Population dynamic studies on phytoplankton cultures

The use of ozone as an oxidative supplement to biological filtration and to control epizootic microbial outbreaks coincident with maintaining a biological filter was investigated in a 2,271-1 (600 gallon) closed marine-water system. Under conditions of a relatively large biomass load (1.82 kg/3801), filter-bed effluent levels of total ammonia (0.135±0.01 ppm), un-ionized ammonia (0.0074±0.0006 ppm) and nitrite (0.17±0.01 ppm) were maintained within acceptable limits. Reservoir ozonation (100 mg/h/380 l) further significantly reduced (P<0.005) these levels. Nitrates were significantly elevated (P<0.005) with ozonation. Cessation of ozonation elevated total ammonia, un-ionized ammonia and nitrite levels above acceptable limits within 24 h. Resuming ozonation rapidly reversed this trend. Ozone reduced the microbial content of the culture water. Ozonation is suggested as a means of maintaining oxidative flexibility when used as a supplement to biological filtration. Further, prevention of epizootic microbial outbreaks may be accomplished without danger to the biological filter provided a proper system design is utilized.Contribution No. 342, Department of Biology.     

Tolerance of Hyas araneus zoea I larvae to elevated seawater PCO2 despite elevated metabolic costs

Early life stages of marine crustaceans respond sensitively to elevated seawater PCO₂. However, the underlying physiological mechanisms have not been studied well. We therefore investigated the effects of elevated seawater PCO₂ on oxygen consumption, dry weight, elemental composition, median developmental time (MDT) and mortality in zoea I larvae of the spider crab Hyas araneus (Svalbard 79°N/11°E; collection, May 2009; hatch, December 2009). At the time of moulting, oxygen consumption rate had reached a steady state level under control conditions. In contrast, elevated seawater PCO₂ caused the metabolic rate to rise continuously leading to a maximum 1.5-fold increase beyond control level a few days before moulting into the second stage (zoea II), followed by a pronounced decrease. Dry weight of larvae reared under high CO₂ conditions was lower than in control larvae at the beginning of the moult cycle, yet this difference had disappeared at the time of moulting. MDT of zoea I varied between 45 ± 1 days under control conditions and 42 ± 2 days under the highest seawater CO₂ concentration. The present study indicates that larval development under elevated seawater PCO₂ levels results in higher metabolic costs during premoulting events in zoea I. However, H. araneus zoea I larvae seem to be able to compensate for higher metabolic costs as larval MDT and survival was not affected by elevated PCO₂ levels.     

受有色金属密集采矿影响的中国南方某地区鸟类羽毛中重金属、砷和硒的含量

重金属污染在中国非常普遍，特别是在其矿区。最近有报道称贵州省鸟类体内的汞浓度高于有害影响水平，即使是在非矿区也同样如此。我们采集了鸟类样本以调查在广西壮族自治区汞是否是铅矿、锌矿和锡矿附近的潜在威胁因素。我们测定了由60个物种组成的627只本地鸟类羽毛中的8种金属或类金属，这些样本采集于在5条河流的14个位点。。我们发现汞浓度（1.27±2.02ppm）低于最近的贵州研究中报道的浓度。汞与其他金属或类金属的相关性最低，而与开采金属（铅、锡、锌）的相关性最高。镉（1.12±2.64 ppm）、砷（4.78±17.11 ppm）和铅（17.18±24.49 ppm）的浓度水平接近有害效应阈值，或与其他研究相比相对较高。除了汞、镉和砷的几个热点矿区外，金属或类金属水平在矿区之间分布均匀，与可开采矿床的区域分布一致。汞尽管可能危害汞矿附近的一些物种，但似乎并没有威胁到中国所有的鸟类物种。然而，除了汞之外，其他金属或类金属也可能对野生生物的健康造成危害。     

Molecular weight fractionation of dissolved organic matter in coastal seawater by ultrafiltration

Fractionation of molecular weight of dissolved organic matter (DOM) in coastal seawater of Tokyo Bay (Japan) was performed by ultrafiltration. Ultrafiltration membranes Diaflo UM-05, UM-10 and XM-100 were used for DOM fractionation, and dissolved organic carbon (DOC) was determined for ultrafiltrates of each membrane. In surface water of Station 1, near the center of Tokyo Bay, low-molecular weight DOM (molecular weight less than 500) which passed through a Diaflo UM-05 membrane was 0.3 to 2.6 mgC/l (24 to 42% of the total DOC) during August, 1971 to September, 1972. The macromolecular DOM (molecular weight greater than 100,000) retained on an XM-100 membrane, ranged from 0.1 to 1.0 mgC/l. These fractions accounted for 8 to 23% of the total DOC. The precision of the method was within ± 0.1 mgC/l, and therefore may be employed for coastal seawater of high DOC content.     

