Masters Theses

Date of Award

8-2003

Degree Type

Thesis

Degree Name

Master of Science

Major

Wildlife and Fisheries Science

Major Professor

J. Larry Wilson

Committee Members

Richard Strange, Sammy King

Abstract

National Park Service biological staff are charged with preserving and protecting all creatures within a park’s boundaries. It is only a matter of time before exotic zebra mussels (Dreissena polymorpha) invade all eastern waterways including Green River within Mammoth Cave National Park, Kentucky. The National Park Service, in cooperation with University of Tennessee, initiated this inventory of plankton within Mammoth Cave National Park to establish baseline data prior to zebra mussel invasion. During this two year study (2000-2002), 180 plankton samples were collected at three sampling sites which encompassed all major riverine habitat types within the three flow zones (free-flow, transitional, impounded) created by Lock and Dam #6. Duplicate plankton samples were taken on all six occasions at these sites. Each year one sample was collected in June/July (base flow), another in August/September (base flow), and the other in November/December (enhanced flow). Zooplankton were sampled using both vertical (4/site) and horizontal (4/site) tows with 153-micron and 80-micron mesh plankton nets. Samples were fixed in the field with a 10% sugared formalin solution for later examination in the laboratory. A 1.0-L polycarbonate water bottle was used to collect phytoplankton samples at a depth just above the Secchi disk transparency level; samples were fixed in a 1% Lugol’s solution and stored in an opaque container for analysis. Water temperature, conductivity, dissolved oxygen, pH, and water transparency were also measured and recorded at each sample site. Water quality data were similar among sites and the variation among dates was consistent with climatic conditions. Dissolved oxygen ranged from 10.96 (mg/L) in iv December 2001 to 6.20 (mg/L) in July 2002. Temperature ranged from 25.9o C in July 2002 to 6.4o C in November 2000. The pH ranged from 8.05 (su) in November 2000 to 5.72 (su) in July 2002. Conductivity ranged from 282 (mS/cm) in November 2000 to 383 (mS/cm) in July 2002. A paucity of zooplankton was observed in Green River while phytoplankton densities were similar to levels measured upstream in Green River Lake. The dominant zooplankton groups were Cladocera (Bosmina longirostrus) and Copepoda (Mesocyclops edax). Densities of Bosmina ranged from 0.01/L in September 2000 to 0.46/L in December 2001; M. edax densities ranged from 0.01/L to 0.53/L during the same period. Aquatic insects were collected at densities equal to or greater than the zooplankton during the study, with the family Chironomidae as the dominant aquatic insect taxon collected. Chlorophyta (green algae) was the dominant phytoplankton phylum present during all samples with approximately 97% of the species composition; the genus Cholorella comprised over 95% of all cells in every sample. Other filamentous Chlorophyta genera, like Ulothrix, contributed minor portions of the population. Also, Cyanophyta (blue-greens) and Chrysophyta (golden-brown algae) were found in relatively low numbers. Only limited evidence of zooplankton reproduction was found at the downstream sample site. We concluded that, during the study period, Green River did not exhibit a true plankton community, potamoplankton, but rather a tachyplankton (transient) community. A digital reference collection of zooplankton and phytoplankton was created to provide baseline data for future studies. A long-term plankton data set should be developed if future mussel propagation projects are to be successful in the river.

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