sail-world.com
 
 
News Home Photo Gallery Cruising Australia Cruising USA Cruising Canada Boats for Sale Sail-World Racing FishingBoating
Video Gallery Newsletters
Sail-World.com : Where the whales are
Where the whales are

'Whales fast food joint - the Great South Channel'    .

There are patches in the ocean where right whales congregate to feed. Nobody knows how these patches form. But understanding why they do would certainly help design policies to conserve marine animals - and perhaps help cruising sailors to avoid contact. Nicholas Woods, in this Oceans Watch Essay, here describes an expedition into an Atlantic Ocean patch, located in the 'Great South Channel':

When people are hungry, they go to a place where they know they can find their favorite food. Right whales do much the same thing.

Where the whales are -  .. .  

In the Great South Channel, a deep-water passage between Nantucket and Georges Bank in the western Atlantic Ocean, thick swarms of tiny marine organisms known as copepods appear every spring. Basking sharks, cod, haddock, and endangered North Atlantic right whales all feast upon these dense patches. In a way, the Great South Channel is like the right whales’ favorite restaurant, and they keep coming back every year.

Nobody knows how these patches form. But understanding why they do would certainly help policymakers design marine protected areas and fisheries regulations to help conserve marine animals. This is why we are at sea aboard the research vessel Tioga at the crack of dawn. Our team from the Autonomous Systems Laboratory at Woods Hole Oceanographic Institution (WHOI) is helping to untangle the combination of physical and biological processes that form these dense copepod patches.

Above the steady drone of the engines, a loud 'beep' penetrates the air on the bridge. The tone indicates that we are close to an underwater glider that has been surveying the area for the past two weeks. It’s 8 a.m. on a Saturday morning in mid-May, and everyone is in position to recover the glider.

Whales underwater glider being launched -  .. .  

Back ashore in the lab, Dave Fratantoni, a WHOI physical oceanographer and my Ph.D. advisor, checks the glider’s most recent position and relays the information to the rest of us in the field. Captain Ken Houlter, at the helm, guides the ship toward the waypoint. Ian Hanley, the first mate, rigs the deck for recovery. I huddle over a computer with Ben Hodges, our lab’s research assistant, reading the data stream that accompanies the tone, trying to discern the range and bearing to the vehicle. We relay the information to Houlter, who alters course accordingly. Then we begin to scan the horizon for the glider’s little yellow tail, a flag smaller than a sheet of paper marking not only the location of the vehicle but also a new piece to the puzzle of plankton patchiness.

At the mercy of currents:
Scientists have known for many years that right whales and other predators feed on copepods in the Great South Channel, but what makes this place so special remains a mystery. In fact, biologists don’t know how whales even find these dense patches. Past research has suggested that the physical environment—the currents, tides, and possibly the bathymetry of the ocean floor—might play roles in creating these important feeding areas. However, no one has yet identified the specific mechanisms—physical, biological, or a combination—by which dense copepod patches form.

The waters of the Great South Channel are extremely dynamic. A fairly steady coastal current flows south along the east coast of Cape Cod’s forearm and into the Great South Channel. When it reaches the channel, some of this coastal current flows south around Nantucket Shoals, while another part turns toward the east and joins the northeastward flow along the northern flank of Georges Bank.

Whales feeding patch in the Atlantic -  .. .  

To the south, part of another current, flowing southwestward along the southern flank of Georges Bank, turns north into the Great South Channel.

On top of all this, strong currents driven by winds and tides are also flowing. At any given moment, these may be twice as fast as the steady currents. The copepods are at the whim of these complex flow patterns. To determine where the copepods will go, we must understand the flows that move them around.

A multipronged approach:
The complex nature of the currents in the Great South Channel demands that we employ a variety of different techniques and tools to study the ocean circulation. Each is better suited for studying some aspects of the physical oceanography than others; combining methods allows us to understand more of the picture than any one method alone.

Research ships serve as platforms from which we deploy our vehicles, but they also take useful measurements of the water near the surface, including temperature and salinity. Meteorological moorings provide data on wind speed and direction at locations around the Great South Channel. These data tell us how winds move the surface waters. In addition, satellite-tracked surface drifters deployed in the region throughout the past thirty years give us an idea of how the surface water flows.

Another useful tool is the autonomous underwater glider. These underwater robots 'fly' through the ocean by shifting their buoyancy, alternating between sinking and rising in the water. The wings on their sides provide lift, which allows them to glide for many days at a time.