Effects of the polychlorinated biphenyl Aroclor® 1254 on the American oyster Crassostrea virginica

Young oysters (Crassostrea virginica) were continuously exposed to Aroclor^® 1254, a polychlorinated biphenyl (PCB), in flowing, unfiltered seawater. Growth rate (height and in-water weight) was significantly reduced (=0.05) in oysters exposed to 5 g/l (ppb) for 24 weeks. Growth rate was not affected in oysters exposed to 1 ppb for 30 weeks. Mortality was not significant in exposed and control groups. In oysters exposed to 5 ppb, greatest PCB residue (whole body) was 425 mg/kg (ppm), 85,000x the concentration in the water, and less than 0.3 ppm was retained after 28 weeks depuration in PCB-free water. In oysters exposed to 1 ppb, greatest residue was 101 ppm, 101,000x the concentration in the water, and less than 0.2 ppm was retained after 12 weeks depuration. Examination of oysters exposed to 5 ppb of this PCB for pathogenesis revealed atrophy of digestive diverticular epithelium and degeneration of vesicular connective tissues concomitant with leukocytic infiltration, but tissue recovery seemed excellent after 12 weeks depuration.Registered trademark, Monsanto Company, St. Louis, Missouri, USA. Mention of commercial products or trade names does not constitute endorsement by the Environmental Protection Agency.Contribution No. 146, Gulf Breeze Laboratory.     

Biological production of nitrite in seawater

The relative importance of 3 different sources for biological production of nitrite in seawater was studied. Decomposition of fecal pellets of the copepod Calanus helgolandicus (at a concentration of approximately 12 g-at N/l), in seawater medium, released small amounts of ammonia over a 6 week period. It nitrifying bacteria were added to the fecal pellets nitrite was barely detectable over the same period. Decomposition of phytoplankton (present at a concentration of about 8 g-at particulate plant N/l) with added heterotrophic bacteria, released moderate amounts of ammonia over a 12 week period. If the ammonia-oxidizing bacterium Nitrosocystis oceanus was added to the decomposing algae, nitrite was produced at a rate of 0.2 g-at N/l/week. Heterotrophic nitrification was not observed when 7 open-ocean bacteria were tested for their ability to oxidize ammonia. The diatom Skeletonema costatum, either non-starved or starved of nitrogen, produced nitrite when growing with 150 or 50 g-at NO ₂ ^- -N/l at a light intensity of about 0.01 ly/min. When nitrate in the medium was exhausted, S. costatum assimilated nitrite. If starved of vitamin B₁₂, both non-N-starved and N-starved cells of S. costatum produced nitrite in the medium with 150 g-at NO ₃ ^- -N/l. Nitrate was not exhausted and cell densities reached 2x10⁵/ml due to vitamin B₁₂ deficiency. If light intensity was reduced to 0.003 ly/min under otherwise similar conditions, cells did not grow due to insufficient light, and nitrite was not produced. In the sea, it appears that, in certain micro-environments, decomposition of particulate matter releases ammonia with its subsequent oxidation to nitrite. The amounts of these nutrients and the rate at which they are produced are dependent upon the nature of the materials undergoing decomposition and the associated bacteria. In certain other areas of the sea, where phytoplankton standing stock is high and nitrate is non-limiting, excretion by these organisms is a major source of nitrite.     

Stabilization of the As-contaminated soil from the metal mining areas in Korea

Phytoextraction is a remediation technology with a promising application for removing arsenic (As) from soils and waters. Several plant species were evaluated for their As accumulation capacity in hydroponic culture amended with As. Cucumis sativus (cucumber) displayed the highest tolerance against As among 4 plants tested in this study (corn, wheat, sorghum and cucumber). The germination ratio of Cucumis sativus was more than 50% at the high concentration of 5,000 mg-As/l. In Cucumis sativus grown in a solution contaminated with 25 mg-As/l, the accumulated As concentrations in the shoot and root were 675.5 ± 11.5 and 312.0 ± 163.4 mg/kg, respectively, and the corresponding values of the translocation and bioaccumulation factors for As were 1.9 ± 0.9 and 21.1 ± 8.4, respectively. These results indicate Cucumis sativus is to be a candidate plant for phytoextraction of As from soils and water.     

