What is seagrass?
Seagrasses are the only true plants in the ocean. They live in the subtidal zone where they get enough light to photosynthesise, grow, flower and pollinate. They are usually anchored in sand or sediment and contribute to clearer waters as less suspended particles can form once the grass is established and there is a slowing of water movement owing to the height of the grass. Greater clarity of water better supports the function of corals and therefore reef structures.
What does seagrass do?
Seagrass evolved from terrestrial plants and recolonised the oceans millions of years ago. Seagrass meadows are very productive ecosystems which preserve biodiversity, often acting as nurseries for many species as the tall leaves offer protection and shelter for smaller life forms.
Seagrass is integral in the carbon, nitrogen and sulphur cycles of the subtidal ocean and seagrass meadows can form large and natural carbon stores.
Seagrass is considered to be an ecosystem engineer. From reduction of sediment movement to oxygenation of the sediment, seagrasses store carbon, improve water quality and reduce excess nutrients from pollutants such as those entering the sea through eutrophication.
Seagrass in Europe
In the Mediterranean, the sea grass Posidonia oceana, or “Neptune grass” in English and “Alka” in Maltese is the species of seagrass which offers a food source for marine herbivores such as parrot fish, turtles and nudibranchs.
However, some climate change models suggest that some seagrasses will go extinct – Posidonia oceanica is expected to go extinct, or nearly so, by 2050.
Our impact- Are we being Ecoresponsible?
It’s not just important to consider whether your sunscreen, body lotion or hair conditioner is coral or reef safe, we need to consider the chemical impact of our presence in the ocean on seagrass too. Although there are no validated test guidelines to assess the toxicity of a substance or product on seagrass, we can extrapolate existing freshwater and terrestrial data to the marine environment somewhat. If a chemical disrupts the nitrogen or carbon cycle, it may disrupt seagrass growth and survival. If a chemical impacts on algal growth, it my have an impact on photosynthesis and so could affect seagrass. Effects observed in freshwater macrophyte testing and terrestrial plant testing may indicate a potential for similar effects on seagrass in the subtidal compartment.Just because there is no validated test guideline to assess the impact of our chemicals on seagrass specifically, it does not mean that we should ignore the environmental safety assessment altogether.
Ecoresponsibility means using all available information to make an informed assessment, regardless of the legal imperative to do so.
The focus this March is on seagrass but true ecoresposibility is for life, not just for March.
First published 1 Mar 2021