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BY THE BAY: Amazing phytoplankton - Heritage Afloat
The theme of this year’s Heritage Week (Feb 17 to 23) is ‘Heritage Afloat,’ and a variety of activities are planned around the community to celebrate Captain Vancouver’s voyages, fishing, and so on. These are the traditional concepts of heritage and will be interesting and fun. Yet we should also consider the natural heritage that has supported an unbroken chain of human life since the end of the last ice age.
Delta’s heritage includes the Fraser River that brings life-giving freshwater to the lowlands and deposits sediments that build up the delta landscape. It includes the salt waters of the Georgia Strait washing our shores, their ebb and flow creating the estuarine ecosystems of marsh and slough.
Afloat in all these waters are microscopic, light-loving phytoplankton, literally ‘plant wanderers’, that drive the food chain as they drift the waters of the world. These tiny organisms capture sunlight in ring-shaped molecules of chlorophyll.
During photosynthesis, the world’s phytoplankton absorb carbon dioxide from the air and release half the earth’s oxygen.
What more essential organisms could there be?
Phytoplankton thrive in the presence of certain nutrients, such as nitrate, phosphate and iron.
This is why a group from Haida Gwaii attempted, controversially, to increase phytoplankton by depositing iron into the ocean.
With good conditions, plankton proliferate rapidly, causing extensive blooms. These attract herbivores which are then preyed on by carnivores.
Harmful algal blooms, and subsequent death of marine life, can occur from eutrophication, the excessive nutrient enrichment caused by agricultural run-off or poor water circulation. Eutrophication is a concern on Roberts Bank, where tidal movements are affected by port and ferry causeways.
The marine food web is complex. As organisms at the lowest level, phytoplankton provide food for a host of slightly larger creatures, including zooplankton (‘animal drifters’) like jellyfish and the tiny larvae of fish, and crustaceans such as copepods and krill.
Copepods are a huge source of protein for fish, seabirds and mammals. Krill, one of the smallest animals on earth, is eaten by blue whales, the largest. Delta is a maritime community, built from the watery landscape at the mouth of the mighty Fraser river.
The lowly phytoplankton is the epitome of Heritage Afloat, as it drifts the planet’s waters, making life possible by changing sunlight into life’s breath and food. For Heritage Week events in Delta, see www.corp.delta.bc.ca
• Anne Murray is an independent writer, naturalist and author of two books on the natural history of Boundary Bay: A Nature Guide to Boundary Bay and Tracing Our Past ~ A Heritage Guide to Boundary Bay, www.natureguidesbc.com. She blogs at www.natureguidesbc.wordpress.com