Dictyosphaeria cavernosa
A hollow green bubble seaweed that can smother coral reefs.
Dictyosphaeria cavernosa, a green alga belonging to the class Ulvophyceae and the family Siphonocladaceae, is one of just three species in that family. Its common name is green bubble seaweed. This alga is multicellular, with a surface covered in bumps or bubbles, and is hollow—unlike its lookalike sister species, D. versluysii, which is solid. When young, it has a green-yellow color and can reach about 12 centimeters across.
Found worldwide, especially in Southeast Asia, it typically grows on rocks in shallow reef areas. Around Oahu, it appears in Kaneohe Bay, where sewage discharge played a major role in its expansion. The alga often hides in rock crevices near tidal pools and can initially be mistaken for a green rock. Its spread speeds up when nutrients are abundant, and it has several periods each year of heavy growth.
Between the 1960s and 1970s, increased sewage release into the ocean supplied the nutrients that fueled this alga’s growth. By blanketing coral reefs in a thick layer, it smothers and kills the reef along with other organisms. Scientists have studied the physical, biological, and chemical conditions of the reefs to find ways to curb the alga’s spread. Cutting off its nutrient source led to a decline in growth by 1977.
Quick Facts
- Genus
- Dictyosphaeria
- Species
- cavernosa
Facts from the source article.
Lore & Background
Dictyosphaeria cavernosa is multicellular and hollow, in contrast to its sister species D. versluysii, which is solid and has the same appearance. It grows about 12 cm in diameter and is green-yellow when young. The alga is usually found in crevices of rock formations around rocky tidal pools and may initially resemble a green rock.
It is found all over the world, especially in South-East Asia, and on the island of Oahu it occurs in the Kaneohe Bay area. The sewage system had a huge role in the growth of the algae in Kaneohe Bay. During the 1960-1970's, an increase in sewage discharge provided nutrients that became the primary source for the bubble seaweed to grow, allowing it to spread rapidly.
The algae can spread rapidly due to access to nutrients, and it has a few times out of the year when it grows abundantly. This alga is harmful to coral reefs because it spreads and covers the reef in a thick layer, killing the reef and other organisms.
Reader's Guide
The significance of Dictyosphaeria cavernosa lies in its ecological impact on coral reefs, particularly in Kaneohe Bay, Oahu, where increased sewage discharge during the 1960-1970's supplied nutrients that fueled its rapid growth. The algae spreads by covering reefs in a thick layer, killing the reef and other organisms. Scientists have studied the physical, biological, and chemical aspects of the reefs to find ways to reduce the algae's growth. By 1977, declining the source of nutrients for the algae reduced its growth. This case illustrates how nutrient pollution from human activities can drive the proliferation of a single algal species, with cascading effects on reef ecosystems. The species is also notable for its hollow structure, which distinguishes it from its solid sister species D. versluysii, despite their similar appearance.
Did You Know?
- Dictyosphaeria cavernosa is hollow, while its sister species D. versluysii is solid despite having the same appearance.
- During the 1960-1970's, sewage discharge in Kaneohe Bay provided nutrients that caused the algae to spread rapidly.
- By 1977, reducing the nutrient source led to a decline in the algae's growth.
More in Marine Green Macroalgae, Part 2 1-24
Spotted an error? Know more?
Reader corrections go straight into our review queue. Suggest an edit · How this site is sourced