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Spending the summer trying to heal a concussion brain injury means that not much science has been happening in my life lately. Now three months post-accident, I'm finally able to do a little bit of thinking and am not quite as exhausted as I was, although extended periods of concentration are still taxing and usually result in what I've come to call the concussion headache. I'm very disappointed to have been on the DL (disabled list) for most of the summer intertidal season, and hope that when the afternoon minus tides return this fall I'll be able to take advantage of them. Fortunately my condition has progressed to the point that I can drive myself out to the wharf to collect a plankton sample and spend a couple of hours looking through microscopes at what I've caught. That's about the limit of what I can do these days; it's not much, but at least it's something.

As we approach the autumn equinox I would expect to see signs that the summer growing season is winding down. Days are noticeably shorter than they were a month ago, and the major upwelling season has passed. In terms of plankton, this should mean a reduction in phytoplankton abundance and diversity, with an overall shift in population makeup away from the strictly photosynthetic diatoms and favoring dinoflagellates, many of which are at least sometimes heterotrophic.

The water at the wharf is remarkably clear right now. Visibility would be fantastic for anyone who wanted to dive under the wharf. September and October tend to be the best months for SCUBA diving in Monterey Bay because the natural cessation of coastal upwelling results in clearer and warmer surface water. I didn't have a Secchi disk or any other way to measure turbidity, but judging by how far below the surface I could see the plankton net as it sank I'd guesstimate that visibility was about 7.5 meters. For people used to diving in the oligotrophic waters of the tropics this level of visibility is downright awful, but for those who dive in productive areas this is not bad.

As expected, when I pulled up the net there wasn't much phytoplankton in the net, and none of the diatom smell I get in spring plankton tows. The net came up pretty clear and rinsed easily into my jar. There was, however, a lot of zooplankton. When I got back to the lab I started looking through small aliquots to see what was there.

The usual suspects were quite plentiful. These included:

  • copepods, in both larval and adult stages
  • polychaete worms
  • veliger larvae, of both gastropod and bivalve types
  • medusae from the hydroid Obelia sp.
  • tintinnids, a type of protozoan that lives in a goblet-shaped glass shell
  • echinopluteus larvae, probably of the sand dollar Dendraster excentricus

Especially beautiful in today's sample were the acantharians:

A living marine acantharian protozoan, collected from the plankton. 25 August 2016 © Allison J. Gong
A living marine acantharian protozoan, collected from the plankton.
25 August 2016
© Allison J. Gong

Acantharians are large single-celled protozoans; I've seen some that are 3 mm in diameter. They build spines of strontium sulfate, which are arranged in precise geometric formations. The protoplasm of the cell extends partway along the spines, which are thought both to deter predation and provide buoyancy. Acantharians are predatory, feeding on smaller unicellular organisms, but also form symbiotic relationships with unicellular algae. The algae are given safe harbor within the cell of the acantharian, and in return provide fixed carbon to the protozoan. Although the players are different, this is pretty much the exact same symbiosis as occurs between reef-building corals and zooxanthellae in the tropics (and also between some of our temperate sea anemones and zooxanthellae).

Here's a puzzle for you. Take a look at this pair of animals:IMG_7178
IMG_7221

 

 

 

 

 

Both consist of a roundish body and a tail. The one on the left is much larger, about 5 mm long, and more opaque. The one on the right is about 2 mm long and is very transparent.

Question: Do you think these animals are the same thing?

Answer: It can often be a mistake to assume any close evolutionary relationship between animals that appear to share a morphological similarity, but in this case shape does result from genetic relatedness. Both of these animals are chordates, my (and your!) closest invertebrate relatives. Yes, we share a closer kinship to these critters than we do to any other invertebrates. We also share with them the following morphological characteristics: pharyngeal gill slits, a dorsal hollow nerve cord, a notochord, and a post-anal tail. Of course, for us the gill slits, notochord, and tail are gone long before we are born, but if you look at pictures of human embryos you can see them. Once we are born the only chordate characteristic remaining to us is the dorsal hollow nerve cord, which runs up through our vertebral column.

