Monday 24 March 2014

Time to get muddy in Fladen

With the MCZ element of the survey under our belts, the third and final leg of our survey took us up North to the Fladen Grounds, an extensive area of muddy seabed. This part of the survey is to assess the ecology of muddy communities, particularly the tall sea pen (Funiculina quadrangularis), and burrowing in-fauna (such as the langoustine Nephrops norvegicus). We've switched from a Hamon grab to a Day grab which now allows us preserve the layering of the sample so we can collect the top 2 cm for analysis of its organic and inorganic make-up.

Day grab in action (Neil Golding/JNCC)
Once the weather had cleared up, we were able to start sampling again. The sample strategy for the Fladen part of the survey is more intense both in terms of time and data collected. While 2 grabs are taken per station, a sledge camera transect is also taken in the same area.

Camera sledge deployment (Neil Golding/JNCC)
The grab samples have mostly been mud-dominated to start of with, the most common species making an appearance being the burrowing sea potato (Echinocardium cordatum), the white sea urchin (Echinus acutus), the slender sea pen (Virgularia mirabilis), the phosphorescent sea pen (Pennatula phosphorea), anemones (mostly Bolocera) and plenty of worms, which of course all have to be “tweezered” out of the 1 mm mesh sieve – an arduous and time-consuming task with numb fingers.

Virgularia mirabilis and Pennatula phosphorea (JNCC/Cefas)

The tall seapen (Funiculina quadrangularis) is a feature of interest in the Fladen area. A rarer find in the offshore environment than on the sheltered west coast of Scotland, it’s associated with burrowed mud habitat and can grow up to 2 m tall. After only a few decent sledge camera transects, we have so far seen lots of Virgularia mirabilis (above) and Pennnatula phoshorea (above and below) but Funiculina remains to be seen.

Pennatula phosphorea and the hermit crab Pagurus sp. (JNCC/Cefas)

Burrowing megafauna is a feature of interest in this area given the nature of the seabed habitat. While Nephrops norvegicus has been observed on the video tows, they have been too quick to take stills of yet. Below is the largest North sea anemone, Bolocera tuediae, whose tentacles provide shelter to various crustacean species; below could be the friendly blade shrimp Spirontocaris llijeborgii.

Bolocera tuediae surrounded by what could be Spirontocaris llijeborgii. (JNCC/Cefas)
Bed of Echinus acutus. (JNCC/Cefas)