Total labile carbon in the euphotic zone of the Baltic Sea as measured by BOD

Total labile organic carbon was estimated in the euphotic zone of the Baltic Sea by a method based on the determination of the biological oxygen demand (BOD); the method is extremely simple, requires little sample water, and is quite precise (±4.5 μmol O₂/l or ±40.4 μgC_lab/l). The amount found was 1,150 μgC_lab/l, or about 29% of the total organic carbon. At 1 m, a relationship between biological activity, as measured by chlorophyll content, and the amount of labile carbon was found: ln C_lab (μg/l)=ln 6.87 (μg/l) +0.272 ln chlorophyll (μg/l), with a correlation coefficient of 0.86, which is significantly greater than zero at the 0.001 level.     

Impact of water quality on the stress physiology of cultured Labeo rohita (Hamilton-Buchanan)

Investigation was conducted for 12 months in two water bodies, S1 with optimum water quality and S2 receiving sewage water. The water quality parameters were assessed in relation to the impact on the stress sensitive physiological parameters of fish Labeo rohita. While optimum levels of transparency, dissolved oxygen, unionised ammonia, alkalinity and hardness in S1 reflected in minimum variation of the physiological parameters of L. rohita but suboptimal levels of DO (nil-18.0 mg/l) and CO2 (nil-16.0 mg/l) observed diurnally and unionised ammonia (0.11-0.42 mg/l) found throughout the experimental period, resulted in significant variation in plasma cortisol (90.0-377.0 ng/ml), cholesterol (89.6-285.0 mg/dl) and condition factor (0.7-1.3) in L. rohita. The results are of significance for fish aquatic habitat management.     

Acid–base regulation in the Dungeness crab (Metacarcinus magister)

Homeostatic regulation allows organisms to secure basic physiological processes in a varying environment. To counteract fluctuations in ambient carbonate system speciation due to elevated seawater pCO₂ (hypercapnia), many aquatic crustaceans excrete/accumulate acid–base equivalents through their gills; however, not much is known about the role of ammonia in this response. The present study investigated the effects of hypercapnia on acid–base and ammonia regulation in the Dungeness crab, Metacarcinus magister on the whole animal and isolated gill levels. Hemolymph pCO₂ and [HCO₃ ^?] increased in M. magister acclimated to elevated pCO₂ (330 Pa), while pH remained stable. Additionally, hemolymph [Na⁺], [Ca²⁺], and [SO₄ ^2?] were significantly increased. When challenged with varying pH during gill perfusion, the pH of the artificial hemolymph remained relatively unchanged. Overall, ammonia production and excretion, as well as oxygen consumption, were reduced in crabs acclimated to elevated pCO₂, demonstrating that either (amino acid) oxidation is reduced in response to this particular stress, or nitrogenous wastes are excreted in an alternative form.     

Some effects of hypoxia and medium ammonia enrichment on efflux rates and circulating levels of ammonia inNephrops norvegicus

Eutrophication has been reported for autumn months in regions of the Kattegat/Skagerrak, causing stress to bottom-living organisms. The present studies, undertaken in April (1989), investigated the effects of hypoxia and high ammonia levels in the burrowing decapodNephrops norvegicus (L.). The net ammonia efflux rates and circulating ammonia levels at 6 and 12°C, at normoxia [partial pressure of O₂ in the water (torr),P _wO₂ = 155 torr)] and hypoxiaP _wO₂ = 24 torr) in normal seawater and ammonia-enriched (300µmol ammonia l^–1) seawater were examined. The hourly weight-specific efflux rates were very variable and in all groups included some individuals which showed periods of no net efflux, or even a net uptake of ammonia. At each temperature, net efflux-rate differences due to treatments were not significant (P>0.05; ANOVA, in all cases) and only the differences between the net efflux rates of the normoxic groups were significantly affected by temperature (P<0.05; ANOVA). Circulating ammonia levels were also variable, and at 6°C the ammonia-enriched groups had significantly higher weight-specific blood ammonia content values than the normoxic group (P<0.05 in both cases). A net uptake of ammonia occurred in ammoniaenriched conditions — probably along a reversed NH ₄ ⁺ gradient, as downhill pNH₃ gradients were maintained in all groups — and may represent the only means by which some branchial efflux of ammonia could proceed.     

