Saltmarsh blue carbon accumulation rates and their relationship with sea-level rise on a multi-decadal timescale in northern England

Feldwork and elemental and thermogravimetric analyses were conducted as a part of the NERC funded (NE/R010846/1) Carbon Storage in Intertidal Environments (C-SIDE) project (https://www.c-side.org/).Saltmarshes are widely thought to sequester carbon at rates significantly exceeding those found in terrestrial environments. This ability arises from the in-situ production of plant biomass and the effective trapping and storage of both autochthonous and allochthonous organic carbon. The role saltmarshes play in climate change mitigation, through accumulating ‘blue’ carbon, depends on both the rate at which carbon accumulates within sediments and the rapidity with which carbon is remineralised. It has been hypothesized that carbon accumulation rates, in turn, depend on the local rate of relative sea-level rise, with faster sea-level rise providing more accommodation space for carbon storage. This relationship has been investigated over long (millennial) and short (decadal) timescales but without accounting for the impact of higher quantities of labile carbon in more recently deposited sediment. This study addresses these three key aspects in a saltmarsh sediment study from Lindisfarne National Nature Reserve (NNR), northern England, where there is a comparatively pristine marsh. We quantify rates of carbon accumulation by combining a Bayesian age-depth model based on 210Pb and 137Cs activities with centimetre-resolution organic carbon density measurements. We also use thermogravimetric analyses to determine the relative proportions of labile and recalcitrant organic matter and calculate the net recalcitrant organic matter accumulation rate. Results indicate that during the 20th century more carbon accumulated at the Lindisfarne NNR saltmarsh during decades with relatively high rates of sea-level rise. The post-depositional loss of labile carbon down the core results in a weaker though still significant relationship between recalcitrant organic matter accumulation and sea-level change. Thus, increasing saltmarsh carbon accumulation driven by higher rates of sea-level rise is demonstrated over recent multi-decadal timescales.Peer reviewe

Detailed Analysis of a Contiguous 22-Mb Region of the Maize Genome

Most of our understanding of plant genome structure and evolution has come from the careful annotation of small (e.g., 100 kb) sequenced genomic regions or from automated annotation of complete genome sequences. Here, we sequenced and carefully annotated a contiguous 22 Mb region of maize chromosome 4 using an improved pseudomolecule for annotation. The sequence segment was comprehensively ordered, oriented, and confirmed using the maize optical map. Nearly 84% of the sequence is composed of transposable elements (TEs) that are mostly nested within each other, of which most families are low-copy. We identified 544 gene models using multiple levels of evidence, as well as five miRNA genes. Gene fragments, many captured by TEs, are prevalent within this region. Elimination of gene redundancy from a tetraploid maize ancestor that originated a few million years ago is responsible in this region for most disruptions of synteny with sorghum and rice. Consistent with other sub-genomic analyses in maize, small RNA mapping showed that many small RNAs match TEs and that most TEs match small RNAs. These results, performed on ∼1% of the maize genome, demonstrate the feasibility of refining the B73 RefGen_v1 genome assembly by incorporating optical map, high-resolution genetic map, and comparative genomic data sets. Such improvements, along with those of gene and repeat annotation, will serve to promote future functional genomic and phylogenomic research in maize and other grasses

Sea-level change, carbon storage and greenhouse gas fluxes in a Northumberland (UK) salt marsh

Salt marshes are currently receiving increased attention because of their ability to act as climate change mitigators by sequestering carbon at high rates, while also providing multiple co-benefits. However, questions still exist concerning the precise functioning of these ecosystems which need to be addressed before any climate offsetting benefit is quantified. Using separate but linked elements, this study addresses two main questions aimed at providing more certainty about natural salt marsh functioning: first, the impact of sea-level rise on carbon accumulation rate and, second, the extent to which greenhouse gas fluxes – carbon dioxide, methane and nitrous oxide – detract from carbon sequestration. To this end, a proxy based sea-level reconstruction was developed for a salt marsh at Lindisfarne, Northumberland (UK). Complementary tide-gauge data were compared with high-resolution carbon and sediment accretion rates calculated for each centimetre down a core of sediment. Further, greenhouse gas fluxes were measured using static chambers across the marsh surface and converted to carbon dioxide equivalents from which estimates of net radiative balance were calculated. Rates of relative sea-level change over a ~60-year period were found to explain a significant proportion of variation in carbon accumulation rate, with high rates of sea-level rise associated with increased rates of carbon accumulation. The net radiative balance of the high marsh zone was -6.03 ± 2.20 SD t CO2 eq ha-1 yr-1, meaning that a beneficial net impact is still achieved when greenhouse gas fluxes are included in calculations. These findings support the assertion that salt marshes have a role to play as nature-based climate solutions. If the results of this study are reflected in other locations, it will be possible to state that where marshes keep pace with sea-level rise, increased carbon sequestration is likely and will not be significantly negated by greenhouse gas emissions from the marsh

Raw Gas Flux Data.xlsx

Complete gas flux data set shown on the first sheet with values deleted from the second sheet and not carried forward to flux calculations highlighted in red. </p

Age Modelling R Code

R script used to produce age model for core LI21/20 and obtain sediment accretion rates for each centimetre of sediment. </p