Enhanced phosphorus accumulation efficiency by the pelagic community at reduced phosphorus supply: A lake experiment from bacteria to metazoan zooplankton

Abstract

The effects of experimentally reduced total phosphorus concentrations (TP) from 2.4 to 0.6 mol L Ϫ1 on plankton community in a shallow lake were evaluated from the proportion between dissolved reactive P (DRP), dissolved nonreactive P (DOP) and particulate organic P (POP), and the stoichiometry among particulate organic carbon (POC), nitrogen (PON), and POP. In both triple ratios, DRP : DOP : POP and POC : PON : POP, we used POP as a key component to indicate shifts between P fractions and between nutrients in particulate organic matter. The enhanced P accumulation by the planktonic assemblage by 14% at reduced P supply was achieved by two steps, in the first year mainly at the expense of DOP and in the second year by DRP. The evidence that this increase of %POP of TP reflects the adaptive P utilization of the organisms under low P supply was substantiated by significant relationships between P fractions and changes in the community. A higher %POP of TP was associated with higher specific alkaline phosphatase activity and with tighter coupling between producers and consumers respectivelythat is, driven from both the nutrient-producer and the producer-consumer interface. A lowered %DOP of TP was significantly related to smaller overall loss rates for the carbon pool of bacteria and algae, whereas %DRP of TP was correlated to the decrease of the biomass of most organism groups. Stoichiometric shifts toward a P-rich assemblage under low TP have been justified by compositional shifts from N-rich cyanobacteria to P-rich eukaryotic algae and bacteria. The shifts toward POP in both triple ratios strongly indicated that the plankton community acted as a sink for phosphorus under reduced total pool size.Ecosystems are regulated by abiotic and biotic factors. The controversial debate over which of the two is more important finally led to the concept of bottom-up and top-down control. These are not mutually exclusive but act alternatively or simultaneously. Abiotic factors such as nutrient supply establish potential biomass increases of producers, whereas food web structure determines actual biomass increase. The concept is complicated by feedback and coupling 1 Corresponding author (Katrin.Teubner@oeaw.ac.at). AcknowledgmentsWe thank Dan Danielopol, Gernot Falkner, Martin Hahn, Alois Herzig, Thomas Posch, and Bettina Sonntag for discussion on adaptation of organisms, ratios, and food chain structure. We are very grateful to Thomas Weisse, Richard Robarts, and two anonymous reviewers for improving an earlier draft of the manuscript.

Modifications in phytoplankton size structure by environmental constraints induced by regime shifts in an urban lake

“…Similar changes during ecosystem regime shift in the urban lake, Alte Donau have been described for a number of variables and derived parameters by Teubner et al (2003). Reduction of various nutrient components strongly affected phytoplankton production and growth as well as the producer-consumer interface in the food web.…”

Phosphorus dynamics in the water of tropical semiarid reservoirs in a prolonged drought period

“…Phosphorus is considered a limiting nutrient and is present in freshwater systems in forms: soluble reactive phosphorus (SRP), dissolved organic phosphorus (DOP), and particulate phosphorus (PP) (Teubner et al, 2003). The sum of soluble reactive phosphorus (SRP) and dissolved organic phosphorus (DOP) is the total dissolved phosphorus (TDP).…”

“…SRP is the primary dissolved form of phosphorus and is readily available to algae and aquatic plants (Golterman, 2004). PP can be seen as a key parameter in P limited ecosystems, because it is a function of total biomass, but, the PP is associated to other fraction of P in water (SRP and DOP) (Teubner et al, 2003). Thus, the determination of P forms in water is important to understand their dynamics and relationships with other components of the aquatic system, such as phytoplankton, macrophytes and sediment, and understand the implications in the water quality.…”

Zooplankton phosphorus excretion in Swarzędzkie Lake (Western Poland) and its influence on phytoplankton

“…Moreover, as the turnover rate of a unit of phosphorus increases, less of the fraction of input phosphorus is deposited in sediments and more is passed up the trophic food web (Ejsmont-Karabin 1984). The process of nutrient recycling is especially important in oligotrophic lakes, primarily due to organisms in the microbial loop (Teubner et al 2003). Greater internal loading in eutrophic lakes stimulates the development of larger phytoplanktonic organisms, with relatively high nutrient-storage capacities (Reynolds 1993, Reynolds et al 2002.…”

“…Greater internal loading in eutrophic lakes stimulates the development of larger phytoplanktonic organisms, with relatively high nutrient-storage capacities (Reynolds 1993, Reynolds et al 2002. Consequently, the importance of the microbial loop in phosphorus recycling in eutrophic lakes decreases and the role of micro-and mesozooplankton increases (Teubner et al 2003).…”