Nutrient flux in the Rhode River: Tidal transport of microorganisms in brackish marshes

Concentrations of bacteria, chlorophyll a, and several dissolved organic compounds were determined during 11 tidal cycles throughout the year in a high and a low elevation marsh of a brackish tidal estuary. Mean bacterial concentrations were slightly higher in flooding (7·1 × 106 cells ml-1) than in ebbing waters (6·5 × 106 cells ml-1), and there were no differences between marshes. Mean chlorophyll a concentrations were 36·7 µg 1-1 in the low marsh and 20·4 µg 1-1 in the high marsh. Flux calculations, based on tidal records and measured concentrations, suggested a small net import of bacterial and algal biomass into both marshes. Over the course of individual tidal cycles, concentrations of all parameters were variable and not related to tidal stage. Heterotrophic activity measured by the uptake of 3H-thymidine, was found predominantly in the smallest particle size fractions ( <1·0 pin). Thymidine uptake was correlated with temperature (r=0·48, P<0·01), and bacterial productivity was estimated to be 7 to 42 µg C l-1 day-1

Use of fluorescently labelled algae (FLA) to estimate microzooplankton grazing

The fluorescent dye 5-(4,6-dichlorotriazin-2-yla)m inofluorescein (DTAF) was used to label a small alga (Nannochloris sp.), following the protocol of Sherr et al. (1987). A rotifer (Brachionus sp.) and a small ciliate (Euplotes sp.) ingested the fluorescently labelled algae (FLA) and demonstrated saturation kinetics. A small tintinnid ingested the FLA at rates intermediate to those of the rotifer and ciliate. Fluorescent labelling of algae is a promising technique that may be used for estimating grazing rates in a manner analogous to that discribed by Sherr et al. (1987) using fluorescently labelled bacteria (FLB)

Development and applications of microbial ecogenomic indicators for monitoring water quality: Report of a workshop assessing the state of the science, research needs and future directions

This article brings forth recommendations from a workshop sponsored by the U.S. Environmental Protection Agency?s Science to Achieve Results (STAR) and Environmental Monitoring and Assessment (EMAP) Programs and by the Council of State Governments, held during May 2002 in Kansas City, Kansas. The workshop assembled microbial ecologists and environmental scientists to determine what research and science is needed to bring existing molecular biological approaches and newer technologies arising from microbial genomic research into environmental monitoring and water quality assessments. Development of genomics and proteomics technologies for environmental science is a very new area having potential to improve environmental water quality assessments. The workshop participants noted that microbial ecologists are already using molecular biological methods well suited for monitoring and water quality assessments and anticipate that genomics-enabled technologies could be made available for monitoring within a decade. Recommendations arising from the workshop include needs for (i) identification of informative microbial gene sequences, (ii) improved understandings of linkages between indicator taxa, gene expression and environmental condition, (iii) technological advancements towards field application, and (iv) development of the appropriate databases

Community structure and bottom-up regulation of heterotrophic microplankton in arctic LTER lakes

Microplankton community structures and abundance was assessed in lakes at the Toolik Lake LTER site in northern Alaska during the summers of 1989 and 1990. The microplankton community included oligotrich ciliates, but rotifers and zooplankton nauplii comprised greater than 90% of total estimated heterotrophic microplankton biomass. Dominant rotifer taxa included Keratella cochlearis, Kellicottia longispina, Polyarthra vulgaris, Conochilus unicornis and a Synchaeta sp. Microplankton biomass was lowest in highly oligotrophic Toolik Lake ( < 5 µgC 1-1 at the surface) and highest (up to 55 µgC 1-1) in the most eutrophic lakes, experimentally fertilized lakes, and fertilized limnocorrals, consistent with bottom-up regulation of microplankton abundance

Development of Real-Time PCR Assays for Rapid Detection of Pfiesteria piscicida and Related Dinoflagellates

