Plastic pollution in Nigeria: A huge research burden for scientists

This editorial discusses the available empirical findings on plastic pollution in Nigeria, particularly in the aquatic environment, and identifies some research gaps to be filled through empirical studies by terrestrial and aquatic scientists.

One of the clarion research needs of our time is plastic pollution. It is also one of the worst environmental challenges of the current geological period; i.e. the Anthropocene, (Waters et al 2016). The ubiquity of plastics has been well established, based on the reports from the tropics and temperate regions, terrestrial and aquatic environments, and in both
invertebrate and vertebrate animals (Akindele et al 2020). Globally, there have been heightened awareness and advances in plastic pollution over the last decade, understandably so, because of its implications for animal and human health (Carbery et al 2018); hence the need for the expertise of scientists.

Hitherto, research efforts were focused mainly on the abundance of microplastics (<5 mm in size) and macroplastics (> 5mm in size) in aquatic ecosystems (e.g. Nel et al 2018; Ebere et al 2019). Also, plastics have been reported in the three possible environmental compartments of the aquatic ecosystem (i.e. water, sediment and animals) (e.g. Lourenço et al 2017; Ebele et al 2019). However, there is now a need for greater attention on the toxicological implications of plastics. This is against the backdrop that they serve as vectors for the transfer of persistent, bioaccumulative and toxic chemicals (Teuten et al 2009). Furthermore, it has been recommended that the there is a need to investigate the
physiological fitness of some groups of animals vis-à-vis their exposure to different types of plastics. This is to provide a clue on their toxicity in animals (Akindele and Alimba, 2021).
Plastic pollution of the aquatic environment (marine in particular) became a topical issue towards the end of the last century, though not on a large-scale. In the last decade, many academic researchers picked up interest in plastic pollution, as evidenced in the number of paper publications in this regard. As at September 2020, nine out of the 59 plastic pollution studies from Africa, were from Nigeria (Akindele and Alimba, 2021), with the first available reports made in 2019 (Akindele et al 2019; Ebere et al 2019). Only three out of the Nigerian studies gave an account of plastic ingestion by animals (i.e. Akindele et al 2019; Adeogun et al 2020; Akindele et al 2020); other reports were on water or sediments. It is also worth emphasizing that the three studies were exclusively on freshwater animals (gastropods,
insects and fishes).

There is ostensibly a deficiency of data about plastic pollution in Nigeria. Thus, many research gaps are craving for the attention of aquatic ecologists, entomologists, ecotoxicologists, physiologists, etc. Currently, there are no sufficient data on plastic ingestion by many groups of animals in freshwater and marine environments. Elsewhere in Africa, there are reports of plastic ingestion by zooplankton, annelids, bivalves, cephalopods and aquatic birds (e.g. Lourenço et al 2017; Kosore et al 2018). Plastic pollution might be of particular interest to Nigerian marine biologists, since there is still a dearth of information in this regard as it relates to marine and estuarine animals. There is also a compelling need,
especially for terrestrial zoologists, to study plastic ingestion in some terrestrial animals, particularly the focal species such as insects and birds. For instance, one of the studies from Nigeria on plastic ingestion by freshwater animals focused on the larvae (aquatic life stage)
of damselfly, mayfly and non-biting midge (Akindele et al 2020). The occurrence of plastics in the insect larvae suggests the presence of plastics in their adults, and many other adult insects, in the terrestrial environment. Hence, it is very logical if plastic loads and their toxicity in terrestrial animals are considered in future studies. This is also imperative because the bulk of plastic contaminants in the aquatic environment usually emanates from terrestrial sources (Akindele and Alimba, 2020).

Also, the nine plastic pollution studies from Nigeria were exclusively made in the southern part of the country. While there is a need for more research data from the southern part, the same research efforts should be deployed in the northern part. This is very important
if the present approach of treating plastic pollution in Nigeria will be rectified. With a high level of research awareness on plastic pollution in different parts of the country, appropriate authorities (state and federal governments) could be put on their toes as far as the mitigation of plastic pollution is concerned. Polymer identification of suspected microplastics and macroplastics is also very important in future studies. It has been proven that microscopic identification of microplastics alone is not reliable, since ~70% of suspected microplastics do not often turn out to be plastics, even though they have such a resemblance (Hidalgo-Ruz et al 2012). Hence, there is a need for some state-of-the-art equipment that is not readily
available in Nigeria, e.g. micro-Fourier-transform infrared (ìFTIR) spectroscope. This final stage of identification of suspected plastics is a very crucial an essential requirement for impactful research in plastic pollution. Many of the African studies that ever got to this analytical stage sought collaboration with researchers in developed countries. Intending
researchers will either go this same way or seek huge funding as this could be capital intensive.

In conclusion, the following research gaps exist to date on plastic pollution of the Nigerian environment:
Plastic (macroplastics and microplastics) loads and chemical (polymer) identification in marine and estuarine animals.
Plastic loads and polymer identification in terrestrial animals.
Laboratory-controlled experiments: (i) physiological fitness of animals on account of plastic ingestion or exposure to plastics; (ii) ecotoxicological implications (heavy metals, persistent organic pollutants, etc.) of plastic ingestion by animals.
Implications of plastic pollution for both ecosystem functions and ecosystem services.
Data are particularly needed for Nigeria’s large freshwater systems, e.g. River Niger,
River Benue, Cross River, Kainji Lake, Shiroro Lake, and Tiga Lake.

Doctoral students can engage in research that advances knowledge and understanding in the aforementioned research gaps, as this has a dual advantage of helping their career and providing hints for environmental policy formulation.