Midwater Ecology Expedition Fall 2019

The researchers are studying vision in deep-sea animals like this unusual piglet squid, Helicocranchia. Image by Kat Bolstad.

MBARI Expedition #479

Expedition goal: The principal goal of this expedition is to measure oxygen consumption rates of select deep-sea animals using a custom-designed tool, the Midwater Respirometry System (MRS), at both shallow and deep locations. We will also be observing and collecting midwater animals to investigate their ecology, physiology, and behavior in conjunction with onboard collaborators from GEOMAR Helmholtz Centre for Ocean Research in Kiel, Germany, and the Auckland University of Technology in New Zealand. Additional research will include the effects of abrupt seafloor topography on the distribution of midwater species, and the impact of food falls (carrion) on the deep-sea food web.

Expedition dates: November 15-21, 2019

Ship: R/V Western Flyer

Research technology:  ROV Doc Ricketts, Midwater Respirometry System

Expedition chief scientist: Bruce Robison

The Midwater Ecology Group will continue its research into the respiration rates (oxygen consumption) of deep-sea animals using the Midwater Respirometry System (MRS). The MRS allows the group to measure these animals’ metabolic rates where they live as opposed to in the laboratory at surface pressure. Understanding the energy requirements for these animals will allow a clearer understanding of the biological pump and the energy transfer from the surface, through the ocean’s midwaters to the seafloor. The group’s studies over the last three decades have shown the area of the deep ocean where the oxygen level is lowest is growing. The midwater team has documented the vertical expansion of the oxygen-minimum zone by 60-to 80-meters in relation to ocean warming. This expansion has fragmented the midwater community by shifting the distributions of some midwater animals. Long-term studies like this are necessary for first detecting shifts in communities and then predicting how communities will respond in the future to further changes in the environment

Midwater cruises also include exploration of this large habitat, where light does not penetrate from above and the seafloor is not in sight below. Such explorations have led to many significant observations and discoveries about this habitat and the animals that live there—and their behavior.

Updates from researchers on the R/V Western Flyer:

Thursday, November 21, 2019
Henk-Jan and Stella Scheer

Deepstaria and its commensal isopod Anuropus

We are guest scientists from GEOMAR Helmholtz Centre for Ocean Research Kiel and are very happy to join the MBARI midwater expedition on the Western Flyer. During this week, we have been documenting and collecting a range of midwater animals. Such in situ observations provide much more than an image alone. For example, by studying animals in their natural habitat, associations between organisms can be observed. A good example of such an association we came across early in the cruise and involved the presumably commensalistic association between the large medusa Deepstaria enigmatica and the giant isopod Anuropus. Repeated observations of this large medusa show that there is always a single isopod inside the bell of Deepstaria. Many gelatinous species are hosts for amphipod symbionts, and on this cruise, we also found hyperiids on the jellyfish Periphylla periphylla and inside pyrosomes. Depending on the species of gelatinous zooplankton, the crustaceans use the host as a transport vehicle, as protection from predators, or as a source of food.

Astrid, Rob, Henk-Jan, and Kim ready for a night of midwater trawling after the ROV has returned to the R/V Western Flyer

A major focus of our research visit is to study the connections between the midwater food web and the benthic food web (at the seafloor). When midwater animals die, the carcasses sink to the seafloor and, once deposited, the carcass becomes a so-called foodfall. The foodfall attracts a variety of benthic fauna including scavengers and create local areas of enrichment. For many deep-sea bottom ecosystems, the deposition of organic material from the water column onto the seafloor is the only source of food supply. However, we know little about which pelagic species are the major contributors of organic matter, and which scavengers benefit from the foodfalls. Observations of carcasses on the seafloor are very rare, in particular those of medium-sized animals since they are rapidly consumed (refer to Astrid’s cruise log). The ROV Doc Ricketts is a great instrument to study foodfalls. During previous MBARI cruises in the Gulf of California, the ROV surveys revealed that deep-sea squid sink to the seafloor and are eaten by various organisms including crustaceans and sea stars (https://www.mbari.org/squid-graveyard/).

The common sea nettle or Chrysaora being eaten by Rathbunaster

On this cruise we have been performing seafloor ROV surveys to document and quantify foodfalls and their scavenging communities. On the very first day we already came across a Chrysaora jellyfish being eaten by sea stars. This particular foodfall was especially interesting since we observed it on the steep canyon walls. Using the unique VARS database of over 25 years of deep-sea observations, we plan to make an overview of the variety of foodfalls in Monterey Bay. Although the weather on Tuesday did not allow us to perform ROV operations, we used the shelter time inshore to collect large specimens of Chrysaora for future foodfall experiments.

