Steve Hawkins
Marine Biological Association, Plymouth

Supporting Evidence

A number of species living on the coastline of the United Kingdom are either warm-water species with their northern limits in the UK or cold-water species with their southern limit in the UK and Northern Europe. These species can, therefore, be used as indicators of climate change by studying their distribution and abundance in response to changes in temperature. Rocky shore species are particularly useful as climate indicators as rocky shores are readily accessible, most species are sedentary or sessile (i.e. do not or cannot move around) and they can be easily sampled in a non-destructive way. There are also numerous long-term datasets available (see table 1), particularly those collected by the Marine Biological Association from the late 1940s onwards. With this in mind the Marine Biodiversity and Climate Change project (MarClim) was instigated in 2001 to undertake broad-scale resurveys around the whole of the UK to compare distributions with those previously recorded. Surveys were continued until the end of the project in 2005 and funding is being sought to continue surveys of climate indicator species in key areas. The final project report (from which most of the information below is taken) was published in 2005 (Mieszkowska et al., 2005).

Table 1. Rocky Shore datasets utilised by the MarClim project (Source: MECN workshop report (Burrows et al., 2006)).

The data shown in table 1 was used to a) develop and test hypotheses on the impact of climatic change on marine biodiversity in Britain and Ireland, and b) forecast future marine community changes on the basis of the Met Office's Hadley Centre climate change models and the United Kingdom Climate Impacts Partnership's climate change scenarios (the broad range of species known or thought likely to be temperature sensitive were covered).

Specifically, the MarClim project investigated the following predictions on the current and future responses of intertidal rocky shore fauna and flora to changes in environmental temperature regimes in Britain:

(1) Northern species will retreat northwards and their abundance will decline; such changes are likely be driven by a reduction in reproductive output and/or decreased juvenile or adult survival during hotter summer periods.

(2) Southern species will expand their range northwards and their abundance will increase. The mechanisms underlying these responses are likely to be an increase in reproductive output and/or juvenile survival during warmer summer periods and milder winters. The extent to which range extensions can occur will also be dependent on length of larval life stages and presence of rocky shores or artificial substrate beyond existing range edges enabling hydrographic barriers to be breached via 'stepping stones'.

(3) Biological interactions including competition, facilitation and predation will modulate the responses of southern and northern species with implications for community structure and ecosystem functioning. For example in barnacles, the northern species (Semibalanus balanoides) is competitively superior and the southern species are released from competition by recruitment failure associated with warm springs.

(4) Changes will be greater than in the last warm period in the 1950s prior to the cold winter of 1962/63.

The period for which ecological information exists spans the relatively warm 1950s, the severe winter of 1962/63 and a cool period from the 1970s to the mid 1980s. Experiments investigating the effects of warming on species reproduction and recruitment of the lusitanian topshells Osilinus (Monodonta) lineatus and Gibbula umbilicalis have been undertaken to investigate the mechanisms influencing these species increase in range and abundance (Mieszkowska et al., 2006). In parallel, models were constructed on interactions between northern and southern indicator species, focussing on barnacles and validated by comparisons with long-term time series. Models were also constructed to predict past and current distributions of indicator species and validated against MarClim archived and contemporary data.

The main findings of the project were:

• Range extensions have occurred at the northern limits of the geographical distributions of typically southern, warm water species Osilinus lineatus (toothed topshell), Gibbula umbilicalis (flat topshell), Chthamalus montagui (Montagu's stellate barnacle), Chthamalus stellatus (Poli's stellate barnacle) and Balanus perforatus (acorn barnacle) since the mid-1980s in Wales, Northern Ireland and Scotland, including greater penetration around the north of Scotland into the colder North Sea.
• Eastward range extensions of the southern species Osilinus lineatus (toothed topshell), Gibbula umbilicalis (flat topshell), Patella ulyssiponensis (china limpet), Patella depressa (black-footed limpet), Melarhaphe neritoides (small periwinkle), Actinia fragacea (strawberry anemone) and Balanus perforatus (acorn barnacle) have also occurred since the mid-1980s into the colder eastern English Channel beyond previous biogeographic boundaries.
• The northern species Alaria esculenta (dabberlocks) and Tectura testudinalis (common tortoiseshell limpet) have shown small retractions in their southern distributional limits and declines in abundance at populations close to these range edges, but the rate of recession is not as fast as the rate of advancement in southern species.
• Synchronous increases in abundance have been recorded in populations of southern topshells throughout Britain and northern France since the mid-1980s. These increases are an order of magnitude greater than the inter-annual variation detected, increasing the confidence that these are observations of decadal-scale change rather than the result of anomalous years, providing support to the theory that these increases in abundance are climate-related. These are driven by better and more consistent recruitment.
• Annual reproductive cycles of the southern/lusitanian trochids are commencing earlier in response to milder winters and warmer springs, coupled with increased survival of newly settled recruits exposed to milder, shorter winters on the shore.
• The annual reproductive cycles of the southern/lusitanian limpet Patella depressa are starting earlier and lasting longer in south-west Britain. In contrast, less than 20% of the population of the northern/boreal limpet, Patella vulgata, reached gonad development stages at which spawning can occur on some shores in south-west Britain in 2004/2005.
• Fluctuations of the northern barnacle Semibalanus balanoides and the southern Chthamalus spp. have been related to climate change using historical data collected by Southward and advanced statistical methods. These show that there is a direct negative effect of warm springs on survival of Semibalanus balanoides which, via release from competition, has an indirect positive effect on Chthamalus. These data have been used for hindcast and forecast modelling using UKCIP climate scenarios. In particular these models have been able to incorporate characteristics such as species mortality, larval supply and competitive interactions to create more biologically realistic predictions of species responses to climate change.
• Models using the extensive broadscale resurvey data have been created for all MarClim indicator species to predict changes in their abundance and distribution in response to wave action and sea surface temperature regimes forecast by UKCIP (MarClim undated b).

