Jessie Soder: Drag It Along, Dump It Out, Count ‘Em Up, August 14, 2011

NOAA Teacher at Sea
Jessie Soder
Aboard NOAA Ship Delaware II
August 8 – 19, 2011 

Mission: Atlantic Surfclam and Ocean Quahog Survey
Geographical Area of Cruise:  Northern Atlantic
Date: Wednesday, August 14, 2011 

Weather Data
Time:  16:00
Location:  41°47N, 67°47W
Air Temp:  18°C  (64°F)
Water Temp:  16.5°C  (62°F)
Wind Direction:  SE
Wind Speed:  6 knots
Sea Wave height:  0
Sea Swell:  0

Science and Technology Log

A fellow volunteer, Rebecca, and myself measuring clams

When I found out that the Teacher at Sea trip that I would be on was a clam survey, I thought, “Oh, clams.  I see those on the beach all the time.  No problem.”  I learned that the clams are collected using a hydraulic dredge.  I knew  that a dredge was something that you dragged along the bottom of the ocean.  That seemed simple enough.  Drag it along, dump it out, count ‘em up, and you’re done.

Quickly, I learned that this project is not that simple!  A few questions came to mind after we had done a couple of tows:  How many people are needed to conduct one tow for clams and quahogs? (operate the machinery, the ship, sort through a tow, collect the data, etc.)  How many different jobs are there during one tow?

Sorting through contents of a dredge

Those questions are hard to answer, and I don’t have a precise answer.  What I have learned is that it takes a lot of people and everyone that is involved has a job that is important.  I asked the Chief Scientist, Victor Nordahl, how many people he preferred to have on a science team per watch.   He told me that it is ideal to have six people dedicated to working on sorting the contents of the dredge, processing the catch, and collecting data per watch.  Additionally, he likes to have one “floater,” who can be available to help during each watch.  This seems like a lot of people, but, when there is a big catch this number of people makes the work much more manageable.  There are six people, including myself, on my watch.  Four of us are volunteers.

Each time the dredge is lowered, pulled along the ocean floor, and then brought back onto the ship it is called an “event.”  In my last post I included a video of the dredge being hauled up onto the deck of the ship after it had been pulled along the bottom.  An entire tow, or “event,” is no small feat!  During my watch Rick operates the machinery that raises and lowers the dredge.  (Don’t forget the dredge weighs 2500 pounds!)

There are also two people working on deck that assist him.  (You can see them in the video from my last post.  They are wearing hard hats and life vests.)  Additionally, an officer on the bridge needs to be operating and navigating the ship during the entire event.  There are specific times where they must speed up, slow down, and stop the ship during a tow.  They also have to make sure that the ship is in the correct location because there are planned locations for each tow.  Throughout the entire event the science team, deck crew, and the bridge crew communicate by radio.

Rick, in front of the controls he uses to lower and raise the dredge

As I said, this project is not simple!  To make it more complicated, equipment often breaks, or is damaged, which means that the deck crew and the science team have to stop and fix it. On this trip we have stopped to fix equipment several times.  Various parts of the dredge get bent and broken from rocks on the ocean floor.  Before the dredge is lowered, the bottom is scouted with a depth sounder to try to avoid really rough terrain.  On the screen of the depth sounder different substrates are shown in different colors.  For example sand is shown in green and rocks are shown in red.  We try to avoid a lot of rocks.  However, all the rocks cannot be avoided and sometimes we hit them!

Personal Log

Vic getting a hair cut

Before coming on this trip I was told that the work can be strenuous and, sure enough, it is.  Sometimes a tow brings up hundreds of pounds of rocks (with some clams mixed in!) that we need to sort through and, as you know, rocks are heavy!  The work is also a bit, well, gross.  We have to measure all the clams, whole and broken and we also have to collect weights of “clam meat.”  That means that we have to open the shells and scrape the meat out.  I have a pretty high tolerance for gross things, but I am starting to grow weary of clam guts!

In between tows there is a little bit of down time to catch your breath, drink coffee and eat cookies, watch the ocean, and read a book.  During one of these breaks, the Chief Scientist Victor Nordahl, took the moment and had his hair cut!

