Dave Grant: The “River in the Ocean”, March 2, 2012

NOAA Teacher at Sea
Dave Grant
Aboard NOAA Ship Ronald H. Brown
February 15 – March 5, 2012

Mission: Western Boundary Time Series
Geographical Area: Sub-Tropical Atlantic, off the Coast of the Bahamas
Date: March 2, 2012

Weather Data from the Bridge

Position: 26 degrees 19 minutes North Latitude & 79 degrees 55 minutes West Longitude
Windspeed: 14 knots
Wind Direction: South
Air Temperature: 25.4 deg C / 77.7 deg F
Water Temperature: 26.1 deg C / 79 deg F
Atm Pressure: 1014.7 mb
Water Depth: 242 m / 794 feet
Cloud Cover: none
Cloud Type: NA

“The moment one gives close attention to anything, even a blade of grass,
it becomes a mysterious, awesome, indescribably magnificent world in itself.”

Henry Miller

My evenings looking through the microscope are a short course in invertebrate zoology. Every drop of water filtered through the plankton net reveals new and mystifying creatures. Perhaps 90% of marine invertebrates, like newly hatched mollusks and crustaceans, spend part of their life in a drifting stage – meroplankton; as opposed to holoplankton – organisms that are planktonic throughout their life cycle.

MOLLUSK LARVAE

Bivalve

Bivalve

 Univalve

Univalve

The lucky individuals that escape being eaten, and are near a suitable substrate at the right moment, settle out into a sedentary life far from their place of origin. For the long distance travelers swept up in the Gulf Stream, the most fortunate waifs of the sea that survive long enough might make it all the way to Bermuda. The only hope for the remainder is to attach to a piece of flotsam or jetsam, or an unnatural and unlikely refuge like the electronic picket fence of moorings the Ron Brown is servicing east of the Bahamas.

“The gaudy, babbling, and remorseful day,
Is crept into the bosom of the sea.”
Shakespeare

A league and a half* of cable, sensors and a ton of anchor chain are wrestled on deck during a day-long operation in the tropical heat. (*A mariner’s league equals three nautical miles or 3041 fathoms [18,246 feet])

It is easy to be humbled by the immensity of the sea and the scope of the mooring project while observing miles of cable and buoys stretched towards the horizon, about to be set in place with a ton of anchor chain gingerly swung off the stern for its half-hour trip to the bosom of the sea.

Thanks to the hard labor and alert eyes of our British and French (“And Irish”) colleagues retrieving and deploying the attached temperature and salinity sensors, I am regularly directed to investigate “something crawling out of the gear” or to photograph bite marks from deep sea denizens on very expensive, but sturdy equipment.

A retrieved sensor with bite marks.

A retrieved sensor with bite marks.

To my surprise, other than teeth marks, very little evidence of marine life is present on the miles of lines and devices strung deeper than about 200 meters. This may be due in part to the materials of which they are constructed and protective coatings to prevent bio-fouling, but sunlight or more precisely, the attenuation of it as one goes deeper, is probably the most important factor.

Fireworm (Drawings and images by Dave Grant - NOAA Ron Brown)

Fireworm
(Drawings and images by Dave Grant – NOAA Ron Brown)

Handle with care! Close-up of worm spines

Handle with care! Close-up of worm spines

The first discovery I was directed to was a striking red bristle worm wiggling out of the crevice in a buoy.  It appears to be one of the reef-dwelling Amphinomids – the aptly-named fireworms that SCUBA divers in the Caribbean avoid because of their venomous spines; so I was cautious when handling it.  This proved to be the deepest-dwelling organism we found, along with some minute growths of stony and soft corals.

Five o’clock shadow” on a buoy – A year’s growth of fouling organisms – only an inch tall.

On shallower buoys and equipment, there are sparse growths of brown and blue-green algae, small numbers of goose barnacles, tiny coiled limey tubes of Serpulid worms like the Spirobis found on the floating gulfweed, some non-descript bivalves (Anomia?) covered with other fouling growth, skeleton shrimp creeping like inch-worms, and of course the ubiquitous Bryozoans. Searching through this depauperate community not as challenging as the plankton samples, but not surprising since our distance from land, reefs or upwelling areas – and especially clear water and lack of seabirds and fishes; are all indicators that this is a nutrient-deficient, less productive part of the ocean.

