Decoding the Science of Plankton
Though plankton are often too tiny for us to see in the water, they are a fundamental part of our marine environment. They are essential components of the marine food web and many marine animals rely on plankton for food – such as juvenile fish, small crustaceans, some sharks and whales and even other plankton themselves! The marine ecosystem would collapse without plankton, and therefore it is essential to study plankton so that we can monitor the health of the ocean. They are indicators for changes which are happening within our environment.
Plankton viewed from a microscope (Credit: https://www.britannica.com/science/plankton)
When monitoring how plankton changes over time, it is important for scientists to create a long-term time series within an area. This can help researchers observe changes in plankton numbers throughout the years. Unfortunately, getting consistent datasets over a long period of time can prove a challenge. Therefore, Maude Delap’s extensive collection of records and observations are incredibly important to marine science in Ireland. From her work, we can observe information on plankton communities from over 100 years ago!
Delap’s work on plankton dates back in 1895, when a team of three scientists from University College London came to Valentia Island to carry out a marine biological study. They had chosen to study Valentia due to the island’s westerly location and suitability for their study - and as they had heard of a certain Delap family who were avid naturalists. They arrived in April of that year and converted an empty house close to the shore into a laboratory.
Due to the success of the 1985 study, six scientists returned to conduct another, bringing with them their own trawler funded by the Royal Society. This time, they set up their laboratory in the Fishermen’s Halls in Knightstown. Of the six scientists, Edward T. Browne took charge of tow-netting the harbour for plankton species. By this point, Maude Delap had already developed an interest in the marine species of the harbour, so she and her sister Constance began to assist Browne in his studies. After the research team departed in 1896, the Delaps continued the tow-nettings. They sent their samples, preserved in formalin, back to Browne for examination. On top of this task, they also recorded the temperature of the sea and kept general notes on any changes in the species that they observed.
The Delap sisters carrying out research on the shore (Courtesy of the National Science & Engineering Plaques Committee)
Maude began compiling her own records of plankton in 1899 up until 1923. These records would go on to be published in three separate journals: Sea and Inland Fisheries Scientific Investigations and Irish Naturalist. Maude and Constance would row around the harbour towing a net for collecting plankton. they would bring these specimens back to her home-made laboratory called “The Department”. They would then have sieved the net full of plankton with seawater into a jar, leaving them with a soup like mixture of water, debris, and plankton.
At this time, it is not clear if Maude used to preserve these samples using preservatives such as formalin or if she studied them alive. Working with dead and live plankton samples each has their own difficulties. Live plankton zoom in and out of frame of the microscope lens, making it difficult to focus on them as they dart all over the frame. Preserved plankton often loses its colour and sometimes its shape, making it difficult to observe the small details which make some species identifiable. It would be time consuming alone just separating the plankton themselves from the plant material and sand.
Plankton net being towed behind boat.
Regardless of her methods, it’s safe to say that Maude would have spent hours looking down her golden microscope, observing the plankton samples she caught. It’s worth mentioning that identifying plankton is a very difficult task. Often the details which make plankton identifiable are very small and difficult to differentiate. Even in today’s age of technology and high-quality microscopes, plankton work can be incredibly time-consuming. It’s astounding to think that Maude was carrying out such precise work with such simple and few resources. The quality of detail in the sketches available in Maude’s sketchbooks show that she had an extremely keen eye.
Maude Delap’s microscope which can be viewed at Valentia Heritage Centre (Credit Dr. Nessa Cronin)
Throughout her study, she identified up to 64 species of plankton of many varying types including young forms of lobsters, starfish and sea snails. However, most of the species recorded are “gelatinous zooplankton”. These are the smaller jellyfish species or jellyfish-like species. She wrote to Browne often, who helped her with her identification of these species. It is possible that some of these species were incorrectly identified, or have since been re-classified, but all in all, it is an incredible feat for a self-taught planktonologist. It is also a lovely insight into the incredible biodiversity of the waters surrounding Iveragh.
Some individual plankton were large enough that she was able to collect them by hand or by using bell jars. Sometimes she would do land-based watches for blooms or shoals of plankton, as at times the abundance of species, such as the By-the wind sailor (Velella velella), would choke up her plankton-net, making it difficult for her to carry out tows. In total, between the years 1899 and 1923, Maude had dated records of plankton for 284 days in total. Maude notes that after 1910, her observations were irregular. It’s astounding to think that even in 1923, at the age of 57, she was still devoting her time to recording the changes of animals in the harbour.
Plankton net being hauled up
Even if she did not mention the exact date that she saw a certain animal, she still often mentioned how their numbers changed throughout the months. In the wintertime of many of these years, she notes how it was impossible to tow-net on the choppy water, but still included some observations that she was able to make. This is incredibly important as knowing how these numbers change on a yearly basis allows scientists to understand how species abundance changes with the seasons. Seasonality is vital in today’s study of biodiversity, as it is possible that climate change and human-based activities are influencing how species change throughout the year and this has the potential to upset many of nature’s delicate balances.
Maude Delap’s work on plankton provides an insight into how plankton communities functioned 100 years ago and deserves to be highlighted. From these observations, we can compare and contrast how plankton communities and abundance has changed over time. They are baseline datasets which can be used for future studies into Valentia harbour. Likewise, the sheer amount of time and dedication that Maude put into collecting these records needs to be acknowledged. For 24 years, she dedicated her time to making these observations. It would have taken a significant amount of time and effort to regularly tow-net the harbour. Similarly, she must have spent hours at a time at her microscope identifying the different species of plankton and making her detailed sketches. Her devotion and contribution to plankton research is worth commemorating and celebrating within our community.
