Welcome to the second talk
of Shared Science.
I would like to comment before starting
that these talks are authorized to be public,
they will be on Repositorio Institucional of the university, Acceda.
They are now also available on the Youtube channel
of the Biblioteca Universitaria.
Here is our first speaker,
Federico Maldonado, who will go down in history.
The idea is that we all know
a little of what is done in
each group of the faculty,
which researches are made,
to know each other
and to share it, because it is not only the sea
but also some do coastal things
and we want them to participate.
We also want to know
if you have any doubts as well or you want
to contribute, to share it,
because sometimes we are too focused on
respiration, in Fede's case, or in my case
on currents and we forget about the rest
and maybe things from the outside
could help us.
The idea is also to encourage students
to come to these talks,
to show the use of what you are learning.
And Avelina is in charge to inform you.
This was for you to see what is going on.
Then we have here our second speaker,
that will talk about
migration and trophic ecology of vertical migrant
fishes that dominate subtropical Northeast Atlantic.
Involvement on active carbon flux.
I believe that you all know him,
Alejandro Ariza, he studied biology
in the Universidad de La Laguna.
And he specialised in marine biology,
and there he began with his research;
that he later continued in th ULPGC,
signed by Santiago Hernández León.
He works now on inter-zonal migrants
that live in mesopelagic waters
and I quote what he told me before:
"We are interested in the exportation of carbon
that those organisms do when they migrate.
This has to do with the biological pump
of the ocean, a complex mechanism
that the ocean takes CO2 from the atmosphere,
something that is very interesting in this
global change scenario that we are living in".
This is a little part of what he is going to tell us,
and he also works between
the ULPGC, with Santiago Hernández,
and the Instituto Canario de Ciencias Marinas
with Fernando Bordes Caballero,
in terms of acoustic and he has stayed
the last one in Norway,
in an institute working on
acoustics and he has just embarked
in the Ramón Magalef to work in the volcanic
crisis in El Hierro.
Nothing else Alejandro, it is all yours.
Thanks Avelina, you saved me a lot of explanations.
I want to say that in this work
other people has collaborated,
Rupert William Reuter, Fernando Bordes Caballero
from the Instituto Canario de Ciencias Marinas
and Santiago, the head.
The research of migration and trophic ecology
address the implication of these organisms
on the active flux efficience.
In this work we want to focus on this especially.
Well, let's start.
I would like to begin with this image,
this is an echogram,
where we can see a migration process.
What you can see down here is
the Deep scattering layer
and it is produced by the echo
that pelagic organisms make
that live between 400 and 700 mts deep.
What you see up here is the migrant layer,
and its a part of the same organisms
that emigrate when it gets darker
to eat epipelagic plankton in the in the surface.
When the dawn comes, they come back
again to deeper layers to protect themselves
in the darkness from predation.
This is called diel vertical migration,
that is how in scientific articles is seen.
And this phenomenon happens globally
every night.
This has a great importance in the trophic
connection between organisms
of the surface and the deeper ocean.
That is why it has strong implications
on carbon.
These animals eat in the surface
the organic carbon produced there,
they transport it to intermediate layers,
and they release it in form of
carbon dioxide when they breath
or these types of organic carbon
when defecating, excreting or when they are predated.
This active transportation of carbon
by the migrators,
is what we called active carbon flux,
and with another important mechanism,
that is the gravitational flux o passive flux,
both are part of the biologic pump of carbon;
that is a complex system
that takes carbon dioxide from the atmosphere and now is more important
due to climate change.
Who are these migrators?
Traditionally from the perspective of the
biogeochemical oceanology,
when we talk about migrators and active flux
zooplankton is the first that comes to everyone's mind.
I would like today to talk about another type
that is the one that I work with, the micronekton;
that are mainly fishes, crustaceans, cephalopods
between 2 and 10 centimeters of size.
They are migrators, like the zooplankton
however they have been excluded
of the active flux counts.
This is like this, because
these animals escape easily
from the nets that are used for plankton.
They evade them, they do not escape.
Moreover they are little enough to
escape from the commercial trawl nets.
The last ones, although they get something,
they are rare in oceanographic campaigns,
because they consume a lot of time.
