The ocean is filled with undescribed species

And here is one of them. This beautiful reddish copepod is also in the genus Pleuromamma, and does not yet have a scientific name. I show this for those of you who don’t yet know that the ocean is a mysterious and relatively uncharacterized place, with lots of secrets left to uncover. Despite a decade of discovery in the international Census of Marine Life, there are still many marine species left to be discovered and described. For some faunal groups, the majority of the species present may be new to science. We tend to think of marine zooplankton as being relatively well studied, in comparison to the deep sea. However, even for surface zooplankton, I suspect that the majority of species may be undescribed in high diversity ocean regions, such as the subtropical gyres. Learning about this diversity is critically important to understanding how these communities function, and the role different species play in marine food webs.

This beautiful Pleuromamma copepod is distinct from both P. abdominalis and P. quadrungulata, with which it co-occurs here in the equatorial region. It has long been noted that there is variation in the presence and degree of development of spines on the antennules of Pleuromamma copepods. In the photo, you can see two animals, oriented head to head, with the top animal lacking the strong spines on the antennules that are very visible in the animal below. It turns out that this variation is informative, and can be used to distinguish good species. Stay tuned for an upcoming publication from Junya Hirai (University of Tokyo) on the genetic lineages within the ubiquitous species P. abdominalis. I hope to find the time to establish a name for this organism, along with the many other undescribed lineages within this nominal species. Establishing a new name for a species is an opportunity to honor your predecessors and acknowledge the heroes that inspired your scientific journey. I hope to name at least one of these species P. frosti, in honor of Bruce Frost.

Keep in mind that even though we are now out in the middle of the Atlantic Ocean, you don’t have to go very far to find new species. You may even have some right in your backyard. For example, I know there are some undescribed copepods in the coral rubble right along the beach at Diamond Head, at one of the most popular surfing spots on Oahu (my backyard at home in Honolulu). There are probably also a myriad of small, but important, and unknown species lurking in the habitats around your home. Find them and be amazed!

How to catch plankton?

Well… remember that plankton can range in size from things that are very, very small, like bacteria, to things that are really quite large, like giant jellyfishes? How we catch plankton depends quite a bit on what type of plankton we would like to catch. It is also important to know that things that are small tend to be very abundant in the ocean, and organisms become more rare as they increase in size. This pattern means that we can usually sample small volumes of water to study small plankton, and we need to sample very large volumes of water to find large plankton. If we focus just on the animals that are in the plankton (and not the smaller things), we usually sample them using a few different ways:

Bongo nets

Using plankton nets. People have been collecting planktonic animals in nets for hundreds of years, and this still remains the most common way of sampling. There are lots of different types of nets, some very simple and some very complicated. Some have very fine mesh and are good for collecting small animals (e.g. copepod nauplii, see posts by Michelle), and some have very coarse mesh and are good for collecting things like shrimp, or small fishes, that really are good swimmers. We have to tow the net quite a bit faster to collect animals that are good swimmers, because they can feel the net coming and and are quite good at escaping!

Cod end with plankton in a bucket

During the daytime, when there is sunlight on the ocean, they may also see the net coming, and be able to avoid getting caught. We are using two different types of nets on this cruise, and we are towing them in two different ways: (1) vertical tows of a 60 um mesh net to collect copepod nauplii (baby copepods), and (2) oblique tows of a bongo net (see picture), to filter larger volumes of seawater and collect larger animals in the upper ~ 350 m of the ocean. Oblique just means that we are towing the net at an angle (45 degrees), so the net is moving both along in the ocean horizontally as we are pulling it up towards the surface. We can filter more seawater this way, and collect animals that are relatively large and relatively rare. Once we get our nets back in, we rinse them and collect the plankton in our buckets (see picture of the collecting end on the net, which we call ‘cod end’). On this cruise we carefully split the catch of each net using a Folsom Plankton splitter (see picture of me in the lab splitting a sample).