Impact of total organic carbon and chlorine to ammonia ratio on nitrification in a bench-scale drinking water distribution system

Nitrification occurs in chloraminated drinking water systems and is affected by water quality parameters. The aim of this study was to investigate the impact of total organic carbon and chlorine to ammonia ratio on nitrification potential in a simulated drinking water distribution system as during chloramination. The occurrence of nitrification and activity of nitrifying bacteria was primarily monitored using four rotating annular bioreactors (RAB) with different chlorine to ammonia ratios and total organic carbon (TOC) levels. The results indicated that nitrification occurred despite at a low influent concentration of ammonia, and a high concentration of nitrite nitrogen was detected in the effluent. The study illustrated that reactors 1(R1) and 3 (R3), with higher TOC levels, produced more nitrite nitrogen, which was consistent with the ammonia-oxidizing bacteria (AOB) counts, and was linked to a relatively more rapid decay of chloramines in comparison to their counterparts (R2 and R4). The AOB and HPC counts were correlated during the biofilm formation with the establishment of nitrification. Biofilm AOB abundance was also higher in the high TOC reactors compared with the low TOC reactors. The chlorine to ammonia ratio did not have a significant impact on the occurrence of nitrification. Bulk water with a high TOC level supported the occurrence of nitrification, and AOB development occurred at all examined chlorine to ammonia dose ratios (3:1 or 5:1).     

Arsenic mineralization,source, distribution,and abundance in the Kutahya region of the western Anatolia,Turkey

Environmental exposure to arsenic (As) in the Kutahya region of the western Anatolia, Turkey has been reported to cause various types of arsenic-associated skin disorders (Dogan, Dogan, Celebi, & Baris, 2005). A geological and mineralogical study was conducted to find the sources and distribution of the As. Geogenic (background) levels were measured in samples collected from various sources in the Gediz, Simav, Tavsanli, Emet, Yoncali, Yenicekoy, and Muratdagi areas of the Kutahya region. Based on this analysis, we determined that natural sources are a domineering factor affecting the distribution of As, which was found: (1) mainly in evaporitic minerals, including colemanite (269–3900 ppm) and gypsum (11–99,999 ppm), but also in alunite (7–10 ppm) and chert (54–219 ppm); (2) in secondary epithermal gypsum, which has a high concentration of As in the form of realgar and orpiment along fracture zones of Mesozoic and Cenozoic carbonate aquifers; (3) in rocks, including limestone/dolomite (3–699 ppm) and travertine (5–4736 ppm), which are relatively more enriched in As than volcanics (2–14 ppm), probably because of secondary enrichment through hydrological systems; (4) in coal (1.9–46.5 ppm) in the sedimentary successions of the Tertiary basins; (5) in thermal waters, where As is unevenly distributed at concentrations varying from 0.0–0.9 mg/l. The highest As concentrations in thermal water (Gediz and Simav) correlate to the higher pH (7–9.3) and T (60–83°C) conditions and to the type of water (Na–HCO₃–SO₄ with high concentration of Ca, Mg, K, SiO₂, and Cl in the water). Changes in pH can be related to some redox reactions, such as the cation exchange reactions driving the dissolution of carbonates and silicates. Fe-oxidation, high pH values (7–9.3), presence of other trace metals (Ni, Co, Pb, Zn, Al), increased salinity (Na, Cl), high B, Li, F, and SiO, high Fe, SO₄ (magnetite, specularite-hematite, gypsum), and graphite, and the presence of U, Fe, Cu, Pb, Zn, and B, especially in the Emet, Gediz, and Simav areas, are the typical indicators for the geothermally affected water with high As content. A sixth source of As in this region is the ground (0.0–10.7 mg/l) and the surface waters (0.0022–0.01 mg/l), which are controlled by water–rock interaction, fracture system, and mixing/dilution of thermal waters. The high As concentration in groundwater corresponds to the areas where pathological changes are greatest in the habitants. Arsenic in ground water also effects ecology. For example, only Juriperus oxycedrus and J. varioxycedrus types of vegetation are observed in locations with the highest concentration of As in the region. Branches and roots of these plants are enriched in As.     

