Bettina Riedel

Natural History Museum Vienna, Austria · Zoology I., Fish Collection

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 physi...

Oxygen depletion can lead to the collapse of benthic ecosystems, i.e. to dead zones, and large-scale biodiversity loss. Based on mortality and survival, we evaluated ranges of sensitivity and tolerance to hypoxia levels, duration of anoxia and H2S exposure across taxa and key life habits. Experiments were conducted on a sublittoral soft-bottom unde...

Anoxia was successfully induced in four benthic chambers installed at 24 m depth in the northern Adriatic Sea for periods varying from 9 days to 10 months. During the 10-month period, species richness significantly decreased. Al-though no significant change in Shannon diversity and even-ness was observed, the composition of the foraminiferal as-sem...

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...

Over the last decades, hypoxia in marine coastal environments has become more and more widespread, prolonged and intense. Hypoxic events have large consequences for the functioning of benthic ecosystems. In severe cases, they may lead to complete anoxia and the presence of toxic sulfides in the sediment and bottom-water, thereby strongly affecting...

Benthic foraminiferal pores are considered to play an important role in facilitating the gas exchange between the organism and the environment, with pore size and density supposed to be related to gas exchange intensity. Recent studies have therefore attempted to establish relationships between pore patterns and redox conditions, such as bottom wat...

Purpose Sequential nutrient regeneration and organic matter (OM) degradation were studied in surface coastal sediments of the Gulf of Trieste (northern Adriatic Sea). Materials and methods In situ benthic chambers were used under normoxic, anoxic and reoxic conditions. Diffusive benthic fluxes were calculated from pore water modelling using a diffu...

Anoxia was successfully induced in four benthic chambers installed at 24-m depth on the Northern Adriatic seafloor from 9 days to 10 months. To accurately determine whether benthic foraminifera can survive experimentally induced prolonged anoxia, the CellTracker Green method was applied and calcareous and agglutinated foraminifera were analyzed. Nu...

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 change...

The northern Adriatic Sea is one of nearly 500 areas worldwide suffering widespread mortalities due to anoxia. The present study documents post-anoxia macrofauna dynamics after experimentally inducing small-scale anoxia in 24m depth (2 plots, each 50 cm×50 cm). Timelapse camera deployments examined short-term scavenging of the moribund and dead org...

Anoxia was successfully induced in four benthic chambers installed at 24m depth on the northern Adriatic seafloor from 9 days to 10 months. To accurately determine whether benthic foraminifera can survive experimentally induced prolonged anoxia, the CellTracker™ Green method was applied and calcareous and agglutinated foraminifera were analyzed. Nu...

Coastal hypoxia and anoxia have become a global key stressor to marine ecosystems, with almost 500 dead zones recorded wordwide. By triggering cascading effects from the individual organism to the community and ecosystem-level, oxygen depletions threat marine biodiversity and can alter ecosystem structure and function. By integrating both physiolog...

Anoxia was successfully induced in four benthic chambers installed at 24 m depth in the northern Adriatic Sea, for periods varying from 9 days to 10 months. During the 10 months period, species richness significantly decreased. Although no significant change in Shannon diversity and Evenness is observed, the composition of the foraminiferal assembl...

Long term experimental studies suggest that, under anoxic transient conditions, redox fronts within the sediment shift upwards causing sequential rise and fall of benthic fluxes of reduced species (Mn(II), Fe(II) than S(-II)). Infaunal benthic organisms are associated to different redox fronts as micro-habitats and must be affected by such changes...

Sequential nutrient regeneration and organic matter (OM) degradation in surface sediments of the Gulf of Trieste (northern Adriatic Sea) were examined using in situ benthic chambers under normoxic, anoxic and reoxic conditions. Intensive NH4+ and PO4- anoxic regeneration was subsequently slower in prolonged anoxia. NH4+ production was probably also...

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...

Combined in situ and laboratory studies were conducted to document the effects of anoxia on the structure and functioning of meiobenthic communities, with special focus on harpacticoid copepods. In a first step, anoxia was created artificially by means of an underwater chamber at 24 m depth in the Northern Adriatic, Gulf of Trieste (Mediterranean)....

Anoxia has been successfully induced in four benthic chambers installed on the Northern Adriatic seafloor from 1 week to 10 months. To accurately determine whether benthic foraminifera can survive experimentally induced prolonged anoxia, the CellTrackerGreen method has been applied. Numerous individuals have been found living at all sampling times...

In the Mediterranean, the northern Adriatic Sea shows most features known to promote late-summer hypoxia and anoxia. These features, along with anthropogenic eutrophication and marine snow events, have led to repeated benthic mortalities here. The present study was designed to document the post-anoxia macrofauna dynamics. We deployed an underwater...

