Positive feedback between chironomids and algae creates net mutualism between benthic primary consumers and producers

TitlePositive feedback between chironomids and algae creates net mutualism between benthic primary consumers and producers
Publication TypeJournal Article
Year of Publication2017
AuthorsHerren, C. M., Webert K. C., Drake M. D., Vander Zanden M. J., Einarsson A., Ives A. R., and Gratton C.
JournalEcology
Volume98
Issue2
Number of Pages447-455
Date PublishedFeb
Type of ArticleArticle
Reprint Number0012-9658
LTER Accession NumberWOS:000393375700016
Keywordsbenthic primary production; consumer-resource dynamics; facilitation;, lake myvatn; population-dynamics; spatial-distribution; larvae diptera;, nutrient cycling; positive feedback, river laxa; food webs; sediments; iceland; water; ecosystems
Abstract

The chironomids of Lake Myvatn show extreme population fluctuations that affect most aspects of the lake ecosystem. During periods of high chironomid densities, chironomid larvae comprise over 90% of aquatic secondary production. Here, we show that chironomid larvae substantially stimulate benthic gross primary production (GPP) and net primary production (NPP), despite consuming benthic algae. Benthic GPP in experimental mesocosms with 140,000 larvae/m(2) was 71% higher than in mesocosms with no larvae. Similarly, chlorophyll a concentrations in mesocosms increased significantly over the range of larval densities. Furthermore, larvae showed increased growth rates at higher densities, possibly due to greater benthic algal availability in these treatments. We investigated the hypothesis that larvae promote benthic algal growth by alleviating nutrient limitation, and found that (1) larvae have the potential to cycle the entire yearly external loadings of nitrogen and phosphorus during the growing season, and (2) chlorophyll a concentrations were significantly greater in close proximity to larvae (on larval tubes). The positive feedback between chironomid larvae and benthic algae generated a net mutualism between the primary consumer and primary producer trophic levels in the benthic ecosystem. Thus, our results give an example in which unexpected positive feedbacks can lead to both high primary and high secondary production.

URL<Go to ISI>://WOS:000393375700016
Print Copy LocationEcology