Underwater Pollinators - No Longer Under The Radar

Avid readers of PlantingSeeds’ articles are familiar with pollinators and their roles in the ecosystem. From birds to bees, to bats, wasps and many others, our organisation works to shine the spotlight on pollinators’ important roles to support biodiversity. But it can be a little difficult to understand and be familiar with the As and the B’s of it all.

As an example, what do you know about underwater pollinators? We are not talking about bees and birds that can swim or dive! And if you claim ignorance, you are not alone. Biologists only discovered indications of underwater pollinators in the last 10 years.

A 2016 study conducted by marine biologists indicates that invertebrates play a role in pollination in the aquatic environment. The study, ‘Experimental evidence of pollination in marine flowers by invertebrate fauna’, published in Nature Communications, found experimental evidence that a variety of microscopic marine invertebrates are pollinators and have formed a symbiotic relationship with turtle grass, the plant matter that featured in the experiment.

(Marine invertebrates comprise many groups of different organisms and occur from the sea surface to the seafloor and into the substrate.They represent the vast majority of marine biodiversity and include, for example, sponges, corals, bluebottles, worms, shells, sea urchins, starfish, crustaceans, sea cucumbers and nudibranchs. Their size ranges from tiny microscopic organisms to several metres in length, and they have an amazing diversity of form).

The study found that in the absence of water-flow, the invertebrates visited the flowers, and carried and transferred mucilage mass with embedded pollen from the male flowers to the stigmas of the female flowers. Pollen tubes were formed on the stigmas, indicating that pollination was successful.

Traditional theories propose that water flow is the key to pollination of marine plants, and that animals only have a pollination role in terrestrial environments. However, these traditional theories suggest that pollination of marine plants is difficult in environments or times where the surrounding water tends to be still.

The Nature Communications study does not discard water as potentially being the primary vector for pollen transport, nor does it confirm if symbiotic relationships involving invertebrates are common in aquatic environments. However, the experimental evidence indicates we need to consider new methods of underwater pollination.

The new research has implications for our current understandings on environmental impacts on oceans. With climate change making oceans more acidic, gaining a fuller perspective on aquatic pollination is important. The acidification of the oceans is making it more difficult for invertebrates to maintain their exoskeletons, and therefore leads to population declines.The indication of the role of marine invertebrates aiding marine plants during pollination contributes to a further negative feedback loop.

Through chemistry, we know that the ocean’s ability to dissolve carbon dioxide will cause it to become more acidic. Through biochemistry, we know that plants use photosynthesis to convert carbon dioxide into oxygen. So the nefarious cycle is that the invertebrate population will fall because the ocean is becoming more acidic. This, in turn, causes the population of aquatic plants to decline because of the loss of pollinators, which lowers the rate at which carbon dioxide will be converted into oxygen. This leads to the ocean becoming even more acidic, further reducing the invertebrate population.

The new research does spotlight how we may be able to identify new means of restoring ecosystems. The identification of key underwater pollinators and the subsequent reintroduction of them into the ecosystem may support aquatic plant life and bolster their populations.

And the benefits may go beyond the aquatic ecosystem. Marine pollinators may help farmers who grow their crops in water. Aquaculture is a method of agriculture that grows crops in water, and a branch of aquaculture - hydroponics, raises fish with crops to produce a more nutrient-rich environment. Could the future of aquaponics involve raising crops with the help of delicious marine pollinators? Are marine pollinators the future of aquaponics?

Underwater pollinators have been under the radar for a long time. While PlantingSeeds is not proposing constructed habitat to support marine invertebrates, we hope we have contributed to a new theory that holds water.