Hypoxia and anoxia have become a key threat to shallow coastal seas. Much is known about their impact on macrofauna, less on meiofauna. In an attempt to shed more light on the latter group, in particular from a process-oriented view, we experimentally induced short-term anoxia (1 week) in the northern Adriatic Sea (Mediterranean) and examined the t...

Hypoxia and anoxia have become a key threat to shallow coastal seas. Much is known about their impact on macrofauna, less on meiofauna. In an attempt to shed more light on the latter group, in particular from a process-oriented view, we experimentally induced short-term anoxia (1 week) in the Northern Adriatic Sea, Mediterranean, and examined the t...

Combined in situ and laboratory studies were conducted to document the effects of anoxia on the structure and functioning of meiobenthic communities, with special focus on harpacticoid copepods. In a first step, anoxia was created artificially by means of an underwater chamber at 24 m depth in the Northern Adriatic, Gulf of Trieste (Mediterranean)....

An increasing number of coastal seas is exposed to severe eutrophication, often resulting in seasonal hypoxia. In the Northern Adriatic Sea, marine snow events also develop every year in late summer to early autumn, further promoting severe hypoxia or anoxia at the sea floor. Consequently, benthic communities of the most exposed areas experience re...

Hermit crabs play an important role in the Northern Adriatic Sea due to their abundance, wide range of symbionts, and function in structuring the benthic community. Small-scale (0.25 m2) hypoxia and anoxia were experimentally generated on a sublittoral soft bottom in 24 m depth in the Gulf of Trieste. This approach successfully simulates the season...

Tab. 1. Results of Mann-Whitney U-test for behavioural differences in the number of observations in the five oxygen categories: all Paguristes eremita individuals. Comparison refers to oxygen categories: 1: normoxia; 2: mild hypoxia; 3: moderate hypoxia; 4: severe hypoxia; 5: anoxia. Bold: highly significant (P < 0.001); Underlined numbers: signifi...

Anoxia is a key issue in the past and present marine ecosystems. This is because no other form of disturbance so severely affects marine communities over such extensive areas. Anoxia is also the only manifestation of human-induced disturbance that was also an important factor in ancient systems. While microorganisms may rule the Earth, it is fundam...

Crustaceans are sensitive to hypoxia and are therefore useful indicator organisms for oxygen depletions. We used the experimental anoxia generating unit in the northern Adriatic Sea to artificially induce and document hypoxia and anoxia on a small scale (0.25 m2 per deployment). Behavioural responses and mortalities were documented for 9 crustacean...

Hypoxia and anoxia are key threats to modern shallow coastal ecosystems worldwide and both their frequency and intensity have increased dramatically over recent decades. In the Adriatic Sea, hypoxic events may affect up to 3000 km² of the seafloor, leading to extensive mass mortalities of the benthos. The onset of these catastrophic events, however...

No other environmental parameter in shallow coastal ecosystems worldwide has changed as dramatically as dissolved oxygen (DO). Nearly 400 hypoxic (<2 ml l-1) and anoxic areas have been identified and the number is expected to increase. Such "dead zones" cause cascading effects from the molecular to the ecosystem level. Ultimately, biodiversity loss...

One predicted effect of global climate change, specifically global warming, is the increase in the temperatures and stratification of shallow coastal and estuarine systems. This, coupled with ongoing anthropogenic eutrophication, will exacerbate hypoxia and benthic mortalities, significantly damaging these critical marine ecosystems. These phenomen...

Hexaplex trunculus (Linnaeus, 1758) is one of the most abundant and widespread muricid gastropods in the Northern Adriatic Sea, but relatively little is known about the feeding ecology of this predator. We examined the activity of H. trunculus on a sublittoral mussel bed at 24 m depth through in situ time-lapse observations and bulk samples. The ca...

The Northern Adriatic Sea experiences seasonal low dissolved oxygen (DO) events and mortality of benthic organisms. The onset and extent of such disturbances, however, are difficult to forecast and study in the field. We address this problem by deploying a device that artificially induces and documents small-scale anoxia on soft-bottom in 24 m dept...

During oxygen crises, benthic faunas exhibit a series of behavioural patterns that reflect the duration and severity of the event. During artificially induced oxygen deficiencies at 24 m depth in the Northern Adriatic Sea, we photographically documented predation by the sea anemones Cereus pedunculatus (Pennant, 1777) and Calliactis parasitica (Cou...

Shallow coastal seas are most endangered and, through a series of impacts ranging from overfishing, eutrophication to coastal development, they are likely to experience the largest change in biodiversity, should present trends in human activity continue. No other crucial environmental variable has changed more drastically in shallow coastal marine...

Oxygen depletion events and anoxia are a key threat to shallow marine coastal seas worldwide. The mortalities they trigger, however, are difficult to document in full. We developed an underwater device to experimentally induce hypoxia and anoxia on the seafloor. The EAGU (Experimental Anoxia Generating Unit) combines a time-lapse camera and flashes...