Every year, as early as Memorial Day or as late as Father's Day, there's about a week of really lovely low tides. This midsummer tide series usually includes the lowest low tides of the year, and we intertidal ecologists plan our field activities around them. Incidentally, there's a corresponding low tide series in the midwinter, too. However, at that time of year the lows are in the afternoon, and because the low occurs about 50 minutes later each day you're fighting darkness as you work the series. But in the summer, even if the first day of the tide series has a low tide before sunrise, that 50-minutes-later-each-day thing is really nice and you never have to worry about running out of daylight.
This year, the California Academy of Sciences sponsored several citizen science excursions called Bioblitzes to various locations on the California coast. The goal of these Bioblitzes was to document biodiversity in the intertidal in protected and non-protected areas of the coastline. Back in May I volunteered to lead a Bioblitz at one of the sites close to me, and planned to participate in a few others as well. In addition to actual organized Bioblitzes, citizens were invited to submit their own independent observations to the project.
Today is the three-week anniversary of the car accident that left me bruised and concussed. The bruises are pretty much healed at this point, and the soreness in my ribcage is also much improved. The medical advice I got for dealing with the concussion was, "Protect your brain from stimulation. Let it heal. And REST." So for the past three weeks I haven't been doing much of anything. I was worried that I wouldn't be able to go out on any of the midsummer low tides, as it didn't take much to overtax my injured brain and I didn't want to risk overextending myself. I did end up skipping the first Bioblitz of the week and modified my original plans for the rest of the tide series to play it safe and stay closer to home.
I'm still trying not to spend too much time on the computer (electronic screens are very bad for injured brains) so I'm going to summarize my week's activities in a single post. I'll keep the stories short. But I did want to share some of the things I saw.
Day 1 - Natural Bridges, Monday 6 June 2016, low tide -1.6 ft at 06:25
My first venture out by myself was to Natural Bridges. It's very close to my house and I figured that if I needed to bail I could walk out and be home within 15 minutes. It was cold and foggy and I felt energized just to be out there again.
Turns out this trip was about all my brain could cope with that early in the week. I skipped a Bioblitz up at Pigeon Point on Tuesday so I could stay home and rest, which ended up being a good call. A whole day of doing nothing was exactly what my concussed brain needed.
Day 2 - Mitchell's Cove, Wednesday 8 June 2016, low tide -1.1 ft at 08:02
The day of rest was enough to get me back out there on Wednesday. My friend Brenna met me at Mitchell's Cove for a morning of tidepooling. Mitchell's Cove is a popular, dog-friendly beach in Santa Cruz, particularly busy in the mornings and evenings. Last September it was visited by a juvenile humpback whale, which came right into the Cove and hung out there for several days. I didn't see any whales this week, but there was a surprising diversity of life in a relatively small area of rocky intertidal.
We have two species of surfgrass in northern California. At this time of year they are very lush and conspicuously green.
Phyllospadix scouleri, the species that has flatter, more ribbon-like leaves, was blooming. Its congener, P. torreyi, growing in almost exactly the same place, has narrow leaves that are more cylindrical in cross-section, and was not in bloom. Phyllospadix is a true marine plant; the flowers are inconspicuous swellings near the bottom of the leaves and the pollen is carried by water, rather than wind, to nearby plants.
And I saw two species of hydroids! This one is easy to ID to the genus Aglaophenia, but I would need to examine it under a microscope to determine the species. I wasn't collecting anything on Wednesday so I don't know which species it is.
This second hydroid is, I think, a species of Abietinaria. The hydroid colony is the pale orange stuff; the pink stuff is coralline alga.
And I saw an octopus! We know that they're in the intertidal, but they are so cryptic and clever at hiding that we don't see them very frequently. This one was definitely smarter than I was. Instead of scooping it out and placing it on dry ground so I could photograph it more easily, I chased it around a tidepool with my camera. Thus, this is the best picture I could get:
Okay, you'll just have to take my word for it.
Day 3 - Davenport Landing, Thursday 9 June 2016, low tide -0.7 ft at 08:52
This was the day of my "official" Bioblitz. I had four participants--Brenna, Alice, Martha, and Andy. As of right now (Brenna hasn't yet uploaded her observations) the other four of us have made 120 observations, documenting 50 species. Here are some of mine:
There are kelps, such as Egregia menziesii (feather boa kelp) whose habitat is the rocky intertidal. Most kelps, though, live subtidally, often in kelp forests. Nereocystis luetkeana, the bullwhip kelp, is one of the subtidal canopy-forming kelps. This one recruited to the intertidal. It is quite small and extremely cute; the float is only 2 cm in diameter.
Algae look their best when immersed. Out of the water they usually collapse into stringy or gooey masses, making it difficult to appreciate their structural beauty. This piece of Microcladia borealis was submerged in a tidepool, and fortunately there was enough light that I could take this picture.
Day 4 - Natural Bridges, Friday 10 June 2016, low tide -0.2 ft at 09:42
Yesterday I returned with a former student, Daniel, to Natural Bridges. It was sunny and warm, completely different from how it had been on Monday. There were many boaters out on the bay, taking advantage of the glassy flat sea.
I've seen a lot of shore crabs running around on the rocks this year. On cool, damp days they just scurry about, but on warm sunny days they often sit still and literally foam at the mouth. The bubbles they produce keep their gills moist so they can still breathe even while emersed. This biggish shore crab was working up quite a froth.
Hermit crabs don't usually end up out of the water. This one was immersed in a tidepool, wearing the shell of the snail Olivella biplicata.
Nuttallina californica is one of the most common chitons seen around here. They often hunker down into small crevices where water will collect even at low tide. This individual was nestled among a clump of Phragmatopoma tubes; being closely surrounded by other animals will help keep its own body moist.
Unlike the hard granite that you'd find at the southern end of Monterey Bay, the rock at Natural Bridges is a soft, easily eroded mudstone. You can scratch it with your fingernail. Limpets take advantage of this soft rock by digging themselves little home scars, which conform perfectly to the contours of their shells and make a snug, water-tight fit. The limpet leaves its home scar to forage when the tide is in and returns to it as the tide recedes. The owner/occupant of this scar has likely died, as it wouldn't have abandoned its home scar when we were there at low tide.
And speaking of limpets, Daniel and I spent a lot of time observing the owl limpet, Lottia gigantea. This limpet is noteworthy not only for its large size, but for its territorial behaviors. They are indeed large--the biggest ones I've ever seen are about the size of the palm of my hand--and the big ones are all females. Lottia gigantea is a protandrous hermaphrodite: individuals begin sexual maturity first as males, and then the lucky few turn into females.
The truly remarkable thing about L. gigantea is its ability to modify the environment. The large females maintain an area called a farm, from which they diligently remove interlopers. They will scrape off settling larvae of barnacles and mussels, and will push off other limpets. Lottia farms are very common at Natural Bridges; if you are here and see a suspiciously empty patch of rock amid the mussel bed, look for a big limpet hanging out on the edge of the empty spot.
The owl limpet has a good reason for keeping other animals off her territory. It provides her food. This animal is indeed a farmer. See the pale zig-zag markings in the Lottia farm? Those are marks made by the limpet's radula as she grazes over the rock. All limpets are grazers, but L. gigantea actively manages her farm so that she feeds on one area while allowing the algal film to grow on other areas, then rotates to a new feeding spot as the old one becomes depleted. Pretty clever for a snail, isn't it?
It felt really good to spend some quality time with Mother Nature again. I'm still taking it very easy, careful not to get overtired and to continue letting my brain heal. Getting outside for even short periods definitely seems to help.