Aridgides, LJ, Doblin, MA, Berke, T, Dobbs, FC, Matson, DO & Drake, LA 2004, 'Multiplex PCR allows simultaneous detection of pathogens in ships' ballast water', MARINE POLLUTION BULLETIN, vol. 48, no. 11-12, pp. 1096-1101.
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There is enormous potential for global transfer of microorganisms, including pathogens, in ships' ballast water. We contend that a major advancement in the study of ballast-water microorganisms in particular, and of aquatic pathogens in general, will be expedited sample analysis, such as provided by the elegant technology of DNA microarrays. In order to use DNA microarrays, however, one must establish the appropriate conditions to bind target sequences in samples to multiple probes on the microarrays. We conducted proof-of-concept experiments to optimize simultaneous detection of multiple microorganisms using polymerase chain reaction (PCR) and Southern hybridization. We chose three target organisms, all potentially found in ballast water: a calicivirus, the bacterium Vibrio cholerae, and the photosynthetic protist Aureococcus anophagefferens. Here, we show simultaneous detection of multiple pathogens is possible, a result supporting the promising future use of microarrays for simultaneous detection of pathogens in ballast water.
Baines, SB, Fisher, NS, Doblin, MA, Cutter, GA, Cutter, LS & Cole, B 2004, 'Light dependence of selenium uptake by phytoplankton and implications for predicting selenium incorporation into food webs', LIMNOLOGY AND OCEANOGRAPHY, vol. 49, no. 2, pp. 566-578.
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The potentially toxic element selenium is first concentrated from solution to a large but highly variable degree by algae and bacteria before being passed on to consumers. The large loads of abiotic and detrital suspended particles often present in rivers and estuaries may obscure spatial and temporal patterns in Se concentrations at the base of the food web. We used radiotracers to estimate uptake of both selenite (Se(IV)) and C by intact plankton communities at two sites in the Sacramento/San Joaquin River Delta. Our goals were to determine (1) whether C and Se(IV) uptake were coupled, (2) the role of bacteria in Se(IV) uptake, and (3) the Se:C uptake ratio of newly produced organic material. Se(IV) uptake, like C uptake, was strongly related to irradiance. The shapes of both relationships were very similar except that at least 42-56% of Se(IV) uptake occurred in the dark, whereas C uptake in the dark was negligible. Of this dark Se(IV) uptake, 34-67% occurred in the 0.2-1.0-μm size fraction, indicating significant uptake by bacteria. In addition to dark uptake, total Se(IV) uptake consisted of a light-driven component that was in fixed proportion to C uptake. Our estimates of daily areal Se(IV):C uptake ratios agreed very well with particulate Se:C measured at a site dominated by phytoplankton biomass. Estimates of bacterial Se:C were 2.4-13 times higher than for the phytoplankton, suggesting that bacteriovores may be exposed to higher dietary Se concentrations than herbivores.
Chen, M, Zeng, H, Larkum, AWD & Cai, Z-L 2004, 'Raman properties of chlorophyll d, the major pigment of Acaryochloris marina: studies using both Raman spectroscopy and density functional theory', Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, vol. 60, no. 3, pp. 527-534.
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The Raman spectroscopy of purified chlorophyll (Chl) d extracted from Acaryochloris marina has been measured over the wide region of 250-3200 cm -1 at 77 K following excitation of its Soret band at 488 nm and analyzed with the aid of hybrid density-functional vibrational analyses. A Raman peak specific to Chl d, which arises from the formyl group 31 C = O stretching, was clearly observed at 1659 cm-1 with medium intensity. Peaks due to other C = O stretching vibrations of the 131 keto-, 133 ester- and 173 groups were also observed. Four very strong peaks were observed in the range of 1000-1600 cm-1, assigned to the CC stretching and mixtures of the CH3 bend and CN stretching. CCC and NCC bending contribute to medium intensity peaks at 986 and 915 cm-1. Out-of-plane CH bending at Chl d methine sites 10, 5 and 20 contribute to observed peaks at 885, 864 and 853 cm-1, respectively. A few modes involving the MgN stretching and MgNC bending motions were observed in the very low frequency range. Density functional theory (DFT) calculations have been used to make assignments on the observed Raman spectrum and the DFT results have been found to be in good agreement with the experimental results. © 2003 Elsevier B.V. All rights reserved.