Jessie Soder: Happy as a Clam, August 12, 2011

NOAA Teacher at Sea
Jessie Soder
Aboard NOAA Ship Delaware II
August 8 – 19, 2011 

Mission: Atlantic Surfclam and Ocean Quahog Survey
Geographical Area of Cruise:  Northern Atlantic
Date: Wednesday, August 12, 2011 

Weather Data
Time:  12:00
Location:  41°47.405N, 67°21.702W
Air Temp:  18.4°C  (65°F)
Water Temp:  17°C (63°F)
Wind Direction:  South
Wind Speed:  8 knots
Sea Wave height: 1 foot
Sea Swell:  2 feet

Science and Technology Log

TK holding a monkfish caught in the dredge

When I was a little girl I was always excited to pull the minnow trap up from the end of the dock to see what oddities I had caught accidentally while trying to trap minnows.  I am reliving this excitement on a much larger scale on this research cruise.  The dredge we are using to fish for ocean quahogs and surfclams is 5ft x 20ft, weighs 2500lbs, and is pulled for ¼ nautical mile each time it is towed.  (That means it covers an area of about 9000 square feet.)  As you might imagine it accidentally catches things besides the ocean quahogs and the surfclams that we are fishing for.

The dredge is lowered into the water off the back of the ship.  Once it hits the ocean floor a powerful jet of water is sprayed into the ocean floor in front of it to “liquefy” the sand or mud on the ocean bottom.  This loosens the clams and suspends them in the water, just above the bottom.  (Ocean quahogs and surfclams aren’t far below the bottom; just a few inches.)  Then, while they are suspended in the water the dredge scoops them up.  The dredge is brought back up to the ship and dumped and we sort through the catch.  The ocean quahogs, surfclams, and a few other species are kept to weigh and measure.  Below is a video of the dredge being hauled back on the back deck of the ship.

After three watches I am getting pretty good at identifying ocean quahogs and surfclams.  What is the difference between an Atlantic surfclam and an ocean quahog?  Well, they are very similar!  They are both bi-valve mollusks, which means that they have two shells covering a soft body.  They both burrow into the sand so that only their siphon sticks out.  Both of them filter their food, algae and plankton, through their siphon.  One of the biggest differences between them is in the way that their shells connect, or hinge together.  Another difference is their lifespan.  The ocean quahog lives for more than 150 years and the Atlantic surfclam lives for approximately 30 years.  Their size and shape are different too.  Ocean quahogs are rounder than the Atlantic surfclams, which have a triangular shape.  The  Atlantic surfclam also grows larger than the ocean quahog.

Ocean Quahog (left) Atlantic Surfclam (right)

Just like I was excited as a kid to find crayfish and bullheads in my minnow trap I am excited to see what the dredge brings up each time.  So far our biggest catch was 4400 quahogs!  Conversely, our smallest catch was just three quahogs! Sometimes the dredge is filled with empty shells, or empty shells and sand dollars, or thousands of clams, or sometimes it is really sandy.  Each time it is a surprise and it gives you a brief glimpse of what the bottom looks like.

Personal Log

Empty shells and sand dollars

There are many potential dangers that you can face every day while working on a ship.  In fact, since being aboard we have run three drills; man overboard, fire, and abandon ship.  These drills are run on every trip so that everyone knows exactly what to do.

I think that there is something about being at sea on a ship that heightens your awareness of yourself.  I have experienced that same sort of feeling when I am sea-kayaking in big water, or hiking on a bear trail.  It is the feeling that there is something out there that is bigger than you are.  You sense things in a much clearer and acute way.

This evening the sun was going down on the starboard side of the ship and the moon was coming up on the portside.  We could see for miles and miles.  Earlier today we watched a school of tuna swim past and dolphins in the distance.  It was a beautiful clear and sunny day and we were 140 miles from land.  We are lucky.

Questions to Ponder

The clams and quahogs are collected on this research cruise from the sea floor using a hydraulic dredge.  The dredge is lowered and run along the seafloor for about 5 minutes in order to pick up the clams and quahogs.  Each time this is done it is called a “tow.”  How many people do you think are needed to conduct (operate the machinery and collect the data) one tow for clams and quahogs?  How many different jobs are there during one tow?

Anne Artz: August 4, 2011

NOAA Teacher at Sea
Anne Artz
Aboard NOAA Ship Delaware II
July 25 — August 5, 2011

Mission: Clam and Quahog Survey
Geographical Area: North Atlantic
Date: August 4, 2011

Weather Data from the Bridge
Location:  41 10.239 N; 67 36.023 W
Conditions:  Foggy in the morning giving way to partly cloudy skies; warming up, water calm.

