Cladophora sericea

Graceful Green Hair

5 September 2025

Beachcomber Regional Park, Strait of Georgia, Vancouver Island, B.C., Canada.

Tide: 3.5 foot low at 10:44am PDT (measured at Winchelsea Island Tidal Station)

Weather: Mix of sun and cloud, hazy; wind NW 15 km/hour, sea light chop, humidity 75%, 20˚C.

Moon: Waxing Gibbous (95.1%, 14 days); Next phase, Full Moon, 7 September 2025 at 11:08 am PDT; Previous Phase, First Quarter, 30 August 2025, 11:25 pm PDT.

Figure 1: Exposed at a moderately low tide in late summer, the Graceful Green Hair algae – Cladophora sericea, stands out next to the olive green of Fucus distichus. The green shouts out with its vivid tone. Beachcomber Regional Park, Strait of Georgia, Vancouver Island, B.C., Canada. September 5, 2025. Photo ID 27836 ©Seaweedwhisperings.com

Person 1:

Disassociated.

Not there.

Floating in a trance.

Fuzzy, blurred.

Clouded thinking, clouds others’ thinking.

I can’t think of the best words to describe how it gently sets down atop the other marine life as the tide goes out; perhaps “waft” works.

Doesn’t tangle much, but when exposed by the outgoing tide does lightly interlock with its neighbors to form a mat. Light interlock also serves to keep its filaments together when interacting with the sea.

A common name for this seaweed is Graceful Green Hair. Graceful fits with its gentle flowing nature.

Figure 2: At this moderate low tide a mix of marine algae were exposed today on the shoreline along the western edge of Northwest Bay. In the distance and off to the right neighboring Mistaken Island is visible and its shores had similar green ‘skirts’; some of these bright green algae have created sizeable mats of color. Their seasonal growth is advanced at this time of year and they can be striking to observe. Beachcomber Regional Park, Strait of Georgia, Vancouver Island, B.C., Canada. September 5, 2025. Photo ID 27837 ©Seaweedwhisperings.com

Person 2:

On this early autumn day with a hazy sky that was dulled from its true blue color, the greens of several macro marine algae were particularly vivid. There were several species on view; a few Ulva’s and then another thin thread-like species that is in a different genus altogether, namely Cladophora sericea. The common name of this seaweed, Graceful Green Hair, is apt, as to see this seaweed even laid out and exposed at low tide there is a grace to its form. Other species that are similar, like Ulva prolifera, give a more tangled and intermingled impression.

The green of Cladophora sericea was very light and vivid when seen above the waterline. Floating and immersed in pools, however, the green deepens in tone and the whole feel of the seaweed softens and becomes very fuzzy or blurred. Its pattern is indistinct in water, you can see there are some major branches along the thalli, but the rest of the seaweed is a green blur.

Vivid and bright or darker and blurred…, this is an interesting contrast.

The thallus is a collection of small threadlike growths; looking closely in my hand I could see what look like divisions along the thallus. I think these are actually cell divisions. Here and there the thallus branches, but it is so small that following that precisely is not easy. Again, there’s something indistinct or tricky to discern about this seaweed.

Maybe one could be mistaken about who it is? Possibly it likes to be difficult to identify? I chuckled to think that offshore from the point we were exploring the nearest island is actually named Mistaken Island.

The green color can stand out because it is vivid; it also can stand out because it can give the impression of something that is a bit “off” or sickly or lacking nutrients or maybe dying. It is a fine line between vivid neon and washed out yellow green. Maybe this seaweed knows something about that ‘fine line’…?

When I think about the vivid aspect, showing most strongly when it is out of water, I think maybe this is a kind of distress signal or a protest of some kind; or maybe it is a demonstration – a kind of show or display. While this seaweed can grow in the mid intertidal areas, it seems to have a strongly different energy when the tide is high and it is immersed in seawater.

If seen en masse, I think the intertidal regions that host a lot of Cladophora sericea can stand out – it’s like putting a coating of neon green high-vis coloration along the shoreline.

The ‘graceful’ aspect of this seaweed appears most strongly when it is immersed in moving water; there it flows as fuzzy green streamers in accord with the current. In still water, it is quite different. Its many small branches spread out and seem almost to enjoy having a bit of distance from each other. It’s not that they don’t typically get along, but when in a calm pool this seaweed seems to want to reach its branches in many directions. And that reach doesn’t seem overly coordinated – it is more like an expression of pleasure upon being released from the stronger force of moving water. Ah…, maybe they really love to be at ease…, to others this looks like they become diffuse and indistinct but for them it is a feeling of pleasure.

Figure 3: Viewed in the calm water of a tidal pool, Cladophora sericea fluffs out and floats in a highly relaxed manner. Beachcomber Regional Park, Strait of Georgia, Vancouver Island, B.C., Canada. September 5, 2025. Photo ID 27838 ©Seaweedwhisperings.com

Discussion:

In still water this seaweed is diffuse, fuzzy and spread out as much as it can possibly be. It feels like it wants to “flow into” all the space around it. Gently floating and wafting in calm pools is a highly enjoyed state of being for Cladophora. When they are in conditions with active running currents or wave action, we wondered if they could possibly feel bullied by these much stronger forces, as they certainly have no strength to physically resist these forces / influences. Yet we found that emotionally they are inert, truly oblivious to the situation. It simply is what it is. So, no, bullying is not experienced by this seaweed.

