The tropics experience significant changes in ocean surface temperature, often driven by phenomena like El Niño-Southern Oscillation (ENSO). These shifts in sea surface temperature have profound impacts on global weather patterns and marine ecosystems.

Thermohaline circulation (THC) refers to the large-scale, density-driven circulation of the global ocean. It is governed by differences in temperature (thermo) and salinity (haline), which affect the density of seawater, driving the movement of deep-ocean currents across the planet.

Sea turtles, particularly the leatherback species, have a diet that consists largely of jellyfish. Due to the visual similarity between translucent plastic bags drifting in the water column and jellyfish, sea turtles often ingest plastic debris, which can lead to intestinal blockages, malnutrition, and death.

A surface plume, often caused by oil spills or sediment discharge, creates a layer on the water's surface. This layer increases turbidity and reflects or absorbs sunlight, significantly reducing the amount of light that can penetrate into the deeper layers of the ocean, which negatively affects photosynthetic organisms.

Ocean dumping involves the deliberate disposal of waste materials into the sea. While historically practiced, it is now heavily regulated or banned by international treaties like the London Convention due to the severe environmental damage it causes to marine life and water quality.

Studies conducted in the early 2000s, specifically around 2004, highlighted the alarming accumulation of microplastics in marine environments. Researchers found that the mass of plastic debris in certain seawater samples significantly outweighed the biomass of plankton, which serves as the foundation of the marine food web, indicating severe ecological disruption.

Tritium, a radioactive isotope of hydrogen, is frequently used in oceanographic studies as a tracer. Because it is incorporated into water molecules, it acts as an excellent marker for tracking water mass movement, circulation patterns, and the dispersion of radioactive contaminants in the open ocean. Its presence helps scientists understand the long-term mixing and transport processes occurring within deep-sea environments.

Microplastics are pervasive pollutants in marine environments. They are frequently ingested by various aquatic organisms, including fishes, which mistake the small plastic particles for food. This ingestion leads to bioaccumulation within the food chain, posing significant risks to both marine life and human consumers who rely on seafood.

Marine ecosystems are highly sensitive to changes in acidity. When the pH level drops significantly, such as to 4.5, the resulting acidification can be lethal to many marine organisms. This acidity interferes with biological functions, such as calcification in corals and shellfish, leading to widespread mortality and ecosystem collapse.

Rivers act as major conduits for pollutants, including heavy metals, which are washed from the land through runoff and industrial discharge. These substances are eventually transported downstream and deposited into the oceans, which serve as the ultimate sink for most terrestrial waterborne contaminants.