WEEDS DISPLACE KELP WHEN CO2 IS HIGH

Photo: John Turnbull

New research by Prof. Sean Connell and an international team from Europe, Canada, the USA, and Hong Kong has found that the higher carbon dioxide levels predicted for our oceans will favour subordinate weedy plants over formerly dominant, more ecologically valuable kelp forests. Disturbances to ecosystems, such as increasing ocean acidification from higher CO2 levels, often create opportunities for particular organisms to thrive at the expense of others. As weedy species are better able to exploit carbon as a nutrient, they will grow faster than their natural predators (sea urchins) can consume them, displacing more biodiverse kelp forests and potentially resulting in conservation implications for species such as the leafy seadragon (Phycodurus eques) and common seadragon (Phyllopteryx taeniolatus, above), which inhabit kelp-covered rocky habitats in Australia’s southern waters. Led by the University of Adelaide, the researchers used natural volcanic CO2 seeps to compare today’s growth of weeds and kelps with levels of CO2 forecast for the turn of the century. ‘Under the level of acidification we will find in oceans in a few decades, marine life is likely to be dominated by fast-growing, opportunistic species at the expense of longer-lived species with specialist lifestyles,’ co-author Prof. Ivan Nagelkerken states. ‘We need to consider how natural enemies might be managed so that those weedy species are kept under control.’

Connell S, et al. 2018. Ecology. DOI:10.1002/ecy.2209