Explorers! For the next few blog entries, we will be looking into how ocean plastic have affected the lives of those who rely on it. To start off, we shall look into the homes of a member of the Sulidae family, the Brown Booby. This post will serve as a summary to compare the results of two papers studying the same species of sea bird, the brown booby (Sula leucogaster), and its use of marine debris as nesting material and how this behaviour could describe the marine debris situation in the surrounding marine environment.

Article 1: Nests of the brown booby (Sula leucogaster) as a potential indicator of tropical ocean pollution by marine debris.

(Authors: Tavares, D.C., da Costa, L.L., Rangel, D.F., de Moura, J.F., Zalmon, I.R., Siciliano, S., 2016)

Tavares et al. studied brown boobies in coastal islands around Brazil primarily collecting data from the Santana Archipelago (SA) and “Franceses” Island (FI). These two sites were chosen as they were main breeding areas for brown boobies; the surrounding beach area was also sampled. Tavares et al, 2016 hypothesised that a preference for fishing gear, due to its resemblence to the vegetation the birds would have used, as nesting material among the brown boobies.

From their results, it was found that fishing gear made up 58% (SA) and 30% (FI) of the marine debris nesting material collected from the respective islands. Coincidentally, the Santana Archipelago is a hot spot for trawler fishing which is suspected to be the main contributor to the amount of fishing gear that is washing up to the nearby islands. Amongst the rest of the debris collected, it was found that a significant proportion were hard and soft plastics. The researchers suggested that this could be lethal to both adult and young brown boobies since both are at risk of entanglement or even ingesting the debris, thus increasing the risk of mortality. Young chicks depend highly on their parents for food, if their parents ingest these plastics by accident, and inadvertently feed it to their young.

An interesting find, the researchers noticed that despite having the appropriate vegetation needed to build a nest available for the birds, the brown boobies’ nests were still full of marine debris. What is causing this behaviour? Some literature have their own theories but nothing has been proven thus far.

Article 2: The use of anthropogenic marine debris as a nesting material by brown boobies

(Authors: Granta, M.L., Laversb,J.L., Stuckenbrockc, S., Sharpc, P.B., Bond, A.L., 2018.)

Granta et al, 2018 for this next paper decided to do a bigger survey of the nests of brown boobies across a bigger sampling area – 18 sites were chosen across 5 countries and data collection was done between 2013-2018. They found that overall, plastics were most abundant type of marine debris found, with hard plastics consistently appearing in the nests at all sites; hard plastics make up more than half of all debris found. They also found that the nests with the most debris found were those from the Santana Archipelago .

In their discussion, they talked about how ocean currents and wave action account for why marine debris wash ashore on brown booby nesting sites, of which some are uninhabitated islands located far from civilisation. Other sources of marine debris deposits highlighted include shipwrecks, trawling ships, and beachgoers (if the nests are near a human inhabitated territory). The researchers made an interesting hypothesis – since male brown boobies act as the primary nesting material collectors and the female will survey and judge the males’ handiwork before choosing her mate, this odd preference for marine debris could be an attempt by the male to impress their mate. One of their concerns is that marine debris in nests today could be an indication of how nests will look like in the years to come following the rise in marine plastic and other debris in the ocean.

Hmm..

Nature has its own way of making a comeback, however in today’s world, this cannot happen without global protection efforts to control how much is taken out of the environment at a time. Animals like sea birds are key in keeping a balance in our world’s oceans being apex predators, scientists refer to them as sentinel species – indicators of ocean health as mentioned by Granta et al, 2018.

References

Tavares, D.C., da Costa, L.L., Rangel, D.F., de Moura, J.F., Zalmon, I.R., Siciliano, S.,2016. Nests of the brown booby (Sula leucogaster) as a potential indicator of tropical ocean pollution by marine debris. Ecol. Indic. 70, 10–14.

Granta, M.L., Laversb,J.L., Stuckenbrockc, S., Sharpc, P.B., Bond, A.L., 2018. The use of anthropogenic marine debris as a nesting material by brown boobies (Sula leucogaster)