Dormant propagule banks of aquatic invertebrates in ponds invaded by exotic pine species in southern Brazil

Abstract

Exotic pine invasion affects native wetland communities in the Southern Hemisphere by changing the hydrological regimen and physicochemical characteristics. Studies evaluating the emergence of aquatic invertebrates from dormant stages are vital to identify the resilience of aquatic communities in ponds invaded by exotic pine species. In the present study, we tested the hypotheses that: (1) pine invasion decreases the richness of drought-resistant aquatic invertebrates in ponds; (2) pine invasion modifies the invertebrate composition in ponds; and (3) these differences in species composition (β diversity) are associated primarily with species turnover. Dry sediment samples were collected from three natural ponds in native grassland and three ponds in a pine invasion matrix in southern Brazil. In all, 7205 invertebrates, primarily represented by cladocerans (18 species), were sampled after rewetting dry sediments. Pine invasion decreased the richness of aquatic invertebrates because the natural ponds had almost 60% more species and a higher number of estimated species than the pine ponds. The composition differed between natural and pine ponds, and this difference in species composition (β diversity) was associated primarily with the replacement of some species by others. The presence of pine appears to alter colonisation and survival rates of aquatic invertebrates that aestivate in dry sediments in southern Brazil wetlands.

Composition of cladoceran dormant stages in intermittent ponds with different hydroperiod lengths

“…Many studies have shown that the necessary conditions for breaking dormancy such as light, nutrients, salinity, predation and competition are species-specific (Brendonck and De Meester 2003;Vandekerkhove et al 2005;Santangelo et al 2011). The experiments of Santangelo et al (2011) and Arau´jo et al (2013) had a short duration (between 10 and 20 days), while in the studies by Á vila et al (2015) and Stenert et al (2016), most cladoceran species (>50%) emerged 30 days after sediment rehydration. According to Golladay et al (1997), the rapid response to rehydration is an important characteristic of aquatic invertebrates living in intermittent wetlands.…”

“…Cladocerans that emerged and developed from propagule banks within each tray were sampled over the experiment with a small square net (5 · 5 cm, 60-lm sieve) 1 day after rehydration, and 7, 14, 21, 32, 39, 46, 53, 60, and 67 days after rehydration (Á vila et al 2015;Stenert et al 2016). Samples were collected by agitating the sediment and then sweeping through the overlying water.…”

Effects of spatial scale and habitat on the diversity of diapausing wetland invertebrates

“…1). We used modified methods by Ávila et al (2015) and Stenert et al (2016). In brief, dry sediment sampled per habitat in each pond was homogenized and distributed into plastic trays, totaling 18 trays (3 samples × 2 habitats × 3 ponds).…”

“…In an experimental room, the trays were flooded with distilled water and stored at constant temperature and photoperiod over 21 d. Aquatic invertebrates were sampled on Days 2, 7, 14 and 21. Three sweeps were performed in each tray and the sampled invertebrates were preserved with 80% ethanol (Ávila et al 2015(Ávila et al , Stenert et al 2016 and identified to species level (cladocerans) and lower taxonomic resolutions (ostracods and copepods) according to Elmoor-Loureiro (1997). The invertebrates were deposited in the Laboratory of Ecology and Conservation of Aquatic Ecosystems of University of Vale do Rio dos Sinos (UNISINOS).…”

Brazil’s Native Vegetation Protection Law Jeopardizes Wetland Conservation: A Comment on Maltchik et al.

“…However, the legal mechanisms provided by the NVPL, even if improved at the state level, are clearly insufficient to promote wetland conservation in Brazil. Overcoming environmental challenges imposed, for example, by climate change (Junk et al 2013), high rates of wetland loss (Creed et al 2017) and the spread of exotic species (e.g., Stenert et al 2016) will require the adoption of effective integrated strategies for the protection, restoration, management, creation, mapping and monitoring of wetlands (e.g., Grasel et al 2018b). We emphatically recommend the creation of a national policy specifically focusing on wetland conservation.…”