A Sea Of Change, Winter 2006

A sea of change The seas are not only rising, their temperature is increasing thanks to climate change. But what effect will this have on the creatures that live around the UK coasts? Pippa Moore and her colleagues at the Marine Biological Association take a plunge into the Big Blue.

I

t is widely accepted that the planet is experiencing a period of rapid climate change, primarily driven by human activities. Sea

surface temperatures (SST) around the British coastline have increased. In fact, data for the English Channel show a 1 C rise in SST since 1990, greater than any other change recorded over the past 100 years (Hawkins et al 2003). Because of this, climate change impacts on our marine biodiversity are of strategic concern to the scientific community, government, NGOs and the general public. 0

The British Isles, particularly southwest Britain, are ideally situated for investigating the effects of climate change as they straddle two major marine biogeographic zones. This

results in both warm (lusitanian) and cool (boreal) species co-existing, living at the northern or southern edge of their biogeographic ranges. These species have been shown to respond to previous natural climate shifts and as such are expected to respond to the current rapid climate changes affecting our seas.

Effects of global change on plankton and fish Early work carried out by researchers at the Marine Biological Association of the UK (MBA), for example, linked fluctuations in the abundance of coldwater planktonic herring larvae and warm-water pilchard eggs with fluctuations in climatic conditions (Southward 1980). More recently a northward shift of 10˚ latitude in the distribution of southern species of

copepod in the eastern Atlantic has been found (Beaugrand et al. 2002). These species shifts could potentially impacts on fish have large communities as there will be a mismatch in plankton availability at the time of the year when food is needed. In the English Channel, work on both commercial and non-commercial fish populations found that changes in mean annual sea surface temperature (SST) accounted for the greatest variation (24 per cent) in fish community structure. Fishing pressure also accounted for changes in the commercial part of the population (Genner et al 2004). Declines have been seen in the abundance of larger commercial species, such as skates, rays and brill. Large increases have also been noted in smaller trash species (commercially caught fish not for human consumption), such as poor cod, red band-fish and dragonets. Such shifts in fish species ranges have also been observed in the North Sea (Perry et al 2005). There have also been changes in species migration and spawning times in the English Channel (Sims et al 2001, 2004).

Intertidal indicators of climate change

Winner – Strawberry anemone

12

The edge Winter 2006

As the most readily accessible marine habitat in Europe, rocky shores have been the focus of formal recording of species distributions since the first half

1963

© MBA

2001 The change in fish sizes caught between the 1960s and now is clearly evident in these MBA trawl photos taken in: left, Oct 1963; right, Nov 2001.

of the 20th Century. Rocky shores are easily surveyed and can provide cheap indicators of changes offshore. The Marine Biodiversity and Climate Change (MarClim) project has recently analysed historic data sets from the 1950s-1980s and contemporary data on intertidal indicator species abundances, distributions and population structure. The project has observed eastern and northern range extensions of many intertidal species with southern biogeographic distributions including: limpets, topshells, barnacles and algae. In many cases the extension of species ranges in the eastern English Channel has been assisted by sea defences which act as stepping stones for species expansion to areas where previously suitable hard substrata has not been present (Herbert et al 2003).

Sea defences are likely to increase over the next few years, providing more habitat for species range expansion. More can be found out about the rocky shore survey work at www.mba.ac.uk/marclim Already some species are being recorded as ‘winners’ or ‘losers’. ‘Winners’ include the strawberry anemone Actinia fragacea and the topshell Gibbula umbilicalis which have both been recorded further north and east in recent years. In contrast, dabberlocks seaweed Alaria esculenta and the common tortoiseshell limpet Tectura testudinalis have both been classed as ‘losers’ as their ranges are contracting in the British Isles. Although it is not clear how all species will respond to climate change or the speed that they will respond, what is clear is that species ranges will change and change independently of each other. Different species mixtures will occur resulting in large impacts on the structure and function of marine communities. Efforts are now being made to understand the mechanisms behind species responses to climate change to inform predictive models to forecast future species ranges and community structure.

Getting involved The Marine Life Information Network (MarLIN), in conjunction with other agencies has been at the forefront of coordinating a volunteer marine recording network. Volunteer recorders are given a variety of resources including marine life recording schemes and identification guides which focus on conspicuous and easily identifiable species, many of which are sensitive to climate change. Findings are reported via the MarLIN website where the information is verified, validated, entered into a database and made available to all. To find out more about getting involved, see the MarLIN website: www.marlin.ac.uk/LearningZone. It is hoped that this sort of inititative will strengthen links between research and education as well as contributing to baseline data by providing wide geographical and temporal coverage, tapping into local knowledge and picking up rare occurrences of species.

Marine Biological Association: www.mba.ac.uk Tel 01752 633207

K. Telnes

Authors: Pippa Moore, Post doctoral research assistant on the MarClim project - Steve Hawkins, Director of MBA - Keith Hiscock,

Loser – common tortoiseshell limpet

Programme Director, MarLIN - Alan Southward, Associate research fellow, MBA

The edge Winter 2006

13