Stephen B. Baines

The Trace Metal Composition of Marine Phytoplankton

Trace metals are required for numerous processes in phytoplankton and can influence the growth and structure of natural phytoplankton communities. The metal contents of phytoplankton reflect biochemical demands as well as environmental availability and influence the distribution of metals in the ocean. Metal quotas of natural populations can be assessed from analyses of individual cells or bulk particle assemblages or inferred from ratios of dissolved metals and macronutrients in the water column. Here, we review the available data from these approaches for temperate, equatorial, and Antarctic waters in the Pacific and Atlantic Oceans. The data show a generalized metal abundance ranking of Fe≈Zn>Mn≈Ni≈Cu≫Co≈Cd; however, there are notable differences between taxa and regions that inform our understanding of ocean metal biogeochemistry. Differences in the quotas estimated by the various techniques also provide information on metal behavior. Therefore, valuable information is lost when a single metal stoichiometry is assumed for all phytoplankton.

SYNCHRONOUS BEHAVIOR OF TEMPERATURE, CALCIUM, AND CHLOROPHYLL IN LAKES OF NORTHERN WISCONSIN

The degree to which a variables dynamics are synchronized among a set of neighboring lakes indicates the relative influence of regional climate variability. Furthermore, by determining which lakes tend to be most synchronous in their response to climate we can deduce the primary ways that climate influences the dynamics of the variable in question. In this study, we look for evidence of synchrony in the temperature, calcium, and chlorophyll dynamics of seven neighboring northern Wisconsin lakes. Our goals were to assess the influence of climate on dynamics of these variables and the effect of lake basin properties on their response to climate signals. Synchrony was measured as the r2 value from a regression relating observations of a variable in one lake against simultaneous observations of the same variable in another. Temperature was the most synchronous variable, with all pairs displaying significant synchrony. Calcium was also highly synchronous, with 15 of the 21 lake pairs exhibiting significant sy...

Sampling Larval Fish Populations: Choice of Sample Number and Size

Abstract The number and size of larval fish samples are usually determined arbitrarily, despite the influence of these decisions on the precision of abundance estimates and the ability to detect differences among population estimates. Review of the literature suggests that most surveys of larval fish are based on few (median, 4), large (median, 300 m3) samples. To evaluate current sampling designs, we developed a model, based on published data, to predict the variance in larval fish abundance among replicate samples. Inter-replicate variance (s 2) is strongly related to mean abundance (x) as: log10 s 2 = 0.19 + 1.74·log10 x; r 2 = 0.93, P < 0.0001. This relationship was tested with an extensive data set collected in the Hudson River, New York (weekly samples over 14 years in 12 regions of the 250-km-long river), and was found to be general across environments, life history stages, and species. The model was not affected by sample volume, Our analysis shows that half of published studies estimated larval a...

Quantitative 3D elemental microtomography of Cyclotella meneghiniana at 400-nm resolution

X-ray fluorescence tomography promises to map elemental distributions in unstained and unfixed biological specimens in three dimensions at high resolution and sensitivity, offering unparalleled insight in medical, biological, and environmental sciences. X-ray fluorescence tomography of biological specimens has been viewed as impractical—and perhaps even impossible for routine application—due to the large time required for scanning tomography and significant radiation dose delivered to the specimen during the imaging process. Here, we demonstrate submicron resolution X-ray fluorescence tomography of a whole unstained biological specimen, quantifying three-dimensional distributions of the elements Si, P, S, Cl, K, Ca, Mn, Fe, Cu, and Zn in the freshwater diatom Cyclotella meneghiniana with 400-nm resolution, improving the spatial resolution by over an order of magnitude. The resulting maps faithfully reproduce cellular structure revealing unexpected patterns that may elucidate the role of metals in diatom biology and of diatoms in global element cycles. With anticipated improvements in data acquisition and detector sensitivity, such measurements could become routine in the near future.