   

Bio-fouling – “on the half-shell.”                       Skeleton shrimp (Caprellidae)

The Ron Brown is the largest workhorse in the NOAA fleet and its labs and decks are intentionally cleared of equipment between cruises so that visiting scientists can bring aboard their own gear that is best suited to their specific project needs. NOAA’s physical oceanographers from Miami arrived with a truckload of crates holding Niskin water sampling bottles for the CTD and their chemistry equipment for DO (Dissolved Oxygen) and salinity measurements; and in a large shipping container (“Ship-tainer”) from England, the British and French (“and Irish”) scientists transported their own remote sensing gear, buoys, and (quite literally) tons of massive chain and cables to anchor their moorings. (I am surprised to learn from the “Brits” that the heavy chain is shipped all the way from England because it is increasingly hard to acquire. )

In the lab: Scores of sensors serviced and ready for deployment

In the lab: Scores of sensors serviced and ready for deployment

This is how most science is facilitated on the Brown and it requires many months of planning and pre-positioning of materials. I am lucky and can travel light – and with little advanced preparation. I am using simple methods to obtain plankton samples and images via a small portable microscope, digital camera and plankton net which I can cram into my backpack for any trips that involve large bodies of water. The little Swift* scope has three lens (4x, 10x, 40x) with a 10x ocular, and I get great resolution at 40x, and can get decent resolution to 100x. Using tips from Dave Bulloch (Handbook for the Marine Naturalist) I am able to push that somewhat with a simple Nikon Coolpix* point-and-shoot camera – but lose some of the sharpness with digital zoom.  As you might suspect, the ship’s movement and engine vibration can be a challenge when peering through the scope, but is satisfactory for some preliminary identification. (*These are not commercial endorsements, but I can be bought if either company is willing to fund my next cruise!)

PHYTOPLANKTON

Centric diatom - Coscinodiscus

Centric diatom – Coscinodiscus

    

Dinoflagellates –  Different Ceratium species

ZOOPLANKTON

A Plankton précis

Collecting specimens would be much more difficult without the cooperation of the Brown’s crew and visiting scientists, and their assistance is always reliable and appreciated. The least effective method of collection has been by filtering the deep, cold bottom water brought up in the Niskin bottles. As mentioned earlier, no live specimens were recovered; only fragments of diatom and Silicoflagellate skeletons surviving the slow drift to the bottom, which I have been able to identify through deep sea core images posted at the Consortium for Ocean Leadership website.

Needless to say, the most indiscriminate method of collection and the most material collected is through the large neuston net. The greatest biomass observed on the trip is the millions of tons of Sargassum weed, which covers the surface in great slacks around us that are even visible in satellite images.

Although the continuous flow of ocean water pumped into the wet lab and through my plankton net is effective and the most convenient collection method, the most surprising finds are from the saltwater intake screens that the engineer directed me to. This includes bizarre crystal-clear, inch-long, and paper-thin Phylosoma – larvae of tropical lobsters – that I initially mistook for pieces of plastic.

Inch-long Phylosoma larvae on a glass slide. (One of the tropical lobsters.)

Inch-long Phylosoma larvae on a glass slide. (One of the tropical lobsters.)

“All the ingenious men, and all the scientific men, and all the fanciful men in the world …
…could never invent anything so curious and so ridiculous, as a lobster.”

Charles Kingsley -The Water-Babies

Plankton communities are noticeably different between the Gulf Stream, inshore, and offshore in the pelagic waters east of the Bahamas.  Near the coast, either the shallower Bahama Banks or the neritic waters over the continental shelf closer to Charleston, the plankton is larger, more familiar to me and less challenging to sort, including: copepods, mollusk larvae and diatoms. Steaming over the shelf waters at night, the ship’s wake is often phosphorescent, and dinoflagellates, including the “night-light” Noctiluca are common in those samples.

Dinoflagellate - Noctiluca

Dinoflagellate – Noctiluca

 The waters east of the Bahamas along the transect line are notable for their zooplankton, including great numbers and varieties of Foraminifera, and some striking amphipod shrimp. Compared to cooler waters I am familiar with, subtropical waters here have over a dozen species of Forams, and some astonishingly colorful shrimp that come up nightly from deeper water.

It’s not all work and no play on the Ron Brown, and there are entertaining moments like decorating foam cups with school logos to send down with the CTD to document the extreme pressure at the bottom. Brought back to class, these graphically illustrate to younger students the challenges of deep sea research.

