Algae Observing along Sagami Bay

I had the opportunity to join algae researcher Dr. Akiyoshi Takahashi and other marine specialists in observing, collecting, and identifying algae at a few locations along the Sagami Bay coast of the Miura Peninsula. (Since harvesting seaweed from rocks without permission is illegal, Dr.Takahashi had obtained prior authorization for collecting seaweed for research purposes.)

Normally, just looking at the ocean from land doesn’t reveal what lies beneath the surface, and even when snorkeling in the summer, I rarely take the time to closely observe seaweed. But walking along the rocky shore during low tide with a focus on seaweed, I found myself constantly amazed:

“What is this? I’ve never seen it before!”

“Wow, it’s beautiful!”

“So lovely…”

I was surprised to discover such a wide variety of seaweed species in the sea right before my eyes—but that surprise comes because I am not a specialist.

In contrast, for those researchers who have been observing algae in this area for decades:

“That species of seaweed aren't here this year.”

“There are fewer than before.”

They compared the current state of the ocean with the once-abundant past and expressed disappointment at the decline.

During Japan’s period of rapid economic growth in 1950s to 1970s, Route 134 along the coast was paved, and for the 1964 Tokyo Olympics, land reclamation projects created marinas in both Hayama and Enoshima. Later, the media promoted the region as the stylish resort and the "mecca for surfers", then villas, hotels, and restaurants sprang up along the coast, wide sandy beaches and pine groves disappeared, and even the underwater environment has become increasingly desolate...

Dr. Takahashi’s research shows a correlation between rising sea temperatures and the decline of algae.

During our recent observations, we also found many sea urchins—known for feeding on seaweed—and numerous wakame plants whose soft upper parts had been eaten away.

Although studies have been conducted on the relationship between sea temperature and algae, very little research has explored the effects of land development.

As a result, most conclusions point to:

“The decline of algae is due to rising sea temperatures.”

However, seaweed cultivation specialist Shogo Arai, who has visited the area multiple times, has pointed out:

“I believe another reason is the reduced supply of nutrients and oxygen from land to sea due to land development.”

My volunteer work with Mizu no Wa Tsunagi: chotto (Regenerate ecological connectivity linking land, rivers, and the sea: chotto) aims to help restore the natural connection between land and sea by carrying out maintenance activities on land such as:

• Promoting the infiltration of rainwater into the ground

• Reducing the inflow of dirt into rivers and the sea

• Helping to restore/regenerate the natural flow of water and air from the land to the sea

  
  

Through these efforts, we aim to restore and regenerate the entire watershed’s natural environment, including what lies beneath the ocean surface.

I’m neither a researcher nor a scholar, so I can’t identify species or speak to academic matters, but I am constantly moved by the unique beauty of each seaweed, shell, and fish.

That sense of wonder becomes my motivation:

“I don’t want to see these seaweeds and creatures disappear any further.”

“If possible, I want to help bring back those that have already vanished.”

To those who visit the coast or any beach, I hope you won’t be satisfied just by looking at the surface and take a moment to imagine the world beneath the waves 🐚🐠🦀

This rocky shore is not backed by concrete seawalls, but instead preserved as a protected area where the natural continuity from land to coastal vegetation, rocky shore, and underwater environment is maintained — being here is truly soothing.

Identification work of the collected seaweeds. Dozens of species were confirmed in each area.