Long term change

Pete Rendle and Stuart Jenkins sampling in the English Channel on board the RV Prince MadogOne of the most powerful approaches to understanding man's impact on marine ecosystems is to examine change at the population and community level over appropriate time scales.  In terms of many of the most pervasive anthropogenic impacts in the marine environment  (fishing pressure, climate change, eutrophication), this means analysing time series over multi-decadal scales.  Working with my colleague Dr Hilmar Hinz I have developed interests in how coastal soft sediment infaunal and epifaunal communities have changed over the last 50-100 years.  There are very few benthic time series with which to work; hence we have focused on high quality historical surveys conducted prior to the huge increase in fishing pressure we have seen over the past 50 years and the recent (past 3 decades) rapid warming. 

 The work of Norman Holme

Norman Holme, a staff member at the Marine Biological Association in Plymouth, UK developed an extensive body of work investigating the benthic ecology of the English Channel.  He left an invaluable record of the marine benthos of this area over the period 1949 to 1980.  We have utilised some of his work to attempt to understand both changes in distribution of soft sediment biota and changes in community compostion over a 50+ year time scale.  Repeating a portion of his Channel wide survey of 1958/59 on board Bangor University's Prince Madog  in 2006 we showed that although there were some notable changes in distribution of benthic organsims, the magnitude of change was much lower than in some other components of the Channel ecosystem (interdial biota, fish, plankton) (Hinz et al 2011).   

The Eddystone Reef

Conservation agencies have a difficult task when selecting areas of the seabed to protect.  A laudable aim is to apply protection from mans' activites (in many cases demersal fishing activities) in order that communities revert to those which bear some resemblance to communities prior to the implementation of industrialised levels of fishing.  One question which is asked is: 'But what did the seabed used to look like and is it very different to that which we see today?'.   Funded by Natural England, our student Evelina Capasso compared the present state of benthic community of gravel beds around the Eddystone Reef off the SW coast of England with the position over one hundred years ago (see Allen 1895). 

Changes were clearly evident as expressed in Evelina's paper (Capasso et al 2010): Echinoderm diversity showed a clear reduction between 1895 and 2007. The sea urchins Echinus esculentus, Spatangus purpureus, and Psammechinus miliaris and large star-fish Marthasterias glacialis showed reductions in abundance,in some cases being entirely absent from the survey area in 2007. Polychaetes showed a shift from tubiculous species to small errant and predatory species such as Glycera, Nephtys, and Lumbrineris spp. Within the group Mollusca large species such as Pecten maximus and Laevicardium crassum decreased in abundance while small species increased.

A benthic time series in North Wales

In 2008 we re-established a benthic time series in North Wales by building on the work of Dr Ivor Rees who, with School of Ocean Sciences Masters students, had consistently sampled the infauna of Red Wharf Bay on the north coast of Anglesey over a period of 20 years.  This area has not been subject to intensive fishing and thus provides the opportunity to examine relatively natural inter-annual variation in benthic assemblage composition over recent decades.  Understanding of natural cycles of change provides an important context with which to view a range of anthropogenic impacts. 

Work supported by:

English Nature: Aggregates Levy Sustainability Fund £108,759 Jenkins SR and Frost MAn environmental context to the effects of marine aggregate dredging January 2006 

Defra £10,000  Jenkins SR, Hinz H, Cappasso E Frost M, Long term change in benthic fauna off Plymouth: utilizing historic records and establishing a long term time series. March 2007 

Natural England £12,000 Jenkins SR, Hinz H, Cappasso E Frost M  Establishing the extent of change in gravel communities at the Eddystone Reef: a potential offshore Special Area of Conservation. March 2007 

Defra £10,000 Jenkins SRand Hinz H, Establishing a benthic time series in North Wales: linking the old with the new.  October 2008

Defra:  Through the Marine Environmental Change Network

Countryside Council for Wales:  Establishing a benthic time series in North Wales