Pfiesteria complex species are heterotrophic and mixotrophic dinoflagellates that have been recognized as harmful algal bloom species associated with adverse fish and human health effects along the East Coast of North America, particularly in its largest (Chesapeake Bay in Maryland) and second largest (Albermarle-Pamlico Sound in North Carolina) estuaries. In response to impacts on human health and the economy, monitoring programs to detect the organism have been implemented in affected areas. However, until recently, specific identification of the two toxic species known thus far, Pfiesteria piscicida and P. shumwayae (sp. nov.), required scanning electron microscopy (SEM). SEM is a labor-intensive process in which a small number of cells can be analyzed, posing limitations when the method is applied to environmental estuarine water samples. To overcome these problems, we developed a real-time PCR-based assay that permits rapid and specific identification of these organisms in culture and heterogeneous environmental water samples. Various factors likely to be encountered when assessing environmental samples were addressed, and assay specificity was validated through screening of a comprehensive panel of cultures, including the two recognized Pfiesteria species, morphologically similar species, and a wide range of other estuarine dinoflagellates. Assay sensitivity and sample stability were established for both unpreserved and fixative (acidic Lugol’s solution)-preserved samples. The effects of background DNA on organism detection and enumeration were also explored, and based on these results, we conclude that the assay may be utilized to derive quantitative data. This real-time PCR-based method will be useful for many other applications, including adaptation for field-based technology

Bacterial production in an arctic pond

Bacteria of natural waters have an important role in recycling nutrients. As we accumulate information on the biomass of bacteria, however, we realize that these large quantities of bacteria may also be an important source of particulate matter for animals. While these statements have been made before, there have been few attempts to quantify the role of bacteria as producers of particulate matter in freshwater systems. The study reported here deals with biomass and production rates of bacteria in a tundra pond in arctic Alaska

Lake characteristics influence recovery of microplankton in arctic LTER lakes following experimental fertilization

Lakes N-1 and N-2 at the Arctic Long Term Ecological Research site at Toolik Lake, Alaska, U.S.A. were fertilized with nitrogen and phosphorus for 5 and 6 years, respectively. The response and recovery of the microplankton community (protozoans, rotifers and crustacean nauplii) differed in the two lakes. Microplankton biomass in Lake N-1 increased five-fold while that in Lake-N-2 only doubled, despite larger nutrient additions to N-2. Microplankton community structure in Lake N-1 shifted toward dominance by few taxa, while the community in Lake N-2 maintained diversity. Finally, the recovery of Lake N-1 to near prefertilization microplankton biomass levels was rapid, while Lake N-2 showed at least a 1-year lag in recovery. These differences appear to be related to differences in the structure of lake sediments

Changes in abundance, composition and controls within the plankton of a fertilised arctic lake

1. An oligotrophic arctic lake was fertilised with inorganic nitrogen and phosphorus as (NH4)2 NO3 and H3PO4 for five summers. The loading rate was 1.7–2.5 mmol N m–2 day–1 and 0.136–0.20 mmol P m–2 day–1 which is two to three times the annual loading of lakes in the area. The heterotrophic microzooplankton community was enumerated during the experiment as well as 1 year pre- and post-treatment. 2. The structure of the microplankton community changed from a nutrient limited system, dominated by oligotrich protozoans and small-particle feeding rotifers, to a system dominated by a succession of peritrich protozoans and predatory rotifers. These peritrich protozoans and predatory rotifers were not present prior to fertilisation and never constituted more than a small fraction of the biomass in other lakes at the research site. The average biomass of the rotifers and protozoans was more than seven and a half times larger by the end of fertilisation than it was initially. 3. Because of the increases in numbers of individuals in these new taxa, the structure of the microbial food web changed. When fertilisation stopped, most parameters returned to prefertilisation levels within 1 year

Detection of the Dinozoans Pfiesteria piscicida and P. shumwayae: A Review of Detection Methods and Geographic Distribution

Molecular methods, including conventional PCR, real-time PCR, denaturing gradient gel electrophoresis, fluorescent fragment detection PCR, and fluorescent in situ hybridization, have all been developed for use in identifying and studying the distribution of the toxic dinoflagellates Pfiesteria piscicida and P. shumwayae. Application of the methods has demonstrated a worldwide distribution of both species and provided insight into their environmental tolerance range and temporal changes in distribution. Genetic variability among geographic locations generally appears low in rDNA genes, and detection of the organisms in ballast water is consistent with rapid dispersal or high gene flow among populations, but additional sequence data are needed to verify this hypothesis. The rapid development and application of these tools serves as a model for study of other microbial taxa and provides a basis for future development of tools that can simultaneously detect multiple targets