On land, it isn’t difficult to envision the gaps that physically separate groups of organisms and the habitats they live in. For example, a forest-dwelling animal may live in a patch of forest surrounded by meadows or urban areas it does not venture into. These habitat patches vary in size and may be connected by narrow zones of habitat, called wildlife corridors, which allow animals to move from patch to patch. This kind of connectivity enables animals to move in search of food, mates, living space, and more. When these routes are cut off, a group of animals may become isolated from the larger population.
It may not be as easy to see how this concept of habitat connectivity applies to the ocean, which may appear to the casual observer as an enormous, single body of water through which organisms can freely move. However, that view is deceptive, as we know that marine animals and plants are found in specific habitats and areas and that their distributions can range from whole ocean basins to small, isolated patches.
There can be many barriers to organism movement in the ocean such as currents, tides, and temperature or salinity changes in the water column and on the seafloor. In the ocean, layers of water sometimes move in different directions and originate from different places, such as waters around Antarctica and the Arctic. Imagine being a tiny coral larva, floating along the ocean currents — these differences may be key to where you end up settling, and whether you can survive there.
For species that are attached to the seafloor such as corals, the type of bottom (hard or soft) may also be an important factor in where animals end up living. Such habitats may be patchy in their distribution and in turn limit the places where a species may occur. A core question for studies of connectivity is what factors influence if and how deep-sea animals, such as tubeworms on hydrothermal vents, can travel among distinct patches of habitat.
Habitat connectivity is critical for maintaining healthy populations of organisms, as it promotes biological diversity through the exchange of genes (i.e., reproduction) and allows animals to respond in the face of environmental changes. Understanding the factors that connect various ocean habitats and thus influence the distribution of a species is important for predicting how these animals will respond to disruptions in the environment (e.g., oil spills) and developing plans to limit potential impacts.