The penultimate episode in our Blue Planet II series takes us to the coast, where land and sea collide. In this episode, we meet creatures who alternate between these two very different domains, and learn how they adapt to survive in this ever-changing environment. What are some of the most notable aspects of this bridge between two worlds?
Tide pools on rocky shores provide a refuge to many marine organisms, including those that prefer continuous submersion. As tides recede along these coasts, rock depressions and crevices remain filled with water and samples of ocean creatures.
Fur seals and sea lions (Carnivora: Otariidae) evolved in the North Pacific and later dispersed throughout the Southern Hemisphere. However, the timing and number of dispersals into the Southern Hemisphere remains poorly understood. Research indicates that the distribution of these mammals is tightly linked to sea surface temperature and productivity, and suggests that otariids may be vulnerable to future anthropogenic climate change.
Newly-weaned Southern elephant seal (Mirounga leonine) pups must strike a balance between conserving energy during their post-weaning fast and simultaneously developing diving abilities to become independent. Research suggests that temperamental weather, such as increased westerly winds and erratic storms, can have a detrimental impact on the pups’ cardiorespiratory activity.
The common octopus (Octopus vulgaris) has one of the richest motor repertoires of all animals, enabling them to complete a range of complex tasks, such as using their siphon to emit a jet of water to deter intruders, or to remove sand from a shell to make it easier to carry. They also use their arms to open large clams, and have been known to remove the lids of their aquariums to escape!
Mussels are the most important aquaculture species in Europe (based on live weight). Blue mussels (Mytilus) are usually considered a robust species, resistant to disease. Since 2010, however, abnormal mortality events have occurred in farmed blue mussels in France, with scientists hypothesizing that water-borne pathogenic bacteria are being passed from wild blue mussel parents to their larvae, especially under hatchery conditions.
Rock crabs, green crabs, and grapsid crabs live in rock pools, which may be subject to periods of low oxygen. When oxygen is low, they can increase the water flow over their gills to get more oxygen.
The Atlantic puffin (Fratercula arctica) is a migratory seabird, and research suggests that they visit a range of overwintering destinations, resulting in a range of migratory routes, with different energy expenditures. However, it appears that puffins tend to stick to the same timings and locations for major movements.
King Penguins dive during day and night-time. During daytime, they reach depths of between 100 m and 300 m in 1–4 minutes, and at these depths light levels fall to within the nocturnal range. Therefore, the birds are, from a sensory perspective, nocturnal foragers at all times: either they forage at night at relatively shallow depths (30–40 m) or they forage during the day at night-time light levels at greater depths.
Images: 1) Tide pool by PamperedwithNature. 2) Sea lion by Gellinger. 3) Mussels by stux. 4) Atlantic puffin by Free-Photos. 5) King penguin by Pixel-mixer.