Doblin, MA, Popels, LC, Coyne, KJ, Hutchins, DA, Cary, SC & Dobbs, FC 2004, 'Transport of the harmful bloom alga Aureococcus anophagefferens by oceangoing ships and coastal boats', APPLIED AND ENVIRONMENTAL MICROBIOLOGY, vol. 70, no. 11, pp. 6495-6500.
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It is well established that cyst-forming phytoplankton species are transported in ships' ballast tanks. However, there is increasing evidence that other phytoplankton species which do not encyst are also capable of surviving ballast transit. These species have alternative modes of nutrition (hetero- or mixotrophy) and/or are able to survive long-term darkness. In our studies of no-ballast-on-board vessels arriving in the Great Lakes, we tested for the presence of the harmful algal bloom species Aureococcus anophagefferens (brown tide) in residual (i.e., unpumpable) ballast water using methods based on the PCR. During 2001, the brown tide organism was detected in 7 of 18 ballast water tanks in commercial ships following transit from foreign ports. Furthermore, it was detected after 10 days of ballast tank confinement during a vessel transit in the Great Lakes, a significant result given the large disparity between the salinity tolerance for active growth of Aureococcus (>22 ppt) and the low salinity of the residual ballast water (similar to2 ppt). We also investigated the potential for smaller, recreational vessels to transport and distribute Aureococcus. During the summer of 2002, 11 trailered boats from the inland bays of Delaware and coastal bays of Maryland were sampled. Brown tide was detected in the bilge water in the bottoms of eight boats, as well as in one live-well sample. Commercial ships and small recreational boats are therefore implicated as potential vectors for long-distance transport and local-scale dispersal of Aureococcus.
Hill, R, Larkum, AWD, Frankart, C, Kuhl, M & Ralph, PJ 2004, 'Loss of functional Photosystem II reaction centres in zooxanthellae of corals exposed to bleaching conditions: using fluorescence rise kinetics', PHOTOSYNTHESIS RESEARCH, vol. 82, no. 1, pp. 59-72.
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Hill, R, Schreiber, U, Gademann, R, Larkum, AWD, Kuhl, M & Ralph, PJ 2004, 'Spatial heterogeneity of photosynthesis and the effect of temperature-induced bleaching conditions in three species of corals', MARINE BIOLOGY, vol. 144, no. 4, pp. 633-640.
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Heterogeneity in photosynthetic performance between polyp and coenosarc tissue in corals was shown using a new variable fluorescence imaging system (Imaging-PAM) with three species of coral, Acropora nobilis, Cyphastrea serailia and Pocillopora damicornis. In comparison to earlier studies with fibre-optic microprobes for fluorescence analysis, the Imaging-PAM enables greater accuracy by allowing different tissues to be better defined and by providing many more data points within a given time. Spatial variability of photosynthetic performance from the tip to the distal parts was revealed in one species of branching coral, A. nobilis. The effect of bleaching conditions (33°C vs. 27°C) was studied over a period of 8 h. Marked changes in fluorescence parameters were observed for all three species. Although a decline in ΦPSII (effective quantum yield) and Yi (the first effective quantum yield obtained from a rapid light curve) were observed, P. damicornis showed no visual signs of bleaching on the Imaging-PAM after this time. In A. nobilis and C. serailia, visual signs of bleaching over the 8 h period were accompanied by marked changes in F (light-adapted fluorescence yield), NPQ (non-photochemical quenching) and Ek (minimum saturating irradiance), as well as ΦPSII and Yi. These changes were most marked over the first 5 h. The most sensitive species was A. nobilis, which after 8 h at 33°C had reached a ΦPSII value of almost zero across its whole surface. Differential bleaching responses between polyps and coenosarc tissue were found in P. damicornis, but not in A. nobilis and C. serailia. NPQ increased with exposure time to 33°C in both the latter species, accompanied by a decreasing Ek, suggesting that the xanthophyll cycle is entrained as a mechanism for reducing the effects of the bleaching conditions. © Springer-Verlag 2004.
Jermiin, LS, Ho, SYW, Ababneh, F, Robinson, J & Larkum, AWD 2004, 'The Biasing Effect of Compositional Heterogeneity on Phylogenetic Estimates May be Underestimated', Systematic Biology, vol. 53, no. 4, pp. 638-643.
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Macinnis-Ng, CMO & Ralph, PJ 2004, 'In situ impact of multiple pulses of metal and herbicide on the seagrass, Zostera capricorni', AQUATIC TOXICOLOGY, vol. 67, no. 3, pp. 227-237.
