Karah Nazor: Sorting Protocol and the Ubiquitous Tunicates of the Central CA Coast: Salps and Pyrosomes, May 30, 2019


NOAA Teacher at Sea

Karah Nazor

Aboard NOAA Ship Reuben Lasker

May 29 – June 7, 2019


Mission: Rockfish Recruitment & Ecosystem Assessment

Geographic Area: Central California Coast

Date: May 30, 2019

Last night I fell asleep, twice, at the lab bench in between trawls, since I am still adjusting to being on the night shift.  We worked from 9:00 P.M. to 6:30 A.M. After the shift I had a nice hot shower and slept a solid 9 hours from 7:00 AM to 4:00 PM.  Hopefully, I will be less drowsy tonight!

Upon waking, I went to the galley and grabbed some Raisin Bran and coffee and took it up to the flying bridge to hang out with Ornithologist Brian Hoover.  Our current location is in the middle of the Channel Islands, an area I know something about because my friend Evan Morrison, mentioned in my first blog, helps with the Channel Islands Swimming Association, and I would like to swim between these islands one day.  Lauren Valentino, Flora Cordoleani, Ily Iglesias and I congregated on the flying bridge and decided we should exercise. We joined Flora in her squat challenge (80 squats on this particular day), followed by 5 minutes of planking and a bit of erging.  Half of female members of the fish sorting team are avid rock climbers. They did lots of pull-ups using the rock ring climbing training holds that are installed there.

It felt nice and warm when the ship stopped for deployment of the Conductivity, Temperature and Depth (CTD) Rosette, and it got chilly again as the wind picked up when the ship started moving again. We saw a few whale spouts in the distance and at 5:30 P.M. we went down to the galley for a delicious meal of steak and mashed potatoes.  I am beginning to really appreciate how nice this whole experience has been in terms of amenities. The NOAA Reuben Lasker first set launch in 2014 and is a state of the art fisheries vessel with a sophisticated acoustics lab, fish lab, dynamic positioning system, CTD, etc., but is ALSO equipped with creature comforts including a movie lounge, an ice cream cooler loaded with ice cream sandwiches, snickers, fruit pops, you name it, and my personal favorite – a coffee bar where all coffee is freshly ground, an espresso machine, and all varieties of milk and creamers, including Reese’s cup whipped cream. The mattress in my stateroom bunk is quite comfortable and the shower gets hot within seconds! I doubt it can get much better than this for a research experience at sea?

Game Plan and Trawling Line: Point Sal line with five 15 minute hauls.

I am familiar with the sorting protocol now. The catch is dropped from the net into the bucket by members of the deck crew and survey tech, with the oversight of Keith Sakuma, Chief Scientist and NOAA Operations Officer Keith Hanson.  The bucket is immediately placed in the fish lab and this is when the fish sorting team starts our work.

Cobb Trawl net
Dropping the catch from the Cobb Trawl net into the bucket.
fish on a sorting tray
A volume of fish just placed on a sorting tray. This catch has a lot of anchovies, krill, and California smoothtongues.
Separating the krill
Separating the krill from the myctophids, Northern anchovies, and California smoothtongues.
Sorting fish group photo
Team Red Hats sorting fish. NOAA’s Keith Hanson in the rear left side.


SORTING AND COUNTING METHOD

We start by carefully picking through a 2000 mL or 5000 mL volume of the harvest, depending on Keith Sakuma’s initial assessment of the species density and volume in the bucket.  The first volume of catch to be sorted is evenly dispersed onto four white sorting trays arrayed on the main lab bench. Once you have a pile of the catch on your tray, you start to separate them into piles of different types of organisms, such as Northern anchovies, ctenophores, krill, salps, pyrosomes, Californian smoothtongues, squid, rockfish, myctophids, and young of year (YOY) fish.  I prefer to use my hands for sorting while others use forceps. Once sorted, we count the number of individuals for each species. If we have difficulty identifying an animal that we have not yet seen, we ask Keith Sakuma or a more experienced team member to help with identification. YOY fish, some in larval form, are particularly difficult for me.

Once sorted and counted, we verbally call out the common name and number of organisms to Keith Sakuma who manually records the data in a 3-ring binder for the lab hard-copy.   For smaller organisms, such as krill or salps, or in hauls with a high number of any particular species, it would be quite tedious to pick out and count each individual in the total haul.  This is why we start with a small subsample volume or 0.5, 2 or 5L, count the individuals in that small volume, establish the ratio for the number of individuals in that volume, and then extrapolate and calculate by the total volume of the haul.  For example, if we counted 97 pyrosomes in the initial 5L sort, and we collected a total of 1000L, then we can say that there are 19,400 pyrosomes in the haul.

