Happy anniversary Plankton Portal 2.0!

Blog post by Jean-Olivier Irisson

A year ago, we announced Plankton Portal 2.0, which featured a more streamlined design, a simpler tagging interface, and most importantly, a whole new dataset. Since then, this new data from the Mediterranean Sea has spurred a lot of interest and plenty of new questions. Participants on the site were surprised by the difference in size of everyone’s favourite jellies, the Solmarisidae (Solmaris rhodoloma in California, Solmissus albescens in the Med), which are much larger! Siphonophores also seem more abundant there. And the Mediterraean data came with brand new categories of organisms to mark: nice and cute medusa ephyrae (i.e. baby jellies), elegant Pteropods and the elusive fish larvae.
In total, as of last Sunday, 368,361 organisms were marked, on 50,519 distinct images. Through time, the classifications were marked by two peaks in activity: a huge one when the new version was announced through a mailing to the Zooniverse community (thanks everyone!) and another one when we pushed for 1,000,000 classifications in total, to celebrate Jessica’s PhD defense. When we zoom in, we see activity fluctuating around 1000 and now 500 classifications per day. This is still great (but coming back to 1000 would be even better! 😉 ).
time_series
time_series_zoomed

 

The top 11 contributors, all authors of over 5000 classifications each, are displayed below. If you made this top 11, we owe you special thanks (and probably a beer too). We hope you will stay interested and involved in this project. If you did not, you should really not be disappointed because all other volunteers still collectively account for 60% of the classifications; so you matter very much! Hopefully all of you will be happy to see some of the outcome of your work below.
who

 

Time for a bit of science! The most common classification was… nothing, empty, zero, zlich, zip… Well, you get the idea. Indeed, when we film the sea, we most often see nothing (nothing living at least). Even though we pre-selected potentially interesting frames for Plankton Portal (the ones having some kind of large object in them), about a third of your classifications did not contain any organism we were interested in. In real life, the proportion of dead detritus vs. living organisms is more around 95% vs. 5%, so our pre-filtering still avoided you a lot of blank frames! In terms of organisms, the 10 most abundant are shown in the figure below.

what

 

Doliolids, Copepods, and Radiolarian colonies dominate the rest. We immediately noticed, when we shot the images, that Doliolids were particularly abundant. Those organisms are very effective filtering machines and they may therefore have an impact on the density of smaller organisms, in particular unicellular algae. The relative abundance of Copepods and Radiolarian colonies is to be interpreted carefully: Radiolarian colonies can be large and span several frames (therefore increasing the total count) and Copepods are likely under-estimated because we mostly see the larger ones with ISIIS, and they are not the dominant ones in the Mediterranean. Still, it echoes nicely a recent Nature paper by Tristan Biard (a contributor to PlanktonPortal’s talk, under the username Collodaria), which showed that Rhizaria (a large taxonomic group to which Radiolarians belong) can be equivalent in biomass to Copepods, who were previously thought to largely dominate the plankton. These findings were also based on in situ images, because these fragile Rhizaria cannot be collected with nets.

 

Finally, the images in the Mediterranean were collected along transects (i.e. straight lines) perpendicular to the shore. We were interested in how organisms were distributed along a gradient between coastal and open ocean conditions. In the plots below, the coast is on the left, the open ocean on the right and the vertical direction is depth (top: surface; bottom: 100 m depth). So you basically see a “slice” of water along which ISIIS undulated. The size of the dots is proportional to the number of classifications recorded. You can immediately notice that Doliolids (first plot) are concentrated near the surface, and fish larvae (second plot) even more so! This is a surprising finding for fish larvae, which sometimes ended up in concentrations of over 10  individuals per cubic meter, a number much higher than what was previously observed elsewhere, with conventional plankton nets.
distrib_doliolid_w_icondistrib_fish_w_icon
Radiolarian colonies, on the opposite, tend to be concentrated in mid water (see figure below). Within this messy picture, some structure seems to emerge. Indeed, the white lines on top of the plot are contours of the concentration of Chlorophyll A in the water (i.e. of the amount of unicellular algae). If you look carefully, you will see that those lines are moving up, towards the surface, as we travel offshore (from left to right on the plot). This is actually well known in this region. What is interesting is that the radiolarians seem so follow the same pattern, and that higher concentrations of colonies sit on top of this high Chlorophyll region. Something is definitely going on between these two!
distrib_radiolarian_colonies_w_icon
That’s it for now — thanks again to everyone for this wonderful year of activity! We apologise for not being as active as we would like to be on Talk. To that end, we thank the active moderators who take over this important responsibility. And finally, we thank Zooniverse for the great opportunity and community they created. Now, on to next year!
Advertisements

