Ammonia excretion by zooplankton and its significance to primary productivity during summer

Excretion rates of ammonia have been determined for zooplankton off the coasts of Washington and Oregon (USA). Rates varied from 0.16 to 0.60 g-at NH ₄ ⁺ -N/mg dry weight/day for most planktonic animals, and from 0.02 to 0.06 for jellyfishes. Ammonia concentration in seawater was low in offshore regions. Ammonia released by zooplankton was studied in relation to primary productivity during summer. It was found that, in the Columbia River plume offshore, excreted ammonia contributed about 90% of the total nitrogen requirements of observed production rates. The ammonia-N contribution was 36% in oceanic waters, and was relatively unimportant in the inshore region. The significance of eddy diffusivity in offshore waters and upwelling in inshore waters is also discussed.Contribution No. 747 from the Department of Oceanography, University of Washington, Seattle, USA.     

Role of echinoderms in benthic remineralization in the Chukchi Sea

The role of large, epibenthic organisms in carbon cycling at high latitudes is difficult to assess using standard ship-board collection techniques. We used a remotely operated vehicle equipped with video imaging to examine the distribution and abundance of epibenthic organisms in the northeast Chukchi Sea during June 1998. At each of 11 sites, we collected between 25 and 50 images from a minimum of 20 min of video. We observed 15 different epibenthic taxa, with the echinoderms (Ophiura sarsia, O. maculata, Ophiopholis aculeata, Stegophiura nodosa, and Echinarachinus parma) overwhelmingly dominating the epibenthos. Echinoderm density was highly variable, ranging from 0.2 to 256.6 individuals m^-2 (median=16.3), and echinoderm biomass varied between <0.5 and 4,988 mg C m^-2 (median=737). The highest biomass of ophiuroids recorded (3,388 mg C m^-2) is 30% higher than the highest previously reported from an Arctic shelf. Using a relationship between biomass and respiration developed for deep-sea organisms living at cold temperatures, we estimated respiration rates from <0.1 to 15.0 mg C m^-2 day^-1 (median=1.9). Respiration rates measured on board were several orders of magnitude higher than those obtained from the predictive equation. Further work is needed to assess echinoderm respiration rates accurately under in situ conditions. Even with calculated minimal values for respiration rates, a comparison of epifaunal and infaunal respiration at four stations revealed that echinoderm respiration accounted for as much as 25% of total respiration. High epifaunal respiration rates and biomass values are likely supported by high concentrations of particulate organic carbon carried by Bering Sea water flowing through the eastern Chukchi Sea. Our observations support observations from the Eurasian Arctic that echinoderms dominate the epibenthos of Arctic shelves and that the role of these organisms in carbon remineralization must be considered if we are to generate accurate models of carbon cycling in the Arctic.     

Metabolism and elemental composition of zooplankton from the Barents Sea during early Arctic summer

Rates of oxygen consumption, ammonia excretion and phosphate excretion were measured on a hydromedusae (Aglantha digitale), pteropods (Limacia helicina, Clione limacina), copepods (Calanus finmarchicus, C. glacialis, C. hyperboreus, Metridia longa), an amphipod (Parathemisto libellula), a euphausiid (Thysanoessa inermis) and a chaetognath (Sagitta elegans), all of which were dominant species in the Barents Sea during early summer 1987. Water and ash contents and elemental composition (C and N) were also analysed on the specimens used in these metabolic experiments. Between species variations were 67.8% to 94.7% of wet weight in water content, 6.4% to 56.5% of dry weight in ash content, 16.7% to 61.0% of dry weight in carbon content, and 4.3% to 11.2% of dry weight in nitrogen content. Oxygen consumption rates ranged from 0.33 to 13.8 l O₂ individual^-1 h^-1, ammonia excretion rates, from 0.0072 to 0.885 gN individual^-1 h^-1 and phosphate excretion rates, from 0.0036 to 0.33 g P individual^-1 h^-1. In general, higher rates were associated with larger species, but considerable differences were also seen between species. The ratios between the rates (O : N, N : P, O : P) exhibited a wide species-specific variation, indicating differences in dominant metabolic substrates. Typical protein oriented metabolism was identified only in S. elegans. From the results of metabolic rate measurements and elemental analyses, daily losses of body carbon and nitrogen were estimated to be 0.50 to 4.15% and 0.084 to 1.87%, respectively, showing faster turnover rates of carbon than that of nitrogen. Comparison of daily loss of body carbon of the Barents Sea zooplankton with that of the Antarctic zooplankton indicated reduced rates of the former (63% on average).     

