Tag Archives: Plankton

Door #15 Twinkle, twinkle, little animal?

Yesterdays door of this calendar introduced the bioluminescent animals of the deep sea.
In the parts of the ocean where sunlight reaches (the photic zone), production of ones own light is not common. This is because it is costly (energetically), and when the surroundings already are light, the effect is almost inexistent. An exception to this is the use of counter-illumination that some animals have: lights that when seen from underneath the animal camouflages them against the downwelling light from above.

But what then with the ocean during the polar night? Last Thursdays blog told the story of the dark upper waters during the constant dark of the arctic winter, and how the quite scanty light of the moon is enough to initiate vertical mass movements. Another thing we see in the dark ocean is that processes that at other latitudes are limited to the deep sea come up nearly to the surface during the polar night.

So – in the Arctic winter we don´t have to use robots and remote cameras to observe biioluminescent animals: we can often observe them using normal sport diving equipment or even from above the surface. A very recent study (Cronin et al, 2016) has measured the light from different communities in the Kongsfjord of Svalbard during the polar night. They found that going from the surface and down, dinoflagellates produced most light down to 20-40 m depth, the lighting “job” was then in general taken over by small copepods (Metridia longa). Most light was produced around 80 m depth.

Bioluminescent dinoflagellates shining through the winter sea ice in Kongsfjorden. Photo: Geir Johnsen, NTNU

Bioluminescent dinoflagellates shining through the winter sea ice in Kongsfjorden. Photo: Geir Johnsen, NTNU

It is possible to recognise different species from the light they make; a combination of the wavelength, the intensity and the length of the light-production gives a quite precise “thumbprint”. If we know the possible players of the system in addition, an instrument registering light will also be able to give us information about who blinks most often, at what depths, etc. Cronin and her coauthors have made a map of the lightmakers in the Kongsfjord.

Bioluminescence profiles from Kongsfjord. Figure 3 from Cronin et al, 2016

Bioluminescence profiles from Kongsfjord. Figure 3 from Cronin et al, 2016

This is all well and good, but the next question is of course WHY. There can be several uses for light, and we can bulk the different reasons into 3 main groups: Defense, offense and recognition.

Different strategies for Bioluminescence. Fig 7 from Haddock (2010), redrawn for representation of the Polar night bioluminescence by Ola Reibo for the exhibition "Polar Night"

Different strategies for Bioluminescence. Fig 7 from Haddock (2010), redrawn for representation of the Polar night bioluminescence by Ola Reibo for the exhibition “Polar Night”

 

The bioluminescent cloud from an escaping krill. Kongfjorden, during the Arctic polar night. Photo: Geir Johnsen, NTNU

The bioluminescent cloud from an escaping krill. Kongfjorden, during the Arctic polar night. Photo: Geir Johnsen, NTNU

Defence has already been mentioned above: the counterillumination against downwelling light is helping an animal defend itself against predation. Some will leave a smokescreen, or even detach a glowing bodypart while swimming away in the dark, and others blink to startle the enemy or to inform their group-mates that an enemy is getting close.

 

 

Offense is mainly to use the light to get food (this is typical angler-fish-behaviour), and recognition is very often about flirting. Instead of flashing your eyelashes at your your chosen potential partner, you flash some light at him or her…

Thursdays are about amphipods in this blog, so here they come. Bioluminescent amphipods are present mainly in the hyperiid genera Scina (a Norwegian representative of this genus is Scina borealis (Sars, 1883).) Hyperiids are amphipods that swim in the free watermasses, like most other bioluminescent animals.

The bioluminescent amphipod Scina borealis (Sars, 1893). The added stars indicate where the bioluminescence occurs. Original figure: G.O.Sars, 1895.

The bioluminescent amphipod Scina borealis (Sars, 1893). The added stars indicate where the bioluminescence occurs. Original figure: G.O.Sars, 1895.

Crustacea use more different ways to produce bioluminescence than most other groups – this points to a possibility that the use of bioluminescence has evolved several independent times in this group. So the copepod Metridia longa will use a different chemical reaction than the krill, and the amphipods use again (several) different reactions. Some research on the bioluminescence of amphipods was undertaken already in the late 1960s, where P Herring collected several Scina species and kept them alive in tanks. There he exposed them to several luminescence-inducing chemicals and to small electrical shocks, to see where on the body light was produced and in what sort of pattern. He reported that Scina has photocytes (lightproducing cells) on the antennae, on the long 5th “walkinglegs”, and on the urosome and uropods. They would produce a nonrythmical rapid blinking for up to 10 seconds if attacked, and at the same time the animal would go rigid in a “defence-stance” with the back straight, the antennae spread out in front of the head, and the urosome stretched to the back. This definitely seems to be a defence-ligthing, maybe we should even be so bold as to say it would startle a predator?

