Chapter

Ecology of Baltic Coastal Waters

Volume 197 of the series Ecological Studies pp 217-243

Gulf of Riga and Pärnu Bay

  • J. KottaAffiliated withEstonian Marine Institute, University of Tartu
  • , V. LauringsonAffiliated withEstonian Marine Institute, University of Tartu
  • , G. MartinAffiliated withEstonian Marine Institute, University of Tartu
  • , M. SimmAffiliated withEstonian Marine Institute, University of Tartu
  • , I. KottaAffiliated withEstonian Marine Institute, University of Tartu
  • , K. HerkülAffiliated withEstonian Marine Institute, University of Tartu
  • , H. OjaveerAffiliated withEstonian Marine Institute, University of Tartu

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The Gulf of Riga (Fig. 10.1) is a relatively shallow and isolated water-body with a surface area of 16,330 km2. On its eastern and southern sides it is flanked by the Estonian and Latvian mainlands, and on the northern side by the islands of Saaremaa and Muhu. The Gulf of Riga is connected to the Baltic Proper via the Irbe Strait, and to the Väinameri Archipelago Sea by the Suur Strait. Annual river inflow (Table 10.1) ranges between 18 and 56 km3 (on average 32 km3), while the volume of the gulf is 424 km3. The residence time of water masses is 2–4 years (HELCOM 1996). The Gulf of Riga receives fresh water from a huge drainage area (134,000 km2), mostly entering the southern part of the basin (Andrushaitis et al. 1995). In general, the bottom relief of the area is quite flat, with gentle slopes towards deeps. The northern part of the Gulf is characterised by a wide coastal zone with diverse bottom topography and extensive reaches of boulders. The southern part of the Gulf of Riga is more exposed; steep and soft substrate prevails. In the deeper parts of the Gulf, silty sediments prevail.