The Spread of the Ribbon Sea lettuce across oceans

The Ribbon Sea Lettuce (Ulva reticulata) is an algae-type species that has been introduced to many oceans like the Atlantic, eastern Pacific, and Indo-west Pacific oceans. One of its pathways for introduction has been said to be ballast water via shipping. Ballast water is what ships or large vessels use to maneuver under bridges or to not sink below depth. Ballast water is usually contained in the ship’s ballast tanks, which can also harbour small barnacles, algae, and microorganisms like the ribbon sea lettuce.

The Ribbon Sea lettuce was recently reported to be in the Atlantic Ocean, specifically in Venezuelan waters. It grows on rocky substrates but can become free-living vegetative algae after maturing and detaching itself.

Once the ribbon sea lettuce penetrates coral reefs and starts competing with other benthic species, its invasiveness becomes localized. This algae can have green tides or massive algal blooms because of high nutrient influx. In the Caribbean region, the Tourism sector is a major industry, dependent on its aesthetically clean beaches to entice beachgoers, swimmers, and tourists alike.

U. reticulata can have negative socio-economic impacts on tourism because of its massive algae growth. The ribbon sea lettuce gets its growth from high nutrients caused by eutrophication via human factors such as untreated sewage. The tide blooms can cover clear water and sandy beaches impeding tourists and locals. For example, in the early 2000s, the Philippines suffered because of the green tidal blooms, which decreased tourism. Another similar event occurred during the 29th Olympic Games held in Qingdao China, where more than 10,000 people and 1,400 boats had to be cleaned after the massive algal bloom interrupted the sailing event.

This invasive algae is a cause for concern as it is currently on the high-risk watch list according to a risk analysis conducted by Barbados and the OECS countries. This risk analysis evaluated potentially invasive species vectors and the aquatic species that are more likely to be introduced into the region via shipping (ballast water, biofouling), aquaculture (fish farming), and aquarium trade (aquarium releases).

Currently, a method to prevent Ribbon Sea lettuce and other forms of algae, barnacles, and microorganisms is Ballast Water Management. The Ballast Water Management Convention was implemented by the IMO and signed by all Caribbean countries sans St. Vincent and the Grenadines and Dominica. The convention allows for proper protocols and measures to be used for vessels and their ballast water, i.e., emptying ballast water tanks of any non-native species.

Read more about this from our sources below!


Marine Risk Assessment Final Report – Ribbon Sea Lettuce

CABI – Ribbon Sea Lettuce

Algae BaseUlva reticulata Forssk√•l 1775

IMO – Implementing the Ballast Water Management Convention