Science and Technology Log

Today at approximately 11 am we finished our last dredge of this leg of the clam survey.  We just completed station #371.  There are approximately 500 stations scheduled for the entire clam survey with the final 2-week leg still left to complete.  We return to Woods Hole tomorrow morning and the Delaware II is expected to leave for the final leg on Monday morning, returning to Georges Bank to complete the final station dredges there.

Volunteer clam counters on the Delaware II

The past two days we have encountered some mechanical problems which the very capable crew repaired, and the past 12 hours we have collected large quantities of quahogs and surfclams in our final ten dredges.  We will spend the remainder of today cleaning up the deck, the wet lab, the dry lab, and putting away all the equipment we’ve been using.  The trip home will take approximately 12 hours.  We anticipate arriving in Woods Hole at 7 am in the morning.

Personal Log

It’s been an incredible trip for me — I’ve really come to appreciate what life at sea is like for the men and women who do this day in and day out all year long.  We were fortunate to have excellent weather and relatively calm seas and I can’t imagine what it would have been like to do this type of work in cold, windy rain, rough seas, or even with ice covering the deck and its equipment.  There are two teams or shifts: the day shift (noon to midnight) and the night shift (midnight to noon).  Each shift has a Watch Chief who coordinates the work of the science crew, enters all the data of all the clams and other things we bring up, and communicates with the bridge and Chief Scientist.

Watch Chief Jonathan Duquette

Watch Chief Nicole Charriere

Jonathan Duquette is the day shift Watch Chief and Nicole Charriere is the night shift Watch Chief, both of whom do an excellent job not only coordinating the work in the lab but also keeping the science crew (mostly us volunteers) informed of what we’re doing, where we’re going, and what we can do to help.  They are extremely hard-working and it’s been a privilege to work alongside both of them.

Anne Artz: August 2, 2011

NOAA Teacher at Sea
Anne Artz
Aboard NOAA Ship Delaware II
July 25 — August 5, 2011

Mission: Clam and Quahog Survey
Geographical Area: North Atlantic
Date: July 30, 2011

Weather Data from the Bridge
Location:  Georges Bank off the New England coast
Latitude: 42.634N
Longitude: 68 00.801 W
Conditions: Cloudy today, somewhat cooler but with sun most of the day

Science and Technology Log

This being the beginning of a new month we all did our safety drills on August 1 – that means everyone, including all the crew.  First we did the fire drill then the “Abandon ship” drill where we had to put on our “gumby” suits in one minute.  I did much better this time!  We’ve moved away from the New York-New Jersey coast and are now on the Southern Georges Bank.  We ran into a problem this morning when the cable that runs the pump for the dredge got tangled around the dredge during one of the drops.

A damaged power cable on the dredge

It necessitated cutting the cable that was twisted around the dredge then reconnecting it.  The cable itself is a series of copper wires twisted into 6 coils, surrounded by a neoprene “skin”, then surrounded by a Kevlar sleeve, and finally a synthetic woven casing.  It will take somewhere of 6-8 hours to repair the cable during which time we cannot do any dredging.  I’m going to use the down time to introduce you to some of the crew here on the Delaware II.

LCDR Richard Hester and ENS Carl Noblitt

There are three groups of workers: the NOAA Commissioned Corps which run the ship, the crew members who perform day-to-day work on board, and the science crew who are responsible for performing the scientific experiments for each expedition.  The NOAA Commissioned Corps on the Delaware II consists of the Commanding Officer (CO), LCDR Richard Hester, Executive Officer (XO), LCDR Sean Cimilluca, LT Fiona Matheson in charge of operations, ENS Shannon Hefferan, the Navigations Officer, and ENS Carl Noblitt, Junior Officer.

LCDR Sean Cimilluca

I interviewed Ensign Hefferan and asked her how she got into the NOAA  Commissioned Corps and what her job was like.  I’ll be posting that interview once we are back in Woods Hole since internet connections are not that good out at sea.

Personal Log

I would be remiss if I didn’t give credit to our outstanding cooks on the Delaware II.  Both of the men who work in the galley do an amazing job.  Other than the first day I haven’t made it for breakfast but lunch and dinner have been wonderful.

