July 16, 2018
Salish Sea, Pacific Northwest
With the warmer than normal temperatures we’ve been having lately and the long sunny summer days, we’ve been seeing a massive proliferation of algae in the local bays. Blooms like these are not unprecedented, but they are a reminder of how quickly aquatic populations can change.
I’m seeing both macroalagae and microalgae blooms. Macroalgae is the big stuff aka seaweeds, like what’s piled up along the shore here. The local brown algae, Rockweed, is growing as it always does, on rocks, not especially abundant. But the green algae Sea Lettuce has exploded in growth as it’s been doing the past few years.
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Another green macroalgae, the stringy Grass Kelp, has also bloomed. Green algae are particularly fast growing.
Sea Lettuce has proliferated so quickly it’s filling local bays, getting floated by high tides and then settling on beaches when the tide goes out. A killdeer pokes around a mass. Decaying seaweeds attract small amphipods which are food for birds. The seaweed itself is food for geese.
Some animals are making use of the abundant Sea Lettuce but it has negative effects too. It smothers eelgrass, and when it dies, its decomposition depletes aquatic oxygen, stressing marine animals.
Microalgae is also blooming. I haven’t gotten out my plankton net but this one is obvious by its color. This is Noctiluca, sometimes known as Tomato Soup algae for the intense opaque orange it takes on in very shallow water. Noctiluca is a dinoflagellate, a single celled algae.
Noctiluca is a “red tide” but not toxic per se. However it has negative effects in an ecosystem, as described by biologists:
The orange-colored species does not produce any toxins found to be harmful to humans, but it is not exactly a friendly organism either. It often shows up in marine waters that are out of balance with nutrients or impaired in some other way. It can gobble up other plankton that feed tiny fish and other creatures, but it does not seem to provide a food supply that interests very many species — probably because of its ammonia content. Consequently, Noctiluca is often referred to as a “dead end” in the food web. pugetsoundblogs.com/...
There are other microalgae species proliferating in Salish Sea waters right now. State testing warns against eating any shellfish in my area due to presence of biotoxins:
These explosions of algae are not unusual, and in fact our water temps have been cooler this summer than in the past few “Blob” years, near historic average, but the increasing masses we’ve been seeing is a sign of elevated nutrient levels. That comes from terrestrial runoff: natural and human caused, like sewage and fertilizers. The latter have been increasing. As Washington state Dept of Ecology says, about Noctiluca,
Noctiluca contains high concentrations of ammonia which make them unappetizing prey in the food chain. Studies have shown this ammonia has a negative impact on juvenile fish within the population. When large blooms of Noctiluca exist in Puget Sound, their ravenous feeding patterns lead to a boom-and-bust of the plankton populations.
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While
Noctiluca are naturally occurring and blooms have been observed and recorded in Puget Sound since the 1940’s, there is growing concern that human-caused nutrient over-enrichment is increasing the intensity, changing the timing, and increasing the spatial distribution of
Noctiluca blooms.
ecologywa.blogspot.com/...
What’s the high summer nature news where you live?
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