The look of this seaweed in still water is ‘cloudy’. Person 1 noted that they can have clouded thinking; in current parlance this is like a person who suffers from brain fog - they are aware of their surroundings but find difficulty in trying to stay focused with their thoughts. This fits the energy of Cladophora sericea very well.

When this seaweed is doing very well, a phenomena called an “algal bloom”, it can actually use most of the available oxygen in the water it occupies. This starves other life forms of oxygen and that could certainly ‘cloud’ their thinking, too! Does the energy of this seaweed give us some clues as to the levels of the functioning of the brain? Possibly so...

This seaweed has been noted for its ability to store nitrogen, yet at times it really doesn’t look quite healthy, as if it in fact might be lacking nutrients. Given that it can be good at storing nitrogen we concluded that the ‘faded look’ of this seaweed must be when it is truly nutrient depleted; those times are when it has lost its vigor and is heading towards death.

Oblivion…, this word came up in our Whispering and it is apt – oblivion is “the state of being unaware or unconscious of what’s happening”. This is how Cladophora sericea happens to consume all available oxygen and smother nearby life forms. It is NOT intentional; they are unconscious of what is happening. We could say that any smothering that occurs is the result of this seaweeds presence when it is thriving; its proximity to others can impact them significantly. It seems that those life forms that cannot move or respond appropriately in some way are the ones who will suffer. It also means that Cladophora is quite used to others reacting to them by moving away or keeping a “healthy distance” from them. They recognize it as what is needed for the other. But if Cladophora is not quite ‘in balance’ we sensed there could be a bit of a protest such as a plea for companionship perhaps? Possibly a bit of remorse? It seems they could feel a bit lonely and hard done by if they are not flourishing.

Potential remorse comes into consideration in another way. The oblivion state that Cladophora can occupy is a blessing, because with it they do not have to contemplate the consequences that their life actions may have on the lives of others. It seems like perhaps they actually don’t have the ability to contemplate these effects, and even if they could they are locked into how they are and are consequently unable to change this in any significant way.

Figure 4: Some filaments in hand give a sense of the size and structure of this seaweed. Beachcomber Regional Park, Strait of Georgia, Vancouver Island, B.C., Canada. September 5, 2025. Photo ID 27839 ©Seaweedwhisperings.com

Biology & Natural History Information:

Description:

Thallus of Cladophora sericea is grass green to light green and is comprised of slightly to profusely branched uniseriate filaments. Often growing in clumps or floating, plants are bushy or spreading; not tufted like other species in the genus such as Cladophora columbiana. Height can reach 5 to 20 cm. Main axes are 50-70 µm diameter and cells are 4 to 8 times longer than wide and contain reticulated chloroplasts. Lateral branches are shorter and thinner. Branching is from the end of cells and branches become narrower at their tips. Attachment to the substrate is by clusters of basal rhizoids or by basal poles at mid to lower cells. This seaweed can form extensive mats in undisturbed areas.

Habitat:

Found on all substrates this seaweed forms mats in the mid to low intertidal when growing in predominantly protected areas; at more exposed sites it can be found floating in quiet pools.

North Pacific Distribution:

Cladophora sericea is widely distributed in the oceans of the world including the Atlantic Ocean, Mediterranean, Caribbean, Indian Ocean, Pacific Ocean and Australia; its type locality is Isle of Sheppey, Kent, England. The North Pacific distribution extends from the Aleutian Islands, all along the coastlines of British Columbia, Washington, Oregon and reaching to San Diego, California; also Korea, and Japan.

Remarks:

The species name is from the Latin adjective, sericeous, meaning silken or silky. Studies from the Pacific Island of Hawaii have noted that this seaweed is found on most Hawaiian reefs; it is a small part of the biomass of the diverse intertidal community there. As an opportunistic settler, it thrives in nutrient rich waters and its prolific growth can deplete oxygen needed by other life including the animal life of the coral reefs themselves. Cladophora sericea has “demonstrated nitrate storage capabilities” which increase its longevity in stressful conditions. In times of large blooms, this alga can passively drift to new areas and be snagged on reefs and rocks sometimes smothering organisms beneath.

Classification:

Empire: Eukaryota

Kingdom: Plantae

Subkingdom: Viridiplantae

Infrakingdom: Chlorophyta Infrakingdom

Phylum: Chlorophyta

Subphylum: Chlorophytina

Class: Ulvophyceae

Order: Cladophorales

Family: Cladophoraceae

Genus: Cladophora

Species: Cladophora sericea (Hudson) Kützing 1843

Former name(s):

Basionym is Conferva sericea Hudson. This species has numerous synonyms, homotypic and especially heterotypic: the interested reader is referred to AlgaeBase.org for a full list.

Figure 5: The annual and often prolific growth of opportunistic green algae is an important part of many balanced coastal ecosystems. Beachcomber Regional Park, Strait of Georgia, Vancouver Island, B.C., Canada. September 5, 2025. Photo ID 27840 ©Seaweedwhisperings.com