Top chefs Jonathan Rockwell and James White on the Delaware II

We’ve had everything from BBQ chicken, lasagna, a full turkey dinner, scallops, shrimp, and lots of different kinds of fish.  Besides all that, they cook vegetables that even my husband might eat and he won’t eat anything but a baked potato!  They feed all 30 of us every day and it’s a good thing we work so hard otherwise I’d definitely have to be dieting when I get home!

Anne Artz: July 30, 2011

NOAA Teacher at Sea
Anne Artz
Aboard NOAA Ship Delaware II
July 25 — August 5, 2011

Mission: Clam and Quahog Survey
Geographical Area: North Atlantic
Date: July 30, 2011

Weather Data from the Bridge
Location:  Off the coast of New York (Long Island)
40 36.212 N; 72 07.159 W
Conditions: Warm, sunny with very few clouds, very little wind, calm water

Science and Technology Log

The process of sampling the ocean bottom for surfclams and quohogs isn’t as easy as it sounds.  Both of these animals live below the surface of the ocean bottom and that ocean bottom can be sand, mud, or contain a large number of rocks.   To get to the clams the dredge is lowered into the water using a large crane and cable.  Once on the ocean floor, a pump directs the edge of the dredge into the sand/mud and at the same time blows back anything collected into the back of the dredge.  The entire time the ship is moving, dragging the dredge along the bottom.  The idea is for the clams and other larger samples to remain in the dredge while mud and sand wash out the sides and the back.  This works most of the time but occasionally we have brought up the dredge filled with grey sticky mud or large amounts of sand and rocks.  We can put the dredge back into the water off the stern (rear) of the ship and wash away some, but the sticky grey mud has caused problems and we keep our fingers crossed each time the dredge comes up.

The dredge that is lowered to the ocean floor to collect samples

Before sending the dredge down, three sensors are loaded onto the top and side.  These are similar to flash drives that collect certain data such as water depth, temperature, and tilt. This data is retrieved and downloaded into the computer after each “event” (the term used for each sample).  I’ve been trained on setting up the event using the computer in the bridge.  It requires communicating with the NOAA Corps officers who are on the bridge navigating the ship.  These people work closely with the winch operator who is lowering the dredge into the water at designated points.

NOAA Lead Fisherman Todd Wilson is responsible for operation of the winch that lowers the dredge.

The winch operator is also in direct communication with the crew on the deck who assist in lowering and raising the dredge and providing for a safe working environment for the volunteers and scientists.  Because of  all the heavy equipment on the deck, we are all required to wear hard hats when on the deck.  Of course, we also wear our life jackets.  The process of lowering and raising the dredge in specific areas is highly technical and one that is worked out well in advance of each sea trip.  Once at sea, it is the job of the Chief Scientist (Jakub Kircun) to monitor our sampling sites.

The Chief Scientist of the Delaware II Jakub Kircun

Occasionally we have to make adjustments, such as yesterday when the blade assembly of the dredge was damaged by rocks.

The broken blade apparatus that had to be removed from the dredge and replaced.

We had to stop our work for almost two hours while the crew removed the damaged part and replaced it with a new one.  This happens with some regularity so the ship carries extra blades and blade assemblies.  There are only two more assemblies left (of the part we replaced yesterday) and approximately three more weeks of sampling.  I asked what would happen if we ran out of blades and/or blade assemblies and was told the last leg (the last two weeks of sampling) may have to be cut short.  If possible, the crew may try to repair the broken part.

Personal Log

I’ve gotten to know my fellow team (those of us on the noon-midnight shift) through our long hours on deck and in the lab.  Two of the volunteers are like me – here for this particular leg.  Brenna O’Neill  is a graduate student at the Florida Institute of Technology and works in marine sciences.  Henry Hope is a NOAA employee who usually works in a lab in Woods Hole, MA but volunteered for this trip to see what kind of science we did at sea.  The other members of our team are all NOAA employees – either working continuously on the ship for all the science expeditions or part time on the ship and part time in a lab.  I was surprised to find out that there are various science expeditions carried out all year long – including in the middle of winter.  One of the crew told me of working on deck having to chip away ice from the equipment before it could be used.  It’s been so warm and humid on this trip I can’t imagine being that cold.  In fact, I brought several sweatshirts and jeans with me thinking it might be cool out at sea but haven’t even looked at them since I arrived.  It’s been all t-shirts and shorts even at midnight.  Last night we had another 2-hour delay because of a lightning storm – this time we DID hear the thunder!