Foam cup:  Before-and-after a trip to 5,000 meters

Foam cup: Before-and-after a trip to 5,000 meters

Navigating by Dead-reckoning

On calm days while we are being held on-station by the Brown’s powerful thrusters, I can measure current speeds using Sargassum clumps as Dutchman’s logs as they drift by. Long before modern navigation devices, sailors would have to use dead-reckoning techniques to estimate their progress.  One method used a float attached to a measured spool of knotted line (A log-line), trailing behind the moving vessel. The navigator counted the number of knots that passed through his hands as the line played out behind the ship to estimate the vessel’s speed (in knots). Since nothing is to be tossed off the Brown, I rely on a simpler method by following the progress of the Sargassum as it drifts by stem-to-stern while we are stationary at our sampling site. Since I know the length of the Brown at the waterline (~100-meters), I can estimate current speed by observing drifting Sargassum.

Watching sargassum, I wonder if a swimmer could keep pace with the currents in these waters. When in college
my brothers and would strive to cover a 100-meter race by swimming it in under a minute. Here is the data from east of the Bahamas. See if you can determine the current speed there and if a good swimmer could keep pace.

ESTIMATING CURRENT SPEED

Data on currents:
Average of three measurements of Sargassum drifting  the length of the Ron Brown = 245 seconds.
Length of the Ron Brown – 100-meters.

1. How many meters per second is the current east of the Bahamas?
2. As a swimmer in college – with my best time in the 100-meters freestyle of one minute – could I have kept up with the Ron Brown… or been swept away towards the Bahamas?

For more on currents, visit my site at the college:
http://ux.brookdalecc.edu/staff/sandyhook/Student%20Page%201/TUTS-2-09-1/Index.html

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Other navigational exercises I try to include determining Latitude and Longitude. Latitude is easy as long as you can shoot the sun at midday or find the altitude of Polaris in the night sky; and sailors have done that for centuries. The ship’s navigator will get out the sextant for this, or, since the width of one’s fist is about 10-degrees of sky, I can estimate the height of both of these navigational beacons by counting the number of fists between the star and the horizon.

ESTIMATING LATITUDE

Data:
Night observation (Shooting the North Star) – Number of Fists from the Northern horizon to Polaris = 3
Day observation (Shooting the Sun) – Number of Fists from the Southern horizon to the Sun = 5.5

If the width of a fist is equal to about 10-degrees of horizon, our estimate of Latitude using Polaris is 30-degrees (3 x 10).
Not too bad an estimate on a rocking ship at night, compared to our actual location (See Data from the Bridge at the top.).

Shooting the Sun at its Zenith at 12:30 that day gives us its altitude as 55-degrees – which seems too high unless we consider the earth’s tilt (23.5-degrees). So if we deduct that (55 – 23.5) we get 31.5, which is closer to our actual position. And if we consult an Almanac, we know that the sun is still about six degrees below the Equator on its seasonal trip North; so by deducting that (31.5 – 6) we end up with an estimate of 25.5-degrees. This is an even better estimate of our Latitude.

Here is the dreaded word problem:

By shooting the Sun, our best estimate of Latitude is 25.5 degrees (25 degrees/30 minutes)
The actual Latitude of the ship using GPS is 26-degrees/19 minutes.
If there are 60 minutes to a degree of Latitude – each of those minutes representing a Nautical Mile – how many Nautical Miles off course does our estimate place us on the featureless sea?

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Longitude is much harder to determine if you don’t have an accurate timepiece to compare local time with universal time (The time at Greenwich, England), and an accurate ship’s chronometer wasn’t in use until the mid-1700’s.
To understand the challenge of designing a precise timepiece that reliably will function at sea, I used two crucial clock mechanisms:  a pendulum and a spring. Finding a spring was easy, since “Doc” had a scale at Sick Bay. For the pendulum I fashioned a small weight swinging on a string)

Using the scale to observe the ship’s motion.

Using the scale to observe the ship’s motion.

