The islet of Alegranza, to the north of Lanzarote, is 10.2 square kilometers in size, being the largest in the Chinijo archipelago of the Canary Islands. This uninhabited island, the northernmost, is the first obstacle crossed by the Canary Current and for this reason it has gone from being a natural paradise and biodiversity refuge to a garbage dump. The first inventory of marine debris in Alegranza removed 3,667 objects weighing 321 kilos, 97.7% of which were plastic.

The lobster trap labels, dating from 1999 to 2018, come from North America, evidencing not only the journey of these materials that have crossed the Atlantic but their long life in the ocean.

The study has been carried out by Alicia Herrera, Alexis Rivera, Teresa Moreno, Ico Martínez and May Gómez and published in Science Direct.

The objective is to take a census once a year in the same area to estimate the annual contribution of marine litter and analyze the trend in each category of litter studied.

Of the total objects analyzed, 97.7% were plastic, the most abundant being beverage bottles (25.4%). While it is difficult to know the origin, source, and route of the debris, the legible labels provided valuable information linking marine debris to three continents.

Alegranza is protected by the figure of the Natural Park of the Chinijo Archipelago and has also been recognized as a special protection area for birds (ZEPA). It is a key habitat for the Cory's shearwater, among other species, and for being the largest marine reserve in Europe, with 700 square kilometers. Alegranza has been uninhabited since 1968 and receives very few visitors, mainly scientists, since access is prohibited and permits are required.

The Canary Islands lie off the northwest coast of Africa, disturbing both currents and surface winds, and the average permanent current is the southwest Canary Current. This geographical location is a hot spot for the accumulation of marine litter, since all the litter dragged by the Canary Current is deposited on its northeast coast. The archipelago is especially vulnerable to plastic pollution, as ocean currents carry marine debris from the east coast of the United States and Canada, North Africa and Europe to its shores.

The waste study focused on Caleta del Trillo, a coastline approximately 100 meters long, which accumulates a large part of the island's marine debris, due to its orientation, which exposes it to the prevailing winds and currents. A first visual inspection was carried out, followed by five cleanings in 2020, according to the sampling methodology proposed in the OSPAR protocol.

A total of 3,667 items weighing 321 kilos were removed, of which 97.7% were plastic, 1.9% textile and 0.4% metal, and no paper or cardboard objects were recovered. Most of the objects removed were made of plastic, so the type of plastic object, the possible origin and the sources were analyzed. The most abundant everyday plastic objects were PET bottles, plastic fragments and caps.

A noteworthy fact is the enormous number of beverage bottles that arrive in Alegranza, both from maritime traffic and from unknown origin, which account for 25.4% of the pieces found. Plastic bottles are among the top five global litters in all settings, accounting for 12.9% of items found on the shoreline.

Among the plastics derived from maritime traffic, the abundance of ropes and buoys stands out, while among the objects derived from aquaculture, the presence of sticks of mussel farming ropes and labels of lobster pots from the east coast of the United States and Canada predominates. .

Regarding the possible sources, 50.2% corresponds to consumers of the general public with an unknown route, 20.2% comes from maritime traffic and fishing, 2% comes from activities related to aquaculture, while the 27.6% are fragments from unknown sources.

Lobster license tags provided important information about geographic origin, pathway, and sources, as well as the date they entered the ocean. Most of the tags come from the coasts of Maine and Massachusetts, and from the east coast of Canada. All of them come from aquaculture in this region and have been dragged to the Canary coasts by the Canary Current. Regarding the date, licenses have been found from 1999 to 2018, this data shows that there are plastics that may be more than 20 years old in the sea and are still in good condition and with legible labels.

The scientists in charge of the study consider that it is crucial to continue cleaning, studying and classifying the marine debris that reaches Alegranza through the Canary Current to determine the changes that occur over time in the type of waste and its sources. In this way, managers and policy makers will be able to evaluate the effectiveness of the environmental policies applied and define the new conservation policies to be implemented.