For a selection of the project's taxonomic groups we study fundamental proxies for the intensity of resource extraction and human impacts on marine life: changes in animal size (see GMM), plus changes in trophic level (as inferred by bulk and compound specific stable isotope analysis), and ancient DNA (aDNA) evidence for fisheries-induced evolution and changes in effective population size.

Ancient DNA

Ancient  DNA (whole genome sequencing) data are being used in a variety of ways: 1) We use chromosome resolved assemblies and whole genome sequence data to unambiguously identify genetic sex and confirm species of specimens. This type of analysis can be performed on specimens with extremely low DNA preservation. 2) Specimens with the best preservation are sequenced deeper in order to create spatially resolved genomic reference datasets of a number of individuals with known origin. We then use these reference data, in combination with published data from important research by other teams, to assign archaeological and historical individuals in our larger dataset (e.g. cured fish or trade goods of walrus ivory) to these spatially explicit groups, even when there is low-coverage sequence data. 3) Finally, we reconstruct estimates of past effective population sizes using a variety of approaches, for those specimens with sufficient aDNA preservation.  The 4-OCEANS aDNA research is led by Prof. Bastiaan Star of the UNiversity of Oslo.

Stable Isotope Analysis

A fundamental measure of extraction pressure on fish and sea mammals is a decrease in the trophic level of animals exploited, due to early extraction of the largest individuals of both species of interest and its prey. This can be evaluated by taxon and animal size based on zooarchaeological data (See Systematic Review and GMM), but is measurable far more directly using stable isotope analysis of the protein from museum and archaeological specimens of fish and sea mammal bone. There are two main approaches to using stable isotope analysis for the determination of trophic level: bulk and compound specific. Both are employed by 4-OCEANS. We first measure bulk δ15N ratios on samples of defatted bone collagen (all assessed for preservation). Collagen δ15N reflects both baseline values in the ecosystem and trophic level. This easily derived value is an excellent guides to trophic level within a given ecosystem. However, it must be augmented by either extensive analyses of baseline control samples (problematic using archaeological material across wide ranges of time and space) or by compound specific stable isotope analysis in order to compare information on trophic level between ecosystems and across time periods characterised by major environmental change. Crucially, we thus supplement bulk collagen isotope data with δ15N and δ13C measurements of single amino acids using compound-specific isotopic analysis (CSIA). Concurrent with bulk δ15N analysis, we measure bulk collagen δ13C and δ34S values to further refine our understanding of changes in the marine environment, and to help identify fish and sea mammal remains that represent imports from distant ecosystems; δ13C is influenced by environment and diet and δ34S is an indirect proxy for salinity. The 4-OCEANS stable isotope research is led by Dr. Erin Kunisch, Dr. Danny Buss, Dr. Katrien Dierickx and Dr. Mohsen Falahati-Anbaran, with key support from Eirik Sollid and our colleagues at the National Laboratory for Age Determination.