Article
Midges, Cladophora and Epiphytes: Shifting Interactions Through Succession
Freshwater Science
(2012)
Abstract
Midge larvae (Pseudochironomus richardsoni Malloch) in the South Fork Eel River, California,
weave retreats in mats of Cladophora glomerata (L.) Kutz. and graze on its algal epiphytes. Densities of these
midges and their effects on Cladophora vary over time (seasonally, over the course of succession, and
interannually) and space (down the drainage network). New Cladophora growth is green, turns yellow with
early colonization by a monolayer of Cocconeis, and rusty-red as it becomes heavily epiphytized by a
multistory layer of Epithemia spp. (Rhopalodiaceae), diatoms that contain N-fixing endosymbiotic
cyanobacteria. To determine how midges influence epiphyte assemblage structure, we incubated
Cladophora in early (green [G]), mid (yellow [Y]), and late (rusty-red [R]) stages of succession with and
without midges and assessed changes in epiphyte density and composition. Midge effects on epiphyte
composition and density (as measured by % cover on Cladophora filaments) varied with stage of succession
and proximity to the ends of midge retreats. Local increases in retreat-associated cyanobacteria occurred in
Y and R stages. Percent cover of Cocconeis increased on Y filaments .2 cm from midge retreats (ambient)
indicating indirect midge effects (e.g., fertilization). Midges were less effective grazers on adnate Cocconeis
cells than on loosely attached Epithemia and often ingested Cladophora in the process of grazing or retreat
building, especially in G and Y stages. In contrast, midges that grazed on R Cladophora primarily consumed
diatoms in the Rhopalodiaceae. Midge survival and retreat quality were lower in G than in Y or R stages,
where retreats were longer and denser. Shifts in epiphyte composition and % cover caused by midge–algae
interactions at small scales (mm–m) could affect ecologically significant processes, such as N-fixation and
foodweb interactions at larger reach and watershed scales.
Keywords
- algal–grazer interactions,
- Cladophora,
- Cocconeis,
- cyanobacteria,
- diatoms,
- Epithemia,
- food webs,
- midge,
- Mediterranean climate,
- nitrogen fixation,
- Pseudochironomus
Disciplines
Publication Date
2012
DOI
10.1899/11-021.1
Publisher Statement
© 2012 by Society for Freshwater Science
Citation Information
Paula Furey, Rex L. Lowe, Mary E. Power and Alexis M. Campbell-Craven. "Midges, Cladophora and Epiphytes: Shifting Interactions Through Succession" Freshwater Science Vol. 31 Iss. 1 (2012) p. 93 - 107 Available at: http://works.bepress.com/paula-furey/6/