.0, 1.2 and 0.45 m poresize. Examination by light microscopy showed that most of the bacterial population passed through a 5.0-m filter, whereas most algae were retained. In all experiments, bacterial and algal cell numbers and biomass were estimated. P-uptake by algae and bacteria was closely correlated with cell biomass. P-uptake by algae was high only in the summer months, whereas P-uptake by bacteria was high throughout the year. Neither algal nor bacterial P-uptake, however, was correlated with temperature or dissolved orthophosphate, total organic phosphate or total phosphate concentrations. Cell biomass of algae at a given time had a high correlation with dissolved organic phosphate levels in 2 weeks prior to sampling (r=0.830) and a low correlation in the 2 weeks following sampling (r=0.0005). Algal cell numbers had a high correlation with bacterial cell numbers (r=0.950). The biomass of algae and bacteria also had a high correlation (r=0.902). The rate of P-uptake from the water by algae and bacteria varied with season and with the species composition of the natural population.     

Nutrient regeneration by zooplankton during a red tide off Peru,with notes on biomass and species composition of zooplankton

During March and April 1976, a red tide, dominated by the dinoflagellate Gymnodinium splendens Lebour, developed in the vicinity of 15°06'S and 75°31'W off Peru. At the height of the bloom, the euphotic zone was 6 m deep and the chlorophyll a at the surface was 48 g l^-1. A daily collection of zooplankton at 09.00 hrs showed large fluctuations of biomass, from 0.2 to 3.84 g dry weight m^-2 in a water column of 120m. Copepodids and nauplii dominated the collections. During a period of reduced wind, the adult copepods were a mixture of the species characteristic of the coastal upwelling system and the neritic species associated with more northerly, tropical waters. Nitrogen regeneration by the zooplankton varied with the development of the bloom, the type of zooplankton dominating the experiment, and biomass fluctuations, but never accounted for more than 25% of the nitrogen uptake by phytoplankton.     

Relationship between the zooplankton,phytoplankton, particulate matter and dissolved free amino acids in the Celtic Sea

Estimates of the biomass of zooplankton, phytoplankton and particulate matter collected in the Celtic Sea during mixed-water conditions (on 8 and 9 April 1983) were compared to the concentration and diversity of sixteen dissolved free amino acids (DFAA) measured in seawater and in particles. During a day profile, variations of dissolved amino acids with depth reflected the feeding activity of copepods. The relationship was not apparent in a night profile and other processes, such as heterotrophic utilization of dissolved nitrogen by microorganisms, were thought to be involved. The ratios of total DFAA concentration (nM litre^-1) in the particulate phase over the concentration in seawater ranged from 1 to 200 within the water column. Of the sixteen amino acids measured, ornithine, a decomposition product of arginine, was responsible for more than 70% of the total concentration of DFAA in seawater. In the particles, phenylalanine ranged from 30 to 88% of total DFAA. In seawater this amino acid occurred in the 20 to 40 m depths (1.3 to 9.9% of total DFAA) in the day profile and at 5 m (12.4%) and 80 m (6.4%) in the night profile. Previously it has only been found in very low concentrations (<5%) in seawater, and its presence is considered to be the result of zooplankton feeding.     

Zooplankton abundance and grazing at Davies Reef,Great Barrier Reef,Australia

Zooplankton abundance and grazing on autotrophic and heterotrophic particulate matter were measured along a transect across Davis Reef (18°5S; 147°39E) and in the back-reef lagoon over tidal and diel cycles during austral winter (August 1984). Zooplankton entering the reef from the surrounding shelf waters decreased in abundance over the reef flat, presumably because of predation. Within the reef lagoon, maximum daytime densities of pelagic copepods occurred during high water, suggesting an external input. At night, water-column zooplankton biomass increased by a factor of 2 to 3 due to the emergence of demersal reef zooplankton. Zooplankton grazing rates on heterotrophic particulate matter (bacteria + detritus and Protozoa) compared to phytoplankton were higher on the reef flat than on the fore-reef or lagoon. Within the lagoon, zooplankton grazing rates on heterotrophic material were maximum during high water, coincident with maximum tidal concentrations of particulate organic carbon. The combined demersal and pelagic zooplankton community were often able to crop 30% of the daily primary production by >2µm phytoplankton. However, >50% of phytoplankton biomass was in cells <2µm, presumably unavailable to these zooplankton. Our particulate production and ingestion measurements, together with zooplankton carbon demand extrapolated from respiration estimates, suggest that the zooplankton community of Davies Reef derives much of its nutrition from detritus.Joint contribution from the University of Maryland, Center for Environmental and Estuarine Studies (No. 2015), and the Microbial Ecology on a Coral Reef Workshop (MECOR No. 19)     

