Blue Whales Rely on Wind to Locate Food in Coastal Upwellings

Krill (Euphasiida) are small shrimp-like crustaceans forming the backbone of marine ecosystems despite individual size (1-2 cm). They form enormous swarm populations (10,000-60,000 individuals/m³) saturating oceans between 300-600 meters depth, collectively forming hundreds of millions to billions of tons of biomass. As omnivorous filter feeders, they consume phytoplankton and serve as critical links transferring energy from microscopic producers to macroscopic predators including fish, seabirds, squid, octopus, penguins, seals, and baleen whales. Their swarming behavior creates defensive advantages and attracts predator feeding frenzies. Beyond their role as prey, krill drive massive nutrient cycling: gills release ammonia and phosphate, dissolving exoskeletons release calcium, fluoride, phosphorus, and organic carbon, and fecal pellets provide iron, nitrogen, and phosphorus. Their swimming motion stirs these nutrients into seawater, feeding microbial communities they depend on. As keystone species, krill bridge microscopic and macroscopic food webs, making their conservation critical for ecosystem stability.

Krill are tiny (2-inch) pelagic crustaceans found worldwide that form massive swarms; they perform daily vertical migrations from deep waters to the surface at night to avoid predators and feed on phytoplankton, serving as a keystone species for whales, seals, squid, and birds, while also playing a crucial role in ocean nutrient cycling through their migrations and acting as a vital link in marine food webs.

Antarctic krill (Euphausia superba) serve as a keystone species in the Southern Ocean food web, consuming diatoms during summer blooms and serving as primary sustenance for penguins, seals, and whales traveling thousands of miles; despite being traditionally classified as plankton, recent research reveals krill as strong swimmers (necton) capable of swimming continuously for weeks, utilizing specialized pleopods for propulsion and periopods lined with filtering hairs to capture their microscopic phytoplankton prey.

Krill are small crustaceans (zooplankton) that perform daily vertical migrations of several hundred meters, feeding on phytoplankton at night and descending to avoid predators during the day; they are critically important as a primary food source for whales, fish, and seabirds, and play a vital role in carbon sequestration by transporting carbon from the surface to the deep ocean through their fecal pellets, making them essential for both marine food webs and global carbon cycling.

Antarctic krill are tiny translucent shrimp-like creatures about 2.5 inches long, weighing barely more than a gram. Despite their small size, they form massive swarms where a single cubic meter of water can contain tens of thousands of individuals. Krill feed on phytoplankton and become food for nearly everything larger, including whales, seals, penguins, fish, and seabirds. They are considered a keystone species because they form the foundation of the entire Southern Ocean food web. Scientists estimate there are more than 700 trillion adult krill alive in the Southern Ocean at any given moment. If you tried counting that number out loud, one number every single second without ever stopping to rest, it would take you well over 20 million years to reach the final count. Antarctic krill swarms can be so massive they are visible from space as enormous patches of discolored water. One documented swarm covered over 170 square miles of open ocean and stretched down more than 600 feet deep, containing an estimated 2 million tons of krill. This single swarm's weight would require lining up more than 160,000 school buses bumper to bumper stretching for hundreds of miles. The total combined weight of all Antarctic krill is estimated at 300-500 million tons, exceeding the combined weight of all 8 billion humans on Earth.

Ocean surface temperature decreases progressively from equatorial and tropical regions toward polar regions due to the latitudinal gradient in solar insolation. However, the warmest ocean surface temperatures occur in subtropical regions (25-35° North and South) rather than at the equator, because subtropical regions experience high pressure, which leads to absence of clouds, reduced evaporation, and direct solar penetration. Ocean currents modify surface temperature patterns by transporting heat. Warm ocean currents carry warm water from equatorial regions toward polar areas, creating positive temperature anomalies. Cold ocean currents bring cold water from polar regions toward equatorial areas, creating negative temperature anomalies. Major cities are often located on coastlines influenced by warm ocean currents (New York, Tokyo, Rio de Janeiro). Cold ocean currents contribute to desert formation by reducing evaporation, explaining the location of major deserts like Atacama, Namib, and Sahara.

This segment covers temperature anomalies and ocean current effects: (1) Temperature anomalies occur when points at same latitude have different temperatures due to elevation, ocean currents, and proximity to water bodies; (2) Ocean currents push isotherms - cold currents push toward equator, warm currents push toward poles; (3) When comparing east and west coasts of same continent, ocean currents are the primary factor causing temperature differences.

