Effects of bioturbation by three macrozoobenthic species and predation by necto-benthic mysids on cladoceran benthic eggs

Abstract

The effects of bioturbation and predation by the amphipod Monoporeia affinis, the bivalve Macoma balthica and the polychaetes Marenzelleria spp. were studied on the number, vertical distribution and hatching of benthic eggs (ephippia) of the cladoceran Bosmina longispina maritima. It was hypothesised that the 3 functionally different macrobenthic species affect Bosmina ephippia to different degrees. In addition, it was hypothesised that macrofaunal bioturbation either inhibits or enhances predation by the necto-benthic mysid Mysis mixta on cladoceran benthic eggs. M. affinis and M. balthica caused a 48 and 23% decrease in the total number of Bosmina ephippia, respectively, indicating egg predation. In addition, M. balthica extended the distribution of eggs into deeper sediment layers. Both M. affinis and M. balthica suppressed the daily hatching rate of Bosmina, and the effect of the bivalves (reduction 92%) was stronger than that of the amphipods (34 to 78%). None of the benthic species promoted the predation of mysids on Bosmina eggs. Instead, both M. affinis and M. balthica reduced the number of ephippia in the sediment surface (by 79 and 43%, respectively), implying that these species decrease the ability of mysids to feed on cladoceran benthic eggs. M. balthica was the most harmful species for the recruitment of Bosmina, whereas the nonindigenous Marenzelleria spp. did not affect ephippia.

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“…Experimental documentation of the effects of macrofauna on the recruitment of resting eggs to plankton are few, however (Albertsson and Leonardsson 2001;Stå hl-Delbanco and Hansson 2002;Viitasalo 2007). Here we present evidence that two surface deposit feeders, Monoporeia affinis and Macoma balthica, alter the patterns of zooplankton emergence in a way that reflects their species-specific traits and that depends on the zooplankton taxon and the season.…”

“…As a result, faunal-mediated egg burial inhibits benthic emergence (Albertsson and Leonardsson 2001;Viitasalo 2007), whereas upward transport may promote it (Kearns et al 1996;Marcus and Schmidt-Gengenbach 1986). In addition to translocation, predation on benthic resting stages can be potentially intense (Albertsson and Leonardsson 2001;Persson and Rosenberg 2003;Viitasalo 2007), although the importance of such regulation is not well known.…”

“…Emergence from the seafloor is strongly species-specific and often seasonally restricted, but it may essentially contribute to pelagic populations, as demonstrated for copepods (De Stasio 1990;Katajisto et al 1998;Hairston et al 2000) and cladocerans (Kankaala 1983;Onbé 1985;Cá ceres 1998). Investment in a benthic egg or seed bank is not, however, a risk-free strategy: feeding and burrowing of zoobenthos may strongly influence the dormant life stages of plankton (e.g., Albertsson and Leonardsson 2001;Giangrande et al 2002;Viitasalo 2007). …”

“…The depositfeeding amphipod Monoporeia affinis Lindströ m (hereafter Monoporeia) decreases hatching of the copepod Eurytemora affinis in the Baltic Sea (Albertsson and Leonardsson 2001), and both Monoporeia and the deposit-and suspension-feeding bivalve Macoma balthica (L.) (hereafter Macoma) inhibit hatching of the cladoceran Bosmina longispina maritima (Viitasalo 2007). However, since there are large differences in resistance of the benthic eggs of different zooplankton taxa to various stresses (reviews by Gilbert [1974]; Marcus [1996]; Gyllströ m and Hansson [2004]), results for single species cannot be extrapolated to other species or areas.…”

Mechanisms for copepod resting egg accumulation in seagrass sediments

“…Benthic macrofauna tend to be more diverse and abundant in seagrass beds than in unvegetated sediments (Lee et al 2001) and could promote egg retention through burial or egg loss through predation (Marcus and Schmidt-Gengenbach 1986;Viitasalo 2007;Karlson and Viitasalo-Frö sen 2009). Seagrass blade presence could contribute to egg retention by baffling water flow and inhibiting the resuspension of settled eggs (Fonseca et al 1982;Gambi et al 1990).…”