Project Title: The role of sediment size distribution and other microhabitat factors in the abundance and relative dominance of various T. tubifex lineages
Project Start: 28 May 2004
Dana Winkleman, Unit Leader
Objective: The objective of our study is to estimate the relationship between microhabitat variables and the abundance and relative dominance of various T. tubifex lineages.
Introduction: Preliminary oligochaete sampling and PCR analyses conducted by the Colorado Division of Wildlife (CDOW) in the Williams Fork River and Spring Creek indicated that different lineages of T. tubifex dominate the two streams and also vary among sites within streams. For example, Spring Creek T. tubifex populations are virtually all lineage III, whereas on the Williams Fork, lineage V predominates on one reach and lineages III, V, and VI are found on other reaches in various proportions. Preliminary observations on the Williams Fork River indicate that lineage V may be associated with somewhat coarser substrates, but no quantitative sediment samples were collected to quantify possible habitat associations for the various lineages. We began sampling these areas for T. tubifex and collecting habitat information to evaluate the role of habitat variables, including substrate characteristics, in structuring the relative abundance of T. tubifex.
Summary of Progress:
Sampling Design and Mesohabitat Measurements
We are using two approaches to select sampling locations within each stream. The first approach used a stratified random sampling design to select sampling sites, stratifying the river based on stream mesohabitat classifications. We estimated the proportion of mesohabitat types in the William’s Fork River by visually classifying mesohabitats into Runs, Riffles, and Pools and estimating their relative abundance by measuring the linear extent of each habitat type. Based on the proportion of available mesohabitat, we randomly assigned sampling transects within each mesohabitat. Transects were perpendicular to the stream flow and were established by stretching a tape measure across the stream. At each transect a paired core and kick-net sample (see below) was taken at every meter. The second sampling strategy was referred to as targeted sampling. These sampling locations were selected based on flow and depth. We classified habitats based on three flows (high, medium, and low) and three depths (shallow, medium, and deep) resulting in nine possible habitats types, which correspond to several different mesohabitat types. For both sampling strategies, we recorded habitat variables such as water depth, water temperature, flow, and elevation. Substrate samples were also taken at each sample location to allow detailed analyses of substrate size and composition. To date, we have collected 6 transect samples and 30 targeted samples. Each sample consists of a core and kick-net sample (see below). We are currently processing samples (see below), and we plan to refine the sampling frame based on the results obtained from these samples. Habitats containing low densities of T. tubifex will be given lower weight in future sampling and those habitats that contain no T. tubifex will not be sampled.
T. Tubifex Sampling
T. tubifex samples using a stratified random sampling design, stratifying
classifications (see above).
Samples consisted of a 7.3cm diameter, 10 cm deep
core collected at the
center of the 0.5-m2 area that was subsequently
sampled with a kicknet. We are currently identifying and preserving
ethanol. Once all invertebrates are removed we
analyze core samples using standard ASTM analysis
size distribution (both dry
sieving and hydrometer analysis), bulk density
and percent organic
material. For lineage identification, we will send
50 haired oligochaetes from
each sample to be analyzed using qPCR. If possible,
all worms for the replicate 50 worm subsamples will
samples. If not
enough worms are present in the cores, the difference
will be made up with worms from the kick-net samples.
sent 20 samples
in for qPCR analyses.