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Why Is Biodiversity Higher at the Bottom of the Ocean Than at Its Surface?

The world's oceans can support far greater biodiversity than landmasses. The oceans cover over 70 percent of the earth's surface, and are responsible for half of the planet's global primary production, according to the Plymouth Marine Sciences Partnership. Marwa Donia and Mark Hamann of Ohio State University say the oceans contain more than 300,000 documented plants and animal species and perhaps hundreds of thousands yet discovered. This biodiversity, however, is not evenly distributed in the oceans. Some areas have for more biodiversity than others and for a variety of reasons. According to MPA (Marine Protected Areas) News, the oceans seem to house various biodiversity "hotspots," with many near the bottom of the oceans.

Habitat Variety
- The bottom of the ocean offers greater varieties of habitats than near the surface. The food chain in the ocean consists mainly of larger animals feeding on smaller animals, down to the microscopic level. This means small animals need places to hide and predators need places to ambush prey to use the element of surprise. The surface of the ocean is open and offers little in way of escape for prey. Therefore, the majority of species in the ocean head to the depths where better habitat is abundant, often only hanging out near the surface during migratory periods. The bottom of the oceans consists of volcanic ranges, mountains, hydrothermal vents, coral reefs and cold seeps. All these options and others in the ocean depths help marine life to strive.
Food Sources
- Since habitat is better in the depths of the ocean, so is the food for most of the oceans predators, but that is not the only reason. One of the most unique forms of prevalent food found at the bottom of the ocean is large animal carcasses. These animal carcasses draw the ocean's dwellers both large and small to feed on the remains. Another unique food source found at the bottom of the ocean is known as marine snow. Marine snow consists of the decaying materials of animal and plants that fall to the ocean's floor. Marine snowflakes get bigger as they fall through the water and can grow several centimeters before hitting the ocean's floor weeks later. The continuous fall of marine snow contributes greatly to the biodiversity that strives at the ocean's depths.
Coastal Areas Are Important Too
- Coastal areas are important sites for nurseries and breeding grounds for many marine life species. The coastal area extends from the high-tide mark on land to the edge of the continental shelf and consists of shallow, nutrient-rich waters. As such, coastal areas tend to have far greater diversity than open areas of the oceans. Almost 75 percent of the fish that feed the world comes from coastal waters, while the coastal zone accounts for 90 percent of the ocean's marine species.
Coral Reefs Are Crucial
- When it comes to biodiversity, no single structure found in the oceans is more important than coral reefs. Vital to the ocean's ecosystem and designated a biodiversity hotspot, coral reefs form important habitats for marine life and capture a lot of marine snow, making them a nutrient-rich attraction and a great place for marine plants to strive.

Nature