Coronavirus: boon and bane for sea turtles

The global pause in the last months has seen an overall resurgence in water and air quality around the world.

It's also a breath of fresh air for marine life.

This has been evident in major ecosystems like River Ganges, where, in some places, the waters have become drinkable again for the first time in two decades [1].

Horseshoe crabs have seen stabilization in its population in Delaware Bay. A precarious respite, it's important though that there's no resurgence in fishing of this dinosaur age relic since its blue blood is crucial to meeting the growing demand for the production of safe coronavirus vaccine [1].

Quieter oceans have also led to the resurgence of 2000 dolphins off the coast of Fujairah in the UAE [2], superpod of 350 sperm whales (Physeter macrocephalus) off Sri Lanka [3], and more sightings of endangered dugongs (Dugong dugon) off the coast of Thailand [4].

Despite all these good news, giving wildlife time and space to recover can be a double-edged sword for some animals. 

This is the case for sea turtles [5].

Photo of a green sea turtle (Chelonia mydas) hatchling, Tortuguero National Park, Costa Rica,  from Forbes

The logic is that beach closures would be a good thing for these creatures since this would mean less disturbance to them [5]. True enough. This has been the case in one beach in Thailand where 11 leatherback sea turtle (Dermochelys coriacea) nests have been found since November, the highest record in the past two decades. No such nests had been recorded in the last five years. A real boon. [6,7].

On the other side, the pandemic also meant hampering important research and conservation projects [5,8].

In the case of Turtle Island Restoration Network (TIRN), 300 volunteers are typically enlisted to monitor hundreds of kilometers of beaches in Texas. With the onset of COVID-19, however, only two full-time staff are left to patrol the stretches of beach once a week [5].

This poses a huge threat to the critically endangered Kemp's ridley sea turtles (Lepidochelys kempii) since the transfer of their eggs to the hatchling facility is curtailed. Poachers are also likely to steal eggs for income. Beach closures also mean slow response to the threats they are facing [5].

Many turtle conservation groups are also hard hit financially [5,9]. Budgets are usually obtained from volunteer programs which have come to a complete halt due to travel bans [5,10]. Along with this is loss of donations from larger institutions, drying up funding reserves for conservation [5]. This is most critical for projects that have taken decades of work for sea turtle populations to recover [9].

You may click here to know more about sea turtles.

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[1] Degnarain, N. (2020, May 16). Six places where oceans, rivers and marine life have rebounded during the coronavirus pandemic.  Forbes. Retrieved from https://tinyurl.com/y8hdjm8p

[2] Haza, R. (2020, April 14). Watch: rare albino Risso's dolphin spotted off Fujairah coast. The National. Retrieved from https://tinyurl.com/ya6vvkb3

[3] Rodrigo, M. (2020, May 6). Researchers miss out on sperm whale superpod in Sri Lanka amid pandemic. Mongabay. Retrieved from https://tinyurl.com/y8ed449s

[4] The Star. (2020, April 27). Thai oceans see more fish and dugongs amid coronavirus closures. Retrieved from https://tinyurl.com/y73zjl39

[5] Owens, B. (2020, May 6). COVID-19 is not all good for wildlife. Hakai Magazine. Retrieved from https://tinyurl.com/ycap8owy

[6] Geggel, L. (2020, April 21). Baby leatherback sea turtles thriving due to COVID-19 beach restrictions. Live Science. Retrieved from https://tinyurl.com/y9jwte9d

[7] The Guardian (2020, April 20). Coronavirus lockdown boosts numbers of Thailand's rare sea turtles. Retrieved from https://tinyurl.com/y9z4bdcd

[8] Daffurn, E. (2020, April 27). COVID-19: Good or bad for the ocean? Scuba Diver Life. Retrieved from https://tinyurl.com/ya2ljun7

[9] Sea Turtle Conservancy (2020, June 1). Sea turtle conservation work in Tortuguero threatened due to COVID-19. Retrieved from https://tinyurl.com/yamjeg6p

[10] Sunkara, L. (2020, April 29). COVID-19 travel restrictions are further endangering sea turtles. How to help. Forbes. Retrieved from https://tinyurl.com/y9xk2tyj

Who's Got Jellies in their Gut?

Gelatinous zooplankton, loosely termed as jellyfish, can be found throughout world’s oceans, known to cause large blooms. This group includes scyphozoan jellyfish, siphonophores, ctenophores, salps, pyrosomes, and appendicularians [1]. 

If we were asked who dines on these jellies, we might reserve the term ‘belly-full-of jelly’ to charismatic sea turtles (Dermochelys coriacea, Chelonia mydas) and the ocean sunfish (Mola mola). And it's indeed fitting since an adult leatherback turtle, for instance, ingests an average of 330-kg jellyfish wet mass per day or 73% of its body mass [1]. 

With the rise of new technologies in recent years, however, this exclusivity is no longer true: It turns out that not only such massive marine predators get a chunk of their diet from jellyfish. There’s a whole lot on the table, from birds to fishes to worms, joining the feast [1].

New approaches to study the diet of marine animals such as stable isotope analyses or SIA (getting animal tissues to estimate trophic level), animal-borne cameras, remotely operated vehicles or ROVs, and DNA metabarcoding support the finding that a diverse range of marine predators feed on jellies, not incidentally but targeted [1].  

SIA revealed that jellyfish forms a substantial part of the diet of bony fishes Chloroscombrus chrysurus, Thunnus thynnus, Euthynnus alletteratus, Tetrapterus belone, Xiphias gladius and the green sea turtle Chelonia mydas. 

Animal-borne cameras revealed 42.2% of prey capture for some species of penguins, consuming scyphozoans, salps and ctenophores [1]. 

Metabarcoding showed that jellies make up 20% of food DNA sequences of the two species of albatross, ahead of crustaceans in terms of importance. Meanwhile, next-generation sequencing showed that the endangered European eel Anguilla anguilla has got gelatinous zooplankton in its diet. Seen through powerful ROVs, deep-sea octopus (Haliphron atlanticus) and benthic animals, like echinoderms, crabs, shrimps, amphipods, sea anemones, and worms join the slew of jellyfish predators [1].

Hays et al. 2018 Figure 2A, showing a diverse group of predators worldwide feeding on jellyfish.

Overwhelming evidence of widespread jellyfish consumption throughout the world’s oceans means that jellyfish cannot be simply considered a bycatch, but targeted and opportunistically consumed by many marine predators. However, it's important to note that this shift may be influenced by changing ocean conditions [1]. 

Also, knowing that a growing number of marine life now relies on jellyfish for nutrition signifies their susceptibility to harm, or even death, for mistaking plastic wastes for food [1]. 

These findings are important given that jellyfish holds a huge fraction of the pelagic biomass and have recently increased their abundance worldwide [3]. The study also challenges the common notion that undermines the energetic gain from jellyfish consumption, thus the need to better understand its dietary value [1].

To know more about jellyfishes and other gelatinous zooplankton, visit SeaLifeBase. 

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[1] Hays, G. C., Doyle, T. K., & Houghton, J. D. (2018). A Paradigm Shift in the Trophic Importance of Jellyfish?. Trends in Ecology & Evolution 33(11):874-884. Retrieved from https://bit.ly/2DCvaY7

 [2] Lewis, A. (2011, January 5). Leatherback turtle feeding. YouTube. Retrieved from https://bit.ly/1vo1QO8