An algal carbon budget for pelagic‐benthic coupling in Lake Michigan

Abstract

A budget for algal carbon was constructed to quantify the magnitude and major pathways of pelagicbenthic coupling at a site in southeastern Lake Michigan. The flux of algal C to the benthos and the rate of carbon burial were estimated from sediment traps and dated sediment cores, respectively. Assimilation and respiration rates of Diporeia sp., an abundant benthic amphipod, and of sediment microheterotrophs were measured in a microcosm study with 14C-labeled algae (Melosira italica). Melosira (italica and islandica) accounted for 53% of the algal C flux to the sediments. Radionuclide concentrations indicated no net sediment burial of organic C. Of the total C assimilated by Diporeia, 60% was respired, 35% was incorporated into biomass, and 5% was accounted for as soluble dissolved organic compounds. The areal rate of Diporeia respiration (29 nmol C cm 2 d-l) was 23 times greater than that for sediment bacteria (1.3 nmol C cm--2 d-I). Release of radioisotope in the form of dissolved organic compounds was much lower than that incorporated and respired for both Diporeia and sediment bacteria. Of the 61 mmol C m-2 of algal C estimated to be deposited during the spring bloom, Diporeia assimilation accounted for 6 l%, significantly more than the 2% observed for microbially mediated algal decomposition. These observations support the hypothesis of a strong pelagic-benthic energy coupling between the spring diatom bloom and Diporeia in Lake Michigan.

Effects of the coexisting Baltic amphipods Monoporeia affinis and Pontoporeia femorata on the fate of a simulated spring diatom bloom

“…This result is in agreement with many laboratory studies with a variety of experimental setups (Andersen & Kristensen 1992, Hansen & Blackburn 1992, Fitzgerald & Gardner 1993, Webb & Montagna 1993, Andersen 1996, Gullberg et al 1997, Ólafsson et al 1999. It is likely that most of this material is utilised on longer time scales.…”

Carbon source/sink function of a subtropical, eutrophic lake determined from an overall mass balance and a gas exchange and carbon burial balance

“…Sedimentation rates were calculated using a 210 Pb constant rate of supply (CRS) model and 137 Cs as a time marker. Organic matter reaching the surface sediment is easily ingested, mineralized, or resuspended and deposited elsewhere with most likely no organic matter being buried (Fitzgerald and Gardner, 1993), so the average long-term rate of carbon accumulation were calculated (Page et al, 2004). Mass accumulation rates (MAR) were averaged for the samples and were calculated with the relationship (Muller et al, 2005):…”

Ecophysiology of the benthic amphipod Monoporeia affinis in an open-sea area of the northern Baltic Sea:seasonal variations in body composition, with bioenergetic considerations

“…SegerstrAle 1937, Andersin et al 1984, Leonardsson et al 1988. The abundance and biomass of M. affinis populations show long-term oscillations (Andersin et al 1978(Andersin et al , 1984; substantial evidence of a coupling between the intensity of algal blooms and the abundance and biomass of benthic amphipod populations has been obtained from lakes (Johnson & Wiederholm 1992, Fitzgerald & Gardner 1993 and from shallow, coastal areas of the Baltic Sea (Cederwall 1977, Elmgren 1978, Sarvala 1986.…”