When marine plants release reproductive spores, or gametes, the result is that the plant dies. This is the cycle that often occurs with species of Caulerpa in the aquarium when conditions are favorable for reproduction. When Caulerpa begin the process, they often turn yellow with little white spots appearing on the fronds or blades. A white milky substance is then released into the aquarium water. This secretion is composed of the gametes and the cell tissue of the algae. Clear tissue in most species is usually not associated with reproduction, but rather a sign of nutrient deficiency.
What causes reproduction in marine algae?
Marine macro algae reproduce when their environment changes, or when their "biological clock" say it's time. Some of the conditions known to induce a sexual event in nature are: spring tides, lunar phases, temperature and photo period. Some species of algae are even known to release pheromones or organic chemicals to attract male gametes. Several species of marine algae however, are not affected by photo period alone and can reproduce in both light or darkness. In the aquarium the conditions are artificially maintained, so care must be taken to limit any sudden change in water quality that can induce a sexual event. Species of Caulerpa are known to not release reproductive spores if kept under constant illumination. While this may be true, its growth is typically stunted and the algae cease from productively removing nutrients as the process of photosynthesis is slowed. This is known as the 24/7 lighting cycle and is typically employed by aquarists culturing Caulerpa in the refugium.
Controlling growth
Germinated gametes or spores attach themselves to a surface such as rocks or substrate and then begin their growth. Most live rock, imported or aquacultured, are covered in both fertile and unfertile algae spores. This is why, after several weeks or months of favorable conditions in the aquarium, up sprouts a new plant, seemingly out of nowhere. It also explains why undesirable algae such as micro algae and invasive turf algae can quickly appear and take over the live rock and eventually an entire system. The proper cycling of live rock is crucial to remove many of the undesirable algae that may reside upon the surface of the rock.
Control of both micro and macro algae growth is usually accomplished by limiting excess nutrients in the aquarium by using the correct spectrum bulbs and maintaining the temperature of a system. The turbidity of the aquarium environment will also affect growth in marine macro algae. Species that grow in protected habitats will not grow at the same rate or share the same characteristics if introduced to strong currents in the aquarium. This is evident with many species of Caulerpa, especially C. Mexicana. It will remain short and compact in strong current, while growing tall and wide in a sheltered environment. Overall however, marine micro and macro algae are very resilient and will adapt to almost any artificial conditions including current, lighting, temp, salinity and ph. Another limiting factor of growth in marine algae in the aquarium is the competition for nutrients and sunlight between species. When conditions are favorable for rapid growth, eventually one species will try to dominate the landscape and "choke out" other species or colonies. This can be avoided by diligently pruning the aquascape so that no colony intrudes or outgrows its biomass or given space. |
