Invasive ecosystem engineers on soft sediment change the habitat preferences of native mayflies and their availability to predators

Abstract

1. Dreissenid mussels (quagga mussels, Dreissena bugensis, and zebra mussels, D. polymorpha) are invasive species that function as ecosystem engineers in the Laurentian Great Lakes. Dreissena are increasingly abundant on silt, sand and other soft substrates; by altering benthic habitat, these mussels can alter benthic community structure. 2. We used laboratory mesocosm experiments to examine the effects of soft-sediment Dreissena clusters on the habitat preference of Hexagenia, a native burrowing mayfly that is an important food source to fish. We conducted three experiments to test whether Hexagenia: (1) select for bare sediment, soft sediment covered with live Dreissena (added structure and food resources) or soft sediment with clusters made of empty Dreissena shells (added structure only), (2) prefer a specific density of live Dreissena on soft sediment and (3) select for or avoid sediment with an accumulation of empty Dreissena shells. 3. Contrary to initial expectations, we found that Hexagenia selected for sediment covered with live Dreissena clusters, followed by empty Dreissena shells clusters, and lastly what was previously thought to be the preferred habitat, bare sediment. Not only did Hexagenia prefer Dreissena-covered sediment, but they also preferred high densities of Dreissena. 4. We also experimentally tested the effects of Dreissena-covered soft sediment on the availability of Hexagenia to fish. We had three treatment levels representing three distinct habitat types: (1) bare sediment (no Dreissena) treatment in which water was turbid because of mayfly activity, (2) Dreissena-covered sediment treatment in which water was clear because of Dreissena filtration and (3) Dreissena-covered sediment with added turbidity. We found that in low light conditions, similar to many locations where both organisms are found to co-occur, both yellow perch and round goby consumption of Hexagenia significantly decreased when Dreissena covered the bottom sediment. 5. These results suggest that by choosing Dreissena-covered habitat, Hexagenia receive protection from fish predation in turbid ⁄ low light systems. However, protection from predation cannot be the only reason Hexagenia select Dreissena-covered sediments, as Hexagenia selected for live clusters more often than empty clusters and may be a result of additional food resources.

Effectiveness of zebra mussels to act as shelters from fish predators differs between native and invasive amphipod prey

“…Avoiding predators is crucial for the survival and fitness of prey organisms, which develop defence mechanisms to decrease predation risk (Lima and Dill 1990;Lass and Spaak 2003). The phenomenon of predator-prey interactions is particularly interesting in the case of alien species, which, on the one hand, can provide shelters for other invaders, supporting them in novel areas (van Overdijk et al 2003;Gonzalez and Burkart 2004;Kobak et al 2009) and, on the other hand, can offer new, previously unavailable anti-predator refugia for native prey (Gonzalez and Downing 1999;van Overdijk et al 2003;DeVanna et al 2011).…”

“…In other words, the higher the number of invasives in a given area, the greater the probability of success of future invasions. However, existing evidence shows that native species can also benefit from zebra mussel habitats (Stewart et al 1999; Kestrup and Ricciardi 2009;DeVanna et al 2011), leaving the question on the role of this bivalve in the invasional meltdown phenomenon open.…”

The impact of zebra mussel (Dreissena polymorpha) periostracum and biofilm cues on habitat selection by a Ponto-Caspian amphipod Dikerogammarus haemobaphes

“…A snail Physella heterostropha (Say, 1871) selected empty mussel shells in the presence of predator kairomones (Stewart et al, 1999) and a mayfly Hexagenia sp. occupied bivalve clusters hiding from predatory fish (DeVanna et al, 2011). Furthermore, some benthivores, such as Ponto-Caspian neogobiid fish were found to avoid shell habitats (Kakareko, 2011), which increases the role of mussel beds as anti-predator shelters.…”

“…Zebra mussels affect positively not only other aliens, but also many local species (Wolnomiejski, 1970;Kestrup & Ricciardi, 2009;DeVanna et al, 2011). However, their presence may be much more crucial for Ponto-Caspian invaders, as mussels transform novel, likely inhospitable environments into habitats similar to those occurring in their native regions.…”

“…Therefore, this bivalve is often used as a model example supporting the meltdown hypothesis (Simberloff & Von Holle, 1999). On the other hand, a growing body of evidence shows that native taxa, such as amphipods and ephemeropterans evolving allopatrically with zebra mussels, can benefit from the presence of mussel colonies to the same extent as aliens, thus questioning the role of dreissenids in the invasional meltdown (Kestrup & Ricciardi, 2009;DeVanna et al, 2011).…”