Our guests often ask whether we’ve seen any changes amongst the cetacean populations in the past years due to issues like climate change affecting our ocean. The truth is; we do not know. The effects of climate change are known but the way they influence processes in the natural environment is extremely complex and usually happens in a series of changes which strongly affect the food web. These are known as trophic cascades; an event which affects one species will directly or indirectly affect another.
An example for the potential effect of trophic cascades could be applied to this mornings sightings. Today our team was able to encounter two species of dolphins, whose abundance in Madeira is (for now) considered seasonal. First, we met a group of Short-beaked common dolphins (Delphinus delphis), that were hunting Halfbeaks (Belone belone), a planktivorous fish that is highly affected by changes in currents. Extreme temperature changes could cause changes in surface currents, changing the availability of plankton for Halfbeaks which in turn will change their distribution creating a big challenge for their predators. Top-predators like dolphins regulate entire ecosystems, so their problems become a problem for all other organisms existing in those systems.
Apart from trophic effects, extreme weather events such as storms or heatwaves can also cause changes in distribution of even orientation of some animals. Between our sightings our team found yet another dead Atlantic puffin (Fratercula arctica). So far, around 60 of these birds were collected in the region this month with only a fraction surviving. This sad phenomenon of so many dead puffins, a bird very rarely encountered around Madeira, may largely be linked to climate change and scarcity of fish according to local scientists.
After the puffin the mood was elevated by a pod of curious Atlantic spotted dolphins (Stenella frontalis) that gleefully leapt towards our boat. While encountering this dolphin is always magical, so many frequent sightings in winter does leave us wondering whether our “summer dolphins” occurrence in Madeira may also be changing in this ever-changing ocean.
By Paula Thake
Sightings of the day
09:30 Atlantic spotted dolphins, Short-beaked common dolphins