Periodic Reporting for period 3 - SEACHANGE (Quantifying the impact of major cultural transitions on marine ecosystem functioning and biodiversity)
Période du rapport: 2023-10-01 au 2025-03-31
Marine conservation seeks to protect valuable habitats but the pristine state of marine ecosystem functioning and biodiversity is conjectural. Conservation management strategies are often based on highly altered ecosystems where the degree of human-induced change is unknown. In SEACHANGE, we propose a structured approach to the reconstruction of marine ecosystem baselines in order to quantify the impact of human cultural transitions on marine biodiversity and ecosystem functioning. SEACHANGE addresses two key questions: 1) What was the nature of long-term changes in marine biodiversity and ecosystem functioning associated with major socioeconomic changes across the Mesolithic-Neolithic boundary over a 3000-year period in NW Europe? 2) What has been the scale and rate of marine biodiversity loss and changes to ecosystem functioning as a result of fishing intensity and marine habitat loss during the last 2000 years in the North Sea and around Iceland, Southeastern Brazil and the west Antarctic Peninsula?
To address these questions we are analysing: 1) absolutely-dated annually-resolved bivalve shell series; 2) marine sediment cores; 3) archaeological midden materials including shells and bones. We are dating these samples precisely and undertaking zooarchaeological and palaeoecological, stable isotope geochemical and environmental DNA/DNA analyses. We are comparing the data with historical and archival sources, and later in the project we will generate numerical ecosystem simulations. We will identify how the current marine environment differs from that before large scale human impact and what measures are needed, and how long will it take, for marine biodiversity to recover.
We are investigating five key cultural transitions which frame the proposed work packages (WP):
1. The European transition to farming (Mesolithic to Neolithic, 8K to 5K yrs BP; WP1)
2. The European pre-industrial to modern (last 2K yrs; WP2)
3. Hunter-gatherer (aboriginal) to colonial period in Brazil (last 6K yrs)(WP3)
4. The Viking age settlement of Iceland (WP4)
5. The advent of intensive whaling in Antarctica (WP5).
To address these questions we are analysing: 1) absolutely-dated annually-resolved bivalve shell series; 2) marine sediment cores; 3) archaeological midden materials including shells and bones. We are dating these samples precisely and undertaking zooarchaeological and palaeoecological, stable isotope geochemical and environmental DNA/DNA analyses. We are comparing the data with historical and archival sources, and later in the project we will generate numerical ecosystem simulations. We will identify how the current marine environment differs from that before large scale human impact and what measures are needed, and how long will it take, for marine biodiversity to recover.
We are investigating five key cultural transitions which frame the proposed work packages (WP):
1. The European transition to farming (Mesolithic to Neolithic, 8K to 5K yrs BP; WP1)
2. The European pre-industrial to modern (last 2K yrs; WP2)
3. Hunter-gatherer (aboriginal) to colonial period in Brazil (last 6K yrs)(WP3)
4. The Viking age settlement of Iceland (WP4)
5. The advent of intensive whaling in Antarctica (WP5).
In a paper that attracted considerable media attention, the full extent of depletion of the biogenic reef ecosystems built by the European flat oyster (Ostrea edulis) was shown. Documentary records published over 350 years were collated to create a map of historical oyster reef presence along European coasts. The analysis demonstrates that oyster reefs were once a dominant three-dimensional feature of European shelf seas, and their loss indicates a fundamental restructuring and ‘flattening’ of shallow-shelf seafloors. This unique record demonstrates the highly degraded nature of European seas and provides key baseline context for international restoration commitments. It also provides support for the SEACHANGE WP2 hypothesis that there were significant ecosystem changes in the North Sea before, during and after the industrial transition (WP2)
198 shells specimens from the North Icelandic Shelf (WP4) were processed. With the aid of AAG analysis 36 shell specimens were crossdated into the existing chronology, improving replication through the record and extending it further to the present (2005 – 2021). The new chronology has been used for geochemical sampling to update stable isotope records (δ18O and δ 13C).
δ13C and δ15N (bulk and CSIA) data of bone collagen samples of whales and seals from the Southern Ocean were generated and analysed in collaboration with NHMUK. Samples were originally obtained by NHM prior to and during the period of industrial whaling in Southern Hemisphere (WP5)
Cores from Fetlar Basin, Shetland, have produced evidence in offshore marine deposits of the Storegga tsunami. The cores contain sand and shell lenses within a Holocene mud sequence, indicating a sudden change in hydrodynamic conditions, while radiocarbon dates bracketing the lenses overlap with published dates for the Storegga event (WP1)
Sediment cores from Aarhus Bay, Limfjord and Vejle Fjord were sampled for eDNA analysis to investigate biodiversity changes across the Danish transition to agriculture (WP1).
DNA and metagenomic sequencing data were generated for samples from three sediment cores collected during the 2022 cruise (DY150) from around the Northern Isles, Scotland (WP2).
DNA and metagenomic sequencing data were generated from WP2 midden samples covering the medieval and post-medieval periods.
Generation of high-resolution shell growth and stable isotope (δ18O & δ13C) chronologies of A. islandica (WP1, 2, 4) to determine changes in physical environmental variables and potential changes in primary production through time.
Measurement of carbonate clumped isotopes (Δ47 values) of shell carbonate to verify absolute temperature estimates based on shell stable oxygen isotope data (WP1+2).