Quality standard codes of reference of Jordanian coastal waters of the Gulf of Aqaba,Red Sea

Back in 1992, the Gulf of Aqaba Environmental Action Plan (GAEAP), a collaboration between the Aqaba Region Authority (ARA), Jordan and the World Bank, gave considerable emphasis to the environmental protection of the Gulf of Aqaba [The World Bank. Gulf of Aqaba Environmental Action Plan. Report No. 12244JO (1993).]. The document recommended the establishment of a marine reserve and the long term monitoring of the coastal habitats’ environmental quality. The combination of a dedicated follow up, the collaborative efforts of ARA and the Marine Science Station (MSS), and the founding of the Aqaba Special Economic Zone Authority (ASEZA) have turned the recommendations into reality. A comprehensive monitoring program of the Jordanian coastal habitats commenced in 1999. The first three years of the program were financed by a donation from The Global Environmental Facility (GEF). In return, Jordan has committed itself to the maintenance of the monitoring program as an ongoing tool for sustainable coastal management. The monitoring program includes observations on benthic habitat, fish communities, bottom sediments and seawater quality. This paper focuses on the results of seawater-quality monitoring in the first three years. Records of weather conditions, coastal currents, seawater temperature, transparency, salinity, density, pH, alkalinity, dissolved oxygen, ammonia, nitrate, nitrite, phosphate, silicate, particulate matter, chlorophyll a, zooplankton biomass, total coliform, fecal coliform, hydrocarbons and sedimentation rate have been generated monthly since January 1999 at six coastal stations, and one offshore reference station, in the Jordanian waters of the Gulf of Aqaba. The coastal stations are located at sites with different benthic habitats and are occupied by different human activities. Offshore records of density (thermohaline structure), nutrients and chlorophyll a depicted two well-defined seasons; a nutrient-/chlorophyll a-rich, mixed water winter from December to April and a nutrient-/chlorophyll a-poor, stratified water summer from June to October. Short transition seasons appeared in May and November. The mixing and stratification seasons were also clearly depicted in the coastal waters. Statistical analysis of the three-year data collected at the offshore station revealed no significant inter-annual differences in the upper 125 m of the water column with respect to any of the measured parameters. At coastal stations, the water quality at the two northernmost stations was significantly different in comparison to the upper 125 m at the offshore station and to the other coastal stations, with respect to the two key indicator parameters: inorganic nitrogen and chlorophyll a. The three-year findings of the monitoring program are employed to suggest standard codes of reference for the coastal water quality.     

Primary production and phytoplankton community structure during a winter shelf-scale phytoplankton bloom off Western Australia

Regions of high primary production along the oligotrophic west coast of Australia between 34 and 22°S in May–June 2007 (midway through the annual phytoplankton bloom) were found around mesoscale features of the Leeuwin Current. At 31°S, an anticyclonic eddy-forming meander of the Leeuwin Current had a mixed layer depth of >160 m, a depth-integrated chlorophyll a (Chl a)-normalised primary production of 24 mg C mg Chl a ^?1 day^?1 compared to the surrounding values of <18 mg C mg Chl a ^?1 day^?1. In the north between 27 and 24°S, there were several stations in >1,000 m of water with a shallow (<100 m) and relatively thin layer of high nitrate below the mixed layer but within the euphotic zone. These stations had high primary production at depths of ~100 m (up to 7.5 mg C m^?3 day^?1) with very high rates of production per unit Chl a (up to 150 mg C mg Chl a ^?1 day^?1). At 27–24°S, the majority of the phytoplankton community was the ubiquitous tropical picoplankters, Synechococcus and Prochlorococcus. There was a decline in the dominance of the picoplankters and a shift towards a more diverse community with more diatoms, chlorophytes, prasinophytes and cryptophytes at stations with elevated production. Photosynthetic dinoflagellates were negligible, but heterotrophic dinoflagellate taxa were common. Haptophytes and pelagophytes were also common, but seemed to contribute little to the geographical variation in primary production. The mesoscale features in the Leeuwin Current may have enhanced horizontal exchange and vertical mixing, which introduced nitrate into the euphotic zone, increasing primary production and causing a shift in phytoplankton community composition in association with the annual winter bloom.     

