Green Seaweeds (and Yellow-green Seaweed) Text and photos by Jim Young
Cladophora columbiana Green Tuft Southern Alaska to Baja California Family Cladophoraceae
This spongy, atroturf-looking green alga is composed of profusely branched, uniseriate filaments, entangled into a hemispheric mass that is attached to the substrate by rhizoids. Most of the branching is near the tips of the filaments. The cells of the filaments are large, 200 to 250 micrometers, large enough to be seen without magnification, and hey are multinucleate. Each cell contains a large, reticulated chloroplast (the chloroplast forms a network).
There are at least eight species of Cladophora along the Pacific Coast of North America. This one is common, growing on rocks in the mid to low intertidal zones. There are also fresh water species of Cladophora.
Urospora penicilliformis Hanic’s Green Barrels Homer, Alaska to San Simeon, California Family Ulotrichaceae
During late winter and spring, especially just below the cliff at Maxwell Point near the tunnel, you will see smooth basalt boulders with a green coating on their upper sides. This is the filamentous green alga Urospora penicilliformis. It is a gametophytic, unbranched, uiseriate (a single row of cells) filament up to several inches long that grows in clusters. It has heteromorphic life phases with a difficult-to-see, microscopic sporophyte generation. Its barrel-shaped cells, visible through a microscope, are lined up end-to-end. It is present mostly in the upper intertidal zone. It will tolerate temperatures from 0ºC (32ºF) to 25ºC (77ºF) and may dry out on a sunny day. Its common name comes from Louis Hanic who, while at the University of British Columbia, described its life cycle in his 1965 PhD thesis. (Hanic had previously been a restorer of antique furniture in Czechoslovakia.) In addition to our coast, it is found in many other parts of the world
Barrel-shaped cells of U. penicilliformis
Ulva (Enteromorpha) intestinallis Sea Hair, Gut Weed, Tubular Sea Lettuce Aleutian Islands to Mexico Family Ulvaceae
Ulva intestinalis, often called sea hair or gut weed, is a bright green, tubular and cylindrical seaweed that thrives in environments from freshwater to full seawater (it is euryhaline). It is also quite eurythermal, surviving temperatures from 2ºC (35.6ºF) to 30ºC (86.0ºF). Its thallus is an unbranched, hollow tube that usually grows in clumps. The tube is often filled with gas allowing it to float and sometimes detach from its substrates and drift with the tide. We can find it in the freshwater seeps along Tunnel beach, in tide pools, and in Netarts Bay growing in sand and mud and on sticks and clam shells. The left picture is U. intestinalis at a freshwater wet seep. The right picture shows U. intestinalis in Netarts Bay at low tide.
When I learned about seaweeds in the 1960s, this alga was given the geneus name Enteromorpha (meaning intestine shaped), and that is how I knew it for decades. Now (2018) the name may be changing back to Enteromorpha, To date this is uncertain. Taxonomy in the past has been based on morphology, the way an organism is visibly constructed, and the closer they looked alike, the more closely they were considered to be related. This is true for seaweeds as well as plants and animals. All seaweed guides published before 2003 list Ulva and Enteromorpha as distinct genera. This was because some part of the thallus of Enteromorpha, whether it was the stipe or the blade, was hollow or tubular and the wall of the tube consisted of one layer of cells. Ulva, on the other hand, was never hollow but, traditionally, has consisted of blades with two layers of cells (they are distromatic). DNA analyses are now changing taxonomy from a basis of rather artificial morphological constructs to a more real phylogeny built on genetics. We will see how this develops.
Ulva intestinalis at a freshwater wet seep
Ulva intestinalis floating with air in the tubes
Ulva intestinalis in Netarts Bay at low tide
Ulva lactuca Sea Lettuce Alaska to California Family Ulvaceae
Sea lettuce is a leafy green alga with a blade that is two cells thick. It has isomorphicgametophyte and sporophyte phases (that is, they look the same. You can’t tell them apart just by looking at them). The seasonal, stipelessblade is attached to perennial holdfast. It usually grows attached to rocks or other hard substrates but can sometimes be epiphytic. You will find it mostly in the upper and middle tidal zones, both in sheltered and exposed areas. Although it is very common here and in other parts of the world, its specific name has been in dispute because of its molecular signature when compared to that of the holotype, the original specimen to which the name was originally assigned, may be different.
