Natural Assemblages Of Marine Phytoplankton Research Articles

Remote Sensing-Based Study on the Temporal Variations in Chlorophyll-a Concentration After Confo Oil Spill in Bohai Sea

The satellite-derived chlorophyll-a concentration was used to measure the impact of oil contamination on marine environment after the oil spill on June 4, 2011 in the Bohai Sea. The chlorophyll-a concentration and sea surface temperature was derived from MODIS images with 38.47 % and 7.63 % uncertainty, respectively. The impacts of oil spill on aquatic environments can be divided into three stages: (1) the beginning stage (0–7 weeks), during which the toxicity of other pollutants besides the oil exceeds the tolerance of most algae in the Bohai Sea; (2) the self-repairing stage (7–51 weeks), during which the petroleum hydrocarbon concentration is diluted by the physical and chemical degradation process of aquatic ecology and petroleum hydrocarbon becomes one an important carbon source for algal growth; and (3) long-term toxic affecting stage (>1 year). However, there is currently little knowledge about the long-term toxic effect of oil spill on the natural assemblages of marine phytoplankton. In this study, we determined that the process for delivering nutrients required for algal growth from seabed to water column is slowed by the ‘oil-packaged’ suspended particles above the seabed. These results may be helpful for oil spill response, ecological remediation, and environment monitoring.

Effect of a simulated oil spill on natural assemblages of marine phytoplankton enclosed in microcosms

Two microcosm experiments were carried out to simulate the effect of sporadic oil spills derived from tanker accidents on oceanic and coastal marine phytoplankton assemblages. Treatments were designed to reproduce the spill from the Prestige, which took place in Galician coastal waters (NW Iberia) in November 2002. Two different concentrations of the water soluble fraction of oil were used: low (8.6 ± 0.7 μg l −1 of chrysene equivalents) and high (23 ± 5 μg l −1 of chrysene equivalents l −1). Photosynthetic activity and chlorophyll a concentration decreased in both assemblages after 24–72 h of exposure to the two oil concentrations, even though the effect was more severe on the oceanic assemblage. These variables progressively recovered up to values close or higher than those in the controls, but the short-term negative effect of oil, which was generally stronger at the high concentration, also induced changes in the structure of the plankton community. While the biomass of nanoflagellates increased in both assemblages, oceanic picophytoplankton was drastically reduced by the addition of oil. Effects on diatoms were also observed, particularly in the coastal assemblage. The response of coastal diatoms to oil addition showed a clear dependence on size. Small diatoms (<20 μm) were apparently stimulated by oil, whereas diatoms >20 μm were only negatively affected by the high oil concentration. These differences, which could be partially due to indirect trophic interactions, might also be related to different sensitivity of species to PAHs. These results, in agreement with previous observations, additionally show that the negative effect of the water soluble fraction of oil on oceanic phytoplankton was stronger than on coastal phytoplankton.

Effects of dissolved carbon dioxide, zinc, and manganese on the cadmium to phosphorus ratio in natural phytoplankton assemblages

We report the results of a field study, in productive waters off California, of the factors that control the particulate cadmium (Cd) : phosphorus (P) composition of natural assemblages of marine phytoplankton, the dominant vector of both elements to the deep ocean. Controlled shipboard incubation experiments (;2‐4 d) demonstrated that while manipulation of pCO2 and dissolved zinc (Zn) and manganese (Mn) concentrations had little effect on the species composition or C : nitrogen (N) : P ratios of natural, diatom-dominated phytoplankton assemblages, their Cd : P ratio was negatively correlated to each of these variables. The particulate Cd : P ratios of phytoplankton were two to five times higher for cells grown at low pCO2 than for cells acclimated to growth at pCO2 at or above atmospheric equilibrium values. Addition of Zn to incubations at five- to 20-fold above background concentrations decreased Cd uptake and phytoplankton Cd : P ratios across pCO2 and Mn treatments and suppressed short term Cd uptake rates by a factor of approximately two to four, compared to controls. A broad pattern of Mn suppression of Cd uptake was also evident in our incubations. We propose that natural variability in surface water pCO2 and dissolved Zn and Mn, related to water mass history and biological drawdown, likely govern the degree of Cd uptake and, therefore, the evolution of the dissolved Cd : PO4 ratio in recently upwelled, high-productivity surface waters.

