‘Biosecurity’ is a word that we are unfortunately going to be hearing more of into the future and one we should all give some thought to. Biosecurity does have slightly different meanings if you’re a shellfisher or poultry farmer but here, within these Nature Notes, it’s about trying to manage and prevent invasive and/or non-native species from spreading or being introduced outside their natural range.

view down Tacketwood Creek with worm wart weed dominating the lower shore by the stream
view down Tacketwood Creek with worm wart weed dominating the lower shore by the stream (view down Tacketwood Creek with worm wart weed dominating the lower shore by the stream)

We do try our best to avoid ‘doom and gloom’ stories in nature conservation, trying to give an uplifting angle to give hope and encourage engagement. But with biosecurity, there’s just too much unknown about how bad things might really get! So unfortunately, we have to express the worst case scenario which is not the ideal way to spell out the potential seriousness of not taking some action.

Earlier this year, I spotted an odd growth of seaweed that was sprawled across the entrance of the small Tacketwood Creek just south of Kingsbridge. I’m all too used to seeing a green blanket of a seaweed over the mudflats (proliferating in response to an excess of nitrogenous nutrients flowing in from the estuary’s water catchment) but this was more wiry and a mahogany brown colour. It intrigued me enough to deviate from my task in hand for a closer look and since it wasn’t anything that I recognised I took some detailed photos and permitted myself to take some samples.

I tried very hard to identify what it was, even using a microscope to look at it very closely. In all honesty, I struggled and only narrowed it down to being an ‘elongated, worm-like and cylindrical’ red seaweed. Thankfully, when attending an online saltmarsh restoration conference, someone happened to ask that we all look out for an invasive seaweed that was spreading around our UK’s coast and sounded much like that I’d found. To cut a long-story-short - I alerted colleagues within the Marine Biological Association in Plymouth that study non-native marine species and sought their help – they strongly suspected it to be this invasive seaweed but it took further DNA testing to be absolutely sure. It was confirmed as the worm wart or black wart weed, Gracilaria vermiculophylla.

This worm wart weed is described as being from the northwest Pacific (Japan, China, area) – typical of many of our new invasive arrivals, as the conditions are similar enough for them to survive and sometimes thrive. The worm wart weed is able to tolerate the variable salinity and conditions of shallow estuaries, forming mats which may displace native species such as intertidal seagrasses and cause issues for boating by fouling propellers – not a good picture. I read one positive suggestion that it could help the diversification of habitats for that of local native species but I’m afraid that I think that’s just scrabbling for a positive spin. The worst is that it is also suggested that it can grow and reproduce from unattached fragments, making it all too easy to spread it further unless we all take some care … also, that there is no easy way to eradicate it. Again, an all too common issue with these marine invasive and non-native species.

worm wart weed sprawling across the mudflats - the more olive coloured seaweed is a native wrack seaweed
worm wart weed sprawling across the mudflats - the more olive coloured seaweed is a native wrack seaweed (worm wart weed sprawling across the mudflats - the more olive coloured seaweed is a native wrack seaweed)

So, how did it arrive and what should we do?

It is suggested to have arrived in the UK via ‘oyster cultivation’ but it is not clear if this was direct from the Pacific or via Europe which is maybe more likely? The first UK reported sightings were in 2006. We will never know exactly how it arrived locally but it could just as easily have arrived locally on someone’s wellies, wetsuit, kayak, paddle or crabbing line as from a boat, anchor or trailer – highlighting that we must all take care - marine scientists too.

What we must do, is be mindful of Biosecurity, and do our best to think about checking and leaving all life behind when we move any equipment that could possibly harbour organisms or even just fragments of them when moving between waterbodies. And obviously that goes both ways in preventing their spread out, to bringing them in. We can very rarely manage these marine species once they arrive, so it has to be pretty much all about prevention rather than cure.

The official advice from all authorities, organisations and groups is to Check – Clean – Dry.

Check – look out for pools of water, dark & wet crevices, fragments of plants etc. that could possibly harbour animals, their eggs or even fragments of plants that could just be enough to ‘seed’ a new area. Note, that many intertidal species are particularly hardy and may survive for days, not just hours!

Clean – wash, brush and clean off all kit that could possibly harbour, support and transport life – many feel that this keeps kit in good condition anyway. Note, this should ideally be done near to the water body being left and never on arrival at the new site. Hull washdown facilities are notorious hotspots for introducing new species and every effort should be taken to remove all debris and dispose of it responsibly and away from the water. The hull debris may contain antifouling chemicals too which may help deter non-native species but would be toxic left on the seabed.

Dry – take care to dry everything as much as is possible and realistic – again to just make sure that we are minimising the potential to maintain life that could be transferred from site to site. Note, remembering that many intertidal organisms can survive a degree of dryness, some extra time can help.

Biosecurity is now listed as a serious and major threat to our native biodiversity and invasive species are already having an impact on industry and our own enjoyment of our waters – it’s very much in all our interests. For the South Hams area, there is an Biosecurity plan for each of our estuaries that can either be found on the South Devon National Landscape website or where there is a Harbour Authority, their website too. These individual biosecurity plans list those invasive species already found locally, as well as those to look out for as potential future threats. Just last week, we were warned to look out for the colourful Atlantic blue crab when a live example was found off Brighton.

There are of course, also some new species that are arriving and gradually migrating north through climate change but I see these as at least a semi-natural phenomena that we have to expect. We’d hardly begrudge the arrival of egrets now, would we!