Fine-scale distribution of juvenile cephalopods in the Scotia Sea and adaptive allometry of the brachial crown

The pelagic nekton community was sampled with the RMT 25 opening/closing net and a neuston net at two stations in the Scotia Sea south of the Antarctic Polar Front in the open ocean (Station 1) and on the South Georgia northwestern slope (Station 2). Downward oblique tows were made with the RMT 25 through discrete 200 m layers to 1000 m in daylight and darkness. A total of 119 cephalopods representing nine species were removed from the samples, and mantle and arm lengths were measured to the nearest 0.1 mm. The most abundant species at each station was an undescribed Brachioteuthis sp. (B. ?picta). Galiteuthis glacialis and Alluroteuthis antarcticus were caught at both stations. Histioteuthis eltaninae, Bathyteuthis abyssicola and Psychroteuthis glacialis were caught at Station 1. Mastigoteuthis psychrophila and a Chiroteuthis sp. were caught at Station 2. B. ?picta was present throughout the water column to 1000 m at both stations, with little evidence of ontogenetic descent. There was evidence for ontogenetic descent in G. glacialis. This species was absent from the Antarctic Surface Water (ASW) at Station 1, where it was concentrated in the Circumpolar Deep Water (CDW). At Station 2 it was present throughout the water column to 1000 m. The other species were all caught in the core of the CDW (>400 m). In juvenile B. ?picta, G. glacialis and A. antarcticus, growth of the brachial crown is positively allometric with respect to mantle length. Recent data on biomass spectra in high-latitude pelagic systems show that they are characterised by the presence of peaks of biomass separated by biomass minima. Positive allometric growth in the brachial crown of these antarctic oceanic squid is suggested to have evolved as an adaptation to the peaked, or domed, structure of the pelagic biomass spectrum which must be spanned by these predators as their optimum prey size increases with growth. Interspecific differences in the allometry of tentacle growth are probably related to differences in strategies for stalking and capture of prey.     

Sex pheromone of the tea aphid,Toxoptera aurantii (Boyer de Fonscolombe) (Hemiptera: Aphididae)

The tea aphid, Toxoptera aurantii, also called the “black citrus aphid”, is one of the most destructive insect pests in commercial tea plantations and gardens in southern China. In autumn, declining day length triggers production of winged T. aurantii sexuparae, which produce both winged males and wingless oviparae. Oviparous females then release sex pheromone that attracts potential mates. GC–MS analysis of volatile headspace extracts of T. aurantii oviparae revealed that they emit (4aS,7S,7aR)-nepetalactone (I) and (1R,4aS,7S,7aR)-nepetalactol (II) in a ratio of 4.3–4.9:1. Field-trapping experiments with synthetic I and II singly or as two-component blends of different doses and ratios showed significant attraction of T. aurantii males, as well as weak attraction of sexuparae. Identification of the T. aurantii sex pheromone provides a new opportunity for developing a pheromone-based monitoring and management strategy for the sexual phase of tea aphids and, possibly, the alate sexparous generation in late summer and fall.     

Exceptionally high concentrations of the insect repellent N,N-diethyl-m-toluamide (DEET) in surface waters from Jakarta,Indonesia

Jakarta is a booming coastal megacity in Indonesia with over 10 million inhabitants. The rivers flowing through the city district receive enormous amounts of untreated wastewaters from households and industries and discharge high pollutant loads into Jakarta Bay. Applying a screening approach for the identification of characteristic site-specific and harmful organic contaminants, we frequently found the insect repellent N,N-diethyl-m-toluamide (DEET) in river water and seawater samples from Jakarta. The compound was previously reported as persistent aquatic contaminant in industrial countries, and we present here the first data set from a tropical megacity. Concentrations in river water and seawater from Jakarta were exceptionally high, up to 24,000 ng L^?1, and exceeded by far all published concentrations in surface waters worldwide. We explained this with massive usage of the compound, lack of wastewater treatment and low average river flow as compared to rivers in other tropical megacities. The usage and properties of DEET indicate its suitability as molecular marker of municipal wastewaters. Such markers are useful to trace emissions from specific pollution sources in aquatic systems as a basis for the investigation of related impacts. We show here that DEET is in particular useful to trace the long-range distribution of municipal wastewaters in tropical freshwater and coastal systems. This application is of great value for tracing such inputs in tropical coastal habitats which are sensitive to changing water quality like coral reefs. This assists to uncover whether specific conditions in these systems could be related to pollutant inputs from land.     

