Post-Grant Reports


Student-Faculty Collaborative Research Grant Report

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Marine Biology


Marine sponges are known to host large and diverse microbial communities, with densities as high as 10^8 cells/mL representing 15 bacterial phyla. These bacteria are suggested to play an important role in the metabolism of the host sponge. These sponges feed by filtering microorganisms out of vast amounts of water. As a result of this filtering, sponges very effectively integrate their environment. Given this pumping ability and the sensitivity of the bacterial communities to even minute environmental changes, sponges are excellent candidates as biological indicators of environmental degradation in their habitat. In order to determine the effects of varying nutrient levels on sponges and their associated microbial communities, we placed nutrient addition devices (NAD) at Netarts Bay in Netarts, Oregon for six weeks to increase the nutrient load. To assess sponge abundance and diversity we analyzed video transects, and we assessed bacterial abundance and diversity using scanning electron microscopy (SEM) and examining bacterial DNA extracted from sponge tissue samples using gradient gel electrophoresis (DGGE), respectively. In addition, we collected ambient and exhalent water samples in order to assess the nutrient flux through the sponge. We found a significant decrease in sponge abundance and a decrease in bacterial diversity after six weeks of treatment. In addition, we found significant changes in nitrate and total nitrogen fluxes between control and NAD treated sponges, suggesting that bacterially-mediated nitrogen cycling was significantly modified by the nutrient addition. Thus, increased nutrient loads appear to detrimentally affect sponges and their associated microbial communities. As sponge communities seem to show a predictable response to excess nitrogen, they remain excellent candidates for use as bioindicators.


This research was conducted as part of a Linfield College Student-Faculty Collaborative Research Grant in 2013, funded by the Office of Academic Affairs.

Student collaborators were Matt Creech, Amy Hammerquist, and Mariah Denhart.

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