That is why they have been excluded from the research
of active flux.
Nevertheless we think that it is important,
because micronekton is able to
control 5-10% of the diary production of zooplanknton.
Furthermore, the majority of this micronekton is
formed from the Myctophidae family
that 70% of the migrant biomass are myctophids,
and a 75% of the mesopelagic capture
in a trawling, they are also these fishes.
The global stock is estimated at 500 to 600 million tonnes.
and probably understimated,
because escapes are not considered.
That is why we think that myctophids must
represent an important route in the
exportation of organic carbon to
deeper waters.
One issue that has always been a hotly debated one is
the efficiency of the exportation of carbon
of the migrators, due to that
range that they do in these migrations.
Because they are the inter-zonal migrations,
represented in red,
the ones that get through the barriers,
barriers to the exchange of water bodies;
are the ones that are considered efficient
in the carbon exportation.
Trying to move it from a compartment to another in the ocean.
Moreover, the time that they need to come back to the deep
layer must be smaller
than the time that need the food
to be processed and to be evacuated.
If we want that a minimun of what they consume
in the surface to be transported to deeper waters.
That is why studying the migration
and the food chronology is important
to study the active flux.
This is the way we have worked on those two issues,
along with diet, which we have also worked on,
and the daily ration
the amount of body weight they ingest.
We have done this in Hygophum hygomi,
Lobianchia dofleini, two myctophids
that dominate the Subtropical Northeast Atlantic.
As I told you, micronekton does not abound
too much in oceanographic campaigns,
thanks to some cooperation with the
Instituto Canario de Ciencia Marinas thanks to Fernando Bordes.
We worked with help
coming from some campaigns of fishing
prospections, that were done between 1997 and 2002,
with a poop trawling, using a trawling
comercial semipelagic net.
We chose sets done in Fuerteventura,
because those catches were from different times.
This is appropiated for this study
of mmigration because it is a
phenomenon that occur in a 24 hours cycle.
We did not take every set that was done.
We used only the ones interesting for the study,
we prefered to work with epipelagic sets
that we defined between 0 and 150 meters of depth.
We got 9 sets,
in a 24 hours cycle.
The black colour represents the night hours
and blue the light hours.
The mesopelagic sets were defined
between 300 and 700 meters of depth.
We got 6 sets,
distributed this other way in 24 hours.
We took all data of abundance of these two
species, we standardised it to 10.000 cubic meters,
and we computed it in a histogram
in 24 hours
to visualise the migration phenomenon well.
For us in food chronology,
we could not use the samples from Fuerteventura,
that we have the abundance data,
but the samples were distributed in
museums around the world.
We have ordered them and we have them already in laboratory.
We are working them, however
we do not have yet the final product.
Here are the data from
other zone where we analyse
food chronology with the same methodology,
in which we studied individuals
of the mesopelagic layer
a bit before the nightfall
some hours befor the next migration.
We studied their stomach contents.
These individuals are considered premigrators.
We also studied the stomachs of individuals
that we consider postmigrators,
that were caught in the epipelagic layer,
some hours after the nightfall.
This is the procedure of extraction
from the stomach of the myctophids.
This is the look of the
stomach of anLobianchia dofleini.
This is even smaller than a
grain of rice, so we have to be careful while dissecting it.
This is an open stomach.
In this case is really full.
I selected this one because it is very fresh
and it is not what I normally found, but
I chose the one with the freshest content
because is better for the picture,
we can see them perfectly.
It is completely full of copepods.
And this is the compound eye.
Then for the food chronology study
we used two scales.
A stomach fullness scale,
that went from the stage 0
where the stomach was full,
to the stage 3, where it has been totally full.
In addition to considering the filling of the stomach,
we consider the roughness state of
the internal pallets of the stomach,
when the stomach is very full, the roughness disappears.
And as we study the digestion of contents
we did it only on copepods, because we
assume that each group must have
a different rate of digestion,
to avoid this mistake, we only talk about one group.
The copepods because they are the most commonly found,
Then stage 1 is a fresh copepod,
in Stage 2, has the appendices
broken, but the main part of the body is well preserved;
and in stage 3, it has the main part
of the body very deteriorated.
