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Abstract: Satellite records of chlorophyll, sea-surface temperature, sea-ice concentration and wind-stress curl, together with reanalysis wind fields, have been analysed to identify connections between the physical environment and phytoplankton growth. The study focusses on the BROKE-West survey region in the Indian Ocean sector of the Southern Ocean: 20° to 90°E, 70° to 50°S. Correlation and regression analyses showed that, of the parameters that can be routinely monitored from space, wind stress and sea surface temperature were most strongly correlated with chlorophyll across the BROKE-West survey area during the period of the survey. Each of these factors, as well as sea ice concentration, was found to be strongly correlated with chlorophyll at different locations. Three distinct regions were identified: The continental shelf and slope (max. depth=3000m), where satellite data were most obstructed by ice and clouds, supported high concentrations of chlorophyll throughout the growth season (October to April), and although the most important factors determining chlorophyll were likely to be those not observable using remote sensing, close to 100% of variability in surface chlorophyll could be predicted by sea-surface temperature and sea ice concentration. Offshore to the west of 45°E, the eastern Weddell Gyre was found to retain sea-ice later into the growth season and support chlorophyll concentrations on the order of 0.1mgm−3. Wind-driven advection of sea ice to the north and south of the Antarctic Divergence, located at 64°S, produced a strong positive correlation between chlorophyll concentrations along the landward and off-shore edges of the seasonal ice zone and the Southern Annular Mode. Offshore to the east of 45°E, chlorophyll concentrations encountered during the BROKE-West cruise were found to be unusually high. This was attributed to a southerly excursion of the Antarctic Circumpolar Current corresponding to negative Southern Annular Mode indices during the cruise. Significant, regionally varying correlations were found between the physical and biological parameters examined and climatological indices, including the Southern Annular Mode and the tropical El Nino-Southern Oscillation signal. [Copyright &y& Elsevier]

Understanding marine predator distributions is an essential component of arresting their catastrophic declines. 1,2,3,4 In temperate, polar, and upwelling seas, predictable oceanographic features can aggregate migratory predators, which benefit from site-based protection. 5,6,7,8 In more oligotrophic tropical waters, however, it is unclear whether environmental conditions create similar multi-species hotspots. We track the non-breeding movements and habitat preferences of a tropical seabird assemblage (n = 348 individuals, 9 species, and 10 colonies in the western Indian Ocean), which supports globally important biodiversity. 9,10,11,12 We mapped species richness from tracked populations and then predicted the same diversity measure for all known Indian Ocean colonies. Most species had large non-breeding ranges, low or variable residency patterns, and specific habitat preferences. This in turn revealed that maximum species richness covered >3.9 million km2, with no focused aggregations, in stark contrast to large-scale tracking studies in all other ocean basins. 5,6,7,13,14 High species richness was captured by existing marine protected areas (MPAs) in the region; however, most occurred in the unprotected high seas beyond national jurisdictions. Seabirds experience cumulative anthropogenic impacts 13 and high mortality 15,16 during non-breeding. Therefore, our results suggest that seabird conservation in the tropical Indian Ocean requires an ocean-wide perspective, including high seas legislation. 17 As restoration actions improve the outlook for tropical seabirds on land 18,19,20,21,22 and environmental change reshapes the habitats that support them at sea, 15,16 appropriate marine conservation will be crucial for their long-term recovery and whole ecosystem restoration. • Non-breeding seabirds dispersed widely across tropical Indian Ocean • Divergent habitat use and itinerancy preclude localized aggregations • Diffuse richness >3.9 M km2, contrary to multi-species tracking in other oceans • Indian Ocean tropical seabird conservation requires high seas perspective Marine predators often aggregate in highly productive areas. In contrast, Trevail et al. found divergent habitat use and itinerancy of non-breeding seabirds in the tropical Indian Ocean caused diffuse species richness across >3.9 M km2. These findings challenge marine predator distribution paradigms and highlight the need for high seas legislation. [ABSTRACT FROM AUTHOR]

A comprehensive in situ dataset of chlorophyll a (Chl a ; N = 18,001), net primary production (NPP; N = 165) and net community production (NCP; N = 95), were used to evaluate the performance of Moderate Resolution Imaging Spectroradiometer on Aqua (MODIS-A) algorithms for these parameters, in the South Atlantic Ocean, to facilitate the accurate generation of satellite NCP time series. For Chl a , five algorithms were tested using MODIS-A data, and OC3-CI performed best, which was subsequently used to compute NPP. Of three NPP algorithms tested, a Wavelength Resolved Model (WRM) was the most accurate, and was therefore used to estimate NCP with an empirical relationship between NCP with NPP and sea surface temperature (SST). A perturbation analysis was deployed to quantify the range of uncertainties introduced in satellite NCP from input parameters. The largest reductions in the uncertainty of satellite NCP came from MODIS-A derived NPP using the WRM (40%) and MODIS-A Chl a using OC3-CI (22%). The most accurate NCP algorithm, was used to generate a 16 year time series (2002 to 2018) from MODIS-A to assess climate and environmental drivers of NCP across the South Atlantic basin. Positive correlations between wind speed anomalies and NCP anomalies were observed in the central South Atlantic Gyre (SATL), and the Benguela Upwelling (BENG), indicating that autotrophic conditions may be fuelled by local wind-induced nutrient inputs to the mixed layer. Sea Level Height Anomalies (SLHA), used as an indicator of mesoscale eddies, were negatively correlated with NCP anomalies offshore of the BENG upwelling fronts into the SATL, suggesting autotrophic conditions are driven by mesoscale features. The Agulhas bank and Brazil-Malvinas confluence regions also had a strong negative correlation between SLHA and NCP anomalies, similarly indicating that NCP is forced by mesoscale eddy generation in this region. Positive correlations between SST anomalies and the Multivariate ENSO Index (MEI) in the SATL, indicated the influence of El Niño events on the South Atlantic Ocean, however the plankton community response was less clear. • Accuracy of satellite Chl a , NPP and NCP assessed in the South Atlantic Ocean. • First 16 year time series of satellite based NCP. • Wind speed and mesoscale processes control regional NCP. [ABSTRACT FROM AUTHOR]