Babys when the planet is boiling: aquatic animals in Yadoriki Water Source Forest, September 2024

 

Last month in September, it was still hot even in Yadoriki Water Source Forest, ASL 390m+. We forest instructors did a little research in Yadoriki Stream to see what kind of water animals we could find in late September. The high season for water play in the Water Source Forest was supposed to be over by the end of August. But this year it was still boiling hot. Inevitably, Water Source Forest had lots of visitors during weekends to have a chill with Yadoriki Stream. It was still summer. We were delighted to wade in the stream and have a chill. Several families leisurely had picnics in a quiet but gargling sound of the river. Ahhhhhhhhhhhh … summer.

We expected the thing we found in water might not have been different from July or August. Nah. Already a little bit of algae started to establish in the nooks of torrent. They were absent just a couple of weeks ago. The algae will be more by December when all the deciduous trees shed their leaves and started their winter sleep. Confused? Well, while trees have lots of leaves and cover water, the amount of sunlight reaches inside the water is limited. It’s not an algae-friendly environment, mate. Finding algae in Yadoriki Stream would mean fall is approaching, perhaps ... already different from the river during high summer. Then, what our hand nets scooped from the river was definitely different from those a month ago. In September, they were few, and tiny, tiny, tiny. “Hmmmmm. No large larva of Tipulidae or Stoneflies …” “Even Japanese freshwater crabs are pequeños.” The largest specimen we could make on that day was only 2cm or so in body length. Cuties. But in terms of “Gotcha!” feeling … er, you know?

Yadoriki Stream, September 2024

I intentionally scooped the point of algae
as it can cradle the aquatic animals.
But no large ones here …

Tiny crab

In the lab

Lots of tiny heptagenioidea. They are cute!

When we recall a standard lifecycle of water animals, there is no secret for these tiny trophies we could have in September. They mate, lay eggs in water, mum and dad died after that, eggs hatch and larvae spend their child days in water, pupate, and emerge to mate. On average, this cycle takes about 1-2 years, but the time they mate is from spring to early autumn. If the eggs hatch early spring, say March, the babies start to dwell in water from that time, together with those which take more than a year before pupating. i.e. If we do research early spring, or winter, we can catch both big and small aquatic animals. In contrast, from late summer to early autumn, those remaining in water are small babies that come out from the egg recently. Larger aquatic animals in July or August already have become adults and lie eggs by September.

Er … sky was very summer on that day.

OK, OK. What I was surprised was, even in this boiling climate, these creatures follow their traditional lifecycle. Or, maybe they cannot change it easily. Procreation for them is often a one-shot event. It’s not uncommon the bugs to die immediately after a successful egg lying. Unlike humans that can enjoy a long summer for reproduction, they have to do it just once with whatever conditions they are thrown at. I don’t know if the baby water animals are OK with ever-lasting summer. Maybe we should continue collecting data to have some idea what is happening for the baby gadflies under climate change …

Though, fruits of Japanese peppers
already took red autumn red color.

If you find environmental issues in waters of Kanagawa Prefecture, please make a contact with Kanagawa Environmental Research Center 神奈川県環境科学センター

1-3-39 Shinomiya, Hiratsuka City, 254-0014
〒254-0014平塚市四之宮1-3-39
Phone: 0463-24-3311
FAX: 0463-24-3300

k-center@k-erc.pref.kanagawa.jp 

https://www.pref.kanagawa.jp/docs/b4f/index.html