Bacterial recolonization of deposit-feeder egesta: In situ regrowth or immigration?

Plante, Craig J., Susan B. Wilde

Limnol. Oceanogr., 46(5), 2001, 1171-1181 | DOI: 10.4319/lo.2001.46.5.1171

ABSTRACT: The related processes of disturbance, recolonization, and succession can play major roles in structuring communities and in generating spatial heterogeneity. Nonequilibrium processes have been little studied with respect to microbial community dynamics. Here we report experimental efforts to identify the mechanisms of recolonization of egesta employing two intertidal deposit feeders, Balanoglossus aurantiacus and Nereis succinea. Using direct microscopic counts and Biolog plates, we compared the quantitative and qualitative patterns of recovery in egesta isolated from underlying sediments on ‘‘latrines’’ to recolonization in naturally incubated fecal casts. Significant recovery over the 2-h observation periods was never seen on latrines. Rapid recovery in metabolic potential was observed in the naturally incubated fecal casts of both animal species. Likewise, a rapid numerical recovery was seen in the egesta of N. succinea casts on sediments. In contrast, no numerical recovery was evident in any fecal casts of B. aurantiacus over 2 h, regardless of treatment. For these two species, recolonization appears to be dominated by migration of bacteria from underlying sediments as opposed to repopulation by survivors of ingestion. These findings indicate that renewal of available (digestible) microbial resources to deposit feeders is more rapid than would be predicted if regrowth was the dominant process of recolonization. Furthermore, because recovery time is short relative to the interval between disturbances, deposit feeding is unlikely to play a major role in structuring benthic microbial communities.

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