Type of Presentation

Oral

Session Title

General Marine Habitat

Description

Accumulations of beach-cast seaweeds and other matter, collectively known as wrack, are a common and ecologically important occurrence along coastal regions worldwide. Between the unincorporated communities of Deep Bay and Bowser, on the east coast of Vancouver Island, beach wrack is primarily composed of an introduced species of red algae called Mazzaella japonica, which became the target of a commercial beach-cast harvest in 2007. Little is known, however, about the ecological role of M. japonica in this recipient system. Furthermore, literature on the effects of harvesting beach-cast seaweed is limited. The goal of this research was therefore threefold: 1) To quantify the contribution of M. japonica to wrack inputs within the harvest region; 2) to explore how wrack characteristics influence macrofauna communities; and 3) to determine if the commercial removal of beach-cast seaweeds has a detectable effect on wrack characteristics and macrofauna community structure. To answer these questions we monitored a series of permanent transects at six sites across the harvest region, from November 2014 until March 2015. We recorded as much as 853 kg (±99.8 SE) of wrack per meter of shoreline, 63 % to 82% of which was identified as M. japonica across sites. Despite the removal of 674.5 tonnes of beach-cast seaweeds, we found that the trends in wrack biomass were similar between both harvested and unharvested locations. Macrofauna communities differed significantly between study sites, as well as with the age class, depth, and total biomass of the wrack from which they were sampled.

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Beach wrack communities within a commercially harvested coastline of the Salish Sea

2016SSEC

Accumulations of beach-cast seaweeds and other matter, collectively known as wrack, are a common and ecologically important occurrence along coastal regions worldwide. Between the unincorporated communities of Deep Bay and Bowser, on the east coast of Vancouver Island, beach wrack is primarily composed of an introduced species of red algae called Mazzaella japonica, which became the target of a commercial beach-cast harvest in 2007. Little is known, however, about the ecological role of M. japonica in this recipient system. Furthermore, literature on the effects of harvesting beach-cast seaweed is limited. The goal of this research was therefore threefold: 1) To quantify the contribution of M. japonica to wrack inputs within the harvest region; 2) to explore how wrack characteristics influence macrofauna communities; and 3) to determine if the commercial removal of beach-cast seaweeds has a detectable effect on wrack characteristics and macrofauna community structure. To answer these questions we monitored a series of permanent transects at six sites across the harvest region, from November 2014 until March 2015. We recorded as much as 853 kg (±99.8 SE) of wrack per meter of shoreline, 63 % to 82% of which was identified as M. japonica across sites. Despite the removal of 674.5 tonnes of beach-cast seaweeds, we found that the trends in wrack biomass were similar between both harvested and unharvested locations. Macrofauna communities differed significantly between study sites, as well as with the age class, depth, and total biomass of the wrack from which they were sampled.