NWU’s marine research has international impact

Belinda Bantham -- Wed, 06/13/2018 - 14:45

NWU’s marine research has international impact

Researchers at the Unit for Environmental Science and Management (UESM) in the North-West University’s (NWU’s) Faculty of Natural and Agricultural Sciences, are making their impact felt within the field of marine research.

This is evident from the acclaim Dr Roksana Majewska, a postdoctoral fellow from the UESM receives as a contributor to the online research hub, Science Trends. The hub provides a platform for scientists to share their research directly with a large and global audience.

Sea turtle-associated diatoms: undiscovered disappearing micro worlds

Today, many scientists believe we are living through one of the greatest mass extinctions the world has ever seen. One may argue that existing species must inexorably fade away, and new life forms emerge to fill the rapidly changing ecological niches, inevitable with the process of evolution. One may even suspect that these very occasional large-scale die-offs are a natural part of the earth’s life cycle.

In these troubled times, when global biodiversity is widely believed to be reduced by up to several hundreds of species each day, only the sudden and rapid disappearance of species of so-called “charismatic mega fauna” makes the average person feel compelled to sign petitions and passionately support wildlife habitat conservation projects.

That is perhaps quite fortunate for sea turtles – ancient marine creatures iconic to both marine biologists and indigenous peoples to whom they traditionally constitute not only a biological memory of earlier evolutionary eras but also a source of food and important element of cultural heritage. Yet, as has recently been shown, sea turtles themselves constitute a highly unique habitat for largely unknown micro species whose fate is inevitably entwined with that of their hosts.

Diatoms, unicellular microalgae that are thought to be responsible for up to 50% of both oceanic primary production and global oxygen production, are often some of the earliest colonizers on any marine substrate, and it has recently been shown that all seven living species of sea turtle harbour, often very abundant, epizoic diatom communities, some of whose species are as yet only known from the sea turtles. Although diatoms have long been known to grow on aquatic vertebrates, including whales, dolphins, and seabirds, sea turtle-associated diatoms have been almost entirely overlooked.

Only in the last three years have the first studies exploring sea turtle-associated diatoms been published, and several new diatom taxa, including three new genera, have been described. These new taxa show traits of obligate epibionts, which means they may require a direct contact with their basibionts (i.e. the host organism) to develop and survive. If so, we may be dealing with the very first case of endangered marine microbes – quite contrary to the popular hypothesis that, due to their microscopic size, particularly efficient dispersal modes, and high growth rates and adaptation capabilities, in the microbial world “everything is everywhere, and the environment selects”. Since their first discovery, sea turtle diatoms have attracted growing attention, partly due to their potential use as indicators of sea turtle behaviour (e.g. migration patterns) and health.

Although research here may help to bridge various gaps in general understanding of both sea turtle and diatom ecology, evolution, and biogeography, at present many aspects of the symbiosis-like relationship between these micro- and macro-organisms remain unaddressed. For instance, it is not yet understood whether epizoic diatom communities are specific to particular sea turtle host species or, rather, geographic location; or whether they are subjected and respond to seasonality, what factors influence their composition and abundance, and what ecological role and function they have in marine ecosystems.

Currently, despite extensive conservation efforts, all seven existing sea turtle species are endangered, with two species being critically endangered, according to most of the international, national, or regional assessments, and are protected by various legislations. We now know that these remarkable animals constitute mobile islands and hotspots for unique microbial life that could soon be lost before ever being discovered and explored. Thus, the on-going and large-scale research conducted in collaboration among scientists from four different continents aim to provide baseline data about sea turtle-associated diatoms and other microscopic epibionts, generating important advances in both epizoic microbe and sea turtle research.

Dr Roksana Majewska.