09.07.2018- Descent into the deep

Many deep-diving species have been observed in the waters around the Madeiran archipelago, including the Sperm whales (Physeter macrocephalus), the Blainville’s beaked whales (Mesoplodon densirostris) and, the deepest diving mammals to our knowledge, the Cuvier’s beaked whales (Ziphius cavirostris). Visual input is virtually non-existent in the dark ocean where these animals forage and socialize which emphasises the importance of their ability to communicate and echolocate using their bioacoustics. But what do the depths around Madeira actually look like and what other lifeforms can one expect in this mysterious ecosystem?

Last Thursday afternoon researchers went on a mission coordinated by the Observatorio Oceanico da Madeira to answer such questions. The Luso ROV (remotely operated vehicle) went for its first dive; a 90 minute and 2000m descent into the abyss on the south of the island and was then moved along the bottom. The mission was conducted aboard the Portuguese Navy vessel Gago Coutinho which had just returned to Funchal the previous evening with researchers from the Selvagem Grande. The vessel was spotted during our morning tour on our zodiac, the Stenella. Apart from gaining a greater understanding of the physical features of the abyssal plains near the island, which include submarine canyons and valleys leading into the even deeper areas of the open ocean, the campaign aims to explore the biodiversity at these depths. The researchers discovered a great concentration of deep sea corals, which are partially a foundation for the complex ecosystems down below that thrive despite the absence of light. Moreover, these coral species are known to be important climatic indicators and boast a beautiful variety of shapes and colors.

While all this is exciting stuff, how is it important for cetaceans and what has it got to do with whale-watching? The topography of Madeira’s steep underwater plains determine when and where nutrients from the deep are transported to the upper layers of the water column through „upwelling“, fertilizing plankton at the ocean’s surface. This plankton, in turn, is the base of the oceanic food web and feeds the planktivorous fish preyed upon by dophins and baleen whales. Large deep diving cetaceans, such as Sperm whales, also appear closer to the coastline because of the steep underwater gradient and can care for their calves within the more sheltered waters of the island.

The more we understand about the topographic structure of the depths of Madeira and what lifeforms it contains, the more we can understand about such deep diving creatures and what implications human-induced problems, such as noise pollution may have for them and how they can be solved. Moreover, we will have a better idea of the world they spend the majority of their lifetime in. Apart from Sperm whales, our guests on board the tours today also enjoyed sightings with a variety of other cetacean species including Atlantic spotted dolphins (Stenella frontalis), Bottlenose dolphins (Tursiops truncatus) and Short-finned Pilot whales (Globicephala macrorhynchus). Apart from encounters with cetaceans, it’s equally rewarding to have sightings of such research vessels that have embarked on missions to enhance our understanding of the worlds oceans. After all, we are all explorers at heart.

For more information on the research projects conducted by the OOM visit their website (https://oom.arditi.pt) or their Facebook page (https://www.facebook.com/oom.arditi)

By Paula Thake

Sightings of the day

Ribeira Brava

09:00 Atlantic spotted dolphins, Bottlenose dolphins, Sperm whales

13:30 Atlantic spotted dolphins, Bottlenose dolphins, Short-finned pilot whales, Sperm whales

Stenella

12:00 Bottlenose dolphins, Short-finned pilot whales, Sperm whales

18:00 Bottlenose dolphins