Nitrate/nitrite poisoning in dairy cattle associated with consumption of forages irrigated with municipally treated wastewater

Twenty-three cases of nitrate poisoning were diagnosed in a dairy herd due to consumption of green grass, mainly alfalfa, which was irrigated with a municipally treated wastewater. Five cows were found dead and seven fetuses were aborted. Methemoglobin (MtHb) in blood reached 41.6 ± 7.5%, while hemoglobin concentration was low: 6.9 gm dL^–1. Nitrite in plasma was 1.6 ± 0.4 mmol; the levels of nitrate in suspected grass and water were 1.48 × 10³ ppm and 1.7 × 10³ ppm, respectively. The clinical picture included difficulty in breathing, shivering and brown discoloration of the mucous membranes of the vulva, vagina, and conjunctiva. The postmortem findings included dark brown carcasses with dark, nonclotted blood in the dilated vessels. Cardiac hemorrhages, pulmonary and rumen congestion, edema and hyperemia of the mucous membranes of the abomasums and small intestine were noticed in all examined animals. The postmortem examination of aborted fetuses revealed severe ascites and hydrothorax. Affected animals responded well to the treatment with methylene blue. After one week of treatment MtHb and nitrite in plasma were significantly reduced to their minimal levels (10.5% and 0.5 mmol), respectively. One week later, green-feed and water had no evidence of nitrate. A definitive diagnosis was made based on the clinical picture, postmortem findings, high MtHb level in blood, quantitative nitrite analysis of plasma and nitrate analysis of suspected green-grass and response to methylene blue treatment.     

Experimental evidence for internal predation in microzooplankton communities

The fate of microzooplankton production, whether it is channeled to mesozooplankton or recycled within the microbial food web, has major implications for the oceanic carbon cycle. The aim of this study was to estimate internal predation within naturally occurring microzooplankton communities. A dilution series based on the Landry and Hasset technique was created by mixing 200-μm-screened water (used as whole water) with 5-μm-screened seawater due to the dominance of pico- and small nanoplankton at our study site. This modification of the original technique allows for gradual reduction in microzooplankton abundance and thus internal predation while maintaining sufficient phytoplankton prey levels for microzooplankton growth in diluted treatments. Microzooplankton growth and mortality rates were calculated based on the changes in abundance during 24-h incubation. In the diluted treatments, microzooplankton growth rates were significantly higher (1.21 ± 0.20 day^?1 for ciliates and 0.88 ± 0.05 day^?1 for heterotrophic dinoflagellates) compared to those in whole seawater where microzooplankton abundance remained unchanged or even declined over time. Approximately 79 % of microzooplankton production was consumed within the microzooplankton, with aloricate ciliates being the most vulnerable to predation. These findings support the assumption that trophic interactions between microzooplankton can be an important factor controlling their production and, thus, energy transfer in picoplankton-dominated pelagic ecosystems.     

Identification of marine bacteria affecting lithium adsorbents in seawater

Lithium manganese oxide–based adsorbents have been developed for the recovery of lithium from seawater. To maximize the recovery efficiency, it is important to prevent microfouling of lithium adsorbents by marine bacteria. To identify the marine bacteria that cause biofouling against the lithium adsorbents, lithium adsorbents were installed into a non-coated frame or a frame coated with an antifouling agent soaked in seawater. Microorganisms from the surface of lithium adsorbents were collected for 30 days at 10-day intervals, cultured in marine broth, isolated, and identified by 16S rDNA sequencing. Pseudoalteromonas and Vibrio were constituted to 35.6 and 28.8 % of total isolates, respectively, and were predominant in the non-coated frame, whereas Vibrio was poorly isolated (2.3 %) from the antifouling agent–coated frame. In this study, antifouling strategy for maximum lithium recovery efficiency in the marine area takes account of Pseudoalteromonas and Vibrio.     

