Short-term post-mortality scavenging and longer term recovery after anoxia in the northern Adriatic Sea

Blasnig, M.; Riedel, Bettina; Schiemer, L.; Zuschin, Martin; Stachowitsch, Michael

doi:10.5194/bg-10-7647-2013

Cited by 13 publications

(13 citation statements)

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“…We assume this is also linked to the reduced grazing pressure of survivors (see De . Clearly, regardless of the mechanism and strategy, recovery in harpacticoid copepods and foraminifera was much more rapid than in the macrofauna (Blasnig et al, 2013).…”

Section: Discussionmentioning

confidence: 97%

Meiofauna winners and losers of coastal hypoxia: case study harpacticoid copepods

et al. 2014

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Abstract. The impact of anoxia on meiobenthic copepod species was assessed by means of a field experiment. Four plexiglass chambers were deployed in situ in 24 m depth to simulate an anoxic event of 9 days, 1 month, 2 months and 10 months. From normoxic to anoxic conditions, we recorded a drop in copepod density and species richness. With increasing duration of anoxia the relative abundance of the individuals of the family Cletodidae increased, and they survived the 1 month and 2 month anoxia, the latter with few specimens. They were the true "winners" of the experimentally induced anoxia. Dominance did not increase in the deployments because not one, but several species from this family were tolerant to anoxia. The overall rate of survival was the same for males and females, but no juvenile stages of copepods survived in anoxia. During a recovery phase of 7 days after a short-term anoxia of 9 days, harpacticoid copepod density did not increase significantly, and there was only a slight increase in species diversity. We concluded that no substantial colonisation from the surrounding sediment took place. The survivors, however, showed a high potential for recovery according to the number of gravid females, whose number increased significantly once the oxygen was available again. These findings imply that substantial energy is allocated to reproduction in the recovery phase.

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Section: Discussionmentioning

confidence: 97%

Meiofauna winners and losers of coastal hypoxia: case study harpacticoid copepods

et al. 2014

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“…The interactive and cumulative effects of multiple human stressors increasingly force the system to a critical tipping point and qualitatively altered state. meiofauna responses (foraminiferans: Langlet et al 2013a, b; harpacticoid copepods: Grego et al, 2013Grego et al, , 2014De Troch et al, 2013), and immediate post-anoxia scavenging and longer-term recovery (Blasnig et al, 2013) are treated elsewhere in this special issue.…”

Section: B Riedel Et Al: Effect Of Hypoxia and Anoxia On Invertebramentioning

confidence: 99%

Effect of hypoxia and anoxia on invertebrate behaviour: ecological perspectives from species to community level

et al. 2014

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Abstract. Coastal hypoxia and anoxia have become a global key stressor to marine ecosystems, with almost 500 dead zones recorded worldwide. By triggering cascading effects from the individual organism to the community-and ecosystem level, oxygen depletions threaten marine biodiversity and can alter ecosystem structure and function. By integrating both physiological function and ecological processes, animal behaviour is ideal for assessing the stress state of benthic macrofauna to low dissolved oxygen. The initial response of organisms can serve as an early warning signal, while the successive behavioural reactions of key species indicate hypoxia levels and help assess community degradation. Here we document the behavioural responses of a representative spectrum of benthic macrofauna in the natural setting in the Northern Adriatic Sea (Mediterranean). We experimentally induced small-scale anoxia with a benthic chamber in 24 m depth to overcome the difficulties in predicting the onset of hypoxia, which often hinders full documentation in the field. The behavioural reactions were documented with a time-lapse camera. Oxygen depletion elicited significant and repeatable changes in general (visibility, locomotion, body movement and posture, location) and species-specific reactions in virtually all organisms (302 individuals from 32 species and 2 species groups). Most atypical (stress) behaviours were associated with specific oxygen thresholds: arm-tipping in the ophiuroid Ophiothrix quinquemaculata, for example, with the onset of mild hypoxia (< 2 mL O 2 L −1 ), the emergence of polychaetes on the sediment surface with moderate hypoxia (< 1 mL O 2 L −1 ), the emergence of the infaunal sea urchin Schizaster canaliferus on the sediment with severe hypoxia (< 0.5 mL O 2 L −1 ) and heavy body rotations in sea anemones with anoxia. Other species changed their activity patterns, for example the circadian rhythm in the hermit crab Paguristes eremita or the bioherm-associated crab Pisidia longimana. Intra-and interspecific reactions were weakened or changed: decapods ceased defensive and territorial behaviour, and predator-prey interactions and relationships shifted. This nuanced scale of resolution is a useful tool to interpret present benthic community status (behaviour) and past mortalities (community composition, e.g. survival of tolerant species). This information on the sensitivity (onset of stress response), tolerance (mortality, survival), and characteristics (i.e. life habit, functional role) of key species also helps predict potential future changes in benthic structure and ecosystem functioning. This integrated approach can transport complex ecological processes to the public and decision-makers and help define specific monitoring, assessment and conservation plans.