Mostly Ulva lactuca and Ulva linza at Netarts
Cross section of the blade showing two layers of cells
Ulva linza and Ulva taeniata Enteromorpha and Ulva Alaska to Mexico Family Ulvaceae
Ulva linza is around a foot (30 cm) long and an inch (2.5 cm) or more wide, with a flat blade that is tubular near its base but otherwise flattened and two cell layers thick. Ulva taeniata is similar but has a ruffled blade. Both are common and grow together near Happy Camp in the sandy and cobbled area, often attached to pebbles. They are edible.
Ulva linza
Ulva taeniata
Chaetomorpha linum Sea Hair, Spaghetti Algae Alaska to Mexico, many other parts of the world. Family Cladophoraceae
During summer, this is one of the most prevalent of the green algae in Netarts Bay, much of it free floating in large tangled masses. You can find it washed ashore in windrows along the Netarts/Oceanside beach after being driven out of the bay by the tide. Each unbranched strand of C. linum is a uniseriate chain of cylindrical cells, each cell up to 400 microns in diameter and typically from 0.75 to 1.5 times as long as broad.
These large algal mats may become an important primary producer in Netarts Bay, and they may alter oxygen and nutrient fluxes. During daytime, there is a rapid rate of growth in the upper layers of a mat because of high photosynthetic activity where the alga is exposed to sunlight. Photosynthesis can be so high in direct sunlight that surface waters can become supersaturated with oxygen. However, lower in a mat where the alga is shaded by the upper layers, respiration becomes dominant and, especially in areas of low water movement or where the mat is resting on the sediment surface, conditions can become anoxic. This may be especially true at night. These reducing conditions can affect fluxes of ammonium and phosphate ions.
These floating masses can serve as refuges to young fish and invertebrates, offering protection from predators.
Codium setchellii Smooth Spongy Cushion Sitka Alaska to Punta Baja, Baja California Family Codiaceae
Codium setchellii is an encrusting, dark green alga that forms uneven mats from several inches to many inches across and up to a half inch thick. It looks like a bumpy blob with a rubbery texture. The thallus is composed of a single, elongated and branched cell coiled around itself with no dividing cell walls (the technical term for this type of thallus is “coenocytic”). The elongated branches of the cell, which can be seen using a microscope, are called uticles. It prefers to grow on large rocks in the mid and lower tidal zones with moderate wave exposure, often on the horizontal or slightly sloped rock faces, but also where it may be buried with sand.
This alga is preyed upon by the tiny ascoglossan sea slug Placida dendritica, a relationship investigated in Oregon by Cynthia Trowbridge of Oregon State University. Placida ingests the chloroplasts by sucking them out of the cells, and although it harbors some of the chloroplasts in its cerata (dorsal appendages), these algal organelles do not use photosynthesis to produce food for the sea slug, but they camouflage it so its cerata blend in color and shape with the Codiumutricles. This herbivory appears to be greatest when Codium is stressed, that is when it dries or is heated by the sun at low tide.
Blidingia marginata False Mangrove Enteromorpha Alaska to Mexico Family Kornmanniaceae
Found most often high in intertidal salt marshes, this long, hollow, narrow-strand alga grows from a pad-like holdfast and can form extensive mats that cover the soil and other vegetation. This particular example had colonized patches of the Netarts Bay salt marsh in the Cape Lookout State Park. The thallus is mostly unbranched, and tubular as can be seen by the air bubbles inside the thalli in the accompanying micrograph. The cells are rounded and in longitudinal rows. Chloroplasts have a single central pyrenoid (a shiny body in some plastids).
Another Blidingia, Blidingia subsalsa, which is branched, can be found, often free floating, in the sheltered brackish waters of the Netarts Bay salt marsh.
Blidingia marginata mat
Blidingia marginata
Blidingia subsalsa
Blidingia subsalsa
Vaucheria sp. No common name Pacific coast of North America Family Vaucheriaceae
At low tide across some mud flats in Netarts Bay and in the saltmarsh channels you may encounter a dark green layer that makes a kind of velvet mat on the sediment surface. This is Vaucheria sp., which is not in the Phylum of green algae, the Chlorophyta, but is instead in the Phylum Ochrophyta, the yellow-green algae. It is filamentous, aseptate (meaning a filament is not divided into cells), has lots of chloroplasts, and does not contain starch as do the true green algae. A simple chemical test with with potassium iodide, which colors starch dark blue or black, will not stain Vaucheria but will stain a green alga which contains starch.
