The jagged edge of the Gretagrund Shoal’s underwater sandstone plateau

Gretagrund (Gretagrund Shoal) is in the Gulf of Riga – a huge underwater sandstone bank, which, in some places, is only a couple of meters below the surface of the sea. It is located about 10 km south-east of the Island of Ruhnu.

This is one of the most unusual and interesting sea areas in Estonian coastal waters. In comparison to the almost fifty-meter-deep sea surrounding it, the shoal is very rich in marine life, including both more common and rarer sea creatures. On this sandy and granular sea bottom live the bay barnacle (Balanus improvisus) as well as the Sphacelaria arctica. In the course of researching the bottom dwellers of the Gretagrund Shoal, a brand new species was found in the Baltic Sea – the mysid shrimp Paramysis intermedia. In the course of fish studies, it became apparent that the Gretagrund Shoal is Estonia’s most important spawning area for the lavaret. Brown trout and cod have also been caught here.

Bird studies have clearly shown that the Gretagrund Shoal, along with the Ruhnu Island area, is an essential resting spot for a variety of water birds (for instance, the long-tailed duck, velvet scoter, diver, etc).

To protect the Gretagrund Shoal environment, a limited conservation area has been created.

• Jonne Kottaa and Tiia Möller. Important scales of distribution patterns of benthic species in the Gretagrund area, the central Gulf of Riga. – Estonian Journal of Ecology, 2009, 58, 4, 259–269
• Projekt „Gretagrundi madala piirkonna põhjaelustiku ja elupaikade inventuur” Eestimaa Looduse Fondi kodulehel (reports, video and photos; in Estonian)
• E. Vahtmäe. Ka mere-elupaigad väärivad kaitset. – Eesti Loodus 2, 2011 (in Estonian)

Created in 2013