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Internship research project: Plastic in post-hatchling loggerhead turtles
By:
Claudine van Zyl
Claudine is one of our research interns, while she completes her postgraduate diploma in Marine Sciences at the Cape Peninsula University of Technology.

Where do I even begin! 2020 was such a crazy year. It was my final year, and my diploma was coming to an end!  This entailed a semester of classes and a semester of Work Integrated Learning (WIL); a Cape Peninsula University of Technology version of an internship, which includes two reports for final assessment. And didn’t COVID-19 just come along and throw a huge curveball in the middle of all the plans laid out for 2020. Thankfully, I was still able to continue with my internship at the Two Oceans Aquarium Education Foundation, with a Research project on “The characterization of plastics in stranded post-hatchling loggerhead turtles along the South African coastline from 2015 to 2020.  On top of that I was also able to complete my Marine Science Practice Report on activities I had done at the Aquarium Foundation and at the Aquarium, like beach clean-ups, harbour clean-ups, an outreach, sea turtle rescue and rehabilitation, penguin animal husbandry and online courses! 

Allow me to give you a little bit of background before we get into things. I am passionate about the environment, conservation and of course the devastating effectof plastics. My topic and project were so fitting because as a turtle-ologist (that is what we like to refer to ourselves as) I get to see first-hand the effects of plastic pollution on various marine animals, specifically the struggle and suffering of stranded sea turtles. The data recorded by the Two Oceans Aquarium on the post-hatchling loggerhead sea turtle (Caretta caretta) showed that 54 post-hatchlings had ingested plastics from 2015 to 2020.

Claudine with a loggerhead hatchling (Image credit: Kirshia Govender)

Sea turtles are inquisitive creatures and opportunistic feeders, thus making them more at risk of ingesting plastics, especially during their post-hatchling and juvenile life stages. The types of plastics ingested were identified as fragments, film, line, pellets, and foam using GESAMP (2019) method of marine plastic identification. Fragments were the most common type of plastic ingested by post-hatchling loggerhead turtles. The colours of the ingested plastics identified were black, grey, brown, white, cream, clear, yellow, orange, red, green, blue, purple, and pink. The colour identification method was used by Ryan et al. (2016), although in 2018 and 2019 the colour pink was recorded in the data and therefore had to be added to the colour categorization. With the help of previous papers, I was able to group the 13 colours into seven pooled categories namely, black-grey-brown, white-cream, clear, yellow-orange-red, green, blue-purple, and pink. My data showed that the most common colour ingested by the post-hatchlings was white-cream. Post-hatchling loggerhead turtles have been found stranded along 43 beaches off the South African coastline: from St. Francis Bay to St. Helena Bay. again grouped the stranding beach locations to three regions where post-hatchlings had ingested plasticsnamely Cape Peninsula (Kommetjie to Muizenberg), Overstrand (Betty’s Bay to Pearly Beach) and the Garden Route (Struisbaai to Plettenberg Bay). 

The Two Oceans Aquarium Education Foundation’s Sea Turtle Rehabilitation Facility received a total of 634 rescued post-hatchling loggerhead sea turtles from 2015 to 2020. The turtles were brought to the Turtle Rehabilitation Facility with the assistance of the Sea Turtle Rescue Network. The Sea Turtle Rescue Network consists of the Two Oceans Aquarium Education Foundation’s conservation team, coastal communities, and organisations where network points have been created to care for the rescued post-hatchlings and then transport them to the Turtle Rehabilitation Facility. Upon arrival, the weight (g) and measurements i.e., straight carapace length – SCL (cm), straight carapace width – SCW (cm), curved carapace length – CCL (cm), and curved carapace width – CCW (cmare taken of the post-hatchling turtle. Each has an arrival sheet, which records abovementioned measurements, its stranding location and a unique turtle IDThe first two weeks of rehabilitation takes place in a controlled critical-care environment, where each post-hatchling is placed in its own tank. The post-hatchlings are offered food daily and their weight is recorded weekly. 

Loggerhead hatchlings ofetn mistake small plastic pieces for real food in the ocean

The egested plastic of each post-hatchlings is removed from the tank as per methodology described in past papers. The tanks are checked daily to ensure the egested plastic are not re-ingested. Any faecal matter is removed with a net, washed, and filtered through a sieve to ensure that all foreign objects, plastics, or particles are collected. Plastics that were collected during a post-mortem, are usually found within the stomach, intestine, cloaca, and/or bladder. These organs are emptied into a sieve, the contents washed and the plastics are separated and cleaned from the organic waste and dried. The collected plastics are stored with records of egestion or post-mortem dates on the turtle’s arrival sheet. The stored egested plastics are counted and the type and colour are recorded using Microsoft Excel. Further statistical data analysis is done using SPSS v26 software.  

The results for this study showed that most post-hatchlings stranded along the Overstrand coast and were also much larger in arrival weight, CCL, and CCW than both Cape Peninsula and the Garden Route coast. Post-hatchlings that weighed between 30–100 g on arrival ingested more plastic than those weighing > 100 g and the stranding period of the majority post-hatchlings occurred between March and June each yearSo, there you have it! My report allowed me to investigate and explore different papers, which broadened my knowledge and insights, and I have learnt so much about these wonderful creatures.  

References 

GESAMP. 2019. Guidelines for the monitoring and assessment of plastic litter and microplastics in the ocean. Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection. (Reports and Studies GESAMP) No. 99: 130. 

Ryan PG, Cole G, Spiby K, Nel R, Osborne A and Perold V. 2016. Impacts of plastic ingestion on post-hatchling loggerhead turtles off South Africa. Marine Pollution Bulletin 107(1): 155–160. Available at: https://doi.org/10.1016/j.marpolbul.2016.04.005 [accessed 15 October 2020]. 

1 Comment

  1. Long hours and delicat detailed data giving interesting results.

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