A compilation of surface inherent optical properties and phytoplankton pigment concentrations from the Atlantic Meridional Transect

In situ measurements of particulate inherent optical properties (IOPs) – absorption (ap(λ)), scattering (bp(λ)), and beam attenuation (cp(λ)) – are crucial for the development of optical algorithms that retrieve biogeochemical quantities such as chlorophyll a, particulate organic carbon (POC), and total suspended matter (TSM). Here we present a compilation of particulate absorption–attenuation spectrophotometric data measured underway on nine Atlantic Meridional Transect (AMT) cruises between 50° N and 50° S from 2009–2019. The compilation includes coincident high-performance liquid chromatography (HPLC) phytoplankton pigment concentrations, which are used to calibrate transects of total chlorophyll a (Tot_Chl_a) concentrations derived from the ap(λ) line-height method. The IOP data are processed using a consistent methodology and include propagated uncertainties for each IOP variable, uncertainty quantification for the Tot_Chl_a concentrations based on HPLC match-ups, application of consistent quality-control filters, and standardization of output data fields and formats. The total IOP dataset consists of ∼310 000 measurements at a 1 min binning (∼270 000 hyper-spectral) and >700 coincident HPLC pigment surface samples (∼600 of which are coincident with hyper-spectral IOPs). We present the geographic variation in the IOPs, HPLC phytoplankton pigments, and ap-derived Tot_Chl_a concentrations which are shown to have uncertainties between 8 % and 20 %. Additionally, to stimulate further investigation of accessory pigment extraction from ap(λ), we quantify pigment correlation matrices and identify spectral characteristics of end-member ap(λ) spectra, where accessory pigment groupings are present in higher concentrations relative to Tot_Chl_a. All data are made publicly available in SeaBASS and NetCDF formats via the following links: https://seabass.gsfc.nasa.gov/archive/PML/AMT (Jordan et al., 2025a) and https://doi.org/10.5281/zenodo.12527954 (Jordan et al., 2024)

Can the emerging European seaweed industry contribute to climate change mitigation by enhancing carbon sequestration?

Blue carbon habitats, which exhibit high rates of natural carbon sequestration, typically refer to salt marshes, seagrass meadows, and mangrove forests. Recent studies, however, have argued for the inclusion of seaweed-dominated habitats, like kelp forests, into blue carbon frameworks. Farmed seaweed may also function as a blue carbon habitat, with large-scale seaweed aquaculture suggested as a climate change mitigation strategy, but the evidence base remains limited. Here, existing knowledge on the mechanisms influencing carbon uptake, release, transport, and storage from kelp farms was synthesised, and a literature review was conducted to quantify associated rates of carbon sequestration. We identified strong geographical and methodological biases in the literature, with the majority of studies conducted in Asia and focusing on primary production rates as a proxy for carbon sequestration potential. Estimates of carbon release and storage rates were highly variable across locations, species, and approaches, and a scarcity of research on dissolved organic carbon, sedimentary carbon, and net ecosystem productivity was identified. Although the European kelp farming industry is in its infancy, it is predicted to expand to meet increasing demand for seaweed biomass. This is incentivised by perceived associated ecosystem service benefits such as enhanced carbon sequestration. However, multiple factors including environmental concerns, a lack of quantitative evidence, operational challenges, and regulatory complexities hinder industry expansion. Based on both the synthesised empirical evidence and an examination of key barriers and knowledge gaps, we identify future challenges and research priorities needed to assess the role of seaweed farming for climate change mitigatio

Resource acquisition in diel cycles and the cost of growing quickly

Many organisms, notably phototrophs, routinely acquire resources over only a fraction of the day. They have to balance their main period of initial biosynthesis against cell cycle events. Because of their short generation times, this challenge is especially acute for the planktonic microalgae that perform 50% of global C-fixation. Empirical evidence indicates that microalgal day-average growth is a function of the ability to acquire resources rapidly when available, retaining initial products of assimilation to support growth. A fundamental question arises over the optimal physiological configuration to support such activity. Here, we applied computer simulations implementing a development of the quota concept, in which the internal limiting resource is itself C, ratioed against total organism C-biomass. The model comprises metabolite and core pools of carbon C ( M C and C C , respectively), with growth modulated by M C /( M C + C C ); M C supports growth of C C in the absence of concurrent resource acquisition. Dynamic feedback interactions from the relative size of M C controls resource acquisition. The model reproduces the general pattern of growth at different light:day fraction ( LD ), and of afternoon-depression of C-fixation. We explored the efficiency of the physiological cell configuration to locate optimal configurations at different combinations of maximum growth rates ( U max ) and LD values across plausible parameter values for microalgae. While the optimum maximum resource acquisition rate deployed during the L phase scales with U max / LD , the maximum size of the metabolite pool scales to LD / DV , where DV is division time (i.e. U max /Ln(2)). Accordingly, we conclude that faster growing organisms carry a penalty limiting their geographic spread to latitudes and seasons where LD is high. Larger, vacuolated organisms (such as diatoms), having a bigger metabolite compartment, may be at an advantage in such situations

