Effects of Food Removal on Nutrient Release Rates and Lipid Content of Lake Michigan Pontoporeia hoyi

Abstract

Pontoporeia hoyi, the dominant benthic invertebrate in the upper Great Lakes, appears to be well adapted to environments with seasonal inputs of high-quality food such as those supplied by the spring diatom bloom. Ammonium and phosphate excretion rates and lipid content were examined in P. hoyi under the following conditions: (1) field animals sampled seasonally, (2) food-deprived animals in filtered lake water, and (3) control animals held in native sediments without new food inputs. Nutrient excretion rates for P. hoyi (0.5 to 2 nmole NH4 (milligrams dry weight)−1∙h−1 and 0 to 0.15 nmole PO4 (milligrams dry weight)−1∙h−1) were low relative to rates previously reported for other benthic and pelagic invertebrates and varied little among the three treatment groups. In contrast to the animals held in the laboratory without new food inputs, field-collected P. hoyi accumulated increased levels of lipids following the spring diatom bloom. However, after lipid levels in field animals peaked in May, they decreased during the rest of the season at rates similar to those of starved and control animals. P. hoyi's low nutrient-excretion rates, and its ability to accumulate and store energy as lipids, for periods when food is not abundant, appear to be important factors allowing this animal to thrive in temperate lakes with spring diatom blooms.

Seasonal changes in lipid content and composition in the benthic amphipods Monoporeia affinis and Pontoporeia femorata

“…Amphipods that were deprived of food mobilized lipids during starvation, which supports the theory that this species accumulates lipids as an energy store after the spring bloom (Gardner et al 1985b;Gauvin et al 1989). …”

“…In M. a@nis and P. jkmorata from our study, lipid levels were not as high as those of D. hoyi from Lake Michigan, where the mean value was 30-40% of dry mass (Gardner et al 1985b;Gauvin et al 1989), but they are high compared with those of other amphipods (table 10 of Clarke et al 1985).…”

“…In July, when the gonads started developing, mean lipid levels in M. afinis and P. femorata were 27 and 23% of the dry mass. Mean lipid levels of gravid females were 23% in D. hoyi (Quigley et al 1989). …”

“…In D. hoyi, lipid levels of males were lower than those of females in December when the males matured, stopped feeding, and bccame pelagic (Quigley et al 1989). Males of the intertidal amphipod Echinogammarus marinus depleted their lipid reserves when carrying the females in amplexus (Clarke et al 1985).…”

Metabolite Profiles in Starved Diporeia spp. Using Liquid Chromatography-Mass Spectrometry (LC-MS) Based Metabolomics

“…Previous studies have found no significant changes in total body lipids of Diporeia after being starved for a month (Gauvin et al, 1989). Starvation of an European amphipod species, Monoporeia affinis, led to predominantly lipid-based energy metabolism (Lehtonen, 1994).…”