Photo: Will Husby
Deeper Waters
Plankton
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A breathtaking miniature world of beauty lies hidden beneath the surface of Kwilákm. Plankton are free-floating plants (phytoplankton), animals (zooplankton), and bacteria (bacterioplankton) of infinite form, function, and design.
Some are easily seen, such as jellyfish.
But most are less than a millimetre long. Many can be seen only with the aid of a microscope.
But they can be present in the water in the millions, their bodies colouring the waves and blocking light penetration.
Plankton are of immense ecological importance in Kwilákm and throughout the oceans of the world. Many marine creatures, ranging from other plankton creatures, to anchovies and juvenile salmon, to whales, depend on these tiny plants and animals for food.
Phytoplankton
These microscopic, usually single-celled plants drift in the ocean. They provide essential ecological services, including oxygen production and carbon storage, through photosynthesis. They exist in the billions in the first few metres of the ocean surface, and are the foundation of most marine food webs.
Phytoplankton produce 50% of the oxygen that we breathe.
Watching Phytoplankton
Like land plants on Bowen, phytoplankton in Kwilákm have seasonal growth cycles. Keen observers can see the changes in the colour and clarity of the ocean surface.
In winter, even though storms mix deep nutrient-rich waters with surface waters, the water is too cold, and sunlight is too weak for much phytoplankton to grow. And so, the seawater is generally clear.
In spring, days become longer, the ocean surface warms, and the amount of sunlight increases. These factors, along with the abundance of minerals from freshwater runoff and upwelling from the depths, create ideal conditions for phytoplankton. Although individual plants are too small to see without aide of a microscope, plankton blooms can colour the ocean.
In summer, phytoplankton growth continues and the ocean remains murky, clouded by live phytoplankton and the many small creatures that feed on them. As summer progresses, there are fewer dissolved minerals in the surface water, plankton populations decrease, and the water clears.
Fall winds often stir up the waters, bringing mineral-rich water from the deep to the surface, resulting in fall phytoplankton blooms.
Zooplankton
Zooplankton are animal plankton. They include many bizarre-looking representatives and all major invertebrate groups, including some that can only be found in the plankton.
This group also includes vertebrates such as fish eggs and larvae.
They eat either phytoplankton or each other. Most are microscopic, but some are large enough to see with the unaided eye.
Pacific krill, tiny relatives of prawns and lobsters, are important zooplankton in Atl’ka7tsem/Howe Sound.
In the 1980s, they were so plentiful that there was a short commercial fishery in the Sound. This keystone of the marine food chain was hunted for use in tropical fish food and fertilizer.
Like phytoplankton, zooplankton drift with the currents, and although most can swim, they cannot progress against currents.
Bacterioplankton
These mostly single celled organisms are tiny, ranging in size from 0.5 to 50 micrometres (1×10-6 metre). We can’t see them with the naked eye. Scientists study them using powerful electron microscopes. Bacterioplankton include uncounted species, and thousands may be found in a single drop of water. Almost all are harmless to people. Some bacterioplankton are primary producers, using chlorophyll to convert sunlight into sugar. Most are primary consumers eating dead and dying plankton, mostly phytoplankton.
Studies in Atl’ka7tsem/Howe Sound in the 1980s found that their population follows the annual population cycle of phytoplankton: lowest numbers are in mid-winter, greater in spring, greater again in summer, and greatest in early fall (immediately after the die-off of phytoplankton).
In the local food chain, they are the key food of cloud sponges.
A New Plankton Survey of Atl’ka7tsem/Howe Sound
Since seminal research on the plankton of Howe Sound took place in the 1970’s, there was no further studies on the ecological health of plankton until very recently. As part of the Howe Sound/Atl’ka7tsem Marine Reference Guide, Tides Canada, and the Marine Science Foundation have begun a multi-year survey of plankton in the Sound starting in summer 2020.
This much-needed study will provide baseline population data that may be used in the ongoing monitoring and management of marine food webs in the Sound.