The 2023 field season marked the 14th year of bull kelp monitoring by the Mayne Island Conservancy, and the 5th year since the monitoring program expanded to include partners on other Southern Gulf Islands. This past season 33 volunteers and staff from five organizations spent 178 hours on the water. Volunteers recorded a total of 31.23 hectares of bull kelp at 17 annual monitoring sites around Valdes, Galiano, Mayne, the Penders, and Saturna Islands. This was also the first year we compared year-to-year change in kelp area for sites beyond Mayne Island. We have created a site-by-site summary of results (available here) for all sites where we have at least three years of data. Please note that in most cases, long-term data (>10 yrs.) is required to draw conclusions about long-term change.

What is bull kelp?

Bull kelp is an amazing species of brown algae. Large and of high ecological value, it is arguably the most impressive seaweed found in the Southern Gulf Islands. It plays several important roles in our intertidal and nearshore ecosystems. As an annual species, bull kelp lives for only one growing season, yet it can grow to a length of nearly 40 metres (usually closer to 10 metres) from the tight grip of its root-like holdfast on the rocky ocean bottom, to the tips of its long strap-like blades. Growing in dense beds, bull kelp forms underwater forests that provide a safe living space for many marine creatures including sea stars, crabs, rockfish, and young salmon. Kelp forests provide vital nursery habitat for many of our commercially and recreationally valuable fish and invertebrates by allowing them to find food and hide out from predators.

In the fall and winter, as daylight hours diminish, temperatures drop, and storms increase in frequency, aging kelp break free from its holdfast anchors and is swept onto beaches and out to sea, or sinks to the sea floor. Just as decomposing seaweed can help feed our vegetable gardens, so too does it provide life-giving nutrients to the animals living along our shorelines and on the ocean floor.

In addition to its many ecological values, bull kelp also makes a decent musical instrument.

Why monitor bull kelp?

As our planet warms because of increases in greenhouse gases, our oceans are also warming. This warming trend has been linked to declines in kelp here in the Salish Sea and elsewhere in British Columbia, as well as in south Puget Sound, California, and New Zealand. Conservancy survey data, along with data collected by other monitoring programs along the coast, allows us to detect changes in this important species. Recently our data contributed to an understanding of kelp declines in British Columbia (read a pre-press summary of the scientific paper).

A collapse of bull kelp populations would have far-reaching impacts on our ocean environment. Since bull kelp is such a fast-growing species, it captures a lot of energy from the sun, and makes that energy available to marine food webs. Where bull kelp grows in dense forests, such as within our monitoring sites, it provides a place for juvenile fish and other marine animals to hide from predators and shelter from ocean currents. In the process of capturing that solar energy, bull kelp also pulls carbon out of the ocean. Theoretically, some of that captured carbon makes its way into deep ocean sediments, helping offset the negative impacts of ocean acidification and global warming.

What does our data show?

The data we have collected between 2010 and 2023 shows that there is no consistent trend in the sea surface extent of bull kelp across our monitoring sites. This is good news, considering the declines that have been documented elsewhere. Though most of our monitoring sites appear (based on short-term data) to be stable, with some even increasing, we have observed declines at specific sites, including at Georgina Point, the north side of Georgeson Island, and Russell reef (north of Boat Pass between Saturna and Samuel Islands). These sites are all located on the Strait of Georgia side of the islands where sea surface temperatures are warmer. These observations support other research linking warming waters to declines in bull kelp.

Bull kelp has declined in only a few of our monitoring sites, such as the north side of Georgeson Island.

How you can help

Stay informed: Invest time to learn about our natural environment and the work being done to understand and care for it. The more we know, the more able we are to make informed decisions. Talk about what you’ve learned with friends and family. It’s fascinating and fun to learn! See below for some recommended reading related to bull kelp.

Donate: Our work to monitor nearshore marine environments requires funding for staff time, equipment, and overhead. Community donations make up approximately 70% of the operating costs of our Shoreline Care Program, which includes our eelgrass monitoring, bull kelp monitoring, Dungeness crab monitoring, shoreline cleanups, and associated public education programs. We received grant funding from the Sitka Foundation for 2023 and 2024 which covers 30% of the program costs. We want to express a huge thank you to the Sitka Foundation and our community donors for helping make this work possible!

Volunteer: Do you like seeing interesting marine creatures, or paddling local waters in a kayak? We are seeking volunteers for our Dungeness crab and bull kelp monitoring programs in 2024. Please contact us for more information.

Ecosystem Technician Alistair Marr-Paine monitors bull kelp for the Mayne Conservancy in 2023.

Further reading – kelp in the spotlight

Canopy forming kelps have been big news in recent years, with growing concerns about the future of these important species and the ecosystems they create. Studies have ranged from attempting to determine what causes the observed kelp changes (predator prey relationships? warming oceans? pollution?) to investigating sustainable harvesting techniques and restoration methods. The need to find answers to these questions has driven successful efforts to improve monitoring methods using satellites and drones. Below are some brief descriptions of kelp-related work and studies being completed in the region for those interested in learning more:

Visit the Conservancy Kelp Monitoring website page.

Urchin Barrens in the SGI? – Thankfully, urchin barrens are not a common occurrence in the Southern Gulf Islands, but is that changing? Recent work led by the Saturna Island Marine Research and Education Society (SIMRES) has documented an urchin barren along the southeast shore of Saturna Island, an area known as Cliffside. The barren extends north to East Point, a well-known foraging route for the endangered Southern Resident Killer Whales. Efforts are being made to understand why an urchin barren has established at that site and to figure out if there are other sites in the Southern Gulf Islands. The results of our monitoring could help identify other places in the Southern Gulf Islands where this is occurring.

Green urchins occur in abundance along the rocky shore of Cliffside, Saturna Island. Photo taken by Maureen Welton.

Starko et al., pre-press: This study collected data from across British Columbia (including our data) to describe changes in kelp in different parts of the province. They show areas affected by marine heat waves declined in the south of the province, and attribute declines observed further north to loss of predators and resulting increase in sea urchins.

Mora-Soto et al, 2024 – This study led by researchers at the University of Victoria used satellite imagery to detect change in bull kelp in the South Salish Sea. They show a connection between periods of warming water and changes in kelp abundance, with a discussion of how site-specific conditions such as wind and wave exposure affect changes in kelp. In the locations where this monitoring program overlaps with ours, the observations are consistent.

Berry et al., 2021 – Kelp decline in South Puget Sound.

McPherson et al., 2021 – Kelp decline in California.

Kelp Forest Monitoring Alliance of Washington State – South of the border the Washington State Department of Natural Resources and many partners have been working for decades to understand changes in floating kelp species. They recently created an interactive map that summarizes the data by location. Like British Columbia, kelp loss is being observed in places that have experienced more extreme marine heat waves, such as in southern Puget Sound. Some of the monitoring as part of this initiative is driven by volunteer kayakers, just like our monitoring program!


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