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Tides and freshwater inflow which influence water movement in estuarine areas govern the exposure-regime of pollutants. In this experiment, we examined the in situ impact of double pulses of copper and the herbicide Irgarol 1051 on the photosynthesis of the seagrass, Zostera capricorni. Despite a 4-day recovery period between the two 10h pulses of toxicant, the effective quantum yield of photosystem II (ΔF/Fm′) and total chlorophyll concentrations indicated that multiple-pulses had a greater impact than a single pulse. During the first exposure period, samples exposed to Irgarol 1051 had ΔF/Fm′ values as low as zero while controls remained around 0.6 relative units. After the second exposure period, treated samples recovered to only 0.4 relative units. Samples exposed to copper had ΔF/Fm′ values around 0.3 relative units during the first exposure period and while these samples recovered before the second dose, they remained below 0.2 relative units after the second exposure period. Alternate samples were also exposed to one toxicant, allowed to recover and then exposed to the other toxicant. ΔF/Fm′ values indicated that copper exposure followed by Irgarol 1051 exposure was more toxic than Irgarol 1051 exposure followed by copper exposure. © 2004 Elsevier B.V. All rights reserved.
MacIntyre, HL, Lomas, MW, Cornwell, J, Suggett, DJ, Gobler, CJ, Koch, EW & Kana, TM 2004, 'Mediation of benthic–pelagic coupling by microphytobenthos: an energy- and material-based model for initiation of blooms of Aureococcus anophagefferens', Harmful Algae, vol. 3, no. 4, pp. 403-437.
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We present a conceptual model for initiation of blooms of the estuarine brown-tide pelagophyte Aureococcus anophagefferens. The model is based on the observation that in addition to its well-documented stimulation by organic nutrients, Aureococcus is pie
Runcie, JW, Ritchie, RJ & Larkum, AWD 2004, 'Uptake kinetics and assimilation of phosphorus by Catenella nipae and Ulva lactuca can be used to indicate ambient phosphate availability', Journal of Applied Phycology, vol. 16, no. 3, pp. 181-194.
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Uptake, assimilation and compartmentation of phosphate were studied in the opportunist green macroalgaUlva lactucaand the estuarine red algal epiphyteCatenella nipae. The MichaelisMenten model was used to describe uptake rates of inorganic phosphate (Pi) at different concentrations. Maximum uptake rates (V max) of P-starved material exceededV maxof P-enriched material; this difference was greater forC. nipae. Uptake and allocation of phosphorus (P) to internal pools was measured using trichloroacetic acid (TCA) extracts and32P. Both species demonstrated similar assimilation paths: when P-enriched, most32P accumulated as free phosphate. When unenriched,32P was rapidly assimilated into the TCA-insoluble pool.C. nipaeconsistently assimilated more32P into this pool thanU. lactuca, indicatingC. nipaehas a greater P-storage capacity. In both species,32P release data showed two internal compartments with very different biological half-lives.
Ryan, KG, Ralph, P & McMinn, A 2004, 'Acclimation of Antarctic bottom-ice algal communities to lowered salinities during melting', POLAR BIOLOGY, vol. 27, no. 11, pp. 679-686.
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Sea-ice brine algal communities were exposed to salinities between 30 and 10‰ during melting. There was a progressive decline in maximum quantum yield, relative electron transfer rate (rETRmax) and photosynthetic efficiency (α) with decreasing salinity of the final melted sample. While all species showed a drop in these parameters, Fragilariopsis curta and Entomoneis kjellmannii showed the least inhibition. There was a steady increase in rETRmax and alpha; over 5 days after melting, especially in the samples melted into the highest salinities. In addition, the samples melted from the ice without added filtered seawater showed no photosynthetic activity after 2 days. Our results suggest that for experimental work using sea-ice microalgae, the final salinity of the melted sample should be greater than 28‰ (i.e. the ratio of sea ice to filtered seawater should be at least 1:2). © Springer-Verlag 2004.
Seymour, JR, Mitchell, JG & Seuront, L 2004, 'Microscale heterogeneity in the activity of coastal bacterioplankton communities', AQUATIC MICROBIAL ECOLOGY, vol. 35, no. 1, pp. 1-16.
