Temporal variability of Pb fluxes and bioturbation in shelf sediments beneath the high primary production area off Concepción, central-southern Chile (36°S)

We estimated monthly fluxes of ²¹⁰Pb in shelf sediments beneath a high productivity area off central-southern Chile (36°S) during 1 year (September 2002-August 2003). Sediment cores were obtained using a multiple corer and were analyzed mainly for ²¹⁰Pb, total pigments, and macrofauna abundance. The ²¹⁰Pb inventories and fluxes were estimated for surface sediments (0-5 cm) and bioturbation coefficients were inferred using chlorophyll-a (reactive) profiles. In general, ²¹⁰Pb content was inversely correlated with phytodetritus fluxes. High photosynthetic pigment contents in surface sediments were consistently associated with lower ²¹⁰Pb contents. Macrofaunal activity responded to oxygen and organic matter supplies at the sediment surface, generally concentrated in the first centimeters, but particularly so during months of high organic matter fluxes and deficient bottom water oxygen conditions. At this study site, several processes involved in the ²¹⁰Pb surface distribution make it difficult to accurately estimate ages at the surface. We postulate that the organic fluxes promote changes in the faunal activity, which, in combination with sediment resuspension and water circulation over the shelf, produce seasonal variations in the ²¹⁰Pb inventories.     

Nutrient Limitation in Macroalgae (Ulva and Enteromorpha) from the Rías Baixas (NW Spain)

Abstract.  Photosynthesis and growth rates in samples of two green seaweeds ( Ulva and Enteromorpha ) were monitored in the laboratory. The macroalgae were collected every 15 days from four coastal embayments in Galicia (NW Spain). Ulva samples were found to be nutritionally limited, particularly in summer. The physiological activity of Enteromorpha did not appear to be as affected by nutrient scarcity, although it may have suffered from phosphorus limitation. The subsistence quotas, critical concentrations and storage capacity for N and P in Ulva were comparable to those obtained by other investigators in similar studies. The trace metals analysed apparently did not negatively affect the macroalgae at the measured concentrations; one explanation is that many of these metals function as essential micronutrients. The complex physiological interactions between metals and nutrients, however, may complicate interpretation of the results.     

Benthic photosynthesis in submerged Wadden Sea intertidal flats

In this study we compare benthic photosynthesis during inundation in coarse sand, fine sand, and mixed sediment (sand/mud) intertidal flats in the German Wadden Sea. In situ determinations of oxygen-, DIC- and nutrient fluxes in stirred benthic chamber incubations were combined with measurements of sedimentary chlorophyll, incident light intensity at the sediment surface and scalar irradiance within the sediment. During submergence, microphytobenthos was light limited at all study sites as indicated by rapid response of gross photosynthesis to increasing incident light at the sea floor. However, depth integrated scalar irradiance was 2 to 3 times higher in the sands than in the mud. Consequently, gross photosynthesis in the net autotrophic fine sand and coarse sand flats during inundation was on average 4 and 11 times higher than in the net heterotrophic mud flat, despite higher total chlorophyll concentration in mud. Benthic photosynthesis may be enhanced in intertidal sands during inundation due to: (1) higher light availability to the microphytobenthos in the sands compared to muds, (2) more efficient transport of photosynthesis-limiting solutes to the microalgae with pore water flows in the permeable sands, and (3) more active metabolic state and different life strategies of microphytobenthos inhabiting sands.     

Distributions of dissolved and particulate biogenic thiols in the subartic Pacific Ocean