It is a great experience to study the fascinating deep-sea fauna in the Monterey Canyon with MBARI’s Midwater Ecology Group, the ROV pilots, and the Western Flyer crew. Thank you!

Updates from researchers on the R/V Western Flyer:

Wednesday, November 20, 2019
Rob Sherlock

The word from Captain George Gunther was that we might have a short dive Tuesday due to deteriorating weather. This was seconded by the modern sailor’s favorite tool, windy.com. But first thing in the morning, the winds were light and we began our dive at 6:30 a.m., as always, feeling optimistic and excited about what the day would bring.  By 10:30 a.m. that optimism had turned like the weather. Winds gusting to 28 knots meant recovering the ROV in order to beat a hasty retreat into the relatively calm waters outside of Monterey harbor. What to do when the planned ROV dive is scrubbed due to high winds? Any number of things as it turns out.

Our colleagues from GEOMAR, Henk-Jan Hoving and Stella Scheer, noticed the surface waters full of Chrysaora fusescens, medusae commonly called “sea nettles.” If you’ve visited the Monterey Bay Aquarium, you may have seen these beautiful brownish-red medusae swimming gracefully with their tentacles and mouthparts streaming meters behind them. At this time of year these jellies are so common in Monterey Bay and along the California coast that leatherback turtles travel all the way from waters off Japan, crossing the vastness of the Pacific Ocean, just to feed on them and on Aurelia aurita, the moon jelly, also common here.

They aren’t the only ones. We have been encountering dead or dying Chrysaora hundreds of meters deep; usually with seastars, like Rathbunaster, eating them. Henk-Jan and Stella are interested in foodfalls and the animals attracted to them and made good use of the opportunity to collect some sea nettles they saw floating on the surface. The jellies will be frozen in order to make an artificial foodfall that we can later take down with the ROV to monitor.

While scanning the surface for Chrysaora, MBARI Postdoctoral Fellow Astrid Leitner and Kat Bolstad, a cephalopod researcher from New Zealand, spotted several dead Mola mola (ocean sunfish) floating at the surface as well. Since they were small, less than two feet in diameter and dead, it was easy to scoop them up in a net. All were missing their fins—a sign that sea lions had killed them. Not to eat, but because sea lions often grab small ocean sunfish by their prominent dorsal or ventral fins and then fling them like frisbees through the air! Fun for the sea lions, maybe, but not so much for the hapless sunfish. Like leatherbacks, the largest turtles, Mola mola eat jellies and grow to be among the largest of all bony fishes (hmm, must be something to this jelly diet).

Writhing mass of tapeworms from the gut of a Mola mola!

Along the way these slow-swimmers are parasitized by many different animals, from copepods to sea lice, roundworms, and tapeworms. And this is what had Kat excited (well, in a kinda’ gross, I’d-rather-be-dissecting-squid sort of way) as she and Astrid expertly dissected the Molas, and found and filled a bowl full of writhing tapeworms (cestodes) to pass along to colleagues who study these parasites. What remains from the Molas will be used for—you guessed it—foodfalls.

Bruce continues work on a manuscript while he watches the wind, Kim monitors his in-lab respirometers to make sure his Poeobius (butt worms) are still performing, George is currently keying out coronate medusae collected yesterday and me, well, seeing as we have some time, maybe I’ll write up a blog.

And so it goes, full circle back to where we started and, hopefully, tomorrow, back in the water first thing!

Updates from researchers on the R/V Western Flyer:

Monday, November 18, 2019
Kat Bolstad

The cock-eyed squid or strawberry squid, Histioteuthis heteropsis, photographed in the lab by Kat Bolstad.

It is wonderful to be back at sea. I’ve had the honor of sailing with the Western Flyer crew several times before, but not since 2015 (life and small children have happened in the meantime), so it’s great to be back aboard. And this cruise has gotten off to a wonderfully squiddy start for me—I lead a deep-sea squid research group in New Zealand (the AUT Lab for Cephalopod Ecology & Systematics) and the opportunity to see our animals in their natural environment is always a thrilling one.

In our first couple of days we’ve already seen nearly ten different taxa, including the always-intriguing “cock-eyed” squids (Histioteuthidae), delicate alien-looking “glass squids” (Cranchiidae), long-necked siphonophore-mimicking chiroteuthids, and even an “adolescent” vampire squid, in the transitional phase between baby and adult morphology where, for a short time, it has four fins instead of two. On the seafloor at 2,000 meters (6,561 feet) we came across a small octopus, and we’ve also seen a fair few zippy little Gonatus streaking past the camera in the upper layers.  An evening net tow brought in a rare paralarval (baby) Octopoteuthis, which has hooks all along the arms instead of suckers and a long photophore (light organ) at each arm tip.

