Wrecks on the Seabed: Ecology

As part of two major projects: the ALSF funded Wrecks on the Seabed project and the contract to implement the Protection of Wrecks Act (PWA) for English Heritage (now Historic England), Wessex Archaeology’s dive team has surveyed more than 65 shipwreck sites around the coast of the United Kingdom.

These diving surveys have generated a substantial body of information about each site and as we have processed this information it has become increasingly clear that the relationships between wrecks and the plants and animals that inhabit them is a neglected area of study and one that needs closer scrutiny.

The contexts of these two projects - the mitigation strategies generally adopted for wrecks within aggregate extraction areas in the case of Wrecks on the Seabed, and the conservation and management of protected sites in the case of the PWA – have thrown up a number of questions about the relationships between wrecks and their flora and fauna.

For example, do historical wrecks have nature conservation value in terms of the species they attract or the habitats they provide? Where wrecks are surrounded by exclusions zones – such as in aggregate extraction areas – do they act as refuges for species, or habitats from which the re-colonisation of adjacent areas of the seabed can take place after aggregate dredging? Can the presence of species or character of habitats be used as a proxy for gauging wreck site condition and stability? And is there any scope for, or value in, integrating archaeological and ecological surveys of wreck sites?

With these questions in mind we approached Dr. Kate Cole (East Sussex County Council – Coastal Biodiversity Officer/Sussex Seasearch Co-ordinator) and Dr. Gerald Legg (Brighton and Hove Council – Marine Biologist, Booth Museum). We showed them some of the photographic data we’d collected, and asked them whether such information, gathered during archaeological site assessments, would be useful to them as ecologists. And if so, what might be done to incorporate ecological and biological recording into archaeological survey work?

Their response was that this data was useful for biological and ecological purposes and could, for example provide evidence of key indicator species that are ‘moving’ as a result of climate change or are otherwise significant.

From an archaeological perspective these discussions suggested that this information can be used to more accurately describe the biological condition of wrecks, including the variability across wreck sites, by studying the environmental processes at play, as indicated by different species.

Project background

During 2007 we developed these ideas into a proposal to the ALSF for an extension of the Wrecks on the Seabed project. Funding was granted and the project got underway in November 2007.

Objectives

Two of the sites chosen for the project were investigated during Wrecks on the Seabed - the Portland Stone Wreck and Bottle Wreck. Available data for three sites in East Sussex designated as Marine Sites of Nature Conservation Interest (MSNCI) and surveyed by Sussex Seasearch – the HMS Northcoates, the City of Waterford, and the Outer Mulberry – will be also be reviewed.

Claire Dalgleish, a freelance marine ecologist has joined Wessex Archaeology for the duration of the project, and is exploring the questions posed above. Her starting point is a literature review looking for any other work on the links between the archaeology and ecology of historic wreck sites. She will then examine digital photographs of the sites, some of the many hours of footage recorded on the helmet-mounted video cameras carried by our divers during their surveys on the sites chosen for the project, as well as diver observations and site descriptions.

The results of these assessments will be the development of a draft methodology for recording flora and fauna on wrecks as part of archaeological site survey, compatible with Seasearch, Marlin and DASSH standards.

The sites chosen for this project lie at a range of water depths and include steel and wooden wrecks. They are thus likely to play host to a range of ecological communities. We anticipate that the range of chosen sites will allow an assessment of ecological variability across different wreck types at different water depths. The environmental processes indicated by the presence of different species may then be used as potential indicators of relative site vulnerability to change or stability.

• To assess the potential of archaeological data collected from a number of wrecks off the East Sussex coast to provide useful ecological and biological information;

• To assess the value – to archaeologists, ecologists and seabed developers - of integrating archaeological and ecological surveys of wreck sites in future; and

• To propose a cost-effective, but ecologically sound methodology for recording the flora and fauna on wrecks during archaeological site survey, based on diver observations and/or stills images and video footage.

Outcomes

We believe that this project is relevant to the marine aggregates industry in that it will:

• demonstrate the cost benefits of integrating archaeological and ecological surveys of sites in aggregate extraction areas;

• increase understanding by archaeologists of environmental interactions and processes on wreck sites, which could, for example, improve our understanding and prediction of the cumulative effects of seabed development on wreck sites;

• suggest possible cross-over advantages from the respective mitigation measures used by each discipline.

From an archaeological perspective, if the project suggests that the data is useful to both archaeology and ecology, this will open new doors with respect to better understanding site formation processes and the implications this has for managing wreck sites. It will also build important inter-disciplinary links between archaeologists and ecologists, and may point the way to closer interactions in future.

At a general level, this project seeks to promote an awareness of the wider, in this case ecological, importance of the marine historic environment. We hope that this work will add a new dimension – for the public and marine professionals alike – to the study of our historical shipwrecks. Ultimately, it is hoped that the results of the project will benefit strategies for the conservation of our marine resources – both historical and natural.