The Mysterious Mid-Atlantic
Vol.7. 27th June 2017
Marguerite Tarzia explores the mysteries of the mid-Atlantic.
The mid-Atlantic is an enigma; it’s proving elusive for us to count the whales, to catch birds, to document the oceanography in space and time, and to understand what brings the wildlife out here.
The Big Blue
In our early easterly transects, we encountered quite high numbers of birds – Great Shearwaters, Fulmars, Leach’s storm petrel – and whales. We steamed into the Charlie-Gibbs Fracture Zone MPA (Marine Protected Area; see OSPAR commission), crossing the sub-polar front and in the chilly water we were suddenly surrounded by whales, including Humpback whales, Fin whales, Sperm whales and Sei whales and – incredibly – some Blue whales. The North Atlantic population of Blue Whales are still struggling to bounce back after commercial whaling, so it we all felt extremely lucky to be seeing these animals here (we’ve seen 5 so far!).
On our busiest day we had close to 60 different sightings, making for extremely busy shifts. Surprisingly to the team, many of the large whales (and we are talking about some of the largest animals to have ever lived on the planet), have barely showed themselves above the water. Without seeing their body, it is not possible to conclusively identify the animal, as you are essentially just seeing their exhalation (their blow) and nothing more. These animals therefore seem to embody the mood of this part of the ocean: elusiveness.
Blow from a Blue whale © Marguerite Tarzia
Still waters run deep
After our busy sighting days, the weather kept improving, with some amazing sunsets topped off with Pilot whales circling the vessel and feeding Fin whales lunging at prey close to the boat. At certain points the large whales were replaced by pods of dolphins, including Striped and Common Dolphins, with Great Shearwaters and Cory’s Shearwaters circling closely. As we headed further down our second transect, we were allowed a brief window of beautiful weather, with sunshine and gently rippling water. We could have been in an enclosed bay rather than the open ocean.
Striped dolphins © Marguerite Tarzia
As Julie Miller described in her blog post, this was prime time for testing the Fast Rescue Boat, in preparation for catching birds on the calm days to come (so far no luck on that front) and the mist-netting at night to catch Leach’s storm petrels (much luck, many birds caught.
Rescue boat deployed for bird-catching © Marguerite Tarzia
Is there anything out there?
Then the weather changed. It is hard to imagine that it is in fact the same ocean, the same place, as in those sunny days. We have had over a week of mostly grey, foggy and rainy weather. The weather has definitely added atmosphere, and the ocean has been very beautiful in these foggy, muted light conditions, however it has made spotting birds and whales quite challenging. In fact, there have been many days when we have asked ‘is there anything out there at all?’ as the fog closed in around us, letting us see less than 50m ahead of us.
Calm and foggy seas © Marguerite Tarzia
The mid-Atlantic has been playing with us, with ever changing combinations of poor weather and poor visibility to hamper our attempts. On the monkey island, the cetacean team has been particularly affected by this, with fog and calm seas replaced by fog and rough seas, replaced by sleeting rain aimed at our eyeballs.
The cetacean team has doggedly continued to watch, and the bird catching team has continued to attempt catches, each day the technique is honed and improved and birds are regularly brought on board to be processed and diet sampled. There have been over twenty-four birds caught during this trip, with Northern Fulmars being the most regularly caught using the cast nets. Recently we have had catching evening with hundreds of Northern Fulmars sitting on the ‘chummed’ water, paddling their feet in a desperate dance away from Ewan Wakefield’s net.
Releasing a Leachs' storm-petrel © Marguerite Tarzia
End in sight
We are currently on our fifth transect line, close to Canadian waters and heading south. Before getting to this line we diverted to an area of high chlorophyll (planktonic plants at the base of the marine food chain) which we thought would have many birds and whales associated with it. After steaming all day through fog and apparently empty seas we gave up and headed back to the track line.
Now, having left the cold water north of the sub-polar front, the water and the air is much warmer now, and different bird species are starting to show up (Bulwer’s Petrel today!). We are hoping that the predicted bad weather will stay away and that we can continue to survey and catch birds during our last week on board. We hope that the mid-Atlantic will allow us a few more insights into its enigmatic character before we have to leave. Many more guest blogs will be up this week and I will write again before we arrive in port on 2 July.
Follow the RSS Discovery's position on the National Oceanography Centre's 'Vessel Tracker'.