The sea shore is the best known ecosystem of the sea, although really only a handful of species can be found there. The reason it is best known is of course because this is the most accessible part of the sea for us landlubbers.
   
The seashore is a diverse habitat, from mudflats to wave battered rocky shores. Rocky shores are mostly found in outer peninsulas where the waves clean away all the loose debris. Gravel beaches, which are widespread in Eyjafjörður are where it is more sheltered, but mud beaches are at the mouths of rivers where silt from the rivers accumulates into fine sediments. These types create different conditions for organisms and species composition is therefore quite different.
   
Seashores are quite different between regions. Almost all the south beach is sandy and wave battered. There are few organisms there because it is difficult to live with the ever-changing sand. Variety of seashores are found in the east and north but rocky shores are the most common. However, species diversity is low there because the sea is cold and species diversity is lower in cold waters that  warm.
    
Another reason for low species diversity in Eyjafjörður is that tides are low, and the seashore therefore narrow. The most diverse seashores in Iceland are along the west coast, where the ocean is relatively warm and tides are large. There the largest mudflats can also be found, very important feeding areas for waders in Iceland.  
 
There is also a species diversity gradient within the fjord because more species are found in the outer part of the fjord. Most likely this is because of freshwater runoff from the rivers. Most marine organism do not like fresh water and most freshwater organism do not like the saline ocean. Therefore relatively few species thrive where these two ecosystems meet.
 
HV

Bóluþang í fjöru. (Mynd: Tryggvi Sveinsson) Bóluþang í fjöru. (Mynd: Tryggvi Sveinsson)

Ýmis dýr finnast innan um þangið, hér eru nákuðungar, kræklingur og hrúðukarlar. (Mynd: Tryggvi Sveinsson) Ýmis dýr finnast innan um þangið, hér eru nákuðungar, kræklingur og hrúðukarlar. (Mynd: Tryggvi Sveinsson)