The researchers are studying vision in deep-sea animals like this unusual piglet squid, Helicocranchia. Image by Kat Bolstad.

These observations will contribute to a number of different research projects we have underway, including a survey of visual capabilities and retinal structure in deep-sea oegopsid squids, and improving understanding of Pacific cephalopod diversity and interrelationships—especially since our glass squid specimen, Helicocranchia, is probably a new species! This family was recently reviewed in the Pacific ocean (see Aaron Evans’ thesis) which puts us in a good position to compare what we see here with what is known from the region and elsewhere in the same ocean basin. I’m hoping we’ll see a few more glass squid species—likely Galiteuthis phyllura and Taonius borealis—as these are some of my personal favorites to observe, being some of the very strangest among an already pretty bizarre group. Tentacles crossed!

Updates from researchers on the R/V Western Flyer:

Sunday, November 17, 2019
Astrid Leitner

This polychaete worm generally considered a seafloor resident was found swimming in the midwater.

We started out at our deep dive location just outside Monterey Bay on Saturday. We dove all the way to the bottom to about 3,000 meters (9,800 feet) where we deployed Henk-Jan and Stella’s bait package and filled up the Midwater Respirometry System for a 48-hour deep experiment. For this experiment, we managed to collect a very interesting polychaete worm which was swimming in the midwater, although it is generally considered a seafloor resident.

The weather got a bit rougher, and Saturday evening we were glad to head back into the more protected waters of Monterey Bay to our southern canyon wall site. We spent our full dive day on Sunday at this site, taking advantage of the late sunrises of the season to catch the daily downward dawn migration of midwater animals on video with the ROV. Because the ROV launches at 6:30 a.m. every day, and dawn was at 6:20 a.m. today, our timing was just right.

When this bait tray was first placed on the seafloor, it was full of squid—but the deep sea is a busy and active place with some hungry foragers.

I am interested in looking at how migrating midwater animals are affected by the abrupt canyon topography in Monterey Bay. I am especially interested in what happens to those animals which cannot complete their normal morning descent into deep waters because they ended up over the shallow canyon rim during the night while they were busy feeding near the surface. We completed both a set of morning transects down the wall and a complementary set of evening transects back up the wall. This will allow me to compare the distributions of animals relative to the canyon topography at different stages in the daily migration cycle. These transects involve difficult maneuvers in very challenging, steep terrain. Thanks to our team of talented ROV pilots we were able to collect two full sets of transects at the beginning and at the end of the day. Tonight we will be heading back out to the deep station to pick up the Midwater Respirometry System. Hopefully we will have calm seas for our dive out there tomorrow.

Updates from researchers on the R/V Western Flyer:

Saturday, November 16, 2019
George Matsumoto

We departed Moss Landing on Friday heading out to our first dive location on the south side of Monterey Canyon. The weather and sea conditions were pretty calm making for a nice beginning to our seven-day expedition. There are a lot of different objectives for this week but, luckily, the science team is flexible and the Western Flyer and Doc Ricketts crews are amazing and supportive of the work.

In addition to physiology research using the Midwater Respirometry System and remotely operated vehicle (ROV) Doc Ricketts, the science team is working on a couple of relatively new projects. One is to investigate the effect of relatively abrupt topography on the diversity and abundance of life. This involves new Postdoctoral Fellow Astrid Leitner whom you’ll hear more from later in the expedition. We also have Henk-Jan Hoving and Stella Scheer from GEOMAR on the expedition; Henk-Jan was a postdoctoral fellow and now runs his own research program at GEOMAR in Germany. They are working on the abundance and importance of food falls in the deep-sea and are planning to deploy some bait falls to observe timing and identity of visitors to the bait. Kathrin Bolstad is joining this expedition from Auckland University of Technology, New Zealand, and is primarily interested in cephalopods.

I’m interested in coronate medusa like this small jelly Periphylla. On the way down to the bottom, we were visited by a small group of Molas molas. When we arrived at the bottom (around 1,200 meters, or almost 4,000 feet), we spotted this cluster of Neptunea laying eggs in vertical columns. We spent a few hours doing horizontal transects starting in midwater and ending on the canyon wall, then finished the day with some acoustic surveys. All in all, a busy and productive start to the expedition.

MBARI Cruise Participants

Other Cruise Participants:

Henk-Jan Hoving and Stella Scheer, GEOMAR, Germany; Kathrin Bolstad, Auckland University of Technology, New Zealand