Temporal and spatial variability of Chironomidae (Diptera) species emergence in a Neotropical estuary

We analyzed temporal (day-to-day) and spatial (site-to-site) variability of chironomid (Diptera) communities from Laguna del Tortuguero, Costa Rica, to refine a collection protocol that can be used in designs of bioassessments of Neotropical estuaries. We made chironomid pupal exuviae collections on 7 consecutive sampling dates at 3 fixed sampling sites during both the wet and dry seasons. We identified 98 species and 44 genera from 2601 specimens. The 4 most abundant genera accounted for 71% of exuviae. Species-accumulation curves reached saturation for both dry- and wet-season samples, and ∼70% of the cumulative species richness was detected after 3 sampling dates across 3 fixed sampling sites. Species diversity appeared to be structured by sampling-site location along a salinity gradient but not sampling date within a season. Based on the Sørensen incidence-based (SI) and abundance-based (SA) similarity indices, cumulative dry- and wet-season samples were highly similar (SI: 0.701, SA: 0.986). Similarity indices did not differ as a function of the number of days or sites between samples in the dry or wet seasons. Daily similarity ranged from low (SI: 0.188, SA: 0.372) in the dry season with 6 d between samples to high (SI: 0.410, SA: 0.750) in the wet season with 1 d between samples. Based on these results, we recommend that chironomid pupal exuviae collections be made over multiple sampling dates and sites from a Neotropical estuary, and these collections can be made during either wet or dry seasons to detect a large proportion of the chironomid community.