Preliminary studies on primary productivity at Payakonda,Gulf of Kandalaksha,White Sea

Primary productivity studies were conducted at the White Sea Biological Station, Payakonda, during summer 1966. Oxygen and radio-carbon methods were employed; the oxygen method gave higher results. Variations in productivity due to tides were measured; low tide waters supported higher productivity rates.     

Contribution ofSynechococcus spp. to size-fractioned primary productivity in three water masses in the Northwest Atlantic Ocean

The distribution of phycoerythrin-richSynechococcus spp. relative to eukaryotic algae and the contribution ofSynechococcus spp. toin situ primary production were compared at a neritic front, in warm-core eddy 84-E, and at Wilkinson's Basin, during a cruise to the Northwest Atlantic Ocean in July/August 1984. Immunofluorescence analyses ofSynechococcus strains demonstrated the restricted distribution of the tropical oceanic serogroup to the warm-core eddy, while strains of the neritic serogroup and those labelled by antiserum directed against a motile strain, were abundant in all three water masses. Although the majority ofSynechococcus spp. cells were observed in the 0.6 to 1 m fraction, an increasing proportion of the totalSynechococcus spp. cells were found in the 1 to 5 m fraction as nitrate concentrations increased near the base of the thermocline. From immunofluorescence analyses, we determined that the increasing proportion of largerSynechococcus spp. cells at depth was not the result of a change in strain composition, and may therefore be associated with increasing cell volume due to the enhanced nutrient supply. The contribution of the different size fractions to the total standing crop of chlorophyll and thein situ rate of photosynthesis was distincty different for the three water masses. At the neritic front, the larger photoautotrophs of the 1 to 5 m and >5 m fractions were the major contributors to chlorophyll concentrations and primary production.Synechococcus spp. appeared to provide only 6% of the dawn-to-duskin situ primary production at the neritic front. In modified Sargasso water in the warm-core eddy,Synechococcus spp. contributed 25% to thein situ rate of integrated primary production. In this warm-core eddy, the 0.2 to 0.6 m fraction made a major contribution to the standing crop of chlorophyll and primary production that equalled or exceeded that of the larger sze categories. Furthermore, at the bottom of the euphotic layer, eukaryotes numerically dominated the 0.2 to 0.6 m fraction, which contributed 61% of the primary productivity. At Wilkinson's Basin, theSynechococcus spp.-dominated 0.6 to 1.0 m fraction made the greatest contribution to the standing crop of chlorophyll an primary production, while smaller photoautotrophs (0.2 to 0.6 m) accounted for little of the chlorophyll or photosynthetic rates measured over the euphotic layer. Largest numbers ofSynechococcus spp. (2.9x10⁸ cells l^-1) occurred at the 18% isolume, coincident with a shoulder in the chlorophyll fluorescence profile and the site of maximumin situ primary productivity. At Wilkinson's Basin,Synechococcus spp. contributed 46% to thein situ photosynthesis integrated over the water-column.     

