Angelo Coast Range Reserve

11 Jun, 05 AM - 30 Jun, 10 AM

The growth rate hypothesis of Sterner and Elser (2002) suggests a mechanistic linkage between P biogeochemistry and growth and reproduction of individual organisms. This linkage is driven by the relationship between variation in body P content and allocation of resources to ribosomes. To grow fast, an organism requires high RNA content, which leads to high P demand by that organism, possibly leading to constraints on the range of environments in which the organisms can survive and reproduce. New evidence is also accumulating that suggests this relationship is more complex and depends on whether or not P is limiting growth. When N is limiting, the P-growth rate relationship breaks down (Elser et al. 2003, Acharya et al. in press), presumably because N is required for the production of amino acids necessary for enzyme synthesis. Clearly, the dynamics of population growth and community assembly may be strongly influenced by N and P levels in the environment, as well as evolved life history characteristics of individual species. New evidence has also accumulated suggesting an interaction between temperature and body N and P content. As temperature increases, the amount of N or P required to maintain a certain growth rate declines, due to increases in enzyme activity at higher temperatures reducing the need to produce more enzymes. So clearly the temperature at which organisms are growing will influence their response to the productivity and nutrient template within which they are developing. Populations and communities are also developing in response to disturbance regimes, which can have important influences on evolutionary and ecological processes, particularly in stream ecosystems. In essence disturbance regimes define the length and predictability of favorable living conditions for organisms, which can interact with specific requirements of individual species, as well as patterns in nutrient flow and temperature to determine population and community dynamics. For example, high disturbance frequency would favor species that grow fast. These species are likely to have high body P contents, and therefore to have a high P demand from the environment. If P levels are low, and/or temperatures are low, these species cannot grow fast enough to persist. Another interesting possibility is that high disturbance frequency will select for species with high nutrient contents, which provide higher quality food for predators, increasing predator biomass. What I am interested in studying is how these three axes (nutrient availability, temperature, and disturbance regime) interact to determine instream community composition and patterns of energy flow and nutrient cycling across gradients of drainage area and productivity. Clearly, analyzing patterns in body stoichiometry of individual species and of producer and consumer communities will be a major component of this work, and will add to our knowledge of variation in body tissue chemistry of aquatic and terrestrial organisms. I see the first step to be a description of community composition and measurement of body CNP of key species from those communities across as wide a range in drainage area, food quality, quantity, temperature, and disturbance regime as possible, followed by experiments on individual species to determine their response to changes in key environmental parameters (ie N and P content of food, temperature, solar radiation).

Visit #13302 @Angelo Coast Range Reserve

Approved

Under Project # 8715 | Research

Ecological stoichiometry and biogeochemistry of stream food webs

undergraduate_student - St. Olaf College Minnesota

Reservation Members(s)

Nichole Turner Jun 11 - 30, 2007 (20 days)
Group of 3 Undergraduate Student Jun 11 - 30, 2007 (20 days)

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