Biology subjects

Andrews, A. J.

Publications and source records attributed to Andrews, A. J..

6 recordsLinked to original sources

bioRxiv2025

Stable isotope insights into artificial reef effects of floating offshore energy structures in Norwegian North Sea codfishes

Offshore energy structures introduce hard substrate to soft substrate-dominant habitats and may act as artificial reefs providing shelter and food to aggregating fish. In the Northeast Atlantic, knowledge on these effects is limited to shallow habitats in the southern North Sea. Given that effects may be misinterpreted as nature positive contributions, or underestimated and impacting ecosystem services like fisheries, this data-gap hinders management. This is especially problematic for the rapid developments of floating offshore wind farms (OWFs), and decommissioning of oil and gas (O&G) platforms in deep (>100 m) habitats of Norway, the U.K. and Ireland. In this study, we analysed the stable isotopic composition of muscle and liver and the condition of three codfishes of commercial importance (saithe; Pollachius virens, tusk; Brosme brosme and ling; Molva molva) at a floating OWF and two floating O&G platforms off Norway to evaluate how codfish diet and habitat use may be altered by the structures. We find that differences in carbon, nitrogen and sulphur stable isotopes between offshore energy sites and control sites were lower for liver measurements (weeks prior to capture) than muscle (months prior to capture), indicating that codfish diet and habitat use was less impacted by offshore energy structures than longer-term natural feeding variation. Size explained some isotopic differences between sites in saithe, and condition differences between sites in tusk; suggesting that the diet and habitat use of the three species is not significantly impacted by offshore structures. However, we found evidence of lower condition in ling at Hywind Tampen OWF, corresponding to lower nitrogen isotope liver values in ling; that may indicate trade-offs in shelter and diet provision. Overall we highlight the need for further research on trophic effects of deep offshore energy structures to evaluate implications for management and conservation.

ecology↗

bioRxiv2025

Combining environmental DNA and traditional sampling to assess the role of kelp aquaculture as an artificial habitat in Norway

Kelp aquaculture is expanding rapidly in the temperate Atlantic, yet its ecological role as an artificial habitat remains poorly understood. This study assessed the biodiversity associated with wave-exposed kelp farms in coastal Norway using both environmental DNA (eDNA) and traditional sampling methods. Fish and invertebrate communities were surveyed at two kelp farms and compared to nearby natural kelp forests and pelagic control sites. Results from gill-net fishing, camera observations, and invertebrate sampling revealed lower species richness and abundance at kelp farms compared to natural habitats. eDNA analyses (12S and CO1 markers) showed few differences in community composition between sites, and no species were identified as indicators of kelp farms. Traditional sampling detected the presence of the amphipod Caprella mutica in the kelp farms, indicating that operators can play roles in alien species spread. Overall, kelp farms supported distinct but less diverse communities than natural kelp forests, being more similar to pelagic control sites. Finally, eDNA provided limited insights compared to traditional methods. These findings suggest that kelp farms currently provide limited habitat provisioning in Norway, likely as a result of how and where kelp aquaculture is currently performed. We suggest the need for population-level assessments for relevant species like Atlantic lumpfish (Cyclopterus lumpus) and locally based assessments in collaboration with authorities to define nature-positive or negative outcomes to balance ecological and economic goals in the growing seaweed aquaculture industries of the Atlantic.

ecology↗

bioRxiv2024

Ancient DNA reveals historical demographic decline and genetic erosion in the Atlantic bluefin tuna

Overexploitation has depleted fish stocks during the past century, nonetheless its genomic consequences remain poorly understood. Characterising the spatiotemporal patterns of these consequences may provide baseline estimates of past diversity and productivity to aid management targets, help predict future dynamics, and facilitate the identification of evolutionary factors limiting fish population recovery. Here, we evaluate human impacts on the evolution of the iconic Atlantic bluefin tuna (Thunnus thynnus), one of the longest and most intensely exploited marine fishes, with a tremendous cultural and economic importance. We sequenced whole genomes from modern (n=49) and ancient (n=41) specimens dating up to 5000 years ago, uncovering several novel findings. First, we identify temporally stable patterns of population admixture, as bluefin tuna caught off Norway and in the eastern Mediterranean share a greater degree of ancestry with Gulf of Mexico bluefin tuna than western and central Mediterranean bluefin tuna. This suggests that Atlantic spawning areas are important mixing grounds for the genetic diversity of Mediterranean bluefin tuna. We model effective population size to show that Mediterranean bluefin tuna began to undergo a demographic decline by the year 1900 to an extent not observed across the previous millennia. Coinciding with this, we found that heterozygosity and nucleotide diversity was significantly lower in modern (2013-2020), than ancient (pre-1941) Mediterranean bluefin tuna, suggesting bluefin tuna underwent a genetic bottleneck. With this work we show how ancient DNA provides novel perspectives on ecological complexity with the potential to inform the management and conservation of fishes. SignificanceAchieving the aim of the current UN Ocean Decade to "protect and restore ecosystems and biodiversity" is stymied by a lack of historical knowledge on how human exploitation has impacted and therefore what should be restored. Here, we sequence DNA in ancient fish bones to evaluate the historical diversity of the Atlantic bluefin tuna; which has been of great commercial importance for centuries. We find that bluefin tuna began to undergo demographic decline by 1900, 70 years earlier than currently recognised. Correspondingly, we find modern bluefin tuna had lower levels of genetic diversity than historical ones. This suggests that human impacts on the diversity of marine fishes are likely to have begun earlier and be more complex than previously thought.

