Transformation of the offshore benthic community in Lake Michigan: recent shift from the native amphipod Diporeia spp. to the invasive mussel Dreissena rostriformis bugensis

Abstract

Summary 1. The native amphipod Diporeia spp. was once the dominant benthic organism in Lake Michigan and served as an important pathway of energy flow from lower to upper trophic levels. Lake‐wide surveys were conducted in 1994/1995, 2000 and 2005, and abundances of Diporeia and the invasive bivalves Dreissena polymorpha (zebra mussel) and Dreissena rostriformis bugensis (quagga mussel) were assessed. In addition, more frequent surveys were conducted in the southern region of the lake between 1980 and 2007 to augment trend interpretation. 2. Between 1994/1995 and 2005, lake‐wide density of Diporeia declined from 5365 to 329 m−2, and biomass (dry weight, DW) declined from 3.9 to 0.4 g DW m−2. The percentage of all sites with no Diporeia increased over time: 1.1% in 1994/1995, 21.7% in 2000 and 66.9% in 2005. On the other hand, total dreissenid density increased from 173 to 8816 m−2, and total biomass increased from 0.4 to 28.6 g DW m−2. Over this 10‐year time period, D. r. bugensis displaced D. polymorpha as the dominant dreissenid, comprising 97.7% of the total population in 2005. In 2007, Diporeia was rarely found at depths shallower than 90 m and continued to decline at greater depths, whereas densities of D. r. bugensis continued to increase at depths greater than 50 m. 3. The decline in Diporeia occurred progressively from shallow to deep regions, and was temporally coincident with the expansion of D. polymorpha in nearshore waters followed by the expansion of D. r. bugensis in offshore waters. In addition, Diporeia density was negatively related to dreissenid density within and across depth intervals; the latter result indicated that dreissenids in shallow waters remotely influenced Diporeia in deep waters. 4. With the loss of Diporeia and increase in D. r. bugensis, the benthic community has become a major energy sink rather that a pathway to upper trophic levels. With this replacement of dominant taxa, we estimate that the relative benthic energy pool increased from 17 to 109 kcal m−2 between 1994/1995 and 2005, and to 342 kcal m−2 by 2007. We project that previously observed impacts on fish populations will continue and become more pronounced as the D. r. bugensis population continues to expand in deeper waters.

Seasonal zooplankton dynamics in Lake Michigan: Disentangling impacts of resource limitation, ecosystem engineering, and predation during a critical ecosystem transition

“…At the same time, macroinvertebrates favored as prey by planktivorous fishes-Diporeia spp. and Mysis-have both decreased with the former species nearly disappearing (Nalepa et al, 2009;Pothoven et al, 2010). Declines in these key macroinvertebrates may ultimately lead to declines in prey fish biomass.…”

“…Through time, this could result in lower spawning stock biomass and lower fecundity (see Bunnell et al, 2009a) and eventually lead to reduced recruitment for these prey fish species that historically relied upon Diporeia. Whether or not the expansion of quagga mussels in recent years is driving the declines in planktivorous prey fish biomass remains an ongoing debate (see Bunnell et al, 2009b;Nalepa et al, 2009). On the other hand, the decrease in alewife abundance may have been a result of increased predation by Chinook salmon.…”

The role of organisms in hyporheic processes: gaps in current knowledge, needs for future research and applications

“…Finally, future global change will also consist of an increase in the frequency of invasive species. This problem has been widely discussed for surface aquatic systems, both lakes (Gurevitch and Padilla, 2004;Nalepa et al, 2009) and rivers (Dukes and Mooney, 1999;Piscart et al, 2005Piscart et al, , 2010Piscart et al, , 2011Werner and Rothhaupt, 2007;Strayer, 2010;Labat et al, in press). For the hyporheic zone, the occurrence of invasive species is not yet documented even if some invasive isopods and amphipods were already observed (C. Piscart, personal communication).…”

Reproduction and genetic detection of veligers in changingDreissenapopulations in the Great Lakes

“…The greater fecundity of D. polymorpha may provide an explanation for the more rapid dispersion of D. polymorpha in the early stages of the dreissenid invasion. D. bugensis seem capable of growing at greater depths than D. polymorpha, a characteristic that may explain the availability of D. bugensis recruits even when D. polymorpha are the predominant species at shallower depths (Nalepa et al 2009). The present study agrees with previous reports that D. bugensis become reproductively mature earlier in the season (Stoeckmann 2003) and spawn at lower temperatures than D. polymorpha (Roe andMacIsaac 1997, Claxton andMackie 1998).…”