The effects of a no. 2 fuel oil and two crude oils on the growth and photosynthesis of microalgae

Seawater, when equilibrated with a sample of No. 2 fuel oil, becomes toxic in varying degrees to growth of representative types of microalgae, two blue-greens, a diatom, two greens, and a dinoflagellate. For a sensitive organism such as Thalassiosira pseudonana, Strain 3H, 5 ml of seawater equilibrated with fuel oil (containing 15 mg/l of organics) in 20 ml of growth medium is lethal, or roughly in the range of 40 to 400 ppb if the toxic material(s) constitute 1 to 10% water also immediately stops photosynthesis in organism 3H. For other microalgae tested e.g. 580 (a green alga) and PR-6 (a blue-green alga), similar effects on growth and photosynthesis were found, but required higher concentrations of the oil-equilibrated seawater. Water solubles from Kuwait or Southern Louisiana crude oils (when the straight crude oil was equilibrated 1:8 with seawater) were not toxic; however, specific fractions obtained by distillation did show some water-soluble toxicity. Growth experimetns in open or closed growth systems revealed that most organisms were inhibited by varying amounts of these two crude oils when in direct contact with them. Organism 580 would not grow above 5 μl of Southern Louisiana/25 ml of medium, or 10 μl of Kuwait/25 ml of medium (oil in direct contact with algae). With both the seawater equilibrated with fuel oil and the crude oils, the toxic activity is mainly localized in medium and higher boiling fractions derived from distillation cuts from these materials.     

Photoelectrochemical treatment of ammonium using seawater as a natural supporting electrolyte

In the present study, a photoelectrochemical process containing seawater as a natural low-cost supporting electrolyte was used to remove ammonium from wastewater in a continuous flow mode. Based on central composite design (CCD), response surface methodology (RSM) was employed to evaluate the performance of the process in ammonia removal. The effect of four main independent parameters, including initial ammonium concentration, hydraulic retention time (HRT), current intensity and initial pH on the removal of ammonia was evaluated by the model. The optimal initial ammonium concentration, HRT, current intensity and initial pH were 917 mg NH ₄? N;·L ^?1, 108 min, 1.8 A and 8.4, respectively. The high coefficients (R ²=0.97 and adjusted R ²=0.94) obtained by the analysis of variance (ANOVA) demonstrated close correlation between predicted and experimental values. Also, treating the reject water from the sludge dewatering unit as an ammonium-rich wastewater showed the effectiveness of the process for treating real wastewaters (86% ammonium removal). The results revealed that the present process can be an efficient method for ammonium removal from polluted effluents in coastal areas based on the availability of seawater as a cost-efficient supporting electrolyte.     

Effects of crude oil and chemical dispersant on photosynthesis in the brain coral Diploria strigosa

An eight-hour exposure of Diploria strigosa (Dana) to a mixture of Arabian Light crude oil (19 ppm) and the chemical dispersant “Corexit 9527” (1 ppm) in a flowing seawater system reduced photosynthesis by symbiotic zooxanthellae by 85%, while either oil or dispersant alone had no effect. The greatest effect of crude oil plus dispersant occurred in the incorporation of photosynthetic products into lipids. Synthesis of was esters and triglycerides, the major storage lipids, was particularly affected. Total carbon fixation was restored within 3–5 h after treatment, and lipid synthesis was restored within 5–24 h after exposure.     

Distribution of lipopolysaccharide,an indicator of bacterial biomass,in subtropical areas of the sea

Lipopolysaccharide (LPS) concentrations, an indicator of bacterial biomass, were determined in the South China Sea and the Pacific Ocean. The distribution patterns of LPS were compared with those of chlorophyll a (Chl a), zooplankton biomass and the concentrations of several nutrients. LPS and total bacterial numbers in seawater were correlated with each other with a correlation coefficient (r) of 0.84 at Stations 7, 8 and 10. Diurnal fluctuation of LPS was negligible, but Chl a varied slightly in the vertical water column. Zooplankton stayed at a depth of around 400 m during the daytime and ascended quickly to the surface (0–50 m) early in the evening. The profiles of LPS and Chl a were negatively correlated to each other in the water layers above the Chl a maximum peak (r=-0.74; excluding the samples from 75 m at Station 7 and 10 m at Station 11 due to inadequate data for the statistical analysis). LPS and zooplankton biomass during the night-time, in contrast, paralleled each other at 5 stations surveyed (r=0.71). The presence of zooplankton resulted in an increase in bacterial numbers in the seawater in vitro. Based on these results, the factors controlling the occurrence and abundance of bacteria and phyto- and zooplankton in the pelagic sea are discussed.