Hyperspectral reflectance spectra of floating matters derived from HICO observations

Using data collected by the Hyperspectral Imager for the Coastal Ocean (HICO) on the International Space Station between 2010–2014, hyperspectral reflectance of various floating matters in global oceans and lakes are derived for the spectral range of 400–800 nm. Specifically, the entire HICO archive of 9,411 scenes is first visually inspected to identify suspicious image slicks. Then, a nearest-neighboring atmospheric correction is used to derive surface reflectance of slick pixels. Finally, a spectral unmixing scheme is used to derive the reflectance spectra of floating matters. Analysis of the spectral shapes of these various floating matters (macroalgae, microalgae, organic particles, whitecaps) through the use of a Spectral Angle Mapper (SAM) index indicates that they can mostly be distinguished from each other without the need of ancillary information. Such reflectance spectra from the consistent 90-m resolution HICO observations are expected to provide spectral endmembers to differentiate and quantify the various floating matters from existing multi-band satellite sensors and future hyperspectral satellite missions such as NASA’s Plankton, Aerosol, Cloud, and ocean Ecosystem (PACE) mission and Surface Biology and Geology (SBG) mission.

Gap-Filling of Ocean Color Over the Tropical Indian Ocean Using Monte-Carlo Method

Continuous remote-sensed daily fields of ocean color now span over two decades; however, it still remains a challenge to examine the ocean ecosystem processes, e.g., phenology, at temporal frequencies of less than a month. This is due to the presence of significantly large gaps in satellite data caused by clouds, sun-glint, and hardware failure; thus, making gap-filling a prerequisite. Commonly used techniques of gap-filling are limited to single value imputation, thus ignoring the error estimates. Though convenient for datasets with fewer missing pixels, these techniques introduce potential biases in datasets having a higher percentage of gaps, such as in the tropical Indian Ocean during the summer monsoon, the satellite coverage is reduced up to 40% due to the seasonally varying cloud cover. In this study, we fill the missing values in the tropical Indian Ocean with a set of plausible values (here, 10,000) using the classical Monte-Carlo method and prepare 10,000 gap-filled datasets of ocean color. Contrary to the previously used gap-filled datasets, the ecological indicators derived using our gap-filled datasets also quantifies uncertainty indicating the likelihood of estimates. Quantification of uncertainty is critical to address the importance of underlying datasets and hence, motivating future observations.

Tiny Phytoplankton: The Most Powerful Organisms of the Oceans!

Although sharks, whales, and other large organisms come to mind when one thinks about the most important or most powerful organisms of the sea, in fact, the most powerful are the tiny phytoplankton. Phytoplankton, which are microscopic algae, hold this power because they harvest the light from the sun, making food for all other organisms. Phytoplankton are the foundation for the ocean ecosystem. Through the process of photosynthesis, they also make oxygen and are responsible for almost half of the oxygen in the world. However, some phytoplankton can also be harmful and can kill fish or damage ecosystems. These harmful phytoplankton can also make people sick. The phytoplankton are tiny but mighty!

Disentangling marine microbial networks across space

Although microbial interactions underpin ocean ecosystem functions, they remain barely known. Different studies have analyzed microbial interactions using static association networks based on omics-data. However, microbial associations are dynamic and can change across physicochemical gradients and spatial scales, which needs to be considered to understand the ocean ecosystem better. We explored associations between archaea, bacteria, and picoeukaryotes along the water column from the surface to the deep ocean across the northern subtropical to the southern temperate ocean and the Mediterranean Sea by defining sample-specific subnetworks. Quantifying spatial association recurrence, we found the lowest fraction of global associations in the bathypelagic zone, while associations endemic of certain regions increased with depth. Overall, our results highlight the need to study the dynamic nature of plankton networks and our approach represents a step forward towards a better comprehension of the biogeography of microbial interactions across ocean regions and depth layers.

Sculpture and New Technologies in Scientific Educational Outreach: 3D Foraminiferal Models as a Referent of Ocean Acidification and Climate Change

The Foraminifera Project is a collaboration between researchers of the Faculty of Fine Arts and the Faculty of Geological Sciences at the Complutense University (UCM, Madrid, Spain). The work, based on scientific dissemination through art, is framed in the theme “Climate change and Ocean Acidification'' as part of the course “Art, Science and Nature” of the Master's Degree in Research in Art and Creation (Faculty of Fine Arts, UCM). The team used recent sediment samples from Indian Ocean and Red Sea that contained healthy and unhealthy foraminifera specimens to create 3D specimen models. These models were made using traditional sculpture techniques, photogrammetry, and 3D printing to show different states of foraminifera dissolution and corrosion from ocean acidification. The end result of this project resulted in nine interactive pieces which were part of the exhibition “Drift & Migrate'' open to the public during the month of November 2019 in the exhibition hall of the Faculty of Fine Arts (UCM). The 3D models of foraminifera were displayed with educational graphics and blind-accesible explanatory signage (Braille) to share the scientific facts of foraminifera and their role in the ocean ecosystem. The main objective of the collaboration is to raise awareness of anthropogenic effects on foraminifera and the marine ecosystems in general and to expand research opportunities between the arts and sciences at the university.

Sclerochronology in the Southern Ocean

This manuscript aims to provide a comprehensive review of the work done by Antarctic sclerochronology research across different taxa (arthropods, bivalves, brachiopods, bryozoans, cephalopods, hard and soft corals, gastropods, echinoderms and teleost fish), provide an analysis of current challenges in the discipline and start a discussion of what sclerochronology can offer for Antarctic research in future. The Southern Ocean ecosystem remains largely unstudied in part for its remoteness, extreme climate and strong seasonality. This lack of knowledge, some of it even on basic biological information, it is especially worrying due to ongoing climate-driven changes that the Southern Ocean ecosystem is experiencing. Lack of long-term in situ instrumental series has also being a detriment to understand long-term feedbacks between the physical environment and the ecosystem. Sclerochronology, the study of periodic accretional patterns in the hard body structures of living organisms, has contributed to a wide range of Antarctic research disciplines (e.g. paleoclimate reconstructions, population structure analysis, environmental proxies). This review highlights a disparity in research focus by taxa with some groups (e.g. bivalves, teleost fish) attracting most of the research attention, whereas other groups (e.g. gastropod) have attracted much little research attention or in some cases it is almost non-existent (e.g. echinoderms). Some of the long-lived species considered in this review have the potential to provide the much-needed high-resolution eco-environmental proxy data and play an important role in blue carbon storage in the Sothern Ocean. Another issue identified was the lack of cross-validation between analytical techniques. Graphic abstract