Surveys of the distribution of a number of species were carried out after the recent cold winter of 2005/06 (the coldest since 1995/96 for England and Wales, since 2000/01 for Scotland and Northern Ireland) as part of a NERC urgency grant. It was found that the range extensions previously observed were not trimmed back by this event, with the possible exception of reduced abundance of Anemonia viridis.  

It is important to note that many of the exact mechanisms by which species respond to climate are still under investigation (Mieszkowska et al., 2006) although an initial assessment by the MarClim project is that (Mieszkowska et al., 2005):

• It is likely that the northward range extensions observed in North Wales and those along the north coast of Scotland down into the North Sea have occurred in response to climatic warming increasing reproductive effort and juvenile survival success allowing these species to establish on suitable habitats.
• The increased abundance of some southern species, such as trochids, limpets and barnacles, is likely to have been the result of the earlier commencement (and in some cases prolongment) of annual reproductive cycles in response to warmer springs, coupled with increased survival of newly settled recruits exposed to milder, shorter winters on the shore. These species may also be out-competing northern equivalents as climatic conditions become more suitable for their survival and less suitable for species with cold water affinities.

There are also other factors identified by MarClim which may also have an influence on species range extensions:

• It is likely that range extensions along the eastern English Channel have occurred due to a combination of the proliferation of artificial sea defences along this coast, providing suitable habitat where none was previously present, and greater recruitment success of southern species in response to climatic warming. Hydrographic barriers at Portland Bill, the Isle of Wight and Selsey Bill seem to have been breached.

This is potentially an important additional factor contributing to the spread of certain species and will require further investigation.

Please acknowledge this document as: Hawkins, S. (2006). Impacts of Climate Change on Intertidal Species in Marine Climate Change Impacts Annual Report Card 2006 (Eds. Buckley, P.J, Dye, S.R. and Baxter, J.M), Online Summary Reports, MCCIP, Lowestoft, www.mccip.org.uk

References

Burrows, M.T., Hawkins, S.J., Southward, A.J., Kendall, M.A., Thompson, R.C. & O'Riordan, R. (2006). Rocky Shore datasets - Marine Biodiversity and Climate Change Project (Marclim) in: Frost, M. T, Jefferson, R. & Hawkins, S. J. (Editors). (2006).The evaluation of time series: their scientific value and contribution to policy needs. Report prepared by the Marine Environmental Change Network (MECN) for the Department for Environment, Food and Rural Affairs (DEFRA). Marine Biological Association, Plymouth. Contract CDEP 84/5/311. Marine Biological Association of the United Kingdom Occasional Publications No. 22.

MarClim (undated a). Marine Biodiversity and Climate Change. Publications. Available at http://www.mba.ac.uk/marclim/marclim.php?sec=pub. Last accessed 31 August 2006.

MarClim (undated b). Marine Biodiversity and Climate Change. About MarClim. Available at http://www.mba.ac.uk/marclim/. Last accessed 31 August 2006.

Mieszkowska, N., Leaper, R., Moore, P., Kendall, M. A., Burrows, M. T., Lear, D., Poloczanska, E., Hiscock, K., Moschella, P. S., Thompson, R. C., Herbert, R. J., Laffoley, D., Baxter, J., Southward, A. J. & Hawkins, S. J. (2005) Marine Biodiversity and Climate Change Assessing and Predicting the Influence of Climatic Change Using Intertidal Rocky Shore Biota. Final Report for United Kingdom Funders. Marine Biological Association Occasional Publications No. 20.

Mieszkowska, N., Kendall, M. A., Hawkins, S. J., Leaper, R., Williamson, P., Hardman-Mountford, N. J. & Southward, A. J. (2006). Changes in the range of some common rocky shore species in Britain - a response to climate change? Hydrobiologia. 555: 241-251.

MECN (2006). Marine Environmental Change Network. Available at http://www.mba.ac.uk/MECN/. Last accessed 31 August 2006.

Met Office (2006). News Release: Winter Weather Summary. Available at http://www.metoffice.com/corporate/pressoffice/2006/pr20060303b.html. Last accessed 31 August 2006.

Other Information sources

Helmuth, B., Mieszkowska, N., Moore, P. &  Hawkins, S. (2006). Living on the Edge of Two Changing Worlds: Forecasting the Responses to Climate Change of Rocky Intertidal Ecosystems. Annual Review of Ecology, Evolution, & Systematics 37.

Herbert, R.J.H., Hawkins, S.J., Sheader, M. & Southward, A.J. (2003). Range extension and reproduction of the barnacle Balanus perforatus in the eastern English Channel. Journal of the Marine Biological Association of the UK. 83: 73-82.

Hiscock, K., Southward, A. J., Tittley, I. & Hawkins, S. J. (2004). Effect of changing temperature on benthic marine life in Britain and Ireland.  Aquatic Conservation: Marine and Freshwater Ecosystems. 14: 333-362.

Southward, A .J., Langmead, O., Hardman-Mountford, N. J., Aiken, J., Boalch, G. T., Dando, P. R., Genner, M. J., Joint, I., Kendall, M. A., Halliday, N. C., Harris, R. P., Leaper, R., Mieszkowska, N., Pingree, R. D., Richardson, A. J., Sims, D. W., Smith, T., Walne, A. W. & Hawkins, S. J. (2005). Long-term oceanographic and ecological research in the western English Channel. Advances in Marine Biology. 47: 1-105.