Rotifera community
[ref. ID; 1818]
Test system
Urban influences
Test design
26 ponds investigated were subject to distinctly urban influences. All ponds were from north and central London, within 1 kilometre of an underground train station. Average pond size was 1311 m2 +/- 517 m2 (SE) and the ponds were chosen to have a comparable geology, primarily London clay, although 8 sites were on fluviatile and glacial gravels.
Rotifer samples were collected using a thrown phytoplankton net (mesh size 53 um x 53 um, diameter 25 cm). The net was cast out to the middle of the pond, then hauled to the bank, dragging it through any macrophyte beds. This process was repeated 5 times from different parts of each pond to gain a representative sample. Rotifers were preserved in 5% formalin solution. Sampling time was late Summer (August-October 1993) and Spring (April 1994).
Measurements/observations
Identification of rotifers, Heavy metal concentrations, Hydrocarbons, phosphate and nitrate concentrations.
Evaluations
The rotifer lists for each season were combined, then classified into similar assemblages using the package TWINSPAN (Hill 1979). The classification was limited to four divisions, producing 7 end groups, which were described in terms of macrophyte cover, enrichment, pH, conductivity and physical appearance. At each division, indicator species were given, characteristic of the dichotomy. Rotifer assemblages were then ordinated using the package DECoRANA (Hill 1979) to determine the major sources of variation which were responsible for shaping these assemblages. The major sources of variation (axes 1-4) were then correlated (Spearman Rank Correlation) with the physicochemical and biological parameters measured. Comparison of species richness was undertaken with the Mann-Whitney test, using MINITAB version 8.2.
[ref. ID; 1853]
Test system
The non-chlorinated, open cooling-system of a fossil-fuelled power station
Evaluations
Mortality.
[ref. ID; 3329]
Test system
120 days sublethal toxicity
Test strains
Asplanchna girodi (predator)- Brachionus calyciflorus, Keratella cochlearis, Philodina acuticornis, Lepadella patella, Trichocerca pusilla, Plationus patulus (prey)
Toxicants
Pentachlorophenol.
Evaluations
Population growth rate, maximum population densities (Dmax), percent of carrying capacity at Dmax.
[ref. ID; 6964]
Test system
Toxicants
Ultraviolet
Test design
Zooplankton were incubated in the surface waters of two lakes (Lake Lacawac and Lake Giles) with different DOC concentrations. UV present (+UV, no mesh), UV present along with window mesh (+UV, mesh), UV excluded (-UV, no mesh), and UV excluded with window mesh (-UV, mesh). The window mesh was used as a neutral density filter as it reduced the transmission of incident light by approximately 60%. The exposure system consisted of a polyvinyl chloride (PVC) frame with an acrylite sheet (approximately 0.5 x 1.5 m) that either allowed (OP-4 for the +UV treatments) or blocked (OP-2 for the -UV treatments) UV transmission. On each frame a 1" x 1" thin plastic mesh netting was tied to the PVC frame underneath the acrylite sheet. A length of PVC tubing separated the frames into two squares, so that two 4-L capacity zipper-closed BITRAN (12"x12" polyethylene) bags were suspended between the mesh and plastic sheet. The experimental bags for the mesh treatment were placed in 13"x13" cases made of window screen mesh. The frames were held up at the very surface of the water column by styrofoam. A 0.5 m long string with a hook was used to attach the rack to a rope line suspended between two anchored buoys. Eight frames (four each with OP-2 and OP-4) were incubated in each lake, so that each treatment had four replicates (two per frame). Exposure period 3 days or 7 days.
Measurements/observations
Count and identification.