Effect of iron limitation on the cadmium to phosphorus ratio of natural phytoplankton assemblages from the Southern Ocean

There is considerable interest in the biogeochemical cycling of cadmium (Cd) and phosphate (PO4) in surface waters, driven in part by the ongoing development of a paleonutrient proxy that utilizes Cd preserved in fossil planktonic foraminifera to determine past PO4 utilization efficiencies in ocean surface waters. The present article reports the results of a field study into the effects of Fe limitation on the Cd : P composition of natural assemblages of marine phytoplankton in the Antarctic Zone of the Pacific sector of the Southern Ocean. Iron enrichment to shipboard incubation bottles led to increases in community growth rate and final biomass. After 10.7 d of incubation, the climax community was dominated by large diatoms of the genus Fragillariopsis, Pseudonitzschia , and Nitzschia. Direct measurements of phytoplankton metal : P ratios from controlled shipboard experiments indicate that Cd : P, Co: P, and Zn : P ratios decreased from control values with increasing initial dissolved Fe concentrations in the incubation bottles, by factors of ~2–10 at highest Fe additions. We suggest that the effect of Fe limitation on resident diatoms is to decrease growth rate, leading to elevated cellular Cd content. The dissolved Cd : P ratio in iron‐limited surface waters of the Southern Ocean may, therefore, respond to the supply of Fe to the resident phytoplankton community, which has implications for the developing paleonutrient proxy. We suggest that the biological uptake of Cd and P is independent of the dissolved Cd: PO4 ratio. As a consequence, the results argue against the use of empirical Rayleigh fractionation models or models with fixed phytoplankton uptake ratios to account for regional variability in surface water dissolved Cd : PO4.

Patterns of DNA damage and photoinhibition in temperate South-Atlantic picophytoplankton exposed to solar ultraviolet radiation

Natural marine phytoplankton assemblages from Bahı́a Bustamante (Chubut, Argentina, 45°S, 66.5°W), mainly consisting of cells in the picoplankton size range (0.2–2 μm), were exposed to various UVBR (280–315 nm) and UVAR (315–400 nm) regimes in order to follow wavelength-dependent patterns of cyclobutane pyrimidine dimer (CPD) induction and repair. Simultaneously, UVR induced photosynthetic inhibition was studied in radiocarbon incorporation experiments. Biological weighting functions (BWFs) for photoinhibition and for CPD induction, the latter measured in bare calf thymus DNA, differed in the UVAR region: carbon incorporation was reduced markedly due to UVAR, whereas no measurable UVAR effect was found on CPD formation. In contrast, BWFs for inhibition of photosynthesis and CPD accumulation were fairly similar in the UVBR region, especially above 300 nm. Incubation of phytoplankton under full solar radiation caused rapid CPD accumulation over the day, giving maximum damage levels exceeding 500 CPD·MB −1 at the end of the afternoon. A clear daily pattern of CPD accumulation was found, in keeping with the DNA effective dose measured by a DNA dosimeter. In contrast, UVBR induced photosynthetic inhibition was not dose related and remained nearly constant during the day. Screening of UVBR or UVR did not cause significant CPD removal, indicating that photoreactivation either by PAR or UVAR was of minor importance in these organisms. High CPD levels were found in situ early in the morning, which remained unaffected notwithstanding treatments favoring photorepair. These results imply that a proportion of cells had been killed by UVBR exposure prior to the treatments. Our data suggest that the limited potential for photoreactivation in picophytoplankton assemblages from the southern Atlantic Ocean causes high CPD accumulation as a result of UVBR exposure.

Metabolism of neutral monosaccharide constituents of storage and structural carbohydrates in natural assemblages of marine phytoplankton exposed to ultraviolet radiation

We used the 13C tracer technique in conjunction with gas chromatography‐mass spectrometry to examine the impact of ultraviolet radiation (UVR) on the patterns of biosynthesis and composition of monosaccharides in natural assemblages of phytoplankton photoadapting to high light intensities. Exposure to UVR resulted in a decrease in the rates of phytoplankton photosynthesis and a marked reduction in the rates of production and pool sizes of neutral monosaccharides within the storage carbohydrate fraction (operationally defined as carbohydrates soluble in hot water). In contrast, the biosynthesis of neutral monosaccharides associated with cell wall or structural carbohydrates (operationally defined as the fraction of carbohydrates insoluble in hot water) showed an increase in the presence of UVR, which, although marginal, was consistent from station to station. The decline in pool sizes of monosaccharides within the storage carbohydrate fraction was largely responsible for the decline in the overall carbohydrate content of the cells. The diminution in the rates of synthesis and pool sizes of glucose within this fraction represented one of the most significant differences compared to phytoplankton shielded from UVR. In the structural carbohydrate fraction, the synthesis of several component monosaccharides was consistently higher in phytoplankton exposed to UVR.

