Efficiency of crustacean zooplankton in transferring allochthonous carbon in a boreal lake

Abstract

v€ ag 4-6, Ume a 90736 Sweden Citation: Grosbois, G., D. Vachon, P.A. del Giorgio, and M. Rautio. 2020. Efficiency of crustacean zooplankton in transferring allochthonous carbon in a boreal lake. Ecology 101(6):Abstract. Increased incorporation of terrestrial organic matter (t-OM) into consumer biomass (allochthony) is believed to reduce growth capacity. In this study, we examined the relationship between crustacean zooplankton allochthony and production in a boreal lake that displays strong seasonal variability in t-OM inputs. Contrary to our hypotheses, we found no effect of allochthony on production at the community and the species levels. The high-frequency seasonal sampling (time-for-space) allowed for estimating the efficiency of zooplankton in converting this external carbon source to growth. From the daily t-OM inputs in the lake (57-3,027 kg C/d), the zooplankton community transferred 0.2% into biomass (0.01-2.36 kg C/d); this level was of the same magnitude as the carbon transfer efficiency for algal-derived carbon (0.4%). In the context of the boundless carbon cycle, which integrates inland waters as a biologically active component of the terrestrial landscape, the use of the time-for-space approach for the quantifying of t-OM trophic transfer efficiency by zooplankton is a critical step toward a better understanding of the effects of increasing external carbon fluxes on pelagic food webs.

Freshwater Microbial Eukaryotic Core Communities, Open-Water and Under-Ice Specialists in Southern Victoria Island Lakes (Ekaluktutiak, NU, Canada)

“…Annual production largely depends on inorganic nutrient supply in the summer, but in ice-covered lakes, organic matter produced in the summer is required to sustain biological activity during winter (Lizotte, 2009;Hampton et al, 2017;Teufel et al, 2017;de Melo et al, 2019). Dissolved organic matter (DOM) is processed by the winter bacteria that support heterotrophic flagellates, dinoflagellates, and ciliates (Lizotte, 2009;Vigneron et al, 2019), which are food for small zooplankton and which maintain resident fish populations (Grosbois et al, 2020), ensuring a healthy ecosystem.…”

Mercury Export From Freshwater to Estuary: Carbocentric Science Elucidates the Fate of a Toxic Compound in Aquatic Boreal Environments

“…Although boreal lakes and reservoirs differ in many respects, including age, residence time, mean water temperature, and the origin and quality of the OM available (Kalff, 2002;Tadonléké et al, 2012), carbocentric science teaches us that planktonic food webs in northern temperate and boreal lakes as well as in reservoirs are subsidized by allochthonous OM in a large proportion (Del Giorgio et al, 1999;Cole et al, 2002;Cole et al, 2006;Tadonléké et al, 2012;Emery et al, 2015;Grosbois et al, 2020). In fact, terrestrial soils typically provide very active loci for the decomposition of OM, which is exported to and through aquatic systems (Cole et al, 2007).…”

“…Autochthonous labile (easily degradable) OM (phytoplanktonderived organic compounds), although present in smaller quantities, has been shown to enhance overall bacterial activity and thus promote the incorporation of flooded allochthonous OM, which is less labile, at the bacterial level (Guillemette et al, 2015) or at a higher level in the trophic chain. In fact, Grosbois et al (2020) recently demonstrated that the efficiency of zooplankton in a boreal lake in transferring autochthonous and allochthonous carbon is equivalent, suggesting that the breakdown of terrestrial detritus and recalcitrant dissolved high-molecular-weight humic substances may be facilitated by co-metabolism using carbon of algal origin (labile autochthonous carbon). The Hg-centric science led to the same findings: the bioavailability of labile carbon in newly flooded areas or in productive lakes promotes bacterial activity (and, in some cases, in deep or warm temperate/tropical waters, anoxia), which, in turn, results in increased mercury methylation rates in the water column and in sediments, and an increase in its final byproduct, MeHg (Mailman et al, 2006;Bo et al, 2016;Bravo et al, 2017;Figures 1A-C).…”

Integrating ecosystem metabolism and consumer allochthony reveals nonlinear drivers in lake organic matter processing

“…Long-term metabolism patterns are more indicative of site-specific patterns than are day-to-day variations (Bernhardt et al 2018), but the study length varied among lakes and often focused on summer measurements. Annual trends in metabolism would be interesting to explore, particularly in conjunction with allochthony (Grosbois et al 2020).…”