Alisa A. Mihaila1,2, Rebecca Lawton1,2, Christopher R. K. Glasson1,2, Marie Magnusson1,2
1School of Science, The University of Waikato, Tauranga, New Zealand
2Environmental Research Institute, The University of Waikato, Tauranga, New Zealand
The reproductive cycles of seaweed are typically controlled by both endogenous and environmental factors related to seasonal change, such as temperature, light intensity, and photoperiod. In particular, gametogenesis and sporogenesis are mediated by temperature for approximately 70% of temperate seaweed species where this has been quantified. Therefore, it can be expected that increases in water temperature due to climate change causes shifts in the reproductive phenology (the timing of key events in the reproductive cycle) of seaweeds. This has become an increasingly common phenomenon for a range of organisms from different terrestrial and aquatic taxonomic kingdoms, however, to date, research on the effects of climate change on the reproductive phenology of seaweeds is lacking. Instead, the majority of related research focus on geographical shifts in the distribution and abundance of seaweed populations. We therefore conducted monthly field sampling of the red seaweed Asparagopsis armata over 18 months at Matheson’s Bay, North Island, New Zealand, and quantified presence/absence of reproductive structures, and reproductive maturity and viability of naturally released carpospores and tetraspores under laboratory conditions. The reproductive phenology of A. armata was previously assessed 35 years ago at this location, and since then, the average sea surface temperature along the northeast coast of the North Island has increased at a rate of 0.4 °C per decade. This study therefore provides the first temporally longitudinal analysis of potential climate driven shifts in reproductive phenology of a seaweed of emerging commercial importance.