Dolf DeJong is the vice president of conservation and education at the Vancouver Aquarium Marine Science Centre. He is currently on assignment at the Oceanografic Aquarium in Valencia, Spain, supporting the staff of Europe’s largest aquarium as they expand their conservation and education efforts. His On Assignment blog series chronicles some of his adventures and experiences while he’s on dispatch in Spain.
When we made the decision to update how we managed the 11 million litres of outdoor lakes at the Oceanografic Aquarium in Valencia, Spain we anticipated seeing some significant changes. With the addition of the new waterfall and updated operating practices, we expected the pools to transition from the existing blue to a more natural green as the algae began to grow and insects and other species to move in.
Many people are unaware that healthy water in a natural functioning ecosystem is not usually clean and clear like the water flowing from our kitchen taps. Untreated water contains all sorts of tiny organisms, plankton and aquatic plants — important building blocks for larger animals further up the food chain.
The barn swallow (Hirundo rustica) is a pretty little bird with a blue back and forked tail — its nesting preference is on human made structures such as barns and bridges. A large number of these birds pass through
the area as they migrate from Southern Africa to Europe to nest. A few even stay in Valencia for the summer, nesting near Oceanografic under the Calatrava-designed bridge between the Agora and the Science Museum. What was significant this spring was the total number of barn swallows feasting over our new “living lake.” It was the highest number of the birds staff had ever seen at the Oceanografic site.
The returning barn swallows are insectivores: birds who make their living catching and eating flying insects. This year at Oceanografic we have been seeing far more flying insects in the early evenings over our “living lake.” The healthy state of the water at the site has attracted these wild bird species to come feed by the lake; which is certainly a win for both the individuals nesting locally and those continuing on to nesting sites further north.
We’ve had some people question if the water is now “dirty” at Oceanografic and wonder how the animals in our care will react. To answer that question — the ducks, swans and other waterfowl who live year-round at the Aquarium are predominately dabbling feeders who are happy to consume aquatic plants and algae. These changes have provided a healthy enrichment to their current diet and the only real “downside” to the green-ish water is that it’s not as aesthetically pleasing for some people who prefer the blue bottomed habitats to the more natural greens.
We celebrate the benefits of the upgrades to the lakes for the animals in our care and for the champions of migration who pass through the region twice a year. We are all looking forward to seeing the birds again in the fall when they pass through once more on the way back to their winter homes.