Posters from the Spring Meeting, University of Birmingham 17-19 April 2000

Benthic Foraminifera from the Eden Estuary, N. E. Scotland.

Heather A. Austin University of St Andrews, Gatty Marine Laboratory, St Andrews.

Foraminifera are widely employed as paleoenvironmental indicator species. However, very little is known of the ecology of free-living benthic foraminifera inhabiting intertidal sediments. This poster provides an introduction to the benthic foraminifera of the Eden Estuary, N. E. Scotland. The Eden Estuary is a small (10 km²) macrotidal (approximately 5 meters) estuarine environment with large and expansive intertidal mudflats (7.9 km²). Preliminary surface sediment samples to a depth of 1 cm reveal a rich and relatively diverse benthic foraminiferal assemblage. The dominant "live" (rose Bengal stained) taxa are Haynesina germanica and Elphidium incertum. While the "dead" assemblage is dominated by Stainforthia fusiformis. Selected taxa are illustrated by scanning electron micrographs (SEM) and light micrographs. Standing crops on the mid-shore mudflats during October 1999 are estimated to be 5 cm^-2.

These results are part of a larger study which aims to (1) determine the natural distribution of "live" benthic foraminifera within the estuary; (2) establish the seasonal succession of foraminiferal standing crop across an estuarine transect; (3) relate these seasonal changes to a variety of biotic and abiotic environmental variables; (4) extract living foraminifera into laboratory culture to evaluate foraminiferal response to individual variables. The goal of this study is to increase our understanding of the ecology and physiology of epipelic foraminifera.

The potential harbouring of pathogenic bacteria by protozoa in biofilms.

Joanna English¹, Jackie Parry¹, and Roger Pickup². 1 Biological Sciences Department, IENS, Lancaster University, Lancaster, LA1 4YQ. 2 Institute of Freshwater Ecology, Windermere Laboratory, Far Sawrey. Ambleside, Cumbria, LA22 OLP.

Protozoa have been nicknamed "Trojan Horses of the Microbial World". Certain species of pathogenic bacteria, for example Legionella sp. and Vibrio cholera, have been proven to survive and replicate within protozoan hosts. Others have been identified as surviving in protozoan hosts but not replicating, for example coliform bacteria such as Pseudomonas spp. and Salmonella typhimurium. In the natural river environment coliform bacteria, of human and animal origin, that can be potential pathogens can integrate into biofilms (surface-associated communities). Considering that there are a number of bacterivous protozoa also existing in biofilms, this project aims to examine protozoan-coliform interactions within them. The River Conder, Lancashire has been chosen as the experimental site as it shows a continuum of faecal coliform levels, from pristine sites to those which are heavily contaminated. Naturally occurring coliforms have been isolated and identified, and their fate within protozoan species is currently being evaluated i.e. whether they are digested or survive within the protozoan, with or without replication.

Digital analysis of protozoan colonisation of biofilms.

Karen Heaton¹, Jackie Parry¹ and Gianfranco Novarino². 1 Division of Biological Sciences, IENS, Lancaster University, Lancaster, LA1 4YQ.
2 Department of Zoology, Natural History Museum, Cromwell Road, London, SW7 5BD.

To date, very little is known about the initial stages of biofilm formation. Though bacterial colonisation of surfaces has been investigated, it has never been observed in the presence of protozoa. A flow cell has been designed that allows the observation of bacterial colonisation of a virgin substratum in the presence of protozoa (test system) and in the absence of protozoa (control system), simultaneously. The colonisation is monitored using a standard or inverted microscope and filmed using a CCD (charge coupled device) video camera. This type of camera can record images 25 times a second thus allowing an overall picture of protozoan movement to be created and the data run together into a computer digitiser. Using this system, we intend to address how bacteria and protozoa interact during the establishment of biofilms.

An automated method for the determination of protozoan grazing rates.

Karen Heaton and Jackie Parry, Division of Biological Sciences, IENS, Lancaster University, Lancaster, LA1 4YQ.

This novel technique uses fluorimetry to measure the decrease in E. coli cells transformed to express the green fluorescent protein (GFP), over time in the presence of a protozoan predator. It relies on the fact that the GFP is denatured at low pH and that during digestion, the pH of protozoan food vacuoles drops and its fluorescence is lost. The grazing rates of protozoan monocultures, or natural assemblages can be estimated by the decrease in fluorescence over time. The experiments are undertaken in a fully automated, multi-label, multi-task plate reader (Victor 1420) using 96 cell well microtitre plates thus allowing a calibration curve of live E. coli cells versus fluorescence, several controls and three cultures with replicates to be run at the same time. The data are produced in an Excel file for which a macro has been written to automatically manipulate the data. The sensitivity of the fluorimeter allows us to accurately determine the reduction in free E. coli cells in the media due to grazing, the inherent fluorescence of individuals of different protozoan strains and the period required for food vacuole acidification to occur in different strains of protozoa.

Effect of grazing on picocyanobacteria in Esthwaite Water.

Katie Harper¹, John Smith¹, Jackie Parry¹ and John Day². 1 Division of Biological Sciences, IENS, Lancaster University, Lancaster, LA1 4YQ.
2 Institute of Freshwater Ecology, Windermere Laboratory, Far Sawrey. Ambleside, Cumbria LA22 OLP.

Picocyanobacteria form a major component of the total chlorophyll concentration in oligotrophic and mesotrophic waters, but far less in those which are eutrophic (previous work at Lancaster University). Grazing of picocyanobacteria, mainly by heterotrophic nanoflagellates (HNANs) also increases with eutrophication. This suggests a change of control from bottom-up in oligotrophic waters to top-down in eutrophic waters. Little is known about the community structure of the picocyanobacteria as there are inherent difficulties in classification due to their small size and lack of distinguishing morphological characteristics. It is known that the pigment composition of the community changes with trophy (from domination by phycoerythrin rich in oligotrophic waters to phycocyanin rich in eutrophic waters). An in-depth study of the community structure of picocyanobacteria and preferential grazing by HNANs in Esthwaite Water (a eutrophic lake) in the English Lake District will be performed. Hip 1 PCR typing will enable differentiation between strains of picocyanobacterial isolates from Esthwaite Water. Experiments will include: a) incubation of mixed (Hip 1 typed) cultures of picocyanobacteria from Esthwaite Water in the presence of different raptorial-feeding flagellates e.g. Paraphysomonas sp. and Bodo sp. b) incubation of monocultures of (Hip 1 typed) picocyanobacteria with different size classes of grazers from Esthwaite Water.