Algal nutrient limitation affects rotifer growth rate but not ingestion rate

Abstract

The food algae Scenedesmus acutus and Cyclotella meneghiniana were grown in chemostats in a modified WC medium at identical growth rates (0.4 d-l) but under different nutrient regimes. Nitrate or phosphate was reduced to produce N-or P-limited algae. Brachionus rubens did not differentiate between nonnutrientlimited and nutrient-limited Scenedesmus and ingested both at comparable rates. The rotifers reached highest maximum growth rates with nonnutricnt-limited Scenedesmus. N-limited Scenedesmus permitted similar growth rates at low food concentrations (below the incipient limiting level, ILL), but maximum growth rates at high food concentrations (above the ILL) were significantly reduced. With regard to the high N content of Brachionus, direct mineral N deficiency of the food appears to be possible. P-limited algae (Scenedesmus and Cyclotella) permitted no positive growth rates of the rotifers at all. P-limited algae that were short-term enriched with phosphate contained similar amounts of P as nonnutrient-limited algae but still were of lower nutritional quality, thus suggesting the importance of essential biochemical constituents.

How Daphnia copes with excess carbon in its food

“…These observations agree with results from shortterm experiments with the rotifer Brachionus rubens (Rothhaupt 1995) and D. magna (DeMott et al 1998). Yet some studies have shown apparently reduced algal clearance rates in long-term (20 h-2 day) incubations of daphniids feeding on P-limited chlorophytes (Van Donk and Hessen 1993;.…”

Investigation of a rotifer (Brachionus calyciflorus) - green alga (Scenedesmus pectinatus) interaction under non- and nutrient-limited conditions

“…These results are in concordance with the hypothesis that nutrient-limited algal food reduces growth of Brachionus and are comparable to those found by Rothhaupt (1995) and Jensen & Verschoor (2004) who offered S. obliquus that differed in nutritional status to Brachionus rubens and B. calyciflorus, respectively.…”

“…Rothhaupt (1995) showed that Brachionus rubens ingested nutrient (N-and P) limited Scenedesmus equally to non-limited cells, but that Brachionus growth was reduced. Also growth of B. calyciflorus was reduced when they were fed with nutrient-limited Scenedesmus (Jensen & Verschoor 2004).…”

Microzooplankton feeding behaviour: grazing on the microbial and the classical food web of African soda lakes

“…Brachionus is often considered to be a sizeselective grazer, unable to distinguish between particles of different quality (Demott, 1986;Rothhaupt, 1990Rothhaupt, , 1995Hansen et al, 1997). In contrast, Snell (1998) pointed out the presence of chemoreceptors in the buccal field of this genus, indicating that other factors might also play a role for food selectivity.…”

“…Furthermore, other methods such as isotopic or radioactive labelling and coulter counter techniques bear the risk of delays because of incubation times, altering microbial community structure or leading to a misinterpretation of egested particle fragments and cell breakage occurring during ingestion (Harbison & Mcalister, 1980;Peters, 1984). We also avoided culturing because in vitro conditions can affect important factors such as food quality or colony size (Rothhaupt, 1995;Verschoor et al, 2007). We worked with organisms freshly isolated from the lakes to guarantee near-natural conditions.…”