Restoring Baltimore's Inner Harbor, One Biohut at a Time

In June 2014, eight Biohuts were installed on the bulkheads in Baltimore's Inner Harbor just outside the Aquarium. The Biohut is a double cage system where one side is filled with oyster shells that attract rapid colonization by microorganisms. The oysters are seeded with spat (juvenile oysters) that grow and serve as biological filters by filter feeding and removing algae from harbor water.

Mussels and barnacles attach and grow on the oyster shells and also act as living filters in these urban waters. The outer cage is empty and provides only shelter, offering a predator-free zone for juvenile native fish. The double cage system of the Biohuts restores some of the ecological function once provided by the natural landscapes historically found in this area.

The Biohuts are monitored by our team each week using an underwater camera to capture activity within the hut. Species found on camera so far include: striped bass (Morone saxatillis), gizzard shad (Dorosoma cepedianum), common grass shrimp (Palaemonetes pugino), mummichog (Fudulus heteroclitus), white perch (Morone americana), banded kilifish (Fudulus diaphanous), blue crab (Callinectes sapidus) and pipefish (Syngnathus fuscus).

To better understand the success of the project, two of the Biohuts were temporarily removed from the water for dissection exactly one month after their launch. In total, 462 white-fingered mud crabs (Rithropanopeus hirrisii) and 417 common grass shrimp were observed living within the oyster shells. In addition, three further species were documented, including American eel (Anguilla rostrate), naked goby (Gobiosoma bosci) and Atlantic silverside (Menidia menidia).

The Aquarium will continue to monitor Biohut activity through the fall, so stay tuned for updates.