Resource partitioning among cladocerans in a littoral macrophyte zone: implications for the transfer of essential compounds

Abstract

International audienceThe maintenance of species diversity in a given environment is strongly linked to resource partitioning. Littoral macrophyte zones are heterogeneous environments with high microcrustacean diversity, where zooplankton have dietary access to seston as well as organisms growing on macrophytic surfaces (epiphyton). We conducted a field study in a macrophyte-rich backwater of the river Allier to examine how seston and epiphyton were used as potential food sources by four dominant cladoceran species. Fatty acids were analyzed in these two food sources to assess how their differential uptake affects the trophic trajectory of essential compounds from these resources to cladocerans. Our results showed resource partitioning among the four cladocerans studied; while Eurycercus fed mostly on epiphyton, Daphnia mostly consumed phytoplankton, and Ceriodaphnia and Simocephalus were able to forage on sestonic and epiphytic resources. Based on their polyunsaturated fatty acid (PUFA) content, it was evident that epiphyton was of higher food quality than seston in this macrophyte-rich backwater system. Variability of PUFA compositions of seston and epiphyton, and diversity of foraging strategies of cladoceran species, which represent the major link between microorganisms and consumers at higher trophic levels, affect dietary energy pathways and point to a variable PUFA transfer efficiency in backwater food webs

Spatial and seasonal variability of the carbon isotopic signature of Daphnia and their ephippia in four French lakes: Implications for the study of carbon transfers in lake food webs

“…Throughout the summer stratification period, the δ 13 C Daphnia values were very close to the δ 13 C seston values in all four lakes studied. The slight differences found between the signatures of Daphnia and seston (averaging 0.4‰ during the summer stratification period) are similar to those already reported in the literature (del Giorgio & France, 1996; Grey et al, 2000; Masclaux et al, 2014; Morlock et al, 2017; Schilder et al, 2017). At that time of the year, seston is mainly composed of phytoplankton, and it is likely that most of the carbon assimilated by Daphnia comes from phytoplankton during this period, even if we cannot totally exclude other food sources.…”

Species identity matters when interpreting trophic markers in aquatic food webs

“…These relationships did not completely align with other studies (e.g., [ 31 , 33 , 34 ]), but this inconsistency may be explained by a single, important diet item in the fishes collected. Chydorids are benthic-oriented microcrustaceans that feed primarily on epiphyton [ 49 , 50 ]. Chydorids and other benthic invertebrates may serve as EPA-rich prey items to fish [ 31 , 33 ], and EPA is thought to be an important fatty acid for zooplankton growth and fitness [ 51 ].…”

The comparison of the feeding of European perch Perca fluviatilis L. larvae in littoral and pelagic habitats of northern temperate lakes

“…Another important issue is the nutritional quality of zooplankton in littoral and pelagic areas as that is the key factor sustaining larval growth. Masclaux et al (2014) assessed the fatty acid composition of epiphyton and seston in the macrophyte rich littoral zone. They found that the epiphyton that can possibly provide an important dietary source for cladocerans in the littoral had higher content of nutritionally essential compounds of poly unsaturated fatty acids (PUFA) compared to the seston.…”