On both scales what we want to know
at what time are they eating
and how long it takes them to digest the food.
In order to study the diet, what we did is to take
contents of animals on the surface
at 12 p.m. because they were eating at that time.
Then they had the fresh contents,
y esto venía bien para estudiar
the contents rather than the digested ones.
And for the study of the daily ration,
we look at stomachs listed as
maximum filling stage,
and the data is expressed as a percentage
of the animal's body weight with what it is ingesting.
Well, let's see the results.
These are the results of abundance.
In the mesopelagic layer and in the epipelagic layer,
for Hygophum hygomi and Lobianchia dofleini.
These shaded areas represent
the night periods.
The first thing we see is
that even though daylight fishing was analysed
in the epipelagic layer,
as expected did not register
neither species.
Not even the first
half hour after the nightfall
tampoco aparecen, se demoran un poco más en subir.
This 0 individuals,
and between 9pm and 1pm,
both species have the highest abundance.
Moreover, what we see is that
in the case of the Lobianchia dofleini especially,
se ve que hay una
progressive decrease in abundance
as the night progresses
and with a peak of abundance
in the lower layers.
The pattern of no individuals here
and at night they appear,
is a normal migration pattern
of night migration
al anochecer en sentido ascendente,
which has been well documented for years.
And the issue of abundance growth
together with late onset in lower layers,
may be a phenomenon
of midnight sinking.
This is a hypothesis postulated by Pearre,
in which he states that
these individuals do not migrate in a massive way,
do not descend in a massive way at dawn,
but they do it in a way,
asynchronous in some way
individual as they feel satiated.
When their stomachs are full, they decide to go down.
As this is an individual phenomenon,
it does not register very well with the
traditional acoustic techniques.
That is why this has not been discussed until now.
If we look at the captures of the mesopelagic layer,
we see that there is presence by day and by night.
We are interested the most in
is the presence during the night, because
it may be the result of this sinking.
But also a number of individuals
who are simply not migrating.
If you remember the image we saw
at the beginning of the talk,
when the migrant layer rises during the night,
the deep layer does not disappear.
This is not new, it has been known for a long time.
It used to be thought that the
species in this layer were non-migratory.
The presence of these individuals means that
are migratory species that choose not to migrate.
What we are interested in is knowing
what the motive is and what they are doing there.
If we look at the results of stomach filling,
we see that as we expected,
individuals who we consider to be
migrating on the surface,
most of them have full stomachs and
seedlings; this is due to what we already know
that they eat at night on the surface.
However, organisms in the mesopelagic layer
are just hours away from migrating again,
we hope they had empty stomachs,
because most of them have full stomachs.
We found this rather strange
and in the bibliography you will find
some references that
they eat during the day in the mesopelagic layer,
as postulated by Pearcy for myctophids in the Pacific.
However, on the basis of the digestion results,
we see that individuals do indeed,
that are migrating are at the surface,
as most of them have stomachs
full of fresh prey.
If not, let alone in a state of advanced digestion.
In case of theLobianchia dofleini,
we find less prey, less copepods,
because they ingested fewer copepods.
But there are still more fresh prey,
no prey at maximum digestible state.
This indicates that they are actively eating there.
In the case of individuals,
that were about to migrate,
we see that those stomachs were full,
but most of them
was full of prey
in a high state of digestion.
So much so that in theLobianchia dofleini
so digested that we were unable to quantify copepods.
There was a digested mass
which could not be quantified, and therefore
the digestion scale methodology
has not been efficient with this species.
For the future we will consider using
imaging techniques to
quantify the area of this digested mass.
But in any case, the results suggest
that if there are no fresh prey,
evidently they do not eat during
the day in the mesopelagic layer.
However, the question we asked ourselves,
what worried us most was,
why stomachs are full and very digested
just before the next migration.
The most plausible explanation for us
is that these contents come from
the last migration they carried out.
We do not know when this last migration took place,
whether it was 1, 2 or 3 nights before is impossible to know,
but we know that this implies that the system
digestive and evacuation processes are very slow.
And something that I think deserves more research,
because it has implications on the
active flux issue.
