Amphipods generally appear compressed from the sides, but Corophium species appear more flattened (as if compressed from the top) than most amphipods. In Corophium the 2nd pair of antennae (lower pair) are conspicuously enlarged and give the appearance of arms extending in front of the head. There are long setae on the gnathopods (leg-like limbs behind the head).
Corophium is more often recorded in estuarine than fresh water sites, and it is possible that the species pictured is an adventive (introduced) species. They are thought to burrow into muddy beds.
Corophium are filter feeders using the long setae on their gnathopods to trap suspended organic matter.
The presence of Corophium may indicate sea water influence. They have not been assigned tolerance values, but the general amphipod values are 5 (hard bottom sites) and 5.5 (soft bottom sites).