Evaluating the influence of macrophytes on algal and bacterial production in multiple habitats of a freshwater wetland

Abstract

Algal14 C uptake and bacterial 3 H leucine incorporation were measured over 20 months to assess the influence of macrophytes on the spatial distribution and magnitude of microbial production and the relative importance of algae versus macrophytes to whole-system energy flow in a southeastern U.S. wetland. Algal and bacterial production were determined for water column and plant-, sediment-, and wood-surface microhabitats in four zones defined by aquatic vascular plant composition: no macrophyte, floating leaved (Nymphaea odorata), heterophyllous (Proserpinaca palustris), or emergent macrophyte (Juncus effusus) zones. We combined production data with detailed habitat measurements to estimate production at meter-squared and whole-wetland scales and compared microbial C fixation to concurrently determined rates of macrophyte production. Production on plant surfaces was significantly lower than on wood and benthic sediments in all zones. At a meter-squared scale, 79% of algal production and 74% of bacterial production occurred on sediments, with epiphytes contributing Ͻ6% to both algal and bacterial rates. With the exception of phytoplankton in the Nymphaea zone and bacteria on Juncus zone sediments, production in the water column or on plant or sediment surfaces did not significantly differ among macrophyte zones. Thus, plant type did not affect the spatial distribution of microbial activity except in the Juncus marsh, where the limited area and volume of water per square meter reduced production at larger spatial scales. However, the magnitude of bacterial production was influenced by macrophytes, as bacterial carbon demand greatly exceeded the amount supplied by algal production. At the whole-ecosystem scale, macrophytes overwhelmed algal production, which accounted for only 4-10% of total wetland C fixation.Although significant progress has been made in understanding rates and determinants of algal and bacterial production and the contribution of these assemblages to energy flow in pelagic systems over the past two decades, microbial dynamics in other settings have received far less attention (Vadeboncoeur et al. 2002). This lack of information is particularly acute for wetlands (Goldsborough and Robinson 1996;Kirschner and Velimirov 1999), where studies of energy flow have focused on aquatic macrophytes rather than algae and where, conversely, bacterial populations are often viewed in terms of biogeochemical processes rather than productivity (but see Findlay et al. 1998). Consequently, 1 Corresponding author (ehstanley@wisc.edu). AcknowledgmentsWe are indebted to S. M. Evces for her tireless contributions to all aspects of this study. R. G. Wetzel generously provided supplies, equipment, and a wide range of other support and advice throughout this project, and G. M. Ward provided meteorological and hydrologic data. Thanks to L. S. W. Lindblom for access to her data. Pond surface area and volume estimates and wetland maps were made by Joe Partlow at the Department of Biological Sciences GIS Laboratory....

Comparison of Fungal Activities on Wood and Leaf Litter in Unaltered and Nutrient-Enriched Headwater Streams

“…Annual bacterial production on snags in a large blackwater river was estimated at ca. 0.7 g C m Ϫ2 year Ϫ1 (12), while bacterial production on wood in a subtropical wetland was 0.007 to 1.2 g C m Ϫ2 year Ϫ1 , depending on season and habitat, with a grand mean of 0.12 g C m Ϫ2 year Ϫ1 (43).…”

Importance of detrital algae, bacteria, and organic matter to littoral microcrustacean growth and reproduction

“…Eurycercus inhabited the Nymphaea zone almost exclusively (Lemke 2000). Surface waters were relatively nutrient poor (Stanley and Ward 1997), and monthly water temperatures ranged from 7.7uC to 28.1uC (Benke et al 1999). During the 14 C-incorporation experiment (15-17 March 1994), pH of wetland water was 5-6, and mean daily water temperature was 13.1uC.…”

Pomen makrofitov v jezerskem ekosistemu / The importance of macrophytes in lake ecosystem

“…Zaradi visoke primarne proizvodnje ma krofiti prispevajo velike količine organskih snovi v je zeru in po navadi celo presežejo primarno proizvodnjo alg (Wetzel 2001, Lauster et al 2006. V nekaterih jezerih lahko makrofiti vzdržujejo velik del bakterijske proizvodnje (Stanley et al 2003). Ker makrofiti v pli tvih jezerih vplivajo tako na fitoplankton in bakterije ) je pričakovano, da bodo vplivali tudi na interakcijo med fitoplanktonom in bakterijami.…”