Anne Helene


Literature:

Cronin HA, Cohen JH, Berge J, Johnsen G, Moline MA (2016) Bioluminescence as an ecological factor during high Arctic polar night. Scientific Reports/Nature 6, article 36374 (DOI: 10.1038/srep36374)

Haddock SHD, Moline MA, Case JF (2010) Bioluminescence in the Sea. Annual Review of Marine Science 2, 443-493

Herring PJ (1981) Studies on bioluminescent marine amphipods. Journal of the Marine biological Association of the United Kingdoms 61, 161-176.

Johnsen G, Candeloro M, Berge J, Moline MA (2014) Glowing in the dark: Discriminating patterns of bioluminescence from different taxa during the Arctic polar night. Polar Biology 37, 707-713.

Photo: P Kohnert

Plankton People

Finally!!!!!! Today was the day for the plankton folk to rule the Porsild, and boy did we rule! We set off at the crack of dawn (or around 8 am…). To our surprise breakfast was waiting for us, despite the early hour. Thanks to the troopers Anne Helene and Perpetua, who got up at 6.15 to prepare that for us!

The group that headed out was Peter K., Sandra and Josefin, who were all on the hunt for plankton. But we also brought our super translator, Jakob, and Jeroen had the duty of assisting and entertaining.

At first the weather was looking promising. The sun was shining and the water was calm, however as soon as we came out onto open water the waves got significantly bigger. The mighty captain of Porsild decided that conditions were too rough for our planned destination, and so instead he took us to an alternative spot. As Peter had some specific criteria for catching his beloved pteropods (planktonic snails), we needed to find a spot were the depth was a minimum of approximately 200 m. As some pteropods migrate down during daytime to avoid predators, the plankton net needed to go down to ca. 150 m.

As Josefin had only recently learnt that the water hose on board collected its water from 3 m depth, her surface phytoplankton samples were extremely easy to obtain!!! She could simply put her Barbie-sized phytoplankton net under the hose and filter out the plankton.

Photo: J Sefbom

Sandra and Josefin – happy plankton samplers

At the spot, the big zooplankton net was thrown over board and hauled at 150 m for a good while. Peter was full of joy and high hopes for his samples. The excitement was building up as the net surfaced, but…as it was pulled back on board the boat, Peter noticed that the collecting bottle attached to the bottom of the net had been smashed into pieces!!! Despite Peter hiding behind his sunglasses we could tell that the tears were building up. Jeroen stepped in and calmed him down by whispering comforting words in his ear. Søren, our boatman, then suddenly appeared from the cabin holding a big role of duct tape. We could all feel the hope beginning to return. Peter wiped away his tears and stepped into the cabin. He duct taped the life out of the small bottle, and back into the water it went. As always, third time is a charm, and Peter could finally retrieve his pteropods. Søren received a massive big hug from the overjoyed Peter. In the catch there were the expected two species, namely Limacina helicina and juveniles of its specific predator Clione limacina. Generally pteropods have attracted special interest being among the species that are considered to suffer most from increasing ocean acidification, but still little is known about their phylogeny and evolution…

Photo: J Sefbom

Sandra and Jeroen enjoying the sun between samples

Next up was Sandra. Sandra wanted to retrieve zooplankton samples from 25 m depth. Although our quick-mouthed and cheeky friend had been surprisingly quiet during the rough ride, it was now her time to shine. She quickly returned the zooplankton net into the water and gave strict instructions on the depth and length of the tow. As Josefin had buttered up the captain with pieces of chocolate, he was finally willing to follow the strict orders, marvellously translated by Jakob. In the end Sandra got the samples she needed without having any further problems.

Last but not least, Josefin needed to collect phytoplankton samples from 40 m depth. This was carried out with the help of diligent Søren and… a water sampler! The 60 litres of water that were collected, were then concentrated to a mere volume of 15 ml!!

On our way back to the harbour winds and waves had picked up. Since Jakob had almost accidently dropped Peter’s samples back into the ocean, Peter was now guarding his buckets of planktonic treasures. He set up camp with a minimum of 1 m radius, which no man was allowed to pass. Unfortunately he had forgotten to bring lids, so for the last minutes of the cruise he had to hold the buckets in his hands to prevent the content from being spilled over the deck.

Photo: J Sefbom

Peter and the Plankton

After 3 hours we arrived back at the harbor without any further incidents. All in all, the trip was extremely successful.

Written by: Josefin (Gothenburg University) and Peter (Bavarian State Collection of Zoology)

Featured image: Clione limacina – commonly known as ”Sea Angel” (photo: Peter Kohnert)