Complex dynamics of toxin producing algal species and primary productivity in two water ponds of Faizabad

In order to develop a method of predicting and assessing pond eutrophication, which is a serious environmental problem, and to propose effective measure of improvement of water quality. The present study was performed to measure water quality variables, primary productivity, chl-a and biomass of toxin producing algal species and fish production. High nutrient influx and toxin producing algal species have been observed during June 1999 to May 2000 in two water bodies [Girija Kund (A) and Maqubara pond (B)] of Faizabad. The maximum chl-a concentration, toxins producing algal species biomass were found to be 415.00 and 515.00 in pond A, while 451.00 microg/l and 541.22 mg/l in pond B, respectively in the case of Microcystis aeruginosa. Ecological parameters to evaluate GPP, NPP and CR were found to be 297.00, 134.000 and 182.00 mgCm3/h in summer season in pond B, respectively which is higher than pond A. A poor association existed between chl-a and GPP. Temporal variation (Photosynthetic rate) in A(max) & P(max) was also observed to evaluate the productivity of pond. Annual fish production potential of the ponds A and B has been estimated to be around 342.00 Kg and 204. 00 Kg, respectively which may be due to the presence of toxin producing algal species.     

重污染河道中浮游植物初级生产力特征

通过对苏州城市河道的调查研究发现,城市河道的浮游植物初级生产力与其它水体有明显不同。从2004年6月至2005年5月通过取样分析苏州苗家河水体浮游植物种类、数量和叶绿素a含量变化及采用黑白瓶法测定浮游植物产氧能力,结果表明:该河道氮、磷含量较高,浮游植物群落为绿藻-硅藻型,种类少,季节变化明显,水体中表层叶绿素a的含量低于底层。分析表层水体和底层水体叶绿素a的产氧能力发现,河道中浮游植物的光合产氧能力普遍较低。本文揭示了重污染河道中大量悬浮颗粒附着在浮游植物的体表,影响了浮游植物的光合产氧能力,是整个水体和底泥中的溶氧普遍较低的重要原因之一。探讨了重污染河道溶氧偏低产生黑臭的原因,为重污染河道的综合治理提供了参考。     

重污染河道中浮游植物初级生产力特征

通过对苏州城市河道的调查研究发现,城市河道的浮游植物初级生产力与其它水体有明显不同。从2004年6月至2005年5月通过取样分析苏州苗家河水体浮游植物种类、数量和叶绿素a含量变化及采用黑白瓶法测定浮游植物产氧能力,结果表明：该河道氮、磷含量较高,浮游植物群落为绿藻一硅藻型,种类少,季节变化明显,水体中表层叶绿素a的含量低于底层。分析表层水体和底层水体叶绿素a的产氧能力发现,河道中浮游植物的光合产氧能力普遍较低。本文揭示了重污染河道中大量悬浮颗粒附着在浮游植物的体表,影响了浮游植物的光合产氧能力,是整个水体和底泥中的溶氧普遍较低的重要原因之一。探讨了重污染河道溶氧偏低产生黑臭的原因,为重污染河道的综合治理提供了参考。     

Mesoscale variability related to iron speciation in a coastal Ross Sea area (Antarctica) during summer 2014

Dissolved iron (Fe) distribution and speciation was determined in water samples (0–200?m) collected in a coastal area near Terra Nova Bay during the austral summer of 2014. Nutrients, dissolved oxygen, chlorophyll-a, phytoplankton composition and prokaryotic biomass distribution were investigated in combination with measurements of the physical properties of the water columns and its dynamics. The dFe value was above the limiting growth concentration, ranging from 0.52 to 4.51?nM, and it showed a spatial variability with a horizontal length scale of about 10?km, according to the variability of the water column physical properties and to iron sources. The organic ligands (L) maintained the concentrations of dFe at levels much higher than the inorganic solubility of Fe, keeping it available for phytoplankton and the log K’_FeL values found (from 22.1 to 23.6) highlighted the presence of complexes of differing stabilities.     

