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01.10.24 All, Commentary, Legal, Scientific

Letter in the Ellsworth American, “The Truth About Rockweed” (12/14/23)

David Porter, of Brooklin, describes misleading publicity about a recent scientific paper published by researchers at the University of Maine and the Maine Maritime Academy.

https://www.ellsworthamerican.com/opinion/letters_to_editor/the-truth-about-rockweed/article_ae6e415c- 9a97-11ee-8159-434b736616b8.html

The truth about rockweed

Dec 14, 2023

Dear Editor:

Rockweed is a slow-growing, wild seaweed on the rocky coast of Maine. It is highly valued as a commercial fertilizer and debates about how rockweed harvesting should be managed are contentious. To wit, the next State Legislature will be voting on LD 2003 to open the entire shoreline to unlimited rockweed harvesting.

To address questions about overharvesting, academic researchers collaborated with commercial companies to test for effects of a single harvest on rockweed biomass (amount) and height one year later. Their article, “Bed-scale impact and recovery of a commercially important intertidal seaweed,” by Johnston et al., is in the Journal of Experimental Marine Biology and Ecology (2023).

Their study has been widely publicized as evidence for rapid recovery of commercially harvested rockweed beds throughout Maine. For example, in the Working Waterfront Newspaper (December 2023, Op-Ed Maine Seaweed Council) — “The bottom line from the University of Maine is that rockweed regenerates at a rapid rate, fully recovering its biomass within a year of harvest.”

However, the researchers identified limitations of their study that are not mentioned in this publicity. Many published studies come with caveats — here, it is especially critical to acknowledge these limitations when the findings are used in policy and management decisions.

Figure 1 – Map and number of study sites; from Johnston et al. 2023.

Briefly, the goal of the study was to test for the effects of harvesting on rockweed one year later, at the level of entire rockweed beds. Commercial harvesters were asked to cut rockweed at half of the study sites along four regions of the coast. Surprisingly, in the harvest year, no harvesting effects were detected at three of the four regions (only 10 small samples were collected at each site). Sweeping statements asserting that there was rapid, full recovery after one year fail to acknowledge many sites where there was no documented impact from which to recover.

Where the researchers did detect harvesting, they stated that “it is important to note that the likelihood of complete height and biomass recovery after one year was lower at these more disturbed sites.” In summary, these details matter.

David Porter

Brooklin

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