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.
September 1, 2015
Salish Sea, PNW
A soup of drifting microscopic creatures supports the wealth of life in the Salish Sea. No plankton...no orcas, salmon, birds, seastars, crabs, seals, you name it. Plankton is seasonal like everything in this latitude, and the days are getting markedly shorter now. I thought it would be fun to see what's floating around out there right now in late summer. Sunlight energy and the nutrient store from last winter are both winding down now, but the water is still a rich opaque green, a sure sign of planktonic life. I used a plankton net that filters water, sweeping it back and forth 30-40 times, and the plankton too large to go through the net collected in the bottle at the end.
Looking at the samples with my digital microscope, I found the seawater in the bay is very busy right now. Here's some of what I saw.
The base of the food web is PHYTOPLANKTON, single-celled photosynthesizers. The sample was packed with phytoplankton, including DIATOMS, the type that live in glass boxes of various shapes, patterns, linkages and appendages.
Chain diatoms dominated this sample, especially various kinds of Chaetoceros, which all have long spines that help slow their sinking.
Chaetoceros, and some Asterionella:
(All photos by me. In Lightbox...click to enlarge)
The bad boy below has been common throughout the season. Pseudo-nitzschia is a diatom that produces domoic acid, a potent nerve toxin that kills carnivores further up the food chain like fish and marine mammals. Pseudo-nitzschia has proliferated so much out along the open ocean coast that crab season was cut short (crab accumulates the toxin). The extreme warm water event lingering offshore has promoted blooms all along the Pacific coastline. State testing indicates we did not get any blooms here in the San Juan islands this summer.
Pseudo-nitzschia:
The other major category of phytoplankton is the DINOFLAGELLATES, which have 2 "tails". I'm seeing more dinoflagellates than usual this year, although Heterosigma , another biotoxin-producer, has been scarce. Last year we had several blooms of Heterosigma.
Another dinoflagellate with a lower profile this year is Noctiluca, the one that turns seawater into tomato soup. There were a few individuals, like this one.
Noctiluca:
In June, there were large persistent patches of reddish water in the bay for most of the month. I took samples twice to see what it was, and did not find any one species predominating (a bloom). It's still a mystery. This is what it looked like:
I have a couple of hypotheses. It could be an organism too small to be filtered out by my net. Or it could be a mix of two species that both produce a reddish color. Noctiluca and Pseudo-nitzschia each turn water red, and both were present in those June samples.
Alexandrium is the species that causes Paralytic Shellfish Poisoning when its toxin accumulates in shellfish that consume it by filter-feeding. I saw just a few of these. The San Juan islands are among the few shorelines in Washington where mussels and oysters can still be collected safely right now.
Alexandrium:
Abundant now is Ceratium, a non-toxic dinoflagellate:
Lots of TINTINNIDS, strange clear tube-shaped creatures with a ring of cilia around one end that sucks in phytoplankton. This image has two of them, each containing a food cell: a diatom in the left, a dinoflagellate in the right.
ZOOPLANKTON are abundant right now, both the tiny animals that are planktonic their whole life and creatures only temporarily drifting until they develop into large familiar invertebrates. Zooplankton eat phytoplankton.
The critters that do the heavy lifting in the sea year round, food for a wide range of animals from sponges to fish, are copepods. Here's an adult, with a larval barnacle above it. Copepods are just barely visible to the naked eye.
Copepods go through several molts before becoming adults. Here is an early stage individual:
I collected my plankton sample by a dock. Alongside and under the dock were thousands of small fish darting constantly through the water. These are Shiner Perch. Obviously they were finding plenty of zooplankton to eat!
This fella below makes me a bit nervous. The sample was swarming with them. It's a larval barnacle. Great food source for fish and invertebrates, but they are looking for a place to settle so they grow up into barnacles. Any surface will do. This means we will have to continue taking our boat out at least every 10 days to avoid a barnacle-fouled prop. A spinning prop will knock off young barnacles but once they are well-cemented it takes a chisel. This plankton sample tells me the barnacle season is still in full swing.
Other larvae I saw -
A POLYCHAETE worm larva, either a tubeworm or a free-living type:
(spreading its spines in this pic)
A JELLYFISH larva:
A SNAIL larva:
I also saw clam and crab larvae. Unfortunately I did not see any larval seastars.
We've had unusually warm dry clear weather this summer, with occasional windy days that stir up nutrients. This may explain why the water is still packed with plankton in early September.
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All nature observations welcome in the comments.
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