Net primary productivity of some aquatic macrophytes in sewage-sullage mixture

Sewage-sullage mixture from Raipur city is spread over a vast area surrounding the city. This mixture has a pH always above neutrality with high turbidity. Transparency was nil with the absence of phenolphthalein alkalinity and dissolved oxygen. Hardness was high with low nitrogen and phosphorus concentration. Human consumable. acquatic macrophytes are cultivated in such waste water. Net primary productivity of three macrophytes: Ipomoea aquatica, Marsilea quadrifolia and Nelumbo nucifera were evaluated while being cultivated in such sewage-sullage mixture. Productivity was determined either with periodic biomass removal (I. aquatica and M. quadrifolia) or through removing the biomass only once at the time of growing season (N. nucifera). Growing season productivity of up to 27.48. 19.81 and 9.49 g m(-2) and day(-1) and extrapolated productivity of up to 100.30, 72.31 and 34.64 mt. ha(-1) yr(-1) was recorded for I. aquatica. M. quadrifolia and N. nucifera respectively. Thus, these macrophytes are yielding a high amount of human consumable biomass from an area which neither be a useless wetland.     

Effects of local fisheries and ocean productivity on the northeastern Ionian Sea ecosystem

To better understand the effects of fisheries and ocean productivity on the northeastern Ionian Sea we constructed an Ecopath with Ecosim model with 22 functional groups. Data on biomass, production/biomass, consumption/biomass, and diet for each group were estimated or extrapolated from the literature. Fisheries landings and discards were also included. Temporal trajectories were simulated using Ecosim. The model was fitted with time-series data for the most important groups from 1964 to 2006. Simulations highlighted a decline of top predators and of most of the commercial species since the late 1970s. The model shows that the decline of fish resources was mainly caused by an intensive fishing pressure that occurred in the area until the end of the 1990s and also by changes in primary production that impacted the trajectories of the main functional groups. In particular, simulated changes through time in PP impacted the abundance trends of all the commercial species, showing a cascade-up effect through the ecosystem. The application of Ecopath with Ecosim was a useful tool for understanding the trends of the main functional groups of the northeastern Ionian Sea. The model underlined that management actions are needed to restore and protect target species including marine mammals, pelagic and demersal fishes. In particular, measures to reduce overfishing, illegal fishing activities and to respect existing legislations are in need. Moreover, the adoption of marine protected areas could be an effective management measure to guarantee prey survival and to sustain marine predators.     

Optical characterization of primary productivity across a coastal front

Methods for the remote estimation of phytoplankton biomass and production rates using multiplatform sampling strategies are essential for the better understanding of oceanic bio-geochemical cycles. Recent advances in remote sensing of ocean color have made synoptic estimation of phytoplankton biomass attainable. While considerable success has been achieved in the estimation of plant biomass, the synoptic estimation of phytoplankton rates of production has been inadequate. Rapid shipboard estimates of the vertical distribution of primary productivity, on mesoscale spatial scales and event-time scales, are needed to provide both surface validation and data for the development of bio-optical models linking production to the optical characteristics of the water column. This study details the primary productivity and optical properties of a frontal region in July 1985 along 35°50N in the Southern California Bight which is shown to be consistent with the concurrent high-performance liquid-chromatography pigment-analysis. We describe here a quasi-synoptic shipboard bio-optical sampling strategy across a frontal region as an example of time-corrected data for assessing phytoplankton production in highly variable ocean regions.     

Cooling water chlorination and productivity of entrained phytoplankton

A study to determine the effects of various concentrations of chlorine on the productivity of entrained marine phytoplankton was carried out at a nuclear power station on northeastern Long Island Sound, USA. Chlorine is a biocide used to control the growth of marine fouling organisms on the walls of many power station cooling systems. Chlorine concentrations considerably below those required to eliminate fouling organisms produced large decreases in the productivity of entrained phytoplankton. Generally, between 0.25 and 0.75 ppm residual chlorine at the cooling water discharge, continuously applied, is required to eliminate fouling organisms. At the highest chlorine concentration tested, 0.4 ppm residual at discharge (addition of chlorine at 1.2 ppm at cooling water intake), there was an 83% decrease in productivity as compared with the productivity at the intake. Productivity measurements were made at 6 other continuously applied chlorine concentrations. At the lowest concentration tested, too low to measure with our analytical method (addition of chlorine at 0.1 ppm at the intake), we measured a production decrease of 79%. Thus, a decrease in chlorination dosage of over an order of magnitude produced essentially no reduction in the damage done to entrained phytoplankton. Application of chlorine intermittently produced somewhat less of a decrease in primary productivity. When there was no chlorine addition during the period of study, there was essentially no effect on productivity. These data indicate that chlorine cannot be used effectively as a biocide for fouling organisms without having adverse effects on entrained phytoplankton.Contribution No. 2838 of the Woods Hole Oceanographic Institution.     