Ocean Acidification: Another Planetary Boundary Crossed

Ocean acidification has been identified in the Planetary Boundary Framework as a planetary process approaching a boundary that could lead to unacceptable environmental change. Using revised estimates of pre‐industrial aragonite saturation state, state‐of‐the‐art data‐model products, including uncertainties and assessing impact on ecological indicators, we improve upon the ocean acidification planetary boundary assessment and demonstrate that by 2020, the average global ocean conditions had already crossed into the uncertainty range of the ocean acidification boundary. This analysis was further extended to the subsurface ocean, revealing that up to 60% of the global subsurface ocean (down to 200 m) had crossed that boundary, compared to over 40% of the global surface ocean. These changes result in significant declines in suitable habitats for important calcifying species, including 43% reduction in habitat for tropical and subtropical coral reefs, up to 61% for polar pteropods, and 13% for coastal bivalves. By including these additional considerations, we suggest a revised boundary of 10% reduction from pre‐industrial conditions more adequately prevents risk to marine ecosystems and their services; a benchmark which was surpassed by year 2000 across the entire surface ocean

Mind the gap - The need to integrate novel plankton methods alongside ongoing long-term monitoring

Changes in plankton have important implications for ecosystem services, including supporting fish stocks, carbon sequestration, nutrient cycling, and oxygen production. Standard long-term plankton monitoring relies on light microscopy to identify and count plankton taxa, with methods fully supported by international standards, providing high quality trusted data. Novel methods, including imaging and molecular, offer means of collecting select types of plankton data efficiently, filling targeted knowledge gaps left by standard monitoring and generating a more complete picture of plankton dynamics. Standard and novel monitoring methods present different advantages and costs, positioning their suitability to address different management needs. Standard plankton monitoring time-series are unique in providing the long-term temporal coverage, and thus statistical power, needed to detect and understand climate change impacts. When explored in parallel with standard monitoring, novel methods open doors to observing our seas from complementary perspectives, but further work is necessary before data from standard and novel methods can be integrated to address policy needs. Marine management priorities are shifting, and novel methods are increasingly proposed as possible alternatives to standard monitoring. However, for a long-term taxonomic perspective it is still essential to retain the specialist skills and maintain standard monitoring time-series to inform policy assessments of important changes in pelagic biodiversity. This review aims to inform readers of the value of long-term data, the importance of retaining taxonomic skills and embracing novel methods for marine plankton monitoring to assess pelagic biodiversity. We recommend strategies to maintain long-term monitoring whilst incorporating novel method

Acute and partial life-cycle toxicity of a tri-polymer blend of microplastics in the copepod Acartia tonsa

Microplastics are a prolific environmental contaminant that pose a risk to marine organisms. Ecotoxicological studies have identified microplastics can cause sub-lethal harm to aquatic biota. However, prior studies often lack comparability and environmental relevance, for example focussing upon monodisperse beads at extremely high concentrations. Copepods are keystone marine taxa that play vital roles in the marine food web and biogeochemical cycling. In this study, we adapted ISO methods to conduct acute and partial life-cycle toxicity tests exposing adult and juvenile life stages of the copepod Acartia tonsa to a fully characterised tri-polymer microplastic blend comprising cryoground polyethylene, polypropylene, and nylon particles (5–100 μm) at concentrations ranging 0–1000 μg L− 1 . The tests considered the toxicity of microplastics on a wide number of endpoints including adult survival, algal ingestion rates, egg production and size, larval development ratio and juvenile survival. Mortality, egg size and larval development ratio proved to be the most sensitive endpoints. The tri-polymer blend had an LC5072h value of 182 μg L− 1 providing a baseline for future toxicity testing using this method

