Parasites and ecosystem energy flow
Creators: name: Lettini, Stacey E.
Publisher: name: No Publisher Supplied
Year: 2009

description: It has been difficult to incorporate parasites into ecological studies at the community and ecosystem levels.  The small size of parasites makes them easily overlooked, and the effects of parasites can often be subtle, indirect and difficult to measure.  In this thesis I argue that the best way to include parasites into ecological studies is to measure the direct costs of parasites at the individual, population, and community levels.  Furthermore, I propose that the best measure of cost is direct energy loss because this metric will scale from the individual to the ecosystem level.  Thus, the objectives of this dissertation were to determine the direct and indirect energetic costs of parasitism within individuals, populations, and communities of hosts.  To determine the energetic effects of parasites, field surveys, bomb calorimetry, and respirometry were used to create energy budgets for all species collected from streams of the New Jersey Pinelands, including the parasites.  The most common parasite was Acanthocephalus tehlequahensis, and at the individual and population level, this parasite significantly alters the energy allocation patterns in its isopod intermediate host.  Infection increased ingestion and respiration, decreased survival and reproduction, and caused significantly more production energy to be allocated to growth.  This parasite extracted 6.7% of the production energy from the isopod population (infected and uninfected hosts).  On the other hand, in the definitive hosts, the parasite had little effect on energy allocation, and there were no significant differences in the energy budgets between infected and uninfected pirate perch hosts infected with A. tehlequahensis and the trematode Phyllodsitomum sp. Although, parasite infection double to the proportion of production energy allocated to reproduction from 7% to 14%, and parasites within the fish population (infected and uninfected hosts) received 1.3% of the host’s production energy.  At the ecosystem level, energy budgets were created within two pineland streams, one with a high-level of parasitism and one with a low level of parasitism.  Parasites extracted a small amount of energy from both streams (&lt;1%), but proportionally less energy went to parasitism in the stream with low levels of parasitism.  Parasite establishment within this stream may be constrained by energy flow through the food web because little energy makes it up the food web to trophic levels that parasites infect.  A stable isotope analysis (δ13C andδ15N) was used to determine energy flow and trophic relationships of adult and juvenile parasites and their hosts.  There were significant differences in δ15N values of juvenile and adult parasites, and different parasite species within the same hosts.  These data suggest that juvenile parasites can feed at a higher trophic level than their adult counter-parts, and when co-occurring within the same fish host different parasite species may acquire energy from different trophic positions.  The results of this dissertation suggest that parasites require a small amount of energy from their hosts at all levels of ecological organization.  However, parasites are intimately tied to the energy flow of a system because they alter energy allocation patterns of their hosts, they derive their energy from many trophic levels within a food web, and energy dynamics may regulate parasite establishment and maintenance at the ecosystem level.  Therefore, energy can be a useful metric in determining the ecological costs of parasitism.