Feature Papers of Oceans 2024

1. Introduction

As the noted futurist and author Arthur C. Clarke famously remarked, our world of Planet Earth should be more appropriately named Planet Ocean [1]. The global ocean covers nearly three-quarters of the planet’s surface and, considering its great depths, makes up roughly 99% of the planet’s total habitable space [2]. Life is presumed to have originated in the sea, and the ocean remains the home of an estimated 94% of global wildlife, including 78% of the planet’s animal biomass [2,3,4]. Although the ocean houses most of our planet’s life, we know far more about terrestrial ecosystems. Fewer than a million marine species have been described, yet according to one estimate [5], the total number of undescribed marine species may be as high as ten million. Of the 33 known animal phyla, only 12 are found on land and only 1 is endemic to land, whereas 32 occur in the oceans and 14 are endemic there [3]. The ocean has an outsize impact on land, with at least half of Earth’s atmospheric oxygen coming from the sea and roughly 30% of its carbon dioxide absorbed by the sea, being the planet’s single greatest carbon sink [4]. Every bit of Earth’s global climate, even on land far from the sea, is governed by the ocean’s mass of water, its remarkable thermal inertia, and its powerful conveyor currents [5,6,7,8].

In terms of humans, the ocean’s impact is no less profound, even if we often forget this impact on our daily lives. The ocean is a major source of food, especially protein in the form of finfish and shellfish. It provides biological materials such as agarose gel and carrageenan (both from seaweed), which are used as thickeners and stabilizers in shampoo, toothpaste, other toiletry products, and foods such as ice cream. Many medicines and biofuels come from the sea [4]. It is a prime source of energy, including extracted oil, gas, and other petroleum compounds, as well as tidal, wave, wind, and thermal gradient energy. The ocean is a major contributor of valuable resources, including sand and gravel, salt and freshwater (from desalination), and polymetallic nodules mined from the seafloor. The ocean is a key resource for transport/travel, trade, and commerce, not to mention recreation, tourism, and valuable real estate. Coastal habitats protect people’s lives and structures from hurricanes and other storm winds and wave surges.

Despite the ocean’s tremendous importance to humans and other organisms, it largely remains a mystery. We know distressingly little about basic marine processes and even less about the topography and geology of deep-sea basins [2]. Although we have grasped that our existence depends on marine processes, we still have much to learn about marine ecosystems, their operation, and how they relate to life on land [5,8]. Research into basic marine science and oceanography—including geology, chemistry, physics, meteorology, microbiology, botany, and zoology—has never been more important, yet it continues to lag behind studies of terrestrial regions. In a slow but profound shift, however, this is beginning to change.

Any deep or notable transformation is often described by the term “sea change,” and this phrase perfectly captures what is happening at this moment regarding marine science: not just a monumental transformation in how we study the ocean but a profound and newfound awareness of why a clearer understanding of our ocean matters to everyone (and everything) on the planet.

As distressing as our longstanding ignorance of basic marine processes is, our dawning understanding of humanity’s increasingly harmful impact on the ocean and its biosphere is even more distressing. With the sea once seen as a limitless expanse, a boundless source of food, and an infinite dumping ground for trash and other waste, we now recognize our heavy anthropogenic influence on the sea. We realize that the sea’s pH has quickly become more acidic than in pre-industrial times [4], and that it has silently absorbed more than 90% of the climate’s excess heat generated chiefly by carbon emissions [4]. We know that noise pollution dramatically affects marine life, while plastic pollution, accumulating from an influx of roughly ten million metric tons of new plastic entering the ocean each year (89% of which involves single-use plastics), increasingly clogs seaways, imperils marine trophic webs, and clearly threatens human health [4,9].

In the face of so much ignorance and need, what can be done? Clearly, the first step is to learn much more about the ocean and its role in regulating Earth’s fundamental activities. From basic information to detailed knowledge, we need to know more. We need more research into marine science, at every level and from multiple funding sources. We need more education for and engagement by an informed global populace. We need to understand that we are all citizens of Planet Ocean and that the future of our world, and humanity’s future, hangs in the balance.

2. Overview of Special Issue

Arriving at this crucial time, this Special Issue, the Feature Papers of Oceans 2024, helps in filling many of the gaps in our understanding of marine science. At the same time, this Special Issue showcases a variety of research methodologies with high-quality, quantitative datasets. This collection of open access publications from leading researchers in marine science demonstrates some of the interdisciplinary ways that mathematical modeling, biodiversity exploration, and advances in engineering and technology continue to unlock some of the ocean’s mysteries.

At the same time, this collection features a wide array of topics that illustrate many of the key ways in which humans continue to influence the ocean for good and ill [10]. The ocean regions featured and discussed in these papers, including the Caribbean, Mediterranean, and Black Seas, are sites of tremendous human activity and hence anthropogenic impact. They offer test cases on how to study and alter ocean processes to aid all of Earth’s species, including our own.

The nine publications assembled here offer a broad-ranging introduction to current issues affecting marine science, including a trio of offerings each on oceanography, marine biology, and marine policy—along the way, each publication reveals how all three of these areas are intertwined.

