Kelp Development in an Aquaculture Facility:

Quantifying diel periodicity of spore release and comparing growth methods of Laminaria ochroleuca.
Supervisor: Aschwin H Engelen Neusa Martins (CCMAR, Univ Algarve)
Kelps and kelp forests play a vital role in marine environments providing ecosystem services including carbon sequestration, fisheries production, biodiversity enrichment, coastal protection and nutrient uptake. Due to the environmental as well as increasing commercial importance on kelp species, it is important to understand what motivates their growth and reproductive behavior. This study involves aspects to measure the growth rates of Laminaria ochroleuca sporophytes as well as their reproductive behavior of spore release. Young sporophytes of the kelp L. ochroleuca were developed at an aquaculture facility in southern Portugal. The current examination measured the growth rate of sporophytes to compare how they develop in three different methods of holdfast attachment. Young sporophytes were either developed free floating in a 500 L tank, or attached by the holdfast to either an underwater plate or rope. Weekly measurements of the blade surface area, length, width and visible reproductive area were analyzed to compare the growth rates of each attachment method. The results demonstrate that the kelp perform markedly better when their holdfast is secure as opposed to free floating. There were similarities between both plate and rope attachment methods, but the plate attachment performed best for the growth rates overall. This study also quantifies the diel periodicity of the spore release from the kelp at the aquaculture facility. This experiment quantified the abundance of spores released from cuttings of sporophytes’ sorus tissue over the duration of 28 hours. These five replicate samplings occurred during the prominent phases of the moon to identify if there was also an influence of the lunar phase. Temperature, tide height and light intensity were measured throughout the experiment to determine if there was a correlation with the timing of the spore release. The results demonstrated that there was a peak of abundance in spores within a four hour period, but occurring at different times of the day. Two sets displayed a primary release just after the sunset and one set showed a release after sunrise, indicating photoperiod as a potential trigger for the release of spores. There was no clear pattern ascertained and the environmental parameters that induce the maturation or the release of spores remains inconclusive.