Evaluation of Polycyclic Aromatic Hydrocarbon Pollution From the HMS Royal Oak Shipwreck and Effects on Sediment Microbial Community Structure

Gareth E Thomas,Jan L Brant,Clare Hynes,Terry J Mcgenity,Stefan G Bolam,Boyd A Mckew,Rodney Brash,Paul S O Mcilwaine,Freya Goodsir

doi:10.3389/fmars.2021.650139

Abstract

Despite many shipwrecks containing oil there is a paucity of studies investigating their impact on surrounding environments. This study evaluates any potential effect the World War II shipwreck HMS Royal Oak is having on surrounding benthic sediments in Scapa Flow, Scotland. HMS (Her Majesty’s Ship) Royal Oak sank in 1939, subsequently leaked oil in the 1960s and 1990s, and is estimated to still hold 697 tonnes of fuel oil. In this study, sediments were analysed, over a 17.5 cm depth profile, along a 50–950 m cruciform transect away from the shipwreck. Analysis of polycyclic aromatic hydrocarbons (PAHs) revealed low concentrations (205.91 ± 50.15 μg kg–1 of dry sediment), which did not significantly differ with either distance from the shipwreck or sediment depth. PAH concentrations were well below the effects-range low (ERL) for the OSPAR (Oslo/Paris convention for the Protection of the Marine Environment of the North-East Atlantic) maritime area. The average Pyrogenic Index, in sediments around HMS Royal Oak, was 1.06 (±0.34), indicating PAHs were pyrogenic rather than petrogenic. Moreover, analysis of sediment microbiomes revealed no significant differences in bacterial community structure with distance from the shipwreck, with extremely low levels of obligate hydrocarbonoclastic bacteria (OHCB; 0.21% ± 0.54%). Both lines of evidence suggest that sampled sediments are not currently being impacted by petrogenic hydrocarbons and show no long-term impact by previous oil-spills from HMS Royal Oak.

Highlights

In the last two decades, the focus on evaluating the environmental impact from shipwrecks has significantly increased (Landquist et al, 2013), especially those from the two World Wars, which constitute >8,600 shipwrecks in the world’s seas (Monfils et al, 2006)
This study evaluates historic impact of oil contamination from the shipwreck HMS Royal Oak on the surrounding benthic microbial communities
The objective of this study was to determine whether fuel oil from HMS Royal Oak displays elevated concentrations in surrounding benthic sediments, by determining both the concentration and source of sediment polycyclic aromatic hydrocarbons (PAHs) over a 950 m radius of the shipwreck

Summary

Introduction

In the last two decades, the focus on evaluating the environmental impact from shipwrecks has significantly increased (Landquist et al, 2013), especially those from the two World Wars, which constitute >8,600 shipwrecks in the world’s seas (Monfils et al, 2006). Crude oil and its petroleum derivatives can have toxic effects, especially oils with higher proportions of volatile organic compounds (VOCs) and polycyclic aromatic hydrocarbons (PAHs) (IARC, 1987; National Toxicology Program, 2011; Manzetti, 2013). On the 14th October 1939, 6 weeks after the start of World War II, the British battleship HMS (Her Majesty’s Ship) Royal Oak was torpedoed by a German submarine and sank to the bottom of Scapa Flow (Orkney Islands, Scotland; Figure 1). As many lives were lost, HMS Royal Oak is protected under the Protection of Military Remains Act 1986. HMS Royal Oak sank with approximately 3,000 tonnes of fuel oil on board. Whilst any visible oil leakage from HMS Royal Oak in Scapa Flow has subsided, it is unknown whether there is a legacy of hydrocarbon contamination in the sediments

Objectives

Methods

Results