Moina

Moina are tiny freshwater water fleas established in the Freshwater Lake since May 2026, where hundreds persist in the system but concentrate in sheltered Lakeshore vegetation rather than expanding freely through open water. They are negatively phototactic: most visible on the lake glass each morning when lights turn on, then retreating during daylight and becoming more active again at night. A separate, smaller Daphniid species was identified alongside them in May 2026; the two are now confidently distinguished.

Moina is a genus of small freshwater cladocerans found in ponds, temporary pools, rice paddies, and warm, nutrient-rich water bodies worldwide. They are closely related to Daphnia but are generally smaller, more rounded, and substantially more tolerant of adverse conditions including low dissolved oxygen, warm temperatures, and high organic loading. Adults are typically 0.3 to 1.5 millimeters in size, making them visible to the naked eye as specks but not readily distinguishable from other small zooplankton without close observation.

Moina are filter feeders that process suspended algae, phytoplankton, microbes, and fine organic particles from the water column using modified appendages as filtering combs. They are negatively phototactic: under bright light they tend to sink or retreat toward shelter, while they become more active at the water surface and on glass surfaces in low light and at night. In sheltered freshwater habitats, they often aggregate among dense aquatic vegetation where predation pressure is lower.

Moina reproduce rapidly by parthenogenesis under good conditions, with females producing broods of genetically identical clones every one to two days. A single individual can found a reproducing population. Under environmental stress (overcrowding, temperature extremes, food shortage, drying), they shift to sexual reproduction and produce resting eggs called ephippia that can survive desiccation and harsh conditions until conditions improve. Lifespan is typically ten to twenty days. This combination of fast asexual reproduction and resilient resting eggs makes Moina one of the most productive and persistent zooplankton in warm freshwater systems.

In the Freshwater Lake, Moina filter suspended algae and fine organic particles from the water column, removing material that would otherwise contribute to turbidity or accumulate as surface films. At hundreds of individuals, their collective grazing adds measurable plankton-grazing pressure to the system, though the link between Moina density and water clarity in miniBIOTA has not been measured directly.

Moina are also a potential prey resource for larger invertebrates in the Freshwater Lake. Ghost Shrimp zoea and adults, young Slough Crayfish, and other macro-invertebrate predators could consume Moina as part of their diet. The observation that Moina concentrate in sheltered Lakeshore vegetation rather than open water is consistent with predation pressure or light avoidance keeping the population constrained, even though food is abundant in the open water column.

In miniBIOTA, the Moina population occupies a niche shared with the Unidentified Tiny Daphniid and Daphnia sp. in the freshwater zooplankton layer. Their persistence since May 2026 at stable hundreds without major expansion suggests the system is not providing conditions for unconstrained population growth.

Moina were introduced from a wild-collected trail-pool sample on May 1, 2026, as part of an effort to establish freshwater zooplankton in the Freshwater Lake.

May 1, 2026: Moina were introduced from a wild-collected Florida trail-pool sample. The same day, very small individuals were observed in the water column, described as "a new wave of very small Moina," possibly representing recently hatched individuals from the sample population. This interpretation is uncertain; the small individuals may have simply been the smaller members of the introduced cohort rather than in-system hatchlings. Video evidence shows numerous small Moina visible in the water column. The observation noted that the previous weeks had seen low Moina visibility, raising uncertainty about establishment, and that this new cohort suggested the possibility of building a sustainable population.

May 21, 2026: After weeks of observation, Josue reported being able to confidently distinguish the Moina population from a newly observed, smaller Daphnia-like species. The Moina population was described as stable and established but not expanding as expected. Hundreds are present in the Freshwater Lake, with noticeably higher concentrations in sheltered Lakeshore vegetation among dense plants. On the glass in the morning after lights turn on, approximately a dozen individuals are commonly visible. They tend to remain hidden during the day and become much more active at night. The note described some ecological factor as appearing to limit abundance despite continued persistence. No media.

June 17, 2026: During a general condition assessment of the Freshwater Lake, Moina were confirmed present. The population was described as modest and stable, not rapidly increasing. The owner concluded that Moina (and copepods) have not expanded to the density needed to reduce the visible algae load. No snails were observed congregating at the water surface, which was interpreted as a negative indicator for acute dissolved oxygen stress. No media. Assessment triggered consideration of introducing a nutrient-removing plant to address the persistent green water condition through a different mechanism.

June 25, 2026: Moina confirmed in dense Lakeshore vegetation, consistent with the shelter-preference pattern observed since May 21, 2026. Observation paired with confirmation of Daphnia in the lower open water column; the two populations are co-present and occupying distinct microhabitats. Suspended green algae remains abundant. The owner proposes that elevated water temperature is limiting the ability of both Moina and Daphnia to keep pace with algae growth. Video documented for the paired observation. Observation record, June 25, 2026.