for Pacific Northwest waters. Our normal surface water temperatures range from about 9ºC (~48ºF) in winter to 13ºC (~56ºF) in summer (varying not just with season but with tide cycle, river runoff, the Pacific decadal oscillation, and other factors). Sometimes in summer it heats up excessively and our community of marine creatures suffers. After the spell of clear sunny weather we've had lately, there are areas in the Salish Sea that have warmed up into a range where we're starting to see effects on sea life. These are most extreme in shallow protected bays right now, but as the temperature of these inland waters increases with global warming, we can expect to see this more often.
Here's what I've been observing over the past week.
What you see there on the right is a streak of a massive yellowish-green Harmful Algal Bloom (HAB) which appeared on July 9.
The Daily Bucket is a regular feature of the Backyard Science group. It is a place to note any observations you have made of the world around you. Rain, sun, wind...insects, birds, flowers...meteorites, rocks...seasonal changes...all are worthy additions to the bucket. Please let us know what is going on around you in a comment. Include, as close as is comfortable for you, where you are located. Each note is a record that we can refer to in the future as we try to understand the patterns that are quietly unwinding around us.
What's going on in this bay? Follow me below the fold for the story.
(All photos by me. In Lightbox...click to enlarge)
I kayak around in this bay near my house frequently. Lately I've been observing the rocky shorelines closely, monitoring the incidence and progression of Seastar Wasting Syndrome (SSWS) (update on that anon). Of all the sites I had checked on my island, this stretch of shoreline on the east headland is the only place I had seen any affected seastars. These photos were taken last Sunday, July 6.
Closer to the headland, I paddled into this indentation through deep green waters. I was taken aback by the hundreds of juvenile Dungeness crabs hanging out in there! This eelgrass bay is a great nursery for young crabs, with abundant prey for them (small fish and invertebrates). However, young crabs are favored food for fish and gulls, so they tend to congregate in protected spots like this alcove.
Look how clear the water was that day! I was happy to see this healthy Ochre seastar.
On Tuesday July 8 I noticed a marked yellowish opacity to the water in the bay along the shore and in the southeast corner of the bay. The water felt unusually warm.
The next day, July 9, I brought my plankton net and a thermometer. Out in the middle of the bay, the surface temperature was 15ºC (60ºF), and about 5 feet down, a little cooler, 14ºC.
Paddling over to the eastern side of the bay, I entered the bloom.
Water temperature there was 18.5ºC (~67ºF), as far down as I could measure. Along the shoreline it was even warmer. One spot, in the very SE corner, where the wind has been blowing sun-warmed surface water, I measured 22.5ºC (~75ºF)!
The plankton sample I collected was swarming with one kind of organism, Heterosigma akashiwo. It's the tiny golden potato-shaped critters in this photo I took. There's a fragment of a diatom (with the filaments), much larger, for comparison. Very few living diatoms. A few dinoflagellates, like the urn-shaped Dinophysis on the left. Some tintinnids, like the vase-shaped creature on the right, were zooming about snapping up the Heterosigma.
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Heterosigma akashiwo is a unicellular planktonic organism that both photosynthesizes and ingests bacteria. It is lethal to fish who swim through a bloom like this, evidently clogging their gills, suffocating them. It is toxic to some invertebrates also, including zooplankton.
At Crab Cove, the translucent water had turned murky, and no crabs or seastars were to be seen.
Small dead fish, nudibranchs and jellyfish floated by.
I did see otters though, and a seal, fishing elsewhere in the bay. This bloom is not toxic to the predators and scavengers of fish.
While Heterosigma blooms are seen commonly in summer, they are increasing in frequency and magnitude in the Salish Sea. Dormant cysts in the sediment are activated by 15ºC water and have maximum toxicity at 20ºC (~70ºF). Warm water triggers these HAB blooms.
The following day, July 10, I was relieved to see the water in the bay clearing somewhat. Tides flush this bay vigorously (30% every tide cycle), so the thick bloom was dispersing. Here's a view of Crab Cove on Thursday.
Last night at sunset we saw fish jumping near the beach, though not over on the eastern side of the bay. Today (July 11) the water is considerably more clear, although the temperature is still high, 17ºC (~64ºF), so I wouldn't be surprised to see another bloom here.
Models of future sea temperatures in these waters, such as in this report by the Climate Impacts Group, University of Washington, predict an increase over the next century of several degrees. Salmon, already on the edge of extinction due to overfishing, dams, clearcutting and habitat loss, may well be pushed over the edge by warmer water alone. Certainly, more frequent Heterosigma HABs will further stress the marine ecosystem here as a whole, from zooplankton to fish to orcas.
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Time for you to share your observations. What's up in nature in your backyard today?
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