The animal on the left is called a tadpole larva, probably of one of the benthic solitary or colonial tunicates. Tadpole larvae are short-lived and lecithotrophic (i.e., non-feeding); the opacity of the body is an indicator of energy reserves stored in body tissues. Tadpole larvae have a short larval life. They typically don't disperse far from the parent, and within a few hours metamorphose into new tunicates.

The animal on the right is a larvacean. It bears a superficial resemblance to the tadpole larva, but is an adult. Larvaceans are entirely planktonic and have one of the most interesting lifestyles imaginable. They live in a house of snot. The house is secreted from an area on the back of the animal, and is inflated as the animal pumps its tail up and down in a rhythmic sinusoidal fashion. The mucus house actually consists of two distinct meshes: the outer mesh is coarse and serves to keep large particles from clogging up the finer feeding mesh. The feeding mesh collects very small particles, which are transported in a mucus thread to the animal's mouth.

Larvacean in its mucus house.
Larvacean in its mucus house.

Larvaceans are prodigious mucus makers. As any filter does, the house eventually clogs up. Instead of trying to backflush and clean out its house, the larvacean wiggles out of it and secretes a new one. They can build up to three houses a day when the water is full of plankton! The discarded houses of countless larvaceans slowly sink from the surface and are a major source of food to animals in the deep sea.

Larvaceans caught in a plankton net are almost always dislodged from their houses. In a dish or a drop of water on a microscope slide, they thrash about in a characteristic larvacean sort of way. Only once have I caught a larvacean and then been able to watch it build a new house in my dish of water. What I saw today is much more typical.

This poor animal was trapped under a cover slip so it can't move freely, but the tail still thrashes about. You can also see its little heart beating like mad.

The tadpole larva, on the other hand, is a much more sedentary creature. It doesn't disperse far so its tail remains still, and its heart rate is much slower than that of its pelagic cousin:

To shift to a completely different taxon there were, as usual, many crustaceans. In addition to the larval and adult copepods, today I saw several examples of Podon, a type of crustacean called a cladoceran. The most familiar cladocerans are the freshwater Daphnia species, but in Monterey Bay we see Podon on a fairly regular basis. Cladocerans reproduce via parthenogenesis, in which unfertilized eggs develop into daughters, and in the springtime most of the Podon I catch are gravid. At this time of year, however, they are not reproducing, at least not parthenogenetically.

Podon sp., a cladoceran. 25 August 2016 © Allison J. Gong
Podon sp., a cladoceran.
25 August 2016
© Allison J. Gong

The most striking feature of Podon is its large compound eye, which causes problems. For many creatures living up in the water column, the only way to hide is to be transparent. This invisibility would be interrupted by any pigment in or on the body. Unfortunately for Podon and other animals that try to hide in plain view, eyes are, at bare minimum, a collection of pigmented cells that detect light. For them, eyes are both a useful sensory structure and a big "Here I am!" signal for predators.

The best thing I saw in today's sample, aside from the acantharians, was a small ciliated blob with little ciliated flaps. This cute little creature is the Müller's larva of a polyclad flatworm. It's hard to appreciate the cuteness of Müller's larva in a 2-dimensional still shot, so here's a video:

Okay, so maybe it's not the cutest larva in the plankton. It was swimming really fast and I had to squash it a bit under a cover slip to slow it down enough that I could keep up with it. But I don't come across them very often, so it's always a pleasure when they show up. You'll have to take my word that they're cute.

Oh, and by the way, I kept the tadpole larva and a couple of other shmoo-like larvae in a dish of seawater to see what they will turn into. Tomorrow I may have new things to look at. I dumped the rest of the plankton into a tank of filter-feeders, where they will resume their place in the food chain.

At the marine lab we have many seawater tanks and tables in various shapes sizes. For my purposes the most useful are the tables. The tables are shallow, about 20 cm deep, but what's nice about them is that water depth can be managed by varying the height of the stand pipe in the drain. I have some critters wandering free within tables and others confined to tanks, colanders, or small screened containers. One of my tables contains the paddle apparatus that stirs jars of babies when I'm raising larvae.

