CIE Spotlight: Recovery pathways from small scale disturbance in a temperate Australian seagrass

Tim S., Craig S. & Peter M

Tim S., Craig S. & Peter M

Title: Recovery pathways from small scale disturbance in a temperate Australian seagrass

Authors: Timothy M. Smith, Paul H. York, Peter I. Macreadie, Michael J. Keough, D. Jeff Ross, Craig D. H. Sherman

Source: Marine Ecology Progress Series, Vol. 542, Pages 97–108, 2016

Brief summary of the paper: Recovery from disturbance is a key element of ecosystem persistence, and recovery can be influenced by large scale regional differences and smaller local scale variations in environmental conditions. Seagrass beds are an important yet threatened nearshore habitat and recover from disturbance by regrowth, vegetative extension, and dispersive propagules.

We described recovery pathways from small-scale disturbances in the seagrass Zostera nigricaulis in Port Phillip Bay, a large embayment in south-eastern Australia and tested whether these pathways differed between five regions with different hydrodynamic conditions and water quality, and between sites within those regions.

Recovery pathways were broadly consistent. When above-ground biomass was removed, recovery, defined as the point at which disturbed areas converged with undisturbed controls, took 2 – 8 months, but when we removed above- and below-ground biomass, it took between 2 – 13 months. There was no evidence of recovery from sexual reproduction at any sites regardless of the presence of seeds in the sediment or flower production.

We found no regional differences in recovery, but substantial differences between local sites. At some sites rapid recovery occurred because seagrasses grew quickly, but at others, apparent recovery occurred because regrowth coincided with overall declines in cover of undisturbed areas.

Recovery time was unrelated to seagrass canopy height, biomass, percentage cover, stem density, seed bank density, epiphyte cover or sediment organic matter in seagrass adjacent to disturbance experiments.

This study highlights the importance of understanding fine-scale variation in local recovery mechanisms, which may override or obscure any regional signal.