Thursday, July 26, 2014
Breakfast was at 4:30am, followed by gearing up for work in the tidal flats. This involves hip boots, a bright orange Pvc rain bib, my matching orange Carhartt rain jacket, and lots of layers. Unfortunately I don’t have the documentation of this fashionable outfit, but imagine a cross between Deadliest Catch and the Stay Puff Marshmallow Man and you’re close.
Jennifer Ruesink is part of a project called the Zostera Experimental Network (ZEN)
, which is a collaboration of scientists around the world studying eelgrass (Zostera marina
). I got to help out with one of their predation intensity experiments this morning, which involves super gluing live amphipods (tiny crustaceans about 6-10 mm long) to fishing line attached to poles and sticking them in an eelgrass bed to then check the next day. The number of creatures missing is a rough indicator of the level of predation, which can be compared to the level of herbivory (tested by, I’m not kidding, gluing organic kale to similar poles). While not always my first choice of an activity at 6:30a on a boat in the drizzly cold, the company was good and I got to pick Jennifer’s brain about feasible locations to sample from and the general ecology of the area. I also had my first taste of walking in tidal flat mud…
That afternoon I had an in depth conversation with Alan about his natural history observations of the bay and how the oceanography, such as river inputs and currents, may affect population structure. He also seems to know everyone who’s anyone that deals with oyster growing and management at the local and state levels. We mapped out a plan of where to put settlement substrates and where to collect adult oysters from so both the north and south parts of the bay are represented.
For the north part of the bay, the native oysters primarily live 30 feet underwater, and therefore can only be collected from trawling. Luckily for me, a trawl had been done that day to collect Pacific oysters to sell, and they were able to set aside a couple dozen native oysters that had also been picked up. These oysters had been cleaned on the outside and separated from each other, so excellent subjects for my first dissections! Up until then, I had never shucked an oyster, nor even seen an Olympia oyster myself, so this first group was slow going. For each oyster, I shucked off the top shell, rinsed the body with special purified water, and then dissected a small section of the adductor muscle to preserve in a buffer called RNALater (which keeps the DNA from degrading). I then noted the length/width of the shell, whether gonads were present, and the gender when I could tell.
For most native oysters, you need to look at the gametes (egg/sperm cells) under a microscope to tell if it is a boy or girl. Olympia oysters are different compared to most oysters in another interesting way. When the water temperature is just right, the males release their millions of sperm into the water for the females to filter out and use to fertilize their eggs. The young larvae are then brooded in the female’s mantle cavity for about 12 days until released into the water. This theoretically gives each larvae a much better chance of surviving the harsh ocean than the Pacific oyster larvae, which are floaters from the second a sperm fertilizes an egg.
Friday, June 27, 2014
This day will forever remain in my memory as the day I almost died 500 meters from dry land…that’s obviously an exaggeration, but at the time it certainly felt that way. My goal was to collect adult Pacific oysters from a site that Jennifer and Alan termed “Parcel A”, look to see if there happened to be any natives hanging around, as well as pick some shell sticks they had set out earlier to look for Olympia oyster spat. Jennifer dropped me off on an oyster hummock with the boat around 7:30am, geared up in my orange Stay Puff outfit with my gloves and little collecting bag. The plan was for me to wait for the tide to go down so I could find the oyster stick, collect about 2 dozen Pacifics, and then walk back to shore and walk the little ways back to their house. I found a comfy spot amongst the razor sharp shells to sit, and then used an incredibly rough method to sample Pacific oysters at random from the surrounding area.
- Large oyster hummocks
Oysters grow best on the shells of other oysters, and so in relatively undisturbed areas like this all of the oysters are in clumps, with the younger ones crowding on the older, larger ones. Some of these ladies were 16 cm long, and surprisingly heavy! An hour of traipsing around didn’t yield any native oysters, so I started back towards shore across what seemed to be a flat expanse of easily traversed damp brown. The second I stepped off the oyster reef, however, I sunk down to my knees. As thick mud is one of those non-Newtonian fluids
where it actually solidifies under a shearing force, I tried to “sprint” forwards and tired quickly. This is where things got bad, like crying and calling for my momma bad. I made the mistake of sitting down and immediately sank so that mud and water went over my chest high rain bib and filled up my boots, making me even heavier. The Neverending Story came to mind more than a few times…
Admitting defeat, I trudged back to the safety of my oyster hummock, and decided the path of least resistance was to walk through the rising water around the rocks, climb over to the pier, and walk back to the house from there. Numerous people working around the docks must’ve seen this entire scene and I can only guess what they were thinking. Upon arriving at the house, Alan greeted me with a spray hose and congratulations- apparently plenty of people they’ve taken out to the tidal flats end up needing some kind of “rescuing”. He also recommended a bucket next time to help me push myself out when I get stuck (advice I have kept to avidly since).
The afternoon involved dissecting and measuring the Pacifics I had collected, and I discovered the joy of opening a “mudder”- a oyster shell that’s actually full of large polychaete worms and the same thick black mud that irked me so earlier that day. I also practiced collecting the tiny 0.5 mm spat off of the shell sticks. How I’m going to extract DNA from each of these tiny oyster babies is a challenge for back in Chicago.