ecology↗

bioRxiv2024

Five millennia of mitochondrial introgression in Atlantic bluefin tuna identified using ancient DNA

Mitogenomic (MT) introgression between species is readily documented in marine fishes. Such introgression events may either be long-term natural phenomena or the result of human-driven shifts in spatial distributions of previously separated species. Determining the drivers behind MT introgression is stymied by the difficulty of directly observing patterns of interbreeding over long timescales. Using ancient DNA spanning five millennia, we here investigate the long-term presence of MT introgression from Pacific bluefin tuna (Thunnus orientalis) and albacore (Thunnus alalunga) into Atlantic bluefin tuna (Thunnus thynnus), a species with extensive exploitation history and observed shifts in abundance, and demographic distribution. Comparing ancient (n=130) and modern (n=78) mitogenomes of specimens covering most of the range of Atlantic bluefin tuna we detect no significant spatial or temporal population structure. This lack of spatiotemporal genomic differentiation is indicative of ongoing gene flow between populations and large effective population sizes over millennia. Moreover, we identify introgressed MT genomes in ancient specimens up to 5000 years old and find that this rate of introgression has remained similar through time. We therefore conclude that MT introgression in the Atlantic bluefin tuna is to date unaffected by anthropogenic impacts. By providing the oldest example of directly observed MT introgression in the marine environment, our results highlight the utility of ancient DNA to obtain temporal insights in the long-term persistence of such phenomena.

evolutionary biology↗

bioRxiv2020

Surprising Phenotypic Diversity of Cancer-associated mutations of Gly 34 in the Histone H3 tail

Sequencing of cancer genomes has identified recurrent somatic mutations in histones, termed oncohistones, which are frequently poorly understood. Previously we showed that fission yeast expressing only the H3.3G34R mutant identified in aggressive pediatric glioma had reduced H3K36 trimethylation and acetylation, increased genomic instability and replicative stress, and defective homology-dependent DNA damage repair (Yadav et al., 2017). Here we show that surprisingly distinct phenotypes result from G34V (also in glioma) and G34W (giant cell tumors of bone) mutations, differentially affecting H3K36 modifications, subtelomeric silencing, genomic stability, sensitivity to irradiation, alkylating agents, hydroxyurea and influencing DNA repair. In cancer, only one of thirty alleles encoding H3 is mutated. Whilst co-expression of wild-type H3 rescues most G34 mutant phenotypes, G34R causes dominant hydroxyurea sensitivity and homologous recombination defects, and dominant subtelomeric silencing. Together, these studies demonstrate the complexity associated with different substitutions at even a single residue in H3 and highlight the utility of genetically tractable systems for their analysis.

molecular biology↗

bioRxiv2018

Dispersal routes of climate-induced marine range expansions into the Arctic

As a result of ocean warming, the species composition of the Arctic seas has begun to shift in a boreal direction. One ecosystem prone to fauna shifts is the Northeast Greenland shelf. The dispersal route taken by boreal fauna to this area is, however, not known. This knowledge is essential to predict to what extent boreal biota will colonise Arctic habitats. Using population genetics, we show that Atlantic cod (Gadus morhua), beaked redfish (Sebastes mentella), and deep-sea shrimp (Pandalus borealis) specimens recently found on the Northeast Greenland shelf originate from the Barents Sea, and suggest that pelagic offspring were dispersed via advection across the Fram Strait. Our results indicate that boreal invasions of Arctic habitats can be driven by advection, and that the fauna of the Barents Sea can project into adjacent habitats with the potential to colonise putatively isolated Arctic ecosystems such as Northeast Greenland.

ecology↗