Iron-mediated effects on nitrate reductase in marine phytoplankton

The potential activity of nitrate reductase was determined in uni-algal cultures in the laboratory and in natural marine phytoplankton assemblages. In the laboratory bioassays, distinct differences in nitrate reductase activity were observed in iron replete versus depleted cultures for Emiliania huxleyi, Isochrysis galbana and Tetraselmis sp. Cells from iron-depleted cultures had 15 to 50 percent lower enzyme activity than those from iron-replete cultures. Upon addition of iron, nitrate reductase activity was enhanced in depleted cells up to levels comparable to those of the replete cells. Bioassays in the northern North Sea conducted in 1993, under low iron conditions, demonstrated similar results. Upon addition of 2.5 nM iron, a distinct enhancement, to a maximum of three times, of nitrate reductase activity was observed within 32 h after addition. Therefore, iron can stimulate nitrate reductase activity. In spite of the clean techniques used, some nitrate reductase activity was always observed. Iron deficiency was shown to impair nitrate reductase activity, but it is unlikely that nitrate reduction would cease completely.

Ecophysiological and Trophic Implications of Light-Stimulated Amino Acid Utilization in Marine Picoplankton

By using microautoradiography, light-stimulated utilization of dissolved amino acids for natural marine phytoplankton assemblages was demonstrated. The <2-mum-size (diameter) picoplankton, known to be a dominant fraction of marine primary production, revealed a widespread capability for this process. Autofluorescent (chlorophyll a-containing) picoplankton and some larger phytoplankton from diverse oceanic locations, as well as isolates of the representative cyanobacterial picoplankton Synechococcus spp. (WH7803, WH8101), showed light-stimulated incorporation of amino acids at trace concentrations. Dark-mediated amino acid utilization was dominated by nonfluorescent bacterial populations. Among autofluorescent picoplankton, light-stimulated exceeded dark-mediated amino acid incorporation by 5 to 75%; light-stimulated amino acid incorporation was only partially blocked by the photosystem II inhibitor 3(3,4-dichloro-phenyl)-1,1-dimethy-lurea (2 x 10 M), suggesting a photoheterotrophic incorporation mechanism. Parallel light versus dark incubations with glucose and mannitol indicated a lack of light-stimulated utilization of these nonnitrogenous compounds. Since marine primary production is frequently nitrogen limited, light-mediated auxotrophic utilization of amino acids and possibly other dissolved organic nitrogen (DON) constituents may represent exploitation of the relatively large DON pool in the face of dissolved inorganic nitrogen depletion. This process (i) increases the efficiency of DON retention at the base of oceanic food webs and (ii) may in part be responsible for relatively high rates of picoplankton production under conditions of chronic dissolved inorganic nitrogen limitation. Picoplanktonic recycling of organic matter via this process has important ramifications with respect to trophic transfer via the "microbial loop."

Photosynthesis-irradiance relationships in polar and temperate phytoplankton populations

Analyses of some 700 photosynthesis-irradiance (P-I) experiments made on natural marine phytoplankton assemblages in over six years of field work are summarized. Observed variations in P-I parameters are discussed in relation to geographical location, sample depth and temporal cycles (diel to interannual). Results suggest that P-I characteristics and therefore regional primary production are largely under physical control; temperature and light appear to be the most important environmental covariables.

Effects of drilling muds and mud additives on the primary production of natural assemblages of marine phytoplankton

The effects of two types of drilling mud and eight mud additives on the primary production of natural assemblages of marine phytoplankton from the Santa Barbara Channel, California, were examined. Exposure for 4 h to BaSO 4 Ca-, Cr- and Fe- lignosulfonate, Drispac (a polyanionic cellulose polymer), X-Pel-G (gilsonite), Soltex (a sulfonated asphalt) and a synthetic reference drilling mud at concentrations ranging over seven orders of magnitude did not significantly alter primary production of phytoplankton relative to untreated controls. A used drilling mud from the Santa Barbara Channel significantly enhanced primary production of phytoplankton exposed for 4 h to mud diluted by a factor of 10 1 to 10 7. Exposure for up to 120 h to low concentrations of BaSO 4, iron-lignosulfonate, paraformaldehyde and both the reference drilling mud and used Santa Barbara mud did not significantly alter primary production. Long-term exposure to Soltex and gilsonite significantly reduced primary production, but only at exposure times considerably longer than would be expected in nature. Drispac enhanced primary production by 50 % after exposure for 120 h to 1 μg liter −1. Phytoplankton composition was not altered by long-term exposure to the muds or additives. These results suggest that, where dilution is rapid, discharge of muds containing the additives studied here would not significantly alter the primary production of natural phytoplankton assemblages in the vicinity of drilling platforms.