Anne Artz: July 26, 2011

NOAA Teacher at Sea
Anne Artz
Aboard NOAA Ship Delaware II
July 25 — August 5, 2011

Mission: Clam and Quahog Survey
Geographical Area: North Atlantic
Date: July 26, 2011

Weather Data from the Bridge
Location: 40 32.672 N070 43.585 W
Temperature: 18.5 C
Winds:  Easterly at 3-4 knt
Conditions:  Sunny today, some clouds, ocean calm

Science and Technology Log

Our first full day at sea (and at work)!  We left the dock at Woods Hole, MA yesterday at 2 pm and headed out past Martha’s Vineyard and Nantucket.  While steaming towards our sampling site, we practiced two very important safety drills — a fire drill and the abandon ship drill.  The abandon ship drill was unique in that we had to don our survival suits (supposedly in a minute but I think I took longer than that) that protect us in the water from hypothermia and also help keep us afloat.

Survival Suit

Anne Artz in her survival suit

Around 6 pm we reached our first sample location and the “day team” (that’s me and some fellow volunteers) started our work.  The testing protocol is fairly simple: sample sites have been predetermined by computer.  Survey sites are selected based on depth and location (latitude and longitude).  When we reach those locations, a large sled-like cage called a dredge is lowered into the water and dragged along the ocean floor for a prescribed amount of time (generally 5 minutes).

Sampling dredge on the Delaware II

This cage goes on the ocean floor scooping up samples for our analysis.

The dredge is then brought up and the contents emptied onto the deck.  Our work then takes 10-15 minutes to sort through what is brought up, keeping those items we are surveying or counting, and throwing the rest back into the water.  We attempt to identify organisms we bring up and we count all live bivalves, any gastropods, hermit crabs, starfish and all fish.  Species we identify and measure are the surfclam, the ocean quahog, the southern quahog, and sea scallops.  Once we’ve separated out what we need, we weigh the catch then measure the size of each item collected.  We throw everything back into the water and clean up the deck while heading to our next location.  The procedure is repeated about twice each hour.  For our work on the deck we wear protective clothing, hard hats, and of course, a life vest.

Personal Log

There are seven volunteers aboard this trip, including myself.  They are a varied group from all over but are all very interested in ocean science.  Some of them are college graduates, some are still in college and we are all first-timers on this type of research vessel.  We were assigned a 12-hour shift, either noon to midnight or midnight to noon.  I feel fortunate to be on the noon-midnight shift as that means I don’t have to alter my sleeping pattern much.  It’s tiring work but the good part is there are breaks between each haul so most of us have our books with us on the deck (so handy to have a Kindle!).  The crew here is as varied as the volunteers, from all over the country and they are all very good at what they do.  I initially thought having 4 girls sleeping in a room the size of a walk-in closet would be difficult but it’s not.  At any given time two of us are on deck, on duty, so the room is available for sleeping, changing, showering, etc.  We all respect quiet below deck because at any given time, someone is always trying to sleep!

Interesting Things Seen Yesterday

A shark with a rather large fin above the water was following us from a distance for a while — maybe curiosity?  We brought up several skates (they look like rays) the largest being about 12 inches long.  They are incredibly beautiful up close, looking almost angelic.  It seems a shame they have such a bad reputation!

Lisbeth Uribe, August 5, 2008

NOAA Teacher at Sea
Lisbeth Uribe
Onboard NOAA Ship Delaware II
July 28 – August 8, 2008

Mission: Surfclam and quahog survey
Geographical Area: Southern New England and Georges Bank
Date: August 5, 2008

Chief Scientist Vic Nordahl, Chief Boatswain Jon Forgione and Chief Engineer Patrick Murphy discussing the best way to reattach the pump power cable to the dredge.

Chief Scientist Vic Nordahl, Chief Boatswain Jon Forgione and Chief Engineer Patrick Murphy discussing the best way to reattach the pump power cable to the dredge.

Ship Log 

In the last 48 hours the engineers, crew and scientists have had to re-attach the power cable to the dredge (see photograph), fix the cracked face plate of the pump, replace the blade and blade assembly, change the pipe nozzles that direct the flow of water into the cage, and work on the dredge survey sensor package (SSP). Dredging is hard on the equipment, so some mechanical problems are to be expected. The main concern is for lost time and running out of critical spare parts.  So far we have had great success with making the repairs quickly and safely.

