Sea Lettuce - A "Growing" Problem

The rampant growth of sea lettuce in North Bay, Warrens Cove and Prince Cove, and its harmful effects on aquatic biota and shorelines continues to be a major concern of many of our members. To address this problem, our Board has voted to investigate the feasibility of sea lettuce removal in these areas.

Sea lettuce and dead blue crabs in North Bay
August, 2003

The negative impacts of sea lettuce growths are many. These include damage to, or even the killing of, shellfish, crabs, bottom dwelling organisms, eelgrass, and shoreline grasses. Decaying sea lettuce and other undesirable algae deposited on shore are not only unsightly but also create obnoxious odors and breed large quantities of undesirable flying insects.

One scientific study has shown that sea lettuce "is detrimental to estuarine invertebrates due to the production of toxic exudates and low oxygen tensions which occur in the seaweed beds at night". Mortality to blue crabs may occur within minutes after such conditions arise. Many other studies have shown that sea lettuce mats on the bottom layers of an estuary "likely kill some non-mobile species, such as polychaetes (worms) and sedentary mollusks".

Initially, our program will gather relevant information from scientific and conservation organizations around the world that have studied sea lettuce effects on water quality and biota. Of special interest will be those locations that have actually tested or practiced sea lettuce harvesting or removal, including the methods used, and the positive and negative impacts observed. As sea lettuce removal could adversely impact some species, our research will also identify the potential of unwanted bycatch resulting from harvesting, as well as loss of habitat or food.

This exciting new initiative will help us all to understand the effects of sea lettuce and other harmful algae on the Three Bays' flora, fauna, and water quality, and how we might stem their unwanted growth.

Don Schwinn, Chairman of our Technical & Scientific Committee, will lead the effort.