The three papers collected in this Special Issue that involve oceanography demonstrate how ongoing marine research continues to reveal fundamental aspects of Earth science and meteorology. The paper by Pelegri et al. (contribution 1) on ocean mixing shows how perturbations from shear and flow instability derive from gradients of temperature, density, and other basic aspects of the ocean and atmosphere. The paper by Rudan and Sviličić (contribution 2) shows how physical experiments and wave modeling from computational fluid dynamics (CFD) inform our understanding of how breakwaters or other man-made barriers impact wind-induced waves to provide physical protection from storms, thereby saving beaches and homes from coastal erosion. The paper from Bisinicu and Lazar (contribution 3) straddles the boundaries between basic oceanographic research on how seawater quality (including nutrients and pollution) affects plankton biogeography, biodiversity, and biomass, with an awareness of how human environmental policies and other choices interact with seasonal changes and invasive species. These factors determine plankton species richness and marine distribution, both vertically and horizontally, in both shallow coastal and deep pelagic international waters.

The three papers collected in this Special Issue that focus on marine biology also demonstrate a variety of methods and study organisms, but all show that life persists along with, and often despite, stark human impacts [11]. The paper by Lucey et al. (contribution 4) shows how climate change and ocean acidification lead to mass mortality events of Caribbean corals from hypoxia and bleaching, but it confirms that coral populations can adapt their metabolic rates and show stress tolerance to hypoxia, offering hope for the restoration of damaged reefs. The paper by Lombardo and Marletta (contribution 5) on heterobranch gastropod mollusks (sea slugs) near a petrochemical hub in the Mediterranean reveals how marine biodiversity adapts to temperature and other essential factors of habitat, as well as to industrial pollution from human sources, showing that we share the ocean with diverse life that is generally resilient even in fragile, delicate ecosystems. Likewise, the paper by Ayala and Méndez-Tejada (contribution 6) shows not only how blooms of Sargassum macroalgae (seaweed) respond to sea surface temperatures, cloud cover, and solar radiation but also that these ocean factors are easily influenced by human activity, such as erosion from agricultural tilling practices in distant arid lands. This generates particulate deposition that affects human health on land just as it affects seaweed health in the sea, and Sargassum blooms in turn affect humans in multiple ways, such as by posing navigation hazards.

Finally, the three remaining papers focus primarily on human technologies and policies that both help and hinder our ability to understand care for the sea. The paper by Bassolillo et al. (contribution 7) concerns unmanned underwater vehicles (UUVs, or marine drones) and remotely operated underwater vehicles (ROUVs) for autonomous navigation for shipping and exploration, with algorithms from mother ships helping in the detection and planning of optimal routes for adaptive weather routing. The paper from Prieto et al. (contribution 8) considers government controls and international agreements of risk indicators of port inspections, maritime transport, and accidents at sea and how these factors together determine hazards and safety controls of ocean shipping and commerce. The paper by Henderson et al. (contribution 9) looks at the Cultural Heritage Framework Programme (CHFP) of the UN Decade of Ocean Science (2021–2030) and how it relates to such programs as the UNESCO SeaVoice and Blue Economy initiatives, offering Western and traditional/indigenous scientific and cultural education on such matters as marine protected areas (MPAs), marine archaeology, sustainable development, and general ocean literacy.

3. Conclusions

Each feature paper in this Special Issue stands alone as a valuable contribution to our ever-increasing body of knowledge about how the ocean operates and how these functions are affected by human impact. Taken together, these diverse research reports provide a testament to the essential value of conducting, analyzing, and communicating findings about our global ocean. Despite a striking variety of topics and methodologies, these interdisciplinary reports join a chorus to tell the same story: We live on Planet Ocean, and despite its resilience in the face of the many risks we pose to it [11], there are limits to this resilience [10].

New opportunities create new threats. The shipping of oil in huge tankers, which began in the late 19th century, helped carry valuable new fuel sources around the world relatively easily and inexpensively. Unfortunately, this also created entirely new hazards, such as coastal oil spills caused by these tankers sinking or running aground. Many of the most severe threats to whales and other marine life, including ship strikes, entanglement in nets or longlines, and bycatch in giant trawls or purse seines, did not become problematic until the 20th century, such that marine life has had little time to adapt to new threats. Other dangers posed to marine life, such as intense noise pollution from high-intensity SONAR and seismic testing, arrived even more recently [4,12]. The human use of the ocean has benefited our species, but often at the expense of other species and also, as we are increasingly learning, by posing threats to human health as well [9,13,14].

However, threats also present new opportunities. The climatic and health threats from fossil fuels have spurred tremendous innovation in renewable energy sources. These threats have also created urgency to innovate newer, more energy-efficient vessels and marine propulsion technologies. Overfishing has spurred newer, more sustainable harvesting and mariculture practices, not to mention key international agreements. This has led to the better management of marine resources and has created protected areas to preserve fragile habitats. Plastic pollution is driving innovation in biodegradable materials as well as ushering in new practices for packing and shipping goods. Climate change is leading scientists and futurists to consider bold advances in geoengineering. Most of all, these threats are driving major changes in education and awareness, so that there is hope for future generations of our world’s citizens and researchers.

We must continue to study the basic Earth and environmental science underlying the sea and its life forms and apply these lessons learned to protecting that life and changing how we interact with it. Our world is distinguished by a massive, ancient, and thriving ocean, but we can no longer deny our impacts on it, nor can we overlook its finite fragility. For the sake of our world and our human future, we must learn to live in harmony with, rather than merely near, the ocean. The fight continues, and the sea change accelerates. The editors of this journal, Oceans, hope to report additional important findings as feature papers in years to come.