Photoacclimation in phytoplankton: implications for biomass estimates, pigment functionality and chemotaxonomy

Chl a and C-normalized pigment ratios were studied in two dinophytes (Prorocentrum minimum and Karlodinium micrum), three haptophytes (Chrysochromulina leadbeateri, Prymnesium parvum cf. patelliferum, Phaeocystis globosa), two prasinophytes (Pseudoscourfieldia marina, Bathycoccus prasinos) and the raphidophyte Heterosigma akashiwo, in low (LL, 35 μmol photons m⁻² s⁻¹) and high light (HL, 500 μmol photons m⁻² s⁻¹). Pigment ratios in LL and HL were compared against a general rule of photoacclimation: LL versus HL ratios ≥1 are typical for light-harvesting pigments (LHP) and <1 for photoprotective carotenoids. Peridinin, prasinoxanthin, gyroxanthin-diester and 19′-butanoyloxy-fucoxanthin were stable chemotaxonomic markers with less than 25% variation between LL versus HL Chl a–normalized ratios. As expected, Chls exhibited LL/HL to Chl a ratios >1 with some exceptions such as Chl c ₃ in P. globosa and MV Chl c ₃ in C. leadbeateri. LL/HL to Chl a ratios of photosynthetic carotenoids were close to 1, except Hex-fuco in P. globosa (four-fold higher Chl a ratio in HL vs LL). Although pigment ratios in P. globosa clearly responded to the light conditions the diadinoxanthin-diatoxanthin cycle remained almost unaltered at HL. Total averaged pigment and LHP to C ratios were significantly higher in LL versus HL, reflecting the photoacclimation status of the studied species. By contrast, the same Chl a-normalized ratios were weakly affected by the light intensity due to co-variation with Chl a. Based on our data, we suggest that the interpretation of PPC and LHP are highly dependent on biomass normalization (Chl a vs. C).     

The spring phytoplankton bloom in Lindåspollene,a land-locked Norwegian fjord. II. Biomass and activity of net- and nanoplankton

From February 24 to April 24, weekly samples were collected at fixed depths at one station in Lindåspollene, a land-locked Norwegian fjord. Adenosine triphosphate (ATP), chlorophyll a, phaeophytin, ¹⁴C assimilation, and respiratory activity [electron transport system (ETS) activity] were measured in the net- (>30 m) and nanoplankton. Netplankton contained on the average 48% of the total chlorophyll a and 56% of the ATP, but contributed only 7% to the total carbon assimilation and 11% to the ETS activity. The assimilation numbers for net- and nanoplankton ranged from 0 to 1.2 and from 1.5 to 13.2, respectively. At the oxygen/hydrogen sulphide interface, high concentrations of ATP, but not of chlorophyll a, were found in the nanoplankton fraction. Netplankton algae grew actively only in the first phase of the bloom, and nanoplankton predominated later, apparently due to low nutrient concentrations. During the bloom, Skeletonema costatum made up the main part of the biomass. The number of cells in the chains decreased throughout the bloom, possibly reflecting the lowered silicate content. It appeared that only nanoplankton were grazed by zooplankton, while netplankton sank to the bottom and represented input to the benthos.     

Spring sea ice photosynthesis,primary productivity and biomass distribution in eastern Antarctica, 2002–2004

While it is known that Antarctic sea ice biomass and productivity are highly variable over small spatial and temporal scales, there have been very few measurements from eastern Antarctic. Here we attempt to quantify the biomass and productivity and relate patterns of variability to sea ice latitude ice thickness and vertical distribution. Sea ice algal biomass in spring in 2002, 2003 and 2004 was low, in the range 0.01–8.41 mg Chl a m⁻², with a mean and standard deviation of 2.08 ± 1.74 mg Chl a m⁻² (n = 199). An increased concentration of algae at the bottom of the ice was most pronounced in thicker ice. There was little evidence to suggest that there was a gradient of biomass distribution with latitude. Maximum in situ production in 2002 was approximately 2.6 mg C m⁻² h⁻¹ with assimilation numbers of 0.73 mg C (mg Chl a)⁻¹ h⁻¹. Assimilation numbers determined by the ¹⁴C incubations in 2002 varied between 0.031 and 0.457 mg C (mg Chl a)⁻¹ h⁻¹. Maximum fluorescence quantum yields of the incubated ice samples in 2002 were 0.470 ± 0.041 with E _k indices between 19 and 44 μmol photons m⁻² s⁻¹. These findings are consistent with the shade-adapted character of ice algal communities. In 2004 maximum in situ production was 5.9 mg C m⁻² h⁻¹ with an assimilation number of 5.4 mg C (mg Chl a)⁻¹ h⁻¹. Sea ice biomass increased with ice thickness but showed no correlation with latitude or the time the ice was collected. Forty-four percent of the biomass was located in bottom communities and these were more commonly found in thicker ice. Surface communities were uncommon.     