All of these tables are gravity fed from a supply of semi-filtered seawater supply in the ceiling of the building. The seawater flows through some sand filters before being pumped to the top of the building, but is by no means entirely clean. We get all kinds of things recruiting to the surfaces of tables, jars, or anything that sits in a seawater table for more than a few days. Some of the stuff that recruits is a nuisance, such as the spirorbid worms that build tiny calcareous spiral tubes on just about anything and scrape up the knuckles something awful. Other stuff is benign, and more or less ignored until it gets in someone's way. Or until I decide to take a close look at it.

Last year I finally decided to look at some of the red filamentous stuff growing on the bottom and sides of one of the tables. To the naked eye it doesn't look like much, which is why I love having access to a good compound scope. Here's my notebook page from that day:

Observations and sketches of the red alga Antithamnion defectum. date © Allison J. Gong
Observations and sketches of the red alga Antithamnion defectum.
16 June 2015
© Allison J. Gong

Today I took some pictures of the same stuff. It's really pretty and delicate when you see it magnified!

Filaments of A. defectum at 100X magnification. 17 August 2016 © Allison J. Gong
Filaments of A. defectum at 100X magnification.
17 August 2016
© Allison J. Gong
Close-up view of an apical tip of A. defectum at 200X magnification. 17 August 2016 © Allison J. Gong
Close-up view of an apical tip of A. defectum at 200X magnification.
17 August 2016
© Allison J. Gong

I am always gratified when I look back at drawings I made in the past, and find that they still hold true and can be corroborated by photographs. The filamentous reds are so pretty! This is not the best time of year to find sexy algae, and I saw no reproductive structures on any of the filaments I examined. Maybe next spring.

In a different table (the table where the paddle apparatus is, actually) there is some brownish fluffy stuff growing on the bottom surface. I took a look at some of it and noticed right away that the threads didn't have their own inherent structure the way the Antithamnion defectum does. These threads seemed to be sticky, and when I picked up a little piece of the fluff it collapsed into a blob. I had to tease apart the threads in a drop of seawater to make sense of what was going on.

Observations and sketches of benthic diatoms. 17 August 2016 © Allison J. Gong
Observations and sketches of benthic diatoms.
17 August 2016
© Allison J. Gong

These diatoms are really cool! I have no idea which species they are, though. We do have local diatom genera (Thalasionema and Thalassiothrix) in which adjacent cells stick together at their ends to form this kind of wonky chain, but the cells themselves look different. So for now these are unidentified diatoms.

There's no doubt that they are diatoms, though. They have the typical diatom color, a golden-brown that I would name Diatom if I got to name colors, and I could see through the microscope that the cells are enclosed in a silica structure called a frustule.

This is the diatom color:

Chains of benthic diatoms. 17 August 2016 © Allison J. Gong
Chains of benthic diatoms at 100X magnification.
17 August 2016
© Allison J. Gong

At higher magnification the sculpting on the frustule surfaces becomes visible. Unfortunately, at higher magnification you necessarily have less depth of field, so it's more difficult to take photos that show this kind of detail.

Benthic diatoms at 200X magnification. 17 August 2016 © Allison J. Gong
Benthic diatoms at 200X magnification.
17 August 2016
© Allison J. Gong

Some of these cells appear to be doubled. I think one of two things is going here: either the cells simply remain attached to each other by a thin layer of mucilage, or a cell has recently divided and the two cells that are stuck together are the resulting daughter cells. Throughout the growing season diatoms reproduce clonally (each cell divides to produce two genetically identical daughter cells), and their populations can expand very rapidly in response to either natural or artificial nutrient inputs. Because the cells are enclosed by a rigid frustule, however, this clonal replication cannot continue indefinitely. Perhaps diatom reproduction is fodder for another blog post, if people are interested.

But don't those cells look cool?

Mediterranean climates, such as the one that much of California experiences, are characterized by two distinct seasons: a mild, moderately wet season and a warm/hot dry season. In most of the state the majority of precipitation falls between Thanksgiving and Memorial Day, with very little in the other months. At this time of year the dry season is in full swing. I've heard of a few reasons why California is called the Golden State: (1) the Gold Rush that began in 1848; (2) the carpets of California poppies that blanket the state in the spring; and (3) the drying up of the summer grasses, which covers much of the state in a golden mantle dotted with oak trees.