Copepods: Rice of the Sea

Of all plankton groups, probably most is known about the copepods. They represent a critical link in the food chain and are consumed by diverse animal community ranging in size from small fish, chaetognaths, and ctenophores all the way up to large whales (the right whale is a voracious copepod feeder). Because of their small size and importance as food, copepods are affectionately known as “the rice of the sea.” Copepods are effectively captured by plankton nets because they have hard exoskeletons, and scientists have good estimates of their abundances and distributions. Although copepods are all relatively small (0.5 mm – 5 mm in length), they comprise over 200 families and 10,000 different species.

CopepodsTogether

Examples of typical copepods. Note to the two large appendages on the top of the head with small sensory hairs

Copepods consume both phytoplankton and microzooplankton in two different ways: suspension feeding and raptorial feeding. Suspension feeding is relatively passive and performed by beating small appendages that draw a current through a feeding chamber. Copepods then select which particles encountered are food and discard others. Raptorial feeding is used to actively capture prey. Many copepods have small sensors on their first appendages to detect water disturbances produced by prey and also predators. They can use these relatively large appendages to “hop” through the water and capture an unsuspecting prey item or to quickly escape a predator.

Copepod reproductive strategies vary greatly and are adapted towards the ability to withstand the variable conditions that characterize the ocean environment. For example, many copepod eggs have the ability to enter a phase of diapause where they remain viable on the bottom for several months or even years, only hatching with conditions are favorable (high concentrations of food). Some copepods carry their eggs, allowing them to develop a bit before releasing them into the water column. The timing of copepod reproduction is especially important for the life cycle of fishes because most fish larvae depend on the recently hatched copepod nauplii for food. If there are not enough copepod nauplii present when fish larvae are abundant, there could be mass starvation events causing few fish larvae to reach their juvenile stage. Because of this, the copepod life cycle is extremely important to fish populations and overall ocean ecosystem health.

This image was taken from a thin layer near Stellwagen Bank offshore of Massachusetts, USA. Each one of the white particles is a copepod. The concentration of organisms in this image corresponds to ~400,000 individuals per cubic meter! That is some good eating for a right whale!

This image was taken from a thin layer near Stellwagen Bank offshore of Massachusetts, USA. Each one of the white particles is a copepod. The concentration of organisms in this image corresponds to ~400,000 individuals per cubic meter! That is some good eating for a right whale!

One of the most remarkable characteristics of copepods is their tendency to aggregate in discrete thin layers within the water column. Sometimes >90% of the copepod biomass will be confined these thin layers, which are a maximum of 5 m thick. ISIIS and other systems that sample on small scales are ideal for detecting these layers of copepods, and the function of the formation and dissipation of copepod thin layers is not well understood. Copepods have been shown to be attracted to strong changes in current direction and speed, potentially allowing them to feed at a faster rate within these zones (Woodson et al. 2005). The changes in environmental variables associated with aggregations of copepods are of great interest to marine ecologists. With your help, we can better understand how these extremely important organisms are distributed throughout our oceans!

References:

Johnson WS, Allen DM (2005) Zooplankton of the Atlantic and Gulf coasts: A guide to their identification and ecology. Johns Hopkins University Press. Baltimore, MD.

Woodson CB, Webster DR, Weissburg MJ, Yen J (2005) Response of copepods to physical gradients associated with structure in the ocean. Limnol Oceanogr 50:1552-1564