Gut evacuation rates and pigment destruction in the Antarctic krill Euphausia superba

Krill grazing data collected during cruises in the region of the Antarctic Polar Front (S.A. Agulhas Voyage 70) and the South Georgia shelf (R.V. Africana Voyage 119) during the austral summer of 1993 were analyzed to estimate the variability of crucial parameters of the gut fluorescence technique in relation to food availability and krill feeding history. Gut evacuation rates (k) and passage or throughput times (1/k) varied in the ranges of 0.101 to 0.424 h^-1 and 2.3 to 9.9 h and were strongly correlated (p<0.001, r ²=0.98) to krill feeding activity (estimated as initial gut pigment content, G₀) but not to ambient chlorophyll a concentration. A significant differences was found when k values derived from incubations in filtered seawater and low charcoal particle concentrations (0.4 to 0.8 mgl^-1) were compared with values derived from krill fed high concentrations of charcoal (6 mgl^-1). The efficiency of gut pigment destruction was among the highest recorded for zooplankton organisms, 58.1 to 98.4%, and did not covary significantly (p>0.05) with ambient food concentration. However, the pigment lost per individual krill was strongly correlated with the total amount of pigment ingested (p<0.001, r ²=0.99). We suggest that both gut evacuation rates and pigment destruction efficiency may be realistically estimated only when krill is allowed to continue ingesting particles uninterruptedly. Charcoal particle concentration should be equivalent to the in situ wet weight of total seston per unit volume. An objective criterion for the standardization of the measurement and calculation of k values is also proposed.     

Dynamique du phytoplancton et matière organique particulaire dans la zone euphotique de l'Atlantique Equatorial

At two fixed stations in the Equatorial Atlantic Ocean (0°–4° W), the physical, chemical and biological properties of the euphotic layer were determined for 14 d (Station A: 5–18 February, 1979) and 13 d (Station B: 20 October–7 November, 1979), respectively. The stability of the water column allowed comparison of 3 different “systems”: (i) a well-illuminated and nitrate-depleted mixed layer; (ii) a chlorophyll maximum layer (chl a _max) in the thermocline which is poorly illuminated (6.3% of surface irradiance); (iii) a well-illuminated but nitrate-rich (>0.9 μg-at l^-1) mixed layer. In each layer the particulate organic carbon (COP), nitrogen (NOP) and phosphorus (POP) contents were measured and compared with the phytoplankton biomass. In the chlorophyll maximum layer, the phytoplankton biomass contributed significantly to the total particulate organic matter (between 55 and 75%). In the nitrate-depleted mixed layer, the results varied according to whether the regression technique [COP=f(chl a)] was used, or the chl a synthesis during the incubation of the samples. With the former technique, the phytoplankton carbon (C _p) content appeared minimal, because the y intercept, computed using all the data of the water column, was probably overestimated for this layer. POP would be more associated with living protoplasm than with carbon and nitrogen in the three layers. In the chlorophyll a maximum layer it constitutes a valuable detritus-free biomass measurement, since 80% of the POP consist of phytoplankton phosphorus. The assimilation numbers (NA=μg C μg chl a ^-1 h^-1) were high in all three layers, but the highest values were recorded in the nitrate-depleted mixed layer (NA=15 μg C μg chl a ^-1 h^-1). In the chlorophyll maximum layer, light would be a limiting factor during incubation: between 10²⁵ and 8.10²⁴ quanta m^-2 d^-1 NA and light are positively correlated independant of nitrate concentration. The growth rates of phytoplankton (μ) were estimated and compared to the maximum expected growth rate. Our main conclusion was that despite very low biomass and nutrient content, the mixed layer was in a highly dynamic state, as evidenced by high rates of phytoplankton growth and short nutrient turnover times (1 d or less for PO-P₄ in the mixed layer versus 3 d in the thermocline). The presence of nitrate in the water column allows the development of a higher phytoplankton biomass but does not increase growth rate.     