Dissolved and particulate concentrations of the biogenic thiols cysteine (Cys), arginine–cysteine (Arg–Cys), glutamine–cysteine (Gln–Cys), γ-glutamate–cysteine (γ-Glu–Cys) and glutathione (GSH) were measured in the subartic Pacific Ocean in the summer of 2003 using high performance liquid chromatography (HPLC) with precolumn derivatization as reported in previous work. In this study, a preconcentration protocol for the derivatized thiols was utilized to extend detection limits of dissolved thiols to picomolar levels. The measured concentrations of particulate and dissolved thiols were uncoupled, with distinctive depth profiles and large differences in the particulate to dissolved ratios between individual compounds. Glutathione was the most abundant particulate thiol whereas the most abundant dissolved thiol was γ-Glu–Cys, with concentrations as high as 15 nM. Given the relatively small pool of intracellular γ-Glu–Cys and the very low dissolved concentrations of GSH, we hypothesize that glutathione released from cells is rapidly converted to the potentially degradation resistant γ-Glu–Cys outside the cell. The relatively high concentrations of other dissolved thiols compared to particulate concentrations implies both biological exudation and slow degradation rates. Some thiols appear to vary with changes in nutrient availability but this effect is difficult to decouple from changes in community structure inferred from pigment analyses. Dissolved thiol concentrations also exceed typical metal concentrations in the subartic Pacific, supporting previous arguments that they may be important in metal speciation.     

Spring and summer phytoplankton communities in the Chukchi and Eastern Beaufort Seas

Phytoplankton pigments and size-fractionated biomass in the Chukchi and Beaufort Seas showed spatial and temporal variation during the spring and summer of 2002. Cluster analysis of pigment ratios revealed different assemblages over the shelf, slope and basin regions. In spring, phytoplankton with particle sizes greater than 5 μm, identified as diatoms and/or haptophytes, dominated over the shelf. Smaller (<5 μm) phytoplankton containing chlorophyll b, most likely prasinophytes, were more abundant over the slope and basin. Due to extensive ice cover at this time, phytoplankton experienced low irradiance, but nutrients were near maximal for the year. By summer, small prasinophytes and larger haptophytes and diatoms co-dominated in near-surface assemblages in largely ice-free waters when nitrate was mostly depleted. Deeper in the water column at 1–15% of the surface irradiance larger sized diatoms were still abundant in the upper nutricline. Phytoplankton from the shelf appeared to be advected through Barrow Canyon to the adjacent basin, explaining similar composition between the two areas in spring and summer. Off-shelf advection was much less pronounced for other slope and basin areas, which are influenced by the low-nutrient Beaufort gyre circulation, leading to a dominance of smaller prasinophytes and chlorophytes. The correlation of large-sized fucoxanthin containing phytoplankton with the higher primary production measurements shows promise for trophic status to be estimated using accessory pigment ratios.     

Composition and distribution of phytoplankton with size fraction results at southwestern east/japan sea

Abundance and distribution of phytoplankton in seawater at southwestern East/Japan Sea near Gampo were investigated by HPLC analysis of photosynthetic pigments during summer of 1999. Detected photosynthetic pigments were chlorophyll a, b, c₁₊₂ (Chl a, Chl b, Chl c₁₊₂), fucoxanthin (Fuco), prasinoxanthin (Pras), zeaxanthin (Zea), 19’-butanoyloxyfucoxanthin (But-fuco) and beta-carotene (β-Car). Major carotenoid was fucoxanthin (bacillariophyte) and minor carotenoids were Pras (prasinophyte), Zea (cyanophyte) and But-fuco (chrysophyte). Chl a concentrations were in the range of 0.16-8.3/land subsurface chlorophyll maxima were observed at 0-10m at inshore and 30–50 m at offshore. Thermocline and nutricline tilted to the offshore direction showed a mild upwelling condition. Results from size-fraction showed that contribution from nano+picoplankton at Chl a maximum layer was increased from 18% at inshore to 69% at offshore on average. The maximum contribution from nano+picoplankton was found as 87% at St. E4. It was noteworthy that contribution from nano+picoplanktonic crysophytes and green algae to total biomass of phytoplankton was significant at offshore. Satellite images of sea surface temperature indicated that an extensive area of the East/Japan Sea showed lower temperature (<18 °C) but the enhanced Chl a patch was confined to a narrow coastal region in summer, 1999. Exceptionally high flux of low saline water from the Korea/Tsushima Strait seemed to make upwelling weak in summer of 1999 in the study area. Results of comparisons among Chl a from SeaWIFs, HPLC and fluorometric analysis showed that presence of Chl b cause underestimation of Chl a about 30% by fluorometric analysis but overestimation by satellite data about 30-75% compared to HPLC data.     