Insights into the origins of calcification from coccolithophore life cycles

Marine phytoplankton play critical roles in global biogeochemical cycles, so it is remarkable that fundamental aspects of their biology remain poorly understood. One striking example is our incomplete understanding of life-cycle histories in many phytoplankton groups. The coccolithophores, with their characteristic cell covering of calcium carbonate plates (coccoliths), represent a lineage for which much remains to be learned about their life cycle. Most studies have focused on the heavily calcified diploid phase. However, coccolithophores can also exist in a haploid phase that is lightly calcified and often motile. Both phases can persist in the environment and reproduce asexually, representing a haplo-diplontic life cycle. The comparative biology of these life-cycle phases and the environmental factors that trigger switching between them remain poorly understood, representing a significant knowledge gap in coccolithophore biology, particularly when predicting their response to future environmental change (Frada et al., 2018

Fusion, fission, and scrambling of the bilaterian genome in Bryozoa

Groups of orthologous genes are commonly found together on the same chromosome over vast evolutionary distances. This extensive physical gene linkage, known as macrosynteny, is seen between bilaterian phyla as divergent as Chordata, Echinodermata, Mollusca, and Nemertea. Here, we report a unique pattern of genome evolution in Bryozoa, an understudied phylum of colonial invertebrates. Using comparative genomics, we reconstruct the chromosomal evolutionary history of five bryozoans. Multiple ancient chromosome fusions followed by gene mixing led to the near-complete loss of bilaterian linkage groups in the ancestor of extant bryozoans. A second wave of rearrangements, including chromosome fission, then occurred independently in two bryozoan classes, further scrambling bryozoan genomes. We also discover at least five derived chromosomal fusion events shared between bryozoans and brachiopods, supporting the traditional but highly debated Lophophorata hypothesis and suggesting macrosynteny to be a potentially powerful source of phylogenetic information. Finally, we show that genome rearrangements led to the dispersion of genes from bryozoan Hox clusters onto multiple chromosomes. Our findings demonstrate that the canonical bilaterian genome structure has been lost across all studied representatives of an entire phylum, and reveal that linkage group fission can occur very frequently in specific lineage

Evidence of climate change (intertidal indicators)

Rocky shore species live in habitats that are exposed to both terrestrial and marine climates during the diurnal tidal cycle, and so provide a unique perspective on the genetic and physiological adaptations to survival in a constantly changing, environmentally challenging ecosystem. Most intertidal animals and seaweed are fixed to the rock or can only move small distances, which places them at the mercy of long-term climate change and extreme events such as heatwaves and storm events that are increasing in frequency and severity. As a result, they have shown some of the fastest responses to global warming in any system on the planet, shifting their geographic distributions to higher latitudes where sea and air temperatures are cooler. The rocky shore is an accessible habitat to study, and scientists have been able to look at the biological pathways by which different creatures respond to changes in climate by carrying out long-term surveys and experiments. The rapid responses to changes in temperature and the large amount of knowledge of their biological processes mean that intertidal species can be used as indicators of the biological effects that climate change is having within the marine real

Chemical composition of the harvested subtidal kelp, Lessonia trabeculata, from a coastal location in central Chile

Kelp forests are important ecosystem engineers in temperate and sub-polar regions, providing ecosystem services valued at billions of dollars annually. In Chile, over 72,000 tons/yr of wet subtidal kelp (Lessonia trabeculata) are harvested annually for the alginate industry, yet its chemical variation remains poorly understood. In this study we examined the alginate content and nutritional profile (i.e., proximal analyses) across different kelp morphological structures (holdfasts and stipes) over 8 months in Las Cruces, Central Chile (33°SL). Each month, tissue from six sporophytes was pooled and averaged, resulting in eight independent samples (n = 8 months), with each sample analyzed in triplicate. Results revealed significant variability between kelp morphological structures and across seasons. Alginate and carbohydrate concentrations peaked in austral summer, with patterns of interannual variation identified. Protein and fiber contents were higher than those in other kelp species, peaking in spring and summer, while lipid concentration peaked in autumn but remained relatively stable year-round. All compounds were generally more abundant in holdfasts. These findings suggest a potential for extracting high-value compounds, such as proteins, from L. trabeculata beyond the current alginate focus. Interannual variations as well as corresponding trends between kelp composition and physico-chemical properties of surface seawater were also observed, highlighting the need for further research to understand and predict these patterns better. These findings could help pinpoint the best harvesting times for specific chemical profiles, boosting profitability while reducing environmental impact