Ecology of the northern Red Sea crinoids and their Epi- and Endozoic fauna

Fourteen crinoid species are found along the coral reefs of the northern Red Sea that form aggregations of different species at various depths. The shallowest aggregation consists partly of Lamprometra klunzingeri and Capillaster multiradiatus, occurring subtidal to a depth of 2 to 5 m. Of this group, Heterometra savignii inhabits depths down to 12–15 m. Further down, another group of 10-armed crinoids occurs, dominated by Decametra chadwicki and Oligometra serripinna. The deepest aggregation of crinoids occurs at 45 m; its most common members are Colobometra arabica and Comaster distinctus. Feeding on micro- and nanoplankton, shallow-water crinoids show a circadian activity rhythm; in deeper aggregations (10 to 12 m), this behaviour changes with decreasing illumination, to a diurnal activity rhythm. The symbiotic animals living on crinoids comprise 27 taxons, among them Copepoda (6 species), Mollusca (2 species), Polychaeta (11 species, especially Myzostomida); Ophiurida (1 species), Crustacea, Decapoda (6 species); and the clingfish Lepadichthys lineatus. These symbiotic animals form food webs at various depths, according to the distribution of their crinoid host. The occurrence of Indo-West Pacific and Mediterranean commensals on the same crinoid in the Gulf of Aqaba is of special interest.     

Exploring the influence of lake water chemistry on chlorophyll a: A multivariate statistical model analysis

A multivariate statistical approach integrating the absolute principal components score (APCS) and multivariate linear regression (APCS-MLR), along with structural equation modeling (SEM), was used to model the influence of water chemistry variables on chlorophyll a (Chl a) in Lake Qilu, a severely polluted lake in southwestern China. Water quality was surveyed monthly from 2000 to 2005. APCS-MLR was used to identify key water chemistry variables, mine data for SEM, and predict Chl a. Seven principal components (PCs) were determined as eigenvalues >1, which explained 68.67% of the original variance. Four PCs were selected to predict Chl a using APCS-MLR. The results showed a good fit between the observed data and modeled values, with R² = 0.80. For SEM, Chl a and eight variables were used: NH₄-N (ammonia-nitrogen), total phosphorus (TP), Secchi disc depth (SD), cyanide (CN), arsenic (As), cadmium (Cd), fluoride (F), and temperature (T). A conceptual model was established to describe the relationships among the water chemistry variables and Chl a. Four latent variables were also introduced: physical factors, nutrients, toxic substances, and phytoplankton. In general, the SEM demonstrated good agreement between the sample covariance matrix of observed variables and the model-implied covariance matrix. Among the water chemistry factors, T and TP had the greatest positive influence on Chl a, whereas SD had the largest negative influence. These results will help researchers and decision-makers to better understand the influence of water chemistry on phytoplankton and to manage eutrophication adaptively in Lake Qilu.     

Theoretical analysis of change in forest carbon use efficiency with stand development: A case study on Hinoki Cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.) plantation from the seedling stage

Changes in carbon use efficiency (CUE), which is defined as the ratio of net primary production (NPP) to gross primary production (GPP), were estimated for the aerial parts of the Hinoki Cypress (Chamaecyparis obtusa (Sieb. et Zucc.) Endl.) with respect to stand development. The analysis incorporated previously published data from the early stages of stand development, namely the seedling stages of the cypress. For this analysis, a simple mathematical model to assess the changes in CUE was developed by incorporating data on physiological variables and mass of woody species. The CUE tended to increase with increases in the aboveground biomass of the stand, and then decreased gradually despite increases in the aboveground biomass. The CUE-value (0.28, 0.39) of the seedling stage was lower than that (0.33-0.58) of the young or mature trees. To examine the effect of physiological variables and mass on CUE, the ratios of the specific respiration rate to the specific photosynthetic rate (r/a) and the leaf biomass to the aboveground biomass or leaf mass ratio (y_L/y_T) were calculated. The low value of CUE at the seedling stage was due to the high ratio of specific respiration rate to specific photosynthetic rate r/a, but was not due to the high value of the leaf mass ratio y_L/y_T. In addition, the decline in CUE associated with older stages of stand development was due to the decreasing changes in y_L/y_T, and the r/a ratio did not influence the change in CUE.     

