Its crazy chaos out there!
Hold on tight Salty Sea Dogs
The wind is blowing at about 8 knots, and although the ocean swells are not huge, the time period between the swells is very short. So, even though it is not super windy, the sea is a little choppy because the swells are so close together.
The Salty Sea Dogs really have to watch their footing, and Monique and Chris keep a close eye on them.
The 200 meter contour line – Hmm, I wonder what that is?
Our intended destination today is where the ocean is about 200 meters deep.
The waters off Cape Town are close to the continental shelf of Africa, and as we go further out to sea, the sea gets deeper and deeper.
It gets deeper in stages, and when the depth stays the same for a little while, this is called a contour line. Contour lines are very helpful as they help us to understand what it looks like on the bottom of the sea.
The lines on this map show the contour lines with the depth measured in meters off Cape Town.
Understanding the contour lines helps us to spot wildlife ~ who would have thought!
Ocean currents are rich in nutrients that are food for baitfish, such as sardines and anchovies. We know that sardines and anchovies feed many species in the ecosystem including gamefish, seals, sharks, dolphins and sea birds.
When the ocean current pushes up against a contour line, it helps to keep the nutrients in a focused area. When the water is rich in nutrients, it means we have a good chance of spotting a big variety of marine wildlife
There’s a lot going on at 200 meters!
As we get closer to the 200-meter depth, Chris looks into the distance. He has excellent eyesight and loves to spot things at sea!
Up ahead there looks to be thousands and thousands of birds working over an area.
As we get closer Monique starts to identify the birds: White-chin petrels, Cape gannets, Sooty and Cory shearwaters, and even the tiny Wilson’s storm petrel.
It is crazy with activity as the shearwaters bob on the surface before diving down below, the white-chins soar around, and the gannets plunge into the water from high above.
As we get closer Brownie begins to whimper with excitement, Sandi starts to yelp, and Lucy trembles with anticipation.
What have they spotted?
Mixed in with the craziness of the thousands of birds, the surface of the ocean bubbles with spray and turbulence. A huge school of about 800 Dusky dolphins is also here, and they are joining in on the feeding event!
The noise is tremendous … gannets are squawking, shearwaters are squeaking, dolphins are splashing, and as the wind begins to pick up, we can hear this too.
The Salty Sea Dogs look all around. It is just incredible with the activity stretching over 2 kilometers.
Soon, a number of Dusky dolphins approach our boat for a closer look. Brownie and Lucy lean over for a closer look. What a view they get!
Paws for thought – a Contour line wrap up!
By going to the 200 meter contour line we hoped we would find a concentration of wildlife, and we did!
This is a great example of how the non-living parts of this ecosystem helped to create perfect feeding conditions for the living parts of the ecosystem.
In this case, the non-living parts are the ocean current and the contour line; and the living parts are the baitfish, various sea birds and dusky dolphins.
Curious to find out more? Check out ‘What is an ecosystem’ in Fact Finder.
A Dusky Goodbye
As we begin the long journey back to the harbour, a couple of Dusky dolphins leap with joy and say goodbye, sending The Salty Sea Dogs on their way back home!
Until the next time,
Big woofs from the Waves to you all!