Science and Technology Log 

Collecting Tow Event and Sensor Information for the Clam Survey 
Over the weekend I was moved up to the bridge during the towing of the dredge. I was responsible for logging the events of each tow and recording information about the ship and weather in a computerized system called SCS (Scientific Computer System). I listened carefully to the radio as the lab, bridge (captain) and crane operator worked together to maneuver the dredge off the deck and into the water, turn on the pumps, tow the dredge on the seafloor bottom, haul the dredge up, turn off the pump and bring the clam-filled dredge back on deck. It is important that each step of the tow is carefully timed and recorded in order to check that the tows are as identical as possible.  The recording of the events is then matched to the sensor data that is collected during dredge deployment. As soon as the dredge is on deck I come downstairs to help clean out the cage and sort and shuck the clams.   

Lisbeth is working on the bridge logging the events of each tow into the computer system.

Lisbeth is working on the bridge logging the events of each tow into the computer system.

My next job assignment was to initialize and attach to both the inside and outside of the dredge the two mini-logger sensors before each tow. Once the dredge was back on deck I removed both mini-loggers and downloaded the sensor data into the computers. Both sensors collect pressure and temperature readings every 10 seconds during each tow. Other sensors are held in the Survey Sensor Package (SSP), a unit that communicates with onboard computers wirelessly.  Housed on the dredge, the SSP collects information about the dredge tilt, roll, both manifold and ambient pressure & temperature and power voltage every second. The manifold holds the six-inch pipe nozzles that direct the jets of water into the dredge.  Ideally the same pump pressure is provided at all depths of dredge operation. In addition to the clam survey, NOAA scientists are collecting other specimens and data during this cruise.

Two small black tubes (~3 inches long), called miniloggers, are attached to the dredge. The miniloggers measure the manifold (inside) and ambient (outside) pressure and temperature during the tow.

Two small black tubes (~3 inches long), called miniloggers, are attached to the dredge. The miniloggers measure the manifold (inside) and ambient (outside) pressure and temperature during the tow.

NOAA Plankton Diversity Study 
FDA and University of Maryland Student Intern Ben Broder-Oldasch is collecting plankton from daily tows.  The plankton tows take place at noon, when single-celled plants called phytoplankton are higher in the water column. Plankton rise and fall according to the light. Plankton is collected in a long funnel-shaped net towed slowly by the ship for 5 minutes at a depth of 20 meters. Information is collected from a flow meter suspended within the center of the top of the net to get a sense of how much water flowed through the net during the tow. Plankton is caught in the net and then falls into the collecting jar at the bottom of the net.  In the most recent tow, the bottle was filled with a large mass of clear jellied organisms called salps. Ben then filters the sample to sort the plankton by size. The samples will be brought back to the lab for study under the microscope to get a sense of plankton species diversity on the Georges Bank.

An easy way to collect plankton at home or school is to make a net out of one leg of a pair of nylons. Attach the larger end of the leg to a circular loop made from a metal clothes hanger.  Cut a small hole at the toe of the nylon and attach a plastic jar to the nylon by wrapping a rubber band tightly around the nylon and neck of the jar.  Drag the net through water and then view your sample under a microscope as soon as possible.

Biological Toxin Studies 

NOAA Scientist Amy Nau hauls the plankton net out of the water using the A-frame. (Upper insert: flow meter; lower insert: plankton in the collection bottle after the tow).

NOAA Scientist Amy Nau hauls the plankton net out of the water using the A-frame. (Upper insert: flow meter; lower insert: plankton in the collection bottle after the tow).

Scientists from NOAA and the Food & Drug Administration (FDA) are working together to monitor clams for biological toxins. Clams and other bi-valves such as oysters and mussels, feed on phytoplankton. Some species of phytoplankton make biological toxins that, when ingested, are stored in the clam’s neck, gills, digestive systems, muscles and gonadal tissues.  If non-aquatic animals consume the contaminated clams, the stored toxin can be very harmful, even fatal.  The toxin affects the gastrointestinal and neurological systems. The rate at which the toxins leave the clams, also known as depuration rate, varies depending on the toxin type, level of contamination, time of year, species, and age of the bivalve. Unfortunately, freezing or cooking shellfish has no effect on the toxicity of the clam. The scientists on the Delaware II are collecting and testing specimens for the two biological toxins that cause Amnesia Shellfish Poisoning (ASP) and Paralytic Shellfish Poisoning (PSP).