Sea surface temperature anomalies show deviations from normal ocean temperatures, where cold water (14-25 cm below normal in North Carolina's northern waters) sinks and warm water (16-21 cm above normal in Raleigh Bay and Wilmington) rises, with the Gulf Stream significantly influencing these temperature patterns along the East Coast.

Ocean currents redistribute heat around the planet, with western ocean currents being narrow and fast (like the Gulf Stream carrying warm water northward) while eastern currents are wider and slower (like the California Current carrying cold water southward); these currents create variations in sea surface temperature by moving warm or cold water across different regions, and surface currents flowing away from the equator can trigger upwelling, where cooler deep water rises to replace the surface water.

Sea surface temperature anomalies reveal global climate patterns and ocean current dynamics. The Drake Passage between Pacific and Atlantic oceans shows the most extreme temperature gradients, with cold water in the South Pacific and hot water in the South Atlantic. The Gulf Stream creates mixed cold and warm water patterns as it flows toward Iceland and Scotland. Anomalously warm water exists around New Zealand and the southern Indian Ocean, while cold water surrounds the China Coast and northern Indian Ocean. These patterns affect weather systems, marine ecosystems, and global climate regulation.

Baleen whales like the right whale filter feed by swimming with their mouth open to catch everything. The fin whale gulps huge amounts of water and squeezes it out through baleen plates. Basking sharks, larger than great white sharks, don't have baleen but have specially adapted gill rakers that filter out microscopic plankton. The whale shark, the largest fish in the world, has similar gill structures for filtering. In the pelagic environment where food is patchily distributed, predators like sharks use specific foraging strategies: they make long journeys in straight lines, then when they encounter food, they have meandering paths through that area until food is no longer encountered. This strategy allows them to efficiently search for and exploit patchy food resources.

There is a significant size discrepancy between prey and predators in ocean ecosystems. Krill are about 10 cm long while many predators are much larger and must consume prey one at a time. Research reveals that krill are obligate swarmers, spending their entire life cycle in closely spaced clusters. This creates extreme patchiness where some areas have absolutely no krill while others have thousands per cubic meter. Average concentration measurements are misleading because predators either find nothing or find abundant food depending on where they encounter prey. About 60-80% of predictive capability for predator locations comes from measures of prey distribution characteristics rather than biomass, meaning spatial patterns matter more than total food availability.

Ocean predators survive not by consuming average food concentrations but by exploiting small, concentrated patches of food-rich areas throughout the ocean; sonar technology reveals these biological hotspots where organisms aggregate, solving the apparent paradox that animals cannot survive on the average dilute food concentrations measured in the ocean.

Marine foraging involves searching coastal areas for edible sea creatures. Successful foraging requires understanding habitat structures like seaweed (rainbow rack) that provide camouflage for marine life. Foragers must identify edible species including lobsters, prawns, rocklings, and smelt. Seaweed creates complex underwater environments that support diverse marine life, making it both a challenge and opportunity for finding food. The forager demonstrates how to navigate through seaweed to locate and capture marine creatures.

The open ocean is the largest wilderness on Earth, with no roads, landmarks, or ground that remembers what has passed. For predators, the first challenge is not the attack but finding where the hunt can begin. Unlike land where hunters follow tracks and scent, the sea does not hold memory in the same way. Prey moves through current, light, depth, and fear, then disappears into water that quickly looks unchanged. A wrong direction costs energy and an opportunity missed by minutes may not return. The ocean leaves no tracks but gives signs—birds gathering above, fish rising too quickly, or schools tightening as pressure builds. These signs do not last, and the ocean demands both patience and urgency. Food is rarely spread evenly, so predators must conserve energy and wait for the right moment when prey concentrates. In shallow, clear water, a hunt can look simple—a predator sees prey, the prey reacts, and the chase begins. But most of the ocean is not that simple. Water hides distance, light fades with depth, and a school can disappear into blue space even when it is close. Sound travels through water with great reach—a splash, a call, or the movement of many fish can pass through the sea before anything appears in view. Dolphins use clicks that travel outward and return as echoes, revealing distance, shape, and movement. Orcas carry memory, which becomes powerful in a wilderness without permanent roads. Sharks read the ocean through another set of clues—a fish in trouble moves differently from a healthy one. Prey behavior is one of the strongest signs—a relaxed school moves with a steady rhythm, but when pressure builds, that rhythm changes. The prey survive by staying difficult to isolate, while predators succeed by forcing one fish, one mistake, one opening.