Freshwater Copepod (Cyclopoida)

Tiny benthic crustaceans that hunt bacteria, rotifers, and organic particles along the substrate and plant surfaces of the Freshwater Lake, this order-level group expanded after the removal of the Flagfish and is closely associated with the decomposing plant matter and biofilms accumulating on the lake bottom. Order-level identity only; no species-level determination has been made.

Cyclopoida is among the most diverse and abundant orders of copepods in freshwater ecosystems, with thousands of described species worldwide. Unlike the open-water calanoids, cyclopoid copepods are predominantly benthic or semi-benthic: they live near the substrate, on submerged plant surfaces, and in organic sediment, spending more time crawling than swimming. They are visually identified by their single median nauplius eye, which gives one common genus its name, Cyclops, and by the females' two prominent egg sacs carried symmetrically at the abdomen.

Cyclopoids are largely predatory or omnivorous. They feed on bacteria, rotifers, nematodes, protists, small invertebrates, and fine organic particles, making them functionally different from the filter-feeding calanoids. Some species also consume algae and detritus. This more varied diet suits their bottom-dwelling lifestyle where diverse microbial and small invertebrate prey is available.

Cyclopoids are notably tolerant of low oxygen and elevated organic load, reflecting their adaptation to the sediment and detritus layer. Generation times of two to four weeks are typical in warm freshwater systems. Females carry two egg sacs; eggs hatch into nauplii that pass through several larval stages before reaching adult form.

Cyclopoid copepods function as secondary consumers and detritivores in the benthic zone, hunting small invertebrates and processing microbial and fine organic material at the sediment surface and plant leaf layer. In miniBIOTA, the Cyclopoida node is specifically associated with the submerged vegetation and decomposing organic debris in the Freshwater Lake: tapegrass and Creeping Primrose-Willow (Ludwigia repens) surfaces provide both physical habitat and concentrate the microbial prey they feed on.

This positions Cyclopoida at a different trophic interface than the Calanoida node: rather than grazing the water column, they process material from the lake bottom and plant surfaces, channeling benthic microbial production into crustacean biomass available to crayfish, shrimp, and other invertebrates. The Flagfish removal (April 5, 2026) removed predation pressure on both larval and adult cyclopoids, enabling the population to expand visibly.

Introduction context: No specific introduction event is documented. the record notes the species was "introduced as part of a mixed wild-collected microfauna batch to seed the Freshwater Lake." No introduction date is on record. Cyclopoids were likely present in the lake before the April 2026 observations but suppressed by Flagfish predation.