We are definitely in the golden season now. We had a good, colorful spring with a banner crop of wildflowers, thanks to the El Niño rains, and it was green well into July. Given the drought, we hadn't seen that much green in years. But now the annual vegetation has dried out and most of the state is on high alert for wildfire. Fire is a seasonal event in the arid west, and every year several thousand acres burn in California. July and August are the worst months.

This year the most devastating fire in my region of the state is the so-called Soberanes fire burning near Big Sur. As of today the fire has blazed for 23 days, scorched over 71,000 acres, and is 60% contained. Almost 60 homes have been lost and over 400 other structures are threatened, all because some idiot lit an illegal campfire. Up here in Santa Cruz we are over 60 miles away from the fire, but the entire region has been affected by the smoke. Until recently the typical summer onshore winds have blown most of the smoke eastward and while we've smelled smoke here we have been spared the worst of it. This satellite photo was taken two days after the fire started:

Soberanes fire, image captured by satellite. 24 July 2016 © Jeff Schmaltz, NASA
Soberanes fire, image captured by satellite.
24 July 2016
© Jeff Schmaltz, NASA

This morning when I woke up the smell of smoke seemed stronger. It was foggy, enough so that water had condensed on the ground and cars, but instead of smelling like ocean the fog smelled like fire. The sun came out for about an hour in the mid-afternoon, showing a sky that wasn't as blue as it is when ordinary fog recedes. Air quality is pretty bad so I've been staying indoors with windows and doors closed.


Last week I was in the Lake Tahoe region, on a short vacation with my family in South Lake Tahoe. On our first day there we went on a short hike in the Angora Lakes area. Let me tell you, being at altitude makes a concussion headache worse--I had been weaning myself off the ibuprofen, but had to go back on the full doses for the handful of days we were at altitude.

On 27 June 2007 an illegal campfire ignited a wildfire that eventually burned 3100 acres and destroyed more than 300 homes and commercial structures in a populated area near South Lake Tahoe. The Angora fire was fully contained on 2 July and 100% controlled on 10 July.

Map of the Angora fire. 28 June 2007 © Phillip Wooley
Map of the Angora fire.
28 June 2007
© Phillip Wooley

On the hike out to Angora Lakes you see a few burnt trees off the trail, but don't really get a feel for the scope of the area affected by the fire. So on our way out of the Tahoe basin we drove through one of the neighborhoods that had burnt. Almost 10 years after the fire now, all of the burnt homes have been either rebuilt or completely torn down. It was interesting to see that the fire's damage had been spotty: in a neighborhood of mostly older houses there would be a couple scattered here and there that were obviously new construction, likely post-fire rebuilds.

In the years since the fire there has been a lot of restoration work in the Angora region:

Post-fire restoration work at Angora 8 August 2016 © Allison J. Gong
Post-fire restoration work at Angora
8 August 2016
© Allison J. Gong

It is quite easy to see exactly what the fire did and did not burn.

8 August 2016 © Allison J. Gong
8 August 2016
© Allison J. Gong
8 August 2016 © Allison J. Gong
8 August 2016
© Allison J. Gong
8 August 2016 © Allison J. Gong
8 August 2016
© Allison J. Gong

But even a burnt tree possesses a stark beauty that living trees do not have:

8 August 2016 © Allison J. Gong
8 August 2016
© Allison J. Gong

Fire is, or used to be, a significant part of the ecology of much of the western United States. Some plants' seeds require the heat of fire to germinate, and fire opens up the canopy to allow low-growing plants access to sunlight. When a fire burns through a wilderness region the clock is reset on ecological succession, allowing different species of plants to take their turn thriving in the habitat. We humans experience ecology as a snapshot in time, the duration of our own lifetimes. In the aftermath of a wildfire we have the opportunity to observe the early stages of succession that will likely result, decades down the road, in a mature forest. Even now, only nine years after the fire, it is clear that plants, especially grasses, have been thriving in areas that had been burnt down to charred soil. It will be interesting to watch how succession proceeds over the next several years.

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