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Microscale sampling techniques and flow cytometry were employed to measure the distribution patterns of 8 subpopulations of bacteria separated according to variations in cell fluorescence and light scatter properties. Subpopulations of bacteria defined on the basis of these parameters have recently been shown to represent cells exhibiting dissimilar activity levels, and we therefore assume that the subpopulations of bacteria identified here represent metabolically diverse groups. Microscale distribution patterns of these subpopulations were measured at a resolution of 4.5 and 12 mm, within 2 dissimilar coastal habitats, A mean 2-fold change in the abundance of the total bacterial community across sample sets was observed. However, levels of spatial heterogeneity were consistently higher for the cytometrically defined subpopulations than total counts. In most samples, the population of bacteria exhibiting the highest levels of green fluorescence, or DNA content, and hence assumed to represent the most active bacteria in the community, also showed the highest levels of microscale spatial variability, with a maximum change in abundance of 14.5-fold observed across a distance of 9 nun. Where Zipf rank-size analysis was conducted, the microscale distributions of subpopulations differed significantly (p < 0.05) in 79% of cases, implying that bacterial communities are made up of physiologically distinct compartments, perhaps influenced by different microscale features of the environment. We suggest that these results provide the first evidence for the existence of microscale heterogeneity in the metabolic activity of aquatic bacterial communities.
Siboni, N, Fine, M, Bresler, V & Loya, Y 2004, 'Coastal coal pollution increases Cd concentrations in the predatory gastropod Hexaplex trunculus and is detrimental to its health', MARINE POLLUTION BULLETIN, vol. 49, no. 1-2, pp. 111-118.
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Stewart, AR, Luoma, SN, Schlekat, CE, Doblin, MA & Hieb, KA 2004, 'Food web pathway determines how selenium affects aquatic ecosystems: A San Francisco Bay case study', ENVIRONMENTAL SCIENCE & TECHNOLOGY, vol. 38, no. 17, pp. 4519-4526.
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Chemical contaminants disrupt ecosystems, but specific effects may be under-appreciated when poorly known processes such as uptake mechanisms, uptake via diet, food preferences, and food web dynamics are influential. Here we show that a combination of food web structure and the physiology of trace element accumulation explain why some species in San Francisco Bay are threatened by a relatively low level of selenium contamination and some are not. Bivalves and crustacean zooplankton form the base of two dominant food webs in estuaries, The dominant bivalve Potamocorbula amurensis has a 10-fold slower rate constant of loss for selenium than do common crustaceans such as copepods and the mysid Neomysis mercedis (rate constant of loss, k(e) = 0.025, 0.155, and 0.25 d(-1), respectively). The result is much higher selenium concentrations in the bivalve than in the crustaceans. Stable isotope analyses show that this difference is propagated up the respective food webs in San Francisco Bay. Several predators of bivalves have tissue concentrations of selenium that exceed thresholds thought to be associated with teratogenesis or reproductive failure (liver Se > 15 mug g(-1) dry weight). Deformities typical of selenium-induced teratogenesis were observed in one of these species. Concentrations of selenium in tissues of predators of zooplankton are less than the thresholds. Basic physiological and ecological processes can drive wide differences in exposure and effects among species, but such processes are rarely considered in traditional evaluations of contaminant impacts.
Suggett, DJ, MacIntyre, HL & Geider, RJ 2004, 'Evaluation of biophysical and optical determinations of light absorption by photosystem II in phytoplankton', Limnology and Oceanography: Methods, vol. 2, no. 10, pp. 316-332.
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Fast repetition rate (FRR) fluorescence can provide highly resolved estimates of light absorption by photosystem II (PSII), a variable that is critical to bio‐optical determinations of phytoplankton productivity. We compared estimates of chlorophyll a‐specific light absorption by PSII, achlPSII, using both biophysical (FRR) and optical (chlorophyll a‐specific light absorption coefficient, achl) techniques on cultures of phytoplankton from diverse taxa. Biophysical determinations of achlPSII were obtained from the product of the effective light absorption cross‐section of PSII (σPSII), measured by FRR fluorescence, and the ratio of PSII reaction centers to chlorophyll a (nPSII), measured by oxygen flash yields. Both parameters were highly variable between individual taxa. In mixtures of algae, the estimates of σPSII were largely determined by the taxon that dominated fluorescence intensity. Independent optical estimates of achlPSII were obtained by weighting the light absorption spectra of photosynthetic pigments by the fluorescence excitation spectra. The biophysical and optical estimates of achlPSII were highly correlated (r2 = 0.94) with a slope that was not significantly different from 1 and an intercept of 0. Estimates of productivity using biophysical or optical absorption measurements should therefore be comparable when the latter are adjusted to account for the proportion of light provided for photochemistry into both photosystem I ...