They can fly under any weather conditions, including rough seas that would send an oceanographic vessel back to port. They collect temperature, salinity, and optical data that we can use to look for phytoplankton, which is fodder for copepods. They also can be equipped with acoustic instruments that can measure ocean velocity and look for copepods or listen for whales. The vehicle we are attempting to recover is one of these.

We know from our biologist colleagues that copepods enter the Great South Channel mainly via the coastal current that flows along the Cape Cod seashore and down into the channel. The glider we’re chasing has traveled back and forth across this coastal current four times in ten days. The coastal current is fresher than surrounding waters, which makes it easy to identify using the salinity sensor on the glider.

We are interested to see that each of the glider crossings displayed a different salinity pattern: During the first transect, the fresher water was confined to a small area on the western edge of the Great South Channel. During the next three crossings, however, the fresher water spread farther across the channel, and during the last crossing, the coastal current water was saltier. Changes in the coastal current may lead to changes in the supply of copepods it delivers to the Great South Channel, so we are trying to figure out what controls the coastal current.

Storms mix it all up:
One potential factor we are investigating is surface wind. Wind at the sea surface may partly determine how wide, fast, and deep the coastal current flows. As the wind blows over the surface, it pushes the current around, bringing it closer to the beach or farther offshore; or accelerating it into the Great South Channel or slowing it down; or making it deeper or shallower.

But the wind can also have other effects on the coastal current. If the wind blows hard enough, the current—and all the copepods within it—may get mixed up with surrounding seawater. The winds during strong nor’easter storms drastically affect the coastal current.

In 2005, a strong storm on Mother’s Day weekend did exactly that. Before the storm, a well-defined coastal current flowed near the surface, and lots of right whales were sighted in and around the Great South Channel. After the storm, however, the current had mixed vigorously with the water surrounding it, and right whales were not seen in the area.

We have data from both gliders and a research ship in Great South Channel before and after the storm. We also use a numerical model that incorporates all known physics about fluid flow to simulate the ocean’s circulation during the storm. Together, these help us piece together how the storm affected the shape of the current.

Ocean fronts:
If ocean currents can sweep copepods into the Great South Channel, other ocean motion may actually cause the organisms to cluster. Copepods typically cannot swim fast enough to overcome swift horizontal currents in the ocean, but vertical water motion is much slower, and copepods are able to swim up and down in the water. Past theoretical studies have suggested a mechanism by which the copepods’ swimming ability can combine with a certain pattern of currents to result in an aggregation of the animals.

Suppose there is a region in which the surface currents all horizontally converge on a spot. Unable to fight the horizontal motion, copepods would drift with the flow toward the spot. Since the water can’t pile up in that place, it would be forced to sink. The copepods in the area of these converging currents would all seek to stay near the surface (to feed on phytoplankton, for example). They would swim upward to buck this downward motion, and they would remain in this spot.

As more and more copepods drift to this location and stay there, the density of copepods would increase. This type of mechanism, if it were to occur in the real ocean, would create a hotspot for whales, birds, fish, and anything else that feeds upon copepods.

Just as the atmosphere contains boundaries between warm and cold air known as fronts, which determine weather, the ocean also has fronts between warm and cold or salty and fresh water. If the surface water converges at ocean fronts in the Great South Channel, we might expect to find copepods clustered there.

Complex processes such as these are not likely to be well-characterized by a single observational technique. Using our suite of methods, instruments, and vehicles, we are taking steps to answer important questions about how this critical ecosystem works. Since copepods are food for so many different animals, the factors affecting how and where they aggregate influence the overall health of the marine ecosystems they sustain. So our work will provide fundamental information that resource managers need to make decisions on regulating fisheries and designating marine protected areas.

This research was funded by the Coastal Ocean Institute at WHOI, the NOAA National Marine Fisheries Service Northeast Fisheries Science Center, and the Office of Naval Research Marine Mammals and Biology Program. It was an Ocean Watch Essay for Sailors for the Sea, written by Nick Woods


by Nicholas Woods

  

Click on the FB Like link to post this story to your FB wall

http://www.sail-world.com/index.cfm?nid=95738

7:10 AM Fri 6 Apr 2012GMT


Click here for printer friendly version
Click here to send us feedback or comments about this story.

Click for further information on
Environment and the ocean

Related News Stories:

19 Mar 2012  GreenBlue wants a report card
18 Mar 2012  Sailing ketch Irene - goodbye billionaires, hello cargo!
14 Mar 2012  Climate Change misconceptions and realities - an Ocean Watch Essay
06 Mar 2012  Gulf of Aden crossing and a pirate rendezvous - PlanetSolar
02 Mar 2012  New theory: Neanderthals were great sailors
11 Feb 2012  America pauses on E15 - study bill passes
03 Feb 2012  Whales, whales and more whales in Southern California
17 Jan 2012  Solar ship PlanetSolar takes security forces for Gulf of Aden crossing
15 Jan 2012  Adventure sailing and marine protection - OceansWatch's winning combo
14 Jan 2012  Whale Wars - Australian protesters transferred from Japanese whaler
MORE STORIES ...






