Lake Merritt Underwater Observatory

Latest update February 27, 2019 Started on July 4, 2018
sea
urban

Based at the historic Rotary Nature Center in Oakland CA, we intend to explore the underwater habitats and human impacts in an ever changing urban tidal lagoon. High school and community college students will define and document missions.

July 4, 2018
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Preparation

Videos from our Lake Merritt Underwater Observatory dives in the summer and winter were displayed at the Grand Re-Opening of the Rotary Nature Center in Lakeside Park in Oakland CA on February 16th. Because of recent rains, the water clarity of <50 cm (Secchi) and the continuing rainfall made us decid eto postpone putting our new S.E.E. Trident in the water that day. We hope to do so soon.


Many thanks to OpenROV and to Nicole G. in Berkeley for helping us learn how to apply for the S.E.E. and how to operate the Trident. We are planning a new event in the next few weeks. This program will add a new dimension to natural history interpretation at the Nature Center.

A special thank you to Elks Lodge #003 in San Francisco for funds to purchase the accessories needed for operating the new Trident and making it accessible to a group of interested young people.

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In The Field

The most interesting thing about the video here, is perhaps what is not there. The mussels that dominate in this video were punctuated by anemones in my original one from this same location: https://vimeo.com/285059315.
The bed of the lake had much more on it... here it is empty.

The videos were taken from the same launching point near the Sailboat House on Lake Merritt where there is a series of floating and fixed docks.

This difference in the videos points to the seasonality of the slough as a whole: the fluctuations in salinity and oxygen because of the influx of fresh water... and also a unnatural aspect of Lake Merritt -- the time where the flood gates are most often closed, where the tide is not allowed in to refresh the lake.

Nice footage, Adrian! I like your idea about documenting the seasonal changes in the aquatic community at this urban tidal lagoon. Such a contrast with your footage last summer! Thanks!

Several of us met up with Nicole of OpenROV on Sunday Jan 27th 2019 to explore underwater at Lake Merritt. Many thanks to Nicole of OpenROV and Adrian Cotter for bringing out their remotely operated vehicles. Nicole showed us the new Trident ROV which was amazingly fast and maneuverable. Adrian's 2.8 model got beautifully clear views from time to time as it cruised more slowly.
The expedition was quite successful. We saw lots of red seaweed and mussels and some sunken trash with everything kind of blanketed in beige silt. Lake Merritt is a tidal lagoon connected to San Francisco Bay by a short channel. It receives fresh water from urban creeks and stormdrains. The lake was still brackish on Sunday even after all the rain (24ppt top/27 ppt bottom) and dissolved oxygen (7 ppm). Thanks to Tamia, Davonte, Mike, David and several passersby for assisting with the project. More photos of the day at : https://www.flickr.com/photos/ohsesa/albums/72157704809555041

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Preparation

Major thanks to Adrian Cotter for sharing his expertise and his OpenROV with us. The video really shows the potential for ROV's to show the underwater community. I made a "log" for Adrian's video so that we can begin to record species and habitat observations, and easily locate them in the 14 minute tape. I look forward to the next dive. Thanks to everyone who came out. We can use this experience to plan for a grand reunion maybe this fall. Photos from August 12th here:
https://www.flickr.com/photos/ohsesa/albums/72157672246496828

DIVE LOG –August 12th 2018 - Adrian’s OpenROV

TIME Total time is 14 min

0:00 Tube worms (Ficopomatus emigmaticus) and yellow sponge with long tubes (oscules) extended(Halichondria bowerbanki). Beige brushy stuff is bryozoans and mud tubes from polychaete worms.

0:21 Sea anemones with tentacles extended – 2 light strips on barrel identifies as Diadumene lineata. Form with orange strips also seen elsewhere.

1:02 ROV heads under the dock. Mussels and sponges.

1:26-1:31 A crab on a pillar. Shape and position suggest green shore crab (Hemigrapsus oregonensis).

2:30 Close-up of mussels and anemones, brushy bryozoans. A lot of “marine snow.”

3:17 break, then shifts to travel over yellowish-beige seaweed (bleached from red seaweed?). Color pinkish-reddish.

3:44 Open water

4:00 Fish grazing on vertical pole covered with organisms. Small fish laterally flattened. Condensation in camera chamber a problem.

5:35 A clump of green-colored seaweed to left (Codium fragile). Bottom is soft. Red encrusting stuff on Codium (Star tunicate or Botrylloides schlosseri?).

6:17 Ficopomatus reef red stuff = Star tunicate; beige brushy stuff.

9:13 Long stretch of open water with weed-covered bottom.

11:05 Shift to dense mussels encrusted with white/beige stuff on upper surface usually; orange tunicate (Star?)

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Sunday, August 12th, we had a great little expedition. Lake Merritt Observatory's first. Katie Noonan organized the day bringing out her usual array of sampling equipment. Adrian Cotter set up the OpenROV (named RV Grebe, RV for research vessel :-) and after a little bit of worry and a couple of restarts, had it in the water and exploring for the next hour and a half.


Raven, Davonte, and Angela were out to help: having a go at the ROV controls, helping with various sampling efforts, checking out what the ROV dragged up (at one point the tether brought up some seaweed, which we scooped up and poked around to see what might be living there), and Raven filled out our Lake Merritt Observatory whiteboard for the day (see photos).

We had some learnings:

  • an umbrella or some sort of sun blocker would come in handy
  • turn off the HUD when you record!

We still have to take some time to go through the video and catalog all that's on there: anemones, mussels, various little fish, seaweeds, tunicates, a crab hanging from the pylon, and more!

We're looking forward to exploring some different parts of the lake, and figuring out how best to use the ROV.

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Expedition Background

Students who participated in the OpenROV program will collaborate to design an expedition. Stay tuned.

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