Chief Scientist Keith Sakuma
Chief Scientist Keith Sakuma recording the data from a haul during sorting.

Once 20 individuals of each species have been called out, we no longer have to count that species since the ratio for this catch has already been established and to expedite sorting the rest of the volume.  Following sorting, the length of the twenty representatives of each species is measured using electronic calipers and the values populate on an Excel spreadsheet. After measuring, specimens requested by various research institutes including Scripps Institution of Oceanography, Moss Landing, and Monterey Bay Aquarium Research Institute (MBARI) are collected, labelled and frozen.

Flora Cordoleani
Flora Cordoleani keeping track of which specimens are to be preserved for various research groups.
Keith Sakuma bagging specimens to send to collaborators.

Creature(s) feature: Salps and Pyrosomes. 

Salps What are these strange gelatinous organisms in our catch that look like little puddles of clear jelly with a red, green, yellow, and brown digestive organ in the center?  They are goopy, small and slippery making them difficult to pick up by hand. They float on the sea surface and are ubiquitous in our hauls BUT NOBODY KNOWS ABOUT THEM.

These creatures are called salps and belong to the subphylum Tunicata. Tunicates have a notochord in their early stage of life which makes them members of the phylum Chordata, to which humans also belong. Having a transparent body is a way escape being preyed upon.

A group of salps. This species is dime to quarter sized and this number of salps occupies a volume of ~10-15 ml once placed in a beaker.
Salp digestive organs.

Salps are planktonic tunicates  That can be found as individual salps or in long chains called blastozooids.   The salps shown in the photo below were individuals and were notable in most of our hauls. Individual salps in this pile are dime to quarter sized and occupy a volume of ~10-15 ml. We measured the volume of salps in every haul.

While on the topic of salps, I will tell you about a cool 1 inch long salp parasite I found on my sorting tray (see image below). Keith Sakuma explained that it was a deep sea amphipod called Phronima which is a parasitoid that takes up residence inside of a salp’s body, eats the salp’s organs, and then lays its eggs inside of the salp. The King-of-the-salmon, Trachipterus altivelis, (which we are also catching) uses its protrusible jaw to get inside of the salp just to eat this amphipod!

Phronima amphipod
Phronima amphipod – lives and reproduced in salp after eating the salp’s organs. King-of-the-salmon fish use their protrusible jaws to eat the amphipod.
King-of-the-salmon
King-of-the-salmon, Trachipterus altivelis
King-of-the-salmon jaw protruded
King-of-the-salmon, Trachipterus altivelis, who preys upon phronima living inside of salp, with jaw protruded.
A large haul full of salps.

Another type of salp we keep catching is Thetys vagina, a large solitary species of nektonic salp that feeds on plankton, such as diatoms, and is an important carbon sink in the ocean. Thetys has an external surface, or test, that is covered with bumps and ridges, as seen in the photo below.

Thetys vagina, the twin-sailed salp.
Thetys vagina, the twin-sailed salp.
internal filtering organ
The internal filtering organ of Thetys vagina.
Kristin Saksa examining a larger Thetys
Kristin Saksa examining a larger Thetys vagina, or the twin-sailed salp. The dark colored tentacles are downward facing. This is the siphon where water enters the sac-filled body.

Pyrosomes Pyrosoma atlanticum are another type of planktonic tunicate which are very numerous in most of our hauls. Pyrosomes look like bumpy pink hollow tubes with openings on both ends. They are rigid in structure and easy to pick up by hand, whereas salps are goopy and difficult to pick up by hand.  We have collected some pyrosomes that are 13 inches long, while most are in the 4-6 inch range. The small pyrosomes look like clear Tic Tacs, but they do not taste as such.

Pyrosoma atlanticum
Pyrosoma atlanticum, with an ~6 inch specimen on the left and small pyrosomes on the right.

How can pyrosomes be so ubiquitous just 20 miles or so off of the Central California Coast, but I have never seen one that has floated up on the beach or while swimming?

Pyrosoma atlanticum are also planktonic tunicates, but are colonial organisms made up of many zooids held together by a gelatinous structure called the tunic. One end of the tube is wide open and filters the water for zooplankton and phytoplankton, while the other end is tighter and resembles a diaphragm or sphincter. The pyrosomes we harvested appeared in diverse array of pinks and purples.  Pyrosomes are believed to harbor intracellular bioluminescent bacteria. Pyrosomes are drifting organisms that swim by beating cilia lining the branchial basket to propel the animals through the water and create a current for filter feeding. 

Pyrosome rainbow
Pyrosoma atlanticum assorted by color.
Kristin Saksa
Moss Landing Graduate Student Kristin Saksa excited about the large haul of Pyrosoma atlanticum.
high-five
Pyrosoma atlanticum high-five.

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