Carbon, nitrogen, oxygen and sulfide budgets in the Black Sea: A biogeochemical model of the whole water column coupling the oxic and anoxic parts

Carbon, nitrogen, oxygen and sulfide budgets are derived for the Black Sea water column from a coupled physical-biogeochemical model. The model is applied in the deep part of the sea and simulates processes over the whole water column including the anoxic layer that extends from ?115 m to the bottom (?2000 m). The biogeochemical model involves a refined representation of the Black Sea foodweb from bacteria to gelatinous carnivores. It includes notably a series of biogeochemical processes typical for oxygen deficient conditions with, for instance, bacterial respiration using different types of oxidants (i.e denitrification, sulfate reduction), the lower efficiency of detritus degradation, the ANAMMOX (ANaerobic AMMonium OXidation) process and the occurrence of particular redox reactions. The model has been calibrated and validated against all available data gathered in the Black Sea TU Ocean Base and this exercise is described in Gregoire et al. (2008). In the present paper, we focus on the biogeochemical flows produced by the model and we compare model estimations with the measurements performed during the R.V. KNORR expedition conducted in the Black Sea from April to July 1988 (Murray and the Black Sea Knorr Expedition, 1991). Model estimations of hydrogen sulfide oxidation, metal sulfide precipitation, hydrogen sulfide formation in the sediments and water column, export flux to the anoxic layer and to the sediments, denitrification, primary and bacterial production are in the range of field observations.With a simulated Gross Primary Production (GPP) of 7.9 mol C m⁻² year⁻¹ and a Community Respiration (CR) of 6.3 mol C m⁻² year⁻¹, the system is net autotrophic with a Net Community Production (NCP) of 1.6 mol C m⁻² year⁻¹. This NCP corresponds to 20% of the GPP and is exported to the anoxic layer. In order to model Particulate Organic Matter (POM) fluxes to the bottom and hydrogen sulfide profiles in agreement with in situ observations, we have to consider that the degradation of POM in anoxic conditions is less efficient that in oxygenated waters as it has often been observed (see discussion in Hedges et al., 1999). The vertical POM profile produced by the model can be fitted to the classic power function describing the oceanic carbon rate (C_R=Z^−α) using an attenuation coefficient α of 0.36 which is the value proposed for another anoxic environment (i.e. the Mexico Margin) by Devol and Hartnett (2001). Due to the lower efficiency of detritus degradation in anoxic conditions and to the aggregation of particles that enhanced the sinking, an important part of the export to the anoxic layer (i.e. 33%, 0.52 mol C m⁻² year⁻¹) escapes remineralization in the water column and reaches the sediments. Therefore, sediments are active sites of sulfide production contributing to 26% of the total sulfide production.In the upper layer, the oxygen dynamics is mainly governed by photosynthesis and respiration processes as well as by air-sea exchanges. ?71% of the oxygen produced by phytoplankton (photosynthesis+nitrate reduction) is lost through respiration, ?21% by outgasing to the atmosphere, ?5% through nitrification and only ?2% in the oxidation of reduced components (e.g. Mn²⁺, Fe²⁺, H₂S).The model estimates the amount of nitrogen lost through denitrification at 307 mmol N m⁻² year⁻¹ that can be partitioned into a loss of ?55% through the use of nitrate for the oxidation of detritus in low oxygen conditions, ?40% in the ANAMMOX process and the remaining ?5% in the oxidation of reduced substances by nitrate.In agreement with data analysis performed on long time series collected since the 1960s (Konovalov and Murray, 2001), the sulfide and nitrogen budgets established for the anoxic layer are not balanced in response to the enhanced particle fluxes induced by eutrophication: the NH₄ and H₂S concentrations increase.     