δ15N analysis (via BSIA, CSIA) of A. islandica shells (WP1, 2, 4) to determine temporal changes in N isotope baseline and trophic position of bivalves reflecting change in food web structure.
198 shells specimens from the North Icelandic Shelf (WP4) were processed. With the aid of AAG analysis 36 shell specimens were crossdated into the existing chronology, improving replication through the record and extending it further to the present (2005 – 2021). The new chronology has been used for geochemical sampling to update stable isotope records (δ18O and δ 13C).
δ13C and δ15N (bulk and CSIA) data of bone collagen samples of whales and seals from the Southern Ocean were generated and analysed in collaboration with NHMUK. Samples were originally obtained by NHM prior to and during the period of industrial whaling in Southern Hemisphere (WP5)
Cores from Fetlar Basin, Shetland, have produced evidence in offshore marine deposits of the Storegga tsunami. The cores contain sand and shell lenses within a Holocene mud sequence, indicating a sudden change in hydrodynamic conditions, while radiocarbon dates bracketing the lenses overlap with published dates for the Storegga event (WP1)
Sediment cores from Aarhus Bay, Limfjord and Vejle Fjord were sampled for eDNA analysis to investigate biodiversity changes across the Danish transition to agriculture (WP1).
DNA and metagenomic sequencing data were generated for samples from three sediment cores collected during the 2022 cruise (DY150) from around the Northern Isles, Scotland (WP2).
DNA and metagenomic sequencing data were generated from WP2 midden samples covering the medieval and post-medieval periods.
Generation of high-resolution shell growth and stable isotope (δ18O & δ13C) chronologies of A. islandica (WP1, 2, 4) to determine changes in physical environmental variables and potential changes in primary production through time.
Measurement of carbonate clumped isotopes (Δ47 values) of shell carbonate to verify absolute temperature estimates based on shell stable oxygen isotope data (WP1+2).
δ15N analysis (via BSIA, CSIA) of A. islandica shells (WP1, 2, 4) to determine temporal changes in N isotope baseline and trophic position of bivalves reflecting change in food web structure.
Amino acid geochronology (AAG) dating is a potentially less costly and more efficient range-finding method than radiocarbon dating. Examinination of protein degradation in each of the three microstructural layers of A. islandica showed that the inner portion of the outer shell layer (iOSL) was the most appropriate component to use for AAG dating. Although the resolution of this method is still too low for within-shell age resolution, it has been shown that this approach can be used to establish a relative geochronology through the whole of the Quaternary. In the late Holocene the temporal resolution is ∼1500–2000 years. This study confirms the value of A. islandica as a reliable material for range finding and for dating Quaternary deposits.
The impact of shell morphology, sample spot geometry, different sampling strategies and alignment methods on the reconstruction of environmental signals has been evaluated using numerically simulated environmental signals and digital shell models of A. islandica. This novel alignment method is superior to any existing alignment technique.
Amino acid-specific nitrogen isotope analysis (CSIA-AA) can be combined with with bivalve sclerochronology as a tool for the reconstruction of temporal changes of the ecosystem nitrogen isotope baseline, allowing the quantification of anthropogenic influences (and their rate of change) and the ability to track changing water masses and changes in the integrated food web complexity.
The stable nitrogen isotope (δ15N) composition of bivalve shell organics serves as a proxy for nitrogen fluxes in modern and past ecosystems. δ15N analyses of fossil shells should ideally be limited to the intra-crystalline organic matrix, as this is trapped within biomineral units and is less likely to be contaminated or diagenetically overprinted than inter-crystalline organics. The intra-crystalline approach has been shown to be resilient to diagenetic overprint, so it can provide pristine N isotope information for bulk (δ15N) and compound specific (CSIA-AA-δ15N) isotopes
Shell Ba/Ca (seasonal resolution, whole lifespan of individual) from A. islandica specimens (WP1, 2, 4) can be used to determine changes in frequency, duration and strength of blooms of specific Ba-containing primary producer species (mainly diatoms) and to extract information on primary producer blooms.
The impact of shell morphology, sample spot geometry, different sampling strategies and alignment methods on the reconstruction of environmental signals has been evaluated using numerically simulated environmental signals and digital shell models of A. islandica. This novel alignment method is superior to any existing alignment technique.
Amino acid-specific nitrogen isotope analysis (CSIA-AA) can be combined with with bivalve sclerochronology as a tool for the reconstruction of temporal changes of the ecosystem nitrogen isotope baseline, allowing the quantification of anthropogenic influences (and their rate of change) and the ability to track changing water masses and changes in the integrated food web complexity.
The stable nitrogen isotope (δ15N) composition of bivalve shell organics serves as a proxy for nitrogen fluxes in modern and past ecosystems. δ15N analyses of fossil shells should ideally be limited to the intra-crystalline organic matrix, as this is trapped within biomineral units and is less likely to be contaminated or diagenetically overprinted than inter-crystalline organics. The intra-crystalline approach has been shown to be resilient to diagenetic overprint, so it can provide pristine N isotope information for bulk (δ15N) and compound specific (CSIA-AA-δ15N) isotopes
Shell Ba/Ca (seasonal resolution, whole lifespan of individual) from A. islandica specimens (WP1, 2, 4) can be used to determine changes in frequency, duration and strength of blooms of specific Ba-containing primary producer species (mainly diatoms) and to extract information on primary producer blooms.