Another way to catch plankton is by using the CTD Niskin rosette. Using the CTD rosette, we are able to collect and study plankton from particular depths in the ocean. This is important, because the ocean changes dramatically across depth, very much more so than across the surface of the sea (horizontally). Animals often like to live only at certain depths, and are very good at maintaining themselves where they would like to be in the water column. Most animal plankton are too rare to sample with a CTD rosette. We are using it to sample copepod nauplii, which are often very much more abundant than the adults.

There are yet other methods, which we don’t use on this cruise. For instance, while scuba-diving. Many planktonic animals are gelatinous, and are therefore very fragile and hard to collect without damaging them. Jellyfishes are one good example, but there are many other types of gelatinous plankton that you might not be familiar with, like ctenophores, or siphonophores (ever been stung by a portuguese man-o-war? that’s a siphonophore). In order to really see these animals as complete organisms, you need to collect them by hand.

Slow start

We had a slow start to the day today. Our 03:00 am bongo tow was not terribly successful, and we didn’t collect very many animals of interest (that we are targeting in our studies). That was a disappointment! However, because we didn’t have a lot of organisms that we wanted for our scientific studies, we had a bit of time to focus on other things, like imaging some of the animals we did collect. So today we were able to capture beautiful images of 2 of our target species, Pleuromamma robusta and P. gracilis, that are common copepods in open ocean environments.

These species are important in ocean biogeochemical cycles, because they migrate every day between the surface ocean (at night) and the twilight zone (ca 500 m). While they undergo these migrations, they move carbon and nitrogen from the surface ocean into the ocean’s interior and play a role in sequestering carbon from the atmosphere into the sea. Pleuromamma gracilis is a member of a cryptic species complex, and we are collaborating now with Janet Grieve (NIWA, New Zealand) on systematic revisions of this group, with descriptions of several new species.

In the afternoon, we also caught a Velella velella in our nauplii net. This funny jellyfish-like creature lives on the surface of the ocean, and has a clear sail that sticks up above the sea surface. The animal is then pushed by the wind across the ocean like a real sailor. This beautiful blue color is found in many of the animals that live at the air-sea interface.

We’re off!

We finally left the dock at Immingham last evening, and its wonderful to finally be at sea. Immingham feels a bit like the industrial armpit of England, with the view around the research vessel James Clark Ross dominated by oil refinery smokestacks and enormous cranes for loading containers onto ships. In port, the smell of oil and gas pervades the air and seemed to stick to your skin, and I had the distinct impression that spending a lot of time in that place would shorten my lifespan. It feels good to be out in the clean air of the North Sea, with the sun penetrating through the clouds and shining on the surface of the sea. We cannot see land, even though we know it is there, due to the cloak of fog that hangs over the coastline. There are a few other boats on the water, not many, and its feel that we are quite alone. We sail now towards Portsmouth, where we will stop for a morning to take on more ship’s oil, before finally heading out over the continental shelf and off into the open sea. Finally! We are off on our adventure. Everyone is ready to begin. We have been in port in Immingham since Sept 18 (for 4 days), working on ‘mobilization’, as the Brits call it. The science party has been loading gear, setting up and testing their instruments, and plumbing seawater lines into incubators for experiments while at sea. The science party is a diverse group this time, both in terms of our countries of origin, and also in terms of our scientific interests. We have scientists working on topics ranging from atmospheric chemistry, measuring fluxes of gases across the air-sea interface, to studies of picoplankton abundance and distribution across the ocean, as these are globally-important, but tiny phytoplankton, as well as our ‘zooplankton group’ that will collect planktonic animals for population genomic studies and also run some experiments while at sea. Many, but not all, scientists on board are part of a long time series program, the Atlantic Meridional Transect Programme, that aims to track changing ocean biogeochemistry on interannual and interdecadal time scales. Several of these scientists have been to sea on this cruise every year for the past 5-10 years, or even more. They are old hands at this work, and are very familiar with the ecology of this region of the global ocean. They are a good group to work with. I am excited to be here, and am looking forward to getting started.