A simulation model of the effects of vertical mixing on primary productivity

A random walk stimulation model was developed to explore the effects of variations in light regimes due to vertical mixing on primary productivity. Cells were allowed to light-shade adapt on some time scale by altering chl:carbon ratios in response to variations in light regimes. Photosynthetic response was adjusted according to variations in chl: carbon ratios by either varying the initial slopes of photosynthesis-irradiance curves, or varying photosynthetic capacities. The model suggests that despite physiological adaptation to light, vertical mixing may have little effect on the integrated water column primary productivity. It is suggested that if photoinhibition does not have a pronounced effect, the average distribution of primary production in a water column is not related to variations in light regimes arising from turbulent diffusion processes.This research was performed under the auspices of the US Department of Energy under Contract No. DE-ACO2-76CH00016 and partially supported by the International Decade of Ocean Exploration (IDOE), NSF, as part of the Coastal Upwelling Ecosystems Analysis (CUEA) program.     

Large viruses and infected microeukaryotes in Ross Sea summer pack ice habitats

A variety of Ross Sea summer pack ice habitats between 66 and 75°S were examined for viruses 𔒦 nm capsid diameter. Maximum abundances of these viruses likely to infect eukaryotes were 10⁶-10⁷ ml^-1 brine in surface, interior, and bottom habitats and constituted up to 18% of the total (all sizes) viruses. There is abundant ultrastructural evidence for infection of a variety of microheterotrophs and some autotrophs. One station exhibited the classical characteristics of a lower latitude algal bloom with potential viral control. The blooming alga, Pyramimonas tychotreta Daugbjerg 2000, was infected, as were two abundant heterotrophs, Cryothecomonas spp. and an unidentified flagellate, that fed on P. tychotreta. Infections were observed in only one life history stage (multiflagellate cells) of P. tychotreta, suggesting a relationship among virus-induced lysis, life-history stages, physiology, and environmental factors regulating the life cycle. There is good evidence that diatoms are not a likely source of the large viruses, and viruses in general are not a major food source for ice microheterotrophs in summer.     

The early summer bloom of dinoflagellates in the North Sea,with special reference to 1971

The south-western quarter of the North Sea (between the Wash and the River Tyne) has been investigated for the presence of dinoflagellates. Extensive net surveys were carried out in March, May and June 1971 and a number of other collections were made in the area. North of Flamborough Head, the spring bloom of diatoms was succeeded by a considerable growth of dinoflagellates, of which Dinophysis norvegica was the most abundant organism. Maximum counts of over 28 million dinoflagellates per m³ were recorded. Distribution charts are given for the most common species. A total of 61 species was found during the course of the survey.     

Heterotrophic flagellates from the water column in Shark Bay, Western Australia

The diversity of heterotrophic flagellates in the water column at Denham, in Shark Bay, Western Australia, was examined in April 1995 by observations of living cells in freshly collected samples, and in enrichment cultures. Observations were also made of cells on whole-mount preparations, using light and electron microscopy. A total of 41 species are described, drawn from the apusomonads, cercomonads, choanoflagellates, cryptomonads, euglenids, heteroloboseids, stramenopiles and groups of uncertain taxonomic affinities (Protista incertae sedis). A new species, Percolomonas denhami, is described and assigned to the Heterolobosea. Three-quarters of the species seen have not previously been reported from southern sub-tropical regions. The biogeography of the species seen in Western Australia is discussed with reference to studies in other localities. It appears that many heterotrophic flagellates have a cosmopolitan distribution. Received: 11 June 1996 / Accepted: 13 December 1996