Mighty small: Observing and modeling individual microbes becomes big science

Progress in microbiology has always been driven by technological advances, ever since Antonie van Leeuwenhoek discovered bacteria by making an improved compound microscope. However, until very recently we have not been able to identify microbes and record their mostly invisible activities, such as nutrient consumption or toxin production on the level of the single cell, not even in the laboratory. This is now changing with the rapid rise of exciting new technologies for single-cell microbiology (1, 2), which enable microbiologists to do what plant and animal ecologists have been doing for a long time: observe who does what, when, where, and next to whom. Single cells taken from the environment can be identified and even their genomes sequenced. Ex situ, their size, elemental, and biochemical composition, as well as other characteristics can be measured with high-throughput and cells sorted accordingly. Even better, individual microbes can be observed in situ with a range of novel microscopic and spectroscopic methods, enabling localization, identification, or functional characterization of cells in a natural sample, combined with detecting uptake of labeled compounds. Alternatively, they can be placed into fabricated microfluidic environments, where they can be positioned, exposed to stimuli, monitored, and their interactions controlled “in microfluido.” By introducing genetically engineered reporter cells into a fabricated landscape or a microcosm taken from nature, their reproductive success or activity can be followed, or their sensing of their local environment recorded.

Quantification of phosphorus in single cells using synchrotron X-ray fluorescence

Phosphorus abundance was quantified in individual phytoplankton cells by synchrotron X-ray fluorescence and compared with bulk spectrophotometric measurements to confirm accuracy of quantification. Figures of merit for P quantification on three different types of transmission electron microscopy grids are compared to assess possible interferences.

Exploring ocean biogeochemistry by single-cell microprobe analysis of protist elemental composition.

ABSTRACT. The biogeochemical cycles of many elements in the ocean are linked by their simultaneous incorporation into protists. In order to understand these elemental interactions and their implications for global biogeochemical cycles, accurate measures of cellular element stoichiometries are needed. Bulk analysis of size‐fractionated particulate material obscures the unique biogeochemical roles of different functional groups such as diatoms, calcifying protists, and diazotrophs. Elemental analysis of individual protist cells can be performed using electron, proton, and synchrotron X‐ray microprobes. Here we review the capabilities and limitations of each approach and the application of these advanced techniques to cells collected from natural communities. Particular attention is paid to recent studies of plankton biogeochemistry in low‐iron waters of the Southern Ocean. Single‐cell analyses have revealed significant inter‐taxa differences in phosphorus, iron, and nickel quotas. Differences in the response of autotrophs and heterotrophs to iron fertilization were also observed. Two‐dimensional sub‐cellular mapping indicates the importance of iron to photosynthetic machinery and of zinc to nuclear organelles. Observed changes in diatom silicification and cytoplasm content following iron fertilization modify our understanding of the relationship between iron availability and silicification. These examples demonstrate the advantages of studying ocean biogeochemistry at the level of individual cells.

Effects of wetland plants on denitrification rates: a meta‐analysis

Human activity is accelerating changes in biotic communities worldwide. Predicting impacts of these changes on ecosystem services such as denitrification, a process that mitigates the consequences of nitrogen pollution, remains one of the most important challenges facing ecologists. Wetlands especially are valued as important sites of denitrification, and wetland plants are expected to have differing effects on denitrification. We present the results of a meta-analysis, conducted on 419 published estimates of denitrification in wetlands dominated by different plant species. Plants increased denitrification rates by 55% on average. This effect varied significantly among communities as defined by the dominant plant species, but surprisingly did not differ substantially among methods for measuring denitrification or among types of wetlands. We conclude that mechanistically linking functional plant traits to denitrification will be key to predicting the role of wetlands in nitrogen mitigation in a changing world.

Effects of invasive-plant management on nitrogen-removal services in freshwater tidal marshes.

Establishing relationships between biodiversity and ecosystem function is an ongoing endeavor in contemporary ecosystem and community ecology, with important practical implications for conservation and the maintenance of ecosystem services. Removal of invasive plant species to conserve native diversity is a common management objective in many ecosystems, including wetlands. However, substantial changes in plant community composition have the potential to alter sediment characteristics and ecosystem services, including permanent removal of nitrogen from these systems via microbial denitrification. A balanced assessment of costs associated with keeping and removing invasive plants is needed to manage simultaneously for biodiversity and pollution targets. We monitored small-scale removals of Phragmites australis over four years to determine their effects on potential denitrification rates relative to three untreated Phragmites sites and adjacent sites dominated by native Typha angustifolia. Sediment ammonium increased following the removal of vegetation from treated sites, likely as a result of decreases in both plant uptake and nitrification. Denitrification potentials were lower in removal sites relative to untreated Phragmites sites, a pattern that persisted at least two years following removal as native plant species began to re-colonize treated sites. These results suggest the potential for a trade-off between invasive-plant management and nitrogen-removal services. A balanced assessment of costs associated with keeping versus removing invasive plants is needed to adequately manage simultaneously for biodiversity and pollution targets.