Publikationsdatum:
2014-10-07
Beschreibung:
In this paper we provide an overview of new
knowledge on oxygen depletion (hypoxia) and related phenomena
in aquatic systems resulting from the EU-FP7
project HYPOX (“In situ monitoring of oxygen depletion in
hypoxic ecosystems of coastal and open seas, and landlocked
water bodies”, www.hypox.net). In view of the anticipated
oxygen loss in aquatic systems due to eutrophication and climate
change, HYPOX was set up to improve capacities to
monitor hypoxia as well as to understand its causes and consequences.
Temporal dynamics and spatial patterns of hypoxia were
analyzed in field studies in various aquatic environments, including
the Baltic Sea, the Black Sea, Scottish and Scandinavian
fjords, Ionian Sea lagoons and embayments, and Swiss
lakes. Examples of episodic and rapid (hours) occurrences of
hypoxia, as well as seasonal changes in bottom-water oxygenation
in stratified systems, are discussed. Geologically
driven hypoxia caused by gas seepage is demonstrated. Using
novel technologies, temporal and spatial patterns of watercolumn
oxygenation, from basin-scale seasonal patterns to
meter-scale sub-micromolar oxygen distributions, were resolved.
Existing multidecadal monitoring data were used to
demonstrate the imprint of climate change and eutrophication
on long-term oxygen distributions. Organic and inorganic
proxies were used to extend investigations on past oxygen
conditions to centennial and even longer timescales that
cannot be resolved by monitoring. The effects of hypoxia on
faunal communities and biogeochemical processes were also
addressed in the project. An investigation of benthic fauna is
presented as an example of hypoxia-devastated benthic communities
that slowly recover upon a reduction in eutrophication
in a system where naturally occurring hypoxia overlaps
with anthropogenic hypoxia. Biogeochemical investigations
reveal that oxygen intrusions have a strong effect on the microbially
mediated redox cycling of elements. Observations
and modeling studies of the sediments demonstrate the effect
of seasonally changing oxygen conditions on benthic mineralization
pathways and fluxes. Data quality and access are
crucial in hypoxia research. Technical issues are therefore
also addressed, including the availability of suitable sensor
technology to resolve the gradual changes in bottom-water
oxygen in marine systems that can be expected as a result of
climate change. Using cabled observatories as examples, we
show how the benefit of continuous oxygen monitoring can
be maximized by adopting proper quality control. Finally,
we discuss strategies for state-of-the-art data archiving and
dissemination in compliance with global standards, and how
ocean observations can contribute to global earth observation
attempts.
Repository-Name:
EPIC Alfred Wegener Institut
Materialart:
Article
,
isiRev
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