Trophic position of zebra mussel veligers and their use of dissolved organic carbon

Abstract

We evaluated by stable isotope analysis the trophic structure of an estuarine transition zone (ETZ) food web and the role of an invasive species, the veliger stage of the zebra mussel Dreissena polymorpha. In the St. Lawrence ETZ, where zebra mussel veligers are now the dominant zooplankton in summer, d 13 C ranged from 231.2% (seston) to 216.1% (adult fish) and d 15 N ranged from 2.6% to 17.4%. Isotopic analysis of samples indicated that the overall food web was largely supported by autochthonous phytoplankton rather than by allochthonous terrestrial carbon. Large differences among the isotopic signals of veligers, cladocerans, and copepods suggested the use of different proportions of food items, and the isotopic values of fish larvae indicated no significant assimilation of veligers. The d 13 C signature of the veligers was in a range consistent with feeding on free-living bacteria and dissolved organic carbon (DOC) or both, and freshwater algae incubated in situ. To investigate the possibility of DOC uptake by the veligers, we incubated veligers on 14 C-labelled algal lysates. There was rapid uptake of DOC and incorporation into biomass, equivalent to 6% of the soft tissue dry weight per hour. Zebra mussel veligers are likely using autochthonous DOC as an alternate food source, and they occupy an exotic trophic position in which there is little direct interaction with other major components of the ETZ food web.

Trophic dynamics of two sympatric mysid species in an estuarine transition zone

“…Thus, the pool of suspended organic matter is unlikely to have an important role in the nutrition of mysids, in contrast to what has been reported in other studies (Lasenby & Langford 1973, Jansen 1985, Fockedey & Mees 1999. The ETZ consumer food web in the St. Lawrence Middle Estuary appears to be only weakly coupled with overall particulate organic matter and therefore only loosely linked to decomposer pathways (Martineau et al 2004, Barnard et al 2006, which is consistent with our results; the 2 mysid species were supported by the zooplankton productivity of the ETZ, which is, in turn, supported by autochthonous carbon.…”

“…Details on field sampling and isotopic analysis are described in Martineau et al (2004) and Barnard et al (2006). Briefly, zooplankton samples for isotopic analysis were obtained by horizontal trawls during 3 cruises in summer 2001 (10 July, 20 July and 1 August) at 3 stations across the ETZ (northern, middle and southern channel) using a 500 and 64 μm net for mysids and other zooplankton species, respectively.…”

Water moss as a food item of the zoobenthos in the Yenisei River

“…The stable isotope ratios were given in the conventional differential δ-notation: [14,[26][27][28]. The taxonomic group of zoobenthos with the lowest δ 15 N was selected as the baseline for estimating the TPs of other taxa [14].…”

Dissolved organic matter and persistence of the invasive zebra mussel (Dreissena polymorpha) under low food conditions

“…Coupled with studies proving that adult and larval zebra mussels are capable of efficiently absorbing specific dissolved organic compounds (especially amino acids and fatty acids) at environmentally realistic concentrations (Roditi et al 2000;Baines et al 2005;Barnard et al 2006), our results suggest that zebra mussels gain significant metabolic benefits from absorbing DOM directly from the water. This study represents a distinct advance over previous work on the role of DOM in adult bivalve metabolism in that it directly measured the effect of DOM exposure on a physiological endpoint of great ecological importance.…”

“…However, recent work clearly shows that zebra mussels are unique among the freshwater organisms that have so far been studied in this regard; they can take up dissolved free amino and fatty acids very efficiently at natural concentrations (Baines et al 2005). Significant DOM uptake is also exhibited by larval zebra mussels (Barnard et al 2006). Furthermore, the estimated amount of DOM taken up by adults is equivalent to 10-50% of the typical ration required for zebra mussels to maintain constant weight (Roditi et al 2000;Baines et al 2005).…”