Microplastics a macro-disaster: A threat to the largest fish of our seas?

We aim to investigate microplastic ingestion by whale sharks in the S.A. MPA and identify potential routes of microplastic exposure. As whale sharks belong to the marine charismatic megafauna our findings will help raise awareness of plastic pollution and marine pollution first regionally, through the MWSRP, and then globally.

Microplastics have emerged as one of the major environmental threats to our seas (Galloway et al., 2017; Worm et al., 2017). While there has been an initial effort to investigate microplastic interactions with large filter-feeding marine megafauna, such research has thus far been based on strandings of carcasses and presence of plasticisers in their tissues (Besseling et al., 2015; Fossi et al., 2017). We identified a non-invasive method, which will help gain further insights into microplastic interactions with these megafaunal filter-feeders. Beyond the scientific advances, this study aims to use research on the emblematic and endangered whale shark to raise awareness, enhance marine stewardship and action against marine plastic pollution worldwide. Furthermore, through our outreach and education programme, workshops with stakeholders and environmental ministries we thrive to support the development of sustainable waste management in the Maldives. Lastly, the MWSRP will implement our findings to strengthen regional long-term marine stewardship.

Marine litter and microplastics have been shown to impact over 650 marine species worldwide (GEF, 2012). In fish, microplastics have been shown to cause reductions in food uptake and predatory performance and act as a vector of toxins, which can bioaccumulate and lead to endocrine disruption and hepatic stress (De Sá et al. 2015, Rochman et al. 2013, Rochman et al. 2014). The largest fish of our planet, the whale shark, is particularly prone to the ingestion of microplastics, filtering up to 614 m3/h of sea water to obtain their planktivorous prey (Motta et al. 2010). An area of particular concern are the Maldives where whale sharks are known to occur all year round and microplastics have been found to be particularly abundant (Riley et al. 2010, Imhof et al. 2017). As a consequence, microplastics may add another stressor onto the endangered whale sharks, who in this region suffered from hunting for their meat and oli-filled livers (Rowat 2007; Jackson et al 2001), some remaining illegal finning (Riley et al. 2009), and nowadays a lack of management of the tourism industry, with important rates of vessel strikes reported in the S.A.MPA (MWSRP unpublished data).

To date only few studies have investigated how large-bodied filter-feeders may be affected by microplastics. For instance, Besseling et al. (2015) have extracted 45 microplastics from a stranded humpback individual. Others sampled tissues from basking sharks and fin whales and used chemical tracers such as phthalates as indicators of microplastic ingestion (Fossi et al. 2012, 2014, 2016). This method also has been applied to whale sharks in La Paz Bay, Mexico where tissues have been found to contain compounds used as flame retardants in plastics (Fossi et al. 2017). While this provides some initial evidence of the susceptibility of whale sharks to plastic pollution there is, to date, no empirical evidence of the ingestion of plastic debris by these sharks. Using a non-invasive method of sampling the whale sharks faecal matter we are able to provide direct evidence of microplastic ingestion and address other key scientific questions (objective 1-3).

Despite contributing significantly to the field of microplastic we seek to address the rising demand on science to have a real-world impact through extensive outreach and community engagement. Whale sharks amongst other filter-feeding ocean giants have recently been identified as an ideal umbrella species in order to engage local communities, stakeholders and society globally (Germanov et al. 2018).

Due to their remote location and increasing tourism, the Maldives struggle with their waste management (Malatesta et al. 2015). However, they also feel the great responsibility in protecting their unique marine habitats, home to many threatened marine species. The opportunity of encountering these rare species, lures tourists from all over the world to this archipelago and tourism has become the largest economy in the Maldives. In 2013, whale shark tourism in the South Ari Atoll marine protected area alone has been valued at 9.4 million USD (Cagua et al. 2014). In order to preserve these unique habitats and achieve good environmental status, it is important to open the dialogue with the community and stakeholders alike and increase visibility of the issue of plastic pollution globally. Research and outreach work have been shown to be of importance in achieving this goal. For instance, in the Ningaloo Marine Park, Australia research was a fundamental part of establishing trust between the local community and stakeholders (Cvitanovic et al. 2018). This ambitious but necessary project provides a timely opportunity to drive local waste management and decrease plastic pollution through evidence-based decision making from the local to the global scale.

• Quantify and qualify microplastic present in whale shark faeces and surface water plankton samples collected between 2015 and 2017. Microplastics from faeces and plankton will be compared with one another to investigate transfer of microplastics from plankton.
• Provide sampling gear and training to MWSRP to allow for accurate faecal sample collection and sampling of plankton from discrete depths to more accurately determine microplastic ingestion by whale sharks and identify routes of microplastic exposure. Provide training to MWSRP on standardized data collection on marine litter during beach clean-up.
• Whale shark occurrence data (MWSRP database) and remote sensing data will be analysed to better understand residency patterns of individual specimens within the Maldives and investigate the potential link between certain behaviours, such as being more transient or resident, with the quantity and types of microplastics found in their faeces.
• Run an education programme at the Maldives National University (MNU) (Appendix 2), meet stakeholders and members of the environmental ministry to disseminate our findings. Support innovative waste management initiatives. Support MWSRP outreach efforts in local communities by providing new findings on this emblematic species and raise action against marine pollution.
• Communicate findings worldwide via video documentation of the research and dissemination through social media, newspapers, radio, television, Massive Open-access Online Course (MOOC), as well as to the scientific community in the form of peer reviewed articles.