This is in line with the theory of
Sutton and Hopkins, which says that
the migrant population is divided into
migrants that feed at night,
and individuals that choose not to migrate
because they are in a post-nesting state.
It also fits with the hypothesis
of Pearre, which states that not all individuals
migrate, only those that feel hungry go up.
They don't all go down at the same time, if not
asynchronously as they are satiated.
These are the results of the diet, in which
mainly it is seen that the food
are copepods, followed by amphipods,
and euphausiaceans.
and the Lobianchia dofleini,
eats copepods and euphausiids interchangeably,
and also some ostracods in smaller quantities.
The daily rations we saw that
2% of the body weight of the Hygophum hygomi
is what it eats per day;
and theLobianchia dofleini is 1.34.
This is close to the values
that Pusch obtained in the same area,
here near the Canary Islands for the same species.
What implications does this have for the active flux?
What I said was the important thing about the job.
The results suggest that these myctophids
return to the deep reflection layer,
just after they feel satiated.
When they fill their stomachs they go down.
Moreover, they seem to spend a lot of time digesting.
This implies high efficiency in the
export of carbon to deeper waters.
Moreover, if we consider that this family
constitutes 70% of this migrant mass
and mesopelagic mass,
we can assume that myctophids
probably represent a part of the
very important of the active flux.
Only as an approximation,
to put some values,
using a migrant biomass value,
in terms of carbon,
calculated by experts
in the Canary Islands area,
obtained a very conservative value
of migrant biomass of 158.2 millimoles
carbon dioxide emissions per square metre per day.
If we correct this with the fact that 70% of biomass
are myctophids, and that
ingest 1.76% of their body weight.
It is a value we have obtained from the
value I have shown above.
We obtain that only myctophids and only
considering the active flux of the digestive tract,
are exporting 1.83 millimores of carbon
square metre per day.
I do not know you can imagine whether it is too much or too little,
I have put some values around here to see
what is the importance of this value.
If we compare it with what they are exporting
migrators, only the zooplankton part,
in the Canary Islands is 0.33 and
in Bermuda is 0.17.
Micronekton values are much higher,
and yet it is studied more for active flux.
Considering micronekton values,
the same community I work with, but
derived from the consumption of zooplankton.
Hernández-León in 2010 argued that
the Canary Islands, in a scenario
not very productive, had values between
1.6 and 2.8, close to the value I get,
that seems to fit the 2 methodologies
to estimate the active flux.
And in a bloom scenario, of course
exceed these values.
And well compared to the other one
great mechanism of the biological pump that
is the gravitational flux.
In the Canary Islands, work by Neuer,
values were obtained for both a scenario
very productive and unproductive,
had lower values than ours.
There is also as yet unpublished data from
Hernández-León in the Canary current,
above the archipelago.
The values they hold are also lower than ours.
If we look at the values of
Alonso González et al,
this time in the south of the Canary Islands,
the Canary Current, but to the south.
We see that an area not affected by eddies,
has a value of 5.8, which is quite a lot
than our own, and even if we consider
eddy zones that are enriched
and bloom stage, these values are
obviously bigger than the ones we got.
And in the case of Bermuda and Hawaii,
what I wanted to show is that to begin with
these estimates vary widely.
It is evident, because there is a strong spatio-temporal
variety and depends on the methodology
that has been used.
In some cases our values are higher,
in other lower.
The important thing is that they are in the same order of magnitude
and they are also higher than the estimates.
All this suggests that this figure,
we believe, it is important enough
to begin to consider
to start conducting specific studies
for the estimation of the active flux of the micronekton.
To sum up come the conclusions,
is that the species of Hygophum hygomi and
Lobianchia dofleini, the epipelagic abundance
during a 24-hour cycle,
showed that they perform vertical migrations
normal at dusk, and that
its presence, well above the pycnocline,
is showing that this migration is inter-zonal.
The decline, in particular of the Lobianchia dofleini,
and the abundance in the epipelagic layer
overnight, together with
their subsequent presence in the mesopelagic layer,
suggests that they are doing midnight sinking
after filling their stomachs.
