Epiphytic diatoms (Diatomeae) from Piraquara II urban reservoir, Paraná state

We conducted a taxonomical study of epiphytic diatoms on the macrophytes Polygonum hydropiperoides, Ludwigia peruviana and Alternanthera philoxeroides collected in the mesotrophic reservoir Piraquara II flooded in 2009, located in the state of Paraná. A total of 135 infrageneric taxa were identified, among them five at generic level and other five are first records to the state. We provided illustration, valve metrics, meristics limits and taxonomic reference for each taxon. Also, life forms and species frequency are given. The most frequent diatoms totalized 15.3% of total identified taxa and sporadic species represented 54.7%. Achnanthidium minutissimum (Kützing) Czarnecki and Brachysira neoexilis Lange-Bertalot occurred in more than 90% of analyzed samples. Among the very frequent diatoms we found other species included in Achnantidium, Fragilaria and Eunotia. The solitary Discotella stelligera (Cleve & Grunow) Houk & Klee and the short chain Aulacoseira tenella (Nygaard) Simonsen are free living species that entangle among diatoms from the biofilm.


Introduction
Stems of emergent macrophytes are suitable colonizable surfaces to epiphyton communities and are particularly able to transfer a small amount of nutrients to their epiphytes (Cattaneo & Kalff, 1979).As periphytic diatoms are sensitive to eutrophication, it is important to record the species that occured at present for comparision to the future assemblies, helping to understand the relationship between the species and the trophic level of aquatic system.Informations about biodiversity represent a useful tool for ecological and applied studies, but an accurate taxonomy is fundamental.Identification to species level is time consuming and sometimes difficult, but useful and necessary to future ecological studies (Kociolek 2005) in this urban reservoir.Cetto et al. (2004), Silva et al. (2010), Bertolli et al. (2010) and Faria et al. (2010) provided recent diatom inventories from eutrophic and mesotrophic urbans reservoirs: Iraí, Passaúna and Itaqui.Also, Faria et al. (2013) selected tolerant diatom species from Itaqui reservoir.There are no related studies in the recently flooded Piraquara II urban reservoir.Bittencourt & Gobbi (2006) evaluated phosphorous total maximum daily load in the drainage area of Piraquara II reservoir before flooding.The study demonstrated the reservoir present high potencial to eutrophication due to the intense agricultural use of soil and shallow water.The urban reservoirs have been suffering severe anthropogenic nutrients inputs and consequently eutrophication is accelerated (Calisto et al., 2014) and periphyton may respond by changes in abundance and taxonomic composition (Stoermer & Smol 2004).
We conducted a taxonomical study of epiphytic diatoms in Piraquara II reservoir.For each taxon, we provided illustration, valve metrics and meristics limits, occurence, and literature to species taxonomic determination.The taxa first registered to state of Paraná were also described and commented.

Materials and Methods
Piraquara II reservoir (25º30' S and 49º00' W) is located in a preservation area and was built in 2008 by the dam of Piraquara river, inserted in the Iguaçu watershed, Paraná state, south Brazil (Figure 1).This shallow reservoir with 75 days of water retention time is used for public supply (depth 3.7 m, area 5.64 km 2 , drainage area 58 km 2 ), and is mesotrophic most part of the year (Table 1, SANEPAR, 2013, unpublished data) with Trophic State Index (TSI) around 54 from 55 TSI (SANEPAR, 2010(SANEPAR, -2014, unpublished data), unpublished data).The main economic activities in the vicinity are the livestock and corn culture (Bittencourt & Gobbi 2006).
The examined slides and samples were housed at the herbarium of the Universidade Federal do Paraná (UPCB) (Table 2).First recorded taxa to the state of Paraná and those identified to the generic level were described and commented.Diatoms were identified to the lowest taxonomical level according to current taxonomic literature.The references used to identify each taxon even as metrics and meristics limits are listed on Table 3.      L:57.2;W:9.5; AC:4 6c Table 3. Continued...
The diatoms occuring highly frequent were (10 taxa): Achnanthidium caledonicum (Lange-Bertalot) Lange-Bertalot, Achnanthidium macrocephalum          Achnanthidium minutissimum and Brachysira neoexilis were the most frequent taxa present in 90% of the samples.Among the very frequent diatoms we found other species included in Achnantidium, Fragilaria and Eunotia.The solitary Discotella stelligera and the short chain Aulacoseira tenella are free living species that entangled among diatoms from the biofilm.
Description and comments of specimens not identified and first registered to the state of Paraná are bellow.
Sellaphora sp.Fig. 148 Valves linear-lanceolate, ends subcapitate, raphe-sternum narrow and linear, elliptic central area limited by irregular shortening striae; raphe straight with proximal ends curved to the same side, striae radiate.

Table 1 .
Average set of abiotic data in the months of sampling epiphyton *DO: dissolved oxygen; COD: Chemical oxygen demand; TN: Total Nitrogen dissolved; TP: Total phosphorus dissolved; TDS: Total dissolved solids; IQA: Index Water Quality; SD: standard deviation.SANEPAR (2013), unpublished data

Table 2 .
Piraquara II reservoir informations.Collected species of macrophytes, sampling sites and sample register number at Universidade Federal do Paraná Herbarium (UPCB).