How might human activities and climate change impact on
the health of our seas?
Marine Theme Objective: Human Pressures and Impacts on the Marine Environment
What’s the problem?
We want ‘clean, healthy, safe, productive and biologically diverse’ oceans and seas. To achieve this we need to manage
human activities in a way that minimises their impact. The problem is that we don’t fully understand the impacts of climate
change and human activity on the marine environment, nor how much disturbance it can take before it stops being able to
provide the goods (e.g. fish) and services (e.g. the cycling of carbon) we take from it. It is assumed that a marine system
which is biodiverse is ‘good’, as it provides a range of different habitats and species, thus making it more ‘resilient’ to
impacts. This project intends to help us understand the link between biodiversity and a healthy functioning system and how
climate change and human activities affect these links. This understanding will help us to manage the marine environment
more effectively.
What are the aims of the project?
The key to avoiding ecosystem dysfunction is improving
the understanding of the connections between
important parts of the ecosystem such as flows of
materials such as Carbon (C), Nitrogen (N), Oxygen
(O), Silicon (Si) and energy, and to determine key
connections that are susceptible to change due to
pressures such as human activity and climate changes.
To help understand these links the aim of this research
is to look at:
 key processes such as the controls on production
and fate of Carbon, and how the water column and
sea-bed interact to cycle Carbon in the marine
environment; and
 what parts of the marine ecosystem are key to
delivering these processes.
Models will be used to look at changes in key processes
under different scenarios, for example aspects of
climate change and human activity (specifically
trawling).
Indicators which can be used to describe the state and
change in these processes will also be developed
during the course of the project which is due to
complete in March 2011.
Figure 1: Key elements of ecosystem structure & function in shelf seas. Carbon
is cycled through food webs in the water column and the seabed. Connectivity
between planktonic and benthic food webs is essential for ecosystem health
and productivity, and is susceptible to climate change and human activity.
Which policy areas will the research
inform?
Policy areas dealing with the assessment of human and
climate impacts such as the Marine Strategy Framework
Directive will be able to use this information to inform the
development of Good Environmental Status descriptors
of seabed integrity, food-webs and biodiversity. Data will
also be used to communicate the effect of climate
change to the public. Findings may also be useful in
informing decisions on the placement and management
of Marine Protected areas by assessing the effects of
fishing effort redistributions on water and sediment
functions (carbon and nutrient cycling, benthic
production, plankton production).
ME3205: Marine Ecosystem Connections: Essential indicators of healthy, productive & diverse seas
How might climate change and human activities impact on the health of our seas?
What are the results from the project and
how will they be used?
Importance of biodiversity in cycling of C and N:
Work to date has concentrated on flows of carbon and
nutrients in the North Sea in three study sites. It’s been
found that primary production by phytoplankton in the
water column during the growth season appears to be
rapidly consumed and recycled by diverse communities of
animal plankton. Seabed carbon cycling in shallow areas
with a permanently well mixed water column is controlled
by physical processes. Here, primary production which
reaches the seafloor can be rapidly recycled in a matter of
days to weeks. A large proportion of the North Sea shelf is
of this type.
Developing indicators of connectivity:
Collection of baseline data for the development of
candidate indicators relating to Good Environmental Status
descriptors for food-webs, seabed integrity and biodiversity
is underway within the project and these health indicators
(for example: sediment redox, zooplankton ratios, water
column oxygen) respond to human and climate scenarios,
so can be easily incorporated into future monitoring
programmes. They will be useful in providing improved
insight into ecological functioning and health of shelf sea
regions.
In deeper areas, where the seabed tends to be more
muddy, biological processes are more important in
controlling recycling rates through the sediment which may
take weeks to months. Within the seabed, a number of key
species have been found to drive carbon cycling and we
are now exploring how many species can perform the
same type of ‘function’ and thus if ‘functional redundancy’
exists. Those sites with little functional redundancy (i.e. do
not have many species which can do the same thing) will
be more vulnerable to human activities, so impacts will
need to be carefully managed in these areas.
Effects of trawling and climatic changes:
Trawling can impact the seabed by decreasing benthic
biomass and production, resulting in slower carbon cycling
and increased carbon storage. However, through sediment
resuspension, trawling may also increase the release of
nutrients into the water column.
Changes in the duration and intensity of stratification due
to climate change are likely to have considerable impacts
on marine food webs and carbon cycles. Changes could
include the timing and magnitude of primary production in
different regions and the abundance of planktonic
communities. Models have shown that prolonged
stratification in the North Sea is likely to increase the
incidence of hypoxia (i.e. very low oxygen levels) with
levels reaching <60% oxygen saturation. All of these
impacts will have implications for food-webs and the links
to fisheries production.
Figure 2: Potential impact of bottom trawling on zooplankton production at a
site in the southern North Sea. Zooplankton production is reduced due to the
removal of seabed fauna which recycle nutrients to the water column.
Implications are for reduced ecosystem productivity and reduced drawdown of
atmospheric CO2. This may be moderated by nutrient-release due to
sediment disturbance and re-suspension during trawling.
Where can I find further information about
this and related research?
Cefas are leading this research, and more information
can be found from www.cefas.co.uk/e-conn
Alternatively,
please contact the Marine and Fisheries Science Unit at
Defra, Nobel House, London.
Defra Science – did you know?
At any one time Defra manages over 2000 research projects covering a wide range of topics. For more information on current
research see http://randd.defra.gov.uk and to find out about future research proposals see the Defra Research and Analysis
page at: http://www.defra.gov.uk/evidence/index/htm
ME3205: Marine Ecosystem Connections: Essential indicators of healthy, productive & diverse seas