Bioturbation changes the patterns of benthic emergence in zooplankton

Abstract

We investigated the effects of two functionally different deposit feeders, the amphipod Monoporeia affinis and the bivalve Macoma balthica, on the benthic emergence of copepods (Acartia spp., Eurytemora affinis, Temora longicornis), cladocerans (Bosmina longispina maritima, Daphnia spp.), and rotifers (Synchaeta spp., Keratella spp., Notholca spp.) in the northern Baltic Sea. We performed 3.5-week laboratory experiments in June-July and in September-October using surface sediment containing zooplankton eggs and various combinations of amphipod and bivalve densities. Both zoobenthic species increased egg mortality rates in Synchaeta spp. and in calanoids. Each amphipod consumed a maximum of one Synchaeta spp. egg and 31 calanoid eggs per day, while the bivalves consumed six Synchaeta and 143 calanoid eggs per day. Monthly consumption throughout the community matches or even exceeds the field densities of eggs. In summer, M. affinis decreased the daily emergence rate of Synchaeta spp. by 31-53% and of M. balthica by 57%. The effect on calanoids was less severe: the emergence rate of Acartia spp. and E. affinis was significantly suppressed only by M. balthica (the reduction was 48% and 28% in Acartia spp. and in E. affinis, respectively). T. longicornis was the only species that benefited from macrofauna: together the two zoobenthic species resulted in a 2.7-fold increase in the emergence of this calanoid. Bioturbation significantly influences the benthic emergence of zooplankton, with effects varying among species, and may thus affect the dynamics of pelagic populations.

Hexabromocyclododecane affects benthic-pelagic coupling in an experimental ecosystem

“…2, see S4 for details). Phosphorus recycling seems to have been less affected by faunal activity than nitrogen recycling, in line with results from other studies (Marinelli and Williams, 2003;Viitasalo et al, 2007;Norkko et al, 2013). This is likely in part explained by the strong dependence of phosphorus a Water concentrations not measured; % for these treatments were estimated using water concentration data from the nearest available treatment multiplied by the ratio in nominal amounts.…”

“…In our experiment, indirect effects were mediated by the benthic community. Although sediment mixing by M. balthica may promote copepod benthic emergence, high predation on calanoid eggs (Viitasalo et al, 2007) reduces egg availability considerably. The shallow water depth in the mesocosm may have allowed sinking of copepod eggs throughout the experiment, which by T231 encountered favourable conditions (i.e.…”

Benthic fauna affects recruitment from sediments of the harmful cyanobacterium Nodularia spumigena

“…Similarly, Stå hl-Delbanco and Hansson (2002) found that an active bioturbator (an isopod) had a larger positive effect on the recruitment of freshwater cyanobacteria than a less active one (an arthropod larva). Furthermore, Viitasalo et al (2007) found that resuspension by M. affinis may enhance the hatching of zooplankton eggs in surface sediment, but that predation on eggs cancels this positive effect at high amphipod densities.…”

A field experiment demonstrating risk on the seafloor for planktonic embryos

“…While near the sediment surface, these resting eggs remain vulnerable to predators, but at least some can survive passage through a gut. Bioturbation, sometimes including ingestion, brings buried resting eggs to the surface for further development (Marcus and Schmidt‐Gengenbach ; Viitasalo et al ). In contrast, benthic embryos of most marine animals do not undergo prolonged arrested development and do not survive ingestion, sulfide, or prolonged anoxia, although embryos of some benthic harpacticoid copepods tolerate sulfide as well as anoxia (Vopel et al ) and the horseshoe crab Limulus buries clutches of embryos that can tolerate days of hypoxia (Palumbi and Johnson ).…”