The effects of immobilization on physiology and ultrastructure of unicellular alga Platymonas subcordiformis

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几种红藻和蓝藻的光合作用色素

分离纯化出几种海产红藻和一种蓝藻的光合作用色素,并测定了它们的化学性质和光谱学性质。这些藻类是3种红藻:多管藻(Polysiphonia urceolata)、橡叶藻(Phycodrys sp.)和条斑紫菜(Porphyra yezoensis);蓝藻:钝顶螺旋藻(Spirulina platensis)。用羟基磷灰石柱层析法从上述藻类中分离到几种不同的藻胆蛋白。经SDS-PAGE及光谱测定,发现条斑紫菜中的藻红蛋白不同于其它两种红藻。而橡叶藻中存在的两条藻红蛋白也有差异,条斑紫菜和钝顶螺旋藻中的两种别藻蓝蛋白之间也有区别。叶绿素分析表明,钝顶螺旋藻中叶绿素a的含量高于红藻中叶绿素a的含量。     

化合氯对浮游植物对绿素a和光合作用影响的室内研究

化合氯是温排水中主要的化学物质,它的存在会对电厂邻近水域中生活的浮游植物造成一定的影响,运用均匀设计的实验方法研究温度,化合氯浓度,氯处理时间,及这3个因素之间的交互作用,从中筛选出影响叶绿素a含量与光合作用过程的主要因子,结果表明：影响叶绿素a的主要因子是氯处理时间,氯浓度与处理时间之间的交互作用（置信水平为99％）,影响光合作用的主要是氯处理时间,氯浓度,氯处理时间与氯浓度之间的交互作用,以及温度与氯处理时间的交互作用（置换水平为98％）。     

Phytoplankton production in two east coast estuaries: Photosynthesis-light functions and patterns of carbon assimilation in Chesapeake and Delaware Bays

Chesapeake Bay is a large and productive estuary that has received close scrutiny in recent years because of indications that its water quality and biota have been damaged by man's activities. Data on primary production for the estuary as a whole, however, are surprisingly sparse. We describe here the distribution of photosynthetic carbon assimilation by phytoplankton in Chesapeake Bay, and relate productivity patterns to hydrographic characteristics of the estuary. Between March 1982 and April 1983, a series of four cruises was conducted on Chesapeake Bay, and two cruises on the urbanized Delaware Bay for comparison. The upper Chesapeake and Delaware were highly turbid with high concentrations of suspended particulate matter and dissolved inorganic nutrients. Low chlorophyll concentrations were usually found in these areas of high turbidity, despite the abundance of nutrients, suggesting light limitation. Application of Wofsy's (1983) model of phytoplanton growth confirmed this suggestion. Chlorophyll and productivity maxima usually occurred seaward of the turbidity maxima where light penetration increased and suffient nutrients were present to support active phytoplankton growth. Further seaward of the chlorophyll maxima in the Chesapeake, the photic zone depth increased, concentrations of nutrients decreased, and phytoplankton biomass decreased, suggesting that nutrient availability, rather than light, controlled phytoplankton growth in the lower portion of the estuary. In contrast to the Chesapeake, Delaware Bay was more turbid, had generally higher nutrient concentrations, and was lower in phytoplankton productivity. The chlorophyll maxima and region of rapid phytoplankton growth occurred further toward the lower estuary and shelf regions in Delaware Bay because the high turbidity extended further seaward. Nutrients were never depleted at the shelf end of the estuary sufficiently to retard phytoplankton growth. Photosynthesis-irradiance (P-I) curves from simulated in situ and constant intensity incubations showed a strong correlation of the light-limited slope (a^B) with the light-saturated rate ( ) on each cruise. Spatial variations in corresponded to patterns of phytoplankton abundance, as did integral production (PP) and carbon-based growth rates (μ_C, μ_m), and photosynthetic parameters varied significantly with temperature.