Standing on the scale and swinging the pendulum even in calm weather quickly demonstrated three things:

First: I have developed my sea legs, and no longer notice the regular motion of the ship.
Second: Even when the sea feels calm, the scale’s spring mechanism swings back and forth under my weight; adding and deducting 20 pounds to my real weight and reflecting the ship’s rocking that I no longer notice.
Three: On rough days, even if I can hold still, the ship’s heaving, pitching and rolling alters my pendulum’s reliable swing – its movements reflecting the ship’s indicator in the lab. Experimenting helps me appreciate clock-maker John Harrison, and his massive, 65-pound No. 1 Ship’s Chronometer  he presented to the Royal Navy in 1728.

Ship movement as recorded by the computer

Ship movement as recorded by the computer

Doc: Always on duty -  Sick Bay on the Ron Brown

Doc: Always on duty – Sick Bay on the Ron Brown

Besides having very well-provisioned Sick Bays, NOAA ships have experienced and very competent medical officers.  Our “Doc” received his training at Yale, and served as a medic during the Gulf War.

Especially alert to anyone who exhibits even the mildest symptoms of sea-sickness, Christian is available 24-hours for emergencies – and in spite of the crew constantly wrestling with heavy equipment on a rocking deck, we’ve only experienced a few minor bumps and bruises. He has regular office hours every day, and is constantly on the move around the ship when not on duty there.

Besides keeping us healthy, he helps keep the ship humming by testing the drinking water supply (The Brown desalinates seawater when underway, but takes on local water while in port); surveys all departments for safety issues; and with the Captain, has the final word if-or-when a cruise is to be terminated if there is a medical emergency.

Since a storm pounding the Midwest will head out to sea and cross our path when we head north to Charleston, he is reminding everyone that remedies for sea sickness are always available at his office door, and thanks to NASA and the space program, if the motion sickness pills don’t work, he has available stronger medicine. So far we have been blessed with relatively calm weather and a resilient crew.

                          The warm  (Red) Gulf Stream waters viewed from a satellite iamge.

The warm (Red) Gulf Stream waters viewed from a satellite image.

 Contact: The edge of the Gulf Stream - Matthew Maury’s  River in the Ocean

Contact: The edge of the Gulf Stream – Matthew Maury’s River in the Ocean

Birdwatching on the Ron Brown

For the time being I take advantage of the calm seas to scrutinize what’s under the microscope, and when on break, look for seabirds. East of the Bahamas, as anticipated after consulting ornithologist Poul Jespersen’s map of Atlantic bird sightings, I only spotted two birds over a two-week stretch at sea (storm petrels). This is very much in contrast to the dozens of species and hundreds of seabirds spotted in the rich waters of the Humboldt Current off of Chile , where I joined the Brown in 2008.
(http://ux.brookdalecc.edu/staff/Web%2012-2-04/seabirds/Brown%20terns%202/Terns%20%20fixed/SEPacific.html)

Passing through Bahamian waters was no more rewarding, but now that we are west and in the Florida Straits there are several species of gulls during the day, and at night more storm petrels startled by the ship’s lights. One windy night a large disoriented bird (Shearwater?) suddenly fluttered out of the dark and brushed my head before bumping a deck light and careening back out into the darkness. Throughout the day a cohort of terns has taken up watch on the forward mast of the Brown and noisily, they juggle for the best positions at the bow – resting until the ship flushes a school of flying fishes, and then swooping down across the water trying and snatch one in mid-air.  Like most fishermen, they are successful only about 10% of the time.

Royal tern "on station" at the jack mast.

Caspian tern “on station” at the jack mast.

Royal tern "on station" at the jack mast.

Royal tern “on station” at the jack mast.

  

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Despite the dreary forecast from the Captain, Wes and I are enthusiastic about all we have done on the cruise and formulated a list of why NOAA’s Teacher At Sea program is so rewarding.

Top Ten Reasons:
Why be a Teacher At Sea?

10. Fun and excitement exploring the oceans!

9. Meeting dedicated and diligent scientists and crew from around the world!

8. Bragging rights in the Teachers’ Room – and endless anecdotes!

7. Cool NOAA t-shirts, pins and hats from the Ship’s Store!

6. Great meals, three times a day…and FREE laundry!

5. Amazing sunsets, sunrises and star-watches!

4. Reporting on BIG science to students…and in real-time!

3. Outstanding and relevant knowledge brought back to students and colleagues!

2. First-hand experience that relates to your students’ career objectives!

1. Rewarding hours in the lab and fieldremembering why you love science and sharing it with students!

Powerpoint:
Shots from the deck and under the microscope

(Drawings and images by Dave Grant – NOAA Ron Brown)