NOAA Amnesia Shellfish Poisoning (ASP) Study 
A group of naturally occurring diatoms, called Pseudo-nitzschia, manufacture a biological toxin called Domoic Acid (DA) that causes Amnesia Shellfish Poisoning (ASP) in humans.  Diatoms, among the most common organisms found in the ocean, are single-celled plankton that usually float and drift near the ocean surface. NOAA scientist Amy Nau collects samples of ocean water from the surface each day at noon. By taking water samples and counting the numbers of plankton cells, in particular the Pseudo-nitzschia diatoms, scientists can better determine if a “bloom” (period of rapid growth of algae) is in progress. She filters the sample to separate the cells, places the filter paper in a test tube with water, adds a fixative to the tube and sets it aside for further study in her lab in Beaufort, NC. 

Scientist Amy Nau filters seawater for ASP causing dinoflagellates.

Scientist Amy Nau filters seawater for ASP causing dinoflagellates.

FDA Paralytic Shellfish Poisoning (PSP) Study 
Scientists aboard the Delaware II are also collecting meat samples from clams for an FDA study on the toxin that causes paralytic shellfish poisoning. When clams ingest the naturally occurring dinoflagellate called Alexandrium catenella, they accumulate the toxin in their internal organs. When ingested by humans, the toxin blocks sodium channels and causes paralysis. In the lab, testing for the toxin causing PSP is a lengthy process that involves injecting a mouse with extracts from shellfish tissue.  If the mouse dies, scientists know the toxin is present. The FDA is testing the accuracy of a new quick test for the toxin called the Jellet Test Kit. After measuring and weighing a dozen clams from each station on the Georges Bank, Ben and Amy remove and freeze the meat (internal organs and flesh) from the clams to save for further testing by scientists back on land. At the same time, they also puree a portion of the sample and test it using the Jellet strips for a quicker positive or negative PSP result.

Personal Log 

Pilot whales sighted off the bow!

Pilot whales sighted off the bow!

The problems that we have experienced with regard to the dredge over the past few days are an important reminder of the need for the scientists and crew to not only be well prepared but also flexible when engaged in fieldwork. All manner of events, including poor weather and mechanical difficulties, can and do delay the gathering of data. The Chief Scientist, Vic Nordahl, is constantly checking for inconsistencies or unusual patterns, particularly from the dredge sensor readings, that might need to be addressed in order to ensure that the survey data is consistent and accurate. The time required to repair the dredge meant I was able to do a load of laundry. Dredging is very dirty work! Good thing I am using old shirts and shorts. I also caught up on a few emails using the onboard computers. Though the Internet service can be slow at times it is such a luxury to be able to stay in touch with friends and family on land. I still have two very special experiences that I wish to share before ending my log.

Late in the evening a couple of days ago, as we steamed toward our next tow station, I was invited to peer over the bow. The turbulence in the water was causing a dinoflagellate called Noctiluca to sparkle and glow with a greenish-blue light in the ocean spray.  The ability of Noctiluca and a few other species of plankton and some deep-sea fish to emit light is called bioluminesense. A few days later we had the great fortune to see five pilot whales about 100 meters away, gliding together, their black dorsal fins slicing through the water, occasional plumes of air bursting upward through their blowholes (nostrils located on the tops of their heads).

Answers to the previous log’s questions: 

1. What is the depth and name of the deepest part of the ocean? The Mariana Trench in the Pacific Ocean is 10,852 meters deep, (deeper than Mount Everest is tall – 8,850 meters).  Speaking of tall mountains, the tallest mountain in the world is not Mount Everest, but the volcano Mauna Kea (Hawaii).  It reaches 4,200 meters above sea level, but its base on the sea floor is 5,800 meters below sea level.  Its total height (above base) is therefore 10, 000 meters!

2.What is the longest-lived animal on record? In 2007, an ocean quahog was dredged off the Icelandic coast.  By drilling through and counting the growth rings on its shell, scientists determined it was between 405 and 410 years old. Unfortunately it did not survive the examination, so we do not know how much longer it would have lived if left undisturbed. This ancient clam was slightly less than 6 inches in width.