SCUBA Sampling of Sea pens in Scotland

Chris Yesson

I began my field trip to Scotland by breathlessly running for the sleeper train at Euston, having forgotten the departure time. Our trip ended with Kirsty Kemp and I running for the train in Inverness. In between we had a great time diving in sea lochs, chasing rainbows and enjoying the views of the highlands. The trip was to collect samples of the tall sea pen, Funiculina quadrangularis, from the west coast of Scotland, and was funded by the PADI foundation. 

Sea pens are named from their resemblance to old fashioned quill pens. They are found anchoring in muddy sea beds, where they filter feed. Funiculina is a habitat forming species that can be home to commercially important fish. Unfortunately, Funiculina is vulnerable to anthropogenic impacts, particularly from bottom-contacting fishing gear. We have seen dramatic declines of this species particularly in the Mediterranean. In the UK, it is found off the west coast of Scotland, including at accessible depths of 20-35 metres, which is why we (myself Kirsty Kemp and professional diver George Brown) spent five days diving, starting on the Isle of Mull, finishing 260km north in Ullapool.

Dive Survey in Scotland
Kirsty Kemp and George Brown diving in Loch Broom, near Ullapool. Credit: Chris Yesson

Things didn't go according to plan. We found no seapens on the first two dives. Our plan was guided by surveys from the national biodiversity network, but it turns out that things have changed a bit since the earlier observations were made. On the first night we made a hasty reworking of our plan, drawing on George's local knowledge and focussing on recent observations from 'dependable' observers.

Things turned around when we had the good omen of sailing through a perfect rainbow on the ferry. Our third dive, by the ferry terminal in Loch Aline, met with great success, and we found a large number of fully mature Funiculina well over one metre tall. This was a great dive as we saw the other two shallow British sea pens, Virgularia mirabilis and Pennatula phosphorea at the same time. It is very unusual to see all three sea pens at such a shallow location (~25m).

Not all populations of Funiculina were so healthy. On our dive in Loch Sunart we found a lot of specimens, but none were taller than around 20cm.  We later learned that this site has been dredged recently, which would explain the lack of mature specimens, and the impact this has on populations. However, the silver lining is that the large number of juveniles is a sign of recovery.

Sampling sea pens while diving is a tricky business. We had scissors and plastic bags with us to snip and store small sections off the tips of sea pen colonies. Opening plastic bags wearing diving gloves in torch light while hovering over mud that readily plumes into a sediment cloud is no mean feat. Even when you get the sample in the bag you have to avoid sucking all your samples out when you pull out your hand. Fortunately our pro-diver George was such an expert he made up for my fumbling.

Sampling Seapens in Scotland
George Brown shows his skill in sampling the tip of a 1m sea pen. Credit: Kirsty Kemp

You meet some amazing people working at IoZ and George Brown is a great example. He's been diving for the Highland council for 30+ years and kept us entertained with diving stories including discovering a naval submarine sunk during WWII. Also it is interesting to hear first-hand reports of the extent and severity of the Beggiatoa bacterial mats that form underneath fish farms.

This trip was limited to shore dives, and finding good access to sites was difficult. Our final site in Little Loch Broom took the prize, when we had to hike through 200 metres of bracken, down and (and then up) a steep hill in full dive gear. Thankfully this was worth the effort as we came away with some good samples.

Hiking in dive gear
Hiking up a hill in full gear was worth it to dive in Little Loch Broom.

Our collections will be used in an investigation of the population genetic structure of these vulnerable species. Meesha Patel, a master's student from UCL, has just begun working in the lab to extract DNA and genotype our samples, and we eagerly await her results.



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