Sail-World Cruising News - local and the World

Five rescued after writing giant SOS by Courier Mail/Sail-World Cruising,












Irish student turns a mobile phone into a VHF radio by Niall Murray, Irish Examiner/Sail-World,








'Sailing Adventures in Paradise' by Vincent Bossley by Noonsite Reviewer/Sail-World,












Springtime Greening: Boaters Tips for Earth Day by BoatUS Foundation/Sail-World Cruising,










British rescuers go for their own circumnavigation challenge by Derby Telegraph/Sail-World Cruising,


How sailors really do have a voice in the future of our oceans by Sandra Whitehouse, Sailors for the Sea,


Message-in-a-bottle record - 102 years by AFP/Sail-World Cruising,














Canadian solo sailor rescued north of Auckland by Sail-World Cruising round-up,






Dutchman's 'real' Noah's Ark benefits from film's success
Two separate remote baby rescues sure to raise questions
Dramatic MOB Pacific cold-water rescue - the personal account
Merchant Shipping Chalks Up Another Rescue - Tanker Saves Yacht Crew
RYA Competent Crew Skills – Second edition now available
Why ethanol and boats don’t mix + Video
Check this sailing gear more often during the season
Bluewater open boat weekend - if you are 'starboard' of the Atlantic
Laura Dekker honoured by OCC Award of Merit in New Zealand
Free online fuel spill course - how much do you know?
Smaller but plenty of space: The Nautitech Open 40
Product of the Week: Chafe guards save lines from friction
Government sneaks through the 'Affordable Boat Act'
Japan's Antarctic whaling program harpooned
Yacht of the Week: Kokomo III - and she could be yours
Life-shattering event sends 'rookie' couple sailing the world
Mysteries of the seas, happening right now - missing, sunk, foul play
Sail Norway and Russia this summer - your own boat, or charter
Sunshine4kids' 'Fleet of Hope' sets off again
3,200-year-old boat found in Croatian waters
Product of the Week: the LineGrabber   
Mediterranean Mooring - How to moor stern-to to a dock or quay   
Canadian storm bomb threat - sailors advised: get off the water!   
Carbon monoxide poisoning - is it possible on YOUR boat?   
Sailing family condemmed for taking 3-year-old on circumnavigation   
New contract-free plan for satellite communicator on your smart phone   
Yacht of the Week: The Dashew creation: no sails, but eco-friendly   
No laughing! Sailing mistakes I don't want to make   
Multihull Solutions Phuket 2014 Regatta - new sponsorship   
Destination: From Moscow Sea to the White Sea   
Land sailors of India on adventure across the Rann   
Jet stream gets fish in hot water   
Still no plans for e-Borders   
A Paint App to (almost) replace your marine store assistant   
Air warms but water slower - be careful, sailors, of hypothermia   
Volunteer Canadian rescue team homeless - any offers?   
Hilary Lister and Nashwa Al Kindi set a new trans-ocean record   
How to anchor and 'never utter a word'   
Non-pyrotechnic flares for my boat - Can I or can't I?   
Health benefits of sailing   


For this week's complete news stories select    Last 7 Days
   Search All News
For last month's complete news stories select    Last 30 Days
   Archive News







Sail-World.com  



















 
Our Advertisers are committed to our sport, please support them!
This site and its contents are © Copyright TetraMedia Pty. Ltd and/or the original author, photographer etc. All Rights Reserved.

Photographs are copyright by law. If you wish to use or buy a photograph you must contact the photographer directly (there is a hyperlink in most cases to their website, or do a Google search.) with your request.

Please do not contact Sail-World.com as we cannot give permission for use of other photographer’s images.

Only if the photographer named on the image is Sail-world.com, Powerboat-world.com, Marinebusiness-world.com or NZBoating-World.com.
Contact us .
Ph: +61 2 8006 1873 or complete our feedback form    Contact us .
   View our Privacy Policy.    [Go Home]     [  Banner Advertising Specification]    [Bot Archive ]

Customised news feeds -Marine Industry companies, Clubs and Associations have their own customised version of our news feed on their website.
Look_here_to_see_examples

X6XL VIR CRU NH