The zooplankton around the Falkland Islands are thought to play a major supporting role for species higher up the food chain, however so far very little research has been done into these organisms in this area. My PhD project aims to improve our knowledge about these species and their role within the Falkland Islands nearshore marine environment.
I arrived in the Falklands at the beginning of February, going from winter in Aberdeen to summer here! Within the first week I started to figure out some of the issues involved with collecting data, as our planned boat trip to collect zooplankton samples was delayed by several days because of the wind. I was able to explore around Stanley in this time though, including going over to Yorke Bay to see the gentoo penguins!
Despite the wind, at the end of my first week here, I was able to go out on the SMSG’s RV Jack Sollis with Jesse (one of my supervisors) so I could collect the February zooplankton survey. It was an incredible day – not only was there a large variety of organisms within the zooplankton trawls, including the potentially key lobster krill (Munida gregaria) and hyperiid amphipod (Themisto gaudichaudii) we also saw an amazing range of wildlife!
Image left : some black browed albatross in amongst other birds
Image right: A southern Giant Petrel with a Rockhopper Penguin
The zooplankton samples are collected using a bongo net, which allows two nets to be towed simultaneously, and these are towed through the water for a period of time, during which any zooplankton caught in the net will be collected in the ‘cod end’ (essentially, a collection jar at the end of the net where anything larger than the mesh size gets caught), which can then be sieved out and preserved for further analysis.
Image left: Dr Jesse van der Grient & myself having a look at the Bongo nets
A major objective of my project is to identify which species of zooplankton are found around the Falkland Islands, and what role these organisms play in supporting the wider ecosystem, and with the number of organisms we saw while out on the boat (including penguins, albatross, other seabirds, whales and dolphins) I’m hoping that my research will provide a better idea as to how important the zooplankton is in supporting the larger pelagic food web, including these larger organisms. Understanding the seasonal patterns and distributions of the zooplankton, as well as their life history patterns will have a vital part of this, through linkage to the patterns and distributions of higher organisms that are dependent on the coastal and offshore Falkland environments. Throughout the multiple transects and sites that zooplankton was collected and sieved from, I was constantly impressed by the timing of the Peal’s dolphins. They must have been curious about the science going on, as they consistently circled the boat while we were sieving samples and left as soon as there was a moment to stand back and watch them play! All in all, it was an amazing first sampling trip, and a great introduction to the ecosystem that I am studying.
After collecting the samples, I have spent a lot of time up in the Agriculture Department to sort through and identify what organisms I am finding in my samples. On the days following the sampling I had to work quickly to get a look at the fish larvae (ichthyoplankton) samples collected, as these were stored in seawater so that I could make a note of the key features before were affected by the preservation methods. There’s a huge range of types of organisms I’ve found so far, some of which are familiar, and I can match to a species, but far more that will take more searching through available literature to identify using key morphological features. As samples are being collected throughout the year, I will be able to compare the changing seasonal abundance of these different species. I am here in the Falklands for a few more months to continue to collect samples and identify the zooplankton species, before returning to Aberdeen, where I will take some of my preserved samples and begin the process of DNA barcoding – a method that can be used to identify and differentiate between species that are not clear by just looking at the physical characteristics. Using both of these methods (morphological and molecular identification) I hope to improve our knowledge of what zooplankton species are found in the Falklands and how important they are for the species of commercial interest.
Part of my project is also focused on looking at the life history of the lobster krill in more detail. Although we collected a few individuals during the February sampling, I would need more to be able to start this section of work. Something that is well known about this species is its swarming behaviour – this unfortunately makes it difficult to target when sampling using the bongo nets during the zooplankton trawls, but it does mean that if they are observed swarming somewhere that they can be ‘easily’ targeted. In mid-February we were alerted that there were loads of lobster krill swarming at FIPASS, so we rushed down with a net and a bucket, in the hopes that we could just scoop them up with little hassle. As is often the way, it wasn’t nearly as simple as we had been hoping. The lobster krill were swarming in large numbers, but quite a long way down from where we could attempt to get them from. My first attempt included tying rope to both handles of a bucket in the hope that I could drop the bucket, angle it to sink it into the water and then haul up a bucket of krill. Despite multiple attempts and angles, this method had no success. Eventually, we acquired a long metal pole and duck taped our net to this pole and gradually were able to collect some individuals. Although I’m sure I looked ridiculous while trying to get the krill, I had a lot of fun, and the trip was successful. I’ve been able to collect some data from the individuals caught, including measuring their carapace size, identifying if they’re male or female and whether they have any parasites. Hopefully over the time I’m here I’ll be able to collect some more and add to this data set, especially as so far I’ve only been able to collect some of the smaller individuals, and we know that they grow a bit more before settling as adults.
Due to the recent stormy weather, we had quite a few unusual species that are not normally associated with the zooplankton in the nets – my personal favourite of these was a starfish that was probably 10cm across! Considering most of the things I’m anticipating catching as part of my PhD project need to be identified with a microscope, this was a very unexpected catch. It’s fascinating to already be able to see seasonal differences, even just looking at the samples collected in the last two months! I can’t wait to sort through the other samples collected and continue to collect more zooplankton to continue to build up the knowledge of how these species change in abundance and importance throughout the year.
Image left: Gelatinous species under the microscope
Image right: My favourite catch of the day: a Starfish!