Planktonic bioluminescence in the pack ice and the marginal ice zone of the Beaufort Sea

An icebreaker cruise into the Beaufort Sea in the fall of 1986 provided a unique opportunity for studying planktonic bioluminescence in ice fields and in the marginal ice zone. Bathyphotometer casts (bioluminescence intensity, seawater temperature, beam attenuation coefficient, and salinity) and biological collections were made to a depth of 100 m. A light budget, which describes the planktonic species responsible for the measured bioluminescence, and a dinoflagellate species budget were constructed from the mean light output from luminescent plankton and plankton counts. The vertical distribution of bioluminescence among the ice stations was similar. The maximum intensities were 2 to 8×10⁶ photons s^-1 cm^-3 in the upper 50 m of the sea-ice interface. The marginal ice zone station (MIZ) exhibited a maximum intensity of 2 to 3×10⁸ photons s^-1 cm^-3 between 5 and 30 m depth. At Ice Station 2, Metridia longa and their nauplii contributed approximately 80% of stimulable bioluminescence in the upper 10 m but, overall, Protoperidinium spp. dinoflagellates contributed most of the light to a depth of 100 m. In the MIZ, Protoperidinium spp. dinoflagellates contributed 90% of the light within the upper 10 m, decreasing to 43% of the contributed light at a depth of 40 m. Below 40 m, dinoflagellate bioluminescence decreased to a few percent of the total to a depth of 90 m. Metridia spp. copepods contributed more than 50% of the light at depths from 40 to 90 m. Ostracods, larvaceans, and euphausiid furcilia contributed <1% of all bioluminescence at all depths sampled. Correlation analyses between measured bioluminescence (photons s^-1 cm^-3), the number of bioluminescent dinoflagellates and the light budget for the MIZ indicated highly significant associations: r=0.919, p=0.001, and r=0.912, p<0.001, respectively (Student's two-tailed t-tests). Bioluminescence was negatively correlated with seawater salinity at all stations (p=0.001). Maximum bioluminescence was measured in the less saline surface waters at all stations.     

Growth rates of summer nanoplankton (<10 μm) populations in lower Narragansett Bay,Rhode Island,USA

Growth rates of summer (June–September) phytoplankton assemblages and constituent species were measured in 30 diffusion culture experiments. Size-fractionated (<10 m) phytoplankton assemblages were incubated in situ or under simulated in-situ conditions in outdoor tanks connected to a running seawater system. Doubling rates of important species and groups (such as microflagellates) were compared to community biomass doubling rates estimated from ¹⁴C uptake and changes in chlorophyll a concentrations. Division rates of dominant diatom species generally equalled or exceeded community biomass doubling rates, while those of flagellates and non-motile ultraplankters were slower. Maximum division rates of sixteen common diatom species exceeded 2.1 divisions d^-1, while nine had maximum division rates in excess of 3 d^-1. Mean division rates of 12 diatom species exceeded 1 d^-1. Maximum division rates of flagellated species, uncharacterized microflagellates and non-motile ultraplankton assemblages were 2.1, 1.5 and 1.4 d^-1, respectively. Microflagellate and non-motile ultraplankton assemblage doubling rates were less than 0.5 d^-1 in over half of all growth experiments.     

Differences in productivities between the Great Australian Bight and the Gulf of Carpentaria,Australia, in summer

Phytoplankton standing crop (chlorophyll a) and primary productivity were recorded, and zooplankton biomass was estimated in the two large bays of Australia, the Great Australian Bight on the south coast (December, 1965) and the Gulf of Carpentaria on the north coast (December, 1968). In the Gulf of Carpentaria, the phytoplankton standing crop (average, 27.3 mg chlorophyll a m^-2) and primary productivity (average, 133.1 mg C m^-2 h^-1), as well as zooplankton biomass (average, 305.3 mg wet weight m^-3) are much higher than in the Great Australian Bight (12.1 mg chlorophyll a m^-2, 18.2 mg C m^-2 h^-1, 7.1 mg wet weight m^-3, respectively). The unexpectedly low productivity values in the Great Australian Bight are attributable to environmental conditions of this bay, which obtains neither replenishment of nutrients from the land nor receives upwelling of deep water.