I went to the Boso Peninsula to see Golden Algae (光藻) in two areas, Tateyama and Takeoka, on June 17, '22.
I knew that there was no parking area near caves in Numa so that my husband parked his car at a parking area at Shiroyama Park in Tateyama (城山公園。館山市). After we walked for about 20 minutes through the quiet residential areas and paddy fields, we got to the caves in NUMA Area, Tateyama where Golden Algae is supposed to live. I was curious if I could see the Golden Algae there, because I haven't seen Golden Algae in the cave located at Takeoka, Futtsu (竹岡、富津市) which I visited just before I came to the caves here.
We were lucky!! There I saw Golden Algae spreading over the surface of water in a couple of caves in NUMA Area! Golden Algae is photosynthetic (光合成 の) and carries a strong pigment that gives them a bright color. The colour is a reflection of the surrounding light.
When we were looking into the cave, a man who seemed to live there passed by and told us the horrible days in world War II when they sheltered in these caves.
If it were clear and sunny, we could have seen vividly glowing Golden Algae.
Here are guide posts for the caves in Numa Area.
This is a sea cave at Takeoka, Futtsu (竹岡、富津市) where Bentensama 弁天様 (Goddess of Good Fortune) is dedicated. Not even a bit of Golden Algae were anywhere to be found. I should've come in the early spring because they say that the surface of the water becomes as if a man of generosity had scattered golden powder. Since Golden Algae at Takeoka was discovered for the first time in Japan, it was designated as a National natural monument (国指定天然記念物）in 1928 (Showa 3年).
This is a map of Golden Algae sites that I visted.
This is a map of Numa Area/Tateyama.
It's a 10 minutes bus ride from JR Tateyama Station.
This is a map of Takeoka/Futtsu.
It's a 3 minutes walk from JR Takeoka Station.
I learned that on a sunny day of the right season is a must for veiwing Golden Algae.
I'd love to visit the cave at Takeoka during March and May next year.
If you are interested in viewing Golden Algae, visit Takeoka and Tateyama as well as Mount Nokogiriyama, and Matsudo in Chiba Prefecture.