Link discovered between extreme weather
event and marine ecological change
10th February 2009
Plymouth scientists have discovered evidence of a direct link
between extreme weather events associated with climate change and
episodic changes to the ecological conditions and processes of the
marine environment of the Western English Channel. These
modifications could have significant implications on how our
coastal seas function in the future and ultimately, on the goods
and services provided by the oceans.
The research, undertaken by PML, the University of Plymouth and
supported by the Environment Agency and the Western Channel
Observatory, has demonstrated that heavy summertime rainfall over
the south-west of England caused a modification in the behaviour of
the phytoplankton populations which form the base of the marine
food web.
The summer of 2007 saw the heaviest summertime rainfall since
records began in 1914 which caused increased land “run-off” into
the river systems. This “run-off” is heavily enriched in nitrogen
nutrients which has the result of fertilising phytoplankton
activity in coastal areas. Under normal conditions, much of the
river-borne nutrient load is diluted or removed by biological
activity whilst still in estuaries. However after extreme rainfall
conditions, freshwater and nutrients were flushed away from the
coast and were detected 10 miles offshore at one of PML's
sampling stations. This had the effect of raising inorganic
nitrogen concentrations by more than 5 times the summertime average
but without a similar increase in inorganic phosphorus which
created an unbalanced nutrient supply for the phytoplankton.
To combat this imbalance and the lack of available inorganic
phosphorus, some species reacted by liberating phosphorus
from organic compounds, an option only available to a limited
number of algal groups as it is a far more biologically expensive
process. This changed the function of existing populations and
favoured those that could afford the more energy-consuming routes
to obtain their phosphorus. This raises many questions about future
marine resources under the conditions of increased extreme weather
events that are forecast, specifically with respect to the
occurrence of nuisance algal species and the threats they may pose
to fisheries, aquaculture and human health.
Dr Andy Rees, lead author and Biogeochemist at PML, commented:
“Our research has shown positive evidence of extreme rainfall
having an ecological effect on the marine organisms in our local
coastal waters, off Plymouth. With climate change scientists
predicting an increase in extreme weather events, we could well
experience an increase in the frequency and duration of these
effects, which could change the way in which our coastal seas
function.”
PML plans to continue this work by extending the field research
to the NW African coast and Atlantic Ocean during research cruises
scheduled for later this year.