The effects of crude oil and Corexit 9527 on marine phytoplankton in an experimental enclosure

The effects of a dispersant, Corexit 9527, plus Prudhoe Bar crude oil and the effects of the dispersant only on natural assemblages of marine phytoplankton in three large experimental ecosystem enclosures (CEEs) were studied. The oil and dispersant were added to a layer between 2 and 4 m depth yielding initial concentrations of 4·5 and 2·0 mg litre −1, respectively. The enclosures remained undisturbed for the 17-day experiment except for sampling at 2- or 3-day intervals. Nutrient concentrations, nitrogen transport rates, chlorophyll a, primary productivity, phytoplankton sinking rates, species composition and cell numbers were followed over the course of the experiment. In the enclosure with oil and dispersant, diatom growth was suppressed and the phytoplankton were dominated by microflagellates such as haptophytes, chrysophytes and a prasinophyte. The diatoms appeared healthy under the microscope and the total number of species was similar species that was affected by the oil. Pennate diatoms, amoebae, zooflagellattes (e.g. bodonids) were more abundant than in the control enclosure. The phytoplankton saccessions in the enclosure receiving only dispersant and in the control enclosure were very similar, but markedly dijferentm from that in the oil-plus-dispersant enclosure. A diatom bloom commenced in both the control and the enclosure receiving only dispersant by day 2 and collapsed by day 11 due to nutrient exhaustion (nitrate and silicate). Nitrate it was not exhausted in the enclosure containing oil and dispersant until the end of the experiment (day 17) and consequently primary productivity and nitrogen transport rates increased with time. This observation is in contrast with the control and dispersant only enclosures were primary productivity and nitrogen transport rates declined dramatically in the middle of the experiment due to the exhaustion of nitrate and silicate.

Photosynthetic response of phytoplankton to light: a physiological model

A theoretical representation is developed for the relationship between photosynthesis and light in phytoplankton, based on a simple model of processes associated with electron flow through photosystem II. Photoinhibition is represented as an impediment to this electron flow. Examples are shown of fits to various typical light saturation curves for natural assemblages of marine phytoplankton. An important parameter is the size of the photosynthetic unit of PSII. This feature facilitates discussion of photoadaptation in terms of changes in the light saturation curves consequent on modifications in the number and/or size of the photosynthetic units.

Effects of some representative petroleum refinery effluent compounds on photosynthesis and growth of natural marine phytoplankton assemblages: Part 1—cresols

The effects of cresols on the photosynthesis and growth of natural marine phytoplankton assemblages from the Scripps Pier at La Jolla, California, USA were measured. In two experiments, in which dinoflagellates were the dominant algae, photosynthesis (measured by 14C uptake) was inhibited at concentrations > 100 μg litre −1 and the concentration giving half-maximal photosynthesis was 10,000 μg litre −1. In a third experiment, in which diatoms were dominant, photosynthesis was not inhibited until levels > 10,000 μg litre −1 were reached and the half-maximal concentration was 20,000 μg litre −1. These experiments suggested that dinoflagellates were more sensitive to cresols than diatoms. However, the reverse was true in an experiment using cultures. In a long-term growth experiment (natural assemblages from the Scripps Pier), only a level of 88,000 μg litre −1 completely inhibited growth. There was a two-day lag in growth at 8500 μg litre −1, but the algae recovered and grew as well as the controls which contained no cresols. This experiment was started with a mixed diatom-dinoflagellate-microflagellate population but only the diatoms grew. High concentrations of cresols (> 900 μg litre −1) resulted in a decrease in the diatom Skeletonema costatum, compared with the controls. Otherwise there was no selection for resistant species. In these experiments, cresols were measured by extraction with methylene chloride from seawater followed by measurement by UV absorption. In all experiments cresol levels decreased with time. This was attributed to uptake by phytoplankton and bacterial degradation.

Effects of simulated upwelling and oligotrophy on chemostat-grown natural marine phytoplankton assemblages

Natural phytoplankton assemblages from the Scripps Pier were grown in two chemostats under conditions that simulated two rates of upwelling followed by oligotrophic conditions. At a moderate upwelling rate ( D = 0.3·day −1) centric diatoms were selected, while at a low rate ( D = 0.1·day −1) a mixture of species dominated. Pumping of low-nutrient water (oligotrophy) resulted in a mixture of species at both rates. Upwelling at a high rate decreased diversity of the crop as compared with the low rate or oligotrophy. These results are compared with those of others who have subjected natural assemblages to continuous culture.

Half-saturation constants for nitrate reductase and nitrate translocation in marine phytoplankton

Half-saturation constants for the NO 3 − dependence of nitrate reductase in natural assemblages of marine phytoplankton ranged from 42 to 201 μM and averaged 82 μM. These values are too large to lend credence to a passive diffusion mechanism of NO 3 − translocation across the plasmalemma. On the contrary, they point to the necessity of a transport mechanism.