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“…They were designed to better understand how anoxia affects benthic macrofauna and meiofauna survival and how fast the impacted zone attains a new ecological equilibrium. The main objective was to simulate short-to longer-term bottom-water anoxia and to study the survival, resilience and recolonization of different groups of benthic organisms (macrofauna Blasnig et al, 2013;Riedel et al, , 2012, meiofauna such as foraminifera (Langlet et al, , 2014, nematodes and copepods (Grego et al, , 2014De Troch et al, 2013), which are expected to respond differently to anoxia. Seasonal changes in bottom-water oxygenation are known to induce vertical migrations of the major redox fronts in the sediment, modifying vertical separation between redox-sensitive elements.…”

Section: Published By Copernicus Publications On Behalf Of the Europementioning

confidence: 99%

Artificially induced migration of redox layers in a coastal sediment from the Northern Adriatic

et al. 2014

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Abstract. Long-term experimental studies suggest that, under transient anoxic conditions, redox fronts within the sediment shift upwards, causing sequential rise and fall of benthic fluxes of reduced species (Mn(II), Fe(II) and S(-II)). Infaunal benthic organisms are associated with different redox fronts as micro-habitats and must be affected by such changes during natural hypoxia events. In order to document the geochemical evolution of the sediment during prolonged anoxia in the framework of an in situ experiment designed to mimic natural conditions, benthic chambers were deployed on the seafloor of the Northern Adriatic and sampled after 9, 30 and 315 days of incubation. Oxygen and sulfide were measured continuously in the early stages (9 days) of the experiment. High-resolution pore water profiles were sampled by DET probes and redox-sensitive species (S(VI), Mn(II) and Fe(II)) and alkalinity were measured.Starting oxygen saturation was about 80 % within the chamber. After 7 days, anoxia was established in the bottom waters within the chambers. Mn(II) and Fe(II) started diffusing towards the anoxic water column until they reached the surficial sediment. Being reoxidized there, Mn and Fe reprecipitated, giving a rusty coloration to the seafloor. Infaunal species appeared at the sediment surface. After 20 days, all macro-organisms were dead. Decomposition of macroorganisms at the sediment-water interface generated S(-II) within the entire height of the chamber, leading to a downward flux of sulfides into the sediment, where they were quickly oxidized by metallic oxides or precipitated as FeS. S(-II) was below detection in the water column and pore waters at the end of the experiment. Our results suggest that S(-II) enrichment in the water column of coastal systems, which are episodically anoxic, is strongly controlled by the biomass of benthic macrofauna and its decay during anoxia, whereas its residence time in the water column is controlled by iron availability (as solid oxides or as dissolved reduced cations) within the sediment, even without water circulation.

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Short-term post-mortality scavenging and longer term recovery after anoxia in the northern Adriatic Sea

Cited by 13 publications

References 61 publications

Meiofauna winners and losers of coastal hypoxia: case study harpacticoid copepods

Meiofauna winners and losers of coastal hypoxia: case study harpacticoid copepods

Effect of hypoxia and anoxia on invertebrate behaviour: ecological perspectives from species to community level

Artificially induced migration of redox layers in a coastal sediment from the Northern Adriatic

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