Record Details
Organization and the adaptation of aquatic laboratory ecosystems to resource availability, exploitation, and a toxicant
ScholarsArchive at Oregon State University
| Field | Value |
|---|---|
| Title | Organization and the adaptation of aquatic laboratory ecosystems to resource availability, exploitation, and a toxicant |
| Names |
Woltering, Daniel Mark
(creator) Warren, Charles E. (advisor) |
| Date Issued | 1980-10-03 (iso8601) |
| Note | Graduation date: 1981 |
| Abstract | Organization and the adaptation of aquatic laboratory ecosystems to resource availability, exploitation, and a toxicant were examined in a 34-month study. Sixteen 560-liter microcosms including prey, predator, and competitor populations were employed over a wide range of energy and habitat resource availability and exploitation of the top predator. Chronic exposure to the pesticide dieldrin was used to perturb systems near steady states. Empirical generalizations from ecological theory, productivity theory, and fishery exploitation theory were incorporated to explain in part such performances as development, structure, and persistence of the laboratory ecosystems, their communities, populations, and individual organisms. Dynamic (developmental) and near steady-state community structure and organization were detailed for guppy, amphipod, snail, planaria, and algae populations and for a benthic detritus and microorganism component. Near steady-state population performances including density, production, yield, and size-specific growth and reproduction were determined for the guppy population in order to demonstrate the concordance of life history, population, and community level performances with changes in environmental conditions. A system of isoclines on a series of interrelated resource-utilizer and competition phase planes was employed to gain a better understanding of the structure and apparent organization of the laboratory systems. The 16 systems were established with a 0.6 gram/day alfalfa ration, 20 percent of each tank bottom covered with gravel for invertebrate habitat, and 0, 10, 20, or 40 percent guppy exploitation per month. Exploitation directly affected the size of the guppy populations near steady state (through observed changes in production, yield, growth, and reproduction) and indirectly affected the size of snail and amphipod populations which responded to competition and/or predation from guppies. Following many months of near steady-state system behavior (i. e. restricted fluctuations of population biomasses), eight systems were shifted to a 4.0 grams/day alfalfa ration and 95 percent gravel cover. These high energy and habitat level systems were characterized by relatively complex trophic and habitat resource partitioning. These systems developed different population interactions and community structure and had much higher population densities. At the same time, four low energy and habitat level systems (one at each guppy exploitation rate) with well established near steady states began continuous exposure to 1.0 ppb dieldrin in the water. The response of the laboratory systems to the toxicant was determined by the levels of prevailing environmental conditions as well as by the system's organization and the capacity of the populations to adapt and to persist. There were both density-dependent (via exploitation) and time-dependent components to the response to toxicant perturbation. In general, dieldrin reduced the growth and reproduction of the guppies, this resulting in smaller population biomasses. Amphipod biomasses increased in response to reduced predation and competition. The ecosystem with 0 percent exploitation (i.e. the largest guppy biomass) responded immediately with apparent dieldrin induced mortalities of mature fish. However, eventually the population recovered its lost biomass. There was no apparent initial response at 40 percent exploitation (i. e. smallest guppy biomass), but after 15 months of exposure the guppy population went extinct apparently from the. combined stress of exploitation and toxicant. Community organization and its expression in community development, structure, and persistence involved the adaptation of species populations to each other, to available energy and materials, to habitat, to climatic conditions including water quality and temperature, to exploitation, and to the introduction of the toxicant. Manipulating energy and habitat availability, exploitation levels, and toxicant presence altered near steady-state community, population, and individual organism performances. In these responses to environmental conditions, there was a certain concordance of community, population, and life history patterns that constitutes adaptation of the community and its subsystems. |
| Genre | Thesis/Dissertation |
| Topic | Aquatic ecology |
| Identifier | http://hdl.handle.net/1957/17872 |