And the predominance of fresh prey
in both species at night
in the epipelagic layer, showed
night-time feeding in surface waters.
Both species showed that their stomachs
were full and well-digested, just before
the following migration, suggesting
that part of the population is not migrating
and that it is in a state of post-digestion,
and this implies a very slow evacuation system.
Much slower than
the time it takes for them to return to the deep reflection layer.
In addition, they mainly eat
copepods, euphausiids and daily allowances
were 2% and 1.34% of body weight.
To summarise,
that are vertical inter-zonal
migrants, that migration is inter-zonal,
that feeding should be at night in
surface waters; which are
dropping immediately after
ingesting the food and that the digestive system
is extremely slow.
These are all appropriate conditions
to think that myctophids are
exporting carbon to deeper layers
and that they should play an important role in the
in the biological carbon pump.
Simply put, what we want to say
is that we would like to recommend that in the
future active flux works,
his possibility should begin to be considered,
the micronekton is being considered,
which is still unknown in this field of work.
And I would like to thank all the
people who have helped me,
to the Faculty of Marine Sciences where I am doing my thesis,
the University of La Laguna, where I started my first digestion work,
Instituto Canario de Ciencias Marinas, in particular
Fernando Bordes for teaching me
everything about acoustics,
and the Minister of Science and Innovation.
And thanks to all my colleagues for
all moments on board, in the laboratory,
and for the time away from work that helps.
Thank you.
If you have any questions.
Please do not worry, because I do not expect you to
to be specialised in this.
And those questions that begin with
"this is probably nonsense".
are probably the best questions.
How do they know that those who migrate do not have
the digestive tract full and able to
leave the waste on the surface, in that superior
layer?
I do not know, maybe I did not understand.
You may say that only those who have
empty stomach.
When we see them feeding on the surface,
we find all kinds of stomachs, from empty stomachs
to full stomachs.
I guess it depends on the individual success that
have each finding food,
but the material is fresh.
It did not have time to be digested and so they did not evacuate.
There is a minority, a residue of digested material
much smaller than all that fresh mass.
Then most of the well-digested preys
are below.
So we think that not everything
but most of what they eat
it takes so long to digest that it already
when they go to evacuate are in the deep reflection layer.
Yes, it is just that I got stuck
because it takes so long, it takes so long, so
I did not remember you saying that
up there it was totally fresh what was
in the stomach.
If it takes that long to digest,
between rising again,
he still has a full stomach.
Yes yes, but you haven't found that.
You have only found if it was full
was about fresh things.
Yes, almost everything,
there is a tiny percentage.
Any further questions?
Do you consider
that in the value you give us? The 1.83.
This is still an approximation.
I understand and say that the majority
ingested goes to the mesopelagic layer.
We do not know the exact percentage.
This value is derived from the weight of
the contents at the maximum filling stage.
And as everything is fresh on the surface
and I only find myself digested
down there, I believe that most of them
removing a negligible part,
maybe there is something evacuated on the surface,
but I consider it negligible because of the quantity
very small amount of digested material
when they are on the surface.
A small correction should be applied.
But we do not know which one.
It is an approximation, this
is not a job that has been
que desde el diseño muestral
that the experiment was conducted to calculate
the active flux.
It is a by-product obtained from
other work that was carried out,
approximation
I am well aware that the value that
well...
You have to go deeper, just see that value is important.
It is important and
This needs to be explored further.
When you have the data that
of the museums
that are arriving now.
Your idea is to build a kind of time series
whether they nest more or eat more,
if more individuals go up for a period?
If you will allow me the samples that are there,
we want to see if there are areas
where there were periods of more or less production,
but I am not so sure we have
that we have that kind of sampling.
The Fuerteventura scenario may then be restricted.
We do not know in what,
well we know what time of year it was.
I mean, we do not know if we have enough
samples to make a series of the year,
We don't know if we have enough variety
of bloom or non-bloom scene.
We have to look at when all this comes in.
But in first instance only the area of Fuerteventura.
I think it is quite a productive area.
We have to do work on that.
I guess they are profiled
CTD, chlorophylls and we can see
whether they were in a bloom stage or not.
We were already thinking about it.
Any students?