Primary production and phytoplankton composition in relation to DOC input and bacterioplankton production in humic Lake Örträsket

Abstract

1. The biomass and production of picophytoplankton, large phytoplankton and heterotrophic bacterioplankton were measured in humic Lake Örträsket, northern Sweden during four consecutive summers. 2. High flow episodes, carrying fresh dissolved organic carbon (DOC) into the lake, always stimulated heterotrophic bacterial production at the expense of primary production. Primary production never exceeded bacterial production for approximately 20 days after such an episode had replenished epilimnial DOC. We suggest that allochthonous DOC is an energy source that stimulates bacterioplankton that, because of their efficient uptake of inorganic nutrients, are then able to outcompete phytoplankton. After the exhaustion of readily available DOC, phytoplankton were able to dominate epilimnion production in Lake Örträsket. 3. Biomass production was higher when dominated by phytoplankton than by bacterioplankton, despite a similar utilization of nutrients in the epilimnion throughout the summer. We propose that different C : N : P ratios of bacterioplankton and phytoplankton permit the latter to produce more carbon (C) biomass per unit of available inorganic nutrients than bacterioplankton.

Efficient aquatic bacterial metabolism of dissolved low-molecular-weight compounds from terrestrial sources

“…Snow melt causes a high flow episode in April to May every year in most boreal areas, carrying X50% of the total annual runoff and DOM transport. Moreover, the spring flood can cause pronounced stimulation of bacterial production in boreal lakes (Bergström and Jansson, 2000) with spinoff effects on the pelagic food webs (Drakare et al, 2002). The streams and the lake outlet were sampled once in early spring (March 14) at the beginning of the rising limb and once in late spring (May 22) at the end of the falling limb of the spring flood hydrograph of 2007.…”

Seasonal variations of dominant phytoplankton in humic forest lakes

“…DHS have especially strong negative influences on phytoplankton as they chemically bind phosphates and other essential elements (including calcium and iron) into colloidal complexes, Brought to you by | MIT Libraries Authenticated Download Date | 5/10/18 1:52 PM limiting their bioavailability. Along an increasing gradient of DHSC in a pool of DOC autotrophic algae disappear, and their place is taken by taxa with the features of facultative heterotrophs and by flagellated phytoplankton, which are able to move in the water column (Keskitalo et al 1998, Drakare et al 2002.…”

“…However, only a few have been base on research that lasted more than a year (Keskitalo et al 1998, Hehmann et al 2001, Drakare et al 2002. This paper presents the results of a four-year study (1999)(2000)(2001)(2002) on the qualitative and quantitative variations of phytoplankton communities in humic lakes, with particular emphasis on seasonal variability and cycles of dominance.…”

Phytoplankton composition and functional groups in a tropical humic coastal lagoon, Brazil

“…Mixotrophy has been thought to be a particularly successful strategy in humic systems (Drakare et al 2002;M. Järvinen, unpublished data), where low light and low dissolved inorganic nutrients are limiting to phytoplankton growth, and high concentration of dissolved organic matter leads to high bacterial density (Jones 2000).…”

“…Therefore, lakes with high concentration of humic compounds are identified as a distinct class of systems, easily recognized by their dark-colored water (Hessen & Tranvik 1998). In regard to phytoplankton composition, they frequently show high contribution of chrysophytes and cryptomonads, both with mixotrophic taxa (Jones 1998;Drakare et al 2002;M. Järvinen, unpublished data;Pålsson & Granéli 2004).…”