Iceland the land of fire and ice, and core samples
Posted on: 28/09/2021 By: Paul Butler
Sample collection and processing in SEACHANGE was inevitably delayed because of the COVID pandemic, but thanks to the early inclusion of Iceland on the UK’s green list of relatively easily visited countries, Jake Scolding, James Scourse and Paul Butler were able to visit in late June/early July.
The SEACHANGE North Atlantic cruise was delayed until summer of 2022, but it turned out that two cores were available which had been collected on the North Icelandic Shelf during an earlier project (EU FP7 project “MILLENNIUM”) in 2006. These cores had been kept in controlled conditions in a cold store at University of Iceland since collection and had not been opened or processed in any way. In the absence of fresh core material for eDNA analysis at University of Copenhagen, this presented a great opportunity to get some material to them so they could start their analysis, with the additional benefit of finding out to what extent eDNA from a fully marine environment would degrade during 15 years in storage.
James measures the split core and checks it against colour chart
Upon arriving in Iceland, we were immediately tested for COVID, and were required to quarantine in our hotel for a few hours while we waited for the test results. These didn’t take long, we were all negative (phew!) and were keen to start work early the next day. Our colleague at University of Iceland, Esther Ruth Guðmundsdóttir, was a fantastic help retrieving the cores from the cold store and then setting up our work space. The cores had been untouched since they were collected in 2006. We split them using a core splitter and James gave them an initial assessment for condition. Our analysis of core lengths and local sedimentation rates suggested that the two cores go back approximately 1,000 years and 3,000 years respectively, potentially giving good coverage of the time periods of interest for SEACHANGE.
The following two days were spent sampling for eDNA. Taking samples for DNA analysis requires a pristine uncontaminated environment, all surfaces covered, full protective covering, and cleaning or replacement of the sampling tools between each sample. Luke and Emilia from Copenhagen had sent an instruction video showing the process, and we also set up a video link at one point so they could check that we were doing things right. James used a fresh scalpel for each sample, first scraping off a small layer of sediment from the exposed surface of the split core to remove any contamination that might have happened during the process of splitting. Using 5 ml syringes with the ends cut off (almost like a tiny coring device), James carefully extracted sediment, always from the centre of the exposed surface to minimize edge contamination. These samples were then placed in sterile centrifuge tubes and labelled. All the samples were stored on site at 4oC while Luke and Emilia arranged shipment to Copenhagen.
The two days of sampling were intensive, with the bulky PPE making conditions very hot and uncomfortable. This kind of kit is unusual in a geology department and we sometimes wondered if people passing by and looking in might have thought we were working on some new strain of COVID. Anyway, after finishing lab work on the final day of sampling, we managed to find time to explore Reykjavik and then found a nice Irish bar where we watched England’s famous win over Germany in the Euros.
After the core sampling, Jake returned home while James and Paul set out in a hire car to visit some of the proposed SEACHANGE midden sites in north Iceland. Our guide was Ramona Harrison, who is the SEACHANGE partner for these sites, which cover the period from the Settlement to around the 14th century, with two more sites providing midden materials also until the early modern period (Möðruvellir and Staðartunga. The latter will be site of larger scale excavation in summer 2022). While Skuggi, Oddstaðir and Möðruvellir are sites not currently in a state where they can be sampled, having been excavated and re-covered, this was an opportunity to better understand living conditions during the first 500 years following Icelandic Settlement, with a better idea of past structures of agriculture, trade and religion. We are hoping to find marine artefacts – bones of fish and marine mammals, and also shells, possibly including shells of the flagship long-lived species.
While the Kóngsstadir site produced very sparse and poorly preserved midden materials, the midden chronology indicates early site occupation and a possible 14th century abandonment, with what looks to be an episode of postmedieval reoccupation. The volcanic tephra layers identified there were the same ones encountered at the Skuggi midden in Hörgárdalur, which means there is good chronological overlap in these diachronic period divisions across the entire research area.
