Monitoring Giant Kelp

Last updated Nov 2021 (posted Dec 12, 2020) by Nicole – Marine Citizen Science, Seaweed, Wellington Underwater Club

Area Covered Time series

Diving in giant kelp forests started my passion for seaweed! Giant kelp, Macrocystis pyrifera, is particularly visible with fronds reaching up from the seafloor and building thick floats on the surface in good conditions (it can grow a staggering 60 cm a day under ideal conditions!). 

Giant kelp is less likely to occur in areas where water temperatures exceed 18-19°C and the inner bays of Wellington harbour have already been noted as the very limit of growth. We are interested in how summer water temperatures effect the growth and abundance of giant kelp at Kau Bay, one of the common dive sites in Wellington harbour. To account for summer and winter season volunteers snorkel around the giant kelp bed in May/June and Nov/Dec using a GPS device to plot the surface area on maps. We also use temperature monitoring data from the regional council at the site to get an indication of a warm summer (red arrow, water temperature exceeds 18-19°C frequently) or cooler summer (blue arrow, water temperature mainly below 18-19°C). 

Seaweed forests face a range of threats beside increasing water temperaturessedimentation, sand inundation, coastal development and pollution (including impact by weed killers). Overgrazing by exploding numbers of kina due to the lack of natural kina predators through overfishing can turn thriving seaweed forests into barren rock within a couple of years.

Read more about the project: 

Project Baseline Wellington – Monitoring Giant Kelp is a Citizen Science Project by the Wellington Underwater Club. Contact us for more information.